Screening Assessment 3′,4′:6,7]naphtho[2,3-d]-1,3-dioxol-6(5aH)-one, 9- Furo[

Screening Assessment 3′,4′:6,7]naphtho[2,3-d]-1,3-dioxol-6(5aH)-one, 9- Furo[
Screening Assessment
Furo[3′,4′:6,7]naphtho[2,3-d]-1,3-dioxol-6(5aH)-one, 9[[4,6-O-(1R)-ethylidene-β-D-glucopyranosyl]oxy]5,8,8a,9-tetrahydro-5-(4-hydroxy-3,5dimethoxyphenyl)-, (5R,5aR,8aR,9S)(Etoposide)
Chemical Abstracts Service Registry Number
33419-42-0
Environment Canada
Health Canada
February 2015
Screening Assessment - Etoposide
Cat. No.: En14-213/2015E-PDF
ISBN 978-1-100-25660-3
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Screening Assessment - Etoposide
Synopsis
Pursuant to section 68 of the Canadian Environmental Protection Act, 1999 (CEPA
1999), the Ministers of the Environment and of Health have conducted a screening
assessment of the substance furo[3′,4′:6,7]naphtho[2,3-d]-1,3-dioxol-6(5aH)-one, 9[[4,6-O-(1R)-ethylidene-β-D-glucopyranosyl]oxy]-5,8,8a,9-tetrahydro-5-(4-hydroxy-3,5dimethoxyphenyl)-, (5R,5aR,8aR,9S)-, Chemical Abstracts Service Registry Number
33419-42-0. This substance will be referred to by its common name, etoposide.
Etoposide was identified as a priority for assessment because it had been identified as
posing a high hazard to human health based on classifications by other national or
international agencies for carcinogenicity.
Drugs containing etoposide as an ingredient are assessed under the Food and Drugs
Act (F&DA) with respect to their safety, effectiveness and quality. This assessment
focused on uses and exposures that were not covered as part of the F&DA assessment,
specifically the risks posed by the residues resulting from manufacture, formulation and
disposal after use.
Etoposide is an organic substance, derived from the laboratory transformation of the
root of the mayapple tree (Podophyllum peltatum), that is registered for use in Canada
as a chemotherapeutic agent for the treatment of small lung tumours and testicular
cancer. A total of 23 kg of etoposide was sold to hospitals and pharmacies across
Canada in 2012.
Based on etoposide’s chemotherapeutic use in humans, a small amount of this
substance may be released to wastewater systems after passing through the human
gastrointestinal tract or renal system. Etoposide has moderate solubility in water,
minimal volatility and no tendency to partition to lipids of organisms. Due to these
physical and chemical properties, etoposide is expected to reside predominantly in
water and soil, depending on the compartment of release. Empirical and modelled data
suggest that etoposide has the potential to persist in water, soil and sediment.
Etoposide has low bioaccumulation potential based on a qualitative assessment of its
physical and chemical properties (i.e., high molecular weight, low octanol–water partition
coefficient [log Kow]) and the high potential for fish to metabolize and readily excrete
etoposide.
Based on empirical and modelled effects data, etoposide is expected to be moderately
toxic to organisms in the aquatic environment. There are indications that etoposide may
induce genotoxicity and affect endocrine function in mammals and aquatic organisms.
To account for these sublethal effects, which would not be detected by standard acute
toxicity tests, a high assessment factor was selected to determine the predicted noeffect concentration (PNEC), given that these effects often have an impact at the
population level rather than at the organism level.
Screening Assessment - Etoposide
For the ecological assessment, realistic, conservative exposure scenarios were selected
for the aquatic environment based on expected releases for a site-specific industrial
operation and for down-the-drain releases of the substance. The predicted
environmental concentrations in water were below the PNEC calculated for aquatic
organisms.
Considering all available lines of evidence presented in this screening assessment,
there is low risk of harm to organisms or to the broader integrity of the environment from
etoposide. It is therefore concluded that etoposide does not meet the criteria under
paragraph 64(a) or 64(b) of CEPA 1999, as it is not entering the environment in a
quantity or concentration or under conditions that have or may have an immediate or
long-term harmful effect on the environment or its biological diversity or that constitute or
may constitute a danger to the environment on which life depends.
In terms of general population exposure, the principal potential source of exposure is
drinking water containing the pharmaceutical. The exposure to etoposide present in
drinking water is significantly smaller than the exposure to etoposide through its use as
a pharmaceutical.
For this assessment, conservative assumptions were used when estimating the potential
indirect exposure of the general population to etoposide. Etoposide was not detected in
samples taken from wastewater treatment plant influent and effluent at six plants across
Canada. Upper-bounding estimated intakes of environmental residues based on the
detection limit from that study and on modelled surface water concentrations were very
low (< 1.5 ng/kg body weight per day). Based on low exposures, risks from these
substances are not expected. To further support this risk characterization, the upperbounding estimated indirect exposures of the general population were compared with
the lowest therapeutic dose. The margins of exposure ranged from > 2 000 000 to
3 000 000.
Based on the adequacy of the margins of exposure, it is concluded that etoposide does
not meet the criteria under paragraph 64(c) of CEPA 1999, as it is not entering the
environment in a quantity or concentration or under conditions that constitute or may
constitute a danger in Canada to human life or health.
Conclusion
It is concluded that etoposide does not meet any of the criteria set out in section 64 of
CEPA 1999.
Screening Assessment - Etoposide
Table of Contents
1.
2.
3.
4.
5.
6.
7.
Introduction ............................................................................................................... 1
Substance Identity .................................................................................................... 2
Physical and Chemical Properties .......................................................................... 4
Sources and Uses..................................................................................................... 7
Releases to the Environment .................................................................................. 8
Measured Environmental Concentrations ............................................................ 10
Environmental Fate ................................................................................................ 12
7.1 Metabolites ........................................................................................................ 12
7.2 Modelling Results .............................................................................................. 12
7.3 Environmental Persistence ............................................................................... 14
7.3.1 Empirical data ........................................................................................ 14
7.3.2 Modelling results .................................................................................... 15
7.3.3 Conclusion on persistence ..................................................................... 17
7.4 Potential for Bioaccumulation............................................................................ 18
7.4.1 Metabolism and elimination .................................................................... 18
7.4.2 Estimating BCF and BAF ....................................................................... 19
7.4.3 Conclusion on bioaccumulation potential ............................................... 21
8. Potential to Cause Ecological Harm ..................................................................... 21
8.1 Ecological Effects Characterization ................................................................... 21
8.1.1 Mode of action........................................................................................ 21
8.1.2 Empirical aquatic toxicity data ................................................................ 21
8.1.3 Mechanisms of toxicity ........................................................................... 23
8.1.4 Potential for genotoxicity ........................................................................ 23
8.1.5 Other ecological effects.......................................................................... 24
8.1.6 Modelled aquatic toxicity results............................................................. 25
8.1.7 Derivation of the PNEC .......................................................................... 26
8.2 Ecological Exposure Assessment ..................................................................... 27
8.2.1 Industrial release .................................................................................... 27
8.2.2 Down-the-Drain Releases from Pharmaceutical Use ............................. 28
8.3 Characterization of Ecological Risk ................................................................... 29
8.4 Uncertainties in Evaluation of Ecological Risk .................................................. 31
9. Potential to Cause Harm to Human Health ........................................................... 32
9.1 Uncertainties in Evaluation of Risk to Human Health ........................................ 35
10.Conclusion ............................................................................................................. 36
References .................................................................................................................. 37
Appendix A: Robust Study Summaries .................................................................... 45
Appendix B: PBT Model Input Summary Tables ...................................................... 55
Screening Assessment - Etoposide
Tables and Figures
Table 2-1: Substance identity: etoposide ................................................................ 2
Table 3-1: A summary of the physical and chemical properties of etoposide ......... 4
Table 5-1: Summary of the estimated percent release to compartments resulting
from different life cycle stages for etoposidea. ....................................... 9
Table 7-1: Summary of the Level III fugacity modelling (EQC 2003) indicating the
percentage of etoposide partitioning into each compartment .............. 13
Table 7-2: Empirical data for degradation of etoposide......................................... 15
Table 7-3: Modeled data for degradation of etoposide.......................................... 15
Table 7-4: Summary of modelled data for bioaccumulation of etoposide.............. 19
Table 8-1: Empirical aquatic toxicity data for etoposide ........................................ 21
Table 8-2: Empirical genotoxicity data for etoposide............................................. 24
Table 8-3: Modelled acute aquatic toxicity data for etoposide .............................. 25
Table 8-4: Summary of input values used for estimating aquatic concentrations
resulting from industrial releases of etoposide from the pharmaceutical
industry................................................................................................ 28
Table 8-5: Summary of the input values used for estimating aquatic concentrations
resulting from use of pharmaceuticals containing etoposide ............... 29
Table A-1: Scoring grid for overall study reliability ................................................ 45
Table A.2: Robust study summary for log Kow (Shah et al. 1989) ........................ 46
Table A.3: Robust study summary for water solubility (Shah et al. 1995) ............. 47
Table A.4: Robust study summary for persistence in water (Shah et al. 1995)..... 48
Table A.5: Robust study summary for aquatic toxicity (Zounková et al. 2007)...... 51
Table B.1: PBT model input summary table for physical-chemical models ........... 55
Table B.2: PBT model input summary table for fate modelling ............................. 55
Table B.3: PBT model input summary table for PBT profiling and ecotoxicity ...... 57
Screening Assessment - Etoposide
1. Introduction
Pursuant to section 68 of the Canadian Environmental Protection Act, 1999 (CEPA
1999) (Canada 1999), the Minister of the Environment and the Minister of Health
conduct screening assessments of substances to determine whether these substances
present or may present a risk to the environment or to human health.
A screening assessment was undertaken on the substance furo[3′,4′:6,7]naphtho[2,3-d]1,3-dioxol-6(5aH)-one, 9-[[4,6-O-(1R)-ethylidene-β-D-glucopyranosyl]oxy]-5,8,8a,9tetrahydro-5-(4-hydroxy-3,5-dimethoxyphenyl)-, (5R,5aR,8aR,9S)-, Chemical Abstracts
Service Registry Number (CAS RN) 33419-42-0. This substance will be referred to by its
common name, etoposide. Etoposide was identified as a priority for assessment
because it had been identified as posing a potential high hazard to human health based
on classifications by other national or international agencies for carcinogenicity. This
substance did not meet the ecological categorization criteria for persistence or
bioaccumulation potential, but it was categorized as being inherently toxic to aquatic
organisms.
Screening assessments focus on information critical to determining whether a substance
meets the criteria as set out in section 64 of CEPA 1999. Screening assessments
examine scientific information and develop conclusions by incorporating a weight of
evidence approach and using precaution. 1
This screening assessment includes consideration of information on chemical
properties, environmental fate, hazards, uses and exposure. Relevant data were
identified up to March 2013. Key studies were critically evaluated, along with modelled
results, to reach conclusions. When available and relevant, information presented in risk
and hazard assessments from other jurisdictions was considered. The screening
assessment does not represent an exhaustive or critical review of all available data.
Rather, it presents the most critical studies and lines of evidence pertinent to the
conclusion.
Drugs containing etoposide as an ingredient are assessed under the Food and Drugs
Act (F&DA) (Canada 1985) with respect to their safety, effectiveness and quality. This
assessment focused on uses and exposures that were not covered as part of the F&DA
1
A determination of whether one or more of the criteria of section 64 are met is based upon an assessment of
potential risks to the environment and/or to human health associated with exposures in the general environment. For
humans, this includes, but is not limited to, exposures from ambient and indoor air, drinking water, foodstuffs, and the
use of consumer products. A conclusion under CEPA 1999 on the substances in the Chemicals Management Plan
(CMP) is not relevant to, nor does it preclude, an assessment against the hazard criteria for the Workplace Hazardous
Materials Information System (WHMIS) that are specified in the Controlled Products Regulations for products
intended for workplace use. Similarly, a conclusion based on the criteria contained in section 64 of CEPA 1999 does
not preclude actions being taken under other sections of CEPA 1999 or other Acts.
Screening Assessment - Etoposide
assessment, specifically the risks posed by the residues resulting from manufacture, use
and disposal.
The screening assessment was prepared by staff in the Existing Substances programs
at Health Canada and Environment Canada and incorporates input from other programs
within these departments. The ecological and human health portions of this assessment
have undergone external written peer review and/or consultation. Comments on the
technical portions relevant to the environment were received from Chris Metcalfe, Trent
University and Vance Trudeau, University of Ottawa. Comments on the approach used
to assess the substance with respect to human health were received from Warren
Foster, McMaster University, Sam Kacew, McLaughlin Centre for Population Health Risk
Assessment, and Beate Escher, University of Queensland. Additionally, the draft of this
screening assessment was subject to a 60-day public comment period. While comments
were taken into consideration, the final content and outcome of the screening
assessment remain the responsibility of Health Canada and Environment Canada.
The critical information and considerations upon which the screening assessment is
based are summarized below.
2. Substance Identity
For the purposes of this document, the substance furo[3′,4′:6,7]naphtho[2,3-d]-1,3dioxol-6(5aH)-one, 9-[[4,6-O-(1R)-ethylidene-β-D-glucopyranosyl]oxy]-5,8,8a,9tetrahydro-5-(4-hydroxy-3,5-dimethoxyphenyl)-, (5R,5aR,8aR,9S)-, will be referred to as
etoposide, its common name.
Etoposide can be manufactured as a pure substance (CAS RN 33419-42-0) or as a
more soluble pharmaceutical product, etoposide phosphate (CAS RN 117091-64-2).
Etoposide and etoposide phosphate are both available commercially as pharmaceutical
products for human consumption. Although the pharmaceutical products contain 1%
ethanol for solubilization purposes, studies using the chemical grade as well as studies
using the drug product are presented in the text.
For the purpose of this screening assessment, both forms of etoposide are treated
equally. Etoposide phosphate is not expected to be found in the environment, as the
substance is rapidly transformed in the human body after the drug is injected. Therefore,
the presence of the phosphate is generally omitted from the discussion, given that its
function is predominantly pharmacokinetic and it is not expected to contribute to the
toxicity or to the exposure pathway of etoposide.
