THE DISTRIBUTION OF FLUORIDE IN SOUTH AFRICAN HEALTH MASTER OF SCIENCE

THE DISTRIBUTION OF FLUORIDE IN SOUTH AFRICAN HEALTH MASTER OF SCIENCE

THE DISTRIBUTION OF FLUORIDE IN SOUTH AFRICAN

GROUNDWATER AND THE IMPACT THEREOF ON DENTAL

HEALTH

A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE

REQUIREMENTS FOR THE DEGREE OF

MASTER OF SCIENCE

WATER UTILISATION

FACUL TY OF ENGINEERING, BUILT ENVIRONMENT AND

INFORMA TION TECHNOLOGY

UNIVERSITY OF PRETORIA, PRETORIA

© U n i i v e r r s s i i t t y o f f P r r e t t o r r i i a

"So Moses brought Israel from the Red Sea and they went out into the wilderness of

Shur, and they went three days in the wilderness and found no water. And when they came to Marah, they could not drink of the waters of Marah, for they were bitter: therefore the name of it was called Marah. And the people murmured against Moses, saying, "What shall we drink? And he cried unto the Lord, and the Lord showed him a tree, which when he had cast into the waters, the waters were made sweet"

This dissertation is dedicated to all those who have fought to liberate the oppressed, who have managed to eliminate the barriers that limit the normal social associations of all human kind and who have realized the need of encouraging women to participate in collaborative research and a recognition of their cognitive skills and payment of the human debt

The most appropriate and widely used source of drinking water for the rural populations of South Africa is groundwater. Pilot studies and surveys conducted by the Department of Water Affairs and Forestry (DWAF) indicated that there are a number of boreholes across the country that contain apart from fluoride, levels of nitrate, some heavy metals, total dissolved solids, sulphates and faecal coliform (in isolated regions) that could pose a health risk if the water is used for drinking purposes. Very few boreholes have been tested for heavy metals or toxic organic substances. However considering the levels of fluoride, in general, grOlmdwater is of acceptable quality except for some provinces in which elevated levels of natural groundwater fluoride occurs. Very high levels of fluoride, >4 mgIl occur in some groundwater sources in all nine provinces of South Africa, especially in the Limpopo,

North-West, Eastern Cape, Northern Cape, Western Cape and KwaZulu Natal provinces. A superficial inspection reveals that most of the local people in those areas suffer from dental fluorosis at varying degrees. The main aim of this study is to determine the distribution of the fluoride ion concentration levels in South African groundwater and the impacts thereof on dental health. The available data is used to assess the distribution of the various fluoride ion concentration levels in some national groundwater sources. Areas of particularly high or low fluoride levels are identified.

Results from an epidemiological survey carried out by the National Department of

Health (NDOH) are used concurrently with the fluoride data to determine the percentage morbidity of dental fluorosis in each area The results are compared in order to determine if any relationship exists between the occurrence of fluoride in drinking water and the incidences of dental fluorosis. Vegter's lithostratigraphy and the simplified geology of South Africa are used to interpret the results and assess the role of surface geology in the release and distribution of fluorides in groundwater. The role of other factors such as climate and the interactions of the fluoride ion and other water quality parameters in aqueous media are also assessed.

Keywords: groundwater, fluorides, dental fluorosis, geochemistry, morbidity of dental fluorosis, climate, water quality.

The following are acknowledged for their assistance during the compiling of this dissertation

• My supervisor Professor C. F Schutte for the continuous guidance, mento ring, corrections and encouragement,

• The various officials of the Institute for Water Quality Studies and Geo hydrology

Directorate of the Department of Water Affairs and Forestry who assisted with data extraction;

• Bets Davies and Magda Smidt for checking the quality of the data at all times

• Dr. Kroon for authorizing the access to the Dental fluorosis data

• Prof VanWyk and his team at the Department of Health for providing the Dental fluorosis data

• The South African Weather Bureau for the Temperature data

Special acknowledgements go to my supervisor who tirelessly provided his support and Mr. Mike Silberbauer, a senior specialist at the Institute for Water Quality Studies who offered his unconditional services, GIS expertise and was committed, approachable at all times when maps and diagrams were needed.

ABSTRACT

ACKNOWLEDGEMENTS

TABLE OF CONTENTS

LIST OF FIGURES

LIST OF MAPS

LIST OF TABLES

LIST OF APPENDICES

SYMBOLS AND ACRONYMS

CHAPTER 1: INTRODUCTION

1.1

BackgrOlmd

1.2

Motivation and purpose of study

1.2.1

Some concerns about the fluoridation of South African public water supplies.

1.3

Aims and Objectives

1.4

The Structure of the Dissertation

CHAPTER 2: TIlE CHEMISTRY AND OCCURRENCE OF FLUORIDES

IN TIlE ENVIRONMENT

2.1

Introduction

2.2

The Chemistry of fluoride

2.2.1

In Natural waters

2.2.2

Mineral-aqueous fluoride interactions.

2.2.3

In Soil

2.3

Occurrence of fluorides

2.3.1

General

2.3.2

Occurrence of fluorides in South Africa

2.3.2.1

In Rocks

2.3.2.2

In Minerals

(i)

(ii)

(iii)

(vii)

(viii)

(ix)

(xi)

(xii)

2.3.2.3

2.3.2.4

2.3.2.4.1

2.3.2.5

2.3.2.6

2.3.2.7

2.4

In Soils

In Water

In South Africa

In the Biosphere

Fluorides in the atmosphere

In food

Factors that contributeto the occurrence of high fluoride in groundwater

CHAPTER3:

3.1

Introduction

HEALTHEFFECTSOF FLUORIDES

3.2

Fluoride Metabolism

3.2.1

3.2.2

3.2.3

Absorption

Distribution

Excretion

3.3

Beneficial uses offluoride

3.4

Effects of fluorides on Human Health

3.4.1

General

3.4.2

The significance oflow fluoride ion concentration in drinking water supplies

3.4.2.1

Dental caries

3.4.2.2

3.4.2.3

Remediation

Fluoridation

3.4.3

The significance of high fluoride ion concentrations in drinking water supplies

3.4.3.1

3.4.3.2

Dental fluorosis

Skeletal fluorosis

3.4.3.3

3.4.3.4

Other effects

De-fluoridationtechniques

3.5

Drinking Water Guidelines and Standards for fluoride

3.6

Optimum fluoride levels

29

29

30

30

35

35

36

30

31

34

41

26

26

26

27

27

27

28

28

CHAPTER 4: RESEARCHPROCEDURES

4.1

INTRODUCTION

4.1.1

Water Management System

42

42

4.1.2

The National GrOlmdwater Quality Monitoring Project

4.2

The determination of the fluoride ion concentration distribution in

4.3.1

Introduction

4.4

The determination oftrends in changes of fluoride ion concentrations in

43 groundwater 44

4.3

The determination of the current status of fluoride levels in groundwater 45

45 groundwater

4.5

Dental examinations

4.6

Computer manipulation of spatial data

4.7

The analytical method used for fluoride analysis

46

47

48

49

5.1

Introduction 50

5.2

Occurrence and distribution of the fluoride ion concentrations in groundwater, 1985-2000

5.2.1

Spatial distribution of the fluoride ion concentrations in groundwater

5.2.2

The highest fluoride ion concentrations recorded in South Africa between

50

50

53 1985-2000

5.3

The status of fluoride levels in groundwater as reflected by existing groundwater sources studied between 1996-2000

5.3.1

Spatial distribution

54

54

5.3.2

Frequency analysis.

5.4

The occurrence of dental fluorosis in selected provinces

5.4.1

Morbidity of dental fluorosis and drinking water quality

5.4.1.1 North-West

55

58

61

62

5.4.1.2 Western Cape

5.4.1.3 KwaZulu Natal

5.4.2

Distribution of potential risk areas

5.4.3

Risk levels and optimum fluoride concentrations in drinking water

64

65

65

67

(v)

5.5

Factors that effect the distributionof fluoride in groundwater

5.5.1

Introduction

5.5.2

The role of Climate

5.5.3

Interactionsof the fluoride ion with other water qualityparameters

5.5.3.1 Introduction

5.5.3.2 CorrelationofF- with Hardness

5.5.3.3 Correlationwith Na+

5.5.3.4 Correlationbetween pH and P-

5.5.3.5 Correlationbetween fluoride ion and phosphate

5.5.3.6 Correlationbetween the fluoride ion and total alkalinity

5.5.4

The role of surface geology

69

69

69

72

72

74

75

76

76

77

77

Fig

1:

Fig 2:

Fig 3:

Fig 4:

E h pH equilibrium diagram for the system F1-I

2

0 at 25°C and for total fluoride concentrations <2000mg/.e

Dental fluorosis manifestations.

Locations of current groundwater quality monitoring points.

The distribution of fluoride ion concentrations for the groundwater sources, 1996 - 2000.

MapA

MapA1

Fluoride in groundwater 1985 - 2000 fluoride in groundwater 1985 - 2000 for Fconc > 4,0:::;;8,0

rng/f.

MapA3 Fluoride in groundwater 1985 - 2000 for Fconc > 8,0

rng/f.

MapA4

MapB

MapB1

MapC

MapC1

MapC2

MapC3

Fluoride in groundwater 1985 - 2001 for Fconc:::;;0,5

rng/f

Fluoride in groundwater, 1996 - 2000

Fluoride in groundwater: point and area data

Dental fluorosis morbidity

Dental fluorosis morbidiy (North-West province)

Dental fluorosis morbidity (Western Cape province)

Dental fluorosis morbidity (KwaZulu Natal province)

Table 1:

Table 2:

Table 3:

Table 4:

Table 5:

Table 6:

Table 7:

Table 8:

Table 9:

Table

10:

Table 11:

Table 13:

Table 14:

Table 15:

Table 16:

Table 17:

Table 18:

Table 19:

Table 20:

Table 21:

Solubility products for some minerals

Solubility of fluorite, CaF

2 in the water containing NaHC0

3

Total fluoride concentrations recorded in some rocks in South Africa

Occurrence and chemical composition of some minerals found in South

Africa

F content recorded for some boreholes in South Africa

A summary of dietary sources of fluoride as summarized by Heilman,

etal,I997

Dental fluorosis categorization

Phases of skeletal fluorosis

Drinking water quality standards and guidelines for fluoride in South

Africa, effect of fluoride on aesthetics and human health

Fluoride guidelines

Recommended health quality guidelines for drinking water for elements and ions in the Republic of South Africa.

Chemical requirements macro determinants for drinking water:

Standards for drinking water.

Description and rating of dental fluorosis, Dean, 1939

Highest fluoride ion concentrations recorded for the State and

Individual Primary Drainage Regions as reflected by the WMS data,

1985 - 2000.

Criteria used for the interpretation of Dental fluorosis results.

Dental fluorosis by level of severity in the Free State Province

Dental fluorosis by level of severity in the WC Province.

Dental fluorosis by level of severity in the NW Province.

Dental fluorosis by level of severity in the KZN Province.

Dependency of communities on groundwater for domestic purposes.

Incidences of fluoride ion concentrations in groundwater sources of the

North-West province and the percentage morbidity of dental fluorosis.

Table 27:

Table 28:

Table 29:

Table 30:

Table 31:

Incidences of fluoride ion concentrations in groundwater sources of the

Western Cape province and the percentage morbidity of dental fluorosis.

Incidences of fluoride ion concentrations in groundwater sources of

KwaZulu Natal Province and the percentage morbidity of dental fluorosis.

Relationship between % dental fluorosis morbidity and drinking water fluoride levels in KwaZulu Natal province.

Relationship between % dental fluorosis morbidity and drinking water fluoride levels in the North -West Province.

Maximum fluoride ion concentration limits recommended for drinking water by various bodies.

Effect of climate on fluoride levels in groundwater

Pearson correlation coefficients between fluoride and other water quality parameters measured in three different sites

Fluorine in intrusive and extrusive igneous rocks

Fluorine in metamorphic rocks

Fluorine in sedimentary rocks

The variation of fluoride ion concentrations in groundwater effect of climate.

Physical and chemical interactions of fluoride with other water quality parameters - data and correlations.

Optimum Fluoride ion concentrations calculated for South

Africa, 1985-1999

Simplified aspects on the geology of South Africa

CEV:

ABV:

WMS:

NHPB:

USNRC:

WRC:

WHO:

F

F-

DWAF:

NDQR:

SAWB:

SABS:

ANON.

WQM:

TWQR:

SI

SP

USPHS

AWWA

OFS

RSA:

EC

Copt

TAL

GIS

WMA

SSA

CDTA:

Department of~~~~r Affairs

~d

Forestt-y

N~ional Depart~nt of Health

.'

South African Weather Bureau

South African Bureau of Standards

Anonymous

Water Quality Monitoring

Target Water Quality Range

Chronic Effect Value

A.~ute Effect Value

,

,

Water MM~ement System

National Groundwater Database

United States National Research CmD1cil

Water Research Commission

World Health Organisation

Fluorine

Fluotide ion

Satmfion Index

Satur~ion Percentage

United ~tates Public Health Society

Ameri~ Water Works Association

Orange Free State

Republic of South Africa

Electrical Conductivity

Optimum Concentration

Degrees Celsius

Total Alkalinity

Geographic Information Systems

Water Management Area

Statistics South Africa

Cyclohexene diamine tetra acetic Acid

(xii)

p~soc kg g f.1g

mg ppm

T

P-Tri

Pe

Jd:

Vma:

TISAB

SAWQG:

DOH:

WC

NW

KZN

QUALDB

FS

Ksp

Total Ionic Strength Adjustment Buffer

South African Water Quality Guidelines

Department of Health

WestemCape

North-West

Kwazulu Natal

Quality database(National water quality database housed at DW AF)

Free State

Solubility product constant

Solubility product at 25 °C

Kilogram gram microgram (0,000 OOOlg) milligram (O,OOlg) parts per million or mglkg solid equivalent to Img/l in solution.

Temperature in degrees Celsius.

Irrigasie sediments (mudstone/siltstone)

Eccashale

Dolerite dyke/silt

Sandstone

The beneficial attributes of fluorides to human health have been known for many years

(WHO, 1970). The fluoride ion is a very important dietary substance. When ingested at specific doses, the fluoride ion is beneficial to both bone and dental development in human beings. At correct intake levels it plays a very important role in the formation of teeth

(Pontius, 1991). Too low fluoride intake levels during childhood may give rise to the occurrence of preventable dental caries in later years. Dental caries is a disease caused by specific bacteria harbored in dental plaque, fermenting carbohydrates to produce acids that can demineralise tooth enamel (Hammer, 1986). If this demineralization is allowed to continue, the enamel is penetrated permitting bacterial invasion and eventual loss of the tooth by decay in the absence of restorative dental care.

Too high fluoride intake normally gives rise to teeth mottling (dental fluorosis) and related problems. Chronic endemic fluorosis is a condition which is caused by an excess of fluorides in drinking water and which affects the calcification of the teeth, resulting in what is commonly known as dental fluorosis. Maughan-Brown in 1935 and Raubenheimer in

1938 first reported a study of the occurrence of mottled enamel in South Africa (WRC,

2001). In 1941, Ockerse produced three reports on human fluorosis in various regions of the former Union of South Africa. At that time 805 areas in which dental fluorosis occurred were known (Ockerse, 1947).

In 1942, Ockerse, then a Dental Health Officer, initiated a detailed and systematic survey of the distribution of endemic fluorosis in South Africa He carried out a national survey that covered the period, 1939-1942. In this report, he described the geographic distribution of endemic areas and linked the main cause of dental and skeletal fluorosis to the geology of those areas. Although the prevalence of dental fluorosis and skeletal fluorosis in South

Africa have been recognised much earlier, sporadic and small scale studies were carried out since 1947 (Zietsman, 1991, McCaffery, 1993). No national survey was carried out since then. Like other epidemiological studies around the world, the tendency has been to concentrate on the prevalence and severity of fluorosis without much attention to the study

of the distribution of high fluoride ion concentration in groundwater, the main etiological factor (WRC, 2001).

It is evident in the literature that there are various sources of fluoride. These include the ingestion of certain foods such as green tea, green vegetables like spinach, etc. (Heilman,

et al., 1997), the use of fluoride supplements such as various toothpastes, fluoride pills, mouthwash and drinking water. The occunence of Ouoride levels in drinking water and the etJed on dental health is the basis of this dissertation.

The majority of dental fluorosis sufferers (mainly blacks) in South Africa live in rural areas. These people use untreated surface and grmmdwater as sources for drinking water.

Groundwater is obtained from springs, wells and boreholes. The value of groundwater represents a strategic component of the water resources in South Africa It occurs widely.

Geographically, almost two thirds of South Africa's population depends on it for their domestic water needs (DWAF, 1997). Different studies have shown that the occurrence of dental fluorosis in the majority of cases in South Africa are related to the fluoride content of groundwater used for drinking purposes. (McCaffery, 1993;Fayazi, 1994; Du Plessis,

1995; WRC, 2001).

The occurrence of high fluoride ion concentrations in groundwater is in most cases a natural phenomenon and constitutes a serious water quality problem in groundwater worldwide (Nair, et al., 1984; MCCaffrey, 1993; Roo, 1997; Agrawal and Vaish, 1998). In cases where the concentrations are higher than 1,0 mg/l which is the guideline in most countries, de-fluoridation techniques are used. These are expensive for most developing countries and cannot be easily implemented. Some groundwater sources in South Africa contain high levels of fluoride ion concentration levels. In many cases groundwater is the only or major source of drinking water. Effects on the teeth are visible in individuals from these areas.

In cases where fluoride levels are lower than the set standards or recommended levels for dental protection, fluoridation of water supplies is an option Fluoridation is defined as the adjustment of the fluoride concentration of a public water supply by the addition of

fluoride compounds, which meet the quality standards of the Department of Health in terms of regulation 14, set under the Health Act, (Act no.63 of 1977) in order to obtain an optimal fluoride concentration for maximum benefits, (Anon, 1998).

The awareness of excess fluoride consumption through water has however been increasing countrywide. (~Caffery, 1993; Fayazi, 1994; Rudolph, et al., 1995; Du Plessis, 1995;

WRC, 2001). The issue of whether, and at what levels of concentration to manage the fluoride ion concentrations in South Africa's public water supplies is a contentious one.

While the Department of Water Affairs and Forestry (DWAF) as the custodian of the country's water resources, manages the fluoride levels through the criteria set in its guidelines, (DWAF, 1996) and the South African Bureau of Standards (SABS) specifications (SABS, 2001), the Department of Health proposes compulsory fluoridation of public water supplies (Anon, 1998). This has raised a number of concerns among various stakeholders and concerned parties.

1.2.1

Some concerns about the fluoridation of South African public water supplies

The application of the contents of the regulations under the Health Act has a lot of barriers:

• It has been shown by most research that the occurrence of fluoride in groundwater is in most cases a natural phenomenon. (Nair, et aI., 1984; McCaffery, 1993;

Fayazi, 1994; Rao, 1997; Agrawal and Vaish, 1998).

• Unlike drinking water with high levels of dissolved iron and manganese, which has both colour and objectionable taste, water containing excess fluoride is colourless and tasteless. Chemical testing is required to detect its presence. For this reason, people who live in an area and drink water with high fluoride ion concentrations are not aware of the problem until fluorosis reaches advanced stages. It is of great importance for local and regional authorities to know where the areas of high natural fluoride concentrations occur such that appropriate actions in line with the legislative requirements can be taken during fluoridation. This requires the mapping of the low and high fluoride areas in the country. This is addressed in this document.

• The lack of adequate information that could support the fluoridation exercises is one of the aspects to be considered. Investigations (geological and geochemical) need to be carried out prior to the implementation of water supply schemes and fluoridation/de-fluoridation of the same. The removal of excess fluorides from drinking water and addition of small amounts in the case of lower levels or its absence are issues of concern to the general public as well as professionals. The fact that there has been no detailed and systematic survey of the occurrence and distribution of fluorides at a national level in South Africa for several years indicated a need for this study.

• There are no published South African studies on the assessment of the environmental impact of fluoridation on the natural environment. As South

Africa is a water stressed country, with the establishment of the new Water

Management Areas, each with its unique characteristics, the impacts will be different. A range of studies to assess possible impacts in each one of them will be required.

• Regional studies (McCaffery, 1993; Fayazi, 1994) indicate that people experiencing problems of dental caries and dental fluorosis are based in rural areas where there are no established water treatment works for groundwater.

In most of these areas there is a need to clearly establish who will receive fluoride via the water supply in order to determine the viability of the policy in terms of the holistic impact.

o Exactly what proportion of the population will get fluoride via this mechanism?

o What population segment (risk profile from an oral health perspective) do they represent?

o How many live in areas where it is not viable to fluoridate?

o How many live in areas where it is not necessary to fluoridate?

o What is the size of the population gap between those that need fluoridation and those that do not need it?

o How long will it take to address this gap?

• Most current and recent research on fluorides in South Africa has been restricted to regional studies. (Zietsman, 1991; MCCaffiey, 1993; Fayazi, 1994; WRC, 2001). A national coverage or picture on the occurrence and distribution of fluorides in the country is necessary for correct decision-making concerning fluoridation/defluoridation of South African water supplies.

• In a country such as South Africa with extreme variations between very wet and very dry seasons, one might anticipate variations in fluoride content of the drinking water supplies in areas where this occurs. It is therefore important not only to know the levels of fluoride in grOlmdwater destined for domestic use but also the range of variation thereof should be accurately described before fluoride supplementation Such supplementations are usually recommended when the drinking water fluoride level is <0.7mg1t (Nicholson and Duff: 1981 ; DWAF,

1996).

• The implementation of water fluoridation is influenced by social, political and economic factors. All these need to be taken into account before any water supply is fluoridated. There is a lack of accurate knowledge about water fluoridation amongst the public and this needs to be addressed (Chikte and Perez, 1995)

• There is currently no ground water quality monitoring programmes dedicated at this problem There is also no proper ground water quality management strategy in place yet (DWAF, 2000).

The above concerns raise the following questions that need to be answered:

Where in the country and at what concentrations is fluoride found in groundwater?

How are people exposed to fluoride at its different concentrations?

What health effects are caused by fluoride ingestion?

What corrective measures can be taken to prevent endemic fluorosis?

Are there any variations in the fluoride levels of groundwater? If so what factors contribute to this?

In this dissertation, it is attempted to answer the above questions and concerns through the (oUowingaims and objectives.

1.3

AIMS AND OBJECTIVES OF TIllS STUDY

The study has three main aims:

• To determine the distribution (current and long term) of fluoride ion concentrations in

• To determine the extent of the incidences of dental fluorosis in selected areas.

• To investigate whether a relationship exists between high fluoride levels In groWldwater and the percentage morbidity of dental fluorosis in those areas.

The objectives ofthis dissertation are therefore;

• To describe the distribution of fluoride in South African groWldwater.

• To describe the current status of fluoride occurrence in groWldwater.

• To delineate those areas with fluoride concentrations in groWldwater lower or higher than the recommended limits for drinking water.

• To identify factors that may contribute to the occurrence of high fluorides in groWldwater.

• To identify areas affected by dental fluorosis.

• To compare results obtained from the assessment of the water quality data and the percentage morbidity of dental fluorosis.

• To make relevant recommendations based on the results of this study.

The usefulness of this dissertation will be:

• In the identification of the areas where there are low or high fluoride levels in groWldwater, that is, the delineation of areas in which the risk of fluorosis is absent

(optimum levels of fluoride), less severe, or critical (fluoride levels below or higher than recommended limits). This information should allow for the most efficient utilisation of the available groWldwater resources. It will contribute to correct decision making by managers especially Water Services Providers (WSPs) who have to decide whether to fluoridate or de-fluoridate water supplies, or do nothing.

