UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

 OFFICE OF

                                                                        
                                    PREVENTION, PESTICIDES AND 

         TOXIC SUBSTANCES

September 11, 2008

MEMORANDUM

SUBJECT:	Revised Environmental Fate Science Chapter for the Triclosan
Reregistration Eligibility Decision (RED) Document

	DP Barcode:  343543		Reregistration Case No.:  2340

FROM:	Srinivas Gowda, Microbiologist/Chemist

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

TO:			Mark Hartman, Branch Chief

Diane Isbell, Team Leader

Heather Garvie, Chemical Review Manager

Regulatory Management Branch II

Antimicrobials Division (7510P)

Timothy McMahon, Risk Assessor

THRU:	Siroos Mostaghimi, Team Leader, Team one

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

Norman Cook, Branch Chief

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

Chemical Name				PC Code	CAS#		Common Name

5-Chloro-2-  (2,4-dichlorophenoxy)phenol	54901		3380-34-5	Triclosan

Attached is the Revised Environmental Fate Science Chapter for the
Triclosan RED Document as per the Ciba Corporation’s and Har-Met
International, Inc’s Sixty-Day Public Comments.

5-CHLORO-2-(2,4-DICHLOROPHENOXY)PHENOL

(TRICLOSAN)

REVISED ENVIRONMENTAL FATE SCIENCE CHAPTER

EXECUTIVE SUMMARY

	Triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol] is used primarily as
a bacteriostat, fungicide/fungistat, and mold/mildewcide.  Use sites for
triclosan include commercial, institutional and industrial premises and
equipment, residential and public access premises, and as a material
preservative.  Four of the five required guideline studies for an
environmental fate assessment have been submitted for triclosan;
however, one of the four submitted studies (hydrolysis) was found to be
a preliminary test.  The Agency is using these environmental fate
studies for the assessment of triclosan to fulfill the reregistration
requirements.

	Triclosan is a white crystalline powder with low solubility in water
(12 ppm).  The chemical structures of triclosan (Figure 1) and its
degradate (Figure 2) DCP (2,4-dichlorophenol) are as follows:

 

Figure 1.  Molecular Structure of Triclosan 		Figure 2.  DCP
(2,4-dichlorophenol)

	Triclosan is hydrolytically stable under abiotic and buffered
conditions over the pH 4-9 range based on data from a preliminary test
at 50°C.  Photolytically, triclosan degrades rapidly under continuous
irradiation from artificial light at 25°C in a pH 7 aqueous solution,
with a calculated aqueous photolytic half-life of 41 minutes.  One major
transformation product was identified, DCP (2,4-dichlorophenol), which
was present at a maximum of 93.8-96.6% of the applied dose at 240
minutes post-treatment.  Triclosan degrades rapidly in aerobic soils
maintained in darkness at 20 ( 2°C, with calculated half-lives of
2.9-3.8 days.  One major transformation product was identified, methyl
triclosan, at maximum averages of 13.5-24.0% of the applied dose at
14-28 days post-treatment.  In aerobic water-sediment systems maintained
in darkness at 20 ( 2°C, triclosan degraded with calculated nonlinear
half-lives of 1.3-1.4 days in the water, 53.7-60.3 days in the sediment,
and 39.8-55.9 days in the total system.  The major transformation
product, identified as methyl triclosan, was a maximum average of 4.8%
of the applied dose at 104 days post-treatment (sediment; sandy loam
system).  

	The Agency used its databases (EPI Suite) and open literature (TOXNET)
to conduct this environmental fate risk assessment.

	In soil, triclosan is expected to be immobile based on an estimated Koc
of 9,200.  Triclosan is not expected to volatilize from soil (moist or
dry) or water surfaces based on an estimated Henry’s Law constant of
1.5 x 10-7 atm-m3/mole.  Triclosan partially exists in the dissociated
form in the environment based on a pKa of 7.9, and anions do not
generally adsorb more strongly to organic carbon and clay than their
neutral counterparts.  In aquatic environments, triclosan is expected to
adsorb to suspended solids and sediments and may bioaccumulate (Kow
4.76), posing a concern for aquatic organisms.  There is also a low to
moderate potential for bioconcentration in aquatic organisms based on a
BCF range of 2.7 to 90.

	Hydrolysis is not expected to be an important environmental fate
process due to the stability of triclosan in the presence of strong
acids and bases.  However, triclosan is susceptible to degradation via
aqueous photolysis, with a half-life of <1 hour under abiotic
conditions, and up to 10 days in lake water.  An atmospheric half-life
of 8 hours has also been estimated based on the reaction of triclosan
with photochemically produced hydroxyl radicals.  Additionally,
triclosan may be susceptible to biodegradation based on the presence of
methyl-triclosan following wastewater treatment.  In the laboratory,
triclosan also degraded to methyl triclosan via aerobic soil and aquatic
metabolism, with half-lives of <4 and <1.5 days, respectively and up to
60-days in water-sediment systems.

  SEQ CHAPTER \h \r 1 From published literature studies on the
occurrence of triclosan in waste water treatment plants, treatment plant
efficiency, and open water measurements of triclosan, the majority
suggest that aerobic biodegradation is one of the major and most
efficient biodegradation pathways (70-80%) through which triclosan and
its by-products are removed from the aquatic environment with actual
efficiencies ranging from 53-99% (Kanda et al., 2003) in activated
sludge plants and 58-86% in trickle down filtration (McAvoy et al.,
2002).  Another pathway of removing triclosan from water in wastewater
treatment plants is through the sorption of triclosan and associated
by-products to particles and sludge (10-15%) because of the chemical’s
medium to high hydrophobicity (Agüera et al., 2003; Gomez et al., 2007;
Kanda et al., 2003; Lee and Peart, 2002; Bester, 2003 and 2005; Xia et
al., 2005).  Benchtop fate testing of triclosan found that 1.5-4.5% was
sorbed to activated sludge and 81-92% was biodegraded (Federle et al.,
2002).

triclosan residue in Ohio showed a range of 0.5 to 15.6 μg/g (dry
weight) and there were higher concentrations of triclosan observed in
anaerobic sludge as compared to aerobic sludge (McAvoy et al., 2002). 
Other countries where sludge samples were analyzed for triclosan are as
follows: Canada found 370 ng/g (Lee and Peart, 2002); Germany found
1000-8000 ng/g (Bester, 2003 and 2005); Greece found 1,840 ng/g (Gatidou
et al. 2007); Spain found 420-5400 ng/g (Morales et al., 2005); and 19
WWTP  analyzed in Australia had a range of 90 - 16,790 ng/g dry weight
and a median of 2,320 ng/g (Ying and Kookana, 2007).

Effluent concentrations from wastewater treatment plants in the US were
10-21 ng/L in Louisiana (Boyd et al., 2003); 63 ng/L in the upper
Detroit river (Hua et al., 2005); 72 ng/L in Arlington, Virginia (Thomas
and Foster, 2004); 110 ng/L in North Texas (Waltman et al., 2006); and
the highest was 200-2700 ng/L in Ohio (McAvoy et al., 2002). Effluent
concentrations from wastewater treatment plants in other countries were
measured to be 160 ng/L (Lee et al., 2003) or 50-360 ng/L in Canada (Lee
et al., 2005); 50 ng/L (Bester, 2003), 10-600 ng/L (Bester, 2005), or
180 ng/L (Wind et al., 2004) in Germany; 160 ng/L in Sweden (Bendz et
al., 2005); 430 ng/L (31.2 μg/g particulate matter), 1120 ng/L (16.1
μg/g particulate matter), or 230 ng/L (22.4 μg/g particulate matter)
in three different WWTP in Greece (Gatidou et al. 2007); 80-400 ng/L in
Spain (Gomez et al., 2007); 100-269,000 ng/L in Spain (Mezcua et al.,
2004); 0.15±0.08 mg/person in 5 European countries (Paxeus, 2004); 340
or 1100 ng/L, for trickle filtration and activated sludge treatment
plant in England (Sabaliunas et al., 2003); 42-213 ng/L in Switzerland
(Singer et al., 2002); and from 19 WWTP in Australia the range was
23-434 ng/L with a median concentration of 108 ng/L (Ying and Kookana,
2007).

Triclosan was found in approximately 36 US streams (Kolpin et al., 2002)
where effluent from activated sludge waste water treatment plants,
trickle down filtration, and sewage overflow are thought to contribute
to the occurrence of triclosan in open water. For this study, the U.S.
Geological Survey surveyed a network of 139 streams across 30 states
during 1999 and 2000.  The selection of sampling sites was biased toward
streams susceptible to contamination (i.e. downstream of intense
urbanization and livestock production). The median concentration was 140
ng/L and the maximum concentration detected was 2300 ng/L (Kolpin et
al., 2002). In another study, storm water canal measurements over a 6
month period in Bayou St. John in Louisiana indicated that triclosan
ranged from below the detection level to 29 ng/L (Boyd et al., 2004).
Raw drinking water in Southern California was found to have total mean
concentrations of 56 ng/L triclosan and 49 ng/L triclosan in finished
water and mean concentrations of 734 ng/L of triclosan in raw and
finished drinking water (Loraine and Pettigrove, 2006).   Triclosan was
detected at higher concentrations during dry seasons (August to
November) in the Southern California water systems.  Other published
data on surface water concentrations of triclosan in the US indicated
concentrations of 4 and 8 ng/L in the upper Detroit river (Hua et al.,
2005) and 56 ng/L in Arlington, Virginia (Thomas and Foster, 2004).
Published data on surface water concentrations of triclosan in other
countries indicated concentrations of <3-10 ng/L in Germany (0.3-10 ng/L
methyl-triclosan) (Bester, 2005); 19±1.4 ng/L in England (Sabaliunas et
al., 2003); 11-98 ng/L in Switzerland (Singer et al., 2002); 30 ng/L in
Germany (Wind et al., 2004); and in Australia 75 ng/L (Ying and Kookana,
2007).  Discharge into U.S. surface waters has resulted in other
researchers finding triclosan from the low ng/L levels to a maximum of
2.3 µg/L (U.S. EPA, 2007).

From published literature on the aquatic toxicity of triclosan in
zebrafish, average bioconcentration factors (BCF) for triclosan
following a 5-week accumulation period were 4157 at 3 (g/L and 2532 at
30 (g/L (Orvos et al., 2002).  Following 2 weeks of depuration, average
BCF values decreased to 41 at 3 (g/L and 32 at 30 (g/L.  Depuration rate
constants were 0.142 and 0.141 per day at 3 (g/L and 30 (g/L,
respectively.  The predicted bioconcentration factor for triclosan was
calculated to be ca. 2500.  The lethal body burden was determined to
range from 0.7-3.4 mM/kg, indicating a narcosis mode of action.  These
data indicate that triclosan bioconcentrates in zebra fish, but
depuration occurs rapidly once triclosan exposure is removed. Relative
to bioaccumulation, there are no data presently available to determine
if this occurs.  However, some authors (Balmer, M.E. et. al., 2004;
DeLorenzo et al., 2008; Heidler, J. and Halden, R. U., 2007;
Samsoe-Petersen L. et. al., 2003) suggest that triclosan and methyl
triclosan may bioaccumulate in the environment.

