Determination of the Origin of Heavy Metals in the Coffee (Espresso

Determination of the Origin of Heavy Metals in the Coffee
(Espresso) Making Process
Abstract: The objective of this experiment was to determine the amount of
lead and other metal contamination in an espresso sample from a café in Canada (Dark
Horse in downtown Toronto). Further aims were to determine which process (in coffee
making) contributes to the metal uptake: the city water, water heater, filter, espresso
machine or the beans. Acid digestion of solid samples along with ICP-AES was used to
determine metal concentrations. No lead was detected in any samples implying that
government regulations of lead are effective, but other metals (e.g. antimony) detected
are of concern and more studies should be conducted. The largest source of metals in the
coffee came from the city supplied water. The metals in the dry coffee grounds are
mostly of biological origin needed to sustain life, but coffee plants are able to absorb
heavy metals from a polluted land.
Introduction: Metals are widespread non-biodegradable contaminants found
in the environment because of either natural causes such as weathering of rocks or
anthropogenic activities of industrial production, fertilizer use and mining15. Heavy metal
pollution is a known cause of various disorders such as genomic instability, endocrine
disruption, neurological toxicity, carcinogenicity, immunological problems and impaired
psycho-social behaviour15. Lead is a highly toxic metal with the main routes of
incorporation into the body being through respiratory and digestive (through consumption
of contaminated food and water) mechanisms. Chronic poisoning with this metal leads to
a condition known as saturnism, which is characterized by severe anaemia, digestive,
cardiovascular, renal and nervous disorders15. Lead was estimated to account for 0.9% of
the total global disease burden, due to lead-induced mental retardation and consequences
of increased blood pressure2. The German Federal Institute for Risk Assessment (BfR)
has found that commercial espresso machines release significant quantities of heavy
metals such as lead, copper and nickel in customer’s drinks17. This is a risk hazard for
people who drink coffee, especially in the long term. The purpose of this experiment is to
determine the origin of heavy metals (especially lead) in a cup of coffee – does the heavy
metal originate from the city tap water, the resistive water heater used to warm the water,
the filter or the espresso machine used to make the espresso from coffee beans. Coffee is
the second most popular drink after water in the world2, but if large amounts of lead were
leaching into it from espresso machines then one would observe a health disaster in
society with lead in coffee expecting to add to this disease burden2. Nevertheless with the
strict guidelines regulating the use of lead in metal soldering in Canada, the hypothesis
going into this experiment is that one would not find any detectable amount of lead in
coffee in Toronto. The method that was used to detect lead and other heavy metals in the
experimental samples would be to use an ICP-AES machine. ICP stands for “inductively
coupled plasma” which is more than twice as hot as a combustion flame18. The high
temperature, stability and relatively inert argon environment eliminates much of the
interference encountered with flames. After a spark from a Tesla coil ionizes Ar, free
electrons are accelerated by a radio-frequency field. Electrons collide with atoms and
transfers energy to the entire gas, maintaining a temperature of 6000 to 10000 K. AES
means “atomic emission spectroscopy”18. ICP emission spectrometer does not require
any lamps and can measure as many as 70 elements simultaneously. Atomic emission
from excited metal atoms enters a polychromator and is then dispersed into its component
wavelengths by a grating18. After leaving the grating it is then reflected by a collimating
mirror (which makes light rays parallel), later it is dispersed in the vertical plane by a
prism, and then further dispersed in the horizontal plane by another grating18. Dispersed
radiation ultimately lands on a charge injection device (CID) detector, which is related to
the charge coupled device (CCD) to be recorded and processed for viewing18.
Materials and Methods: Seven different samples were taken to determine the
heavy metal contribution of each component in the coffee making process which are:
cold tap water, hot tap water, hot filtered water, coffee water (water that has run inside an
espresso machine), roasted beans, gunk (used coffee beans) and the drinkable liquid
espresso. The difference in each sample would give the heavy metal contribution from
each process (diagram 1). The dry samples (gunk and roasted ground coffee) were dried
to evaporate water to generate a mass/mass metal concentration. Three different types of
coffee were used: Ethiopian (roasted and gunk), decaffeinated (roasted and gunk) and
Punch Buggy (gunk). 4 grams were used for the roasted coffee and 8 grams was used for
the gunk (there would a lot of water evaporation). After each sample was dried in the
oven for 90 minutes, approximately 0.5 g of dried sample was digested in 10 mL
analytical grade nitric acid in a plastic digestion vessel in a Mars 6 microwave oven.