• In the identification of the link between the occurrence of high fluoride levels in grOlmdwater and the occurrence of dental fluorosis.

• In the identification of factors that affect the occurrence of fluoride ion concentrations in groundwater as demonstrated by the water chemistry, geology and historical information. This will give an insight in understanding the main aspects needed in proper fluoride management in water resources and;

• In the identification of important parameters that influence the concentration of the fluoride ion in groundwater.

The above aspects and factors are very important in the study of fluorides in groundwater, as they will give more insight and information as to how to manage the problem of high or low fluoride ion concentrations. In order to achieve the above aims and objectives, the dissertation is structured as follows:

1.4

THE STRUCTURE OF THE DISSERTATION

The structure is as outlined below

CHAPTER 1: INTRODUCTION

This chapter describes the background and motivation for the study. The approach to fluoride management in South Africa is briefly outlined and concerns are highlighted. The objectives of the dissertation are also outlined in this chapter.

CHAPTER 2: CHEMISTRY AND OCCURRENCE OF FLUORIDES IN THE

ENVIRONMENT

In this chapter a detailed description of fluorides is given. This covers the occurrence and distribution of fluorides in groundwater as reflected in the literature, factors contributing to the high levels of fluoride in groundwater and beneficial effects of fluorides.

CHAPTER 3: HEALm EFFECTS OF FLUORIDES

This chapter gives a detailed description of the health effects of fluorides. The detailed descriptions are however limited to dental and skeletal fluorosis. Fluoride metabolism is also included in this Chapter.

In this chapter, general procedures used to collect, process and present the different types of data are described. Data processing is discussed.

Results obtained from the processing of the various data sets are presented. The way the data was analysed to get the information is described in detail. The information obtained from the results is discussed in terms of the set objectives, findings from the literature, guidelines and standards for fluoride in drinking water.

In this chapter, concluding remarks are made based on the results and discussions.

Reference is made to the achievement or not of the set aims and objectives.

CHAPTER 7: RECOMMENDATIONS

In this chapter, reconunendations are made. The recommendations are made in the context of special reference to fluoride problems in groundwater supplies.

THE CHEMISTRY AND OCCURRENCE OF

FLUORIDES IN THE ENVIRONMENT

The problem of high-fluoride ion concentrations in grOlmdwater is one of the most important health-related, goo-environmental issues in many countries including South Africa It is therefore important to manage fluoride at acceptable levels in our water resources. For this to happen, there must be proper understanding of the occurrence, factors that contribute to the release of fluoride into groundwater, influence of the fluoride ion concentration once it is in groundwater and hence the distribution of different levels of fluoride in groundwater. In all this, the understanding of the chemical characteristics of groundwater related to fluoride occurrence is critical.

The need to understand these aspects and achieve the aims and objectives of this study as outlined in CHAPTER ONE prompted this literature study. Included in this chapter are the following:

• The chemistry of Ouoride

• The occurrence of Ouorides

• Facton that affect the OCCUJTeJlce

• Beneficial uses of Ouoride

Due to the very pronounced electron affinity of the fluorine atom, fluorine is capable of interacting with almost every element it comes in contact with (DWAF,

1996).

It is the most electronegative of all the elements and cannot be oxidized to a positive state. It is not found in a free state in nature, but always in a combination with chemical radicals, elements or other as fluoride compounds. Fluorine forms compounds with every element except helium, neon and argon. Polyvalent cations such as that of aluminium, iron, silicon and magnesium form stable complexes with the fluoride ion Sodium fluoride (NaF), sodium silicofluoride (Na2SiF4) and hydrofluosilicic acid (H2SiF6)are the most common and frequently used fluoride chemicals.

2.2.1

Natural Waters

In natural waters, fluorine normally occurs as the fluoride ion, F.

Fluoride is thought to be one of the main ions that allow the solubilisation of beryllium, scandium, niobium, tantalum and tin.

Most simple compounds of F are readily soluble in water (WRC, 2001). The ~ and pH conditions of F- speciation are shown in Fig. 1 below. It is noted that under conditions in which water is stable, F- usually exists as the monovalent ion, F. At a pH below 3.5, F in solution may occur in the HF form (Thompson, 1994). The close similarity in size and the equivalence of the charge of OH- and

F causes interference when a fluoride ion selective electrode is used for water analysis (WRC, 2001).

l_

pH

Fig 1: ~-pH equilibrium diagram for the system F-HzO at 25°C and for total fluoride concentration less than 2000mglt. (WRC,2001)

The fluoride ion reacts readily with the calcium ion to form CaFz, which is reasonably insoluble and can be found in sediments (DWAF, 19%). Where phosphate is present, an even more

10

insoluble apatite or hydroxy apatite may form. Fluoride also reacts very readily with aluminum, a process that is made use of in the removal. of fluoride from water (WRC, 2001). It forms complexes such as (AlF

6)3or AlF2

+.

The formation of these complexes takes place rapidly, at low or high pH and temperature of groundwater and their formation can be regarded in the hydrogeological context as an equillibium process (Plankey and Patterson, 1986). The formation of these complexes depends on several other factors such as complex stability constant, the concentration of the fluoride ion in solution and complexing species (Rao, et a!.,

1993).

2.2.2

Mineral- Aqueous Fluoride Interactions

Ionic compounds of fluoride dissolve in water and these are believed to be the cause of fluoride release into groundwater. The dissolution of other F- bearing alumino silicate minerals has also been reported (WRC, 2001).

During the mineralization of various fluoride rich minerals, solubility plays an important role. Table 1, below shows the solubility products (Ksp) values of some minerals relevant to the chemistry of groundwater (Gaciri and Davies, 1993)

Mineral

Fluorite (CaF2)

Calcite (CaC0

3)

Aragonite (CaC0

3)

OH apatite

OH apatite

Selaite (MgF2)

Halite (NaCl)

Siderite (FeCOJ)

Magnesite (MgCOJ)

Dolomite

Ksp

3.4XI0

11

1 X

1O~

1 X 10

-5

2.6 X 10--4~

2.3 X

10

·41

6.4 X

10-

9

38 or 1 X 10

Oil

1 X

10

-IU.~

1 X

10 -)

1 X

1O-

1b.7

Temp.ucl pH

18

25

25

25

25

25

18, pH=7.0

40, pH =7.4

27

25

The concentrations of fluoride in groundwater have been shown to be limited by the mineral's solubility especially fluorite, such that in the presence of 10-

3

M of calcium, the fluoride ion concentration is limited to 3,1 mg/t of fluoride. It is therefore the absence of calcium in solution, which allows higher concentrations to be stable (Edmunds and

Smedley, 1996). High fluoride ion concentrations may therefore be expected in groundwater in calcium-poor aquifers and in areas where fluoride-bearing minerals are

An experiment carried out by Roo (1997) showed that the concentration of the fluoride ion m aqueous media drops with increasing bicarbonate content. The same solubility experiments carried out with fluorapatite showed an increase in the fluoride ion concentration. The results are as shown in Table 2, below.

4

5

2

3

Sample

Concentration of

Fluoride present in solution ions (mglt)

Na+

(mglt) after

HCOJ-

2 days 10 days 30 days

1 0 0 5,6 7,3 7,8

47

94

188

376

125

250

500

1000

5,8

7,0

9,5

15,0

7,5

7,8

12,0

17,0

7,8

8,5

14,0

20,0

The dominance of sodium bicarbonate waters in weathered rock formations has been found to accelerate the dissolution of CaF2 and hence the release of fluoride into groundwater in the course of time (Rao, 1997). This experiment shows another mechanism by which alkaline solutions can mobilize F from rocks. It can be explained by the following equations,

CaF2

+

Na 2C~

=

CaC0

3

+

2Na +

+

F -

CaF2

+

2NaHC~

=

CaC~

+

2Na+

+

F -

+

H20

+

CO2

When alkaline waters come in contact with rocks, they can dissolve fluoride with simultaneous precipitation of calcite. (Rao, et ai.,

1993).

The fluoride ion concentrations of groundwater can thus reach higher levels than possible during a single weatheringevaporation cycle. The potential for dissolution or precipitation of a specific mineral in an aqueous solution has also been found to depend on the mineral's solubility and the composition of the aqueous solution. The Saturation Index (SI) defined by Langmuir measures this potential.

SI

= log

(IPA/KT), where lAP is the ion activity product in the aqueous solution

Or Saturation percentage (SP)

SP

=

(IAPIKT) X

100 where K, is the equilibrium constant at temperature T

SI

=

0, SP

= 100, indicates an aqueous solution in equilibrium with respect to the mineral.

SI <

0,

SP <

100, indicates under-saturation of the solution with respect to the mineral and the tendency to dissolve.

SI >

0,

SP>

100, indicates super saturation of the solution with respect to the mineral indicating thermodynamically favourable conditions for precipitation of the mineral.

It has also been established that while the fluoride ion concentration in groundwater is inversely related to Ca

2+, it is positively related to Na\ HC03-, EC, poland other ions.

These relationships are best obtained for fluoride concentrations of

1,0-3,4

mg/l. (Rao,

1997).

Compositional characteristics of some waters include high alkalinity (pH generally greater than 7) and richness in the components Na, K, HC03-, C03

2as well as cr and

F.

These species have high solubility in water. Fe has low solubility because it is precipitated from alkaline water. Ca and Mg are low, as they are precipitated as carbonates and hydroxides respectively. Only limited incorporation ofF is permitted in the CaCOJ structure, such that there is always a net balance ofF in solution. The higher solubility product of CaC03 (Ksp

=

1

X

10

-8) favours its precipitation over CaF

2

(Ksp

=

3,4

X

10

-11).

CaF

2

(s)

Fluorite.

(HCO-1l

(H+)*(F)

2

Depending on pH, an increase or decrease in bicarbonate concentration/activity will be accompanied by a corresponding increase or decrease in the concentration of fluoride ions.

This is due to the formation of hydrofluoric acid, HF.

The fluoride ion forms complexes with elements such as AI, Mg, Fe and Be and this may be an important factor which determines the total concentration of fluorite which dissolves in groundwater. The calcium ion also complexes significantly with the carbonate and sulphate ions. This can increase the solubility of fluorite and hence its mineralization. This complexation has the effect of reducing free calcium and fluoride activities, thereby increasing the tendency of fluorite to dissolve. Silicates complexation is also possible but only in the acidic range (Rao, 1997).

2.2.3 In Soil

Soils adsorb F from dilute and concentrated solutions and this process is being used industrially

(Ginster and Fey, 1995). It has been noted that the fluoride ion mobility depends on soil type, pH of the system and fluoride ion concentrations. Retention ofF in the soil system is favored in acidic sediments containing clays and poorly ordered hydrous oxides of aluminum. Jinadasa, et

ai., 1993 investigated the F adsorption onto the surface of goethite (FeO.OH).They found that fluoride adsorption is minimal above pH 7 and increased with decreasing pH, being greatest at pH 4. In 1996, Meeusen and his colleagues concluded that the behaviour of F in a soil profile was mainly determined by adsorption onto the metal oxide and hydroxide surfaces, specifically with goethite and gibbsite. (Meeusen, et al., 1996)

2.3.

OCCURRENCE OF FLUORIDES

2.3.1 General

Fluorine is the lightest element in the halogen group. It is the 14 th most abundant element in the lithosphere. Fluorine is rarely found in its elemental state in the earth's crust. It usually forms ionic bonds with most elements of the periodic table (Gaciri and Davies, 1993; WRC, 2001,).

These compounds are called fluorides.

Bonding with anions of groups VA, VIA and VIlA

(apart from P, As and Bi) does not occur because of the high electro-negativity of fluorine.

(WRC,2001).

2.3.2 Occurrence of fluorides

in

South Africa

2.3.2.1

In Rocks

Fluorides are found in varying amounts in practically all the geological formations, especially in most igneous rocks. (~CatIrey, 1993; Fayazi, 1994). Fluorides occur most abundantly in nature as fluorspar or fluorite (CaF

2) and crinoline, a fluoride of aluminum and sodium, (Na3AIF6)

(Rawhani, 1986). Fluorspar contains 48.9% fluoride and cryolite, 54.40% (Oscerse, 1947).

Cryolite occurs to a lesser extent than fluorspar in South Africa. Various fluorosilicates (SiF6 ihave also been found. Fluorspar is found mostly in phosphate bearing rocks but it is also widely associated with granite and dolomitic formations. The majority of these deposits, however, are in small and scattered pockets normally found in the granite of the Bushveldt type, the dolomite and the limestone deposits of the Highveldt (Rawhani, 1986). South Africa's economically most significant deposits of fluorspar occur in dolomites of the Malmani subgroup (Transvaal sequence) of the North-West Province and Felsic members of the Bushveld Complex

(Munzhelele, 1998). Minor occurrences are known in KwaZulu Natal. Fluorspar deposits are also found in some of the alkali and carbonatite complexes in the Northern Province, which are of the post Bushveld age. South Africa's reserves of fluorspar are the world's second largest

(Munzhelele, 1998).

On the farm Witkop, in the North-West Province, the deposits consists of a large flat vein beneath a thin layer of shale near the surface which gives way to a pipe-shaped body with angular frameworks of dolomite enclosed in fluorspar and large number of irregular branching

veins developed along cracks and fissures (Mohlahlo, 2000). The deposit of the Vergenoeg

Mine, near Pienaarsrivier in the Northern Province grades 40% of CaF2 and occurs with abundant iron oxide in a massive deposit in felsite (Mohlahlo, 2000).

The most important geological formations in which fluorides may occur in other provinces like the Cape Provinces are the Karoo sediments, volcanics, the younger granites and felsites, the older granites and gneiss. These include the formations which are built of fragments of the above mentioned rock formations such as the Dwyka Tillite or the base of the Karoo sediments and the basalt beds of the Crestaceous system (Oscerse, 1947, Fayazi, 1994).

The following table gives the total fluoride concentrations recorded in some rocks in South

Africa:

Table 3: Total fluoride concentrations recorded in some rocks in South Africa

Rock

Lebowa granite

Area

North-West Province

Pilanesberg (whole rock mean)

North- West Province

Amphibolite North- West Province

Gneiss

North-West Province

Phosphate rock

Dolomite

North- West Province

North-West Province

F content, mgIkg

1570

Reference

M'Caffrey, 1995

M'Caffrey, 1995

27000

104- 1400

240 -2800

M'Caffrey and Willis, 2001

M'Caffrey and Willis, 2001

10400 - 42000

M'Caffrey and Willis, 2001

110 -400

M'Caffrey and Willis, 2001

Common fluoride minerals are fluorspar and fluorapatite, a calcium fluorophosphates mineral.

In South Africa the minerals, which contain variable amounts ofF-are as listed below: (Ockerse,

1947; MCCaffrey, 1993; Fayazi, 1994, and WRC, 2001).

(i) Fluorspar (CaF2)

(ii) Flourapatite (3Ca3P2CgCaF2)

(iii) The various micas

(iv) The amphiboles

(v) Tourmalite

(vi) Topaz (Ah) (Si0

4)

(OH, F) 2

(vii) Fluocerite (Cerium Lanthanum fluoride)

(viii) Apophyllite

(ix) Bultontenite

(x) Zunyite (orthosilicate of aluminum)

(xi) Ephesite

Others of importance include various fluorosilicates and mixed fluoride salts such as cryolite

(Na

3

AlF

6)

Table 4: Occurrence and Chemical composition of some minerals found in South Africa

(Ockerse, 1946, GSSA, 1986, Mohlahlo, 2000, WRC, 2001)

Mineral

Fluorite

(Fluorspar)

Formula

Composition

CaF2

Occurrence

Malmanie, Witkop and Buffelshook usually fotmd in the Bushveld Complex

Associated with red granite. Was mined in the Pilanesberg area, North -West

Province on the farm Tooyskraal, 43.2km west of Warmbaths, Ruigtepoort,

48 km South-West of Warmbaths, Grobbelaars Hoek, ± 112 km North-West of

Potgietersrus and Buffelsfontein, 4.8km North-West ofNaboom-Spruit.

Also

FOWldin alkaline intrusions North and Northeast of Pretoria. Hlabisa in

KwaZulu Natal.

Fluorapatite

3CaJ>2C g

CaF2

Spitkop farm, Eenzaam in Sekukuniland, Wallamansthal, 28.8km

92.26% Ca3 (P04)2 Noth-East of Pretoria. In dolerite Deposits.

7.74%CaF2

Various micas

Muscovites

(White mica)

Biotites (Black

Mica)

Amphiboles

Topaz

Silicates of Al,

K andH2 with

Fe, Mg, Na, Li

Silicates of

Fe,Mg,

Ca, and sometimes

Kand Sodium

A12 Si 04F2

Fluocerite

White micas, Muscovites in the Letaba District, North-West Province

, Namaqualand.

Micas form a constituent of all granites, fluorides are present in all granites in South Africa. Is a constituent of many metamorphic rocks, also in sediments.

Namaqualand, North- West Province

R20F£R=Ce, la,

Di)

Occurs in igneous rocks, granites. Bushveld Igneous Complex in the deposits on the farm Vlaklaagte, 86.4km North-East of Pretoria

Springbok Flats, North - West Province

2.3.2.3

In Soils

Fluorides in soils in some parts of South Africa are usually derived from the weathering of the underlying fluoride-bearing rocks (Fayazi, 1994). Fluorides are found in soils with high contents of phosphates, clay minerals, and colloids at its lowest concentration in light, sandy soils.

(WRC, 2001). It is generally depleted in soils relative to the parent fresh rock. This is as a result of dissolution, but the behaviour of fluorides during weathering is complex. The controlling factors evident from the literature appear to be soil type, calcium and phosphorus content including soil pH.

Traces of fluorides are present in many waters; higher concentrations are often associated with underground sources. As fluorides occur in nearly all-geological formations in South Africa, it is not surprising to find them present in variable concentrations in both surface and groundwater in many areas. Typically, the concentration of fluoride in:

• Unpolluted surface water, is approximately 0,1

mg/t

• Groundwater is commonly up to 3

mg/t,

but as a consequence of leaching from fluoride containing minerals to groundwater supplies a range of3-12

mg/t

or higher may be found

(DWAF,I996).

• Seawater, the fluoride ion concentration is found approximately at 1,3

mg/t

(DWAF, 1996).

2.3.2.4.1 In SouthAfrica

South Africa is among the noted in the world for experiencing high levels of fluoride ion concentrations in groundwater on a regional scale. Several researchers have noted the high Fcontent of certain groundwater in South Africa (Table 5). Ockerse in 1946 measured rock, soil and groundwater concentrations of F- in an attempt to understand the causes of endemic dental fluorosis. His study covered the whole of South Africa, then, the former Union of South Africa but unfortunately gave the Western Bushveld only superficial attention (WRC, 2001). He did, however, single out the Pilanesberg, Warmbaths and Pretoria Saltpan as areas with endemic dental fluorosis deserving greater investigation. He suggested that fluoride in groundwater of the

Springbok flats came from the Ecca formation and suggested fluorapatite as the source. Fayazi,

1994 suggested that the Karoo sedimentary strata contained fluorite derived from the surrounding Bushveld Granites during episodes of arid erosion.

18

In South Africa, fluoride distribution, show that groundwater with a fluoride content greater than the recommended level of 1,0 mgI1is situated in areas underlain by the Karoo sedimentary rocks

(Claren-Sandstones - TRC, Irrigasie sediments, P-TRC and Ecca Shales - Pe). The table below summarises some of the findings.

Farm name and

Number

Alexanderfontein

626KS

Alexanderfontein

626KS

Alexanderfontein

626KS

Bouw lust 660KS

Buiten post 656KS

Groote post 661KS

Groote post 661KS

Klaver Valley 671KS

Minerva 628KS

Borehole Borehole number depth(m)

7 274,3

2

5

1

213,4

300

97,5

6 85,0

2

116

5 61,0

6 61,0

4

213,4

B-number

91405725

81410539

72010657

91405762

81410369

91405750

814106485

81410440

72011085

Finmgll

11,11

13,09

10,80

8,22

19,18

10,72

12,84

11,12

25,40

Geology

P-tri/pe, Tillite

Jd

PtriIPePe Tillite

PeiConglome rate

PelVrna

PelJd

Jd

PelBedrock

P-Tri/PelBedrock

P- Tri: Irrigasie sediments (mudstone / siltstone)

Pe: Ecca shale

Jd: Dolerite dyke / silt

Vma: Sandstone

2.3.2.5

In the Biosphere

In plants, fluoride is mostly stored in the leaves, after translocation from the root system or directly from absorption from the atmosphere. The availability of fluorides to the root system is decreased by increases in the pH, phosphate, calcium, clay and organic matter content of the soil

(WRC, 2001). Typical fluoride concentrations in non-accumulator plants are below 20-mglkg dry weight.

2.3.2.6

Fluorides in the atmosphere

Due to dust, industrial production of phosphate fertilisers, coal ash from the burning of coal and various industries, fluorides are widely distributed in the atmosphere. Inhaling dust rich in fluorides is as dangerous as consuming fluoride containing food, water or drugs. Most plants obtain fluoride through the polluted atmosphere. However, air is typically responsible for a small fraction of total fluoride explosure (USNRC,

1993).

In non-industrial areas, the fluoride concentration in air is typically quite low

(0,05 to

1,90 mg F-/m

3

(WHO,

1986).

In areas where fluoride-containing coal is mined or phosphate fertilisers are produced and used, the fluoride in the air is increased leading to increased exposure by the inhalation route. High levels of atmospheric fluoride occur in areas of Morocco and China (Haikel et a1.,

1986).

In some provinces of China, fluoride concentrations in indoor air ranged from

16 to

46 mg/m

3 owing to the indoor combustion of high-fluoride coal for cooking, drying and curing food (WHO

1996).

Indeed, more than 10 million people in China are reported to suffer from fluorosis related to the burning of high fluoride coal. (Guo and Wang,

1998)

2.3.2.7

In food

Ingesting food and drinking water containing fluorides over a period of time is likely to result in toxic manifestations. It is well recognised that consuming fluoride contaminated food or water for a period of 6 months to a year is adequate to have ill effects on the health especially during childhood. The details on the health effects of fluorides on human health are given in Chapter three of this dissertation. Virtually all foodstuffs contain at least traces of fluoride.

All vegetation contains some fluoride that is absorbed from soil and water. Vegetables and fruits normally have low levels of fluoride,

(0,1-0,4 mglkg) and that typically contributes to little exposure. (Heilman, et al.,

1997).

However higher levels of fluoride have been found in barley and rice (about 2 mglkg) and taro, yams and cassava have been found to contain relatively high fluoride levels (WHO,

1986).

High concentrations in tea can be

3-

300 mg/kg (average

100 mg/kg), so

2-3 cups of tea contain approximately

0,4-0,8 mg

(WHO,

1984).

In areas where water with high fluoride content is used to prepare tea, the intake via tea can be several times greater. In general, the levels of fluoride in meat have been found in the range of

0,2-1,0 mg/kg. In fish levels of

(2-5 mg/kg) have been recorded

(Heilman,

et aI, 1997).

Seafood contains significantly higher fluoride concentrations compared to freshwater food.

Fluoride accumulates in bone and the skeleton of canned fish such as salmon and sardines

(Hammer, 1986). Fish protein concentrates may contain up to 370 mglkg fluoride.

However, even with a relatively high fish consumption in a mixed diet, the fluoride intake from fish alone would seldom exceed 0,2 rng ofF per day (WHO, 1986).

