UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

   OFFICE OF

                                                                        
                                    PREVENTION, PESTICIDES AND 

            TOXIC SUBSTANCES

February 22, 2008

MEMORANDUM

SUBJECT:		Preliminary Ecological Hazard and Environmental Risk
Assessment Science Chapter for the Triclosan Reregistration Eligibility
Decision (RED) Document

			DP Barcode:  341569		Reregistration Case No.:  2340

FROM:		Genevieve Angle, Biologist

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

TO:			Mark Hartman, Branch Chief

Diane Isbell, Team Leader

Regulatory Management Branch II

Antimicrobials Division (7510P)

Timothy McMahon, Risk Assessor

THRU:		Siroos Mostaghimi, Team Leader, Team 1

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 Names

5-Chloro-2-	54901		3380-34-5	Triclosan

  (2,4-dichlorophenoxy)phenol

Attached is the Ecological Hazard and Environmental Risk Assessment
Science Chapter for the Triclosan RED Document.

ECOLOGICAL HAZARD AND ENVIRONMENTAL 

RISK ASSESSMENT CHAPTER

Triclosan

PC Code: 054901

CASE No.: 2340

02/22/08

Genevieve Angle - Biologist

Antimicrobials Division

Office of Pesticide Programs

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, NW

Washington, DC 20460

Table of Contents

												    Page

Executive Summary
………………………………………………………………
……………… 5

1.  Ecological Toxicity Data . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6  

A.  Toxicity to Terrestrial Animals . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . .6 

1.  Birds, Acute  . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . 6

2.  Birds, Subacute. . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . 8 

3.  Mammals, Acute and Chronic . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . .9  

B.  Toxicity to Aquatic Animals . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . .9 

1.  Freshwater Fish, Acute . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . .9  

2.  Freshwater Invertebrates, Acute . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . .10  

3.  Estuarine and Marine Organisms, Acute . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . .11

4.  Aquatic Organisms, Chronic . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . .12 

C.  Toxicity to Plants . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . ..12

II.  Risk Assessment and Risk Characterization . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . .  . . ..13

A.  Environmental Fate Assessment Summary . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . .. . . . .14 

B.  Environmental Exposure And Qualitative Environmental Risk
Assessment… . .. . . . . ..15 

C.  Endangered Species Considerations . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . .  . . . . . . . . . . .17

III.  Confirmatory Data Required. . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . .. . . . . . . . . ..18   

IV.  Label Hazard Statements for Terrestrial and Aquatic Organisms. . .
. . . . . . . .  . . . . . . . . .. 19

V.  References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . . . 20

LIST OF TABLES

																			  Page

Table 1 – Acute Oral Toxicity of Triclosan to Birds. …. . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . .8 

				

Table 2 – Subacute Oral Toxicity of Triclosan to Birds. . . . . . ….
. . . . . . . . . . . . . . . . . . . . . . 9

Table 3 – Acute Toxicity of Triclosan to Freshwater Fish. . . . . . .
. . . . . …. . . . . . . . . . . . . . . 10

Table 4 – Acute Toxicity of Triclosan to Freshwater Invertebrates. . .
. . . …. . . . . . . . . . . . . . 11 

Table 5 – Chronic Toxicity of Triclosan to Freshwater Organisms. . . .
…. . . . . . . . . . . . . . . . 12

Table 6 – Toxicity of Triclosan to Aquatic Plants. . . . . . . . . . .
. …. . . . . . . . . . . . . . . . . . . . ..13

Ecological Hazard and Environment Risk Assessment

For Triclosan

Executive Summary:

	Only a small portion of the uses of triclosan are regulated by the U.S.
EPA and therefore covered in this document.  Triclosan is currently
registered by the EPA as a bacteriostat, fungicide/fungistat and
mold/mildewcide for materials preservation, residential and public
access premises and commercial, institutional and industrial premises
and equipment.   Its materials preservation uses include: adhesives,
fabrics, vinyl, latex, plastics, polyethylene, polyurethane, synthetic
polymers, styrene, floor wax emulsions, rope, textiles, caulking
compounds, sealants, coatings, polypropylene, rubber, inks, cellulosic
materials, slurries, films and latex paints.  The residential and public
access premises uses include: brooms, mulch, floors, shower curtains,
awnings, tents, mattresses, toothbrushes, toilet bowls, urinals, garbage
cans, refuse container liners, insulation, concrete mixtures, grouts,
air filter materials, upholstery fabrics, human wastes and rugs/carpets.
 The commercial, institutional and industrial premises and equipment
uses include: conveyor belts, fire hoses, dye bath vats and ice making
equipment. 