After digestion, the samples were eluted in a 25 mL flask and ultimately 5 mL were put
in a Falcon Tube to be used for the auto sampler of the ICP-AES machine. 5 mL water
samples were taken. They are: cold tap water (city water), hot tap water (heated with
resistive heater), hot filtered water (went through a stainless steel filter) and coffee water
(water than has run through the espresso machine). The liquid samples were filtered
before being put in the ICP-AES machine since large suspended particles can damage the
machine using 1 mL Norm-Ject Tuberkulin syringes and Chromatoprahic Specialties
Syringe filters (0.22 μm). For the two different (decaf and Ethiopian) liquid espresso
samples 0.45 μm (Fischerbrand PTFE) filters were used because 0.22 μm filters would
jam (high pressure build up) from the large amounts of floating matter in the concentrated
coffee. Ultimately 0.45 μm filters did not work for the decaf coffee, so gravity filtration
method was utilized (which was very time consuming and lead to unsuccessful results).
Earlier water samples were unable to detect any lead, so in the third day approximately
250 mL of coffee water and back flash water (coffee water from recently cleaned
espresso machine using Puly CaF) was boiled down to 20 mL to concentrate the metal
ions to have a greater chance of lead detection. Quality control components were a major
portion in the design of this experiment. For all samples 3 identical samples were run
(triplicates) and only the mean value was used. Furthermore, the ICP-AES instrument
gave the RSD and detection limits were provided from the ANALEST laboratory. Blanks
were run for the acid digestion using only analytical grade nitric acid and deionized water
was further boiled down from 250 mL to 20 mL. All glassware was used were all acid
washed for at a week for use. Finally 5 mL of all samples were put into a Perkin Elmer
Optima 7300 DV Optical Emission Spectrometer. The main reasons for using ICP-AES
instead of a graphite furnace-AAS method are as follows: (a) lower susceptibility to
chemical interferences because of higher temperatures, (b) good emission spectra results
for most elements under a single set of excitation conditions, (c) flames are less
satisfactory as atomic emission sources because optimum excitation condition vary
widely from element to element, (d) more energetic plasma sources permit determination
of low concentration of elements that form refractory compounds, (e) plasma emission
methods have concentration ranges of several orders of magnitude unlike absorption
methods and (f) emissions using CIDs are better than using hollow cathode tubes16.
Results and Discussion: After concentrating the water samples tenfold, no
lead was detected in any samples. This supports the hypothesis that government
regulation in Canada has almost eliminated it from everyday life and further questions the
validity and the methodology of the BfR. Even through no lead was detected, other
metals were detected (especially in the city tap water) such as aluminium, barium, boron,
calcium, magnesium, sodium, antimony, selenium, silicon and copper.
The cold tap water showed an aluminium concentration of 0.01 ppm. The
reason that aluminium was detected in tap water is because aluminium salts such as
aluminium sulphate (alum) and polyaluminum chloride (PACl) are used extensively as
coagulants in water treatment plants to enhance the removal of particulate, colloidal and
dissolved substances. They are the most widely used coagulants (instead of iron
compounds) because of their effectiveness, readily availability, and inexpensiveness8. In
Canada, a large proportion of water treatment facilities use aluminium-based coagulants
for their clarification treatment. According to Eaglebrook, which is a large coagulant
supplier of aluminium based coagulants in Canada, 97.2% of their Canadian clients
purify drinking water using aluminium-based coagulants5. Studies by other researchers
have shown that aluminium in Toronto’s drinking water ranged from 0.019 ppm to 0.29
ppm8. Even though, the detected value was lower than expected, a study has found that
high aluminium levels in drinking water (≥ 0.1 ppm) were associated with an elevated
risk of dementia and Alzheimer’s disease. To date, 13 epidemiological studies have been
done worldwide to investigate the hypothesis of a correlation between Alzheimer's
disease and increased concentrations of aluminium in drinking water and nine of these
studies have found a positive association8. Chronic toxicity of aluminum in drinking
water is also associated with severe diseases of the nervous system such as Parkinson's
disease and amyotrophic lateral sclerosis8. Other than water treatment, the presence of
aluminium in water distribution systems can be due to aluminium in the source water
itself and aluminium leached from distribution system materials such as pipes and
pumps8. Factors that may affect aluminium concentration in drinking water are
temperature, pH and the turbidity of water8. Furthermore aluminium concentrations are
dependent on the time of the year it is sampled when a different aluminium compound
(PASS) is used during the winter. PASS is most widely used for Canadian winters instead
of alum because when raw water is cold, chemical reactions are too slow. PASS (which
contains silicate, a mineral agent of polymerization) works better in cold conditions
because it instantly forms hydroxide aluminium flocs which adsorb contaminants on their
surfaces5.