Dietary studies have shown that fish accumulate fluoride in hard tissues and in parts of

South East Asia this resulted in some human populations having a high fluoride diet. Those parts of fish in contact with the water, such as scales, fins and gills, have high fluoride levels. Skin is very high in fluorides and predators consuming the whole fish are subject to much higher fluoride levels than man who often removes skin first (Heilman, et al., 1997).

Dairy feed and mineral supplements may contain high levels of fluoride, up to 200 mg/kg, though most are fewer than 30 mglkg. Cows may thus get more than their daily dose of fluoride from this source before water and forage are even considered.

Bone meal supplements can be very high in fluoride since cattle grazing contaminated pastures may accunmlate 100 mg fluoridelkg of bone, the normal level is 15 mg fluoridelkg. Results from a detailed study on dietary sources are summarised below (Heilman, et aI, 1997).

Food source State

Green tea

Ham

Cooked

Baked

Greens Raw

Chocolate cake

Baked

Fish

Toothpaste

Fried

Mouth wash

Gel treatments

Oatmeal

-

-

-

Cooked

Rice Krispies

Cottage Cheese

Coffee

-

-

Krispies

Noodles

Cooked

Mashed potatoes Cooked

Minestrone soup

-

Spinach

Cooked

Rice

Spaghetti sauce

Cheerios

Peas

Toast

-

Cooked

Cooked

-

Cooked

Sausage

Potatoes

Pork, roast

Whole-wheat bread

-

Boiled

Roasted

-

Quantity

(g1other)

l00g l00g l00g l00g l00g l00g l00g l00g l00g

100g l00g l00g l00g

6 cups l00g l00g l00g l00g l00g

Y2 a teaspoon l00g l00g l00g l00g l00g

F contentmg

3.3

3.3

3.0

2.7

2.5

2.5

4.1

3.7

3.5

2.1

1.7

160-660

1.7

1.5

1.3

1.3

5.9

5.0

5.0

4.6

4.3

1000

4000

13000

10.6

2.4

FACTORS mAT CONTRIBUTE TO TIlE OCCURRENCE OF

HIGH FLUORIDEIN GROUNDWATER

The incidences of high fluoride ion concentrations in groundwater has been attributed to various causes:

• High F content of aquifers

• Low grOlmdwater flow rates

• Semi-arid climate increasing potential evaporation

• High pH waters

• Weathering of alkaline volcanic rocks rich in F

• Fluorspar mineralization and occurrences of rock phosphate deposits

• Granites, gneisses and other crystalline rocks having many fluoride bearing minerals as their essential and accessory mineral composition

• Residual soils including micaceous sand

• Variation in soil texture

• Industrial activities and use of pesticides and insecticides (less common and rare in most cases).

• Various volcanic activities (Rao, et ai, 1993, Fayazi, 1994, Rao, 1997, Agrawal and Vaish, 1998, WRC, 2001).

In the majority of cases, the incidence of high fluoride ion concentrations in groundwater is mainly a natural phenomenon, influenced basically by the local and regional lithological setting, mineralization characteristics and hydrogeological conditions.

(Fayazi,1994; Rao, 1997,

Agrawal and Vaish, 1998). The continuous and long term weathering and leaching mainly by moving and percolating water play the important role in the release of fluoride from minerals, soils and rocks into groundwater. (Fayazi, 1994, Agrawal and Vaish, 1998). In South Africa, it has been confirmed that the general distribution of the fluoride ion in "problem areas" is controlled by the geochemistry of the rock in which the groundwater is encountered

(M"Caffrey, 1993, Fayazi, 1994;WRC, 2001). Lithological controls suggest that the cause of high fluoride concentrations in grOlmdwater is due to the dissolution of fluoride bearing minerals in bedrock and soil (MCCaffrey, 1993). The above factors can be classified into three nuYor classes as described below:

Class

III

Climatic conditions (comparatively temperatures and precipitation favour effective chemical weathering (Nanyaro, et ai., 1984). The composition of the waters therefore reflects partly the lithology of the drainage basins. During arid episodes and the process of erosion, weathered products derived from granitic rocks containing fluorite in the groundwater at this point. (Fayazi, 1994). Groundwaters associated with dolerite dykes and silts, which have intruded sedimentary rocks often, have a relatively high fluoride content.

It has been found that higher fluoride concentrations are obtained in discharged area than in recharge areas, with a trend of fluoride enriched along the direction of flow. These features have been attributed to the smaller quantities of dissolved solids in the recharge areas.

(Qaciri and Davies, 1993).

Industrial processes also contribute to the presence of fluorides in groundwater. Quantities of fluorides pour into the atmosphere each year from aluminium smelters, phosphate processing, coal burning, manufacturing of steel, fluoride compounds, bricks and glass products. Such industries that use fluorides either as raw materials in the manufacturing process or in which they arise as by-products or may even be end-products include enamel, pottery, welding, refrigeration, rust removal, oil, refinery, plastic, pharmaceuticals, fertilizer, automobile and toothpaste industries. However, this route is less important at the moment as the most affected and vulnerable are plants and livestock.

• Factors relating to the availability of fluorides that pass into the hydrological system, namely volcanic activity associated with rift formation and the composition of the volcanic rocks and other types of rocks.

• Factors determining the residence times of dissolved fluorides in the waters, i.e., chemical reactions especially involving the species, Ca

2+ and F, among others.

• Factors of generally lesser significance may however become locally important, these include the injection of fluorides into the hydrological system by industrial operations, for example, fluoride mining and introduction of fluoride through atmospheric precipitation and dissolution of salt crusts. Examples under each class are described below.

Volcanism is an important factor determining fluoride content of the natural waters (Gaciri and Davies, 1993). Four major geological systems are evident: metamorphic rocks of

Precambrian age, sedimentary rocks of Carboniferous to Creataceous age, Tertiary and

Quartenary volcanics and Unconsolidated Tertiaty and Quarternary sediments. It is the chemical leaching, weathering of these rocks and their associates that contribute to the release of fluoride into groundwater. Waters from these volcanic rocks have shown relatively high fluoride content, up to 180 ppm or more. The fluoride content of amphiboles from metamorphic rocks worldwide varies from 30 to 21 400 mglkg (Gaciri and Davies,

1993). In this process the solubility of the mineral plays an important role. (See 2.2.2

above)

Besides geological changes, which result in changes in recharge composition and mixing, several chemical processes have been identified as being important in controlling the major ion chemistry. Other existing minerals in the subsurface and other major and minor ionic constituents of groundwater may affect the dissolution characteristics of minerals, for example fluoride, CaF

2,

(Rao, 1997).

3.1

INTRODUCTION

Many water quality assessment and epidemiological studies of possible adverse effects of longterm ingestion of fluoride via drinking water have been carried out. These studies clearly establish that fluoride primarily produces effects on skeletal tissues (bones and tissues) (Chen,

1993; MCCaffrey, 1993, DWAF, 1996; Ogera, 1997;Guo and Wang, 1998; Muller,

et aI., 1998).

Low concentrations provide protection against dental caries, especially in children This protective effect increases with concentration up to about 2mg1t of drinking water. The minimum concentration of fluoride in drinking water required to produce this effect is approximately 0,5 mgIt (WHO, 1994; Du Plessis, 1995). High fluoride concentrations exert a negative effect on the course of metabolic processes and consequently individuals may suffer from dental fluorosis, skeletal fluorosis, osteoporosis and non-skeletal manifestations or a combination of these.

Since the use of groundwater discussed in this study is mainly for drinking purposes, the effects discussed in this study will be limited to those effects caused by ingesting fluoride via drinking water. The scope of this dissertation is limited to the effect on dental health.

In order to understand these effects fluoride metabolism will first be discussed.

3.2.1

Absorption

Approximately 75-90% of ingested fluoride is absorbed. (DWAF, 1996)

In an acidic stomach, fluoride is converted into hydrogen fluoride (HF) and up to about 40% of the ingested fluoride is absorbed from the stomach as HF. (Clair, et al., 1994). High stomach pH decreases gastric absorption by decreasing the concentration of HF. Fluoride not absorbed in the stomach is absorbed in the intestine and is unaffected by pH at this site. (Whitford, 1997). Relative to the amount of fluoride ingested, high concentrations of cations that form insoluble complexes with fluoride (e.g. calcium, magnesium and aluminium) can markedly decrease gastrointestinal fluoride absorption (Whitford, 1997). When water-containing fluoride is consumed, some fluoride is retained by fluids in the mouth and is incorporated onto the teeth by surface uptake

(topical effect). The rest enters the stomach where it is rapidly adsorbed by diffusion through the

26

stomach walls and intestines. Fluoride enters the blood plasma and is rapidly distributed throughout the body, including the teeth (systemic effect).

3.2.2 Distribution

Once absorbed into the blood, fluoride readily distributes throughout the body, tending to accumulate in calcium rich areas such as the bone. This includes the teeth (WHO, 1996).

Because of the systemic effect, the fluoride ion is able to pass freely through all cell walls and is available to all organs and tissues of the body. Distributed in this fashion, the fluoride ion is available to all skeletal structures of the body in which it may be retained and stored in proportions that generally increase with age and intake. Under certain conditions, plasma fluoride levels provide an indication of the level of fluoride in the drinking water consumed.

USNRC, 1993 notes that, when water is the major source of fluoride intake, some plasma fluoride concentrations of healthy young or middle-aged adults expressed in micromoles per litre are roughly equal to the fluoride concentrations in drinking water expressed as milligrams per litre (USNRC, 1993).

3.2.3 Excretion

Fluoride is excreted via urine, faeces and sweat (WHO, 1996). Most is excreted via urine with faeces and sweat playing only a minor role. Urinary fluoride clearance increases with urine pH due to a decrease in the concentration ofHF. Numerous factors, for example, diet and drugs can affect urine pH and thus affect fluoride clearance and retention (USNRC, 1993).

3.3

BENEFICIAL USES OF FLUORIDES

The beneficial attributes of fluorides to human health have been known for some years (WHO,

1970; WHO, 1984a; Hammer, 1986; Pontius, 1991; WHO, 1994; Du Plessis,1995 ). When ingested at specific doses, the fluoride ion is beneficial to both bone and dental development in human beings.

The beneficial plateau is generally between 0,5 and 2,0mg/l depending on average ambient temperatures which control fluid intake and thus the total dose/day. The total daily intake of fluoride from food is about 0,2-0,5mg, which is only 10-15% of the desirable dose (Pontius, 1991, Boyle and Chagnon, 1995). It has been noted that the fluoride ion is a normal constituent of all diets and at correct concentrations it has beneficial effects in preventing dental caries (Pontius, 1991).

Dental caries is a disease caused by specific bacteria harboured in dental plaque, fermenting carbohydrate to produce acid that can demineralise tooth enamel (Hammer, 1986). If this demineralisation is allowed to continue, the enamel is penetrated permitting bacterial invasion and eventual loss of the tooth by decay in the absence of restorative dental care. It can be reduced by the use of fluoride products. The level of dental caries (measured as the mean number of decayed, missing or filled teeth) falls from seven at a fluoride concentration of 0,1mg/l to around

3,5 at a fluoride concentration of 1,Omg/l. As the fluoride ion concentration increases further (up to 2,6mg/l) dental decay continues to fall, but only slightly (Dean, 1942; USPHS, 1991). The optimal level of fluoride for a temperate climate has been found to be around 1,0mgll. This concentration seems to be associated with a substantial resistance to tooth decay but with only a small and cosmetically insignificant increase in the prevalence of dental fluorosis. For an individual, other effective methods for the prevention and control of caries are to restrict intake of dietary sugars and plaque control by flossing and brushing.

Other beneficial uses, which are not discussed in detail in this survey, include various industrial uses, adjustment of fluoride levels in water supplies, termed water fluoridation. A brief discussion on fluoridation is given in Chapter one. The benefits of water fluoridation have been found to be mostly in children. These include:

• The reduction of the likelihood of dental abscesses,

• The reduction of the risk of toothache,

• The reduction of the need for tooth extractions and general anaesthesia and

• the reduction of the cost of dental treatment.

3.4

EFFECTS OF FLUORIDES ON HUMAN HEALTH

3.4.1 General

The effects on skeletal tissues (bone and teeth) caused by the consumption of drinking water rich in fluorides are well documented. (Driscoll,

et aZ.,

1985; Hammer, 1986; Brouwer,

et aZ., 1988,

Du Plessis, 1995). Both deficient and excessive amounts of fluoride may be harmful to human health. Where the concentrations are low, tooth decay results and where they are high, dental fluorosis (mottling oftooth enamel may occur). (Gosselin,

et aI., 1999).

28

3.4.2

The Significance of low fluoride ion concentrations in drinking water supplies

In 1938, Dean presented information, which demonstrated that dental caries is less prevalent when mottled enamel occurs (USPHS, 1991). From his studies a hypothesis evolved:

Approximately 1,0mg/l of fluoride ion is desirable in public waters for dental health. At decreasing levels, dental caries became a serious problem This dental caries-fluoride hypothesis has served as the basis for programs of supplementing public water supplies having low fluoride levels with fluorides to bring the concentration up to about Img/l. The main significance of the existence of low fluoride levels in water supplies is the development of dental caries. However fluoride may give rise to mild dental fluorosis at drinking water concentrations between 0.9 and

1,2 mg/t.

This has been confirmed in a series of studies carried out in China. (Chen, et

aI., 1993;

Clair, et a!., 1994). These studies showed that, with drinking water containing 1,00 mg/l of fluoride ion concentration dental fluorosis is detected in some populations.

3.4.2.1

Dental Caries

Dental caries is the commonest disease that is affecting mankind and produces a permanent breakdown of tooth substance (Muller, et al., 1998). It happens when bacteria on the surface of the teeth ferment carbohydrates to produce acids that then destroy the hard, calcified tooth tissue.

Fluoride interferes with the metabolism of bacteria, and inhibits the production of the acid by decay-causing bacteria. (Pontius, 1993). This results in a change in the population of bacteria in dental plaque.

In South Africa, tooth decay is one of the most common health problems and leads to loss of working and schooling days as a result of pain and suffering (Muller, et al., 1998). Caries affects

90 to 93% of the South African population (VanWyk, 1995). The fluoridation of public water supplies is aimed largely at the developing community; fluoride levels of 0,3 to 0,4

mg/t

will be able to reduce the incidence of caries by 56% (Carstens, 1995). The low costs of adding fluoride to water, the fact that 80% of the people in South Africa are dependant on the state, and the high incidence of caries, particularly among the developing communities makes it a moral issue to regulate fluoride levels in drinking water (Muller, et al., 1998). The effects on the labour force make it an economic issue.

3.4.2.2

Remediation

In 1930s and 1940s, studies in the United States found that natural levels of Img/l fluoride reduced the incidence of dental caries by approximately 50% (WHO, 1994). Lifetime consumption of fluorides, whether taken systematically or used topically, significantly reduces the incidence of dental caries. (Hargreaves, 1990, Murray, et aI., 1991). Fluoride is essential to the development of resistance to caries and these benefits are for a lifelong duration. It reduces the susceptibility of teeth to caries by stabilising the apatite crystal of the dental enamel, making it more acid resistant and results in remineralisation of the enamel. (Pontius, 1993). Fluoride is essential from birth until the permanent teeth have been formed as it is incorporated into the tooth enamel, which is formed before the teeth erupt In instances where water supplies have been found to be deficient in fluoride ion concentration people have resorted to water fluoridation.

3.4.2.3

Fluoridation

Water fluoridation has been defined as the deliberate adjustment (either by increasing or decreasing) of the fluoride levels of a water supply so that the greatest protection against dental caries is produced with the least risk of dental fluorosis (Pontius, 1991). But this is confusing, since fluoridation is generally understood by the public as only the addition of fluoride to drinking water supplies. The definition connnonly used in South Africa is as provided in Chapter one of this Thesis, that is, the adjustment of the fluoride concentration of a public water supply by the addition of fluoride compounds, which meet the quality standards of the DepartIOOntof

Health.

3.4.3

The Significance of High fluoride ion concentrations in drinking water supplies

Churchill of the Aluminium Co. of America obtained substantial evidence that fluorides are the cause of mottled enamel in 1930. Churchill through spectrographic analysis, found appreciable amounts of fluoride ion in the Bauxite water supply. In collaboration with McCKay, a dentist of

Colorado Springs, Colorado, studied waters from five areas where mottling was endemic and from 40 areas where it was not a problem From these studies it was concluded that excessive fluoride levels in drinking water are the cause of mottled enamel. Their data showed that mottling did not appear unless the fluoride -ion concentration was in excess of Img/l and that the degree and severity of mottling increased as the fluoride level rose. (Clair,

et aJ.,

1994).

30

In South Africa, researchers have proved in various research works that excessive fluoride causes dental fluorosis. (Oscerse, 1946; McCaffery, 1993; Du Plessis, 1995; WRC, 2001). When fluoride levels in drinking water exceed 1,5 to 2,0 mg/t, dental mottling occurs, the severity of which increases with increasing fluoride concentration. (Boyle and Chagnon, 1995). High doses of fluoride interfere with carbohydrate, lipid, protein, vitamin, enzyme and mineral metabolism.

The current threshold for fluoride chronic poisoning as recommended by the DWAF is 4mg/t

(DWAF, 1996). Skeletal fluorosis may occur when concentrations of fluoride in water exceed 3-

6 mg/l and becomes crippling at intakes of 20-40 mg/day. This is the equivalent to a fluoride concentration of 10-20 mg/t, for a mean daily water intake of two litres. (DWAF, 1996).

3.4.3.1

Dentalfluorosis

Dental fluorosis is associated with the ingestion of high levels of fluorides. It is characterised by discoloured, brown stained or blackened, mottled or chalky white teeth. (See Fig 2 below). These effects are not apparent if the teeth were already fully-grown prior to fluoride over exposure therefore, the fact that an adult may show no signs of dental fluorosis doesn't necessarily mean that his or her fluoride intake is within the safety limit. Dental fluorosis is a clear indication of over exposure to fluoride during childhood when the teeth were developing (Driscoll,

et aI,

1985).

(g)-(h) (i)-(j) (k)-(1)

Fig 2: (a)-(b) Mild dental fluorosis , white opaque areas cover tooth surface , Bro w n stains starti ng to build up .

(c)-( d)-Very mild dental fluorosis , the tooth surfaces covered by white opaque , pa p e r-white

(e)-( f) Brown stain superimposed on white cloudy ar e as. Brown stain equals enam e l loss

(g)-( h) severe dental deca y accompanied by dental fluorosis

(i)-(j ) severe dental fluorosis, chipping and large brown stains, loss oftooth struct ure.

(k)

-(1) the enamel damage effects more teeth , unsightly and weakened teeth res ult .

Most of ena mel has been lost from tooth surface .

The protective layer is gone due to denta l fluorosis.

End emic fluorosis is very high in China (Chen ,

et ai ,

1993; Guo and Wang, 1 998). It exits in alm ost all provinces , municipalities and autonomous regions .

According to the 1997 statistics, the population in the disease stricken areas was around 100 million , with more than 2 .

7 million bon e fluorosis patients .

There are v arious types of endemic fluorosis in China , o ne caused by drin king water contaminated with high fluorides, eating or drinking foodstuffs rich in fluoride such as green tea and the one caused by exposure to coal burning.

While there are a variety of ways of describing dental fluorosis, Dean's 1942 description is still extremely useful and widely used in epidemiological studies. (Brouwer, 1988; Du Plessis, 1995).

Normal

The enamel presents the usual translucent, semi-vitriform type of structure. The surface is smooth, glossy and usually of a pale creamy white colour.

Questionable The enamel discloses slight aberrations from the translucency of normal enamel, ranging from a few white flecks to occasional white spots. This classification is used in those instances where a definite diagnosis of the mildest form of fluorosis is not warranted and a classification of "normal" not justified.

Very mild

Small, opaque, paper-white areas scattered irregularly over the tooth, but involving less than approximately 25% of the tooth surface.

Frequently included in this classification are teeth showing no more

Mild

Moderate

Severe than 1-2mm of white opacity at the tip of the summit of the cusps of the bicuspids or second molars?

The white opaque areas in the enamel ofthe teeth are more extensive but do not involve as much as 50% of the tooth.

All enamel surfaces of the teeth are affected, and surfaces subject to attrition show marked wear. Brown stain is frequently a disfiguring feature.

Includes teeth fOI'Irerly classified as "moderately severe" and

"severe". All enamel surfaces are affected and hypoplasia is so marked that the general form of the tooth may be altered. The major diagnostic sign of this classification is the discrete or confluent pitting. Brown stains are widespread and teeth often present a corroded-like appearance.

Dental fluorosis is a sign of chronic fluoride poisoning in children under six to seven years of age. Unfortunately this is only seen years after the damage, which is irreversible has been done.

The recommended upper limit to prevent dental fluorosis varies from region to region, as the fluoride concentration is dependent on the environmental temperatures.

This has been defined as the hardening or abnormal bone density, which develops in a person as a result of drinking water with more than 3 mg/l of fluoride (Rajagopal and Tobin, 1991).

Crippling skeletal fluorosis has been observed where drinking water contains over 10 mg/l

(WHO, 1984a). The level of fluoride in drinking water necessary to produce crippling skeletal fluorosis can vary markedly from one region of the world to another. This has been observed in the results obtained from Senegal (Brouwer, et al., 1988) and the United States example (Leone,

et al., 1955; USNRC, 1993). Brouwer, et al., (1988) observed that of the 42 individuals in

Senegal who had been exposed to fluoride drinking water levels of 7,4 mg/t and llmg/t, 26% had developed crippling skeletal fluorosis. There were more cases of crippling skeletal fluorosis than those reported for the entire of the USA The reason for this marked difference at essentially the same fluoride level is most likely due to marked differences in local conditions, such as diet, water consumption rates which could result in higher fluoride exposure.

Fluoride effects on bone tissues have been found to be cumulative and manifests in a number of stages with the less serious occurring early in the natural course ofthe disease. Whatever may be the type of fluoride exposure, the clinical picture in chronic poisoning occurs in the following phased manner.(Dean, 1942b)

Preclinical phase

Asymptomatic, slight radiographically detectable increases in bone

Phase I mass.

Musculoskeletal: sporadic pain, stiffness of joints, osteosclerosis of

Phase II

Phase III pelvis and spine.

Degenerative and destructive: chronic joint, arthritic symptoms, slight calcification of ligaments, increased osteoclerosis.

Crippling fluorosis: limitation of joint movement, calcification of ligaments/neck, spinal column, crippling deformities/spine and major joints, muscle wasting, neurological defects/compression of the spinal cord.

Whether dental or skeletal fluorosis is irreversible or not and if no treatment exists, the only remedy is prevention by keeping the fluoride intake within safe limits. In places where fluorosis is due to excessive intake of fluoride from drinking water, there should be a shift from that source of drinking water to alternative water sources with lower fluoride concentration or the

34

water should be partially de-fluoridated. Since alternative water resources are scarcely available, especially in developing countries in Africa and Asia, the only solution is de-fluoridation. The constraint is that these methods have proved to be expensive. Prolonged exposure to 10-20 mg fluoride/person/day for more than six years can lead to crippling skeletal fluorosis, in which osteosclerosis, ligamentous and tendinous calcification and extreme bone deformity result.

3.4.3.3

Other effects

Chronic effects on the kidneys have been observed in persons with renal disorders including effects on the thyroid gland, which may occur with long term-exposure to high fluoride concentrations (WRC, 2001). The data and documented information available on this subject are, however, too limited to allow a quantitative evaluation of the increased sensitivity to fluoride toxicity of such persons. (Janssen,

et aI, 1988).