The substance identity information on etoposide is presented in Table 2-1.
Table 2-1: Substance identity: etoposide
CAS RN
33419-42-0
Furo[3′,4′:6,7]naphtho[2,3-d]-1,3-dioxol-6(5aH)-one, 9-[[4,6-O-(1R)DSL name
ethylidene-β-D-glucopyranosyl]oxy]-5,8,8a,9-tetrahydro-5-(4-hydroxy-
Screening Assessment - Etoposide
NCI names
Other
names
Chemical
group
(DSL
stream)
Major
chemical
class or
use
Chemical
formula
3,5-dimethoxyphenyl)-, (5R,5aR,8aR,9S)Etoposide (EINECS, REACH); Furo[3′,4′:6,7]naphtho[2,3-d]-1,3-dioxol6(5aH)-one, 9-[(4,6-O-ethylidene-β-D-glucopyranosyl)oxy]-5,8,8a,9tetrahydro-5-(4-hydroxy-3,5-dimethoxyphenyl)-, [5R[5a,5ab,8aa,9b(R*)]]- (AICS); Furo[3′,4′:6,7]naphtho[2,3-d]-1,3-dioxol6(5aH)-one, 9-[[4,6-O-(1R)-ethylidene-β-D-glucopyranosyl]oxy]5,8,8a,9-tetrahydro-5-(4-hydroxy-3,5-dimethoxyphenyl)-,
(5R,5aR,8aR,9S)- (ASIA-PAC, NZIoC)
(−)-Etoposide; 4′-Demethyl-1-O-[4,6-O-(ethylidene)- β-Dglucopyranosyl]epipodophyllotoxin; 4′-Demethylepipodophyllotoxin 9(4,6-O-ethylidene-β-D-glucopyranoside); 4′-Demethylepipodophyllotoxin
ethylidene-β-D-glucoside; Celltop; EPE; Epipodophyllotoxin VP 16213;
Epipodophyllotoxin, 4′-demethyl-, 4,6-O-ethylidene-b-Dglucopyranoside; Eposin; Eto-Gry; Etosid; Furo[3′,4′:6,7]naphtho[2,3-d]1,3-dioxol-6(5aH)-one, 9-[(4,6-O-ethylidene-β-D-glucopyranosyl)oxy]5,8,8a,9-tetrahydro-5-(4-hydroxy-3,5-dimethoxyphenyl)-, [5R[5a,5ab,8aa,9b(R*)]]-; Fytosid; Lastet; NSC 141540; Toposar; transEtoposide; VePesid; Vepesid J; VP 16; VP 16 (pharmaceutical); VP 16123; VP 16-213; Zuyeyidal
Organic
Pharmaceuticals
C29H32O13
Screening Assessment - Etoposide
Chemical
structure
SMILES
O1C2COC(C)OC2C(O)C(O)C1OC3C4COC(=O)C4C(c5cc(OC)c(O)c(O
C)c5)c6cc7OCOc7cc36
Molecular
mass
588.56 g/mol
Abbreviations: AICS, Australian Inventory of Chemical Substances; ASIA-PAC (Asia-Pacific Substances Lists; CAS
RN, Chemical Abstracts Service Registry Number; DSL, Domestic Substances List; EINECS, European Inventory of
Existing Commercial Chemical Substances; NCI, National Chemical Inventories; NZIoC, New Zealand Inventory of
Chemicals; REACH, Registration, Evaluation, Authorisation and Restriction of Chemical Substances; SMILES,
simplified molecular input line entry system
Source: NCI (2009)
3. Physical and Chemical Properties
A summary of experimental and modelled physical and chemical properties of etoposide
that are relevant to its environmental fate and ecotoxicity is presented in Table 3-1. Key
studies from which experimental data were reported for some of these properties were
critically reviewed for validity. Results from these reviews (robust study summaries
[RSS]) are found in Appendix A.
Models based on quantitative structure–activity relationships (QSARs) were used to
generate data for some of the physical and chemical properties of etoposide. These
models are based mainly on fragment addition methods; that is, they sum the
contributions of sub-structural fragments of a molecule to make predictions for a
property or endpoint. Most of these models rely on the neutral form of a chemical as
input.
Table 3-1: A summary of the physical and chemical properties of etoposide
Screening Assessment - Etoposide
Property
Physical form
Type
Valuea
Temperature
(°C)
Reference
NA
White
crystalline
powder
NA
Gennaro
1995
236–251°C
(mean value
used for
modelling
purposes:
244°C*)
NA
Keller-Juslén
et al. 1971
Melting point (ºC) Experimental
Melting point (ºC)
Modelled
263
NA
Melting point (ºC)
Modelled
334
NA
Boiling point (ºC)
Modelled
759
NA
Density (kg/m3)
Modelled
1.55 × 103
NA
ACD/Percept
a ©1997–
2012
MPBPWIN
2008
MPBPWIN
2008
ACD/Percept
a ©1997–
2012
7.20 × 10–21
Vapour pressure
(Pa)
Modelled
Vapour pressure
Modelled
(Pa)
Henry’s Law
constant
(Pa·m3/mol)
Henry’s Law
constant
(5.40 × 10–23
mmHg)
9.77 × 10−20*
−22
(7.32 × 10
mmHg)
1.77 × 10–25
25
ChemIDplus
1993–
25
MPBPWIN
2008
Estimated
(1.75 × 10–30
atm·m3/mol)
1.12 × 10–19
25
Meylan and
Howard 1991
Modelled
(6.04 × 10–24
atm·m3/mol)
25
HENRYWIN
2008
Estimated
0.6*
NA
Hansch et al.
1995
Experimental
1.0b
25
Shah et al.
1989
(Pa·m3/mol)
Log Kow
(dimensionless)
Log Kow
Screening Assessment - Etoposide
Property
Type
Valuea
Temperature
(°C)
Reference
Modelled
0.04
NA
KOWWIN
2008
(dimensionless)
Log Kow
(dimensionless)
Log Kow
Modelled
0.28
NA
ACD/Percept
a ©1997–
2012
Modelled
1.03
NA
FASS 2011
Modelled (from
MCI)
2.29
NA
KOCWIN
2009
Modelled (from
Kow)
0.28
NA
KOCWIN
2009
Estimated
from Kow and a
regressionderived
equation
described in
Lyman et al.
(1990)
1.71
NA
HSDB 1983–
(dimensionless)
Log Kow
(dimensionless)
Log Koc
(dimensionless)
Log Koc
(dimensionless)
Log Koc
(dimensionless)
Log Koc
Modelled
1.53
NA
ACD/Percept
a ©1997–
2012
Experimental
93.8*
Room
temperature
Shah et al.
1995
Experimental
150
37
Du and
Vasavada
1993
Estimated
58.7
25
Meylan et al.
1996
Modelled
105.7
NA
WSKOWWIN
2008
(dimensionless)
Water solubility
(mg/L)
Water solubility
(mg/L)
Water solubility
(mg/L)
Water solubility
Screening Assessment - Etoposide
Property
Type
Valuea
Temperature
(°C)
Reference
Modelled
~30
NA
Gennaro
1995
Modelled
13.25
NA
KOAWIN
2008
Experimental
9.8
NA
O’Neil 2001
Modelled
9.9
NA
ACD/Percept
a ©1997–
2012
(mg/L)
Water solubility
(mg/L)
Log Koa
(dimensionless)
pKa
(dimensionless)
pKa
(dimensionless)
Abbreviations: Koa, octanol–air partition coefficient; Koc, organic carbon–water partition coefficient; Kow, octanol–water
partition coefficient; MCI, molecular connectivity index; NA, not applicable; pKa, acid dissociation constant.
a
Values in parentheses represent the original ones as reported by the authors or as estimated by the models.
Values marked with an asterisk (*) are values selected for modelling purposes.
b
This experimental study was rejected because it was conducted at a concentration above the water solubility (see
details in Appendix A).
4. Sources and Uses
Etoposide is a semi-synthetic podophyllotoxin transformed in laboratory from the root of
the mayapple tree (Podophyllum peltatum) (Zounková 2010) and is not reported to occur
naturally in the environment.
Entry characterization consisted of searching for information on sources and releases of
the substance in relevant databases (Canada [1978]; HSDB 1983– ; Household
Products Database 1993–,LNHPD 2008, DPD 2010, EAFUS 2011, NHPID 2011). Based
on notifications submitted under the Cosmetic Regulations to Health Canada, etoposide
is not used in cosmetic products in Canada (2012 email from the Consumer Product
Safety Directorate, Health Canada, to the Existing Substance Risk Assessment Bureau,
Health Canada; unreferenced). Information available for this substance indicates that its
uses are limited to pharmaceuticals and positive controls in research. Literature
searches were conducted up to March 2013, and no information was found regarding
alternative uses or releases of this substance in Canada. To date, a survey pursuant to
section 71 of CEPA 1999 has not been issued for this substance. Data were available to
estimate that 22 kg and 23 kg of the substance were sold to hospitals and pharmacies
across Canada during the years 2011 and 2012, respectively (IMS 2013).
In Canada, etoposide is registered in Health Canada’s Drug Product Database as an
active ingredient in licensed pharmaceuticals (DPD 2010). This prescription drug is an
intravenous and oral chemotherapeutic agent used in the treatment of lung and
Screening Assessment - Etoposide
testicular cancer (Hospira Healthcare Corporation 2007; Bristol-Myers Squibb Company
2008).
Etoposide may also be used for additional off-label or veterinary uses that are not
considered in this assessment. The quantity of the substance being used for these
purposes is unknown.
5. Releases to the Environment
Pharmaceuticals can make their way into surface waters through release from
manufacturing or formulation sites and/or release of the unmetabolized substance in
feces or urine from consumers directly using these substances. For this assessment,
potential releases of etoposide from indirect sources (i.e., down-the-drain releases from
patients using the substance for cancer therapy) and direct sources (i.e., releases during
manufacture, formulation or packaging) were assessed. In both cases, releases are
expected to end up mainly in wastewater. No information was available regarding actual
releases of this substance from the manufacture or formulation of pharmaceuticals
containing it. Data were available to estimate the amount (23 kg) of the substance sold
to hospitals and pharmacies across Canada for the year 2012 (IMS 2013).
Anthropogenic releases to the environment depend upon various losses that occur
during the manufacture, industrial use, prescribed use and disposal of a substance. In
order to estimate potential releases to the environment occurring at different stages of
the life cycle of a substance, Environment Canada compiles information on the sectors
and product lines relevant to the substance. In addition to providing an overview of
stages where releases are possible, an effort is made to quantify the percent release
going to wastewater, land and air at different stages of the life cycle. 2 Relevant factors
are considered, uncertainties are recognized and assumptions may be made during
each stage, depending on information available.
The information is compiled to give an overview of the potential losses occurring at
different stages of the life cycle and the receiving media involved, as well as identifying
stages of the life cycle that are likely larger contributors to the overall environmental
concentration. Recycling activities and transfer to waste disposal sites (landfill,
2
The percent releases are presented as a range. Assumptions and input parameters used in making the release
estimates are based on information obtained from a variety of sources, including responses to regulatory surveys,
Statistics Canada, manufacturers’ websites and technical databases and documents. Of particular relevance are
emission factors, which are generally expressed as the fraction of a substance released to the environment,
particularly during its manufacture, processing and use associated with industrial processes. Sources of such
information include emission scenario documents, often developed under the auspices of the Organisation for
Economic Co-operation and Development (OECD), and default assumptions used by different international chemical
regulatory agencies. It is noted that the level of uncertainty in the mass of a substance and quantity released to the
environment generally increases towards the end of the life cycle.
Screening Assessment - Etoposide
incineration) are also considered. However, unless specific information on the rate of or
potential for release of the substance from landfills and incinerators is available,
releases to the environment from disposal are not quantitatively accounted for.
This information is used to further develop exposure characterization scenarios to
estimate resulting environmental concentrations. Presented in Table 5-1 is a summary
of the expected releases for etoposide over its life cycle.
Table 5-1: Summary of the estimated percent release to compartments resulting
from different life cycle stages for etoposidea.
Compartment of
Industrial use (%)
Prescribed use (%)
release
Wastewaterb
0.5
45–74
Metabolized
NA
15
Landc
0
0
Air
0
0
Abbreviation: NA, not applicable
a
Information from the following documents was used to estimate releases to the environment and the distribution
of the substance as summarized in this table: Hande 1998; Hospira Healthcare Corporation 2007; Bristol-Myers
Squibb Company 2008). Values presented for release to environmental media do not account for possible mitigation
measures that may be in place at some locations.
b
The loss to wastewater refers to raw wastewater prior to any treatment.
c
The loss to land does not include transfers subsequent to a substance’s use and service life (e.g., land
application of biosolids). These will be discussed in the “Ecological Exposure Assessment” section.
The above loss estimates indicate that etoposide has a potential for release to the
environment. Most etoposide is released to wastewater subsequently to the
administration of the drug, in feces and urine (i.e., little absorption or metabolism of the
drug).
In general, wastewater is a common point of entry of a substance into water through
wastewater system 3 effluent and a potential point of entry into soil through the
subsequent waste management of biosolids. When a substance is transferred to land
(i.e., the general public may discard un-used or expired pharmaceutical products
containing active medicinal ingredients in household garbage which will likely end up in
landfills), it may be washed into the sewer or surface water or transferred by wind or rain
to nearby soil. Finally, landfills have the potential to leach substances into groundwater
(potentially reaching surface water). In many landfill sites in Canada, leachate is
collected and treated either on-site or off-site prior to release to receiving water.
Unchanged etoposide has been found to be excreted in both urine and bile (Hospira
Healthcare Corporation 2007; Teva Parenteral Medicines 2007). The fraction of
3
In this assessment, the term wastewater system does not include sewer networks or collection systems.