The boron concentration found in tap water was 0.14 ppm. This is lower than
the interim maximum acceptable concentration (IMAC) for boron in Canada at 5 mg/L9.
Boron is a naturally-occurring element found in rocks, soil, and water. The concentration
of boron in the earth’s crust has been estimated to be <10 ppm, but concentrations as high
as 100 ppm can be found in boron-rich areas9. In natural waters, boron exists primarily as
undissociated boric acid with some borate ions10. The natural borate content of
groundwater and surface water is usually small which is present primarily as a result of
leaching from rocks and soils containing borates and borosilicates. Concentrations of
boron in groundwater throughout the world range widely, from less than 0.3 to greater
than 100 mg/litre10. Surface water concentrations of North America (Canada, USA)
ranged from 0.02 mg/litre to as much as 360 mg/litre, indicative of boron-rich deposits10.
Other than natural events, anthropogenic activities can greatly increase the boron
concentration in the water as a result of wastewater discharges (boron is not removed by
conventional drinking-water treatment methods) and through borate (raw material is boric
acid) compounds in domestic washing agents10. Boric acid is a very weak acid with a pKa
of 9.15, and therefore boric acid and the sodium borates exist predominantly as
undissociated boric acid B(OH)3 in dilute aqueous solution at pH <7; at pH >10, the
metaborate anion B(OH)4 becomes predominant. Between these two pH values, from 6 to
11, and at high concentration (>0.025 mol/litre), highly water soluble polyborate ions
such as B3O3(OH)4 , B4O5(OH)4, and B5O6(OH)4 are formed10. Boric acid and borates are
used in glass manufacture (fibreglass, borosilicate glass, enamel, frit, and glaze), flame
retardants, mild antiseptics, cosmetics, pharmaceuticals (as pH buffers), boron neutron
capture therapy (for cancer treatment), pesticides, and agricultural fertilizers10. There is a
large chance that when these materials are disposed improperly, boron leaches into the
water systems to be detectable through ICP-AES.
0.01 ppm of barium was detected in the tap water. Ba is an alkaline earth
element which occurs as a trace metal in igneous and sedimentary rocks. In nature it
occurs mainly as low soluble minerals such as barite (BaSO4) and witherite (BaCO3). Ba
solubilization and, consequently, the release of Ba2+ ions occur under specific conditions
such as in acidic conditions, in the absence of oxygen (due to algal blooms), or even due
to microbial action3.
The largest concentration of metal seen in the tap water sample is calcium (38.58
ppm). This is not unexpected because the largest source for water in Toronto is from
Lake Ontario in the Great Lakes-St Lawrence Lowlands physiographic region of
Canada19. This landscape is flat to rolling and limestone (calcium carbonate) sedimentary
rocks are found just below the surface19. Although calcium carbonate is insoluble, a small
amount of if dissolves when water passes over it and the average calcium ion
concentration in North America is approximately 5.3  10 4 M
20
, but the tap water
concentration of 1  10 3 M is almost twice that of a pristine water source. The main
reason for this elevated calcium ion concentration is anthropogenic de-icing of roads
during winter using calcium chloride salt.
The sodium ion concentration for the supplied water (15.95 ppm) is almost half as
large as the calcium ion concentration. This high sodium level in the tap water which is
primarily derived from a fresh water lake is an anomaly. The major possible source of
this is the de-icing salt (sodium chloride). In the metropolitan area of Toronto alone, an
annual average of 100,000 tonnes of de-icing salts are used to maintain bare pavement
conditions during winter months21. The majority of de-icing salts are transported by
highway runoff into roadside soils and adjacent streams towards Lake Ontario21.