Where incidents of acute intoxication have been reported following overdosing in water supplies, fluoride levels have ranged from 30 to 1000 mg/l (Janssen, et aI, 1988). Some acute effects at high fluoride concentrations include haemorrhagic gastro enteritis, acute nephritis and injury to the liver and heart muscle tissues. Many symptoms of acute fluoride toxicity are associated with the ability of fluoride to bind to calcium However, the details of other fluoride effects in human beings are beyond the scope of this dissertation

3.4.3.4

De-fluoridationtechniques

As soon as excessive amounts of fluorides in water supplies had been established as the cause of dental fluorosis, research on methods of de-fluoridation were initiated. The passing of water through various types of de-fluoridation media such as tricalcium phosphate, bone char, fishbone charcoal, (Bhargava and Killedar, 1992), bone meal and activated alumina was found to accomplish fluoride removal by a combination of ion exchange and sorption. Fluorides can also be removed during lime softening through co precipitation with magnesium hydroxide, or by alum coagulation (Schoeman and Botha, 1985; Schoeman, 1987;Saha, 1993). The details of these methods are not discussed in this dissertation.

Concerns about the effects of fluorides on human health have led a lot of countries to be engaged in research work. This has included the determination of safe levels, standards and guidelines for fluoride ion concentrations in drinking water.

35

A lot of work has been done to establish drinking water standards for fluoride in South Africa and in other countries of the world. (Laksham, 1979; Hammer, 1986; Brouwer,

et aI., 1988;

WHO, 1996). The general conclusion emanating from all findings is that it is particularly important to consider climatic conditions, volumes of water intake and other factors in setting national standards for fluoride. This point is extremely important, not only in setting national standards for fluoride but also in taking data from one part ofthe world and applying it in regions where local conditions are significantly different.

Temperature has been used in most cases to determine the optimum fluoride concentration at which minimal or no health effects will occur. This is because of a general understanding that water consumption is dependent upon environmental temperature. (Laksham, 1979; Hammer,

1986; DWAF, 1996). In 1992,

1.

B. du Plessis in the OFS Goldfields in South Africa conducted a study. The aim of this study was to determine the maximum concentration of fluoride in water that will not cause dental fluorosis. When comparing the results of this study with the results from other studies in the USA an extrapolation of 0,7-mg/t-fluoride concentration was made for the study area

In South Africa, the Target Water Quality Range (TWQR) of 0-1,0 mg/t fluoride is set for human health. This is the concentration range in water necessary to meet requirements for healthy tooth structure. This concentration is a function of daily water intake and hence varies with annual daily air temperature. A concentration of approximately 0,75 mg/t corresponds to a maximum daily temperature of approximately 26°C-28°C. No adverse health effects or tooth damage is expected under these conditions. (DWAF, 1996). The following tables show the current guidelines, recommendations and standards for fluoride in South Africa The guidelines are specifically for drinking water or domestic purposes. It should be noted however that the

South African Water Quality Guidelines are aimed at protecting the water resources such that the water remains fit for its intended uses. They thus only give a description of the effects on water users when the concentration of a particular constituent increases beyond the recommended level.

Table

9:

Drinking water quality standards and guidelines for fluoride in South Africa, effects of fluoride on aesthetics and human health

Fluoride Range (mglt)

Effects

Range (0-1,0)

The concentration in water necessary to meet the requirements for healthy tooth structure is a function of

Target Water

Quality daily water intake and hence varies with annual maximum daily air temperature. A concentration of approximately 0,75mgll corresponds to approximately

26 to 28°C. No adverse health effects or tooth damage

occurs.

1,0-1,5

1,5-3,5

3,5-4,0

4,0-6,0

6,0-8,0

>8,00

>100

>2000

Slight mottling of dental enamel may occur in sensitive individuals. No other health effects are expressed.

The threshold for marked dental mottling with associated tooth damage will probably be noticeable in most continuous users of the water. No other health effects occur.

Severe tooth damage especially to infants' temporary and permanent tee~ softening of the enamel and dentine will occur on continuous use of the water.

Threshold for chronic e.ffects of f/Iloride exposllre,

manifested as skeletal effects.

Effects at this concentration are detected mainly by radiological examination, rather than overt.

Severe tooth damage especially to the temporary and permanent teeth of infants, softening of the enamel and dentine will occur on continuous use of water. Skeletal fluorosis occurs on long-term exoosure.

Severe tooth damage especially to the temporary and permanent teeth of infants, softening of the enamel and dentine will occur on continuous use of water.

Pronounced Skeletal fluorosis occurs on long-tenn exoosure.

Severe tooth damage as above. Crippling skeletal fluorosis is likely to appear on long- term exposure

Threshold for onset acute fluoride poisoning marked by vomiting and diarrhea

The lethal concentration of fluoride is approximately

20oomgll.

Source: DWAF, 1996 (1st issue), South African Water Quality Guidelines for Domestic

Water Use

In 1 9 98, t he Department of Water Affair and Forestry, the Department of Health and the Water

Rese a rch Commission i n South Africa jointly published an assessment guideline . The guideline is cu r rently and widely used to assess the quality of domestic water supplies .

Ta ble 10 provides the g u idelines for fluoride in drinking water.

Tabl e 10 : Fluoride guideline (WRC , 1998)

F l uor i de DRINKING

FOOD

PREPARATION

BATIl lNG LAUNDRY

• Blue-Ideal

D

Green-Good

D

Yellow-Marginal

• P urple Com p letely unacceptable

Table 11: Recommended quality (health) guidelines for drinking water for elements and ions in the Republic of South Africa (RSA) waters, (DW AF, 1996). All values in

EC.

mgIt except pH and

Parameter in mglt except for

ECandpH

EC (mS/m, 25°C) pH low pH High

Ca

Mg

Na

K

Cl

S04

F

(N~

+

N0

2) as N

Maximum limit of no risk, idealgood

150

4.5

10

150

100

200

50

200

400

1,0

10

Low risk range,

Marginal

150-370

4,5-4,0

10-10,5

150-300

100-200

200-400

50-100

200-400

400-600

1,0-1,5

10-20

Medium - high risk range, Poorunacceptable

370

<4,0

>10,5

>300

>200

>400

>100

>600

>600

>1,5

>20

The guidelines presented in Tables 9, 10 and 11 above are currently in use in the country as they strongly complement each other. This assist both the user and water provider in assessing the quality of the water and taking appropriate decisions in cases where the water does not comply with set guidelines and limits.

Table 12: drinking water.

Chemical requirements-macro determinants for drinking water. Standards for

1

2

Determinants

Units

Ammonia as mg/t

N

3 4

Upper limit and ranges

Class 0

(Ideal)

5

6

Class II water

Class 1

Class II consumption

(Acceptable) Max.allowable

period, a max.

<0,2

0,2-1.0

>1,0-2,0

No limit

D

Calcium as

Ca mg/t

Chloride as

Mg/l

cr

Fluoride as

F-

mg/l

Magnesium

mg/l

asMg

(Nitrate and

mg/l

nitrite) as N

Potassium as mg/t

K

Sodium as mg/t

Na

Sulphate as mg/t

SO/-

Zinc as Zn

mg/l

<80

<100

<0,7

<30

<6.0

<25

<100

<200

<3,0

80-150

100-200

0,7-1,0

30-70

6,0-10,0

25-50

100-200

200-400

3,0-5,0

>150-300

>200-600

>1,0-1,5

>70-100

>10,0-20,0

>50-100

>200-400

>400-600

>5,0-10,0

7 years

7 years

1 year

7 years

7 years

7 years

7 years

7 years

1 year a

The limits for the consumption of class II water are based on the consumption of 2t of water per day by a person of mass 70kg over a period of 70 years.

b

These values can indicate process efficiency and risks associated with pathogens.

3.6

Optimum fluoride levels

The optimum fluoride level in water is the level that produces the greatest protection against caries with the least risk of fluorosis. Based on fluoridation studies conducted in the United

States, the US Environmental Protection Agency has established optimum and approval limits for fluoride in public water supplies. (Hammer,1986; WRC, 2001). Similar exercises have been accomplished in other parts of the world including Africa. The recommended optimum concentration for a community is based on the annual average of the maximum daily air temperature from temperature data obtained for a minimum of 5 years and is calculated as follows:

Copt (0,34Y(0,16+ 0,11 n

I

Where Copt

T

= optimum fluoride concentration, mg/t annual average maximum daily air temperature in

°c.

The following formula has recently been used in South Africa for the calculation of optimal fluoride ion concentrations in drinking water.

The approval limit, which is the maximum allowable concentration to prevent excessive dental fluorosis, is double the optimum concentration. The requirements of the Department of Health for health teeth are based on the optimum concentration to promote dental health.

4.1

INTRODUCTION

For many years the Department of Water Affairs and Forestry has been gathering groundwater quality data from around the country as part of ad hoc groundwater resources investigations. Yet little national-scale investigation of data has taken place, except for the depicted map on the Groundwater resources of the Republic of South Africa (Vegter, 1995).

This data gathering process intensified over the past years as a result of regional groundwater mapping programmes and the establishment of a national groundwater qualitymonitoring network in 1994.This included the big survey that was done by the Chief

Directorate Water Services ofthe DWAF on the quality of water used for domestic purposes throughout South Africa. This survey was based on existing data obtained from DWAF ' s databases as well as data from other organisations and Non-governmental organisations

(NGOs).

The groundwater quality data collected prior to 1994 was transferred onto the

National Water Quality Database (QUALDB). This database containing over 55 000 analyses of groundwater samples, mostly of macro elements, has been recently replaced by the Water Management System (WMS). At the time of writing this dissertation this transfer was ongoing. It is possible that some of the data, which will be a few points, were not yet on the WMS. Data from the National Groundwater Quality Monitoring Network is included.

4.1.1

Water Management System (WMS)

The Water Management System is housed at the Institute for Water Quality Studies (IWQS), a directorate within the Chief Directorate Scientific Services of the DWAF. It is a computer programme developed specifically for DWAF to support decision-making and provide the necessary information needed to manage water resources, sources and monitoring in South

Africa. The system comprises of various core components, which include:

• Resource and source management

• Monitoring management

• Registration of samples and results

• Water network management

• Stakeholder list

• Extracting and reporting of results

• Web enablement

• E nvironmental Quest i onnaire

• F eature in management

• C omp l iance Manager

• L etter generation (DW AF, http : / / www-dwafpwv .

gov .

zalProjects )

4.1.2

T h e National Groundwater Quality Monitoring Project

The project started in 199 4 with the monitoring of 376 sites to ascertain the i n flue nce of rainf a ll o n grolIDdwater quality and to determine the grolIDdwater quality on a nat io n al scale .

The mon i t oring points for the project are as shown i n Fig 3 below .

The monito ring points are b eing sampled twice a y ear , that is before and after the rainfall season (O ct o b er and

Apri l res p ectively) .

The samples are usually analysed by the laboratories at the IWQ S and the d ata is forwarded onto the WMS .

4.2

THE DETERMINATION OF THE FLUORIDE ION CONCENTRAnON

DISTRIBUTION IN GROUNDWATER

Using the extraction and reporting core component of the WMS, 44 886 groundwater analyses for fluoride were extracted and downloaded from the database. The set of data was checked for obvious errors. These were eliminated. This resulted in a data set comprising of

36046-groundwater analyses for the fluoride ion concentration. This data set was used to determine the overall fluoride ion distribution in groundwater between 1985-2000 in South

Africa Areas with fluoride ion concentrations lower or higher than the recommended guidelines and standards for fluoride in drinking water were also delineated. The highest fluoride ion concentrations recorded in each primary drainage region during the study period was also identified. The analysis with a spatial component was done using a Geographical

Information System (GIS) software package, ARC/INFO. Lithological boundaries were digitised from the 1:250000 scale geological map of South Africa The SABS maximum standard limit of 1,5 mg/t for fluoride in drinking water was adopted as one of the upper intervals for protection against dental fluorosis. Since fluoride levels in drinking water required to prevent tooth decay and dental fluorosis have been reported as ranging from 0,5 to 1,0 mg/t (WHO, 1994~ Du Plessis, 1995), the minimum beneficial limit used for this study is hence estimated at 0,5

mglt.

The rest of the ranges were estimated on DWAF guidelines for drinking water (DWAF, 1996). The optimum range for good dental health, according to most guidelines and standards for drinking water (WHO, 1984~WHO, 1994~

DWAF, 1996~SABS, 2001) is 0,7-1,Omg/t F-. These values have been used to represent the three beneficial intervals~

> 0,5 <=0,7

>0,7<=1,0

> 1,0 <= 1,5

Intervals in which dental health effects have been confirmed by research were used in plotting the data;

0<= 0,5

>1,5 <= 4,0

>4,0 <= 8,0

>8,0 effect of low fluoride ion concentration on dental health

Effect of excess fluoride

Effect of excess fluoride

Effect of excess fluoride

The details of these guidelines and standards are tabulated in Chapter Three. The spatial distribution of the data was overlain on Vegter 's lithostratigraphy in order to assess the role of surface geology in the occurrence and distribution of fluoride in groundwater.

4.3

THE DETERMINATION OF THE CURRENT STATUS OF FLUORIDE

LEVELS IN GROUNDWATER

4.3.1 Introduction

One of the important tools in Water Quality Assessment is the assessment of the current status or condition of the parameter or constituent of concern. This is usually a measure of the current condition (most recent 3-5 years) at a station or source compared to a benchmark value or data In this study, the values for the fluoride ion concentrations between 1996 and

2000 were used to assess the current status of fluoride ion concentration levels in some national groundwater sources. The data set used was obtained from the data used in section

4.2 above. The values in guidelines (DWAF, 1996; WRC, 1998) and standards (SABS,

2001) were used as a benchmark. The purpose of this was to determine the fitness for use of the groundwater for dOIrestic use and as criteria to characterise the quality of water in the individual groundwater sources based on the fluoride ion concentration observed.

The data set was assessed using the comparison of the observed fluoride ion concentration values and those required for human health as indicated in the various standards and guidelines tabulated in Chapter 3 of this dissertation. The data set between 1996-2000 comprised of 14 509-fluoride samples, collected from the various groundwater sources. This included boreholes and springs. A statistical package, STATISTICA, which calculated a fluoride median value for each unique groundwater source was used to process the data

This resulted in a summarised data set comprising of 6042 values.

Two approaches were used in assessing the data. These were the frequency and spatial distribution The data was plotted on maps to indicate the current distribution of fluoride ion concentration levels in South African groundwater sources and a histogram was constructed to indicate the frequency of the occurrence of these levels. The identified sources were characterised and classified accordingly.

45

The results from these exercises were compared with the dental fluorosis results and areas of concern identified. Some of these areas were physically labelled on the maps and linked to other results for better clarification of observations made especially those sources containing fluoride ion concentrations higher than the threshold for chronic poisoning. The use of such sources for drinking water purposes could lead to severe tooth damage and skeletal fluorosis.

Three adequately monitored boreholes were selected to study the interactions of the fluoride ion with other water quality parameters. Three of the boreholes were selected in the following order: good groundwater quality, and moderately higher fluoride concentrations than the recommended limits, and one having high fluoride ion concentrations. Correlation studies were carried out for these parameters. The main aim was to determine the role and contribution of parameters such as total alkalinity, silicates, phosphate, pH, Hardness

(Mg+Ca), Na, and electrical conductivity (EC). Pearson product moment correlation, from

STATISTICA was used for this study.

4.4

THE DETERMINATION OF TRENDS IN CHANGES OF FLUORIDE ION

CONCENTRATIONS IN GROUNDWATER

The data points described in

4.3

above were processed further in order to select those sites, which were monitored regularly during the selected assessment period. It was observed that for some monitoring points, monitoring was done only in a single year or two. For others monitoring did not start until 1997. The remaining data set was found suitable for the performance of a short-term trend analysis but a provisional attempt indicated that it would not be feasible to carry out the exercise given the following reasons.

• Changes in groundwater quality parameters are generally slow given its nature and hence trends may not be apparent in the water quality data for several years.

• Many factors such as, groundwater contamination from different sources, seasonal cycles, precipitation and natural availability of fluoride might affect the measured and observed water quality. As a consequence, it often takes many years of regular water quality data collection to statistically detect a trend, which usually manifests in small, gradual changes. Ultimately, if ever a trend is identified, additional scientific assessment is often essential to understand the implications of the trends and identifY corrective actions.

46

An independent data set was necessary for this study. This was used to determine the impact of consuming or drinking water with high fluoride ion concentrations levels on dental health. The areas of potential risk could be estimated from the various maps.

For this reason the results from the assessment of1his data set were compared with the water quality results in terms of fluoride ion concentration levels. At the time of writing this dissertation, the National Department of Health (NDOH) conducted a national survey on dental fluorosis. School children were examined in all the nine provinces of the country. Representatives from the Department of Health did the examinations. Symptoms of chronic dental fluorosis or mottled teeth were also looked for during the dental examinations. Detailed particulars about the degree of mottling, as well as the area where these children were born and had lived in up to the age of 12 years were carefully recorded. All cases of mottling were classified according to

Dean,

1939

(Table

12 below). The data for this survey is currently housed at Statistics

South Africa (SSA). Access to the data is arranged through the Department of Health.

The data received from the Department of Health was plotted after calculating total dental fluorosis morbidity for each area. The method for calculating the total % morbidity of dental fluorosis was adopted from Wang, et al

1999.

A comparison of the results obtained from the occurrence of the fluoride ion concentrations in groundwater and the incidences of dental fluorosis in selected provinces was done.

Degree of fluorosis

Normal

Questionable

Very Mild

Mild

Moderate

Severe

Description and rating

0

0,5

A few white flecks to occasional white spots

1,0

Less than 25% of the tooth's surfaces covered by white opaque, paper-white areas.

2,0

Fifty percent of the tooth ' s surfaces covered by White opaque areas.

3,0 nearly all the tooth's surfaces involved in minute pitting and brown staining.

4,0

Smoky white appearance of all the teeth

Pitting frequent and on all tooth ' s surfaces

Hypoplasia, chipping and large brown stains that vary from chocolate brown to black.

Analysis of data with a spatial component was carried out using the Geographical

Information System (GIS) software package ARCIINFO. Lithological boundaries were obtained from the maps produced by Vegter (Vegter, 1995). In order to classify groundwater data in terms of surface geology, various geology maps were used. This was the most accurate and available method for performing the classification since a large number of data points were used. To produce various maps the fluoride ion concentrations in groundwater samples were classified into 7 groups: 0-0,5; 0,5-0,7;

0,7-1,0; 1,0-1,5; 1,5-4,0; 4,0-8,0 and >8.

The fluoride ion-selective electrode method was used to measure fluoride ion concentration in solution. The use of the Total Ionic Strength Adjustment Buffer

(TISAB) brings all solutions approximately to the same ionic strength and to a pH of approximately 5,5. It is also intended to break: up aluminium fluoride and related complexes that might otherwise reduce the fluoride activity (Hammer, 1986).

Cyclohexene diamine tetraacetic acid (CDTA) is used as an effective de-complexing agent.

In this chapter the results obtained using the research procedures described in Chapter 4 are presented and discussed in the following sections:

• Occurrence and distribution of fluoride ion concentrations in groundwater; 1985-2000

• The highest fluoride ion concentrations recorded in South Africa between 1985-2000;

• The status of fluoride ion concentration levels in South African groundwater, 1996-2000

• The occurrence of dental fluorosis in selected provinces and

• The distribution of percentage morbidity of dental fluorosis in selected provinces

• Dental fluorosis and drinking water quality

• Factors that contribute to the occurrence of different fluoride ion concentration levels in groundwater

(as identified in this study);

5.2

OCCURRENCE AND DISTRIBUTION OF THE FLUORIDE ION

CONCENTRATION IN GROUNDWATER, 1985-2000

5.2.1

Spatial distribution offtuoride ion concentrations in groundwater

The overall picture on the distribution of fluoride ion concentrations in groundwater and the potential exposure to fluoride that may exist from those groundwater sources is shown in Map A.

Maps A1-AJ show the distribution of those sources with the fluoride ion concentrations beyond the safe recommended limits for drinking water. Map A4 shows the distribution of sources with fluoride ion concentrations between 0 and 0,5 mg/f.

Such areas are generally considered as deficient in fluoride where these levels persist for a long time. If such a situation persists, then the people using the water for drinking purposes will be susceptible to dental caries problems and they might be a need for fluoride supplementation in the form of fluoridation.

However caution must be exercised as the same sources might exhibit higher concentrations at any time given the climatic conditions, type of aquifer, and type of geology among other factors. The values given in this document do not necessarily reflect the actual values that may exist at all times in a given groundwater source, nor do they reflect the actual or constant exposure to fluoride of the population of South Africa although in exceptional cases that can be true.

In all the maps a comparison of the fluoride levels and their distribution compared to the SABS standards for drinking water and DW AF guidelines as described in Chapter 3 was made. The data is plotted on the geology map to allow for a comparison between the occurrence of the fluorides and the surface geology. It is envisaged that this comparison would give an insight into the role of geology in the occurrence of fluoride ion concentration levels in groundwater.

Seven intervals commensurate with the guidelines and drinking water standards were selected for plotting the data.

The maps are separated to facilitate the delineation of those areas deficient in fluoride and those with high potential for dental fluorosis. (Maps AI-A4). The maximum allowable limit for fluoride ion concentration in drinking water is 1,5 mg/f. According to the SABS, this water can be consumed for a maximum period of one year in order to avoid the occurrence of dental fluorosis.

Map Al shows the distribution of sites with fluoride ion concentration of 1,5-4,0 mg/f. It should be noted that prolonged consumption of this water could result in severe dental fluorosis or skeletal fluorosis in some instances.

From the maps, it is evident that groundwater is generally of good quality but certain areas experience problems of high fluoride ion concentrations. Maps A and A4 support this. A number of cases with higher fluoride ion concentrations in groundwater than the recommended limits for drinking water occur in the Limpopo, Northern Cape, Eastern Cape, KwaZulu Natal and North-

West provinces. The Northern Cape is the most affected province. This is evident from Maps AI-

AJ. Of more concern are those cases with fluoride ion concentrations greater than 8mg/ f. The

Limpopo, Northern Cape, KwaZulu Natal and Eastern Cape provinces have a number of such cases (Map AJ). In other provinces a few cases or individual sources are observed. These include

Mpumalanga and Free State. The consumption of these levels of fluoride can lead to serious health problems. Most of these areas have been found to be endemic to fluorosis. (Map C, CI and C2).

51

It is evident from the maps that most of the groundwater sources have fluoride concentrations above the maximum limit of 1,5 mg/R..recommended by SABS and DWAF for drinking water. Of more concern is the number of boreholes with concentrations above the threshold for chronic fluoride poisoning, which might lead to severe dental fluorosis and crippling skeletal fluorosis.

(Maps A2 and A3).

In conclusion, the results show a country in which in most provinces groundwater sources have fluoride ion concentrations higher than those recommended for fluoride in drinking water.

If the results shown in Map A4 are considered a true reflection of the fluoride levels in drinking water actually consumed by the population then no area is in need of fluoridation to within 0,5-1,0 mg/R..

as recommended by the World Health Organisation (WHO, 1994) or 0,7-1,0 mg/£ (DWAF, 1996,

SABS,2001).

If the local people are using all the examined sites for drinking purposes, then a large number of the groundwater sources of South Africa are in need of partial de-fluoridation.

This will be true for most of the groundwater sources in the Limpopo, North-West, Northern Cape,

Western Cape and KwaZulu Natal Provinces.