I.	Environmental Fate Assessment

Abiotic

	In the hydrolysis study conducted under abiotic and buffered
conditions, non-radiolabeled 5-chloro-2-(2,4-dichlorophenoxy)phenol
applied at concentrations of 5.2 mg/L (Run 1) and 5.9 mg/L (Run 2), was
stable in heat-sterilized aqueous buffer solutions adjusted to pH 4, pH
7, and pH 9 following incubation in brown glass reaction flasks at 50°C
for 5 days.  After 5 days, triclosan residues in Runs 1 and 2 comprised
5.1-5.4 mg/L and 5.9-6.0 mg/L, respectively, in the pH 4, 7 and 9 buffer
solutions.  The half-lives for triclosan in pH 4, pH 7, and pH 9 buffer
solutions at 50°C were not calculated since the study author determined
that it was hydrolytically stable (<10% degradation).  Furthermore, from
the data at 50°C, the study author concluded that the half-life for
triclosan in pH 4, pH 7, and pH 9 buffer solutions at 25°C was greater
than one year.  This preliminary hydrolysis study has the following
deficiencies: insufficient sampling intervals, no chromatogram data to
confirm the material balance, and generally insufficient details in the
methodology and sampling rational.  Although the preliminary hydrolysis
study still contains few deficiencies as it relates to the OPPTS
Guideline 835.2110, the data are useful and indicate triclosan is
hydrolytically stable at pH 4, 7, and 9 at 50°C, therefore, no
additional hydrolysis data is required.  This hydrolysis study (MRID No.
420279-08) is classified as supplemental and no further hydrolysis
testing is required.

	In a photolysis study conducted under abiotic and buffered conditions,
U-dichlorophenyl-labeled 14C-5-chloro-2-(2,4-dichlorophenoxy)phenol
(triclosan, radiochemical purity > 96%, specific activity 12.7 µCi/mg,
in acetonitrile), at a concentration of 4.42 mg/L, degraded rapidly in
filter-sterilized aqueous pH 7 (phosphate) buffer solutions that were
continuously irradiated under a xenon arc lamp at ca. 25 ± 1C for
240 minutes.  In the irradiated samples, [14C]triclosan declined from
96.6-100.2% of the applied radioactivity at time 0, to 55.2-56.4% at 30
minutes, and was 1.1-1.2% at 240 minutes post-treatment.  In the dark
controls, [14C]triclosan was 98.4% of the applied at time 0 and
94.1-106.1% from 15-240 minutes.  The calculated photolytic half-life
was 41 minutes.  In the irradiated samples, one transformation product
was identified, DCP (2,4-dichlorophenol), which increased from 0.4-1.0%
of the applied radioactivity at time 0, to a maximum of 93.8-96.6% at
240 minutes.  In the dark controls, DCP was observed at a maximum of
1.9% of the applied at 240 minutes.  The photodegradation in water
guideline requirements (OPP 161-2) have been fulfilled by this study
(MRID 430226-08).

	In an aerobic soil metabolism study conducted under abiotic conditions,
[phenoxy-U-14C]-labeled 5-chloro-2-(2,4-dichlorophenoxy)phenol
(triclosan; radiochemical purity 95.8%, specific activity 5.43 MBq/mg),
at a concentration of 0.2 mg/kg, degraded rapidly in sandy loam soil
from Germany, clay loam soil from France, and loam soil from Switzerland
that were maintained in darkness at 20 ( 2(C and a moisture content of
pF 2.0-2.5 for 124 days.  [14C]Triclosan declined from an average
91.9-94.7% of the applied radioactivity at time 0, to 42.3-57.9% at 2-3
days, and was 1.1-4.3% at 61-124 days post-treatment.  [14C]Triclosan
degraded with nonlinear half-lives of 2.9-3.8 days in all soils.  One
major transformation product was identified, methyl-triclosan, which was
a maximum of 13.5-24.0% of the applied 14-28 days post-treatment.  The
aerobic soil biotransformation guideline requirements (OECD 307) have
been fulfilled by this study (MRID 472614-01).

In an aerobic aquatic metabolism study conducted under abiotic
conditions, [phenoxy-U-14C]-labeled
5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan; radiochemical purity
96.0%, specific activity 5.43 MBq/mg), at a concentration of 0.1 mg/L,
degraded rapidly in river water-sandy loam sediment and pond water-silty
clay loam sediment systems from Switzerland maintained under aerobic
conditions in darkness at 20 ( 2(C for 104 days.  In the water layer,
[14C]triclosan declined from an average 88.0-92.9% of the applied
radioactivity at time 0 to 48.9-52.8% at 1 day, and was (0.3% at 56-104
days post-treatment.  In the sediment, [14C]triclosan increased from an
average 39.2-40.3% of the applied radioactivity at time 0 to 69.2-74.9%
at 7-14 days, and was 21.3-21.8% at 104 days post-treatment.  In the
total system, [14C]triclosan decreased steadily from 88.0-92.9% of the
applied at time 0 to 52.1-67.9% at 28 days, and was 21.5-21.8% at 104
days post-treatment.  [14C]Triclosan degraded with nonlinear half-lives
of 1.3-1.4 days (water layer), 53.7-60.3 days (sediment), and 39.8-55.9
days (total system) for both water-sediment systems.  One minor
transformation product was identified, methyl-triclosan, which was a
maximum mean of 0.1% of the applied at 28 days post-treatment in the
water and a maximum mean of 3.4-4.8% at 104 days in the sediment and
total system.  The aerobic aquatic biotransformation guideline
requirements (OPP 162-4) have been fulfilled by this study (MRID
472614-02).

In a soil nitrification study conducted under abiotic conditions,
unlabeled 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan; purity
99.3%) at application rates of 0.125, 0.25, 0.5, 1.0, and 2.0 mg/kg dry
soil was studied in a German sandy loam soil amended with lucerne meal
and adjusted to 45% MWC that was incubated in the dark for 28 days at 20
( 2(C.  Nitrite was detected at a mean initial concentration of
0.606-0.661 mg NO2-/kg dry soil for Treatments I-V.  After 28 days,
nitrite was not detected in any treatment.  Nitrate was detected at a
mean initial concentration of 94.7-102.4 mg NO3-/kg dry soil for
Treatments I-V.  After 28 days, the mean nitrate concentration increased
in Treatments I, III, IV, and V (105.0-110.1 mg/kg) and decreased in
Treatment II (94.6 mg/kg).  This soil nitrification study is considered
supplemental information (MRID 472614-03).

In a soil respiration study conducted under abiotic conditions,
unlabeled 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan; purity
99.3%) at application rates of 0.125, 0.25, 0.5, 1.0, and 2.0 mg/kg dry
soil was studied in a German sandy loam soil adjusted to 45% MWC that
was incubated in the dark for 28 days at 20 ( 2(C.  The mean rate of
respiration at test initiation ranged from 6.12-6.61 mg CO2/h/kg dry
soil for Treatments I-V.  After 28 days, the mean rate of respiration
ranged from 5.85-6.13 mg CO2/h/kg dry soil for Treatments I-V.  This
soil respiration study is considered supplemental information (MRID
472614-04).

In a ready biodegradability study conducted under abiotic conditions,
unlabeled 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan; purity
94.8%) at an application rate of 0.206 mg/L was studied in anaerobic
sludge (pH 7.3-7.4) incubated in the dark at 35 ( 1(C for 147 days.  The
concentration of [14C]triclosan was relatively stable and accounted for
78.0-97.4% throughout the study.  This ready biodegradability study is
considered supplemental information (MRID 472614-06).

In a ready biodegradability study conducted under abiotic conditions,
unlabeled 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan; purity
94.8%) at an application rate of 0.2 mg/L was studied in a microbial
inoculum of sandy loam soil and activated sludge from an industrial
sewage treatment plant maintained in the dark at 22 ( 3(C for 57 days.  
 SEQ CHAPTER \h \r 1 [14C]Triclosan decreased from an average 78.8% of
the applied at day 0 to 25.6% at 7 days, 20% (single detection) at 14
days, and was below detectable limits at 21 days.  [14C]Triclosan
degraded with an average half-life value of 5.2 ( 1.7 days. This ready
biodegradability study is considered supplemental information (MRID
472614-07).

APPENDIX

Environmental Fate Data for Triclosan 

Parameter	Value	Source

Molecular Weight (g/mol)	289.55	EPI Suite

Molecular Formula	C12H7Cl3O2	EPI Suite

Water solubility (mg/L)	12 ppm

2 ppm	MRIDs 420279-04, 472614-01, 472614-02, 472614-03, 472614-04,
472614-06, 472614-07

Vapor Pressure/volatility (mm Hg)	4 x 10-4 Pa 25°C

3 x 10-4 Pa 20°C

4 x 10-6 mm Hg 20°C	MRIDs 420279-04, 472614-03, 472614-04, 472614-06,
472614-07

Henry’s Law Constant (atm-m3/mol)	1.5 x 10-7 at 25°C	EPI Suite/TOXNET

pKa	7.9	TOXNET

Log Kow (octanol-water partition coefficient)	4.76	MRIDs 420279-02 &
420279-04

Koc (organic carbon ratio in soil)	9,200	TOXNET

Mobility	Immobile	TOXNET

BCF	2.7 to 90	TOXNET

Hydrolysis (hrs)

pH 4

pH 7

pH 9

	Stable at 50°C	MRID 420279-08

Aqueous photolysis half-life

	Half-life = 41 min.

Degradate: DCP (2,4-dichlorophenol):  Chemical Formula:  C6H4Cl2O

CAS No.: 120-83-2

	MRID 430226-08

Aerobic soil metabolism	Half-life = 2.9 days, sandy loam soil; 3.8 days,
clay loam soil; 3.7 days, loam soil.

Degradate: methyl triclosan.

	MRID 472614-01

Aerobic aquatic metabolism	Half-life (River water-sandy loam sediment) =
1.3 days, water; 53.7 days, sediment; 39.8 days, total system.

Half-life (Pond water-silty clay loam sediment) = 1.4 days, water; 60.3
days, sediment; 55.9 days, total system.

