Estimates Of Exposures And Risks To Aquatic Organisms From Releases Of
Triclosan To Surface Water As A Result Of Uses Under EPA’S
Jurisdiction

[NOTE:  Confidential Business Information (CBI) has been removed from
this document]

 

Patricia Jennings

September 4, 2008

ESTIMATES OF EXPOSURES AND RISKS TO AQUATIC ORGANISMS FROM RELEASES OF
TRICLOSAN TO SURFACE WATER AS A RESULT OF USES UNDER EPA’S
JURISDICTION

INTRODUCTION

The Regulatory Management Branch II of the Antimicrobials Division (AD)
requested the Risk Assessment and Science Support Branch (RASSB) of AD
to provide estimates of exposures and risks to aquatic organisms from
surface water releases of triclosan from uses under EPA’s
jurisdiction.  Triclosan is regulated by both the U.S. Environmental
Protection Agency (EPA) and the U.S. Food and Drug Administration (FDA).
 The EPA regulates the antimicrobial uses of triclosan when used as a
bacteriostat, fungistat, mildewistat, and deodorizer.  The
FDA-registered uses of triclosan include hand soaps, toothpaste,
deodorants, laundry detergent, fabric softeners, facial tissues,
antiseptics for wound care, and medical devices.  General categories of
antimicrobial uses of triclosan include use in commercial,
institutional, and industrial premises and equipment; residential and
public access premises; and as a materials preservative.  Specific
information on the use profile for triclosan used as an antimicrobial
pesticide is posted on EPA’s website at   HYPERLINK
"http://www.epa.gov/oppsrrd1/REDs/factsheets/triclosan_fs.htm" 
http://www.epa.gov/oppsrrd1/REDs/factsheets/triclosan_fs.htm .  Some
common specific uses of triclosan include its use as a materials
preservative in textiles and plastics.

METHODOLOGY AND SCOPE OF THIS ANALYSIS

The Antimicrobials Division of EPA evaluates exposures and risks to
aquatic organisms from releases of antimicrobial pesticides to surface
water.  Antimicrobial pesticides may potentially be released to surface
water during their manufacture, processing, industrial use, commercial
use, and consumer use.  The Exposure and Fate Assessment Screening Tool,
Version 2.0 (E-FAST 2) developed by EPA/OPPTS/OPPT is a screening-level
computer tool that is used to estimate concentrations of a chemical in
surface water to which aquatic organisms may be exposed as a result of
these releases.  The data and tools needed to estimate exposure to
aquatic organisms from releases of a chemical to surface water from
manufacture, processing, industrial use, and commercial use are
different from those needed to estimate exposures to aquatic organisms
from consumer use.  The general population and ecological exposures from
industrial uses module of E-FAST 2 is used to estimate exposure to
aquatic organisms from releases of a chemical to surface water from
manufacture, processing, industrial use, and commercial use.  The
Down-the-Drain module of E-FAST 2 is used to estimate exposure to
aquatic organisms from releases of a chemical to surface water from
consumer use.

Data Required for the General Population and Ecological Exposures Module

Analysis of exposures to aquatic organisms from releases of chemicals to
surface water from manufacture, processing, industrial use, and
commercial use requires data including: (1) the amount of chemical
released on a daily basis to surface water from each facility that
discharges the chemical of concern; (2) the location of facilities that
discharge the chemical of concern to surface water or if that
information is not available, the representative Standard Industrial
Classification (SIC) code for facilities that discharge the chemical of
concern to surface water; (3) the number of days of release per year for
each facility or facility classification that discharges the chemical of
concern; (4) the number of industrial facilities releasing the chemical
of concern to surface water; and (5) concentrations of the chemical of
concern to aquatic organisms.  The ChemSteer model developed by OPPT or
an approach based on this model can be used to estimate the amount of
chemical released to surface water for each day of discharge for each
discharge site.  This information, along with the other input parameters
delineated above can be used to run the general population and
ecological exposures from industrial uses module of E-FAST 2.

Data Required for the Down-the-Drain Module

Analysis of exposures to aquatic organisms from releases of chemicals to
surface water from consumer use requires data including: (1) an estimate
of the wastewater treatment plant influent volume; (2) the percent
removal of the chemical during wastewater treatment; and (3)
concentrations of the chemical of concern to aquatic organisms.  These
input parameters are used to run the Down-the-Drain module of E-FAST 2. 