Map A4 delineates those areas with fluoride ion concentrations lower than the recommended limits for dental health, <0,5 mg/R..(WHO, 1994). However, this water is considered ideal according to the South African Water Quality Guidelines (DW AF, 1996, WRC, 1998) since the concentrations are <0,7 mg/£. This sets a contradiction between the requirements as set by the Department of

Health for the fluoridation of water supplies once the fluoride ion concentration is <0,7 mg/R..and

the DW AF guideline for fluoride. The DW AF1s TWQR for fluoride in drinking water, which is the concentration in water necessary to meet the requirements for health tooth structure as a function of daily water intake and varying with annual daily air temperature is between 0-1,0

mg/R.

According to the guidelines the consumption of this water will have no health effects.

This water is classified as Class 0 and ideal for drinking according to the SABS specifications (SABS, 2001).

Given these conditions and the pattern of distribution of these concentration levels observed in

Map A4, it will be safe to conclude that groundwater is generally of good quality.

It should h owever be no t ed that if a population is subjected to very low fluoride i o n con centrations , de ntal ca ri es might be a problem .

Considering, the fact that fluoride levels vary f rom ti me to time given the f actors that contribute to its occurrence in a locality, it would be a ris k to reco mmend that there be f l uo r i dation ac r oss the country or for specific boreholes .

A rather safe mean s will be to find oth er means of supplementing fluoride such as fluoride tablets to child ren o r administer fluoridat e d t oo t hpaste.

5.2.2

T h e highest fluoride ion concentrations recorded in South Africa betw een 1985- 2000

The high e st fluoride ion concentrations recorded for the various sites across the c ount ry and i n the individu al primary drainage regions are given in Table 14 below .

The fluoride i on co ncentrations

PDR

All

A

J

K

L

M

F

G

H

B

C

D

R

N

P

Q

S

T

U

V

W

X

Table 14 : Highest fluoride ion concentrations recorded for the State and Individua l Pri mary

Drainag e Regions(pDRs) as reflected by the WMS data (1985-2000)

No .

Of analyses

36046

7409

3115

6737

7427

993

564

2183

284

840

124

283

172

421

1357

958

188

620

499

968

332

457

Place

Elandsfontein 321

Zoutpan, North West

Doornkloof, Eastern Cape

Rissiville, Gauteng

Marlborough, Northern Cape

Richmond Hill, Eastern Cape

Bitterfontein, Western Cape

Mitchellsplein, Western Cape

Pietersfontein, Western Cape

Fonteintiies, Western Cape

Farm 138, Western Cape

Doornkloof, Eastern Cape

The Apex, Eastern Cape

Grasrand, Eastern Cape

Dagbreek, Eastern Cape

Klippe Drift, Eastern Cape

Kurnngqanga, Eastern Cape

Roodeberg, KwaZulu Natal

KwaZulu, KwaZulu Natal

Golokodo, KwaZulu Natal

Machibini, KwaZulu Natal

Kasteel, Limpopo

F ion concentrat ion , Yea r recorded

42,05 (19 94)

40,77(19 95)

39,63 (19 88)

38,3 (19 85)

34,64(19 95)

2,75 (1 9 90)

10,37 (19 97)

14,78( 19 98)

10,71 19 97)

15,93 19 89)

6,98 (19 90)

39,63 ( 1 9 88)

3,92 (19 90)

19,52 1 988)

10,28 1 990)

16,83 (1 985)

6,21 (19 90)

12,3 (19 97)

7,14 (19 91)

15,72 (1 992)

23,56 (1 992)

40,49 (1 994)

From t he above, it is observed that cases of high fluoride ion concentration in gr ound water occur in almo s t all provinces and primary drainage regions although some are more a ffecte d than others .

5.3

THE STATUS OF FLUORIDE LEVELS IN GROUNDWATER AS REFLECTED

BY GROUNDWATER SOURCES STUDIED BETWEEN 1996-2000

In order to study the status of fluoride concentrations in various groundwater sources across the country between 1996-2000, two approaches were used namely spatial distribution using

ARCIINFO, a GIS software and the frequency distribution. The 6042 data points extracted from the WMS for the period 1996-2000 were plotted as shown in Map B (details in Chapter 4). To simplify the interpretation of the results observed and account for the various levels of fluoride in groundwater, the data was plotted on Vegter's lithostratigraphy (Vegter, 1993). This allows the assessment of the effect of surface geology in the occurrence and distribution of fluorides.

5.3.1

Spatial distribution

The current status of fluoride ion distribution in South African groundwater is shown in map B.

The map shows that the problems of high fluoride ion concentrations are currently being experienced in the Limpopo and Northern Cape provinces. A few cases were recorded in other parts of the country. Other provinces experience the problem in a limited number of groundwater sources. It should be noted however that all levels and ranges of fluoride occur to a certain degree in almost all provinces. The Map B 1 shows a comparison between the distribution of fluoride using the data from the current study and that done by Simonic in 2001 (Simonic,2001).

It is evident from the two maps that although groundwater is general of good quality there are serious problems of high fluoride levels, > 1,5 occurring in the groundwater sources of the

Limpopo, North-West and the Northern Cape provinces. In other provinces such cases are observed as isolated incidents. The current situation of the fluoride distribution in the country is such that no clear cut demarcation can be made of the areas deficient in fluoride since some of those areas have sources in which the fluoride ion concentration is higher than the recommended limits for drinking water. Many groundwater sources in the Limpopo, North-West, Northern Cape,

Western Cape and KwaZulu Natal provinces show a need for partial de-fluoridation. This must receive serious consideration if the water from those sources is currently being used for drinking

5.3.2

F r equ e ncy Analysis

The distri b ution of the f luor i de ion concentrations calculated for the 6042 station s are shown in a bar chart.

(Fig 4). From the chart it is eviden t that the population is highly skew ed t owards high fluoride co nc e ntrations .

Alt h ough the tail of the graph is i r regular, there is an inc rease d frequency of occur re nce of groundwater sources with fluoride ion concentrations in the rang e> 1 , 5-4 , 0

mgl R..

This is o f con c ern , as the health impacts on teeth can become a problem at these le vels .

= e

C

C )

III

CP

~

= o

•.

III

.

"C

I

'0

•.

.

.

!

=

E c

1

?f

t

0-0.5

>0 .

5>0.7>1 .

0 >1 .

5>4.0>8.0

0 .

7 1.0

1 .

5 4.0

8 .

0

Fluorid e ion concentration ranges, mg/l

% bo

reh oles

I

Of the 60 42 groundwater sou r ces studied ;

3693 (6 1, 1%) had fluoride ion concentrations less or equal to 0,5

mgl R.

.

622 (10 , 2% ) had fluoride ion concentrations between 0 , 5-0 , 7

mgl R.

.

This bri n gs t o 4315 (71,3%) groundwater sources with concentrations of fluorid e

<

0 , 7

mgl R..

This is the current ideal standard according to SABS specifications selected based on the threshold for dental caries risk. Of all the groundwater sources assessed, 74,86% were within the TWQR of

0-I,Omg/f

F recommended by the DWAF for drinking water (DWAF, 1996). It can be concluded that generally, the water in South African groundwater sources is of good quality. From the 6042 groundwater sources studied, 456 (7,5%) had fluoride ion concentrations higher than 1,0

mg/f

but less than 1,5

mg/f

placing the water from these sources in the Class IT category as recommended by SABS. The people drinking this water can only use it for a maximum period of one year. At this level, slight mottling of teeth may occur in sensitive individuals (DWAF, 1996; WRC, 1998).

Currently this is the maximum allowable limit for fluoride in drinking water.

From the histogram it can be observed that there is an increase in the number of sources with fluoride ion concentration levels higher than 1,5

mg/f

but equal or less than 4,0

mg/f.

This is within the threshold limit for chronic effects of fluoride exposure.

Both dental fluorosis and skeletal fluorosis may be detected if the water is consumed for a long period since childhood.

Only 117 groundwater sources had fluoride ion concentrations between 4,0 and 8,0

mg/i!.

Exposure to this water for drinking purposes will cause severe tooth damage and pronounced skeletal fluorosis if the candidates are exposure is for a long time (DWAF, 1996). Crippling skeletal fluorosis is also likely to appear. Of the studied groundwater sources, 19 (0,30%) had fluoride ion concentrations higher than 8,0 mg/

f.

It should be noted however that it is not the quantity of the groundwater sources that is important but the level of fluoride ion concentrations of the water, the impact on health and the population at risk due to the consumption of such water.

It should be noted that there is a contradiction in what is understood as the safe limit for fluoride in drinking water. While the SABS, the DWAF and WHO agree on the safe limit of< 0,7

mg/f

for the fluoride ion concentration as ideal for health teeth, the DOH legislation enforces that the fluoride ion concentration should be equal to 0,7 mg/

f.

According to the WHO a concentration of

0,5 mg/l is ideal for dental health (WHO, 1994) hence concentrations

<0,5mg/f

might cause dental caries if the water is consumed for a long time.

Fluoride ion concentrations

<

O,5mg/£ fall within the safe and ideal range according to the SABS and the DW AF while at these levels the DOH recommends the fluoridation of water supplies.

Considering the fact that the majority of the population does not yet have access to piped water and it is difficult to fluoridate borehole water, water from natural springs and wells, it will be appropriate to recommend that alternative methods of fluoridation such as fluoridated vitamins and minerals, fluoride tablets, fluoridated salt, fluoride-containing mouth rinses and fluoride containing toothpaste.

Professional supervision and public awareness campaigns need to accompany this.

Research into these alternative methods need also to be carried out.

The results of the general investigations of fluorosis obtained by analyzing the data from the DOH are as presented in Tables 16, 17, 18 and 19 .

The criteria used to interpret the results are as presented in Table 15. adopted from Wang,

et aI .

,

1999. The information on the dependency of communities on groundwater for use as drinking water is presented in Table 20 .

This information was obtained in order to confirm the link between high fluoride levels in groundwater , the consumption of this fluoride contaminated water and the occurrence of dental fluorosis in the same areas .

It should be noted that in a province where the communities depend largely on groundwater for drinking water purposes like the North-West Province, the morbidity of dental fluorosis is high.

Class

Dental Fluorosis symptoms

A-Normal No apparent abnormality

B-Slight (Questionable, Very mild, Mild) Yellowish teeth with slight erosion

C-Heavy (Moderate and Severe) Extended erosion or mottling or heavy damage to teeth.

Table 16 : Dental Fluorosis by level of Severity in the Free State (FS) Province

(Age group 12)

Name of

Place

FS-RegionA

ausA ausB ausc

B+C

%

Morbidity

34.5% 62.2%

2 .

5%

64.7% 64.70

62.3% 1.3% 63 .

6% 63.60

FS-RegionB 35.6%

FS-Region C

66.1%

FS-RegionD

FS-RegionE

FS-RegionF

66.1%

66.5%

42 .

4%

29 .

1%

31 .

5%

29.7%

51 .

4%

3 .

0%

1.7%

1 .

7%

4.8%

32.1%

33.2%

31 .

4%

56 .

2%

32.10

33.20

31 .

40

56.20

Table 17 : Dental Fluorosis by level of Severity in the Western Cape (WC) Province

(Age group 12)

Name of Place

Class A CIassB CIassC

B+C

%Morbidity

WC-Boland Overberg Region 86 .

0%

WC-Metro 54.5%

WC- South Cape -Karoo

WC- West-Coast

46.5%

69 .

4%

13.3%

42.1%

39

26

.

.

2%

5%

0%

2.2%

10

1 .

.

7%

4%

13

44

48

27

.

.

.

.

3%

3%

7%

9%

13.30

44.30

48

27

.

.

70

90

Table 18 : Dental Fluorosis by level of Severity in the North-West (NW) Province

(Age group 12)

Name of Place

NW-Br i ts

Class A

32.8%

ClassB

61 .

7%

CIassC

5.6%

B+C

67 .

3% o/oMorbidity

67.30

NW -Delareyville

NW -Mafikeng

NW-Mogwase

NW -Morete1e

NW -Potchefstroom

NW -Rustenburg

NW-Ganyesa

NW-Klerksdorp

NW-Kuruman

NW -L i chtenburg

NW -Schweizer

NW-Taung

NW -Ventersdorp

NW-Vryburg

NW-Zeerust

80 .

7%

97.7%

6 .

7%

25.6%

82 .

8%

81 .

9%

26.7%

82 .

7%

42.3%

86.6%

71 .

7%

31 .

6%

73

49

47 .

.

.

3%

7%

8%

5.8%

0 .

9%

93 .

4%%

35

17 .

2%

5 .

.

3%

8%

54 .

9%

13

57 .

.

5%

7%

12 .

8%

26

60 .

.

6%

7%

20%

43 .

6%

48 .

6%

0%

0%

0%

39

0%

0%

18

1

6 .

.

.

.

1%

4%

8%

0%

0 .

5%

1 .

6%

7.1%

7%

6.7%

2.1%

5 .

0 .

9%

93 .

4%

74

17

57

13

8%

.

.

.

.

4%

2%

5 .

8%

73 .

3%

15 .

3%

7%

3%

28.2%

67

26

.

.

8%

7%

50.3%

50 .

7%

5.80

0.90

93.40

74.40

17.20

5.80

73.30

15.30

57.70

13.30

28.20

67.80

26.70

50.30

50 .

70

NW -Wolmaranstad

61 .

1%

33 .

4%

5.6%

39% 39.00

Table 19 : Dental Fluorosis by level of Severity in the KwaZulu Natal (KZN) Province

(Age group 12)

Name of Place

Durban

Jozini

Ladysmith

Newcastle

Pietermaritzburg

Port Shepstone

Ulundi

Class A

ClassB

79.6% 10 .

9%

50.7%

41 .

7%

86 .

4%

34 .

7%

50 .

8%

72 .

2%

77.1%

57.8%

7.6%

23.1%

17 .

5%

38 .

2%

Class C B+C

1 .

4% 12 .

3%

2.5%

7.0%

3 .

3%

2

1

.

.

1%

8%

1 .

9%

37.2%

57 .

8%

10 .

9%

25.2%

19 .

3%

40.10% o/oMorbidity

12.30

37.20

57.80

10.90

25.20

19.30

40.10

Table 20 : Dependency of communities on groundwater for domestic purposes as provided by the

DW AF 's Water Services Directorate.

Province

Source

Groundwater

Surface Water

Conmned SouR:e

None

Unknown

Total

Supply Potential

Poor

Low

Moderate

High

VeryHi~

Total communities

Total population

North-West

Communities

People

1063 1411707

221 2099461

-

-

13

1297

160

207

341

266

323

1297

108593

-

-

3619761

48733

330061

1220101

1620011

400855

3619761

3619761

Free State

Communities

People

72 122161

149

30

3097252

139452

251

-

24

99

124

4

251

-

3340865

83380

905 112

2271450

80923

3340865

3340865

-

-

KwaZulu Natal

Communities

People

807

75

2416721

212698

48

149685

1563

2493

5624304

8403408

996

558

939

2493

-

-

2590 125

1529404

4283879

8403408

8403408

5.4.1

Morbidity of dental Ruorosis and drinking water quality

The distribution of dental fluorosis in selected provinces is shown in Maps C, Cl, C2 and C3. Map

C is based on the data from tables 17, 18 and 19. The maps Cl, C2 and C3 show the spatial distribution of the current

% dental morbidity of fluorosis morbidity for the Western Cape, North-

West and KwaZulu Natal provinces. The fluoride data is overlain on each provincial map in order to correlate the level of the morbidity of dental fluorosis and fluoride levels in drinking water. It should be noted that there exist differences in the morbidity of fluorosis among the investigated provinces. It was difficult to present the Free State province data using the same format as the dental fluorosis data was reported in regions whose digital data was not present at the time of writing this dissertation.

From the results, a percentage morbidity of dental fluorosis as high as 97% was recorded in the

North-West province. In comparing the distribution of the % morbidity of fluorosis with that of fluoride concentration in groundwater sources (Cl to C3), it is apparent that high morbidity of fluorosis has happened in areas where fluoride concentrations are extremely high and in most cases exceeding the limits for drinking water. In towns and villages where the water quality problem in terms of fluoride ion concentration is less serious, the morbidity of fluorosis is comparatively low.

It is evident from the maps that the occurrence of dental fluorosis and its morbidity correspond to the levels of fluoride ion concentrations in drinking water. The size of the shaded part

(% morbidity of dental fluorosis) in each area gives the idea of the general quality of drinking water consumed by the examined subjects.

The following tables show a comparison of worst-case fluoride ion concentrations and the percentage morbidity of dental fluorosis recorded in each province.

Table 21: Incidences of fluoride ion concentrations in groundwater sources of the North-West province and the percentage morbidity of dental fluorosis

Area

Vryburg 1

Ganyesa

Kudumane

Mogwase

Vryburg 2

Taung

Schweizer Reneke

Delareyville

Wolmaransstad

Klerksdorp

Litchtenburg

Ventersdorp

Potchefstroom

Marico

Rustenburg

Mankwe

Bafokeng

Brits

Moretele 1

> 1,0

>4,0

<0,5

>4,0

< 1,5

>4,0

> 8,0

> 0,5

>4,0

>4,0

> 1,0

> 0,7

> 1,0

> 1,0

Worst case

Fconc, Worst Case F Percentage morbidity of

mg/i

*(This study) conc,

mg/i

dental fluorosis

>8,0

-

Rawhani,1986

46

>8,0 73,3

>1,0

> 8,0

> 8,0

-

-

25,8

-

60,0

93,4

50,3

-

-

8,8

-

-

-

-

-

-

-

-

-

1,1

9,0

17,2

50,0

5,80

- 98,0

-6,0

67,3

74,40

67,8

28,2

5,80

39,0

15,30

13,3

26,7

From the above table it is evident that low fluoride ion concentrations in drinking water result in low levels of morbidity of dental fluorosis while higher concentrations correspond with high percentage morbidity of dental fluorosis. It can be concluded therefore that the effect of fluoride on dental health depends on daily intake of fluoride and drinking water is the main source. Another conclusion from this study is that in most cases severe dental fluorosis did not occur unless the fluoride ion concentration in the groundwater sources was in excess of 1,0 mg!£ and the degree and severity of mottling increased as the fluoride level increased. It should however be noted that the consumption of dietary fluoride and hence the amount of fluoride consumed will depend on the climate of a place. For example, in hot climate the rate of water consumption per day is higher than during winter days. This is because of the temperature dependence of the daily water consumption.

In South Africa, the recommended limit of< 0,7 mg!£ and a maximum allowable limit of 1,5 mg!£ is enforced.

As seen from the above table high fluoride sources are scattered and widely spread across the province. Of great concern are those areas with fluoride ion concentrations higher than 8 mg!£ especially in Ganyesa. In 1986, it was confirmed that in this area, alternative sources to use of groundwater were not easily found (Rawhani, 1986). Although the subject of low fluoride ion concentrations was touched in this study, no field investigations on dental caries were conducted.

Since the results show no particular areas of concern, fluoridation of water sources might not be a priority for the country at the moment. However it can be recommended that for those areas that are confirmed to be deficient in fluoride, fluoridation studies be carried out on a pilot scale. Since the impact is only visible after a long time and is irreversible proper consultation with the affected parties should be made to accommodate and avoid problems at all levels.

It is evident from Map B that the coverage of water quality data from other areas is poor. It is possible that after the publishing of the research results conducted in the former Bophuthatswana, the use of affected boreholes were discontinued (Rawhani, 1986; Pelpoa,

et aI,

1992; McCaffrey,

1993). The other possibility would be that the data is still in the hands of individuals and it was not passed onto the DW AF databases.

However, it can be concluded from the results of the current study that the occurrence of high fluoride ion concentrations in groundwater used for drinking purposes is accompanied by a high percentage morbidity of dental fluorosis. This varies from district to district and village to village.

This was also observed for other provinces (Tables 22 and 23)

Table 22: Incidences of fluoride ion concentrations in groundwater sources of the Western Cape province and the percentage morbidity of dental fluorosis.

Area

Western Cape District

Overberg Region) l(Boland -

Worst Case (F conc in mg/RI)

% morbidity of dental

(This study) fluorosis

>8

13,30

Western Cape Metro District 2

Western Cape District 6

Western Cape District 5

>8

>8

>1,5<= 4,0

44,90

48,70

27,90

In the Western Cape Metro there are a number of groundwater sources with the fluoride ion concentration between 1,5 and 4,0

mg/R.

Only one source had a concentration >8

mg/R.

However, the fact that the majority of sources have the concentrations between 1,5 and 4,0 is already a concern since in this range dental fluorosis becomes a problem. The same was observed and could be concluded about District 6.

Table 23: Incidences of fluoride ion concentrations in groundwater sources of the KwaZulu Natal province and the percentage morbidity of dental fluorosis.

Area

%

DlOlbidity of dental fluorosis

Jozini

New Castle

Ladysmith

Ulundi

Pietermaritzburg

Dmban

Port Shepstone

Worst Case (F cone in

(This study)

rnrJ

f)

<4,0

<1,5

>8

>8,0

<0,5

<1,5

<=4,0

37,20

10,90

57,80

40,10

25,20

12,30

19,30

From Map C, it is evident that the occurrence of high fluoride levels in some groundwater sources is a problem in the provinces studied but the degree of severity and the impact on dental health varies from province to province, district to district and village to village.

5.4.2 Distribution of potential risk areas

Maps CI-C3 were used for this exercise. Only areas for which dental fluorosis data was available during the time of this dissertation were used. These included KwaZulu Natal, North-West, Free

State and Western Cape Provinces. The maps show the level of dental fluorosis risk based on the percentage morbidity of dental fluorosis. Based on the DW AF and SABS guidelines and standards for drinking water, it has been decided in this study to classify the degrees of dental fluorosis risk as follows:

<0.7mg/f - No risk

0.7 - 1.5 mg/f - Low risk

>1.5 - 3.5 mg/f- Medium risk

>3.5mg/f High risk

The above classification resulted in the following tabulated information;

Table 24: Relationship between %dental fluorosis morbidity and drinking water fluoride levels in

KwaZulu Natal province.

%Dental fluorosis Classification of risk AREA

Durban

Jozini

Ladysmith

Newcastle

Pietennaritzburg

Ulundi

Port Shepstone

F cone range,

mgll

1,0-1,5

1,5-4,0

1,5-4,0

0,7-1,5

1,0-1,5

1,0-1,5

1,0-4,0

12,30

37,20

57,80

10,90

25,20

19,30

40,10

Low risk

High risk

High risk

Low risk

Low risk

Low risk

High risk

Table 25: Relationship between %dental fluorosis morbidity and drinking water fluoride levels in the North-West province.

Area

Brits

De1areyville

Mafikeng

Mogwase

Morete1e

Potchefstroom

Rustenburg

Ganyesa

Klerksdorp

Kuruman

Lichtenburg

Schweizer

Taung

Ventersdorp

Vryburg

Zeerust

Wo1maranstad

%dental fluorosis

67,30

5,80

0,90

93,40

74,40

17,20

5,80

73,30

15,30

57,70

13,30

28,20

67,80

26,7

50,30

50,70

39,0

F range,

0,00-9,86

0,66-1,22

0.7-1,0

>8,0

>8,0

1,0-1,5

0,47

>8,0

1,0-1,5

1,0-8,0

1,0-1,5

1,5-4,0

4,0-8,0

>1,5

4,0-8,0

4,59-9,69

1,5-4,0

mgll

Main source for drinking water

No risk to High risk

Low risk

Low risk

High risk

High risk

Low risk

No risk

High risk

Low risk

High risk

Low risk

Medium to High risk

High risk

Medium risk

High risk

High risk

Medium to High risk

From the above observations it can be concluded that the degree of mottling (dental fluorosis) depends on the amount of fluoride ingested. Although this is observed from the results accurate correlation of the degree of mottling of the teeth with the amount of fluoride in the drinking water in South Africa is difficult owing to variations of fluoride levels in groundwater and the dependency of this phenomena on the various factors which include among others the effect of climate. The other factor, which might contribute to the above results, is the injection of fluorides into the hydrological cycle through various industrial activities. Socio-economic factors need also to be considered as a lot of people move from the rural areas into urban areas in search for jobs.