Screening Assessment - Etoposide
etoposide released to the wastewater system varies according to the mode of
administration of the drug. When the drug was administered intravenously, the
proportion of unchanged etoposide recovered in urine represented 29% of the dose
(Allen and Creaven 1975). With this same mode of administration, it is estimated that an
additional 1.5–16% of the etoposide is recovered unchanged in feces (Hospira
Healthcare Corporation 2007; Teva Parenteral Medicines 2007). The maximum value of
16% is conservatively used for this assessment. Therefore, it is estimated that 45% of
the intravenous dose of etoposide will be released to the wastewater system from
prescribed use. This is the lower value in the range of releases to wastewater from
prescribed use.
The bioavailability of etoposide in the human body is reduced by half when the drug is
taken orally (Bristol-Myers Squibb Company 2008), due to the drug remaining in the
lumen. It is assumed that the total unabsorbed oral dose (52%) will be found unchanged
in feces (Bristol-Myers Squibb Company 2008). Up to 16% of the absorbed 48% may
return to the lumen to be excreted, for a total of 8% of the original dose. To the
unabsorbed fraction (52%) is therefore added the maximal amount of absorbed
etoposide returning to the lumen (8%), to reach a maximum of 60% of the oral dose
being excreted in feces.
Similarly, a total of 14% of the etoposide oral dose unchanged in urine is obtained by the
product of 29%, the fraction of etoposide intravenously administered found in urine
(Allen and Creaven 1975), and 48%, the fraction absorbed from an oral dose.
Therefore, 60% and 14% of the administered dose are expected to be found unchanged
in feces and urine, respectively, for a total maximum release of etoposide of 74% from
oral dosing. This accounts for the higher value in the range of releases to wastewater
from prescribed use.
A negligible amount of etoposide is estimated to be lost through waste disposal and
recycling. Etoposide phosphate administered intravenously and etoposide are expected
to have similar pharmacokinetics (Hande 1998) and therefore proportionate releases to
wastewater.
6. Measured Environmental Concentrations
In Canada, samples collected at six municipal wastewater treatment plants selected to
represent typical Canadian treatment systems and geographic variations were analyzed
for etoposide (Smyth and Teslic 2013). These data were collected through an existing
national wastewater monitoring program that was initiated under the Chemicals
Management Plan in 2008. The wastewater monitoring program for 2012–2013
incorporates a multi-media approach by including municipal landfill leachate that is
discharged into the wastewater treatment system, in order to better understand the
influence of leachate inputs to wastewater treatment plants and the impact, if any, on the
receiving water.
Screening Assessment - Etoposide
Etoposide was not detected in any of the influent or effluent samples or in any of the
biosolid samples, with detection limits for the samples ranging from 6.32 to 47.8 ng/L.
The results presented in Smyth and Teslic (2013) do not include winter sampling results,
which tend to show poorer removals of compounds. However, since etoposide was not
detected in the wastewater treatment plant influent in summer, seasonal variations are
expected to be negligible.
In other countries, data on concentrations of etoposide in municipal wastewater effluent,
hospital wastewater and receiving water bodies in other countries have been identified.
The concentrations of a few antineoplastic drugs, including etoposide, were measured in
the effluents of two hospitals in France (Catastini et al. 2008). One of the hospitals
specialized in the treatment of cancers. Samples were collected in quintuplicate at the
exit of the sewage pipe of both hospitals and in the municipal wastewater treatment
plant influent and effluent. Concentrations of etoposide in the hospital effluents were
between the detection limit (0.11 µg/L) and 5.0 µg/L. At the municipal wastewater
treatment plant, etoposide was not detected in the influent or effluent.
The effluents of 21 hospitals in China prior to wastewater treatment were analyzed for
nine cytostatic compounds, including etoposide (Yin et al. 2010). Sixty-five effluent
samples were analyzed for etoposide on different days. Etoposide was detected in 15 of
the 65 samples with concentrations up to 380 ng/L and a median concentration of 42
ng/L, but was under the detection limit of 5 ng/L in the remaining 50 samples. The
results varied significantly from day to day for the same hospital’s wastewater effluents,
which is likely due to the occurrence of a patient being treated in the hospital during a
designated sampling day.
In Spain, Martín et al. (2011) studied methods to improve the analytical detection
performance of various pharmaceutical compounds, including etoposide. Using highperformance liquid chromatography (HPLC) coupled with mass spectroscopy to analyze
etoposide concentrations, the authors reached a recovery efficiency ranging from 91%
to 105% in a hospital effluent, before and after the hospital’s wastewater system, and in
the receiving river. Mean etoposide concentrations (n = 3) were 15 ng/L in the
wastewater system influent and 3.4 ng/L in the wastewater system effluent; etoposide
was not detected in the river, at a detection limit of 2.2 ng/L.
Ferrando-Climent et al. (2013) similarly worked on the development of analytical
methods for cytostatic drugs in another region of Spain. A detection limit of 24 ng/L was
obtained by this group. To test the proposed method, wastewater samples were
collected at the effluent of four hospitals and at the influent of three municipal
wastewater treatment plants. Etoposide was below the detection limit in two of the
hospital effluents, while it reached concentrations of 98 ng/L and 406 ng/L in the other
two hospital effluents. Two of the three municipal wastewater treatment plant influents
showed no traces of etoposide, whereas the etoposide concentration was 83 ng/L in the
third influent.
Screening Assessment - Etoposide
7. Environmental Fate
7.1 Metabolites
A fraction of administered etoposide is excreted via urine conjugated to sulfate, or as a
glucuronide metabolite (Williams et al. 2002). Etoposide glucuronide, 6-[4-[5-[(2,8dihydroxy-7-methyl-4,4a,6,7,8,8a-hexahydropyrano[3,2-d][1,3]dioxin-6-yl)oxy]-8-oxo5a,6,8a,9-tetrahydro-5H-[2]benzofuro[5,6-f][1,3]benzodioxol-9-yl]-2,6dimethoxyphenoxy]-3,4,5-trihydroxyoxane-2-carboxylic acid, CAS RN 100007-55-4 is
the major metabolite found in human urine, at between 8% and 29% of the injected dose
(IARC 2000). Etoposide glucuronide is not listed on the Domestic Substances List
(DSL). In vitro, etoposide glucuronide was shown to be less cytotoxic than etoposide
(Schmidt and Monneret 2003). There are no indications that the addition of the glucose
ring on etoposide (forming etoposide glucoronide) could impact the toxicity of the
substance. Furthermore, etoposide glucuronide is expected to be less bioavailable than
etoposide, due to its larger diameter. Therefore, the metabolite is not evaluated
concurrently with etoposide in this screening assessment.
The hydroxy acid metabolite of etoposide is formed by opening of the lactone ring (the
D-ring). It has been detected in human urine at concentrations of 0.2–2.2% of the
administered dose (IARC 2000). The catechol metabolite of etoposide, 1,2-benzenediol,
has also been detected in urine, but in very small quantities (< 2% of the administered
dose) (Stremetzne et al. 1997). Catechol (CAS RN 120-80-9) has previously been found
to meet the paragraph 64(c) criterion under CEPA 1999 during the Challenge initiative,
for its use as a photographic developer (Environment Canada and Health Canada
2008). Its volume released as a metabolite of etoposide is very low compared with the
estimated releases from the use of catechol in photography. Due to the low percentages
of the administered dose of the drug being excreted in these forms, these metabolites
are not evaluated in this screening assessment.
7.2 Modelling Results
In the environment, CATALOGIC (2012) predicts that a degradation product, very similar
to etoposide, may be formed following biodegradation: 1-((7,8-dihydroxy-2methylhexahydropyrano[3,2-d][1,3]dioxin-6-yl)oxy)-6,7-dihydroxy-4-(3,4,5trihydroxyphenyl)-1,2,3,4-tetrahydronaphthalene-2-carboxylic acid. No information was
located for this substance. Due to its structural similarity to etoposide, QSAR model
predictions, predicting the fate in the environment and the effects, are very similar for
this metabolite and for etoposide.
Level III fugacity modelling (EQC 2003) simulates the distribution of a substance in a
hypothetical, evaluative environment known as the “unit world”. The EQC model
simulates the environmental distribution of a chemical at a regional scale (i.e., 100 000
km2) and outputs the fraction of the total mass in each compartment from an emission
into the unit world and the resulting concentration in each compartment. Environment
Canada uses only the mass fraction distribution results for general information on the
Screening Assessment - Etoposide
environmental fate of a substance and generally does not use the compartmental
concentration results for the predicted environmental concentration (PEC) in a
substance assessment. Some exceptions to this may occur, such as when a wide
dispersive release of a substance suggests that regional-scale concentrations are
appropriate for the PEC(s).
Etoposide is ionizable, with an acid dissociation constant (pKa) of 9.8. Under
environmentally relevant pH conditions (between pH 6 and pH 9), etoposide would
essentially be in its neutral form. Therefore, the EQC model can provide reliable
estimates. Model inputs to EQC (2003) are provided in Appendix B.
The mass fraction distribution of etoposide is given in Table 7-1 using individual steadystate emissions to air, water and soil. The level III EQC model assumes non-equilibrium
conditions between environmental compartments, but equilibrium within compartments.
The results in Table 7-1 represent the net effect of chemical partitioning, inter-media
transport and loss by both advection (out of the modelled region) and
degradation/transformation processes.
The results of Level III fugacity modelling (Table 7-1) suggest that etoposide is expected
to reside predominantly in water or soil, depending on the compartment of release.
Table 7-1: Summary of the Level III fugacity modelling (EQC 2003) indicating the
percentage of etoposide partitioning into each compartment
Percentage
Percentage
Percentage
Percentage
Substance
partitioning to partitioning to partitioning to
partitioning to
released to:
air
water
soil
sediment
Air (100%)
0.001
1.8
98.1
0.04
Water
0
97.8
0
2.2
(100%)
Soil (100%)
0
0.04
100
0.001
When released to water, etoposide is expected to remain in that medium. Volatilization
from water surfaces should not occur based on this compound’s estimated Henry’s Law
constant of 1.77 × 10–25 Pa·m3/mol. Nevertheless, if water is the receiving medium, a
small mass fraction of etoposide is expected to reside in sediment (Table 7-1).
If released to soil (e.g., biosolids application), etoposide is expected to adsorb slightly
onto solid particles based on its estimated organic carbon–water partition coefficient
(Koc) values of 1.9 to 199 (the maximum log Koc is estimated to be ~2.3), which indicates
that etoposide is expected to be fairly mobile in soil. Volatilization from moist soil
surfaces is not expected to occur based on its low Henry’s Law constant; therefore,
releases to soil result in most of the mass fraction remaining in soil or groundwater and
slow losses to reaction (degradation). However, releases to the soil compartment are
expected to be minimal (see Table 5-1 above). For example, little of the substance is
expected to associate with biosolids, given its low soil sorption coefficient.
Screening Assessment - Etoposide
A negligible amount of the substance is expected to reside in air (see Table 5-1 above).
Based on the low vapour pressure of 9.77 × 10–20 Pa and low Henry’s Law constant of
1.77 × 10−25 Pa·m3/mol, etoposide is not volatile. Therefore, if released solely to air, it
will deposit predominately onto soil (98.1%; Table 7-1).
Due to the very low proportion of etoposide expected to partition to air (Table 7-1) and
the short half-life of the substance in air (0.84 hour; see Table 7-2 below), it is
considered unlikely that etoposide would be transported through the atmosphere. Its
long-range atmospheric transport potential is considered negligible.
From its use as a prescription drug, etoposide is expected to be released to wastewater
from excretion and drug manufacture (Table 5-1). It is not expected to be retained in
large proportions in wastewater systems and would be found in surface water, where it
would remain in its neutral form, according to its physical and chemical properties.
Therefore, the fate and effects of etoposide in environmental media other than surface
water, such as soil and air, will not be assessed further, since exposure of non-aquatic
organisms is negligible.
7.3 Environmental Persistence
As presented in Table 5-1, no significant releases are expected in any media other than
wastewater. Once wastewater reaches the wastewater treatment system, only 1.51% of
the etoposide is expected to be retained in biosolids. However, 98.14% of the etoposide
would be found in the wastewater treatment system effluent, as modelled by the
wastewater treatment plant (WWTP) fugacity model (EQC 2003). When etoposide is
released to water, etoposide will reside predominately in surface water, with a negligible
proportion of the substance settling to sediment (Table 7-1).
In order to provide the best possible weight of evidence for the persistence of etoposide,
empirical and modelled data for the substance were considered.
7.3.1 Empirical data
Lu et al. (2000) reported that ultraviolet light (248 nm) ionized etoposide at room
temperature. The effects of other wavelengths were not evaluated by the authors. The
photolysis rate of etoposide exposed to a 248 nm sunbeam is dependent on the
substance’s concentration and has been reported to be 2.8 × 109 L/mol per second (Lu
et al. 2000). Photolysis may occur in water in the first ~30 cm below the surface.
Shah et al. (1989) prepared etoposide solutions of 100 mg/L in water buffered at various
pH values in amber-coloured bottles to avoid photolysis. Stability tests were conducted,
and the solutions were analyzed by HPLC until the remaining etoposide level was
negligible. The results were plotted versus time to determine half-lives. Only half-lives
from environmentally relevant pH values are shown in Table 5a. The degradation rates
were higher at higher pH.
Screening Assessment - Etoposide
No biodegradation studies were found for etoposide. The Millipore Material Safety Data
Sheet notes that etoposide failed the closed bottle test and Zahn-Wellens tests for ready
and inherent biodegradability (Millipore Corporation 2011). Details on the methodology
were not mentioned. Although the reliability could not be verified, the result of this
study—not readily biodegradable—is consistent with modelling results and structural
interpretation.
Table 7-2: Empirical data for degradation of etoposide
Medium
Fate
process
Degradation
value
Degradation
endpoint / units
Referen
ce
RSS
reliability
category
a
Water
Photolysis
2.8 × 109
(248 nm)
Water
Hydrolysis
63.00
Water
Hydrolysis
49.50
Water
Hydrolysis
27.72
Photolysis rate /
L·mol−1·s−1
Half-life (pH 5.00)
/ days
Half-life (pH 6.15)
/ days
Half-life (pH 7.30)
/ days
Lu et al.
2000
Shah et
al. 1989
Shah et
al. 1989
Shah et
al. 1989
NR
Low
Low
Low
Abbreviations: NR, not reviewed; RSS, robust study summaries
a
Robust study summaries were used to determine the quality of the studies and are available in Appendix A.