Degradate: methyl triclosan.	MRID 472614-02

Ready biodegradability	Half-life = 5.2 ( 1.7 days.	MRID 472614-06 &
472614-07



A.	Environmental Fate Guideline Studies

	1.	Hydrolysis (OPP Guideline Number 161-1, MRID No. 420279-08)

	This hydrolysis study was reviewed by the Agency and classified as
supplemental due to the following deficiencies: insufficient sampling
intervals, no chromatogram data to confirm the material balance, and
insufficient details in the methodology and sampling rational.  However,
the data are useful and indicate triclosan is hydrolytically stable at
pH 4, 7, and 9 at 50°C, therefore, no additional testing is required. 
This hydrolysis study (MRID No. 420279-08) is classified as supplemental
and no further hydrolysis testing is required.

	In this study, non-radiolabeled triclosan
[5-chloro-2-(2,4-dichlorophenoxy)phenol, in ethanol, was added to
heat-sterilized pH 4 (acetate), pH 7 (phosphate), and pH 9 (borate)
aqueous buffer solutions at concentrations of 5.2 mg/L (Run 1) and 5.9
mg/L (Run 2).  Each treated buffer solution was incubated in brown glass
reaction flasks at 50°C for 5 days.  Duplicate samples were prepared
for analysis at 0 and 5 days post-treatment.

 

	Study results indicate that triclosan was stable in sterile pH 4, pH 7,
and pH 9 buffer solutions incubated in brown glass reaction flasks at
50°C for 5 days.  At an application rate of 5.2 mg/L, the parent was
present after 5 days incubation at concentrations of 5.4 mg/L, 5.2 mg/L
and 5.1 mg/L in the pH 4, 7, and 9 buffer solutions, respectively.  At
an application rate of 5.9 mg/L, the parent was present after 5 days
incubation at concentrations of 5.9 mg/L, 6.0 mg/L, and 6.0 mg/L in the
pH 4, 7, and 9 buffer solutions, respectively.

	The half-lives for triclosan in pH 4, pH 7, and pH 9 buffer solutions
at 50°C were not calculated since the study author determined that it
was hydrolytically stable(<10% degradation).  Furthermore, from the data
at 50°C, the study author concluded that the half-life for triclosan in
pH 4, pH 7, and pH 9 buffer solutions at 25°C was greater than one
year. 

	2.	Photodegradation in Water (OPP Guideline No. 161-2, MRID No.
430226-08)

	This study was reviewed by the Agency and satisfies the
photodegradation in water data requirements for triclosan.

	In this study, [14C-U- dichlorophenyl]-labeled triclosan
[5-chloro-2-(2,4-dichlorophenoxy)phenol, radiochemical purity > 96%,
specific activity 12.7 µCi/mg], in acetonitrile, was added to
filter-sterilized pH 7 (phosphate) buffer solution at a concentration of
4.42 mg/L.  Aliquots of the treated solutions were transferred to
sterile, silylated quartz test tubes with Teflon-coated rubber stoppers;
tubes were filled completely with the test solution, leaving no
headspace, to prevent volatile losses.  Dark controls were covered with
aluminum foil and maintained inside a temperature-controlled incubator
at 25.0 ± 0.5(C.  The irradiated test samples were placed in a Suntest
photolysis apparatus, and continuously irradiated with a xenon arc lamp
(wavelengths of 200-300 nm) for 240 days.  The mean irradiation
intensity of the xenon lamp was 0.1139 ± 0.0009 W/cm2, which was
similar to a clear sunny summer day in Frederick, Maryland, with a
natural sunlight intensity of 0.096 W/cm2 to 0.115 W/cm2.  The spectral
distribution and intensity of the artificial and natural light sources,
measured over a wavelength range of 200-700 nm, were also similar.  The
temperature in the photolysis chamber was maintained at ca. 25 ± 1(C.

	Duplicate samples of irradiated solutions and single samples of dark
control solutions were analyzed at time 0 and 15, 30, 60, 120, 180, and
240 minutes post-treatment.  At each sampling interval, aliquots of
irradiated and dark control solutions were analyzed for total
radioactivity by liquid scintillation counting (LSC; limit of detection
was 0.023 ppm).  Additional aliquots of each test solution were analyzed
by HPLC using a Zorbax ODS column (250 x 4.6 mm) and the isocratic
solvent elution of methanol:water (75:25, v:v).  Radioactive areas were
identified by radioscanning; non-radioactive areas were identified by UV
(235 nm).  Quantification of the parent and its transformation products
was performed by LSC analysis of the solutions of the isolated
compounds.  Confirmation of the identity of the parent and its
transformation products was performed by a second HPLC analysis using
the same conditions as described previously, except that the solvent
system was methanol:water:acetic acid (800:200:1, v:v:v).  The volatile
[14C]residues from the irradiated and dark control samples were not
measured.

	In the irradiated samples, [14C] triclosan decreased from 96.6-100.2%
of the applied radioactivity at time 0, to 55.2-56.4% at 30 minutes,
39.4-39.6% at 60 minutes, 12.7-15.7% at 120 minutes, and was 1.1-1.2% at
240 minutes post-treatment.  In the dark controls, [14C] triclosan was
98.4% of the applied radioactivity at time 0 and 94.1-106.1% from 15-240
minutes.  Based on first-order linear regression analysis, the
calculated photolytic half-life was 41 minutes, with a rate constant (k)
of 1.68 x 10-2/min.

	In the irradiated samples, one transformation product was identified,
DCP (2,4-dichlorophenol), which increased from 0.4-1.0% of the applied
radioactivity at time 0, to a maximum of 93.8-96.6% at 240 minutes.  In
the dark controls, DCP was observed at a maximum of 1.9% of the applied
radioactivity at 240 minutes.  Two minor unidentified transformation
products were also detected.  In the irradiated and dark controls,
Unknown 1 was a maximum of 7.8% and 1.1%, respectively, and Unknown 2
was a maximum of 5.3% and 1.3%, respectively.

	In the irradiated and dark controls, the material balance was 104.8 ±
3.8% (range, 98.2-111.0%) and 103.6 ± 4.2% (range, 95.7-107.2%) of the
applied radioactivity, respectively.  Volatilized [14C] residues were
not measured.

	3.	Aerobic Soil Metabolism (OECD Guideline 307, MRID No. 472614-01)

	This study was reviewed by the Agency and satisfies the aerobic soil
metabolism data requirements for triclosan.

	In this study, [phenoxy-U-14C]-labeled triclosan
[5-chloro-2-(2,4-dichlorophenoxy)phenol, radiochemical purity 95.8%,
specific activity 5.43 MBq/mg], was added to aliquots of a sandy loam
soil (Speyer 5M, pH 7.1, organic matter 2.4%) from Germany, a clay loam
soil (Senozan, pH 6.85, organic matter 1.79%) from France, and a loam
soil (Gartenacker, pH 7.3, organic matter 2.98%) from Switzerland at a
concentration of 0.2 mg/kg.  The glass metabolism flasks were incubated
for 124 days under aerobic conditions in darkness at 20 ( 2(C and a
moisture content of pF 2.0-2.5.  The flasks were attached to a
flow-through volatile trapping system and moistened air was continuously
drawn through each flask, then through sodium hydroxide and ethylene
glycol traps.

Duplicate samples of each soil were collected at 0, 1, 2, 3, 7, 14, 28,
61, and 124 days posttreatment.  The soils were extracted up to four
times with acetonitrile:water (4:1, v:v), followed by a Soxhlet
extraction with acetonitrile:water (4:1, v:v).  After each extraction,
the supernatants were analyzed for total radioactivity by LSC (limit of
detection was 0.06% of the applied).  The extracts were then combined,
concentrated, re-dissolved in an acetonitrile:water mixture, and
analyzed using LSC.  Day 124 extracts were submitted to a harsh
extraction using acetonitrile:0.1M hydrochloric acid (1:1, v:v) under
reflux conditions and analyzed using LSC.  [14C]Residues in the extracts
were separated and quantified by HPLC using a Kromasil 100-C18 column
(250 x 4.6 mm) and a gradient mobile phase combining (A) 0.1% phosphoric
acid and (B) acetonitrile with UV (224 nm) and radioactive flow
detection.  Quantification of the parent and its transformation products
was performed by LSC analysis of the solutions of the isolated compounds
(limit of detection 0.2% of the applied).  Confirmation of the identity
of the parent and its transformation products was performed by
comparison to unlabeled reference standards.  Identifications were
confirmed by normal phase two-dimensional TLC analysis on pre-coated
silica gel plates (60F254; 0.25 mm thickness; 20 x 20 cm) developed in
ethyl acetate:hexane (50:50, v:v; SS 1; 1st dimension),
chloroform:methanol:water:acetic acid (75:25:2:2, v:v:v:v; SS 2; 2nd
dimension), chloroform:methanol:water:acetic acid (70:30:2:2, v:v:v:v;
SS 3; 2nd dimension), and ethyl acetate:hexane (40:60, v:v; SS 4; 2nd
dimension).  Residues were visualized using UV (254 nm) light with
fluorescence quenching and phosphor imaging using a Fuji BAS 1500
imager.  The sodium hydroxide and ethylene glycol trapping solutions
were analyzed using LSC (limit of detection 0.06% of the applied).  The
presence of carbon dioxide was confirmed by precipitating with barium
hydroxide.  The extracted soil was analyzed using LSC following
combustion (limit of detection 0.62% of the applied).  

In the sandy loam soil, [14C]triclosan decreased from an average 94.7%
of the applied radioactivity at day 0 to 57.9% at 2 days, 23.1% at 7
days, 12.3% at 14 days, and was 4.3% at 124 days.  Based on linear and
nonlinear regression analyses, [14C]triclosan degraded with half-lives
of 30.1 and 2.9 days, respectively.  The observed DT50 value was ca. 2.5
days.

In the clay loam soil, [14C]triclosan decreased from an average 94.3% of
the applied radioactivity at day 0 to 47.3% at 3 days, 27.3% at 7 days,
12.8% at 14 days, 3.2% at 61 days, and was not detected at 124 days. 
Based on linear and nonlinear regression analyses, [14C]triclosan
degraded with half-lives of 12.5 and 3.8 days, respectively.  The
observed DT50 value was ca. 3 days.

In the loam soil, [14C]triclosan decreased from an average 91.9% of the
applied radioactivity at day 0 to 42.3% at 3 days, 12.5% at 14 days,
7.6% at 28 days, and was 1.1% at 124 days.  Based on linear and
nonlinear regression analyses, [14C]triclosan degraded with half-lives
of 20.8 and 3.7 days, respectively.  The observed DT50 value was ca. 2
days.

One major transformation product was detected and identified. 
Methyl-triclosan (M3) was detected at maximum means of 17.5% and 24.0%
of the applied radioactivity in the sandy loam and clay loam soils,
respectively, at 28 days and at a maximum of 13.5% of the applied
radioactivity in the loam soil at 14 days.  One unknown (M1) accounted
for a maximum average of 4.1%, 3.4%, and 3.5% of the applied
radioactivity in sandy loam, clay loam, and loam soils, respectively, at
0 days.