Approach for Estimating Exposures from Down-the-Drain Releases

For this screening level analysis of exposures to aquatic organisms from
uses of triclosan under EPA’s jurisdiction, a simplifying assumption
is that all of the triclosan under EPA’s jurisdiction is released to
surface water as a result of consumer uses.  Estimates of exposures to
aquatic organisms from releases to surface water from its manufacture,
processing, industrial use, and commercial use are therefore, assumed to
be negligible.  Releases of triclosan to surface water from consumer
uses are assumed to result entirely from disposal of consumer products
into household wastewater. Triclosan is assumed to be released into
household wastewater during washing and rinsing of products treated with
triclosan as a materials preservative or other functional component. 
For this analysis, AD used the Down-the-Drain module of E-FAST to
provide screening-level estimates of potential exposures and risks to
aquatic organisms from releases to household wastewaters from consumer
uses of triclosan.

The methodology for the Down-the-Drain module assumes that household
wastewater undergoes treatment at a local wastewater treatment plant and
that treated effluent is subsequently discharged into surface waters. 
The Down-the-Drain module provides estimates of exposure to aquatic
organisms and exposure to humans from ingestion of drinking water and
fish that may be exposed to these household wastewater releases.  In
addition, there is a probabilistic dilution model (PDM) option that
provides estimates of the number of days per year that the concentration
of a chemical in surface water exceeds the concentration of concern for
aquatic organisms.

This analysis focused on exposure of aquatic organisms to triclosan and
did not consider potential exposure to humans from ingestion of drinking
water and fish contaminated with triclosan.  The PDM option of the
Down-the-Drain module was used to estimate the number of days of
exceedance of concentrations of concern for aquatic organisms downstream
of waste water treatment plants (WWTPs).  Input parameters needed to run
the Down-the-Drain module of E-FAST 2 include: (1) the wastewater
treatment plant (WWTP) influent volume of the chemical; (2) the percent
of chemical removed during wastewater treatment; (3) the
bioconcentration factor (BCF) of the chemical in fish; and (4) the
duration of exposure.  These last two input parameters are used to
estimate exposure to humans from ingestion of drinking water and fish
and are not used to estimate potential exposures to aquatic organisms.
Table 1 presents data for input parameters used to run the
Down-the-Drain module of E-FAST 2.

   TABLE 1- INPUT DATA FOR THE DOWN-THE-DRAIN MODULE OF E-FAST 2

WWTP Influent Volume (kg/yr)	Value removed

Bioconcentration Factor in Fish (BCF)	Value removed 

Percent WWTP removal of Triclosan 	Value removed

Exposure duration (years of use)	Value removed



The percent of chemical removed during wastewater treatment was assumed
to be (Value removed) percent.  Measurements reported from benchtop fate
testing indicated that 81-92 percent of triclosan was biodegraded
(Federle et al., 2002).  There is also potential for triclosan
undergoing wastewater treatment to adsorb to sludge and other solids. 
After a review of available literature and modeling results regarding
the environmental fate of triclosan during wastewater treatment, (…
rest of statement removed…).  Companies that manufacture and import
triclosan reported annual volumes for uses under EPA’s jurisdiction to
be (… rest of statement removed…).  As a simplifying assumption, all
of the triclosan reported to be produced or imported for uses under
EPA’s jurisdiction was assumed to enter the influent of wastewater
treatment plants that receive household wastewaters.

For the PDM option of the Down-the-Drain module, values of the
concentrations of triclosan of concern to aquatic organisms were
selected for acute and endangered species risk presumptions for aquatic
animals and plants using acute toxicity endpoint values for species
intended to represent freshwater fish, freshwater invertebrates, and
aquatic plants.  For the acute risk presumption for aquatic animals, the
concentration of concern was calculated by multiplying the estimated
surface water concentration of triclosan by 0.5.  For the endangered
species risk presumption for aquatic animals, the concentration of
concern was calculated by multiplying the estimated surface water
concentration of triclosan by 0.05.  For the acute and endangered
species risk presumptions for aquatic plants, the concentration of
concern was assumed to be equal to the estimated surface water
concentration for triclosan.  The measurement endpoint used for the
acute risk presumption for aquatic plants is the EC50.  The measurement
endpoint used for the endangered species risk presumption for aquatic
plants is the NOAEC.  Estimates of the number of days of exceedance of
concentrations of concern for aquatic organisms downstream of waste
water treatment plants were generated for both high-end and average case
scenarios.