0.05 ppm of antimony was detected in the cold tap water sample. Antimony is
a naturally occurring element and can exist in a variety of oxidation states13. It is present
in the aquatic environment as a result of rock weathering, soil runoff and anthropogenic
activities. Typical concentrations of dissolved antimony in unpolluted waters are less than
1 ug/l, however, in the proximity of anthropogenic sources, concentrations can reach up
to 100 times natural levels13. Antimony enters into the groundwater in the form of
complexes with humic acids. Depending on the geological environment and possible
pollution, groundwater may contain up to a few ng/ml of antimony. In EU countries, the
admissible concentration of antimony in drinking water is 10 ppb11. The emission of
antimony into the human environment appears to be exclusively the result of human
activity. Most emitted antimony is in the form of ATO, which is released as a result of
coal burning or with fly ash when antimony-containing ores are smelted12. Another
source of antimony in the water system is from PET plastics. These plastics were
originally manufactured as disposable water bottles, but later in their lifetime they are
recycled into pipes and other devices. Antimony has been shown to leach from PET
plastics22 and temperatures above 65ºC (during the summer) can promote antimony
leaching. USEPA and the Ontario Ministry of Environment and Health Canada regulate
antimony in municipal water at a maximum of 0.006 ppm (6 ppb). The reason that
antimony is in plastics is because PET is produced using antimony based catalysts such
as Sb2O322. The observed amount was almost 9 times this amount. This came from the
plastic Falcon tubes used to store the water sample prior to this experiment. Antimony is
regulated because it can cause severe health effects such as nausea, vomiting and
diarrhoea. Earlier research in Canada has shown that antimony concentration of water in
PET bottlers increased an average of 19% during storage23. In general groundwater is not
a major source of antimony because crustal rocks contain 0.5 ppm of antimony, while
pristine groundwater may contain as little as 2 ng/L Sb. On the other hand bottled water
typically contains several hundred ng/L Sb – mostly from leaching23. There is a large
chance that the majority of antimony in the tap water samples came from the plastic
Falcon Tube.
Depending on the geochemical surroundings the content of selenium in water
can vary from a few hundredth to thousands ng/ml11. The Toronto tap water sample
contained 0.08 ppm of selenium which is consistent with other experimental data.
Selenium, along with antimony and arsenic, is washed into the ground waters from
dumping grounds, especially from ashes left after coal combustion. However, a
comparison of selenium content in waters subjected to strong and weak anthropogenic
pressure has not revealed significant differences, which proves that urbanisation and
development of industry have little effect on the content of selenium in water11.
Water treatment is the main source of silicon detected in piped water (0.66
ppm). The filtration process of water adds silicon because raw water which is obtained
from rivers, lakes or streams contains a multitude of tiny particles. These small
suspended particles are composed of clay, and results from the erosion of soil, and rock
by either natural forces or due to ploughing the land for agriculture, mining, or
commercial or housing development. The suspended particles increase water’s turbidity,
and thereby reduce the ability of light to penetrate deeply. The largest of the particles
suspended in water are often removed from the water by simply filtering it using sand20.
After the cold tap water went through the resistive heater it was seen that the
calcium concentration decreased by 1.27 ppm which indicates accumulation of scale on
the resistive heater. Even through many other metals such as boron, antimony and
selenium also decreased, statistical tests show these values are not significantly different
though the decrease can also be attributed to the formation of scale with these metals.
Other metals showed a slight increase, and the reasons for these can also be attributed to
the dynamic nature of scaling and descaling that occurs when water is heated and
becomes turbulent. The same results were also observed for the water filter.