7.3.2 Modelling results
Since limited experimental data on the degradation of etoposide are available, a QSARbased weight of evidence approach (Environment Canada 2007) was applied using the
degradation models shown in Table 7-3. Given the ecological importance of the water
compartment, the fact that most of the available models apply to water and the fact that
etoposide is expected to be released to this compartment, biodegradation in water was
primarily examined.
Table 7-3 summarizes the results of available QSAR models for degradation in various
environmental media.
Table 7-3: Modeled data for degradation of etoposide
Fate process
Atmospheric
oxidation
Ozone reaction
Hydrolysis
Primary
biodegradation
(aerobic)
Model and model
basis
Model result and
prediction
Extrapolate
d half-life
(days)
AOPWIN 2008a
t½ = 0.035 day
<2
AOPWIN 2008a
HYDROWIN 2008a
BIOWIN 2008a
NAb
NA
3.72c
NA
NA
Sub-model 4: Expert
“biodegrades fast”
< 182
Screening Assessment - Etoposide
Fate process
Model and model
basis
Model result and
prediction
Extrapolate
d half-life
(days)
Survey
(qualitative results)
BIOWIN 2008a
Ultimate
biodegradation
(aerobic)
Sub-model 3: Expert
Survey
2.1c
≥ 182
“biodegrades slowly”
(qualitative results)
BIOWIN 2008a
Ultimate
biodegradation
(aerobic)
0.65d
Sub-model 5:
< 182
“biodegrades fast”
MITI linear probability
BIOWIN 2008a
Ultimate
biodegradation
(aerobic)
Ultimate
biodegradation
(aerobic)
0.02d
Sub-model 6:
MITI non-linear
probability
“biodegrades very
slowly”
≥ 182
% BOD = 13.9
CATALOGIC 2009
130
“biodegrades slowly”
Abbreviations: BOD, biological oxygen demand; MITI, Ministry of International Trade and Industry (Japan); NA, not
applicable; t½, half-life
a
EPI Suite (2008).
b
Model does not provide an estimate for this type of structure.
c
Output is a numerical score from 0 to 5.
d
Output is a probability score.
Etoposide’s biodegradation model predictions should be viewed with some caution.
Biodegradation processes involve biological activity that may be altered or improved by
pharmaceuticals. As etoposide’s mode of action decreases cell viability, it is possible
that the substance has antibiotic activity in the environment as well. Therefore,
biodegradation rates would be underestimated. Although cell viability is not an intrinsic
structural factor to estimate persistence, bacterial cell viability is directly proportional to
the biodegradation rates that influence the stability of the substance in the environment.
The estimates proposed by DS TOPKAT (©2005–2009) were not considered reliable to
describe etoposide’s biodegradation rate, as etoposide was considered outside of the
model domain for DS TOPKAT. It is believed that chemicals with comparable structures
are not contained in DS TOPKAT’s training set. Therefore, DS TOPKAT estimates are
not shown in Table 7-3.
Screening Assessment - Etoposide
The predictions for CATALOGIC (2009) were 46.7% in the structural domain and were
within the parameter domain for octanol–water partition coefficient (Kow). CATALOGIC
(2009) is able to predict metabolic pathways and transformation products from abiotic
reactions and microbial transformations. For etoposide, the model estimates that one
compound would be formed predominantly. The resulting structure is similar to
etoposide, but with the two five-carbon rings open at the oxygen location. Several
transformation steps are required to obtain this metabolite: ester hydrolysis, primary
hydroxyl group oxidation, aldehyde oxidation, decarboxylation and oxidative Odealkylation at three locations on the structure. Each reaction has an occurrence
probability of between 73% and 100% in the environment. Summing the uncertainties of
occurrence of every reaction, the probability of obtaining the metabolite is 47%
(CATALOGIC 2009).
The primary biodegradation model BIOWIN Sub-model 4 estimates that degradation of
etoposide has a primary half-life of < 182 days. The ultimate biodegradation models
suggest that biodegradation is slow and that the half-life in water would be ≥ 182 days,
whereas the result of the BIOWIN Sub-model 5 would suggest that the substance has a
half-life of < 182 days. The results from BIOWIN Sub-models 3 and 6 and the
CATALOGIC model suggest a slow to very slow rate of biodegradation. Some of
etoposide’s structural features may not be biodegradable, as the structure includes a
large number of rings and branches, whereas other of its structural features are easily
biodegradable, such as esters and benzene rings with various substitutions (easily
biodegradable for compounds with Kow < 2.18) and cyclic chemicals consisting only of C,
O, N and H. Therefore, considering all model results, empirical data and structural
features, there is more reliable evidence to suggest that the biodegradation half-life of
etoposide is ≥ 182 days in water.
In air, a predicted atmospheric oxidation half-life of 0.035 day (see Table 7-3)
demonstrates that this substance is likely to be rapidly oxidized. The substance is not
expected to react appreciably with other photo-oxidative species in the atmosphere,
such as ozone; however, etoposide is susceptible to direct photolysis in ultraviolet light
(Lu et al. 1999). Therefore, it is expected that reactions with hydroxyl radicals will be the
most important fate process in the atmosphere for etoposide. The substance is not
expected to be found in air, but could be degraded by sunlight in the first centimetres
below the surface of receiving water bodies.
Using an extrapolation ratio of 1:1:4 for water:soil:sediment biodegradation half-lives
(Boethling et al. 1995), the half-life in soil is also ≥ 182 days, and the half-life in
sediments is ≥ 365 days. This indicates that, overall, etoposide is expected to be
persistent in water, soil and sediment.
7.3.3 Conclusion on persistence
Photolysis and primary biodegradation half-lives of etoposide in water suggest that
etoposide is readily biodegradable. However, results of CATALOGIC (2009) and
BIOWIN (2008) Sub-models 3 and 6 indicate that ultimate biodegradation in the
Screening Assessment - Etoposide
environment is slow. CATALOGIC (2009) predicts a major metabolite resulting from
etoposide degradation that is very similar to etoposide, meaning that primary
biodegradation may be fast, but the skeleton of the parent structure could be minimally
transformed. Accordingly, etoposide is considered to be persistent in the environment.
7.4 Potential for Bioaccumulation
Experimental and modelled log Kow values of 0.04–1.0 for etoposide (value used for
modelling: 0.6) suggest that the substance has a low potential to bioaccumulate in biota
(see Table 3-1). In order to provide the best possible weight of evidence analysis of the
bioaccumulation potential of etoposide, modelled data, empirical pharmacokinetic
studies and other physiological parameters, such as metabolism and elimination, were
considered in order to arrive at an overall conclusion.
7.4.1 Metabolism and elimination
A pharmacokinetic study indicates that 34–66% of the administered dose is recovered in
human urine after 72 hours (Allen and Creaven 1975). In a similar analysis, Joel et al.
(1995) found that 44% of the dose was recovered in urine. This suggests that etoposide
is rapidly eliminated from humans and would not result in significant body burdens over
time. In the human body, a fraction of the administered etoposide is metabolized by
lactone hydrolysis to generate the hydroxy acid form of the substance; this metabolite
appears to be pharmacologically inactive (McEvoy 2004). The drug can also be
transformed by the action of the cytochrome enzyme CYP3A4 and by sulfate and
glucoronate conjugation (Williams et al. 2002). Generally, the metabolism of etoposide
in the human body follows two pathways: a phase I process that essentially involves
CYP3A4 to produce a hydroxy acid compound and a phase II pathway that would lead
to the excretion of glucuronide and sulfate metabolites. The biotransformation in hepatic
cells is a CYP3A4 (cytochrome P450–mediated demethylation) reaction (IARC 2000). A
homologue of this enzyme is present in mammals, fish and most other species, and it is
deemed that detoxification will occur in a similar fashion in most aquatic species.
The major metabolite found in human urine is the etoposide glucuronide (IARC 2000), at
8–29% of the administered dose. In patients with normal renal and hepatic efficiencies,
the elimination half-life of etoposide was estimated to be 5.6 ± 0.4 hours (D’Incaici et al.
1986). The low elimination half-life suggests that both etoposide and its metabolite will
be rapidly excreted.
For aquatic organisms, the metabolic competency of an organism can be related to body
weight and temperature. The lipid content of fish differs from the lipid content of humans,
and the temperature of Canadian waters is on average lower than normal room
temperature. Although phase I and II metabolic activity in fish may be significantly
reduced compared with human metabolic activity, it is likely that elimination processes in
humans are rapid enough to suggest that the bioaccumulation potential in aquatic
species would be low.
Screening Assessment - Etoposide
7.4.2 Estimating BCF and BAF
Given its use as an antineoplastic drug, etoposide is expected to show high metabolic
activity. Therefore, the modelling methods for estimating bioaccumulation based on
comparison of empirical bioaccumulation factors (BAFs) and bioconcentration factors
(BCFs) of similar molecules or fragments are not suitable for this substance. However, a
mass balance model such as the Arnot-Gobas model may provide reliable estimates
because it includes the metabolic rate in its calculations.
Since no experimental BAF or BCF data were available for etoposide, a predictive
approach was applied using available BAF and BCF models, as shown in Table 7-4.
An estimated BCF of 3 was reported for etoposide (Millipore Corporation 2011) using a
log Kow of 0.60 and a regression-derived equation. This BCF suggests that the potential
for bioconcentration in aquatic organisms is very low.
Measures of BAF are the preferred metric for assessing bioaccumulation potential of
substances. This is because BCF may not adequately account for the bioaccumulation
potential of substances via the diet, which predominates for substances with log Kow >
~4.0 (Arnot and Gobas 2003). Kinetic mass balance modelling is in principle considered
to provide the most reliable prediction method for determining the bioaccumulation
potential because it allows for metabolism correction as long as the log Kow of the
substance is within the log Kow domain of the model. For etoposide, BAF estimates are
deemed to be similar to BCF values because of the negligible dietary uptake for a
substance with a low Kow.
BCF and BAF estimates, corrected for potential biotransformation, were generated using
the BCFBAF (2008) model. Metabolic rate constants (kM) were derived using structure–
activity relationships, described further in Arnot et al. (2008a, b). The middle trophic level
fish was used to represent overall model output and is most representative of the fish
weight likely to be consumed by an avian or terrestrial piscivore. The metabolic rate
constant (kM) is < 125.0/day, depending on the fish weight. The results of the BCF
modelling are given in Table 7-4.
Table 7-4: Summary of modelled data for bioaccumulation of etoposide
kM
Test
Model and model
Value (L/kg
Endpoint
Reference
(/day) organism
basis
wet weight)
BCFBAF
BCFBAF
125a
Fish
BCF
0.97
2008
Sub-model 1 (linear
regression)
BCFBAF
BCFBAF
2008
BCFb
1.02
70.3
Fish
Sub-model 2 (mass
balance)
BCFc
11.95d
0.17
Fish
BCFmax without
CPOPs 2008
Screening Assessment - Etoposide
mitigating factorsc
BCFBAF
39.5
Fish
Sub-model 3
BAFb
1.03
BCFBAF
2008
(Gobas mass
balance)
Abbreviations: BAF, bioaccumulation factor; BCF, bioconcentration factor; kM, metabolic rate constant
a
Predicted value exceeds the theoretical whole-body maximum value, so the whole body maximum values are
provided and recommended by the model to replace the original model predictions.
b
Results generated using weight, lipid and temperature for a middle trophic level fish.
c
Possible mitigating factors include ionization, molecular size, metabolism and water solubility.
d
Number of “unknown fragments” is 57.14%, which is too high to be acceptable.
The BCFBAF (2008) model flagged that the predicted metabolic rate constant (i.e.,
100/day for a 10 g fish) exceeds the theoretical whole-body maximum value, suggesting
that etoposide may be readily metabolized in fish.
Based on three-dimensional analysis of conformers calculated using the BCFmax Model
with Mitigating Factors (CPOPs 2008), the maximum (Dmax) and effective (Deff)
diameters of etoposide range from 1.43 to 2.06 nm. This suggests that etoposide may
also experience restricted uptake from steric effects at the gill surface. Information
regarding molecular size and cross-sectional diameters is useful to consider and is
commonly used by international jurisdictions such as the European Union (ECHA 2008)
as weight of evidence for bioaccumulation potential. Recent investigations relating fish
BCF data to molecular size parameters (Dimitrov et al. 2002, 2005) suggest that the
probability of a molecule crossing cell membranes as a result of passive diffusion
declines significantly with increasing Dmax. The probability of passive diffusion decreases
appreciably when the Dmax is > ~1.5 nm and more so for molecules having a Dmax of
> 1.7 nm. Sakuratani et al. (2008) also investigated the effect of cross-sectional
diameter on passive diffusion in a BCF test set of about 1200 new and existing
chemicals. They observed that substances that do not have a very high bioconcentration
potential (BCF < 5000) often have a Dmax of > 2.0 nm and a Deff of > 1.1 nm. However,
as Arnot et al. (2010) noted, there are uncertainties associated with the thresholds
proposed by Dimitrov et al. (2002, 2005) and Sakuratani et al. (2008), since the BCF
studies used to derive them were not critically evaluated. Arnot et al. (2010) pointed out
that molecular size influences solubility and diffusivity in water and organic phases
(membranes), and larger molecules may have slower uptake rates. However, these
same kinetic constraints apply to diffusive routes of chemical elimination (i.e., slow in =
slow out). Thus, significant bioaccumulation potential may remain for substances that
are subject to slow absorption processes, if they are slowly biotransformed or slowly
eliminated by other processes. However, if the rate of gill uptake is sufficiently mitigated
by steric hindrance to the point where the rate of elimination exceeds uptake,
bioconcentration will be lowered.
The available evidence indicates that etoposide is expected to have low
bioaccumulation potential due to its physical and chemical properties (i.e., high
molecular weight, low log Kow), relatively large cross-sectional diameter, resulting in
Screening Assessment - Etoposide
restricted uptake from steric effects at the gill surface, and high metabolic activity in
many species, which can accelerate the excretion of etoposide from the cells.
Metabolism-corrected BCF and BAF values are also < 5000.