Overall recoveries averaged 97.6 ( 3% (range 90.4-101.3%) in the sandy
loam soil, 97.5 ( 3% (92.0-100.8%) in the clay loam soil, and 97.5 ( 3%
(91.7-100.9%) in the loam soil.  Extractable [14C]residues decreased
from means of 95.4-98.8% of the applied radioactivity at day 0 to
12.5-17.3% at 124 days, while nonextractable [14C]residues increased to
maximum means of 60.8-75.8% at study termination.  Acidic harsh
extraction of select 124 day samples released an average 2.4-2.7% of the
applied radioactivity.  At 124 days posttreatment, volatilized 14CO2
accounted for 11.5-16.3% of the applied radioactivity and organic
volatiles were <0.7%.

In a supplementary experiment, sandy loam soil was treated with
[14C]triclosan at 0.2 mg/kg and maintained at 10 ( 2(C.  Duplicate
samples were removed for analysis at 0, 3, 7, 14, 28, 61, and 124 days
posttreatment and analyzed as previously described.  Overall recoveries
averaged 97.3 ( 2.5% (range 91.8-100.6%).  [14C]Triclosan decreased from
an average 93.5% of the applied radioactivity at day 0 to 17.5% at 124
days.  Major transformation product methyl-triclosan reached a maximum
average of 14.5% of the applied radioactivity at 61 days.  Two unknowns
M1 and M2 accounted for maximum averages of 3.8% and 1.2% (single
replicate), respectively, at 0 days.  Total extractable [14C]residues
decreased from an average 97.9% of the applied radioactivity at day 0 to
30.8% at 124 days, while nonextractable [14C]residues increased to a
maximum average of 59.7% at 124 days.  At study termination, an average
5.1% of the applied radioactivity was present as 14CO2 and volatile
organics were (0.1% of the applied radioactivity.  Based on first-order
linear regression analyses and nonlinear regression analyses,
[14C]triclosan degraded with half-lives of 54.2 and 18.2 days,
respectively.  The observed DT50 value was ca. 7-14 days.

In a second supplementary experiment, aliquots of each soil were treated
with [14C]triclosan at 2.0 mg/kg.  Following treatment, the samples were
incubated as previously described and samples were removed after 23 days
of incubation and immediately stored frozen.

	4.	Aerobic Aquatic Metabolism (OPP Guideline No. 162-4 and OECD
Guideline 308, MRID 472614-02)

	This study was reviewed by the Agency and satisfies the aerobic aquatic
metabolism data requirements for triclosan.

In this study, [phenoxy-U-14C]-labeled
5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan; radiochemical purity
96.0%; specific activity 5.43 MBq/mg) was applied to river water-sandy
loam sediment (water pH 7.3, total organic carbon 2.97 mg C/L; sediment
pH 7.29, organic carbon 0.78%) and pond water-silty clay loam sediment
(water pH 7.2, total organic carbon 6.43 mg C/L; sediment pH 7.26,
organic carbon 5.0%) systems from Switzerland for 104 days under aerobic
conditions in darkness at 20 ( 2(C.  [14C]Triclosan was applied at a
rate of 0.1 mg/L.  The sediment:water ratio was ca. 1:3.3 (ca. 2.0 cm
sediment: ca. 6.5 cm water).  The test apparatus consisted of glass
metabolism flasks (ca. 10.6-cm diameter) connected to a continuous
flow-through (moistened air, 30-50 mL/minute) system with 2N NaOH and
ethylene glycol traps.  The sediment and water were acclimated for ca. 2
weeks prior to treatment.

Duplicate vessels per system type were collected after 0, 1, 7, 14, 28,
56, and 104 days of incubation.  The water layers were drawn off via
pipette and concentrated using solid phase extraction (0, 1, and 7 days)
or rotary evaporation (days 56 and 104) or partitioned with ethyl
acetate and acidified with concentrated hydrochloric acid (days 14 and
28).  The concentrated aqueous extracts were subjected to HPLC analysis
using a Kromasil C18 column (250 x 4.6 mm) and three different gradient
mobile phase methods (Methods 2-4) with UV (224 nm) and radioactive flow
detection.  HPLC Method 2 combined (A) 0.1% TFA in water and (B) 0.1%
TFA in acetonitrile and Methods 3-4 combined (A) 0.1% phosphoric acid in
water and (B) acetonitrile.  Confirmation of the identity of the parent
and its transformation products was performed by comparison to unlabeled
reference standards.  Identifications were confirmed by normal phase
two-dimensional TLC analysis on pre-coated silica gel plates (60F254;
0.25 mm thickness; 20 x 20 cm) developed in ethyl acetate:hexane (50:50,
v:v; SS 1) and chloroform:methanol:water:acetic acid (75:25:2:2,
v:v:v:v; SS 2).  Residues were visualized using UV (240 nm) light and
phosphor imaging using a Fuji BAS 1000 imager.  Sediment samples were
extracted up to 3 times with acetonitrile:water (4:1, v:v).  Sediments
from day 1 onwards were additionally submitted to a Soxhlet extraction
using acetonitrile.  The resulting extracts were combined and
concentrated via reduced pressure.  Day 104 extracts were submitted to
an additional harsh extraction using acetonitrile:0.1M hydrochloric acid
(1:1, v:v) under reflux conditions.  Water layers, sediment extracts,
extracted sediment, and trapping solutions were analyzed for total
radioactivity using LSC (limits of detection were 0.11% of the applied
for the water phase, 0.02% for the extractables, 0.04% for the
non-extractables, and <0.01% for volatiles).  The presence of carbon
dioxide was confirmed by precipitating with barium hydroxide.  Water
layer and sediment extract samples were analyzed for the parent and its
transformation products via HPLC and 2-D TLC as previously described.

In the water layers, triclosan decreased from means of 92.9% and 88.0%
in the sandy loam and silty clay loam systems, respectively, at time 0
to 52.8% and 48.9% at 1 day, 11.4% and 12.0% at 7 days, 3.9% and 6.5% at
14 days, and was (0.3% at 56-104 days.  Observed DT50 values for
triclosan in the water layers were ca. 1 day for the sandy loam and
silty clay loam systems with calculated linear half-lives of 11.9 and
7.2 days, respectively, and nonlinear half-lives of 1.3-1.4 days for
both systems.

In the sediments, triclosan increased from means of 39.2% and 40.3% in
the sandy loam and silty clay loam systems, respectively, at time 0 to
69.2% and 74.9% at 7-14 days, then decreased to 51.6% and 65.1% at 28
days, and was 21.3% and 21.8% at 104 days.  In the sediment for the
sandy loam and silty clay loam systems, calculated linear half-lives
were 56.4 and 53.7 days, respectively, and nonlinear half-lives were
53.7 and 60.3 days.

In the total system, [14C]triclosan decreased steadily in the sandy loam
and silty clay loam systems from 92.9% and 88.0%, respectively, at time
0, to 52.1% and 67.9% at 28 days, and was 21.5% and 21.8% at 104 days. 
Observed DT50 values for triclosan in the total sandy loam and silty
clay loam systems were ca. 28 days and 56 days, respectively, with
linear half-lives of 47.8 and 51.0 days, and nonlinear half-lives of
39.8 and 55.9 days.

		No major nonvolatile transformation products were detected and only
one minor product was identified.  Methyltriclosan was detected at a
maximum mean of 0.1% of the applied radioactivity in the water at 28
days (sandy loam sediment only) and at a maximum of 4.8% and 3.4% of the
applied in the sandy loam and silty clay systems, respectively, for both
the sediment and total system at 104 days.  Unidentified [14C]residues
were total maximum means of 5.1%, 9.9% and 11.0% of the applied in the
water, sediment and total system, respectively, for the sandy loam
systems, and 7.3%, 3.8% and 9.7%, respectively, for the silty clay loam
systems.

		Overall recoveries averaged 94.1 ( 2.6% and 95.4 ( 1.4% of applied for
the sandy loam and silty clay loam sediment systems, respectively. 
Extractable sandy loam [14C]residues increased from a mean <0.1% at time
0 to 75.1-78.7% at 7-14 days and were 27.7-34.8% at 104 days. 
Nonextractable [14C]residues were maximum means of 32.4-33.0% at study
termination.  Volatilized 14CO2 was a maximum mean of 21.4-29.2% at
study termination.  Volatile [14C]organic compounds were a maximum of
0.6% at 104 days for both systems.

	5.	Soil Nitrification Study (OECD Guideline 216, MRID No. 472614-03)

		This soil nitrification study was reviewed by the Agency and
classified as supplemental due to various study deficiencies such as: 
it could not be determined if the European soil used in this study was
comparable to soils found in a typical triclosan use area in the United
States; volatiles were not collected; extractable, nonextractable and
total residues were not determined; material balances was not reported;
the pass level was not reported; the half-life were not determined; the
test material was not radiolabeled; some physico-chemical properties
were not reported; soil collection, sampling depth and storage
conditions were not reported; indications of adsorption of the test
material to the walls of the test apparatus were not reported; microbial
soil biomass was not determined; maintenance of the test conditions in
the soil were not verified;  samples were not analyzed for triclosan and
the transformation of the test material was not determined; dissolved
organic carbon was not determined.  Although the soil nitrification
study contains deficiencies, the data are useful and no additional
testing is required.

	In this study, the effect of unlabeled
5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan; purity 99.3%) on soil
nitrification was studied in a sandy loam soil (Speyer 2.3; pH 7.4;
organic carbon 1.02 ( 0.15%) from Germany.  The test system consisted of
incubation flasks (1 L) containing moistened soil that were treated with
triclosan at application rates of 0.125, 0.25, 0.5, 1.0, and 2.0 mg/kg
dry soil.  Following application, the soils were thoroughly mixed,
amended with lucerne meal (ca. 3% nitrogen), and adjusted to 45% MWC by
adding purified water.  The flasks were stoppered with cotton wool plugs
and incubated in the dark for 28 days at 20 ( 2(C.  Control samples were
also prepared and incubated as described.

Triplicate samples were collected at 0 (<3 hours) and 28 days
posttreatment and extracted twice with 2M KCl.  Following each
extraction, the samples were centrifuged and the supernatants were
decanted, filtered, combined, and adjusted with 2M KCl.  The
concentration of nitrite (NO2-) was measured colormetrically at a
wavelength of 550 nm (limit of quantification was 0.09 mg nitrite/kg dry
soil).  The concentration of nitrate (NO3-) was measured by reducing to
nitrite in a cadmium reductor, then measuring colormetrically (limit of
quantification was 0.55 mg nitrate/kg dry soil).