Even through no lead leached from the machine, after hot filtered water
entered the espresso machine, the antimony concentration increased by 0.07 ppm. This
value is a significant increase. Elemental antimony is an inflexible metal and therefore
has few technical uses. However, it forms very hard and technically interesting alloys
with copper, lead and tin12. Batteries, antifriction alloys, type-metal and cable sheathing
are the main products containing antimony. Antimony trioxide, SbO3, has many uses
including as a flame-proof retardant of textiles, papers, plastics and adhesives; as a paint
pigment, ceramic opacifier, catalyst, mordant and glass decolouriser13. There is a large
chance that antimony was used as a metal alloy or glass in the espresso machine and very
slight corrosion of the machine pipes occurs every time hot water flows through it for
more than ten hours everyday. Other than mechanical corrosion, in wet environments,
microorganisms attach to metals and colonise the surface to form biofilms producing an
environment at the biofilm/metal interface that is radically different from that of the bulk
medium in terms of pH, dissolved oxygen, and organic and inorganic species which leads
to electrochemical reactions to corrode metals. Autotrophic bacteria oxidise inorganic
compounds (e.g. Fe2+ and Mn2+) for energy14. The warm condition of the espresso
machine is a perfect candidate for microbial erosion.
For scientific purposes the use of known origin beans are preferred so the soil,
environment and climatic conditions are known (reason Ethiopian coffee beans were
scrutinized). The decaf coffee was excluded because of the unknown process of
decaffeinating and the Punch Buggy contained an unknown mixture of coffees. The
metals that stood out in the dry coffee were 0.20 ppm copper and 0.17 ppm boron. The
copper concentration can be attributed to the slow roasting process in a pot containing
copper, but the boron concentration in the coffee plants can to traced to the essential
requirement of boron for plant growth for all vascular plants whose deficiency causes
impairments in several metabolic and physiological processes1. To date, one of the
primary functions of boron in vascular plants has been related to the cell wall structure
and function. There is direct evidence for a role of boron in cross-linking the cell wall
proteins rhamnogalacturonan II (RGII) and pectin assembly1. Boron deficiency decreases
the growth of both vegetative and reproductive plant parts1. Boron is never found in its
elemental form in nature, but is found in rocks as borates, i.e. bound to oxygen together
with sodium, calcium, silicon, or magnesium and will usually be hydrated1. In soils,
boron movement follows the water flux; hence, in cool humid climates soil boron is
leached downward in soil profiles, whereas in soils of warm humid, or arid and semiarid
regions, boron is likely to concentrate in surface horizons1. Ethiopia is a warm country
and this explains the high concentration of boron in the coffee beans. The dry coffee
beans also showed 0.16 ppm of barium which is present because of soil pollution (a
serious problem in many countries around the world3). Recently, it was observed that
successive sewage sludge applications increased soil Ba concentration and accumulation
in maize plants grown in Brazil and there is a large chance that the same process occurs
in coffee plants as well3. Ethiopia being an underdeveloped country most likely uses
sewage sludge as a fertiliser in lieu of other types (e.g. urea).
The Ethiopian coffee gunk showed aluminium concentration of 0.59 ppm. The
cause of this can be twofold: during the process of drying the wet gunk in a oven or the
accumulation of large amounts of aluminium from water. Aluminium often binds
strongly with other substances in food such as fluoride and phosphate, which may make it
less absorbable in water6. The aluminium leaching is five times higher at 100ºC
than at ambient temperature; at 185ºC (oven) the leaching is even more and the
aluminium intake is more than eight times than that at 100ºC. As the temperature
increases, the kinetic energy is higher and the movement of molecules becomes faster
therefore, aluminium contaminates food more frequently in an oven6. Furthermore the
aluminium intake at temperatures below 100ºC are less than that in drinking water, while
at 100ºC the aluminium intake is three times more than that in drinking water6 again
proving that the oven was the source of aluminium. The drying time and temperature has
also a significant effect on aluminium leaching from the drying apparatus to the food
solution6.
In the future this experiment can be improved further by using vacuum
filtration for coffee and disassembling the espresso machine to determine the composition
of the alloys to see which metals are actually leaching. This can be done by spark or arc
source emission spectroscopy16. Though ICP-AES method provided the best choice for
this experiment, ICP-MS could be used in the future because in certain circumstances has
provided better detection limits but also has these following limitations: (a) isobaric
interferences, (b) polyatomic ion interferences and (c) oxide and hydroxide specific
interferences16.
Conclusion: Fortunately for the consumer in Toronto, no lead was detected in
any samples indicating that coffee is a safe beverage. Even though no lead was seen, the
Toronto tap water showed traces of aluminium, antimony and selenium which is of
concern. Furthermore this experiment saw possible traces of antimony leaching from
plastics. The biggest source of metals in coffee is tap water itself, though some minimal
levels of metals from the espresso machine was detected possibly because of corrosion.