7.4.3 Conclusion on bioaccumulation potential
Because of its low log Kow, rapid total rate of elimination, rapid gill exchange and
increased metabolic activity, etoposide is not expected to bioaccumulate, bioconcentrate
or biomagnify in aquatic biota.
8. Potential to Cause Ecological Harm
8.1 Ecological Effects Characterization
In order to provide the best possible weight of evidence for assessing the ecological
effects of etoposide, empirical and modelled data were considered in the assessment.
The QSAR models are based on similarities with a large number of compounds, which
include a limited number of biologically active compounds such as drugs. Etoposide is
considered within the limits of domain applicability for most models, but the level of
variability between models is very high.
8.1.1 Mode of action
In mammals, etoposide is an inhibitor of topoisomerase II, an enzyme essential for
deoxyribonucleic acid (DNA) replication, transcription, recombination and chromosomal
segregation. Etoposide forms a ternary complex with DNA and the topoisomerase II
enzyme, preventing religation of the DNA strands. The biotransformation in hepatic cells
involves cytochrome P450–mediated demethylation (CYP3A4) (IARC 2000). A version
of this enzyme is present in most species, so it is suggested that detoxification will occur
using the same enzymatic system in aquatic species.
8.1.2 Empirical aquatic toxicity data
Empirical aquatic toxicity data for etoposide are presented in Table 8-1. Relatively few
data are available on gross or whole body level effects (e.g., abnormal development).
However, a number of biomarker test results are available and are presented in the next
subsections. Due to the potential impact of etoposide on endocrine function and
carcinogenicity, much of the research on etoposide has focused on these areas. They
are largely in vitro studies and therefore cannot be readily used for developing a
predicted no-effect concentration (PNEC) for risk characterization because of the
difficulty in extrapolating from adverse biochemical effects to the ecological population.
Table 8-1: Empirical aquatic toxicity data for etoposide
Test organism
Bacteria
Type of test
Acute (16 h)
Endpoint
NOEC
Value
(mg/L)
200
Reference
Zounková et al.
Screening Assessment - Etoposide
Test organism
Pseudomonas putida
Bacteria
Pseudomonas putida
Bacteria
Pseudomonas putida
Green alga
Pseudokirchneriella
subcapitata
Green alga
Pseudokirchneriella
subcapitata
Green alga
Pseudokirchneriella
subcapitata
Crustacean Daphnia
magna
Crustacean Daphnia
magna
Crustacean Daphnia
magna
Type of test
Endpoint
Value
(mg/L)
Reference
2007
Zounková et al.
2007
Zounková et al.
2007
Acute (16 h)
LOEC
250
Acute (16 h)
EC50
630
Acute (96 h)
NOEC
< 10
Zounková et al.
2007
Acute (96 h)
LOEC
10
Zounková et al.
2007
Acute (96 h)
EC50
250
Zounková et al.
2007
Acute (48 h)
NOEC
10
Acute (48 h)
LOEC
30a
Acute (48 h)
EC50
30a
Zounková et al.
2007
Zounková et al.
2007
Zounková et al.
2007
Abbreviations: EC50, the concentration of a substance that is estimated to cause some effect on 50% of the test
organisms; NOEC, the no-observed-effect concentration, the highest concentration in a toxicity test not causing a
statistically significant effect in comparison with the controls; LOEC, the lowest-observed-effect concentration, the
lowest concentration in a toxicity test that caused a statistically significant effect in comparison with the controls;
a
Critical value for inherent toxicity to non-human organisms.
The effects of etoposide on species from three major trophic levels of the aquatic
compartment were tested: producers, consumers and decomposers (Zounková et al.
2007). The growth inhibition of the unicellular green alga Pseudokirchneriella
subcapitata, a producer, in cell cultures was measured over 96 hours for the amount of
chlorophyll using the response to green light absorbance (680 nm) at five etoposide
concentrations. The assay was repeated in three or four replicates used to generate
dose–response curves. Statistical tests were used to determinate no-observed-effect
concentration (NOEC), lowest-observed-effect concentration (LOEC) and median
effective concentration (EC50), presented in Table 8-1. The effects of etoposide on newly
hatched daphnid, Daphnia magna, a consumer, were assessed at six concentrations.
After 48 hours of exposure, the immobilized organisms were counted, and the results
were expressed as the percentage of control. Statistical tests were performed to
calculate NOEC, LOEC and EC50, shown in Table 8-1. The growth inhibition of cell
cultures of the bacteria Pseudomonas putida, a decomposer, was measured from the
absorption at 590 nm. The test was performed at six etoposide concentrations to
generate dose–response curves. The article met quality standards, and a robust study
summary was used to determine the quality of the studies and is appended in Appendix
A. Standardized statistical toxicity test results are presented in Table 8-1.
Screening Assessment - Etoposide
8.1.3 Mechanisms of toxicity
Four-week studies of toxicity were conducted in monkeys treated intravenously at 0.4–
3.6 mg/kg body weight (bw) per day. The main effects observed were myelosuppression
with anemia, leucopenia, thrombocytopenia and some hepatotoxicity (IARC 2000).
The induction of p53 protein and apoptosis rate were investigated in fish desert
topminnow (Poeciliopsis lucida) hepatocytes (Rau Embry et al. 2006). In mammals, the
p53 protein protects normal cells from aberrant growth by its ability to modulate the
genes involved in cell growth, notably caspase-3. In desert topminnow, p53 protein level
was not affected by etoposide, but a significantly higher level of apoptosis, as shown by
dose-dependent induction of caspase-3, was observed at concentrations of 5.9 and 14.7
mg/L. This suggests that the p53 protein was activated by an alternative mechanism in
fish, compared with mammals. Therefore, at the cellular level, the mechanism of toxicity
of etoposide may not be comparable in fish and mammals.
In order to validate the activity of endosulfan in reducing the apoptosis rate in spleen
cells from Nile tilapia (Oreochromis niloticus), Tellez-Bañuelos et al. (2011) used
etoposide for the positive control. Using flow cytometry, the authors counted apoptotic
cells in a culture exposed to endosulfan alone, to etoposide alone or to both substances
and in a control culture not exposed to xenobiotics. The cell density of splenocytes
exposed to etoposide and subject to early apoptosis decreased by 22%, 14% and 13%
relative to control cells after 24, 48 and 72 hours, respectively.
8.1.4 Potential for genotoxicity
The genotoxicity potential of etoposide was assessed using a pair-wise matching
technique by Jackson et al. (1996) to generate a genetic activity profile. While the data
clearly show a potential for genotoxicity at low doses of 0.01–50 mg/kg bw in humans
and other mammals, this effect is not observed in most prokaryotes or in lower
eukaryotes, for which almost no effects are observed following exposure to etoposide
concentrations between 74 and 740 mg/L.
DNA degradation in mussel hematocytes and gills resulting from exposure to etoposide
was assessed by Mičić et al. (2002). The separation of DNA strands in mussels
following exposure to etoposide was examined. As expected, DNA strands were broken
by the action of etoposide, but response to the substance resulted from non-random
separation of DNA fragments. The results were not provided, but the authors suggested
that etoposide’s mechanism of genotoxicity in mussels is due to its action on specific
DNA sequence targets in hematocytes and gills.
Screening Assessment - Etoposide
In order to examine the genotoxicity potential of etoposide, growing cultures of
Escherichia coli and Salmonella choleraesius subsp. choleraesius were exposed to
various concentrations of etoposide by Zounková et al. (2007). In E. coli, the induction of
SOS-chromotest 4 response resulting from an alteration of the genetic information was
measured indirectly using the ratio of β-galactosidase and alkaline phosphatase
relatively to the negative control. To simulate the influence of metabolic activity, the
experiment was repeated with the addition of rat liver homogenate. This addition
inhibited etoposide’s minimum genotoxic concentration by ~3 times after 2 hours (Table
8-2), indicating that metabolism may be rapid. In Salmonella choleraesius subsp.
choleraesius, the effects of etoposide were measured by the strain’s growth inhibition,
rather than its metabolic activity. The Salmonella strain is less sensitive than E. coli to
etoposide, as shown by its higher minimum genotoxic concentration.
Table 8-2: Empirical genotoxicity data for etoposide
Test organism
Type of test Endpoint
Value (mg/L)
2.4 (without
Bacterium
metabolic activation),
Genotoxicity
MGC
6.4 (with metabolic
– 2 hours
Escherichia coli
activation)
Yeast
Genotoxicity
MGC
150 (140–168)
Saccharomyces
– 16 hours
cerevisiae
Reference
Zounková et al.
2007
Zounková et al.
2007
Abbreviations: MGC, minimum genotoxic concentration; RSS, robust study summary
Some evidence of the genotoxicity potential of etoposide in mice, rats and humans is
presented in IARC (2012), which concludes that etoposide is carcinogenic to humans
(Group 1). Although it is known that etoposide has genotoxic activity in mussels and
prokaryotes, it is not possible to conclude with certainty that genotoxicity would be
observed in other aquatic organisms.
8.1.5 Other ecological effects
Milan et al. (2003) assessed life-threatening arrhythmia resulting from exposure of
zebrafish larvae to etoposide. The two arrhythmia symptoms that indicate heart rate
disorder are QT interval prolongation on the electrocardiogram and torsades de pointes.
4
SOS-chromotest: a bacterial genotoxicity test with the genetically modified bacterial tester strain Escherichia coli
PQ 37. β-Galactosidase activity was measured (reporter enzyme for genotoxicity induced along with DNA repair
system) using a chromogenic substrate ortho-nitrophenyl-β-D-galactopyranoside. At the same time, activity of alkaline
phosphatase (marker of viability/cytotoxicity) was assessed using p-nitrophenyl phosphate chromogenic substrate.
The concentrations causing more than 50% inhibition were excluded from genotoxicity evaluations. The SOS
induction factor was then calculated for each tested concentration, and the minimum genotoxic concentration at which
the induction factor, 1.5, was determined. Values > 1.5 indicate significant genotoxicity.
Screening Assessment - Etoposide
These symptoms were monitored using a camera directed towards the fish heart and
analyzed using software measuring pixel density, plotted against time. After 24 hours of
exposure to etoposide at 1, 10 or 100 mg/L, no significant effect on heart rate or
arrhythmia was observed.
The multi-xenobiotic resistance of sea urchin embryos to etoposide alone or mixed with
known resistance inhibitors was assessed by Smital et al. (2004). Embryos tested with
only etoposide at 2.94 mg/L did not show any significant increase in cell death.
However, when the drugs verapamil and reversin 205 were added to the mixture at low
concentrations, the ratio of apoptotic cells to normal cells was up to 10-fold higher than it
was following exposure to etoposide alone. The authors proposed that cell death is
generated in embryos by high alterations of the genetic material. These co-exposure
experiments indicate that the apoptotic resistance system of sea urchin embryos is
affected by drug mixtures that could be present in effluents from large drug point
sources, such as hospitals.
Etoposide has been shown to be teratogenic and embryocidal in mice and rats at doses
of 1–3% of the recommended human dose based on body surface area (McEvoy 2004).
Etoposide induced thymic atrophy in gestating female rats at 10 mg/kg bw. As the
thymus is a gland of the endocrine and immune system, etoposide is suspected of
affecting endocrine function. However, there is not enough information to conclude this
with high certainty.
8.1.6 Modelled aquatic toxicity results
As the empirical data are limited, QSAR models were used to read across similar
structures in order to verify the consistency between this approach and the experimental
studies presented in Tables 8-1 and 8-2. Confidence in modelled results is low because
of the lack of complete structural coverage for etoposide for most of the models tested
(e.g., OASIS, ECOSAR, DS TOPKAT, CPOPs). Consequently, only the AIEPS (©2010–
2012) model was selected. In addition, only the effect values of the top 10 structures
that had over 60% similarity with etoposide were averaged and are presented in Table
8-3. For the green alga Pseudokirchneriella subcapitata, only the values from the top
five most similar structures were averaged, as only these had over 60% similarity with
etoposide (Table 8-3). The results achieved by this read-across approach are consistent
with the empirical results of Tables 8-1 and 8-2.
Table 8-3: Modelled acute aquatic toxicity data for etoposide
Type of
Value
Endpoint
Test organism
test
(mg/L)
Fish (fathead minnow
Acute (96
LC50
47.6
Pimephales promelas)
h)
Acute (48
Crustacean (Daphnia magna)
LC50
74.9
h)
Alga (Pseudokirchneriella
Acute (72
EC50
10.2
subcapitata)
h)
Reference
AIEPS ©2010–
2012
AIEPS ©2010–
2012
AIEPS ©2010–
2012
Screening Assessment - Etoposide
Abbreviations: EC50, the concentration of a substance that is estimated to cause some effect on 50% of the test
organisms; LC50, the concentration of a substance that is estimated to be lethal to 50% of the test organisms
The predicted critical effect concentration of etoposide in fish was calculated by Fick et
al. (2010), using the fish plasma model proposed by Huggett et al. (2003). This model
generates a concentration ratio based on the compound’s Kow between human
therapeutic plasma concentration and the fish steady-state plasma concentration. Based
on this, the model predicts the concentration of concern in fish from the pharmaceutical
response in humans. The theoretical plasma bioconcentration ratio was estimated to be
low, and the critical effect concentration of etoposide in fish was 7.1 mg/L.
8.1.7 Derivation of the PNEC
The acute toxicity tests for etoposide with algae, crustaceans and bacteria indicate a
potential for effects on a variety of aquatic organisms. Green algae are the most
sensitive class of aquatic organisms tested at low concentration, with low acute effect
concentrations of 10 mg/L. However, an effect level for microscopic algae may be overly
conservative for other aquatic organisms. At higher concentrations, a larger proportion
of the population of D. magna is affected by etoposide. The EC50 of D. magna exposed
to etoposide is as low as its LOEC; the lowest concentration having significantly different
effect value from control is identified as the EC50. This is likely owing to large variability
between replicates or poor design of the range-finding study to determine exposure
concentrations, raising the uncertainty for all tested concentrations. The critical toxicity
value (CTV) was selected to be 30 mg/L, the LOEC and EC50 for D. magna.