For CO2 evolution measurements, untreated sandy loam soil was sieved,
adjusted to 45% MWC, and subsamples were mixed with varying
concentrations of glucose and talc.  The soils were packed into glass
columns, connected to volatile trapping systems for water and CO2 at the
inlet and to an infrared (IR) gas analyzer at the outlet, and maintained
at 20 ( 2(C for ca. 24 hours.  After an accumulation time, a single
column was flushed with CO2-free air and the CO2 concentration was
measured.  After a 7-second waiting period, the next column was flushed
and measured.

Following amendment with lucerne meal, the mean initial concentrations
of nitrite ranged from 0.606-0.661 mg NO2-/kg dry soil for Treatments
I-V.  After 28 days, nitrite was not detected in any treatment.  The
mean initial concentrations of nitrate were 98.5 mg NO3-/kg dry soil for
Treatment I, 102.4 mg/kg for Treatment II, 94.7 mg/kg dry soil for
Treatment III, 95.4 mg/kg dry soil for Treatment IV, and 96.6 mg/kg dry
soil for Treatment V.  After 28 days, the mean nitrate concentration
increased in Treatments I (105.4 mg/kg), III (105.0 mg/kg), IV (110.1
mg/kg), and V (107.4 mg/kg) and decreased in Treatment II (94.6 mg/kg). 
The calculated deviations to control were -9.3%, -18.6%, -9.7%, -5.4%,
and -7.6% for Treatments I, II, III, IV, and V, respectively.

For control samples, concentrations of nitrite and nitrate were <0.08
mg/kg dry soil and 95.4 mg/kg dry soil, respectively, at day 0 in
untreated and unamended soil.  Following amendment with lucerne meal,
mean concentrations of nitrite and nitrate were 0.645 mg NO2-/kg dry
soil and 99.8 mg NO3-/kg dry soil, respectively.  After 28 days, mean
concentrations of nitrite and nitrate were <0.086 mg NO2-/kg dry soil
and 116.3 mg NO3-/kg dry soil, respectively.

For untreated sandy loam soil, the maximum rate of initial CO2 evolution
from 100 g dry soil equivalents was 0.326 mL/hour.  The microbial
biomass was calculated to be 134.2 mg microbial carbon/kg dry weight
soil.

In a supplementary experiment, sandy loam soil samples, amended with
lucerne meal and adjusted to 45% MWC, were treated with
2-chloro-6-trichloromethylpyridine (Nitrapyrin Pestanal(; purity 97.5%),
dissolved in acetone, at a concentration of 5 mg a.i./kg dry soil.   
SEQ CHAPTER \h \r 1 The mean initial concentrations of nitrite and
nitrate were 0.450 mg NO2-/kg dry soil and 95.8 mg NO3-/kg dry soil,
respectively.  After 28 days, mean nitrite and nitrate concentrations
were <0.086 mg NO2-/kg dry soil and 20.4 mg NO3-/kg dry soil,
respectively, resulting in a deviation of -82.4% to control for nitrate.
 Based on these results, it was determined that nitrapyrin showed a
strong inhibiting effect.

	6.	Soil Respiration Study (OECD Guideline 217, MRID No. 472614-04)

This soil respiration study was reviewed by the Agency and classified as
supplemental due to various study deficiencies such as:  it could not be
determined if the European soil used in this study was comparable to
soils found in a typical triclosan use area in the United States;
volatiles were not collected; extractable, nonextractable and total
residues were not determined; material balances was not reported; the
pass level was not reported; the half-life were not determined; the
radiochemical purity was not reported; soil collection, sampling depth
and storage conditions were not reported; indications of adsorption of
the test material to the walls of the test apparatus were not reported;
microbial soil biomass was not determined; maintenance of the test
conditions in the soil were not verified; samples were not analyzed for
triclosan and the transformation of the test material was not
determined; dissolved organic carbon was not determined; detection
limits were not reported; dinosebacetate caused a clear inhibitory
effect on soil microbial respiration.  Although the soil respiration
study contains deficiencies, the data are useful and no additional
testing is required.

	In this study, the effect of 5-chloro-2-(2,4-dichlorophenoxy)phenol
(triclosan; purity 99.3%) on soil respiration was studied in a sandy
loam soil (Speyer 2.3; pH 7.4; organic carbon 1.02 ( 0.15%) from
Germany.  The test system consisted of incubation flasks (1 L)
containing moistened soil that were treated with triclosan at
application rates of 0.125, 0.25, 0.5, 1.0, and 2.0 mg/kg dry soil. 
Following application, the soils were thoroughly mixed and adjusted to
45% MWC by adding purified water.  The flasks were stoppered with cotton
wool plugs and incubated in the dark for 28 days at 20 ( 2(C.  Control
samples were also prepared and incubated as described.  Triplicate
samples were collected at 0 (<3 hours) and 28 days posttreatment.

For CO2 evolution measurements, untreated sandy loam soil was sieved,
adjusted to 45% MWC, and subsamples were mixed with varying
concentrations of glucose and talc.  The soils were packed into glass
columns, connected to volatile trapping systems for water and CO2 at the
inlet and to an infrared (IR) gas analyzer at the outlet, and maintained
at 20 ( 2(C for ca. 18 hours.  After an accumulation time, a single
column was flushed with CO2-free air and the CO2 concentration was
measured.  After a 7-second waiting period, the next column was flushed
and measured.

The mean rate of respiration at test initiation ranged from 6.12-6.61 mg
CO2/h/kg dry soil for Treatments I-V.  The calculated deviations to
control were -4.9%, -6.8%, -7.0%, -10.3%, and -12.0% for Treatments I,
II, III, IV, and V, respectively.  After 28 days, the mean rate of
respiration ranged from 5.87-6.13 mg CO2/h/kg dry soil for Treatments
I-V.  The calculated deviations to control were -9.4%, -11.3%, -12.0%,
-13.5%, and -13.2% for Treatments I, II, III, IV, and V, respectively. 
Based on these results, it was determined that triclosan did not have a
detrimental influence (i.e. ( ( 25%) on soil microbial respiration when
applied to sandy loam soil up to a concentration of 2.0 mg/kg dry soil.

For control samples,   SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1   SEQ
CHAPTER \h \r 1 the mean rate of respiration was 6.95 mg CO2/h/kg dry at
test initiation and 6.77 mg CO2/h/kg dry soil after 28 days.

For untreated sandy loam soil, the maximum rate of initial CO2 evolution
from 100 g dry soil equivalents was 0.326 mL/hour.  The microbial
biomass was calculated to be 134.2 mg microbial carbon/kg dry weight
soil.

In a supplementary experiment, sandy loam soil samples, adjusted to 45%
MWC, were treated with 2-sec-butyl-4,6-dinitrophenyl acetate
(Dinosebacetate Pestanal(; purity 95.6%), dissolved in acetone, at a
concentration of 3.76 mg a.i./1.5 g quartz sand.  The mean rate of
respiration at test initiation was 3.88 mg CO2/h/kg dry soil.  After 28
days, the mean rate of respiration was 2.02 mg CO2/h/kg dry soil.  The
calculated deviations to control were -44.3% at 0 days and -70.2% at 28
days.  Based on these results, it was concluded that dinosebacetate
caused a clear inhibitory effect on soil microbial respiration.

	7.	Ready Biodegradability

		a. (OECD Guideline 311, MRID No. 472614-06)

	This ready biodegradability study was reviewed by the Agency and
classified as supplemental due to the following deviation: the study
author reported that the volume of gas released from the test vessels
was far greater than was theorized and suggested an extraneous source of
carbon may have been present in the test vessels.  Also, the gas
produced by the reference material, ethanol, was far greater than
theorized and the study author suggested that the microbes in the sludge
may have been stimulated by the presence of ethanol, or by the
metabolism of residual organic carbon from organic solvents routinely
used to clean glassware.  Although this study contains deficiencies as
it relates to the OECD Guideline 311, the data are useful.

In this study, the ready biodegradability of
5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan; purity 94.8%;
specific activity 15 (Ci/mg) was studied in anaerobic sludge (pH
7.3-7.4) collected from a wastewater treatment plant in Massachusetts. 
The test system consisted of thirty-six Wheaton serum bottles fortified
with [14C]triclosan secondary stock solution at an application rate of
0.206 mg/L that were placed into a glove box and purged with 70:30
N2:CO2.  The bottles were then treated with the inoculated medium,
sealed with parafilm, placed on their sides, and incubated in the dark
at 35 ( 1(C.  Reference material samples (95.8 mg/L ethanol) and control
samples were also prepared and incubated as described.

Triplicate samples were collected at 0, 7, 14, 21, 28, 42, 56, 70, 91,
119, and 147 days posttreatment.  The samples were extracted with ethyl
acetate, then dried, concentrated, and adjusted to volume with
acetonitrile:reagent grade water (80:20, v:v).  The concentrated aqueous
extracts were subjected to HPLC analysis using a Metachem Nucleosil C18
column (250 x 4.6 mm) mobile phase of acetonitrile:reagent grade water
(80:20, v:v) with radioactive flow detection.  Confirmation of the
identity of the parent was performed by comparison to an unlabeled
reference standard.  Gas production measurements were conducted in all
test systems using stainless steel needles attached to gas-tight
syringes.

The concentration of [14C]triclosan was relatively stable and accounted
for 78.0-97.4% of the applied radioactivity throughout the study.  HPLC
chromatograms showed 2 unidentified peaks, a “shoulder” peak (ca.
5.5 minutes) and a less polar peak (ca. 11.3 minutes), that were present
in most test and control samples.  It was determined that these peaks
represented matrix artifacts.  CO2 evolution for [14C]triclosan was not
determined and an anaerobic half-life was not determined.  The volume of
the gas released from the [14C]triclosan treated test vessels was far
greater than the volume of gas which could theoretically be produced
and, therefore, was not reported.  These results indicated that an
extraneous source of carbon was present.

  SEQ CHAPTER \h \r 1 Material balances steadily decreased from an
average of 90.2 ( 2.5% of the applied radioactivity at 0 days to 46.5 (
15.8% at 147 days.  Extractable [14C]residues decreased from an average
81.1 ( 3.8% at time 0 to 43.9 ( 16.4% of the applied radioactivity at
147 days.

The cumulative corrected volume of gas produced by the reference
material ethanol was, in all but one replicate, far greater than the
theoretical volume of gas which could have been produced by
mineralization of the ethanol alone, ranging from 69.2-314%.
Explanations for this phenomenon may be the stimulation of the microbes
in the sludge due to the presence of ethanol or the metabolism of
residual organic carbon present in varying amounts since organic
solvents are routinely used in glassware cleaning.

  SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1 For
the control samples, the concentration of [14C]triclosan was relatively
stable and accounted for 85.1-100% of the applied radioactivity
throughout the study.  Extractable [14C]residues accounted for 81.3-112%
of the applied radioactivity.

A microbial density of 3.0 x 106 cfu/mL was estimated for the anaerobic
sludge used to inoculate the test medium.  Based on these results, it
can be assumed that the population density of the sludge upon addition
to the nutrient test solution was 3.0 x 105 cfu/mL.  The anaerobic
microbial density ranged from 1.0-1.3 x 104 cfu/mL in the [14C]triclosan
treated test vessels at 63 days posttreatment.  Day 70 blank control
vessels produced 8.0 x 103 cfu/mL.

		b. (OECD Guideline 301B, MRID No. 472614-07)

	This ready biodegradability study was reviewed by the Agency and
classified as supplemental due to the following deviation: the microbial
inoculum used in the study was pre-adapted to the test substances during
a 13-day acclimation period.  Although this study contains deficiencies
as it relates to the OECD Guideline 301B, the data are useful.

	In this study, the ready biodegradability of
5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan; purity 94.8%;
specific activity 15 (Ci/mg) was studied in a microbial inoculum
comprised of sandy loam soil [pH 7.5, organic carbon 3.4%] from
Wisconsin and activated sludge from an industrial sewage treatment plant
located in San Juan, Puerto Rico.  Duplicate test and control samples of
the microbial inoculum, combined with sterile mineral salts solution,
were fortified with either [14C]triclosan or nonradiolabeled glucose
solution.  Following a 13-day acclimation period in darkness under
aerobic conditions at 22 ( 3(C, the contents of the flasks were
combined.  Triplicate glass bottles were treated with either
[14C]triclosan at an application rate of 0.2 mg a.i./L or [14C]glucose
solution at an application rate of 25.0 mg a.i./L.  The glass bottles
were connected to a flow-through volatile trapping system and placed
into an environmental chamber maintained in the dark at 22 ( 3(C. 
Moistened, CO2-free air (50-100 mL/min. flow rate) was passed through
duplicate Instagel( and phenethylamine traps.

Triplicate samples were collected from the volatile and carbon dioxide
traps at 0-10, 12, 14, 17, 20, 25, 28, 31, 34, 37, 41, 47, 54, and 57
days posttreatment and analyzed for total radioactivity by LSC.  The
volume of the remaining solution was recorded, then filtered to remove
biomass.  Each test vessel was rinsed with ethanol and the rinsate was
analyzed by LSC.  Biomass-laden filters were analyzed by LSC following
combustion.  Samples were removed from each [14C]triclosan system bottle
and each control bottle at 0, 7, 14, and 21 days and analyzed by HPLC
using a Metachem Nucleosil C18 column (250 x 4.6 mm) mobile phase of
methanol:reagent grade water (80:20, v:v) with radioactive flow
detection (limit of detection was 0.016 mg/L).  Confirmation of the
identity of the parent was performed by comparison to an unlabeled
reference standard.

  SEQ CHAPTER \h \r 1 For the [14C]triclosan systems, the concentration
of [14C]triclosan decreased from an average 78.8% of the applied
radioactivity at day 0 to 25.6% at 7 days, 20% (single detection) at 14
days, and was below detectable limits at 21 days.  At 57 days
posttreatment, the mean cumulative 14CO2 evolved was 57.1% of the
applied radioactivity and the mean cumulative [14C]volatile organic
products evolved was 10.2% of the applied radioactivity.  Based on HPLC
data, the study author determined that [14C]triclosan degraded with an
average half-life value of 5.2 ( 1.7 days.  The average half-life for
mineralization of triclosan to CO2 was 61 ( 55 days.

For the [14C]glucose systems, at 57 days posttreatment, the mean
cumulative 14CO2 evolved was 81.6% of the applied radioactivity.  The
mean cumulative [14C]volatile organic products evolved was 0.1% of the
applied.

Overall recoveries of [14C]residues averaged 92.1 ( 6.1% (range
85.2-96.6%) and 94.9 ( 2.6% (range 93.3-97.9%) of the applied
radioactivity for the [14C]triclosan and [14C]glucose systems,
respectively.    SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1   SEQ CHAPTER
\h \r 1 Percent recovery was (89% at all sampling intervals for the
control samples.

	The aerobic microbial density ranged from 8.5 x 106 to 1.2 x 107 cfu/mL
in the sludge and from 1.4 x 105 to 4.2 x 106 cfu/mL in the test vessels
at 57 days posttreatment.  Based on these results, it was determined
that a viable aerobic community was present in the test vessels and that
triclosan and its transformation products do not substantially inhibit
aerobic microbial activity.

B.	Summary of Published Literature on Triclosan As Related To
Publicly-Owned Treatment Works (POTW) Concerns

  SEQ CHAPTER \h \r 1 From published literature on the occurrence of
triclosan in waste water treatment plants, treatment plant efficiency,
and open water measurements of triclosan, ccontamination of water can
come directly from   SEQ CHAPTER \h \r 1 public water systems. Triclosan
is ubiquitous in detergents, soaps, and personal care products, which
contribute to the presence of triclosan in water. Published literature
on the occurrence of triclosan in wastewater treatment plants (WWTP),
sewage treatment plants, or wastewater samples for the United States
(Anderson et al., 2004; Boyd et al., 2003 and 2004; Loraine and
Pettigrove, 2006; McAvoy, et al., 2002; Thomas and Foster, 2004 and
2005; Waltman et al., 2006), Canada (Boyd et al., 2003; Hua et al.,
2005), Australia (Ying and Kookana 2007), Japan (Nakada et al., 2006;
Shirashi et al., 1985), Switzerland (Lindstrom et al., 2002; Singer et
al., 2002), and many European countries (Paxeus, 2004) such as England
(Kanda et al., 2003; Sabaliunas et al., 2003; Thompson et al., 2005),
Spain (Agüera et al 2003; Mezcua et al., 2004), Sweden (Bendz et al.,
2005), Greece (Gatidou et al., 2007; Gomez et al., 2007) and Germany
(Bester, 2003 and 2005; Wind et al., 2004) illustrate that triclosan is
removed from wastewater but not completely. The majority of these
studies suggest that aerobic biodegradation is one of the major and most
efficient biodegradation pathways (70-80%) through which triclosan and
its by-products are removed from the aquatic environment.  Another
pathway of removing triclosan from water in wastewater treatment plants
is through the sorption of triclosan and associated by-products to
particles and sludge (10-15%) because of the chemical’s medium to high
hydrophobicity (Agüera et al., 2003; Gomez et al., 2007; Kanda et al.,
2003; Lee and Peart, 2002; Bester, 2003 and 2005; Xia et al., 2005). 
The studies indicated that total removal rates of triclosan from
activated sludge wastewater treatment plants varied from as low as 53%
(Kanda et al., 2003) to as high as 99% (Kanda et al., 2003). Removal
rates for another removal pathway, trickle down filtration, range from
58-86% (McAvoy et al., 2002) and are less effective overall in removing
triclosan than the other pathways previously mentioned. Benchtop fate
testing of triclosan found that 1.5-4.5% was sorbed to activated sludge
and 81-92% was biodegraded (Federle et al., 2002).

Activated sludge and/or sludge samples examined for triclosan residue in
Ohio showed a range of 0.5 to 15.6 μg/g (dry weight) and there was
higher concentrations of triclosan observed in anaerobic sludge as
compared to aerobic sludge (McAvoy et al., 2002).  Other countries
analyzed sludge samples for triclosan with the following findings:
Canada (370 ng/g, Lee and Peart, 2002); Germany (1000-8000 ng/g, Bester,
2003 and 2005); Greece (1840 ng/g, Gatidou et al, 2007); Spain (420-5400
ng/g, Morales et al, 2005); Australia (19 WWTP had range of 90-16,790
ng/g dry weight with median of 2320, Ying and Kookana, 2007).

Effluent concentrations from wastewater treatment plants in the US were
10-21 ng/L in Louisiana (Boyd et al., 2003); 63 ng/L in the upper
Detroit river (Hua et al., 2005); 72 ng/L in Arlington, Virginia (Thomas
and Foster, 2004); 110 ng/L in North Texas (Waltman et al., 2006); and
the highest was 200-2700 ng/L in Ohio (McAvoy et al., 2002). Effluent
concentrations from wastewater treatment plants in other countries were
measured to be 160 ng/L (Lee et al., 2003) or 50-360 ng/L in Canada (Lee
et al., 2005); 50 ng/L (Bester, 2003), 10-600 ng/L (Bester, 2005), or
180 ng/L (Wind et al., 2004) in Germany; 160 ng/L in Sweden (Bendz et
al., 2005); 430 ng/L (31.2 μg/g particulate matter), 1120 ng/L (16.1
μg/g particulate matter), or 230 ng/L (22.4 μg/g particulate matter)
in three different WWTP in Greece (Gatidou et al. 2007); 80-400 ng/L in
Spain (Gomez et al., 2007); 100-269,000 ng/L in Spain (Mezcua et al.,
2004); 0.15±0.08 mg/person in 5 European countries (Paxeus, 2004); 340
or 1100 ng/L, for trickle filtration and activated sludge treatment
plant in England (Sabaliunas et al., 2003); 42-213 ng/L in Switzerland
(Singer et al., 2002); and from 19 WWTP in Australia the range was
23-434 ng/L with a median concentration of 108 ng/L (Ying and Kookana,
2007).

Triclosan was found in approximately 36 US streams (Kolpin et al., 2002)
where effluent from activated sludge waste water treatment plants,
trickle down filtration, and sewage overflow are thought to contribute
to the occurrence of triclosan in open water. For this study, the U.S.
Geological Survey surveyed a network of 139 streams across 30 states
during 1999 and 2000.  The selection of sampling sites was biased toward
streams susceptible to contamination (i.e. downstream of intense
urbanization and livestock production). The median concentration was 140
ng/L and the maximum concentration detected was 2300 ng/L (Kolpin et
al., 2002). In another study, storm water canal measurements over a 6
month period in Bayou St. John in Louisiana indicated that triclosan
ranged from below the detection level to 29 ng/L (Boyd et al., 2004).
Raw drinking water in Southern California was found to have 56 ng/L
triclosan and 49 ng/L triclosan in finished water (Loraine and
Pettigrove, 2006).  Other published data on surface water concentrations
of triclosan in the US indicated concentrations of 4 and 8 ng/L in the
upper Detroit river (Hua et al., 2005) and 56 ng/L in Arlington,
Virginia (Thomas and Foster, 2004). Published data on surface water
concentrations of triclosan in other countries indicated concentrations
of <3-10 ng/L in Germany (0.3-10 ng/L methyl-triclosan) (Bester, 2005);
19±1.4 ng/L in England (Sabaliunas et al., 2003); 11-98 ng/L in
Switzerland (Singer et al., 2002); 30 ng/L in Germany (Wind et al.,
2004); and in Australia 75 ng/L (Ying and Kookana, 2007).  Discharge
into U.S. surface waters has resulted in other researchers finding
triclosan from the low ng/L levels to a maximum of 2.3 µg/L (U.S. EPA,
2007).