5.4.3

Risk levels and optimum fluoride concentrations in drinking water

The Optimum fluoride content of drinking water means a fluoride concentration of not more than

0.7 mg/f in a public water supply (Anon. 1998). It is however known that the optimum fluoride dosage is dependent on the annual average maximum daily air temperature (Hammer, 1986,

Grobler and Dreyer, 1988). There is uncertainty as to the precise concentration of F in drinking water that is optimal for human health, as these will vary from country to country. Table 25 below, shows that the fluoride ion concentration limits for drinking water suggested by various international bodies vary considerably. It is apparent that the upper limit for avoiding widespread dental fluorosis is approximately 2,0 mg/f, although this value is lowered in tropical climates because of increased water ingestion. Fluoride ion concentration calculated for South Africa using the data obtained from the South African Weather Bureau is presented in Appendix C. The optimum fluoride content from this study was approximately 0,8 mg/R..It has been noted that since water ingestion is proportional to air temperature, the optimal F concentration in groundwater used for drinking purposes should be dependant on the mean maximum temperatures experienced in any area, (WRC, 2001). The empirical equation for optimal F concentration calculations is as shown in Chapter 3.

Proposed effects, mgll F in drinking water

BODY/ORGANIZATION

WHO, 1984

US,EPA

TANZANIA

ARGENTINA, URBAN

Brouwer,

et

RURAL

a/.,

1988,

TROPICS >0,6

>1,5

-

>2,0

>1,5

>2,2

Objectionable dental fluorosis Skeletal fluorosis

3,0-6,0

--

-

>8,0

-

-

Crippling skeletal fluorosis

>10

>4,0

-

-

5.5

FACTORS THAT EFFECT THE DISTRIBUTION OF FLUORIDE IN

GROUNDWATER

5.5.1

Introduction

In a country such as South Africa with its extreme climatic variations between very wet and very dry seasons one might anticipate a variation in the fluoride content of the groundwater. If this were true it would be important not only to know the fluoride levels in groundwater used for drinking purposes but also the range of variation. The variation in fluoride content is considered to be the result of the interplay of a number of factors of which the more important are those discussed in detail in Chapter 2 of this dissertation. It is important to understand these factors in order to be able to properly manage fluoride in water resources. It was observed during this study that the fluoride levels in groundwater sources varied from one season to another and from one month to another. It was observed that in other sources the changes were minimal.

This raised the interest of determining some of the factors that could contribute to this behaviour. These are the following;

• The effect of climate, e.g. rainfall

• The role of other water quality parameters,

• The role of surface geology

5.5.2

The role of climate

A few boreholes were selected for this exercise. This included boreholes that were frequently monitored between 1994 and 2000. Three cases were selected, those with good quality drinking water, that is between 0-0,1; those with fluoride ion concentrations between 1,0 and 1,5 mg/£ and those sites with fluoride ion concentrations greater than 4 mg/ £ and from which the consumption of their water for a long time presents a high risk for dental fluorosis. The boreholes selected were monitored between April 1994 and December 2000. For most ofthese sources sampling was done twice a year, before the rain season (for example in April) and after the rains (in October). The results are as presented below. However variations with time were not assessed. The rest of the graphs are as shown in Appendix A. Since the period runs over 7 years, 14 seasons were identified.

Odd numbers represent the dry season while even numbers the wet season

69

::::

C)

E 1 .

5

.-

( , ) c:

1 o

( , ) u

.

Var i ations in F ion concemtrations 1994-2000 in selected monitoring sites

ZQMRSK1

DZQMRUE1

.ZQMSFB1

Varaitions in F ion concentrations in 1994-2000 in selected monitoring sites

1.

2

:::: 1

C)

E 0 .8

c:

.~ 0.

6

0 .

4

( , ) u .

0.

2 o

.

ZQMSM E1

DZQMSS M2

.ZQMST

B1

Variations i n F ion concentrations, 1 9 94-2000 in selected monitoring sites

· ZQMS

TR 1

DZQMS

TY 1

· ZQMS

UT 1

The resu lt s from the above graphs show the changes in fluoride concentration i n differ ent borehol es . While other boreholes show some variations, the borehole at ZQMSFB 1 sh ows variatio ns for the first 3 yea r s and insignificant variation over the remaining year s .

Th is cannot h o weve r b e assigned to the climate effect only.

Table 2 7 below shows such effect in three different sites .

Climatic influences affec t the fluoride concentr a tions in water considerably in areas with high levels of fluoride .

It is obser ved from the results th a t during dry months the fluoride content increases and during and a fter the rains, the content g oes down.

H owever, it is very difficult to generalize from the obse rvati ons since the pattern of va r iations changes from year to year in some cases. This is an indica t i on th at besides the climate, the r e are other factors that influence the level of fluoride ion conc entrations in ground wa ter .

Area

ZQMR.SKI

Borehole 1

ZQMR.UEI

ZQMSFBI

DS

-

Dry

Season

WS

-

Wet

Season

DS

Finmgll

1994

1,30

1,74

0,62

WS

F inmgll

1994

0,85

1,10

0,55

DS

F inmgll

1995

1,08

1,34

1,08

WS

Finmgll

1995

0,65

1,32

0,30

DS

Finmgll

1996

0,85

2,00

0,95

WS

F,mgIl

1996

0,70

1,35

0,31

The above observations show that during the dry months, the water evaporates from the main rocks and soils that contain fluorides. This contributes to an increase in concentration as the various geological forms withhold the fluoride ion. More important is the fact of low inflow into aquifers. As a result the fluoride content increases. During and after the rains, the F content decreases owing to dilution. However that is not always the case in some boreholes. The rains promote chemical weathering and leaching of various rocks rich in fluoride. The fluoride rich water might be carried down the direction of flow increasing the fluoride levels at the final basins in which the water ends. The nature of variations observed raised the need to look into other possible contributors such as the interactions of the fluoride ion with other water quality parameters and the role played by the geology of the area.

5.5.3.1

Introduction

Due to the pronounced electron affinity of the fluorine atom, fluorine interacts with almost every element. It readily reacts with calcium to form the relatively insoluble calcium fluoride. Where phosphate is present an even more insoluble apatite or hydroxyapatite forms. In this study,

Pearson's product- moment correlation was used to assess the nature of the associations.

This correlation assumes that the two variables are measured on at least two interval scales and it determines the extent to which values of the two parameters are "proportional" to each other. The correlations follow the following general expression:

Y

= m*F

+

C

Where, Y is the dependent variable, in this case any of the parameters interacting with the fluoride ion, m-is the slope of the proportionality line, C is the intercept on the Y-axis and F is the fluoride ion concentration.

Three sites were selected for this study, each with a different water composition.

The data for the major inorganic parameters was downloaded from the WMS and the correlation graphs are shown in Appendix B. The results are shown in Table 28 below.

The different associations between the fluoride ion and other parameters should be noted.

For this exercise parameters of interest to the fluoride chemistry in water were considered (details in Chapter 3). In this dissertation, however only correlations between the fluoride ion and Total Alkalinity (TAL), pH, Mg, Ca, Si, EC, and

P0

4

-P were studied. Pearson product moment correlation using STATISTICA was used to assess the interactions.

Correlations were considered significant at p

<

0,5. Any coefficient between -0,2 and +0,2 was considered insignificant.

Table 28: Pearson correlation coefficients between fluoride and other parameters measured in three different sites.

Parameter pH

Mg

Ca

Na

Si

Total Alkalinity

EC

P04-P

Borehole water ill

Borehole water at

Borehole water in

Steynberg, n = 13 TUGELA, n = 13

ZALEXBAY1, n=25

-0.5057

-0.4412

-0.2200

+0.5336

-0.1800

+0.5724

-0.4273

+0.2547

-0.3772

+0.5351

+0.1187

+0.6339

+0.6658

-0.0889

+0.1183

-0.2371

+0.2407

+0.1178

-0.2300

-0.0.2219

-0.0924

+0.7154

+0.6800

-0.1794

+ correlation shows direct impact on the fluoride ion concentration correlation shows indirect impact on the fluoride ion concentration

Fluoride ion concentrations in natural waters have been found to depend on a number of factors.

These include temperature, pH, presence or absence of complexing and precipitating ions, solubility of fluoride-bearing minerals, anion exchange capacity of aquifer materials (OH- for F), type of geological formations traversed by water and the amount of time that water is in contact with a certain geological formation as discovered by Apambire,

et ai.,

1997. This section presents a discussion on the correlations between fluoride and other water quality parameters as observed from the three boreholes that were selected for the study. However, the main source ofF is most probably the dissolution of the various minerals of which the most important is fluorite, CaF2. The inverse relationship between F and Ca and the positive relationship between Fand HCO-

3 and F and Na are in agreement with the following equations:

CaF2 +Na2 C03 ~ CaC0

3

+ 2 Na + + 2F

CaF2 +2NaHCOJ ~ CaCOJ + 2Na+ + 2F+H20 and CO2

5.5.3.2

Correlation of F with Hardness

Water hardness is commonly defined as the sum of the polyvalent cations dissolved in water. The most common such cations are calcium and magnesium, although iron, strontium and manganese may contribute.

Hardness is usually reported as an equivalent quantity of calcium carbonate

(CaC0

3).

It is primarily a function of the geology of the area with which the water is associated.

Waters underlain by limestone are likely to be hard because rainwater containing C02 continually dissolves the rock and carries the dissolved cations to the water system.

These metals can precipitate the fluoride ion as their respective fluorides. The levels of maximum possible calcium and magnesium in the presence of the fluoride ion in water is governed by the solubility principle.

(Details in Chapter 2). The solubility products of calcium fluoride and magnesium fluoride are 3.9 x 10 -

11 and 6.4 x 10 -

9

(molldm-

3)3 respectively. The equilibrium for

CaF2 can be written as follows;

CaF2 ~ Ca2+ + 2F

Ksp [Ca2+][F]2

3.9

X

10-

11 mot3dm-

9

Similarly, for MgF2 it will be;

MgF2 ~ Mg2+ + 2F

Ksp

=

=

[Mg2+][F]2

6.4

X

10-

9 mot3dm-

9

This means that, only when the product of ionic concentrations of calcium and fluoride in water exceeds 3.9 x 10-

11 and that of magnesium and fluoride exceeds 6.4 x 10-

9 these salts will precipitate out.

Otherwise, when the level of fluoride ion in groundwater increases levels of calcium or magnesium ions automatically decreases.

From the results, the correlation between F and Ca2+ depends strongly on the concentrations of the two ions. At lower concentrations for both ions the correlations are positive (Table 28). At high F concentrations and high Ca2+ concentrations the correlation was still positive (Table 28).

At concentrations of F moderately high i.e. between 0,3 - 1,00 mg/R the correlation was negative.

(Table 28) This can be explained using the common ion effect. The dissolution of fluorite is suppressed when the concentration of Ca2+ is above the limit for fluorite solubility. A strong negative correlation between Ca2+ and F (-0,43) in groundwater that contain Ca2+ in excess of that required for the solubility of fluorite was shown (Table 28).

It is observed from the results that in groundwater with low Na + concentration, the fluoride content is generally in the range of 0,02 - 3,0 mg/l (Appendix B). Sodium exhibits a positive correlation with fluoride in many types of groundwater, especially those having low concentrations of calcium

(waters undergoing base exchange). High concentrations of Na+ will increase the solubility of fluorite in waters. This can lead to very high concentrations of fluoride in water.

The results showed moderate to strong positive correlations between Na + and F irrespective of the concentrations of other water quality parameters in any of the boreholes. It can be concluded that

Na+ has a direct influence on the concentrations of the fluoride ion in groundwater and plays a significant role in increasing the solubility of fluorine containing minerals such as fluorite (Table

28).

5.5.3.4

Correlation between pH and F

The correlation was generally negative and not significant. The pH of the water is controlled by the equilibrium achieved by dissolved compounds in the system. In natural waters, the pH is primarily a function of the carbonate system, which is composed of carbon dioxide, CO

2, carbonic acid,

H

2

C03 bicarbonate, HC03- and carbonate, C0

2-

3.

The applicable equilibrium equations and the estimated pH ranges at which are present are:

CO

2

+

H

2

0

H

2

C03 --.

HCO-3 --.

• H

2

C03

W

+ HCO-3

W

+

C03

2pH <6.4

pH: 6.4 - 10.33

pH: >10.3

A process that can also lead to very high concentrations of fluoride in waters and little understood is the anion exchange (Off for F) involving various types of clay minerals.

This process invariably follows base exchange softening (Ca

2

+ and Mg

2

+ for Na +) where the pH is progressively driven to quite high alkaline values (pH 9.0 - to.5). Anion exchange can occur in sedimentary basins ( Boyle and Chagnon, 1995) or igneous terrain but it is most dominant in the sedimentary basins. The relationship of pH and fluoride in groundwater is explained in detail in Chapter 2.

5.5.3.5

Correlation between fluoride and Phosphate

The results show negative correlation between the two species. The natural inorganic phosphorus deposits occur primarily as phosphate in the mineral apatite.

Apatite is defined as natural, variously coloured calcium fluoride phosphate (CasF(p04h) with chlorine, hydroxyl and carbonate sometimes replacing the fluoride.

Apatite is found in igneous, metamorphic and sedimentary rocks.

Phosphate deposits and phosphate rich rocks release phosphorus during weathering, erosion and leaching (Chapter 2). Apatite is widely distributed in all rock types; igneous, sedimentary and metamorphic but is just in small grains, large well-formed crystals though can be found in certain contact metamorphic rocks. Apatite is actually three different minerals depending on the predominance of fluorine, chlorine or the hydroxyl group. These ions can freely substitute in the crystal lattice and all three are usually present in every specimen although some specimens:Cas(P04)3(OH,F,CI), Calcium(Fluoro,ChloroHydroxyl) Phosphate (WRC,

2001).

5.5.3.6

Correlation between Fluoride and Total Alkalinity

The results in Table 28 show positive correlation between the Total Alkalinity and fluoride levels.

This might be due to the release of hydroxyl and bicarbonate ions simultaneously during the leaching and dissolution process of fluoride bearing minerals into the groundwater. That is more and more leaching of minerals into water increases the fluoride ion concentration with high levels of alkalinity as well. High fluoride levels are associated with the high concentration of sodium ions because of greater solubility of sodium fluoride in water. Similarly, high levels of sodium are associated with increased concentration of bicarbonate ions also and this naturally leads to higher alkalinity levels. The correlation between silicate and the electrical conductivity are not discussed in this dissertation. However, the theory is presented in the literature survey.

5.5.4

The role of surface geology

High fluoride levels are mainly found in areas underlain by sedimentary rocks, granites, metamorphic and volcanic rocks (Maps A and B). In the Northern Cape this is mainly in the areas underlain by consolidated to compact sedimentary data, porous unconsolidated to semiconsolidated sedimentary strata and compact sedimentary strata. In North-West province levels higher than the recommended upper limit for drinking water are observed mainly in areas underlain by porous unconsolidated to semi-consolidated sedimentary strata, dolomite chert and subordinate limestone and assemblage of compact sedimentary and extrusive rocks. These are observed in the case of other provinces except for the compact arenaceous and argillaceous strata and the mafic basic lavas that show in the KwaZulu Natal and Limpopo. A detailed and in-depth description of the role of surface geology is however beyond the scope of this dissertation.

77

It is evident from the above observations that the occurrence and the observed distribution of fluoride ion concentrations in groundwater are largely dependent on the geology of the area. The geochemistry also plays an important role in understanding the behavior of fluorides. The tables in

Appendix D show the content of fluoride in various rock types.

From the results of this study, it has been observed that high fluoride levels are mainly found in areas underlain by sedimentary rocks, granites, metamorphic and volcanic rocks This shows that the phenomena of high fluoride levels in groundwater is linked to the geology of the area.

However, this cannot always be traced to geological formations as the water may come in contact with different fluorine-bearing formations kilometres away from these rocks.

Fluorine becomes a component of sedimentary rocks through several processes. Fluorine may be present in resistant minerals as topaz, tourmalite and apatite and to a lesser extent fluorite and the micas. It may be absorbed onto an anion receptor such as a clay particle, or it may be transported into the sediment as an aqueous ion or complex. In marine sediments it may co-precipitate from seawater with CaC0

3 and phosphate. In sediments, F is highest in clay-bearing rocks such as shales and mudstones, (Appendix D) although some sandstone has become cemented by fluorite.

In limestones, some CaF2 and MgF2 co-precipitate with CaC0

3, but most F is found as fluorapatite in the skeletal remains of marine organisms. In gypsum, F co-precipitates with CaS04 as CaF2,but the inability ofF to precipitate as Na or K compounds is reflected in the very low concentrations in rock salt. This can be the case in those coastal areas with high fluoride ion content in their groundwater. (MAPS AI-A3)

No detailed study or field investigations were carried out to determine the cause of the high fluoride levels observed in various regions of the country for this dissertation. The interpretation of the results is based on the observations made after the data was overlain on Vegter's lithostratigraphy and the use of some South African geological maps. A detailed description of the role of geology in the occurrence and distribution of fluoride is given in Chapter

2.

• Areas with high fluoride ion concentrations in their groundwater supplies and high percentage morbidity of dental fluorosis have been identified. Many of these sources require partial de-fluoridation if they are currently used for drinking water purposes or the development of alternative water supplies as a matter of urgency.

• Areas of low fluoride ion concentrations in groundwater have been delineated. In view of the DOH Regulations tabulated in September

2000, such areas are in need of fluoridation.

• Fluorides are found in almost all geological forms but high levels are mainly found in areas underlain by sedimentary rocks, granites, and metamorphic and volcanic rocks.

This shows that the occurrence of high fluoride levels in groundwater is linked to the geology of the area and that chemical leaching (weathering) of the rocks and their associates are important fluoride contributors. However, this origin cannot only be traced to surface geology as other factors also playa role (Chapter

2).

• The release of the fluoride ion into groundwater depends on a number of factors.

These include the solubility of the mineral in which the fluorine atom is found, the pH, the climate, the hardness and the chemical characteristics of the groundwater. Correlations exist between the fluoride ion and Mg, Ca, Na, Total

Alkalinity and silica. The moderate positive correlation between fluoride and silica suggests that there may be a contribution of fluoride to the groundwater from the decomposition of fluorosilicates. However the results reflect that the main source of high fluoride ion concentration in groundwater is most probably the dissolution of fluorite, CaF2. Given the strong correlations between Na and fluorite in some boreholes, it is evident that the presence of sodium ions plays a significant role in increasing the dissolution and hence the solubility of fluorine containing minerals especially fluorite in groundwater.

79

• A weak correlation between fluoride ion concentration in groundwater and the percentage morbidity of dental fluorosis has been shown in some areas. This phenomena could be due to a number of factors among which the differences of the calcium content in the diet of various individuals, variations of fluoride levels in groundwater caused by different geographical conditions in which boreholes are found, injection of fluorides into the hydrological cycle by various industrial activities, socio-economic factors, etc can be mentioned.

From the findings of this study, it is recommended that

• Proper research need to be initiated into investigating cheap and technological simple processes for small scale removal of fluoride from fluoride-rich groundwater or developing alternative methods of water supply in areas where there is such a problem especially in rural areas.

• Combined efforts between the National Department of Health and the Department of Water Affairs and Forestry in determining the fluoridation/de-fluoridation strategies are initiated. It is not practical to fluoridate boreholes; natural springs or hand dug wells on which most of the rural areas depend on. Extensive res.earch

into alternative methods of fluoridation such as salt fluoridation, milk fluoridation, sugar fluoridation and use of fluoride supplements such as fluoride drops, fluoride lozenges, fluoridated toothpaste, fluoridated vitamins, etc need to be initiated in affected areas.

j

Since the delineation of the high-risk areas, with fluoride levels beyond recommended levels for drinking water have clearly been done in this document,

It is recommended that those requiring the upgrading of water ~~~P}i~sand the identification of fluorosis risk areas utilize this document. The mstallation of future boreholes should be accompanied by simple and suitable de-fluoridation techniques. Awareness programmes to educate the public about the consequences of drinking fluoride-rich waters must be in place.

AGRAWAL V AND VAISH A (1998) Fluoride distribution in groundwaters in India, sources, effects and prevention. Groundwater: Sustainable solutions. Proceedings of

International Groundwater conference, Australia. 597 - 599.

ANONYMOUS (1998) Notice R797 of 12 June 1998 Regulations under the Health act,

1977 (Act No. 53 of 1977). Schedule: Regulations of fluoridating public water supplies.

Republic of South Africa Government Gazette. 396 issue 189607 - 14.

APAMBIRE WB, BOYLE DR. and MICHEL FA (1997) Geochemistry genesis, and health implications of floriferous groundwaters in the upper regions of Ghana. Environmental

geology. 33(1) 13-24.

BHARGAVA DS and KILLEDAR DJ (1992) Fluoride adsorption on fishbone charcoal through a moving media adsorbed. Water resolutions. 26(6) 781 -788.

BOYLE DR (1992) Effects of base exchange softening on fluoride uptake in groundwaters of the Moncton Subbasin, New Brunswick, Canada. In: Khavaka,

YK and Maest, AS.

(eds), Water-Rock Interaction, Proceedings

1 h

International Symposium on Water-Rock

Interaction. 771 - 774.

BOYLE DR and CHAGNON M (1995) An incidence of skeletal fluorosis associated with groundwaters of the carboniferous basin Gaspe region, Quebec, Canada. Environmental

Geochemistry and Health. 17 5-12.

BROUWER ID, BACKER DO DE BRUIN A and HAUTV AST JGAJ (1988),

Unsuitability of World Health Organisation guidelines for fluoride concentrations m drinking water in Senegal. LANCET (London UK) (1) no. 8579223 - 225.

BURT BA (1992) The changing patterns of systemic fluoride intake. Journal of Dental

Research 711228-1237.

BURT BA, WAGNER BM, CANTOR KP, KREWSKI D, LEVY SM, Mcconnell EE and

WIllTEFORD FM (1993) Health effects of ingested fluoride. Fluoride. 26(4) 278-281.

CARSTENS N (1995) Personal communication. Community Dentistry, University of

Stellenbosch.

CHEN W, XU R, GUANGHUA C, JZAO J and TICHONG C (1993) Changes of the prevalence of endemic fluorosis after changing water sources in two villages in

Guangdong, China Bull. Environ. Contam. Toxico!. 51479 - 482.

CHIKTE UME and JOSIE-PEREZ A (1995) Perceptions regarding knowledge, purpose and desirability of water fluoridation in South Africa Fluoride and fluorosis.

The status of

South African Research, Pilanesberg National Park, North- West Province. 9.

CLAIR NS, PERRY LM and GENE FP (1994) Chemistry for Environmental Engineering,

Fourth Edition, McGraw -Hill. International editions. 583-585.

DEAN HT (1942a) Epidemiological studies in the United States. Fluorine and dental

health. Washington DC, American Association for Advancement of Science. Publication no.

19.

DEAN HT (1942b) Relationship between dental caries and fluoride level in drinking water.