The Down-the-Drain module of E-FAST 2 provides both high-end
time-averaged surface water concentrations and median time-averaged
surface water concentrations of a chemical released by a wastewater
treatment facility receiving household wastewater. The high-end scenario
uses surface water concentrations based on the 10th percentile stream
dilution factor for streams to which wastewater treatment facilities
that receive household wastewaters discharge.  The average case scenario
uses surface water concentrations based on the 50th percentile stream
dilution factor for streams to which wastewater treatment facilities
that receive household wastewaters discharge.  A stream dilution factor
is calculated by dividing the flow that represents  the receiving stream
flow downstream of a wastewater treatment plant by the wastewater
treatment plant effluent flow.  The stream flow data and stream dilution
factors are ranked and the results are reported in terms of percentiles
of the distribution of data.  To estimate potential acute and chronic
aquatic life impacts, the PDM option uses 1Q10 and 7Q10 stream flows. 
The 1Q10 is the lowest flow for a single day during any 10-year period. 
The 7Q10 is the lowest consecutive 7-day average flow during any 10-year
period.  Estimates for a high-end scenario are based on the averaged
probability of exceedance of the 10 percent of WWTPs that have the
highest probability of exceedance of the COC following treatment based
on the estimated typical daily per capita wastewater volume released. 
Estimates for an average case scenario are based on WWTPs that have an
average probability of exceedance of the COC following treatment based
on the estimated typical daily per capita wastewater volume released. 

AQUATIC EXPOSURE AND RISK ASSESSMENT

Results of the assessment of exposure and risk to aquatic organisms from
uses of triclosan under EPA’s jurisdiction that are disposed in
household wastewaters entering wastewater treatment plants are presented
for acute risk presumptions for aquatic animals; endangered species risk
presumptions for aquatic animals; and acute and endangered species risk
presumptions for aquatic plants.  Table 2 presents concentrations of
concern for acute risk presumptions for aquatic animals and the
corresponding numbers of days of exceedance for these levels of concern
based on high-end and average case scenarios.  When using the PDM option
of E-FAST 2, EPA/OPPT considers risks to be significant if the acute
toxicity value for the most sensitive freshwater fish or invertebrate
tested exceeds the concentration of concern in surface water for 4 days
or more.  Estimated concentrations of triclosan in surface water did not
exceed concentrations of concern for acute risk presumptions for aquatic
animals.

TABLE 2 – NUMBER OF DAYS EXCEEDANCE OF CONCENTRATIONS OF CONCERN FOR
ACUTE RISK PRESUMPTIONS FOR AQUATIC ANIMALS

Test Species	Measurement Endpoint (mg/L)	Concentration of Concern (ug/L)
Basis of Concentration of Concern	High-End Scenario

(# days COC exceeded)	Average Scenario (# days COC  exceeded)

Rainbow trout (Oncorhynchus mykiss)	freshwater fish acute LC50 = 0.288
144	Core data from OPP guideline study	0	0

Cladoceran (Ceriodaphnia dubia)	freshwater invertebrate acute EC50 =
0.13	65	EPA Office of Water (U.S. EPA, 2007	0	0

Waterflea (Daphnia magna)	freshwater invertebrate acute EC50 = 0.39	195
Supplemental data from OPP study that does not meet guideline
requirements	0	0



Table 3 presents concentrations of concern for endangered species risk
presumptions for aquatic animals and the corresponding numbers of days
of exceedance for these levels of concern based on high-end and average
case scenarios.  Estimated concentrations of triclosan in surface water
did not exceed concentrations of concern for endangered species risk
presumptions for aquatic animals.