Studies indicated that passive sampling with semi-permeable membrane
devices (SPMDs) were reliable for monitoring low concentrations of
methyl-triclosan in surface water downstream from WWTPs (Wind et al.,
2004; Sabaliunas et al., 2003). The data from these passive samplings
were added to a geo-referenced model GREAT-ER (Geography-Referenced
Regional Exposure Assessment Tool for European Rivers), and the
resulting PEC (Predicted Environmental Concentration) showed very good
accordance to the measured concentrations in the River Itter, in Germany
which were monitored in the same year. The concentrations did not
deviate more than by a factor of 3 (Wind et al., 2004). In England,
GREAT-ER was a useful tool for predicting and visualizing site-specific
concentrations of down-the drain chemicals but a larger volume of data
are needed to make the model more robust (Sabaliunas et al., 2003).

Contaminant profiles of radioisotope-dated sediment cores collected near
wastewater treatment plants in the Chesapeake Bay, Maryland and Jamaica
Bay, New York showed biocide occurrences coincided with biocide usage
and wastewater treatment strategies employed, first appearing in the
1950s (triclocarban) and 1960s (triclosan), and peaking in the late
1960s and 1970s at 24 ± 0.54 mg/kg dry wt. for triclocarban and 0.8 ±
0.4 mg/kg dry wt. for triclosan (Miller et al., 2008).  In the
Chesapeake Bay, triclocarban was consistently detected throughout the
top 33 cm of the sediment core, ranging from 1.5 to 3.5 mg/kg, in
sediment layers accumulated between ca. 1980 or 1990 and 2006.  In
contrast, triclosan at the same location was at or below the LOQ (0.05
mg/kg).  These levels are comparable to those found in Jamaica Bay in
sediment accumulated between ca. 1990 and 1996.  Analysis of Chesapeake
Bay sediment by tandem MS showed evidence of complete sequential
dechlorination of triclocarban to the transformation products dichloro-,
monochloro-, and unsubstituted carbanilide detected at maximums of 15.5
± 1.8, 4.1 ± 2.4, and 0.5 ± 0.1 mg/kg, respectively.  Concentrations
of all carbanilide congeners combined were correlated with heavy metals
(R2 > 0.64, P < 0.01), indicating wastewater as the principle pathway of
contamination.  This study indicates triclocarban, and to a lesser
extent triclosan, are persistent organic contaminants of estuarine
sediment with triclocarban being more persistent and more abundant than
triclosan.  In aged sediment, triclocarban can undergo slow anaerobic
dechlorination but the process is geographically variable and although
the chlorine substitution pattern can be varied, the overall quantity of
carbanilide species is not reduced.

A laboratory microcosm experiments were conducted using solutions
containing biodegradable dissolved organic carbon (BDOC; i.e. wastewater
effluent or a plant extract; 1.5 L), spiked with fresh pre-conditioned
(OECD 301, 1992) inocula (1.5 mL) derived from a mixed liquor of
activated sludge from two different waste water treatment plants at
original and diluted concentrations, and treated with individual test
compounds (pharmaceuticals and steroids; 1 to 3 (g/L), including
triclosan, to assess the factors controlling biotransformation under
aerobic conditions at 20-22°C (Lim et al., 2008).  Triclosan had no
effect on the rate of disappearance of the BDOC, suggesting negligible
suppression of microbial activity.  In full strength and dilute
wastewater effluent samples, triclosan disappeared within 1 day;
however, degradates of triclosan were not reported.

Triclosan was studied for 28 days at 20°C under aerobic conditions
using the manometric respirometry test (OECD method 301F) and inoculated
with activated sludge (Stasinakis, 2007).  After an initial lag phase of
16.5 ± 3.5 days, 52.1 ± 8.5% (n = 3) of the triclosan aerobically
biodegraded with a half-life of 1.8 ± 0.5 days.  A BOD value equal or
higher than 60% of the theoretical oxygen demand (ThOD), obtained within
28 days, is regarded as evidence of ready biodegradability.  Therefore,
biodegradation results for triclosan do not meet the definition of ready
biodegradability, but do indicate triclosan biodegradation in a waste
water treatment system.  There was no evidence of inhibitory effects of
triclosan on heterotrophic microorganisms or co-metabolic phenomena in
the presence of a readily biodegradable compound.

The aerobic and anaerobic biodegradation of triclocarban and triclosan
were studied in loam soil (pH 7.4) collected from agricultural land
without sludge amendments, treated at a concentration of 1 mg/kg soil,
and incubated in the dark at 22°C for 70 days (Ying et al., 2006). 
Under aerobic conditions, the soil remained microbially viable
throughout the study; however higher dehydrogenase activity was observed
in treated soil compared to untreated soils, especially the triclosan
treated soil.  Triclocarban decreased from 1.07 mg/kg at time 0 to 0.63
mg/kg at 70 days with a half-life of ca. 108 days based on first order
reaction kinetics.  Triclosan decreased from 1.01 mg/kg at time 0 to
0.08 mg/kg at 70 day with a half-life of 18 days.  A level III fugacity
computer model predicted a half-life of 60 days and the PBT Profiler
model for the soil compartment predicted a half-life of 120 days for
both triclocarban and triclosan under aerobic conditions.  Under
anaerobic conditions, little biodegradation of triclocarban and
triclosan occurred over the 70 day study period.  This study indicates
that both triclocarban and triclosan degrade by microbial processes in
soil under aerobic conditions, with triclosan being more biodegradable
than triclocarban.  However, both compounds are highly resistant to
biodegradation in soil under anaerobic conditions.

Triclosan concentrations determined in seawater samples collected in
2004 and 2005 from the German Bight (North Sea) in both the dissolved
phase and suspended particulate matters ranged from 0.8 to 6870 pg/L and
<1-95 pg/L, respectively (Xie et al., 2008).

C.	Summary of Published Literature on Triclosan As Related To
Bioaccumulation/Bioconcentration

From published literature on the aquatic toxicity of triclosan, the
bioconcentration of triclosan in zebrafish (Danio rerio) was assessed
according to OECD Guideline 305C (Orvos et al., 2002).  Zebrafish (mean
weight 0.33 g) were acclimated in 30 L glass aquaria containing 20 L of
dechlorinated tap water.  The aquaria were connected to a continuous
flow-through system (5 L/hour) that delivered [14C]triclosan test
solution (purity >98%; specific activity 0.470 MBq/mg) at test
concentrations of 3 and 30 (g/L.  The fish were subjected to an
accumulation period of 5 weeks and a depuration period of 2 weeks. 
Triplicate samples of muscle, digestive tract and head were collected
weekly and analyzed by incinerating in an Oxymat SA-101.  The [14C]CO2
was collected and quantified.

Average bioconcentration factors (BCF) for triclosan following the
5-week accumulation period were 4157 L/kg at 3 (g/L and 2532 L/kg at 30
(g/L.  The concentration of triclosan was greatest in the digestive
tract of two fish that were separated into muscle (fillet), digestive
system including stomach and intestines, and head.  Following 2 weeks of
depuration, average BCF values decreased to 41 L/kg at 3 (g/L and 32
L/kg at 30 (g/L.  Depuration rate constants were 0.142 and 0.141 per day
at 3 (g/L and 30 (g/L, respectively.  The predicted bioconcentration
factor for triclosan was calculated to be ca. 2500.  The lethal body
burden was determined to range from 0.7-3.4 mM/kg, indicating a narcosis
mode of action.

The effect of triclosan and formation of the degradation product,
methyl-triclosan, was studied in marine species in an estuarine
environment (Delorenzo et al., 2008).  Paleamonetes pugio larvae were
more sensitive to triclosan than adult shrimp or embryos with acute
aqueous toxicity values (96 h LC50) of 154 (g/L for larvae, 305 (g/L for
adult shrimp, and 651 (g/L for embryos.  The presence of sediment
decreased triclosan toxicity in adult shrimp (24 h LC50s were 620 (g/L
with sediment, and 482 (g/L without sediment).  The bacterium Vibrio
fischeri was more sensitive to triclosan than the grass shrimp, with a
15 minute aqueous IC50 value of 53 (g/L and a 15 minute spiked sediment
IC50 value of 616 (g/kg.  The phytoplankton species Dunaliella
tertiolecta was the most sensitive species tested, with a 96 h EC50
value of 3.55 (g/L.  After a 14-day exposure to 100 (g/L triclosan,
adult grass shrimp accumulated methyl-triclosan at concentrations
ranging from 137 pg/g to 704 pg/g, indicating formation of this
metabolite in a seawater environment and its potential to bioaccumulate
in higher organisms.  In limited surface water sampling from Charleston
Harbor, South Carolina, triclosan was detected at a maximum
concentration of 0.001 (g/L.

The 10-day LC 50s of triclosan for the midge Chironomus tentans and the
freshwater amphipod Hyalella azteca after waterborne exposures were 0.4
mg/L and 0.2 mg/L, respectively (Dussault et al., 2007).  A hazard
quotient (HQ) for benthic invertebrates was calculated by dividing the
lowest toxicity value by the highest exposure value found in the
literature, to which the uncertainty factor was applied.  The HQ for
triclosan was 11.5, indicating the compound could pose a risk to benthic
invertebrates.

D.	Contamination of Environmental Compartments and Data Gaps

In an effort to address the issues surrounding widespread detection of
triclosan and triclosan methyl residues in environmental compartments,
EPA took several approaches.  Initially, the Agency met, and discussed
these issues, with the antimicrobial pesticide registrants.  The Agency
emphasized the need for environmental modeling and monitoring that
addresses industrial sites where triclosan is incorporated into plastics
and textiles (since the bulk of antimicrobial pesticide uses involve
plastic and textile items impregnated with triclosan).  For consumer,
antimicrobial uses of triclosan-treated products (e.g., plastic and
textile items including toothbrushes, toys, clothing, footwear) the
Agency decided to perform screening level environmental modeling.  A
discussion on this effort is provided below:

Consumer Uses of Triclosan (e.g., Plastics or Textiles Treated With
Triclosan) – Screening Level Environmental Modeling

During this time the Agency received annual production data for
antimicrobial uses of triclosan from the registrants.  With receipt of
these data EPA decided that this information could be used in a
screening level, modeling effort for consumer uses of antimicrobial
products containing triclosan.  For this effort we decided to use the
Exposure and Fate Assessment Screening Tool, Version 2.0 (E-FAST 2)
developed by EPA/OPPTS/OPPT.