Works Cited
[1] Herrera-Rodriguez M. Role of Boron in Vascular Plants and Response Mechanisms to
Boron Stresses. Plant Stress 2010; 4: 115-122.
[2] Nędzarek A. Concentrations of heavy metals (Mn, Co, Ni, Cr, Ag, Pb) in coffee. Acta
Biochimica Polonica 2013; 4: 623-627.
[3] Abreu C. Organic Matter and Barium Absorption by Plant Species Grown in an Area
Polluted with Scrap Metal Residue. Applied and Environmental Soil Science 2012; 1: 1-7.
[4] Inter-Celtic Colloquium on Hydrology and Management of Water Resources. 2005.
Aluminum contents in drinking water from public water supplies of Galicia.
[5] Niquette P. Impacts of Substituting Aluminum-Based Coagulants in Drinking Water
Treatment. Water Qual. Res. J. Canada 2004; 39: 303-310.
[6] Mohammad F. A comparison of Aluminum Leaching Processes in Tap and Drinking
Water. International Journal of ELECTROCHEMICAL SCIENCE 2014; 9: 3118-3129.
[7] Toronto Public Health. Chemicals in Drinking Water. March 2001.
[8] Dzulfakar M. Risk Assessment of Aluminum in Drinking Water between Two
Residential Areas. Water 2011; 3: 882-893.
[9] Salman T. The measurements of boron concentration rate in water using curcumin
method and SSNTDs Techniques. Advances in Applied Science Research 2013; 4: 105112.
[10] World Health Organization. Boron in Drinking Water. 2003.
[11] Niedzielski P. Total Content of Arsenic, Antimony and Selenium in Groundwater
Samples from Western Poland. Polish Journal of Environmental Studies 2001; 10: 347350.
[12] Word Health Organization. Antimony in Drinking Water. 2003.
[13] Filella M. Antimony in the environment: a review focused on natural waters I.
Occurrence. Earth-Science Reviews 2002; 57: 125–176.
[14] Little B. Microbiologically influenced corrosion of metals and alloys. International
Materials Reviews 1991; 36: 253-272.
[15] Talio M. Sequential determination of lead and cobalt in tap water and foods samples
byfluorescence. Talanta 2014; 127: 244–249.
[16] Skoog, D. A.; Holler, F. J.; Nieman, T. A., Principles of Instrumental Analysis.
Saunders College Pub.: 1998.
[17] BfR Frequently asked questions about the release of lead from coffee and espresso
machines.
http://www.bfr.bund.de/en/frequently_asked_questions_about_the_release_of_lead_from
_coffee_and_espresso_machines-188868.html (accessed October 2014).
[18] Harris, D. C., Quantitative Chemical Analysis. W. H. Freeman: 2010.
[19] Bone R. The Regional Geography of Canada. Oxford, 2014.
[20] Baird C. Environmental Chemistry. W.W. Freeman and Company, 2012.
[21] Sadowski E. The impacts of chloride concentrations on wetlands and amphibian
distribution in the Toronto region. Prairie Perspectives 1999; 1: 144-162.
[22] Westerhoff P. Antimony leaching from polyethylene terephthalate (PET) plastic
used for bottled drinking water. WATER RESEARCH 2008; 2008: 551– 556.
[23] Shotyk W. Contamination of Bottled Waters with Antimony Leaching from
Polyethylene Terephthalate (PET) Increases upon Storage. Environ. Sci. Technol. 2007;
41: 1560-1563.
Appendix:
Diagram 1:
A schematic of the route that tap-water takes to produce a cup of coffee.
Cold tap
water
Hot tap
water
Resistive
heater
Hot filtered
water
Coffee
water
Coffee
(espresso)
machine
Filter
Coffee Drink
(espresso)
Dry
ground
roasted
coffee
Used (gunk)
ground
coffee
Equation 1:
Heavy metal concentrations of coffee, gunk, coffee water and dry ground coffee.