A conservative PNEC was derived by dividing the CTV identified (30 mg/L) by an
uncertainty factor of 500 to account for uncertainties and possible long-term subchronic
effects resulting from exposure to etoposide, as follows: a factor of 100 was applied to
account for uncertainty related to interspecies and intraspecies variability in sensitivity,
extrapolation from acute to chronic effects and extrapolation from laboratory conditions
to the field. A supplementary factor of 5 was applied to account for the possible effects
related to genotoxicity and endocrine function. These subchronic effects would not be
seen in standard short-term laboratory tests because they are not designed to observe
cellular or gene-level interactions. Possible carcinogenic, mutagenic or hormonal effects
from reactive substances may not be observed over the lifetime of the organism, but
“molecular initiating events” may commence quite rapidly upon permeation of the cell by
a reactive compound (in this case a cancer treatment drug), disrupting cellular
processes. Therefore, additional precaution is warranted to account for this nonquantifiable source of uncertainty, which could result in non-predictable excess toxicity
in a species. It has been demonstrated that etoposide has synergistic effects with other
drugs likely to be released from the same source (Smital et al. 2004).
This calculation results in a PNEC of 0.06 mg/L.
Screening Assessment - Etoposide
8.2 Ecological Exposure Assessment
No data concerning the concentrations of etoposide in any media in Canada have been
identified. PECs have been estimated from available information, including estimated
substance quantities, estimated release rates and characteristics of the receiving
aquatic environment. PECs have been estimated for an industrial release scenario and
a down-the-drain release scenario, as described in the following subsections. Since the
biological activity of etoposide metabolites and their contributions to toxicity are deemed
less than those of the parent compound, they are not assessed in this screening
assessment.
8.2.1 Industrial release
An aquatic exposure to etoposide is expected if the industrial substance is released
during its manufacture and processing to a wastewater system that discharges its
effluent to a receiving surface water body. The concentration of the substance in the
receiving water near the discharge point of the wastewater system is used as the PEC in
evaluating the aquatic risk of the substance. It is calculated using the following equation:
PECaq = (1000 × Q × L) × (1 − R) / (N × F × D)
where:
PECaq:
Aquatic concentration resulting from industrial releases (mg/L)
1000: Conversion factor (g/kg)
Q: Total substance quantity produced annually at an industrial site (kg/year)
L: Loss to wastewater (fraction)
R: Wastewater treatment plant removal rate (fraction)
N: Number of annual release days (days/year)
F: Wastewater treatment plant effluent flow (m3/day)
D: Receiving water dilution factor (dimensionless)
Table 8-4 presents the inputs used to estimate aquatic concentrations close to the
industrial point of discharge. Three companies were identified as having industrial
activities related to etoposide, but the proportion of the drug manufactured or imported
by each of the individual facilities is unknown. Therefore, it was conservatively assumed
that all the etoposide mass on the Canadian market is manufactured by one facility.
Based on these assumptions, this scenario yields a PEC of 1.61 × 10−6 mg/L
(Environment Canada 2013a). This PEC value represents the level of exposure in the
receiving water away from the point of discharge from the wastewater system at the site.
Screening Assessment - Etoposide
Table 8-4: Summary of input values used for estimating aquatic concentrations
resulting from industrial releases of etoposide from the pharmaceutical industry
Input
Value
Justification and reference
Estimated quantity as prescribed at hospitals and
Q: Quantity (kg/year)
23
pharmacies across Canada for the year 2012 (IMS
2013)
Personal communication, Technical Support
Document for Pharmaceutical Spreadsheets, from
L: Loss to wastewater
Environmental Assessment Unit, New Substances
0.5
(%)
[Health Canada], to Exposure Unit, Existing
Substances [Environment Canada], dated 2007;
unreferenced
R: Wastewater system
WWTP fugacity model from EPI Suite (2008): total
2
removal efficiency (%)
removal from a wastewater system
Assumed to be manufactured or processed in small
Number of annual
batches over 1 month, due to the assumption of the
release days
21
low substance quantity manufactured or processed
(days/year)
per industrial site
Effluent flow of a large wastewater treatment plant
Wastewater system
located in Mississauga (a typical Canadian
332 624
effluent flow (m3/day)
pharmaceutical manufacturing site, assumed to be
located in Mississauga)
Receiving water
Environment Canada default assumption for large
dilution factor
10
lakes, the WWTP in the scenario discharges to Lake
(dimensionless)
Ontario
Abbreviation: WWTP, wastewater treatment plant
8.2.2 Down-the-Drain Releases from Pharmaceutical Use
As etoposide is used in pharmaceutical products and can be released to water, an
aquatic exposure scenario resulting from down-the-drain releases from pharmaceutical
use was developed. The scenario estimates the concentration of etoposide in multiple
water bodies receiving wastewater treatment system effluents where pharmaceutical
products that contain etoposide may have been released (Environment Canada 2009).
This scenario provides estimates for approximately 1000 release sites across Canada
(Environment Canada 2013b).
The total mass of etoposide used in Canada was assumed to be evenly distributed
within the country. The releases are from the unabsorbed and unchanged fraction of the
drug excreted by patients in feces and urine. The number of annual release days was
estimated to be 365, based on use of the drug across patients. Some variability between
sites is expected because of the location of hospitals where the drug is administered.
Table 8-5 presents a summary of the inputs used to estimate aquatic concentrations
resulting from the use of etoposide. The approach and equations used to calculate the
PECs are described in Environment Canada (2009).
Screening Assessment - Etoposide
Table 8-5: Summary of the input values used for estimating aquatic
concentrations resulting from use of pharmaceuticals containing etoposide
Input
Value(s)
Justification and reference
Estimated quantity as sold to hospitals and
Quantity (kg/year)
23
pharmacies across Canada for the year 2012
(IMS 2013)
Assumes some uptake or metabolism of the
substance within human body (Hande 1998;
Hospira HealthCare Corporation 2007;
Bristol-Myers Squibb Company 2008); 74%
is the higher value in the range of the
calculated fraction released to water (see
Loss to
99
Table 5-1)
wastewater (%)
Variability factora
Wastewater
system removal
efficiency (%)
Number of annual
release days
(days/year)
Receiving water
dilution factor
(dimensionless)
2
Assumes no metabolism in light of the
uncertainty relating to the environmental
stability of the metabolites of etoposide, the
etoposide glucuronide
Default realistic worst-case value
2
WWTP fugacity model from EPI Suite (2008):
total removal from a wastewater system
365
This product is expected to be administered
year-long
Maximum 10
Environment Canada Existing Substances
default assumption
Abbreviation: WWTP, wastewater treatment plant
a
The variability factor is used to define the level of variability of the use of a product in the country. When multiple
products are on the same market, one may be used at a different average rate by inhabitants in one region compared
with those in another region. By default, a value of 2 is used as a realistic worst-case scenario applied to all sites.
The PECs of etoposide in the receiving water bodies were estimated to be in the range
of 3.8×10−8 to 1.6×10−5 mg/L.
8.3 Characterization of Ecological Risk
The approach taken in this ecological screening assessment was to examine various
supporting information and develop conclusions based on a weight of evidence
approach and using precaution, as required under CEPA 1999. Lines of evidence
considered include results from a conservative risk quotient calculation as well as
information on persistence, bioaccumulation, inherent or ecological toxicity, sources and
fate of the substance, and presence and distribution in the environment.
Quantities of etoposide sold in Canada are low, primarily for use as a pharmaceutical
product in medical oncology. As etoposide is released to wastewater from both industrial
Screening Assessment - Etoposide
and prescribed use, it will be treated by the wastewater treatment system. It is not
expected to sorb significantly to sludge or to be removed efficiently from the wastewater
system. Therefore, once released into the environment, it will be found mainly in water.
Etoposide is expected to be persistent in water, soil and sediment, but it is not expected
to be found significantly in media other than water. Based on its low Kow, its high
molecular weight and its high metabolic activity, etoposide is expected to be minimally
absorbed by gills and easily excreted. Therefore, etoposide is expected to have a low
bioaccumulation potential.
Etoposide has also been demonstrated to have moderate potential for toxicity to aquatic
organisms. Some of the evidence of harm for etoposide relates to endpoints such as
developmental and reproductive toxicity, genotoxicity and endocrine function. These
effects are part of the weight of evidence indicating that etoposide has the potential to
be hazardous to organisms. It is acknowledged that cancer generally occurs infrequently
in wild animals and that it is difficult to assess the potential for the manifestation of
cancer endpoints in individual organisms and to estimate the overall impact on
individuals or local populations of organisms. When there is evidence, as in the case for
etoposide, that a substance causes cancer in laboratory animals (particularly through a
genotoxic mechanism), such information could be considered to contribute to the weight
of evidence suggesting potential to cause ecological harm under CEPA 1999. However,
this would not necessarily be sufficient as a sole or primary basis for concluding that a
substance meets the criteria under paragraph 64(a) of CEPA 1999.
A risk quotient analysis, integrating realistic worst-case estimates of exposure with
toxicity information, was performed for the aquatic medium to determine whether there is
potential for ecological harm in Canada. The site-specific industrial scenario
(considering the actual receiving water body) presented above yielded a PEC of 1.61 ×
10−6 mg/L (Environment Canada 2013a).
This PEC value is then used to calculate a risk quotient, as shown in the following
equation:
RQ = PEC/PNEC
where:
RQ: Risk quotient (dimensionless)
PEC: Predicted environmental concentration in receiving water (mg/L)
PNEC:
Predicted no-effect concentration (mg/L)
Screening Assessment - Etoposide
The PNEC for aquatic organisms was evaluated to be of 0.06 mg/L. An assessment
factor of 500, which may be considered excessive to protect the environment, is deemed
to be conservative enough to account for subtle long-term effects such as genotoxicity
and endocrine disrupting effects. The current scientific knowledge on the potential
disruption of the ecosystem from these long-term effects is low, and precaution is
needed. The resulting risk quotient (PEC/PNEC) is 2.68 × 10−5. Therefore, harm to
aquatic organisms is unlikely at this site.
The risk quotients are less than one for all sites across Canada for exposures resulting
from down-the-drain releases through the consumption of pharmaceutical products that
contain etoposide. The maximum risk quotient at one location is 0.0003. Based on the
estimated number of receiving water bodies that will not be negatively affected by the
use of the substance, coupled with the magnitude of the risk quotient and the realism of
the scenario run, etoposide is not expected to cause harm to aquatic organisms from
down-the-drain releases.
Together, the information available suggests that there is low risk of harm to organisms
or the broader integrity of the environment from this substance. It is therefore concluded
that etoposide does not meet the criteria under paragraph 64(a) or 64(b) of CEPA 1999,
as it is not entering the environment in a quantity or concentration or under conditions
that have or may have an immediate or long-term harmful effect on the environment or
its biological diversity or that constitute or may constitute a danger to the environment on
which life depends.
8.4 Uncertainties in Evaluation of Ecological Risk
There are uncertainties due to the lack of information on environmental concentrations
in Canada, the lack of information on manufacturing and the quantity of etoposide
imported into Canada. Although no information was requested from industry, data were
available to estimate the amount of the substance prescribed at hospitals and
pharmacies across Canada for the years 2011 and 2012 (IMS 2013).
The proportion of etoposide manufactured and released from each individual industrial
facility is unknown. Therefore, it was conservatively assumed that all etoposide used in
Canada was manufactured at a single location. Similarly, as the distribution of the use
across Canada is unknown, a variability factor of 2 was applied to every location in
Mega Flush to account for uneven distribution.
The confidence in modelled results for a biologically active substance like etoposide is
low. The model estimates often considered only fragments of etoposide to compare with
other substances, and a large fraction was out of the domain of applicability. The models
to estimate effects cannot address specific modes of action, such as DNA binding, that
are characteristic of a drug like etoposide, nor could models estimate correctly
genotoxicity or endocrine function effects. Therefore, empirical data and other lines of
evidence contributed to the weight of evidence.
Screening Assessment - Etoposide
The bioaccumulation assessment is limited by the absence of empirical bioaccumulation
data and the difficulties in relying on bioaccumulation models. Therefore, a qualitative
assessment based on Kow, metabolic activity and a mass balance model was used to
predict the bioaccumulation potential of etoposide. The mass balance model cannot
address non-passive diffusion routes of uptake and partitioning of the substance to nonlipid phases in the organisms. There is, however, a low potential that model results
would be interpreted as false negative, given the substance’s low Kow.
Regarding ecotoxicity, based on the predicted partitioning behaviour of this substance,
the significance of soil and sediment as important media of exposure is not well
addressed by the effects data available. Indeed, the only effects data identified apply
primarily to pelagic aquatic exposures, although the water column may not be the
medium of primary concern, based on partitioning estimates.
9. Potential to Cause Harm to Human Health
Etoposide, by itself and in combination with cisplatin and bleomycin, has been classified
as carcinogenic to humans (Group 1) by the International Agency for Research on
Cancer (IARC 2012).
Drugs containing etoposide as an ingredient are assessed under the F&DA with respect
to their safety, effectiveness and quality. This assessment focused on uses and
exposures that were not covered as part of the F&DA assessment, specifically the risks
posed by the residues resulting from manufacture, formulation and disposal after use.
Releases of etoposide could occur during its manufacture from a pharmaceutical
production facility to a wastewater treatment plant and the subsequent discharge of
effluent from the treatment plant to a receiving water body. A conservative industrial
release scenario is used to estimate the aquatic concentration of the substance and
yields a concentration of 1.61×10−6 mg/L (1.6 ng/L) in the receiving water near the
discharge point of the wastewater treatment plant (see section 8.2.1).
When patients use pharmaceuticals, some of the drugs may not be absorbed or
metabolized, and even drugs that are metabolized may have active metabolites or may
revert to the parent form in environmental media. This may lead to excretion of active
drug residues into the wastewater system and release of the wastewater effluent
containing these residues into surface water (i.e., lakes, rivers), and this surface water
has the potential to be used as drinking water. Additionally, the drug may be released to
wastewater during the manufacturing process or via incorrect disposal of the excess
pharmaceutical. Therefore, a focus of this assessment is on the potential for indirect
exposure of humans to etoposide through drinking water.