For this screening level environmental modeling effort we used two
modules from E-FAST 2:

(1) The Down-the-Drain (DTD) module of EFAST 2 to estimate
concentrations of triclosan  in surface water to which aquatic organisms
may be exposed as a result of potential releases of triclosan from
consumer uses; and

(2) The Probabilistic Dilution Model (PDM) option of EFAST 2 to estimate
the number of days per year that the concentration of triclosan in
surface water exceeds the concentration of concern for aquatic
organisms.

DTD and PDM assumptions:  For the DTD module the methodology assumes
that household wastewater undergoes treatment at a local wastewater
treatment plant and that treated effluent is subsequently discharged
into surface waters.  The DTD 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, the probabilistic dilution model (PDM) option
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.

Triclosan (Consumer) Environmental Modeling Assumptions:  Note that for
this screening level, modeling analysis of exposures to aquatic
organisms from uses of triclosan under EPA’s jurisdiction, we made a
simplifying assumption that all of the triclosan produced annually for
antimicrobial uses 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 were, therefore, assumed to be negligible.  We assumed
that triclosan was released into household wastewater during washing and
rinsing of products treated with triclosan as a materials preservative
or as a functional component.  Thus, we assumed that 100 % of household,
antimicrobial uses of triclosan goes “down-the-drain” so to speak
– a highly unlikely assumption as we discuss later.  Also, 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.  Further, only acute
concentrations of concern were evaluated for aquatic organisms since
acceptable chronic aquatic data are not available.  (However,
considering the low probability of triclosan being released into
household wastewater and surface waters, EPA also concludes that chronic
aquatic risks are unlikely from consumer uses of triclosan-treated
plastic and textile items.)

DTD and PDM (Consumer) Environmental Modeling Results:  As outlined in
the attached Appendix, the Agency performed screening level
environmental modeling and concluded that, if all of the triclosan
produced annually for antimicrobial uses is released to surface water as
a result of consumer uses, then:

Aquatic Animals:  Estimated concentrations of triclosan in surface water
do not exceed concentrations of concern for acute risk presumptions for
aquatic animals.  (See Appendix, Table 2.)

Aquatic Animals:  Estimated concentrations of triclosan in surface water
do not exceed concentrations of concern for endangered species risk
presumptions for aquatic animals.  (See Appendix, Table 3.)

Aquatic Vascular Plants:  Estimated concentrations of triclosan in
surface water do not exceed concentrations of concern for endangered
species risk presumptions for aquatic vascular plants (e.g., duckweed,
Lemna gibba).  (See Appendix, Table 4.)

Aquatic Non-Vascular Plants:  Estimated concentrations of triclosan in
surface water do exceed concentrations of concern for acute risk
presumptions for species that represent non-vascular freshwater plants
(i.e., algae).  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.  (See Appendix, Table 4.)

Adjustments to DTD and PDM (Consumer) Environmental Modeling Results: 
As indicated above, the Agency performed this DTD and PDM modeling in an
effort to estimate:

(1) Concentrations of triclosan in surface water [from antimicrobial
uses of triclosan (e.g., triclosan-treated plastic and textile items in
households) to which aquatic organisms may be exposed as a result of
potential releases of triclosan from these consumer uses; and

(2) Number of days per year that the concentration of triclosan in
surface water exceeds the concentration of concern for aquatic
organisms.

A critical assumption in this screening level, modeling analysis was
that all of the triclosan produced annually for antimicrobial uses is
released to surface water as a result of consumer uses.  That is, 100 %
of all triclosan produced annually is released into household wastewater
during washing and rinsing of products treated with triclosan as a
materials preservative or as a functional component.

However, in an effort to check this 100 % release value used above for
consumer scenarios, EPA reexamined available textile leaching data and
determined that the 100 % assumption (for release of triclosan into
household wastewater) is highly unlikely.  Specifically, available data
for textile leaching of triclosan indicate that triclosan leaches from a
variety of fabrics in the range of 0.00 % to 0.55 %. 

Conclusions Based On Adjusted DTD and PDM (Consumer) Environmental
Modeling Results:  Considering the above textile leaching data, one can
reduce all calculations (for estimated triclosan concentrations and
concentrations of concern) presented in the attached Appendix by a
factor of 100.  In doing so, EPA concludes that for aquatic animals and
plants (vascular and non-vascular), estimated concentrations of
triclosan in surface water do not exceed concentrations of concern for
acute risk presumptions for any of these organisms.  What this means is
that the Agency can reasonably conclude that the antimicrobial uses of
triclosan (e.g., triclosan-treated plastic and textile items in
households) are unlikely to contribute significant quantities of
triclosan into household wastewater and eventually to surface water.

Industrial Uses of Triclosan (e.g., Triclosan Incorporation Into
Plastics or Textiles In Industrial Setting) – Environmental Modeling
and/or Monitoring

	As discussed above, the Agency has met with the triclosan,
antimicrobial use, registrants and emphasized the need for environmental
modeling and monitoring that addresses industrial sites where triclosan
is incorporated into plastics and textiles (since the bulk of
antimicrobial pesticide uses involve plastic and textile items
impregnated with triclosan).  Since little is known about how much, if
any, triclosan is released from such industrial sites into effluents and
the environment (e.g., surface waters), the Agency is requiring that the
registrants perform environmental modeling and monitoring to address
this issue.  The registrant is required to sample effluents from such
facilities and receiving (surface) waters adjacent to these facilities,
determining the extent and duration of triclosan and major
degradates/metabolites (e.g., triclosan methyl).  Prior to beginning the
environmental monitoring the registrant must submit a protocol to the
Agency for approval.  Additionally (see table below), an anaerobic
aquatic metabolism study (OPPT: 835.4400) is required.  Submission of
these data, along with other available environmental fate studies, will
enable the Agency to better interpret the results of the environmental
monitoring study.

 	Summary Table of Environmental Fate Data Requirements

	Considering the above discussion, the Agency requires the following
environmental fate data:

Environmental Fate Data Requirements for Triclosan



OPP Guideline	Data

 Requirement	MRID

No.	Data Requirement

 Status

161-1

(preferred)	Hydrolysis	420279-08	Supplemental 

(No additional hydrolysis testing required)

161-2 or

835.2240	Photodegradation in Water	430226-08	Satisfied

162-1 or

OECD 307 or 835.4100

	Aerobic soil metabolism	472614-01	Satisfied

OECD 308 or

OPP 162-4 or 

835.4300	Aerobic aquatic metabolism	472614-02	Satisfied

162-3 or

835.4400	Anaerobic aquatic metabolism	N/A	Data Gap

None	Monitoring of representative U.S. surface waters	N/A	Data Gap

REFERENCES

UNPUBLISHED REFERENCES:

   MRID   	                                                  Citation   
                                                     	

420279-08	Pointurier, R. 1990.  Irgasan® DP 300 – Report on
Hydrolysis as a Function of pH.  Unpublished study performed and
submitted by Ciba-Geigy Ltd., Basel, Switzerland.

430226-08	Spare, W. 1993.  Aqueous Photolysis of Triclosan.  Agrisearch
Project No.: 12208.  Unpublished study performed by Agrisearch Inc.,
Frederick, MD; and submitted by Ciba-Geigy Corporation, Greensboro, NC.

472614-01	Adam, D. (2007) (Carbon 14)-Triclosan: Degradation and
Metabolism in Three Soils Incubated Under Aerobic Conditions. Project
Number: B12835. Unpublished study prepared by RCC Umweltchemie Ag.

472614-02	Adam, D. (2006) (Carbon 14)-Triclosan: Route and Rate of
Degradation in Aerobic Aquatic Sediment Systems. Project Number: A33300.
Unpublished study prepared by RCC Umweltchemie Ag.

472614-03	Volkel, W. (2007) The Effects of Triclosan on Soil
Nitrification. Project Number: A89954. Unpublished study prepared by RCC
Umweltchemie Ag.

472614-04	Volkel, W. (2006) The Effects of Triclosan on Soil
Respiration. Project Number: A88312. Unpublished study prepared by RCC
Umweltchemie Ag.

472614-06	Christensen, K. (1994) Triclosan - Determination of Anaerobic
Aquatic Biodegradation. Project Number: 93/12/5076. Unpublished study
prepared by Springborn Laboratories Inc.

472614-07	Christensen, K. (1994) Triclosan - Aerobic Biodegradation in
Water. Project Number: 93/4/4731. Unpublished study prepared by
Springborn Laboratories Inc.

--------------	The Estimation Programs Interface (EPI) Suite.  Windows
based suite of physical/chemical properties and environmental estimation
models developed by the US EPA’s Office of Prevention, Pesticides and
Toxic substances (OPPTS) and Syracuse Research Institute (SRC). 
Physical properties of Triclosan.  EPI Suite Summary (v3.12).  
HYPERLINK "http://www.epa.gov/opptintr/exposure/docs/EPISuitedl.htm"
http://www.epa.gov/opptintr/exposure/docs/EPISuitedl.htm 

-------------	Hazard Substances Data Bank (HSDB).  A Database of the
National Library of Medicine’s TOXNET System.  Triclosan: 
Environmental Fate and Exposure.  HYPERLINK
"Triclosan%20Fate%20Chapter%20for%20RED.updated%2012-21-06.doc"
http://toxnet.nlm.nih.gov 

-------------	U. S. Environmental Protection Agency, Office of Water. 
Summary of Available Aquatic Toxicity Data for Aquatic Life Water
Quality Criteria Development for Triclosan.  Draft: August 16, 2007.

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Sign-off Date      :  09/11/08

DP Barcode No.  :  D343543



Appendix:

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]

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

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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

	

 For a full discussion of the Agency’s screening level modeling effort
for triclosan, see the attached Appendix:  Estimates of Exposures and
Risks To Aquatic Organisms From Releases Of Triclosan to Surface Water
As A Result of Uses Under EPA’s Jurisidiction.

 Note that the Agency focused on textile items (e.g., clothing) which
are likely to be washed or rinsed regularly rather than plastic items
(e.g., toys) which are not as likely to be washed regularly.

  EPA assumes that leaching values for plastic are of the same magnitude
as for textile products.  Note that the Agency used the 0.55 % leaching
value in its evaluation for children who may mouth (incidental oral
ingestion) plastic items (e.g., toys).

  Note that based on the results of these data additional data (e.g.,
ecological effects) may be required in order for the Agency to complete
environmental risk assessments.

 Prior to beginning this study the registrant must submit a protocol to
the Agency for approval.

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

	  PAGE  1  of   NUMPAGES  42 	