[ Metal ]coffee _ water  [ Metal ] dry _ ground _ roasted _ coffee  [ Metal ]used _( gunk ) _ ground _ coffee  [ Metal ]coffee _ drink _( espresso)
Mean Metal Concentrations:
*Only samples from day 1 of the experiment were analyzed for consistency and adjusted
for blanks. All amounts in ppm
Chart 1: Water Samples
Metal
Cold tap water
(city water
from Toronto)
Al
0.01
B
0.14
Ba
0.01
Ca
38.58
Mg
10.11
Hot tap water
Hot filtered
water
Coffee water
0.01
0.09
0.02
37.31
10.22
0.01
0.04
0.02
37.90
10.41
0.02
0.02
0.02
36.48
10.27
Na
Sb
Se
Si
Cu
15.95
0.05
0.08
0.66
16.01
0.07
16.13
0.04
16.57
0.11
0.69
0.70
0.67
0.01
Chart 2: Metal Addition from Each Component
Metal
Al
B
Ba
Ca
Mg
Na
Sb
Se
Si
Cu
Heater
0
-0.05
0.01
-1.27
0.11
0.06
0.02
-0.08
0.03
0.02
Filter
0
-0.05
0
0.59
0.19
0.12
-0.03
0
0.01
0
Machine
0.01
-0.02
0
-1.42
-0.14
0.44
0.07
0
-0.03
-0.02
Chart 3: Dry Samples (Ethiopian). 0.5 g of dried sample was digested in 10 mL analytical
grade nitric acid; adjusted for blanks. Units are μg/mL.
Metal
Al
B
Ba
Ca
Mg
Na
Sb
Se
Si
Cu
Fe
Mn
Zn
Co
Tl
Dry
0.04
0.06
13.83
27.09
Gunk
0.22
0.02
0.28
27.71
27.47
1.14
0.03
0.20
0.12
0.23
0.02
0.69
0.47
0.79
0.90
0.19
0.01
0.06
Chart 4: Dry sample adjusted for mass and volume (ppm) (mass/mass) (μg/mg)
 1 
 0.04 g 

Calculation example: 
10mL 
 mL 
 500mg 
Metal
Al
B
Ba
Ca
Mg
Na
Sb
Se
Si
Cu
Fe
Mn
Zn
Co
Tl
Dry
Gunk
0.0044
0.0004
0.0056
0.5542
0.5494
0.0228
0.008
0.0012
0.2766
0.5418
0.0006
0.0138
0.0094
0.0158
0.018
0.038
0.0002
0.0012
0.004
0.0024
0.0046
0.0004
Chart 5: Results for day 1 and day 2
Cold Hot
Met tap
tap
al water water
(µg/m (µg/m
L)
L)
Detecte
B
N/A
d
Ba 0.0221 N/A
41.649 41.583
Ca
2
4
11.006 11.274
Mg
5
7
17.872 17.556
Na
4
9
Si 0.6184 0.6746
Cu N/A
N/A
Fe N/A
N/A
Mn N/A
N/A
Zn N/A
N/A
Al N/A
N/A
Filtere
d cold
water
(µg/m
L)
Filtere
d hot
water
(µg/m
L)
Dry
Punch
Espress Dry
Decaf
Ethiopia
Ethiopia
Buggy
o water Decaf Gunk
n Gunk
n
Gunk
(µg/mL (µg/m (µg/m
(µg/m
(µg/mL) (µg/mL)
)
L)
L)
L)
N/A
0.1445 0.0851
0.0236
41.005
6
10.618
0
17.106
2
0.6204
N/A
N/A
N/A
N/A
N/A
0.0265
42.970
5
11.521
5
18.239
8
0.7019
N/A
N/A
N/A
N/A
N/A
0.3512 0.3634 0.3001
N/A
0.1618
21.001
37.3114
8
37.717
10.2168
4
0.3020
0.2296 0.0816 0.1563
25.296
19.3059 23.1509
2
26.769
37.0640 31.0983
9
0.2801
0.1379
24.174
7
33.764
3
16.0121 0.3766 1.2771 0.6998
0.9298
0.7010
0.6931
N/A
N/A
N/A
N/A
N/A
0.8571
0.3772
2.0325
0.4304
0.5715
0.8498
0.9970
0.3564
1.6326
0.4530
0.3451
0.8014
0.3153
0.3016
0.7562
0.8430
N/A
N/A
0.6820
0.4556
1.0947
0.7055
0.3045
N/A
0.1761
0.2960
0.6988
0.3076
N/A
N/A
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