Only a portion of the pharmaceutical used in Canada would be released into the
wastewater system. The metabolism of the substance results in a smaller portion of the
pharmaceutical being excreted by the patient in the urine and/or feces. This amount can
be further reduced as a result of wastewater treatment, environmental biodegradation
Screening Assessment - Etoposide
and/or drinking water treatment prior to consumption. The concentration in the water
source is also significantly reduced via dilution as the waste is released into waterways.
For this assessment, conservative assumptions were used when estimating the potential
indirect exposure of the general population to etoposide. Releases to surface water
were modelled using the down-the-drain releases from pharmaceutical use scenario, as
described above. For the purposes of modelling, it was assumed that 74% of the
pharmaceutical that was prescribed was excreted and released into wastewater. It was
also assumed that only 2% of etoposide was removed during wastewater treatment.
This scenario estimates concentrations in approximately 1000 waterways across
Canada. The highest values estimated by this scenario are typically in small waterways
with low dilution capacity, which are unlikely to be sources of drinking water. As a result,
this scenario would be expected to highly overestimate actual concentrations in drinking
water. The maximum PEC estimated was 1.21 × 10−. mg/L (12.1 ng/L).
Limited measured concentration data for etoposide were identified. The concentrations
measured in hospital effluent were not deemed relevant for this assessment, given the
various reductions in concentration that can occur between the release of effluent from
the hospital and consumption by humans. Smyth and Teslic (2013) attempted to
measure etoposide in wastewater from six wastewater treatment plants in Canada.
Etoposide was not detected in the influent or effluent, with detection limits ranging from
6.32 to 47.8 ng/L. As this substance was not detected even at the lowest detection limit,
this value (6.32 ng/L) is considered to be a conservative proxy to actual concentrations.
It is recognized that this concentration would not be expected to be found in drinking
water, as it would be further reduced via dilution after the effluent was released to
surface water and possibly reduced during the drinking water treatment process prior to
consumption. However, this value can be used as a conservative estimate of exposure
of Canadians.
The estimated intakes of etoposide by humans can be represented by formula-fed
infants 0–6 months of age, which is estimated to be the most highly exposed age class,
on a body weight basis, of those examined. The equation for deriving the estimated
intake is given below:
Intake = (PEC × IR) / bw
where:
Intake: Estimated intake of the substance from drinking water (mg/kg bw per day)
PEC: Predicted environmental concentration in receiving water from modelled or
measured data (mg/L)
IR: Ingestion rate of drinking water for formula-fed infants: 0.8 L/day (Health Canada
1998)
Screening Assessment - Etoposide
bw:
Default body weight for infants 0–6 months of age: 7.5 kg (Health Canada
1998)
The maximum estimated intake for etoposide, based on the detection limit of 6.32 ng/L
in wastewater treatment plant effluent in Canada in which etoposide was not detected, is
0.674 ng/kg bw per day. Based on the consumer release scenario’s modelled
concentration of 12.1 ng/L, the estimated intake would be 1.3 ng/kg bw per day.
Given the low levels of estimated exposure, the potential risk of indirect exposure to
etoposide is expected to be low. This determination is further supported by
consideration of two additional lines of evidence for evaluation of potential harm to
human health.
A comparison was made between the estimated intake value for etoposide and the
threshold of toxicological concern (TTC) value of 2.5 ng/kg bw per day originally
proposed by Kroes et al. (2004). The estimated intake is below the TTC. The TTC
provides a reference point against which the range of estimated intakes can be
compared. TTC values, which are derived using probabilistic approaches, establish
generic human exposure threshold values below which it is expected that the probability
of adverse effects is low. A TTC value of 0.15 µg/day (equivalent to 2.5 ng/kg bw per
day) has been established for potentially carcinogenic substances with structural alerts
for genotoxicity. Additional higher TTC values have been established for substances not
containing similar structural alerts by examining available toxicity data for large groups
of substances and are indicative of a very low probability of risk to human health (Munro
et al. 1996a, b; Kroes et al. 2004; EFSA 2012; Dewhurst and Renwick 2013).
A second comparison was also made to evaluate potential risk. The lowest therapeutic
dose (LTD) for etoposide was identified, and a margin of exposure (MOE) was
calculated to determine the ratio between the upper-bounding estimate of intake by the
general population and the dose that would be expected to produce a pharmacological
effect. This approach is consistent with methodology described elsewhere (Webb et al.
2003; Schwab et al. 2005; Watts et al. 2007; Bull et al. 2011; WHO 2011). The LTD is
the lowest concentration that evokes a desired therapeutic effect among target
populations and is equivalent to the lowest dose prescribed or recommended, taking into
account the number of doses per day (WHO 2011). These values are derived from an
assessment of the balance between safety and efficacy.
The products currently registered for use in Canada can be administered intravenously
or orally (DPD 2010); however, as the exposure route for the general population is
through oral ingestion of drinking water, an oral dose is the most relevant for
characterizing the potential risks. Dosage information for the oral form indicates a
recommended dose of 100–200 mg/m2 per day (Bristol-Myers Squibb Company 2008).
Using an adult body weight of 70.9 kg (Health Canada 1998) and a body surface area of
1.82 m2 for an adult (Health Canada 1995), the LTD of 100 mg/m2 is equivalent to a
dose of 2.6 mg/kg bw per day.
Screening Assessment - Etoposide
Conservative MOEs were derived using the equation below:
MOE = LTD/Intake
where:
MOE: Margin of exposure (dimensionless)
LTD: Lowest therapeutic dose (mg/kg bw per day)
Intake: Maximum estimated intake for drinking water derived from modelled or
measured concentrations (mg/kg bw per day)
Using the intake based on the detection limit of samples of wastewater influent and
effluent in which etoposide was not detected results in an MOE of > 3 000 000. The
MOE using the maximum modelled PEC would be > 2 000 000. Given the highly
conservative nature of the exposure inputs and the use of human data to derive a point
of departure for risk characterization, these MOEs support the determination that risks
from indirect exposure to etoposide are likely to be negligible.
It is therefore concluded that etoposide does not meet the criteria set out in paragraph
64(c) of CEPA 1999, as it is not entering the environment in a quantity or concentration
or under conditions that constitute or may constitute a danger in Canada to human life or
health.
9.1 Uncertainties in Evaluation of Risk to Human Health
There is uncertainty regarding the estimation of exposure due to the lack of
representative data on concentrations of etoposide in Canadian surface water or
drinking water and the use of models for estimating risk to human health. However,
confidence is high that actual exposures would be lower than the ones estimated from
both the models and the concentrations in effluent. This is supported by the data
available from other countries and the highly conservative default assumptions used.
The uncertainty in the human risk estimates could be reduced significantly by the use of
measured concentrations of etoposide in Canadian surface water and/or drinking water.
Potential exposures to etoposide could occur via other sources, such as ingestion of fish
or swimming in waters where the pharmaceutical is present, but these exposures are
expected to be much less than the exposure through drinking water and so are not
considered in this assessment.
Etoposide may also be used for additional off-label or veterinary uses that are not
considered in this assessment. The quantity of the substance being used for these
purposes is unknown, and so estimation of releases is not possible at this time.
Screening Assessment - Etoposide
It is recognized that the LTD represents an exposure level at which a desired
pharmacological response is achieved and further that at this exposure level, adverse
effects, in addition to intended effects, may occur in some patients. For certain
indications and certain classes of drugs, the nature of these unintended effects may be
severe. However, the LTD is developed for patients who require treatment for a
particular illness and therefore are likely to be more susceptible to potential effects than
a healthy individual. Although the use of the LTD provides a tier 1 type of assessment
that does not utilize all the toxicity data that may be available for this substance, the
highly conservative exposure defaults that have been used lead to significant margins
between the LTD and the estimated intakes. The LTD also allows for derivation of an
MOE based on a human dose as the point of departure, which is preferable to using a
point of departure developed using experimental animals.
10. Conclusion
Considering all available lines of evidence presented in this screening assessment,
there is low risk of harm to organisms or the broader integrity of the environment from
this substance. It is therefore concluded that etoposide does not meet the criteria under
paragraph 64(a) or 64(b) of CEPA 1999, as it is not entering the environment in a
quantity or concentration or under conditions that have or may have an immediate or
long-term harmful effect on the environment or its biological diversity or that constitute or
may constitute a danger to the environment on which life depends.
Based on the information presented in this screening assessment, it is concluded that
etoposide does not meet the criteria set out in paragraph 64(c) of CEPA 1999, as it is
not entering the environment in a quantity or concentration or under conditions that
constitute or may constitute a danger in Canada to human life or health.
It is therefore concluded that etoposide does not meet any of the criteria under section
64 of CEPA 1999.
Screening Assessment - Etoposide
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2014-09-02
Appendix A: Robust Study Summaries
Description of the Reliability Evaluation
To evaluate the reliability of studies for key ecological endpoints (i.e., inherent
toxicity to aquatic organisms, bioaccumulation potential, persistence), a strategy
generally analogous to the Klimisch approach (Klimisch et al. 1997) has been
developed. It involves the use of a standardized Robust Study Summary (RSS)
form and a scoring system to quantitatively evaluate the studies. The RSS form
is an adaptation of the OECD RSS templates (OECD 2002). It consists of a
checklist of criteria reflecting information on the test substance, method, test
organism, test design/conditions, ecological relevance and results (column 1).
Most items are weighted according to their criticality to the quality of the study
(column 2). For each item, the evaluator must indicate whether the item has been
addressed in the study by answering “Yes” (Y), “No” (N) or “Not applicable” (n/a)
(column 3). The most important or critical items (which describe
parameters/factors that have the most direct influence on the quality of the study)
have been given a higher weight (3 points), while the less critical items have
been given a lower score (1 or 2 points). The weighting is based on expert
judgement.
Once all the questions have been answered, an overall RSS score for the study
is calculated as:
Overall study score (%) =
∑W
∑W
Yes
× 100%
Yes + No
where:
WYes = weight of applicable “Yes” answers;
WYes+No = weight of applicable “Yes” and “No” answers.
The overall score’s corresponding reliability code and category are determined
using the four categories inspired from the Klimisch approach and based on the
score ranges as described in Table A.1.
Table A-1: Scoring grid for overall study reliability
Reliability code
Reliability category
1
High confidence
45
Overall study score
range
≥ 80%
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2
3
4
2014-09-02
Satisfactory confidence
Low confidence
Not acceptable
60–79%
40–59%
< 40%
The RSS for log Kow was performed on the study by Shah et al. 1989 (Table
A.2). The RSS score was 65%, and the reliability code was 2. Overall, the
reliability of this study was found to be satisfactory. Although it is predicted that
the level of confidence is satisfactory, the octanol–water partition coefficient
value should not be considered as the most relevant, because the test was
performed with the pharmaceutical formulation of etoposide instead of the pure
compound. Also, the quantity of etoposide added to the solution was higher than
its water solubility.
Table A.2: Robust study summary for log Kow (Shah et al. 1989)
Item
Weight
Response
Not easily, but basic
Could you repeat the experiment with
5
information is
available information?
presented
Is a clear objective stated?
1
Yes
Is water quality characterized or
2
No
identified (distilled or deionized)?
Are the results presented in detail,
3
No
clearly and understandably?
Are the data from a primary source
3
Yes
and not from a referenced article?
No. 10 mg of
etoposide was
added to 5 mL of
Was the chemical tested at
water and 5 mL of
concentrations below its water
5
octanol. 10 mg/10
solubility?
mL is one order of
magnitude over
etoposide’s water
solubility
Not mentioned, but
HPLC was used,
Were particulates absent?
2
therefore the
solution might have
been filtered
Was a reference chemical of known
3
Not mentioned
constant tested?
46
Mark
3
1
0
0
3
0
1
0
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2014-09-02
Were other fate processes
considered?
Was a control (blank) run?
Was temperature kept constant?
Was the experiment done near room
temperature (15–30°C)?
3
5
Yes; degradation
products
Not mentioned
Yes
3
Yes: 25°C
5
Is the purity of the test chemical
reported (> 98%)?
3
No, but it comes
from a drug
company and is
deemed to be pure
enough in the
formulation
No
1
Yes; Bristol-Myers
3
Was the chemical’s identity proven?
Is the source of the chemical
reported?
5
0
5
3
2
0
1
The RSS for water solubility was performed on the study by Shah et al. 1995
(Table A.3). The RSS score was 89%, and the reliability code was 1. Overall, the
reliability of this study has high confidence; however, the test was performed with
the pharmaceutical formulation of etoposide instead of the pure compound.
Table A.3: Robust study summary for water solubility (Shah et al. 1995)
Item
Weight
Response
Mark
Could you repeat the experiment with
5
Yes
5
available information?
Is a clear objective stated?
1
Yes
1
Is water quality characterized or
2
Yes, distilled
2
identified (distilled or deionized)?
Are the results presented in detail,
3
Tables are missing
1
clearly and understandably?
Are the data from a primary source
3
Yes
3
and not from a referenced article?
Was the chemical tested at
concentrations below its water
5
Yes
5
solubility?
Yes, filtered through
Were particulates absent?
2
a 0.45 µm
2
membrane filter
Was a reference chemical of known
3
Not mentioned
0
constant tested?
Were other fate processes
5
Yes, degradation
5
47
Screening Assessment - Etoposide
Item
considered?
Was a control (blank) run?
2014-09-02
Weight
Mark
3
Response
and photosensitivity
Not mentioned
Yes, approximately:
room temperature
Yes: Room
temperature
No, but it comes
from a drug
company and is
deemed to be pure
enough in the
formulation
No
1
Yes; Bristol-Myers
1
3
Was temperature kept constant?
5
Was the experiment done near room
temperature (15–30°C)?
3
Is the purity of the test chemical
reported (> 98%)?
3
Was the chemical’s identity proven?
Is the source of the chemical
reported?
0
3
3
2
0
The RSS for persistence in water was performed on the study by Shah et al.
1995 (Table A.4). The RSS score was 57.9%, and the reliability code was 3.
Overall, the reliability of this study is low.
Table A.4: Robust study summary for persistence in water (Shah et al.