JournalAmerican Water Works. 351161.

DEAN HT and ~CKA Y FS (1939) Production of mottled enamel halted a change in common water supply. American Journal of Public Health. 29 590 - 596.

DRISCOLL WS (1985). Prevalence of Dental caries and dental fluorosis in areas with optimal and above optimal water fluoride concentrations. Journal of International Society

for fluoride research. 18 (3) 174-175.

DRISCOLL WS (1985) What we know and don't know about dietary fluoride supplements the research basis. ASDC J Dent Child. 52 259-264.

83

DU PLESSIS JB (1995) What would be the maximum concentration of fluoride in water that would not cause dental fluorosis? Fluoride and Fluorosis. The status of South African

Research, Pilanesberg National Park, North West Province. 4.

DWAF (2000) Policy and strategy for Groundwter Quality Management in South Africa,

r t

Edition. 1.1-8.2.

EDMUNDS WM AND SMEDLEY PL (1996) Groundwater chemistry and health: an overview. In Appleton, Fuge and MCCall(Eds). Environmental Geochemistry and Health

Geological Society Special Publication. 11391-105.

FAYAZI M (1994) Regional groundwater investigation on the Northern Springbok flats.

Department of Water Affairs and Forestry. Geohydrology, GH Report no. 3684 108-155.

GACIRI SJ AND DAVIES TC (1993) The occurrence and geochemistry of fluoride in some natural waters of Kenya Journal of hydrology. 143(3-4) 395-412.

GINSTER M and FEY MY (1995) Soil and plant responses to irrigation with a fluoriderich waste water. Fluoride andjluorosis. The status of South African Research, Pilanesberg

National Park, North West Province. 3.

GOSSELIN DC (1997) Domestic well-water quality in rural Nebraska: Focus on nitrate nitrogen, pesticides and coliform bacteria Groundwater monitoring and Remediation 17(2)

77-87.

GOSSELIN DC, HEADRICK J, HARVEY FE, TREMBLAY R AND McFARLAND K

(1999) Fluoride in Nebraska's groundwater. Groundwater monitoring and remediation.

19(2) 87-95.

GROBLER SR and DREYER AG. (1988) Variations in the fluoride levels of drinking water in South Africa. Implications for fluoride supplementation. South African Medical

Journal. 73217-219.

GUO S AND WANG J (1998) Control of fluorosis in China XXIInd conference of the

International Society for fluoride Research, Fluoride.

31(3) 5.

HAIKEL Y, CAHEN PM, TURLOT JC and FRANK RM (1989) Dental caries and fluororsis in children from high and low fluoride areas of Morocco. Assoc.

J

Dent. Child.

Sept-Oct. 56(5) 378-381.

HAMMER MJ. (1986), Need for fluoridation of desalinated water supplies. Aqua. 4 179-

182.

HARGREAVES JA (1990) Water fluoridation and fluorine supplementation.

Considerations for the future.

J

Dental Res. 69(special issue) 765-770.

HEILMAN JR, KIRITSY MC, LEVY SM and WEFEL JS (1997) Fluoride concentrations of infant foods. Journal of American Dental Association, July. 128(7) 857-63.

JANSSEN PJCM, JANUS JA and KNAAP AGAC (1988) Integrated criteria document on fluoride effects. Appendix .Bilthoven, the Netherlands. National Institute of Public Health

and Environmental Protection.

JINADASA KBPN, DISSANAY AKE CB, WEERASOORlY A SVR and SENARATOE A

(1993) Adsorption of fluoride on goethite surfaces, implications on dental epidemiology.

Environmental geology. 21(4) 251-255.

LAKSHAM BT (1979) Groundwater organic/inorganic pollutant health standards. Water

and Sewage works, Chicago. 174-176.

LEONE NC (1955). Roentgenological study of human population exposed to high-fluoride domestic water: ten-year review. American Journal. Roentgenol. Rad. Therapy and

Nuclear Med. 74 874 - 885.

LEWIS HA and CHIKTE VM. (1995) Prevalence and severity of fluorosis in the primary and permanent dentition using the TlSF.

J.

Dent. Association South Africa. 50 467-471.

~CAFFREY LP. and WILLIS JP (1993) Distribution offluoride-richgroundwaters in the eastern parts of Bophuthatswana, relationship to bedrock and soils and constraints on drinking water supplies: a preliminary report. Africa Needs Ground Water. An International

Ground Water convention.

1

1-8.

MEEUSEN JCL, SCHEIDEGGER A, HIEMSTRA J, VAN RIEMSDIJK WH and

BORKOVEC M (1996). Predicting multicomponent adsorption at variable pH in a goethite-silica sand system Environmental Science Technology.

30

481-488.

MOHLAHLO (2000) Fluorspar. Personal Communication. Department of Minerals and

Energy South Africa 1-5.

MULLER WJ, HEALTH RGM and VILLET MH (1998) Finding the optimum: fluoridation of potable water in South Africa Water SA. 24(1) 21 - 27.

MUNZHELELE (1998) Fluorspar. Personal Communication. Department of Minerals and

Energy. South Africa

MURRAY 11, RUGG-GUNN AJ and JENKINS GN (1991) Fluorides in caries prevention

(3

Td ed.).

Butterworth. Heineman Ltd. Oxford.

NAIR KR, MANn F and GITONGA IN (1984). The occurrence and distribution of fluoride in groundwaters of Kenya IAHS. 44 75 - 86.

NANY ARO IT, Aswathanarayana U and MUNGURE JS (1984) A geochemical model for the abnormal fluoride concentrations in parts of North em Tanzania J. Afr. Earth Sci. 2(2)

129-140.

NICHOLSON K and DUFF, EJ (1981) Fluoride determination in water. Analytical letters.

14493-571.

OCKERSE T (1946) Endemic fluorosis in South Africa .Union of South Africa

Government Printer Pretoria. 114pp.

OCKERSE T (1947) Endemic fluorosis in South Africa a PHD Thesis submitted to the

University of Witwatersrand.

OCKERSE T. (1943) Endemic fluorosis in South Africa, Department of Public Health,

Pretoria 93pp.

PELPOA KU, PIENAAR P and XU Y (1992) Development of groundwater resources in

Bophuthatswana In proceedings of the

Ilf h

WEDC Conference. Kathmandu. Nepal.

PLANKEY BJ and PATTERSON HH (1986) Kinetics of Aluminium fluoride complexation in acidic waters. Environment Science and Technology. 20 160-165.

PONTIUS FW (1991) Fluoride regulation and water fluoridation. Journal American Water

Works Association. 83(11) 20, 22, 96.

RAGAGOPAL R AND TOBIN G (1991) Fluoride in drinking water a survey of experts.

Environmental geochemistry and health. 13(1) 3-13.

RAO NR and PRASAD PR (1997) Phosphate pollution in the groundwater of lower

Vamsadhara river basin, India. Environmental geology. 31 117-122.

RAO NS, RAO JP, RAO BN, BABU PN, REDDY PM and DEVADAS OJ (1998) A preliminary report on fluoride content in groundwaters of Guntur area Andra Pradesh,

India. CurroSci.75 (9) 887-888.

RAO NVR, RAO N, RAO KSP and SCHUILING RD (1993) Fluorine distribution in waters ofNalgonda district, Andra Pradesh India. Environ. Geol. 21 84-89.

RAWHANI S (1986) Incidence of microbial, fluoride and nitrate pollution in groundwater.

Seminar on technology transfer in water supply and sanitation in developing areas -

Bophuthatswana, Mmabatho.I-17.

RUDOLPH MJ, MOLEFE M and CHIKTE OME 1995 Dental fluorosis with varying levels of fluoride in drinking water. Fluoride and Fluorosis. The status of South African

Research, Pilanesberg National Park, North West Province. 5.

SARA H (1993) Treatment of aqueous eftluent for fluoride removal. Water Resolution, 27

(8) 134-1350.

SCHOEMAN JJ and BOTHA GR (1985a) An evaluation of the activated alumina process for fluoride removal from drinking water and some factors influencing its performance.

Water SA 11(1) 25.

SCHOEMAN JJ and MACLEOD H (1987) The effect of particle size and interfering ions on fluoride removal by activated Alumina. Water SA. 13 (4) 229-234.

88

SCHOEMAN J1. and BOTHA GR (1985b) Fluoride removal by Activated Alumina and

Reverse Osmosis. Colloquium on treatment and re-use of water in the mining and

metallurgical industry. Randburg, 9-10 May 1-15.

SCHOEMAN JJ and BOTHA GR (1985c) An evaluation of the Activated Alumina process for fluoride removal from drinking water and some factors influencing its performance.

NWR REPRINT RW0990. Water South Africa. Pretoria. 11(1) 25-32.

SIMONIC M (2001) An assessment of groundwater quality at a national scale in the

Republic of South Africa. WRC Project no. K5/841 (electronic atlas).

THOMPSON H (1994) Finding "hidden" fluoride. WWTwater and waste treatment.

37(1)

22,43.

USNRC (1993) Health effects ofIngested fluoride. United States National Research

Council. National Academy Press. Washington, D.C.

USPHS (1991) Review of fluoride. Benefits and Risks. Report of Ad hoc subcommittee on fluoride. Committee to co-ordinate Environmental Health and Related Programs, Feb.

VEGTER JR (1993) Paper 44. Concepts for mapping South Africa's hydrogeology. Africa needs groundwater. An International Ground water Convention, Johannesburg, South

Africa 2 1-11.

WANG XC, KAWAHARA K and GUO XJ (1999) Fluoride contamination of groundwater and its impacts on human health in Inner Mongolia area China. Aqua. 48 (4) 146-153.

WHO (l984a)

Guidelines for drinking water quality, Recommendations,

2 nd edition

Geneva 1

WHO (l984b) Fluorine and fluorides: Environmental Health criteria. World Health

Organization Publication, Geneva, Switzerland. 36:364p.

WHO TECHNICAL REPORT (1970). Guidelines for drinking water quality. 1: Geneva

Switzerland.

WHO (1996) Guidelines for drinking water quality, second edition. Health criteria and other supporting information Geneva 2: 231- 237.

WRC (1998) Quality of Domestic Water Supplies. 1 Assessment Guide, Second Edition

WRC Report no.

ITIOI/98.

WRC (2001) Distribution of fluoride-rich groundwater in the Eastern and Mogwase regions of the Northern and North-West provinces. WRC Report No.

526/JlOI

South Africa: 1.1-

9.85.

ZIETSMAN S (1991) Spatial variation of fluorosis and fluoride content of water in an endemic area in Bophuthatswana

J.

Dent. Ass. S.Africa. 46 11 - 15.

APPENDIXA

VARIATIONS OF FLUORIDE ION

CONCENTRATIONS IN SELECTED BOREHOLES,

1994-2000

Variations in F ion concentrations 1994-2000in sele cte d monitoring sites

1.2

:::: :

C)

.

E c

( ,)

c

0

(, )

L L

0.8

0 .

6

1

0 .

4

-

0 .

2

-

0

-

-

f --

f -f -f --

]

J

] ] ] ]

1

1 n n n

.

Z QMW RB1

OZ QMW SB1

OZ QMW VL 1

Var i ations in F ion concentrations 1994-2000 in selected monitoring sites

1 .

2

1

:: :::

C)

E

.

E u c

0 u .

0.

8

-

0 .

6

0 .

4

-

f --

f --

f -r --

r --

-

r --

0 .

2

0

I

-

I r --

-

I

J I

I

I

-

-

-

-

-

J

I

I

J

• ZQ MYZF1

O ZQ MADL1 oZQ MAD01

6

5

(,, ) c :

0

(, ,) u .

:: :::

C)

E c :

4

3

2

1

0

Variations i n F ion concentrations 1994-2000 in selecte d monitoring sites

1

0.9

-

0.8

-

: en o

.

7 -

.

E

0 .

6 c u c

0

U

L L

-

0.5

-

0 .

4 -

0.3

-

0.2

-

0.1

o -

1 2

I -I --

-

3 4 5 6 7 8

9

10 11 12 13 14

Season

.

ZQM BR M1

DZQM BR N1

DZQM BU R1

.

ZQ MBW W1

OZ QMCL V1

DZ QMCN W

Variations in F ion concentrations 1994-2000 in selecte d monitoring sites

E

-

-

C )

0 .

7

0 .

6

.-

C

0 .

5

CJ

C

0 .

4 o

CJ

0 .

3

LL

-

c -

' -c -

' --

~

' --

n c c -

I --

~ f c -

-

-

-

~

' --

-

t

T 1

-

:L

-

1

1

1

]

]

1

ZQM CPD1

DZ QMC RA1

DZ QMC TN1

Variat i ons in F ion concentrations 1994 2000 in selec ted monitoring sites

3

2.5

::::

C )

E

.-

CJ

C

0

CJ

LL

2

1.5

-

1

-

0.5

0

IT

~

.

Z QM FRR1

DZ QM GDN1

DZ QM HFR1

Variations in F ion concentrations 1994-2000 in selecte d monitoring sites

2

1.8

1.6

=: 1 .

4

C )

E c

0-

1.2

( , )

1

C o

( , )

LL

0.8

0.6

-

-

-

-

0.4

-

0.2

o

-

r -

I -

I -

-

-

.

ZQ MLB W1

DZQ MLO X1

DZ QMM AT1

CORRELATION STUDIES OF THE FLUORIDE ION

AND OTHER WATER QUALITY PARAMETERS

Monitoring Feature 10:

Latitude:

Longitude:

88493

-28.566111

16.508056

name: ZALEXBAYIBOREHOLE AT OPPEINHEIMER BRIO

Drainage Region:

0

First date: 1810311997 n=25

DATA FROM A BOREHOLE AT OPPEINHEIMER BRIO

Last date 2001/05/02

0.307

14.102

0.282

11.521

0.272

14.631

0.250

14.809

0.275

0.285

15.750

19.450

0.320

22.400

0.382

0.294

16.952

15.100

0.285

0.275

0.217

0.217

0.230

11.530

15.133

0.218

16.200

12.700

0.280

12.820

0.230

15.240

0.240

11.740

0.210

0.210

0.220

0.222

15.450

13.475

11.000

10.600

11.150

11.950

0.243

13.580

0.380

16.830

0.330

14.050

4.481

3.966

32.969

3.464

39.470

3.566

2.985

3.610

4.500

37.031

38.151

36.600

45.500

50.800

36.231

34.421

37.840

35.580

34.474

39.041

60.736

49.029

38.600

40.100

38.379

41.850

53.535

43.800

51.600

47.170

55.020

86.950

55.200

64.300

102.300

52.971

47.700

46.910

3.698

3.808

4.200

38.364

37.540

39.350

3.495

34.675

2.760

29.700

36.800

37.450

37.650

31.467

37.400

43.900

2.607

35.767

2.805

39.000

2.380

2.310

2.765

31.025

32.520

35.980

34.350

32.920

40.040

26.050

2.545

29.450

2.790

29.200

2.270

28.600

3.385

28.400

24.550

20.800

24.700

2.640

28.650

22.450

2.790

32.140

28.340

3.650

41.770

3.490

36.900

41.830

37.600

34.080

34.050

32.850

23.333

42.433

49.700

35.600

36.775

44.320

22.150

17.250

14.200

34.450

35.200

15.710

40.350

20.950

28.660

37.250

40.440

45.970

32.800

60.960

67.850

51.050

37.133

39.333

42.050

32.950

32.800

38.440

32.350

46.900

42.250

0.01$

0.020

0.03~

0.017

0.018

0.01~

0.021

0.024

0.01S

0.016

0.024

0.Ot6

0.021

0.021

0.018

0.0~7

0.017

0.008

0.013

0.059

0.048

0.0C)9

0.0C)7

0.015

0.011

8.440

128.289

--0:625

8.100

120.660

0.460

8.230

133.450

8.210

142.530

8.250

141.150

0.195

0.126

8.300

8.310

134.200

142.800

0.059

0.099

0.105

8.570

155.350

8.310

131.340

8.280

132.150

8.080

121.550

8.140

111.630

8.420

8.210

8.320

8.250

8.450

8.340

8.170

8.320

8.530

8.350

131.200

132.250

117.900

119.800

144.160

121.850

110.750

8.180

100.000

8.220

103.900

8.350

99.900

116.080

146.170

150.400

0.141

0.152

397.11

349.00

360.00

0.148

0.172

0.312

325.00

272.67

0.105

0.091

333.67

350.50

0.208

294.00

0.156

297.00

0.074

0.303

0.495

353.20

274.50

257.00

0.499

0.547

0.069

0.072

0.129

0.098

-347-.73 --e:-540

315.92

51.400

5.531

45.600

352.15

352.16

361.50

422.25

474.00

236.00

253.50

246.00

288.00

376.00

351.00

5.557

51.930

4.452

4.452

6.320

50.500

5.900

51.050

6.090

61.550

6.440

68.800

4.140

4.620

4.790

5.107

46.200

5.860

39.700

5.320

48.133

6.835

51.350

4.765

43.250

4.410

50.340

6.215

57.450

50.540

52.750

42.800

38.650

37.600

5.740

35.200

5.220

38.400

2.340

35.750

3.030

42.220

3.640

53.970

5.490

50.800

0.015

0.031

0.023

0.061

0.054

0.020

0.025

0.022

0.012

0.018

0.031

0.027

0.028

0.011

0.057

0.032

0.020

0.020

0.020

0.020

0.017

0.086

0.009

0.020

0.019

1.000

0.572

0.667

0.634

0.666

0.547

0.467

-0.179

0.508

0.715

-0.230

0.689

-0.092

0.684

-0.283

0.572

1.000

0.537

0.959

0.902

0.924

0.803

-0.170

0.411

0.735

-0.568

0.952

0.123

0.953

-0.146

0.667

0.537

1.000

0.666

0.561

0.438

0.762

-0.048

0.134

0.482

0.089

0.670

0.164

0.691

-0.279

0.634 -

-0.666

0.959

0.666

1.000

0.891

0.903

0.841

-0.126

0.307

0.759

-0.465

0.970

0.205

0.976

-0.184

0.178

0.949

-0.234

0.902

0.561

0.891

1.000

0.944

0.659

-0.160

0.370

0.847

-0.501

0.956

0.924

0.438

0.903

0.944

1.000

0.651

-0.215

0.375

0.776

-0.573

0.932

0.145

0.924

-0.185

- 0.547

0.467 -

:O.17~

0.803

0.762

0.841

0.659

-0.170

-0.048

-0.128

-0.160

-0.215

0.651

1.000

-0.014

-0.014

1.000

0.061

-0.265

0.398

' -0.28~

-0.179

0.795

0.454

-0.183

0.286

0.815

0.016

0.234

-0.141

0.437

-

0.508

0.411

0.134

0.307

0.370

0.375

0.061

-0.265

1.000

0.527

-0.296

0.376

-0.354

0.370

-0.155

0.715

0.735

0.482

0.759

0.847

0.776

0.398

-0.289

0.527

1.000

-0.529

0.849

0.070

0.824

-0.412

-0.230

-0.568

0.089

-0.465

-0.501

-0.573

-0.179

0.454

-0.296

-0.529

1.000

-0.481

0.407

-0.446

0.252

0.689

0.952

0.670

0.970

0.956

0.932

0.795

-0.183

0.376

0.849

-0.481

1.000

0.194

0.996

-0.226

-0.092

0.123

0.164

0.205

0.178

0.145

0.286

0.234

-0.354

0.070

0.407

0.194

1.000

0.207

0.076

0.684

0.953

0.691

0.976

0.949

0.924

0.815

-0.141

0.370

0.824

-0.446

0.996

0.207

1.000

-0.202

-0.283

-0.146

-0.279

-0.184

-0.234

-0.185

0.016

0.437

-0.155

-0.412

0.252

-0.226

0.076

0.076

1.000

Monitoring Feature

Latitude:

10:

89775

-22.569167

Longitude: 28.621944

DATA FROM A BOREHOLE AT TUGELA BAD

1.242

4.787 <1

5.212 <1

4.650

4.950 <1

5.600 <1

5.650 <1

5.010 <1

4.800 <1

5.320 <1

4.950 <1

4.980

5.594

1.357

1.500

1.600

6.830

name: ZQMTUG2 TUGELA BAD

Drainage Region: AB3 n=13

8.540

8.689

8.771

8.760

9.470

8.330

8.390

8.020

8.820

8.550

8.260

8.260

8.150

128.973

422.205

415.205

417.600

447.700

405.500

394.600

386.600

400.300

398.500

392.600

406.600

128.193

359.175

324.000

370.425

356.900

413.800

369.400

379.000

367.500

370.200

376.700

361.200

373.900

338.786

298.973

422.205

415.205

417.600

447.700

405.500

394.600

386.600

400.300

398.500

392.600

406.600

403.684

237.136

513.106

500.074

534.700

550.100

483.500

485.100

463.200

487.000

525.500

484.900

525.600

488.800

-

..

,,"

CORRE

<..