TABLE 3 – NUMBER OF DAYS EXCEEDANCE OF CONCENTRATIONS OF CONCERN FOR 
ENDANGERED SPECIES RISK PRESUMPTIONS FOR AQUATIC ANIMALS

Test Species	Measurement Endpoint (mg/L)	Concentration of Concern (ug/L)
Basis of Concentration of Concern	High-End Scenario

(# days COC exceeded)	Average Scenario (# days COC  exceeded)

Rainbow trout (Oncorhynchus mykiss)	freshwater fish acute LC50 = 0.288
144	Core data from OPP guideline study	0	0

Cladoceran (Ceriodaphnia dubia)	freshwater invertebrate acute EC50 =
0.13	65	EPA Office of Water (U.S. EPA, 2007	0	0

Waterflea (Daphnia magna)	freshwater invertebrate acute EC50 = 0.39	195
Supplemental data from OPP study that does not meet guideline
requirements	0	0



Table 4 presents concentrations of concern for acute risk presumptions
for aquatic plants and the corresponding numbers of days of exceedance
for these levels of concern based on high-end and average case
scenarios.  Note that measurement endpoints based on EC05 or NOAEC that
could be used for endangered species risk presumptions for non-vascular
freshwater plants were not available.  However, a NOAEC value of 0.0125
mg/L based on core data from an OPP guideline study was available for a
representative vascular aquatic plant species, the duckweed, Lemna
gibba.  This NOAEC value corresponds to a concentration of concern for
triclosan in surface water of 12.5 ug/L.  The PDM option of the
Down-the-Drain module of E-FAST 2 predicted no exceedances of the
concentration of concern for triclosan for endangered species risk
presumptions for aquatic vascular plants..  

Although estimated concentrations of triclosan in surface water were not
predicted to exceed concentrations of concern for acute risk
presumptions for species tested to represent vascular freshwater plants,
concentrations of triclosan in surface water were predicted to exceed
concentrations of concern for acute risk presumptions for species that
represent non-vascular freshwater plants (i.e., algae).    When using
the PDM option of E-FAST 2, for the most sensitive algal species tested,
if the concentration of concern is exceeded for 4 days or less, OPPT
determines the potential for significant risk on a case-by-case basis. 
The number of days of exceedance of the concentration of concern is 1
day for blue-green algae, 5 days for green algae, and 57 days for
Chlamydomonas sp.  The concentration of concern of 0.15 ug/L for the
algal species, Chlamydomonas, that was used to run the PDM option of the
Down-the-Drain module of E-FAST 2 was based on findings of a significant
reduction of this genera of algae based on an evaluation of the effects
of triclosan on natural freshwater algae located above and below a
wastewater treatment plant (Wilson et al. 2003).  Although this
evaluation is considered supplemental data, it indicates the need for
additional investigation of shifts in algal communities, reductions in
biomass, and effects on higher trophic levels (Wilson et al. 2003). 
Data on the high toxicity of triclosan to different types of algae and
on concentrations of triclosan measured in surface waters indicate that
the presence of triclosan in surface water at levels of concern to algae
may have the potential to affect the structure and function of algal
communities in freshwater stream ecosystems, particularly immediately
downstream of effluents from wastewater treatment facilities that treat
household wastewaters.  Significant adverse effects to aquatic algae,
which are primary producers in aquatic ecosystems, might potentially
impair or destroy the balance of aquatic ecosystems.  

TABLE 4 – NUMBER OF DAYS EXCEEDANCE OF CONCENTRATIONS OF CONCERN FOR 
ACUTE RISK PRESUMPTIONS FOR AQUATIC PLANTS

Test Species	Measurement Endpoint (mg/L)	Concentration of Concern (ug/L)
Basis of Concentration of Concern	High-End Scenario

(# days COC exceeded)	Average Scenario (# days COC  exceeded)

Chlamydomonas sp.	Concentration in freshwater that caused a significant
reduction in this species is 0.00015 	0.15	Supplemental data (Wilson et
al. 2003)	57	6

Green algae (Scenedesmus subspicatus)	Non-vascular aquatic plant EC50 =
0.0007	0.7	EPA Office of Water (U.S. EPA 2007)	5	<1

Blue-green cyanobacteria (Anabaena flos-aquae)	Non-vascular aquatic
plant EC50 = 0.0012	1.2	Core data from OPP guideline study	1	0

Duckweed (Lemna gibba)	Vascular aquatic plant NOAEC = 0.0125	12.5	Core
data from OPP guideline study	0	0

	

 NOTE:  Confidential Business Information (CBI) has been removed from
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