1995)
Item
Weight Yes/No
Specify
Substance identity: chemical name(s)
n/a
Etoposide
Chemical composition of the substance
2
Y
Product was
used as
received
from the
drug
company,
product
monograph
is available
with detailed
information
Chemical purity
1
N
n/a
Reference
1
N
n/a
48
Screening Assessment - Etoposide
2014-09-02
OECD, EU, national or other standard method?
3
N
Justification of the method/protocol if a standard
method was not used
2
Y
GLP
3
n/a
Test type (i.e., hydrolysis, biodegradation, etc.)
Test conditions type (aerobic or anaerobic)
Test medium (water, sediment or soil)
n/a
n/a
n/a
Y
N
Y
Test duration
n/a
Y
Negative or positive controls?
1
Y
Number of replicates (including controls)
1
Y
Measured concentrations reported?
Analytical method / instrument
Type of biodegradation (ready or inherent) reported?
When type of biodegradation (ready or inherent) is
not reported, if there is indirect information allowing
identification of biodegradation type?
Inoculum source
Inoculum concentration or number of
microorganisms
Were inoculum pre-conditioning and pre-adaptation
reported?
Were inoculum pre-conditioning and pre-adaptation
appropriate for the method used?
3
1
2
N
Y
n/a
n/a
Explanations
are provided
for details of
experiment
Not
applicable:
the study
was
completed in
1989, and
GLP was not
implemented
Hydrolysis
Anaerobic
Water
Until
remaining
etoposide
level was
negligible
Negative
Three
replicates
n/a
HPLC
n/a
1
n/a
n/a
1
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
Temperature
1
1
n/a
1
49
Screening Assessment - Etoposide
2014-09-02
Has percentage degradation of the reference
compound reached the pass levels by day 14?
n/a
n/a
n/a
Soil: soil moisture reported?
Soil and sediments: background soil organic
matter content reported?
1
n/a
n/a
1
n/a
n/a
Soil and sediments: clay content reported?
1
n/a
n/a
Soil and sediments: cation exchange capacity
reported?
1
n/a
n/a
pH values reported?
1
Y
Temperature
1
Y
Were appropriate concentrations of the substance
used?
1
Y
If solvent was used, was it done appropriately?
1
Y
Temperature
1
n/a
1.3; 2.03;
3.05; 5.00;
6.15; 7.30;
8.00; 10.00
25°C
Top range of
water
solubility
limit
The solvent
(buffer) has
no
interaction
with the
tested
molecule,
but controls
pH
n/a
Light source
Light spectrum (nm)
Relative intensity based on sunlight intensity
1
1
1
Spectrum of a substance
1
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
Indirect photolysis: sensitizer (type)
Indirect photolysis: concentration of sensitizer
1
1
n/a
n/a
n/a
n/a
n/a
n/a
Many. See
text.
Endpoint and value
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Screening Assessment - Etoposide
2014-09-02
Breakdown products
n/a
n/a
Four
breakdown
products are
observed
but not
identified
Abbreviations: EU, European Union; GLP, good laboratory practice; HPLC, high-performance liquid
chromatography; N, no; n/a, not applicable; OECD, Organisation for Economic Co-operation and
Development; Y, yes
The RSS for aquatic toxicity was performed on the study by Zounková et al. 2007
(Table A.5). The RSS score was 76.7%, and the reliability code was 2. Overall,
the reliability of this study is satisfactory.
Table A.5: Robust study summary for aquatic toxicity (Zounková et al.
2007)
Item
Weight Yes/No
Substance identity: chemical name(s)
Specify
n/a
Y
Chemical composition of the substance
2
Y
Chemical purity
Persistence/stability of test substance in
aquatic solution reported?
1
N
Etoposide
The drug was
supplied by a
hospital, the
composition is
described in the
product monograph
n/a
1
N
n/a
Reference
1
Y
OECD, EU, national or other standard
method?
3
Y
Justification of the method/protocol if a
standard method was not used
2
n/a
GLP
Organism identity: name
51
3
Y
n/a
n/a
European
standards
The Czech
standard (identical
to the European
standard EN ISO
6341:1996)
n/a
Follows standards.
Duplicates,
statistical analysis
and test duration
were adequate.
Pseudomonas
putida,
Screening Assessment - Etoposide
2014-09-02
Item
Weight Yes/No
Specify
Pseudokirchneriella
subcapitata,
Daphnia magna
Latin or both Latin & common names
reported?
1
Y
Life cycle age / stage of test organism
1
Y
Length and/or weight
Sex
1
1
n/a
n/a
Number of organisms per replicate
1
Y
Organism loading rate
1
Y
Food type and feeding periods during the
acclimation period
Test type (acute or chronic
Experiment type (laboratory or field)
1
n/a
n/a
n/a
Y
Y
Exposure pathways (food, water, both)
n/a
Y
Exposure duration
n/a
Y
Negative or positive controls (specify)
1
Y
Number of replicates (including controls)
Nominal concentrations reported?
Measured concentrations reported?
Food type and feeding periods during the
long-term tests
1
1
3
Y
N
N
1
n/a
Were concentrations measured
periodically (especially in the chronic
test)?
1
Y
Were the exposure media conditions
3
N
52
n/a
Yes for daphnia,
not applicable for
the other
organisms
n/a
n/a
20 daphnia per vial.
Not applicable for
other organisms
5 animals/10 ml for
daphnia, not
applicable for the
other organisms
n/a. Acute studies
Acute
Laboratory
Direct contact via
water
16 hours bacteria,
96 hours algae and
48 hours daphnid
Negative. Control
organisms were in
buffer.
Triplicate
n/a
n/a
n/a
Not mentioned for
bacteria. For algae
and daphnia, every
24 hours (daphnia
Zounková 2010)
Water properties
Screening Assessment - Etoposide
2014-09-02
Item
Weight Yes/No
relevant to the particular chemical
reported? (e.g., for the metal toxicity –
pH, DOC/TOC, water hardness,
temperature)
Specify
are not mentioned
16 hours:8 hours
light:dark cycle
(Zounková 2010)
Stock buffered
saline solution and
further diluted with
water
Photoperiod and light intensity
1
Y
Stock and test solution preparation
1
Y
1
Y
1% v/v ethanol
1
Y
1% v/v ethanol
1
N
Was solubilizer/emulsifier used, if the
chemical was poorly soluble or unstable?
If solubilizer/emulsifier was used, was its
concentration reported?
If solubilizer/emulsifier was used, was its
ecotoxicity reported?
For algae and
daphnia (Zounková
2010)
Analysis of
variance and
Dunnett’s test
Analytical monitoring intervals
1
Y
Statistical methods used
1
Y
n/a
n/a
3
Y
Daphnia magna
found in Canada
1
Y
EU standards used
2
Y
EU standards used
1
Y
EU standards used
1
Y
Mentioned in
Was the endpoint directly caused by the
chemical’s toxicity, not by organism’s
health (e.g., when mortality in the control
> 10%) or physical effects (e.g., “shading
effect”)?
Was the test organism relevant to the
Canadian environment?
Were the test conditions (pH,
temperature, DO, etc.) typical for the test
organism?
Does system type and design (static,
semi-static, flow-through; sealed or open;
etc.) correspond to the substance’s
properties and organism’s nature/habits?
Was pH of the test water within the range
typical for the Canadian environment (6
to 9)?
Was temperature of the test water within
53
n/a
Screening Assessment - Etoposide
2014-09-02
Item
Weight Yes/No
the range typical for the Canadian
environment (5 to 27°C)?
Was toxicity value below the chemical’s
water solubility?
Toxicity values (specify endpoint and
value)
Other endpoints reported – e.g.,
BCF/BAF, LOEC/NOEC (specify)?
Other adverse effects (e.g.,
carcinogenicity, mutagenicity) reported?
Specify
Zounková 2010
(18–23°C)
Generally yes. For
the values over the
water solubility,
ethanol in the
product is expected
to solubilize
etoposide
3
Y
n/a
n/a
n/a
Y
LOEC/NOEC
n/a
Y
Genotoxicity
Many. See text
Abbreviations: BAF, bioaccumulation factor; BCF, bioconcentration factor; DO, dissolved oxygen; DOC,
dissolved organic carbon; EU, European Union; GLP, good laboratory practice; HPLC, high-performance
liquid chromatography; LOEC, lowest-observed-effect concentration; N, no; n/a, not applicable; NOEC, noobserved-effect concentration; OECD, Organisation for Economic Co-operation and Development; TOC,
total organic carbon; Y, yes
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Screening Assessment - Etoposide
2014-09-02
Appendix B: PBT 5 Model Input Summary Tables
Table B.1: PBT model input summary table for physical-chemical models
EPI Suite (all models, including
Model input parameters
AOPWIN, KOCWIN, BCFBAF, BIOWIN
and ECOSAR)
SMILES code
X
Molecular weight (g/mol)
NA
Melting point (°C)
X
Boiling point (°C)
X
Data temperature (°C)
NA
3
Density (kg/m )
NA
Vapour pressure (Pa)
X
3
Henry’s Law constant (Pa·m /mol)
X
Log Kaw (dimensionless)
NA
Log Kow (dimensionless)
X
Kow (dimensionless)
NA
Log Koc (L/kg)
NA
Water solubility (mg/L)
X
Log Koa (dimensionless)
NA
Abbreviations: Kaw, air–water partition coefficient; Koa, octanol–air partition coefficient; Koc, organic carbon–
water partition coefficient; Kow, octanol–water partition coefficient; SMILES, simplified molecular input line
entry system; NA, not applicable
Table B.2: PBT model input summary table for fate modelling
STP (1), ASTreat
EQC
(2), SimpleTreat
(required
(3), (required
inputs are
inputs are
different if
Model input parameters
different,
Type I vs.
depending on
Type II
model)
chemical)
SMILES code
NA
NA
Molecular weight (g/mol)
X (1, 2, 3)
X (I, II)
Melting point (°C)
NA
X (I)
5
Persistence, bioaccumulation, toxicity.
55
Arnot-,
Gobas
BCF/BAF
Model
X
NA
NA
Screening Assessment - Etoposide
Model input parameters
Boiling point (°C)
Data temperature (°C)
Density (kg/m3)
Vapour pressure (Pa)
Henry’s Law constant
(Pa·m3/mol)
Log Kaw (dimensionless)
Log Kow (dimensionless)
Kow (dimensionless)
Log Koc (L/kg)
Water solubility (mg/L)
Log Koa (dimensionless)
Soil–water partition
coefficient (L/kg)a
Sediment–water partition
coefficient (L/kg)a
Suspended particles–water
partition coefficient (L/kg)a
Fish–water partition
coefficient (L/kg)b
Aerosol–water partition
coefficient (dimensionless)c
Vegetation–water partition
coefficient (dimensionless)a
Enthalpy (Kow)
Enthalpy (Kaw)
Half-life in air (days)
Half-life in water (days)
Half-life in sediment (days)
Half-life in soil (days)
Half-life in vegetation
(days)d
Metabolic rate constant
(1/day)
2014-09-02
STP (1), ASTreat
(2), SimpleTreat
(3), (required
inputs are
different,
depending on
model)
NA
NA
X (2)
X (1, 3)
EQC
(required
inputs are
different if
Type I vs.
Type II
chemical)
X (I, II)
X (I)
X (3)
Arnot-,
Gobas
BCF/BAF
Model
NA
NA
NA
NA
X
X (2)
X (1)
X (2, 3)
NA
X (1, 3)
X (II)
X (I)
NA
NA
X (I)
NA
X
NA
NA
X
NA
NA
X (II)
NA
NA
X (II)
NA
X (2)
X (II)
NA
NA
X (II)
NA
NA
X (II)
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
X (I, II)
X (I, II)
X (I, II)
X (I, II)
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
56
*
Screening Assessment - Etoposide
Model input parameters
Biodegradation rate
constant (1/day or 1/h) –
specify
2014-09-02
STP (1), ASTreat
(2), SimpleTreat
(3), (required
inputs are
different,
depending on
model)
X
EQC
(required
inputs are
different if
Type I vs.
Type II
chemical)
Arnot-,
Gobas
BCF/BAF
Model
(3, 1/h)
NA
NA
X (1)
NA
NA
X (1)
NA
NA
X (1)
NA
NA
(2, 1/day)
Biodegradation half-life in
primary clarifier (t½-p) (h)
Biodegradation half-life in
aeration vessel (t½-s) (h)
Biodegradation half-life in
settling tank (t½-s) (h)
Abbreviations: BCF, bioconcentration factor; Kaw, air–water partition coefficient; Koa, octanol–air partition
coefficient; Koc, organic carbon–water partition coefficient; Kow, octanol–water partition coefficient; SMILES,
simplified molecular input line entry system; NA, not applicable
a
Derived from log Koc.
b
Derived from BCF data.
c
Default value.
d
Derived from half-life in water.
Table B.3: PBT model input summary table for PBT profiling and
ecotoxicity
CPOPs (including
CATALOGIC, BCF
AIES / DS TOPKAT/
Model input parameters
Mitigating Factors
ASTER
Model, OASIS
Toxicity Model)
SMILES code
X
X
Molecular weight (g/mol)
NA
NA
Melting point (°C)
NA
NA
Boiling point (°C)
NA
NA
Data temperature (°C)
NA
NA
Density (kg/m3)
NA
NA
Vapour pressure (Pa)
NA
NA
Henry’s Law constant
NA
NA
(Pa·m3/mol)
Log Kaw (dimensionless)
NA
NA
57
Screening Assessment - Etoposide
2014-09-02
CPOPs (including
CATALOGIC, BCF
AIES / DS TOPKAT/
Mitigating Factors
Model input parameters
ASTER
Model, OASIS
Toxicity Model)
Log Kow (dimensionless)
X
X
Kow (dimensionless)
NA
NA
Log Koc (L/kg)
NA
NA
Water solubility (mg/L)
X
X
Log Koa (dimensionless)
NA
NA
Abbreviations: AIES, Artificial Intelligence Expert System; Kaw, air–water partition
coefficient; Koa, octanol–air partition coefficient; Koc, organic carbon–water
partition coefficient; Kow, octanol–water partition coefficient; SMILES, simplified
molecular input line entry system; NA, not applicable
58
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