',~!.~

"''''

110 CO FI NTSa < 5

1.000

0.534

-0.118

0.535

0.119

0.804

0.870

-0.222

-0.216

0.534

1.000

-0.683

-0.551

-0.837

0.295

0.232

-0.694

-0.972

0.118

-0.212

-0.843

~'.ii;i

0.850

0.185

0.241

0.166

-0.229

-0.383

-0.329

0.334

1.000

-0.118

-0.683

1.000

0.349

0.468

0.393

0.223

0.392

-0.216

-0.171

0.071

0.339

-0.131

0.225

-0.521

0.535

-0.551

0.349

1.000

0.395

0.686

0.711

0.211

0.241

0.143

-0.182

0.757

0.122

-0.211

-0.445

0.119

-0.837

0.468

0.395

1.000

0.215

0.196

-0.031

0.443

0.059

-0.662

0.351

-0.107

-0.249

-0.257

0.069

0.026

-0.141

-0.122

0.962

0.042

-0.057

-0.507

0.804

0.295

0.393

0.686

0.215

1.000

0.955

0.015

-0.070

-0.143

-0.175

0.975

0.008

-0.176

-0.412

0.870

0.232

0.223

0.711

0.196

0.955

1.000

0.019

0.017

0.028

0.034

0.014

0.014

0.014

0.012

0.013

0.013

0.005

0.015

0.007

8.10

8.70

7.57

8.80

8.08

7.61

8.24

7.73

8.07

8.09

8.74

8.23

7.70

First date: 95/06/27

Last date: 2001/01/05

32.569

32.309

33.362 <0.04

0.147

0.256

34.000

0.077

25.000

42.600

56.900 <0.04

0.054

0.115

43.500

0.055

27.000 <0.04

31.000

0.139

21.700

16.700

0.040

0.088

22.786 <0.04

:lfj~~J_'~;~;Si;;;~i

1075.64

1452.41

1461.00

34.163

38.989

36.636

250.000

238.000

232.000

1508.00

1585.00

1454.00

1469.00

1408.00

1434.00

1486.00

1409.00

1460.00

1408.03

30.340

33.210

37.370

41.610

32.960

33.200

34.320

32.800

35.440

34.019

0.080

0.052

229.000

236.000

240.000

2.600

0.048

0.090

0.046

0.062

220.000

223.000

220.000

260.000 <0.04

2.600 <0.04

248.000 <0.04

0.070

0.078

0.049

0.057

-0.222

-0.694

0.392

0.211

-0.031

0.069

0.015

1.000

-0.117

0.182

0.164

0.056

-0.104

0.028

0.354

-0.216

-0.972

0.384

0.241

0.443

0.026

-0.070

-0.117

1.000

-0.336

-0.673

-0.010

-0.456

0.280

-0.227

0.182

-0.340

1.000

0.172

-0.015

0.540

-0.225

0.429

0.118

~1.it~1\(i

-0.212

-0.329

-0.171

-0.843

-0.071

-0.182

0.143

0.059

-0.141

-0.143

-0.662

-0.122

-0.175

0.164

-0.670

0.172

1.000

-0.228

0.749

0.105

-0.312

0.850

0.185

0.339

0.757

0.351

0.962

0.975

0.056

-0.010

-0.015

-0.228

1.000

0.045

-0.179

-0.413

0.241

0.166

-0.131

0.122

-0.107

0.042

0.008

-0.104

-0.456

0.540

0.749

0.045

1.000

-0.507

-0.292

-0.229

0.334

0.225

-0.211

-0.249

-0.057

-0.176

0.028

0.280

-0.225

0.105

-0.179

-0.507

1.000

-0.143

i••

Ric',i

-0.383

1.000

-0.521

-0.445

-0.257

-0.507

-0.412

-0.354

-0.227

0.429

-0.312

-0.413

-0.292

-0.143

1.000

IpH

N03+N02

F

TAL

Na

Mg

51

P04-P

S04

CI

K

Ca

EC (mSlm)

OMS-Tot

Monitoring Feature

10:

Latitude:

89740

-31.29611

Longitude: 25.830278

DATA FROM A BOREHOLE AT STEYNSBURG

II~

7.971

1.073

0.397

281.468

8.129

3.058

0.400

267.822

7.75

7.3

7.7

7.9

7.86

7.35

7.35

8.01

8.29

8.02

8

3.740

2.820

1.783

1.648

2.115

1.453

1.697

2.848

3.582

1.904

4.380

0.740

0.970

0.470

0.430

0.560

0.400

0.390

0.380

0.320

0.390

0.390

322.200

297.800

313.600

329.900

323.400

287.900

321.500

311.200

332.300

329.800

337.400

113.401

125.108

129.300

135.800

138.300

146.000

132.700

140.300

130.600

126.400

112.400

130.200

137.000

Name: ZQM5TB1 5TEYN5BURG

Drainage Region Q12 start date:

OORP5GEBIEO

21/04/1994

n=13 Last date:

2810512001

29.162

23.936

19.100

21.500

20.100

23.400

18.400

20.000

23.400

23.200

44.500

23.600

30.500

10.105

9.575

10.570

9.040

10.690

10.450

9.290

10.000

9.850

10.880

15.980

10.090

10.020

a~~4~;~~Ef!;

0.014

192.198

0.011

0.014

0.008

0.009

0.016

0.006

0.011

0.007

0.013

0.011

0.009

0.017

183.039

149.200

146.300

160.100

178.200

156.900

178.100

167.900

172.800

204.300

182.900

229.700

130.675

117.076

98.000

103.400

101.200

96.900

94.000

106.900

102.500

104.500

123.100

108.800

148.600

0.941

0.694

0.350

1.260

1.510

1.790

1.290

0.700

0.710

0.750

0.720

0.670

0.700

1.000

-0.473

-0.506

-0.121

0.254

-0.014

-0.134

0.058

0.315

0.097

a

<

~~II_'!!j

-0.473

1.000

0.183

0.313

-0.143

0.362

0.309

0.338

0.315

0.401

-0.443

0.451

0.009

0.199

0.087

0.419

-0.089

0.490

-0.506

0.183

1.000

-0.089

0.255

-0.441

-0.377

-0.237

-0.386

0.401

0.160

-0.427

0.118

-0.444

-0.121

0.313

-0.089

1.000

0.215

0.229

0.348

0.099

0.179

-0.042

0.082

0.442

0.174

0.612

0.254

-0.143

0.255

0.215

1.000

-0.632

-0.528

0.027

-0.263

-0.391

0.482

-0.063

0.061

-0.036

-0.014

0.362

-0.441

0.229

-0.632

1.000

0.825

0.280

0.718

0.654

-0.212

0.537

-0.249

0.633

-0.134

0.309

-0.377

0.348

-0.528

0.825

1.000

0.142

0.373

0.217

0.217

0.209

-0.203

0.381

0.058

0.338

-0.237

0.099

0.027

0.280

0.142

1.000

0.559

0.514

-0.101

0.548

-0.438

0.524

0.315

0.308

-0.679

0.179

-0.263

0.718

0.373

0.559

1.000

0.887

-0.250

0.861

-0.232

0.859

0.097

0.401

-0.386

-0.042

-0.391

0.654

0.217

0.514

0.887

1.000

-0.349

0.814

-0.288

0.733

0.451

-0.443

0.160

0.082

0.482

-0.168

-0.101

-0.101

-0.250

-0.349

1.000

-0.338

0.270

-0.188

114.902

97.528

102.200

97.600

98.900

127.800

119.900

107.900

119.500

114.700

107.400

131.400

92.500

1116.000

108.400

106.400

112.800

110.300

120.600

121.600

159.900

114.900

129.000

130.200

126.100

150.300

929.708

887.921

908.000

882.000

911.000

964.000

900.000

912.000

938.000

931.000

1027.000

979.000

1138.000

0.009

0.419

-0.427

0.442

-0.063

0.537

0.209

0.548

0.861

0.814

-0.338

1.000

-0.293

0.948

l'''ztmJlm~\li:IIc~tti2;;E

0.199

0.087

-0.089

0.490

0.118

0.174

-0.444

0.612

0.061

-0.249

-0.203

-0.438

-0.232

-0.288

0.270

-0.293

1.000

-0.167

-0.036

0.633

0.381

0.524

0.859

0.733

-0.188

0.948

-0.167

1.000

Correlation between F and Total A1kalinity(T AL)

TAL

=

317.13 -10.65 * F

Correlation: r = -.0889

310

~300

260

0.2

~

········-t..···················~···········

.

-=-j~j~~t~::=::t:::tj==t==

+._

..._ 1

-0 ; ..__..

_~._.!.._

J..

i .....•.......

_

~

~.

l..

::

.

···················t···················1·····················r······_·········-1····· ..···_..·······~..···················j····················[··· ..···..··o····j ..····

~

.

.

.

~

;

~

;

-~=t=f==Ff::F=t=t=~-=

····················r···················o···········,'··--··f······ __···..···•.1·····_··· ..·········r··············_···1···--·····_·······!· ..··················~·····-...__..._f ~.

~ ~

'0.... Regression

95% confid.

0.6

F

Fig The effect of Total Alkalinity on the fluoride ion concentration s in borehole water at

Steynberg.

Correlation between F and Na

NA

=

124.02 + 13.661 * F

Correlation: r

=

25475

150

145

140

135

~

130

125

120

115

110

0.2

,0

0.3

0

0.4

0

.. ... ... ...

.0 ...

..

..

,

'"

", .i.

".-

....

0.5

...

0.6

F

0.7

'

..

..

0.8

0.9

1.1

"0....

Regression

95%conlid.

Fig The effect of sodium ion concentration on the fluoride ion concentration in borehole water at

Steynberg

CorrelatIon ~ F and Mg

MG •• 32.757 -16.84· F

CorreIaIIon: r.

-.4412

36 i

32

28

24

20

48

44

40

0

0.3

0.4

0.5

0.6

F

0.7

0.8

0.9

1.1

'0.... Reg.-ion

95% oonfid.

Fig The effect ofHardness(Mg ion concentration) on F ion concentration in borehole water at

Steynberg

CotTeIa1ion ~ F and 5i

51" 12.226 - 3.590 • F

ComIIation: r" -.3772

13 ii)

12

17

16

15

14

11

10

9

8

0.2

··.·0···

...

.....

..

..

...

...

...

0.3

0.4

0.5

0.6

F

0.7

0.8

0.9

1.1

'0....

Reg_ion

95% confid.

Correlation ~ F and Ca

CA" 130.56 - 40.51 • F

Correlation: r· -.4273

130

~

120

110

170

160

150

140

...

:

···0;

....•.....

...

90

80

02 0.3

0.4

0.5

0.6

F

0.7

0.8

0.9

1.1

'0...

R~

95% conIid.

Fig The effect of Hardness (Calcium ion concentration) on fluoride ion concentration in borehole water at Steynberg

ComIIation between F and EC

EC_MS_M= 113.46+ 179.44 of

Correlation: r" .11832

1200

1000

800

:lEI

(I)

:lEI

0 w

600

400

200

0

0.2

0.3

,0

c&

0

0

0.4

0.5

...

0

0.6

F

0.7

0.8

0.9

0

":'"

1.1

'0...

Regression

95% confId.

ComIIalion between F and pH

PH

=

82376 - .8753 • F

ComIIalion: r=-.5057

1.1

'0....

Regresaion

95%conIId.

0.6

F

0.7

CorreIstion between F and Mg

MG

=

-.1815 +.72956· F

Correlation: r

=

.53362

7.5

6.5

5.5

4.5

i

3.5

2.5

1.5

0.5

0.5

6.5

'0....

Regression

95% confKl.

Fig The effect of Hardness(Mg ion concentration) on the fluoride ion concentrations in in a borehole along the TUGELA

ComtIaIIon between F and Ca

CA" 121.74 + 50.394 * F

Corr8lstion: r"

.53515

400

350

C5

300

250

200

150

100

0.5

0

1.5

2.5

3.5

F

4.5

6.5

--O""Reg~

95%confld.

Fig The effect of Hardness (Ca ion concentration) on the fluoride ion concentration in a borehole along theTIJGELA

Correlation between F and Na

NA '"' 355.50 + 2.2230 * F

Correlation: r'"'

.11873

:!

370

L_-O------------:~..:::--.lL---l

60

50 ...

40

~

30

20

10

0.5

0

1.5

Correlation ~ F and TAl.

TAl. '" 26.870 + 1.1175·F

CorreIalion:r"'.11781

6.5

'0-...

Reg..-lon

95'YoconfId.

38 en

36

34

32

44

42

40

30

28

0.5

ColT8lallon bel1N8en F and 51

51'" 31.920 + .63911 • F

ComtIation: r '" .24068

6.5

'0-...

Regression

95'YoconfKl.

F andMg ft.£AN_MG" 5.7946 + 31.960 - MEAN_F

Correlation: r" .57238

i,

18

16

;

14

24

22

20

12

10

8

0.18

..: ... Q.

0' 0

'0....

Reg~

95% confId.

0.3

MEAN]

Fig The effect of Hardness (Mg ion concentration) on fluoride ion concentration in borehole water at

ZAIEXBAYI

ComIlation between F and Ca

MEANCA= 16.546+ 71.305 -MEAN_F

Correlation: r" .63393

~

~

::E

42

34

30

26

0.18

0.22

0.26

0.3

MEAN]

0.34

0.38

'0.... Regl8SSion

95% conIkI.

Fig The effect of Hardness (Ca ion concentration) on the fluoride ion concentration in borehole water at ZALEXBA YI

60

55

50

45

40

~I

2

!

35

30

25

20

15

0.18

..0 '0"

...0 ...

I:J

0.22

ComtIslion between

F

8Ild

Na

MEAN_NA" 4.9477 + 116.44 *MEAN1

ComtIslion: r" .66577

0.3

MEAN1

0.42

"0....

Regre&lSion

95% conftd.

Fig The effect ofNa ion concentartion on fluoride ion concentration in borehole water at

ZALEXBAYI

Correlation between F and TAl.

MEANTAl." 67.947 + 223.37 *MEAN_F

ComtIslion:r-.71537

165

155

145

~ i

135

125

115

105

95

0.18

0;

00;

0

0'

:0

0.22

90.

0.26

0.3

MEAN1

0.34

0.38

0.42

"0....

Regression

95% confid.

CorreI8tion between F and Si

MEANSI- 5.7048 - 2.070 • MEAN]

Correlation: r

=

-.0924

8 in

~

:E

5

4

6

7

3

2

0.18

0

...

0

0 j)'

~'

...

~

...

d

0

0

0

._;

...

f)

0

0

0 ...

00

0

0

0

0

-

.....

p

0.22

0

0.26

0.3

MEAN_F

0.34

0.38

0.42

'0....

R~

95% confid.

N.B Pearson Product moment correlation was used for the study. Marked correlations are significant at p< 0.05 n=13, 13 and 25 respectively.

OPTIMUM FLUORIDE ION CONCENTRA nONS FOR

DRINKING WATER CALCULATED FOR TIlE

REPUBLIC OF SOUTH AFRICA, 1985-1999

Ca e Town D.F Malan

Geor e P.W. Botha

East London

Jan SmutslJohannesbur

Int.

Port Elizabeth-WI<

Louis Bothal Durban

Bloemfontein JBM Hertzo

Kimberl

U in ton

Bethlehem

Pretoria

Nels ruit-Friedenheim

Pietersbur

211790

286904

595729

0476398A3

351795

0240808AJ0240808A2

2615161

0290468A9

3174741

3315859

0513314AX1C9

5558665

0677802A5/0677802BX

22.4

0.8366

21.6

0.8551

23.6

0.8103

22.9

0.8254

23.1

0.8211

25.8

0.8211

25.1

0.7661

26.6

0.7796

28.9

0.7114

22.7

0.8299

25.4

0.7738

26.8

0.7476

25.1

0.7796

22.2

0.8412

21.7

0.8528

23.2

0.8189

22.7

0.8299

22.7

0.8299

25.4

0.7738

25.2

0.7796

26.7

0.7494

28.9

0.7114

22.1

0.8435

25.3

0.7757

26.8

0.7476

25.1

0.7796

21.9

0.8481

21.9

0.8481

23.2

0.8189

22.8

0.8277

22.6

0.8321

25.2

0.7777

25 0.7816

26.7

0.7494

29.1

0.7082

22.4

0.8366

25.3

0.7757

26.5

0.753

25.1

0.7796

22.08

0.8439

21.4

0.8599

20.8

0.8745

22.1

0.8435

22.3

0.8389

25.2

0.7777

24.8

0.7856

24.9

0.7836

28.1

0.7248

21.4

0.8599

25 0.7816

26.6

0.7512

24.7

0.7876

Ca e Town D.F Malan

Geor e P.W. Botha

East London

Jan Smuts/Johannesbur

Int.

Port Elizabeth-WI<

Louis Bothal Durban

Bloemfontein JBM Hertzo

Kimberl

U

in ton

Bethlehem

Pretoria

Nels ruit-Friedenheim

Pietersbur

211790

286904

595729

0476398A3

351795

0240808AJ0240808A2

2615161

0290468A9

3174741

3315859

0513314AX1C9

5558665

0677802A5/0677802BX

21.8

0.8504

21.3

0.8623

23.2

0.8189

19.8

0.8999

22.4

0.8366

25.2

0.7777

24 0.8019

25.9

0.7642

28.1

0.7248

21.4

0.8599

24.6

0.7896

26.6

0.7512

24.7

0.7876

21.6

0.8551

21.2

0.8647

22.8

0.8277

22 0.8458

22.2

0.8412

24.9

0.7836

25.1

0.7796

26.5

0.753

28.9

0.7114

22.3

0.8389

25.2

0.7777

26.5

0.753

25 0.7816

21.7

0.8528

21.6

0.8551

23.5

0.8124

22.4

0.8366

22.8

0.8277

25.6

0.7699

24.3

0.7957

25.8

0.7661

28.4

0.7197

22.1

0.8435

25.2

0.7777

27 0.744

25.2

0.7876 -

21.4

0.8599

21.3

0.8623

24.6

0.7896

23.8

0.7896

22.4

0.8061

26.3

0.7567

24.5

0.7916

27.5

0.7351

31.5

0.6713

23.4

0.8146

26 0.7623

28

0.7265

Ca e Town D.F Malan

Gear e P.W. Botha

East London

Jan SmutslJohannesbur

Int.

Port Elizabeth-Wk

Louis Bothal Durban

Bloemfontein JBM Hertz

Kimberl

U in ton

Bethlehem

Pretoria

Nels ruit-Friedenheim

Pietersbur

211790

286904

595729

0476398A3

351795

0240808AJ0240808A2

2615161

0290468A9

3174741

3315859

0513314AX1C9

5558665

0677802A5/0677802BX

22.4

0.8366

21.6

0.8551

23.6

0.8103

22.8

0.8277

22.6

0.8321

26 0.7623

25.3

0.7757

26.4

0.7549

30 0.6939

22.3

0.8389

26 0.7623

27 0.744

22.4

0.8366

21.6

0.8551

23.9

0.804

21.9

0.8481

22.2

0.8412

25.4

0.7738

24.6

0.7896

26.4

0.7549

29.3

0.705

21.9

0.8481

25.1

0.7796

25.2

0.7777

25.3

0.7757

22.2

0.8412

21.1

0.8671

23.4

0.8146

22.4

0.8366

21.8

0.8504

24.8

0.7856

25 0.7816

26.6

0.7549

29.2

0.705

22 0.8481

25.1

0.7796

26.5

0.7777

25.6

0.7757

21.6

0.8551

21.6

0.8551

23 0.8232

21.8

0.8504

22.4

0.8366

24.9

0.7836

23.8

0.8061

25.3

0.7757

28 0.7265

20.6

0.8795

24.6

0.7896

26.3

0.7567

24.6

0.7896

Int.

211790

286904

595729

0476398A3

351795

0240808AJ0240808A2

2615161

0290468A9

3174741

3315859

0513314AX1C9

5558665

0677802A5/0677802BX

22.4

0.8366

21.7

0.8528

22.8

0.8277

21.7

0.8528

22.2

0.8412

24.6

0.7896

25.1

0.7796

26.1

0.7605

28.9

0.7114

21.2

0.8647

25.1

0.7796

23.3

0.8167

25.2

0.7777

-

22.5

0.8344

21.9

0.8481

23.5

0.8124

22.4

0.8366

22.5

0.8344

25.3

0.7757

25.2

0.7777

26.8

0.7476

29.7

0.6986

22.9

0.8254

26.7

0.7494

23.1

0.8211

26 0.7623

23.4

0.8146

22.6

0.8321

24.3

0.7957

22.2

0.8412

23.2

0.8189

26.2

0.7586

25.9

0.7642

27.4

0.7369

29.6

0.7002

22.6

0.8321

26.4

0.7549

26.9

0.7458

25 0.7816

INFORMATION ON THE SIMPLIFIED GEOLOGY OF

SOUTH AFRICA AND FLUORINE CONTAINING ROCKS

Table 29: Fluorine in intrusive and extrusive Igneous rocks.

'Tr' IS trace, All concentrations in mgIkg

Rock Type

Ultramafic

Gabbros

Diorites

Granites and Granodiorites

Syenite and monzonite

Alkaline ultramafic

Alkali syenite

Alkali granite

Carbonatites

Kimberlites

Dolerites

Pegmatites

Basalts

Andesites

Rhyolites

Trachvte and Latite

Min

Tr.

50

300

20

200

Tr.

100

670

200

520

198

800

20

Tr.

Tr.

200

Range

Max

Intrusive

2000

11000

1300

30000

4000

3800

25800

12400

24000

2500

500

9000

Extrusive

2400

1200

6850

2250

130

430

665

810

1360

1400

1800

5500

8100

1310

420

4320

375

250

610

750

Mean Number

41

249

20

96

42

14

6

37

47

20

182

26

317

97

151

9

Rock Type

Metagabbro

Schists

Amphibolite

Gneiss

Hornfels

Contact Skams

Greisens

Kaolinized Granite

Fenite

Range

Min

99

60

140

240

Metasomatic

26

700

1600

800

Tr.

7800

43500

20400

7400

600

Mean

Max

Regional

140

580

1400

2800

120

250

740

1030

1630

9780

9800

2800

400

Number

2

48

10

14

57

28

26

26

3

Rock Type

Range

Min

Max

Clastic

Mean

Shales, siltstones mudstones

Sandstones and Greywackes

Oceanic sediments and

10

10

100

Limestone

Dolomite

Phosphate Rock

Anhydrite and Gypsum

Rock salt

Tr.

110

10400

130

2

11 660 790

880

1600

180

640

Biogenic!

Chemical

1210 220

400

42000

890

6

260

30500

600

5

Number

98

14

74

6

4

141

49

151

Simpl

i

f

i

ed Geology of the Republic of Sout

h

Af

rica

( Including Les o th o and S w aziland )

The geological f ormati o ns illust ra ted on this map ran g e f r o m s o me of th e o ld est known on Earth, for examp l the Barberton Supergroup , to modern-da y deposits and sand dun e s o f th e K a lah ari .

M any rock types are fOUl in these geological formations.

Sedimentar y conglom e rates , sandstones and shal e f o r m l ar g e sections of tl

Witwatersrand , Cape and Karoo Supergroups ; limestones , dolomites and iron formati o n s occ u r i n th e Tr ansvo

Supergroup; metamorphic granulites , amphibolites and schists outcrop in the Limp o p o r eg ion , t h e Nor the

Cape Province and Namaqualand; ig n eous granites constitute parts of the Kaapvaal Craton i n th e Nort h e rn aJ

Eastern Transvaal Provinces; gabbros and other chrome-rich and platinum-rich igneous roc k s ar e f o und in t l

Bushveld Complex, and ancient volcanic lavas form the Ventersdorp Supergroup and the upperm o s t p o rti o n the Karoo Supergroup.

Adapted from the 1:4 million (1986) "Geological Map of Southern Africa ", Geo l o gi c

Society of South Africa .

ROCK TYPES

D

D

Recent cover

(sand , alluvium)

L ava

(basalt, rhyolite)

D

Sediments ( sandstone , shale, siltstone) .

and dolerite

~ediments

(sandstone, quartzite, shale)

STRATIGRAPHY

Quaternary, Tertiary

Karoo Supergroup

Cape Supergroup

AGE

( m i lli on y ear s)

0-65

150-300

3 20-500

MAIN MINERALS

Diamonds

Amethyst , agates , zeolit e s

F l uorite , prehnite , bar i te platinoids, g y psum

Manganese , go l d , t i n

D

Granite, sedime n ts

(l i mestone)

D

D

Meta-sediments, meta-volcanics

(gneisses, pegmat i tes, etc .

)

Sediments

(arkoses , conglomerate)

Igneous intrusions, etc.

(gabbro , "Red"g r anite, anorthosite)

D

Sediments (dolom i te, limestone iron-format i ons, shale, quartzite )

,

0

Lavas

(basalt , andesite, porphyry )

Cape granites, Malmesbury 5 00-600

Namaqua-Natal Region

Waterberg Group

Bushveld, Phalaborwa

Complexes

Transvaal Supergroup

Ventersdorp Group

600-1500

1 750-1 850

1900-2100

2200-2500

2500-2700

Tin, aragonite (ca v es)

Beryl, tantalite , corundum, lead-zinc copper, quartz

Tin, platinum, chromite , lead-zinc , andalusite , garnet , magnesite, zeoli l

Manganese , l ead-z i n c, ir o n , asbestos , "Tigers e y e ", jaspe ~

Agates

Limpopo Provin c e ±2700-3500

Copper , garne t, corundum , nic kel

D

Metamorphics

(gneisses, granulites, sch i st)

Sediments, volcan i cs

(quartzites , conglomerate, lava)

2700-3100

Gold , quartz, j asper

Witwatersrand , P o ngol a

Supergroups

Granites, tonalites , granitoids

Sediments, volcanics

(sandstones , conglomerate, komatiites, pyroxe n ites)

Ancient granitic crust

"Greenstones": Barberton

Murchison, Pietersburg

,

3000-3100

3000-3500

Tin, tantalite , cor u ndum beryl , emeralds

Gold , nickel , mercur y , antimony, copper-zinc, asbestos

I

D

I

I

:

I

" i

.0

\

\ .

\

~o

\~

Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement

Table of contents