	An ecological risk assessment is not typically conducted for the types
of uses registered for triclosan.  However, since triclosan has been
detected in natural waters, EPA has performed a qualitative
environmental risk assessment using monitoring levels of triclosan found
in waterways and toxicity values from the tables in section I to develop
risk quotients (RQs) and compare them to levels of concern (LOCs) for
triclosan.  LOCs were not exceeded for fish but were exceeded for
aquatic plants.  There were no acceptable acute toxicity studies for
freshwater invertebrates or estuarine and marine organisms nor were
there any acceptable chronic toxicity studies available for aquatic
organisms.  Therefore, risk to these species could not be assessed.

Data Gaps:  

Freshwater invertebrate acute study (850.1010);

As outlined in the environmental fate chapter for triclosan, the
registrant is required to provide a scientific rationale, including
appropriate modeling (e.g., surface water modeling), that addresses and
quantifies the amounts of triclosan and triclosan transformation
products (e.g., triclosan methyl) occuring in various environmental
compartments (e.g., surface waters, biosolids, soil, fish, shellfish)
from triclosan antimicrobial pesticide uses;

Relative to the above requirement, if the registrant is not able to
provide a satisfactory scientific rationale that determines the
quantities of triclosan and triclosan transformation products in various
environmental compartments, then EPA will assume that the present levels
of triclosan and triclosan transformation products detected in such
compartments occurs because of registered antimicrobial use patterns. 
In this case, OPP will require the environmental fate data outlined in
the triclosan environmental fate chapter; and

Depending on the results of the environmental fate studies, which may be
required (see triclosan environmental fate chapter), additional acute
and chronic nontarget organism studies may be required.  These include
the following studies:

	a. Estuarine/marine fish acute study (850.1075) [Technical Grade Active
	Ingredient (TGAI)];

		b. Estuarine/marine shrimp acute study (850.1035) (TGAI);

	c. Estuarine/marine mollusk acute study (850.1025) (TGAI);

		d. Fish early life-stage (freshwater) study (850.1400) (TGAI);

		e. Aquatic invertebrate (freshwater) life-cycle study (850.1300)
(TGAI);

		f. Fish life-cycle study (850.1500);

		g. Fish bioconcentration study – BCF (850.1730) (TGAI);

		h. Acute sediment toxicity to freshwater invertebrates (850.1735)
(TGAI); 			i. Acute sediment toxicity to estuarine invertebrates
(850.1740) (TGAI); 			and

			j. Additional plant toxicity testing:  an additional algal toxicity
test 					(850.5400) with the freshwater green alga, Selenastrum
capricornutum; 				and studies on the rooted freshwater macrophyte rice
(Oryza sativa) – 				850.4225 and 850.4250 (2 tests on seedling
emergence and vegetative 				vigor).

Label Hazard Statements/Use Recommendations:

Triclosan labels must state:  

“This pesticide is toxic to fish and aquatic invertebrates.”

"Do not discharge effluent containing this product into lakes, streams,
ponds, estuaries, oceans, or other waters unless in accordance with the
requirements of a National Pollutant Discharge Elimination System
(NPDES) permit and the permitting authorities are notified in writing
prior to discharge.  Do not discharge effluent containing this product
to sewer systems without previously notifying the local sewage treatment
plant authority.  For guidance contact your State Water Board or
Regional Office of the EPA."

I.	Ecological Toxicity Data

	The toxicity endpoints presented below are based on the results of
ecotoxicity studies submitted to EPA to meet the Agency’s data
requirements for the uses of triclosan.

	A.	Toxicity to Terrestrial Animals

(1)	Birds, Acute 

	In order to establish the toxicity of triclosan to avian species, the
Agency requires an acute oral toxicity study using the technical grade
active ingredient (TGAI).  The preferred-test species is either mallard
duck (a waterfowl) or bobwhite quail (an upland game bird).  The results
of three acute oral toxicity studies, submitted for triclosan, are
provided in the following table (Table 1).



Table 1.  Acute Oral Toxicity of Triclosan to Birds

Species	

Chemical,

% Active Ingredient

(a.i.)

Tested	

Endpoint

(mg/kg)	

Toxicity Category	

Satisfies Guidelines/

Comments	

Reference

(MRID No.)

Mallard duck

(Anas platyrhynchos)	Triclosan 99.7%	LD50 = >2150

NOAEL = 2150

	Relatively nontoxic	Yes (core)

- 14-day test duration

- 19 weeks of age	430226-03

Bobwhite quail

(Colinus virginianus)	Triclosan 99.7%	LD50 = 825

NOAEL = <147	Slightly toxic	Yes (core)

- 14-day test duration

- 21 weeks of age	430226-02

Bobwhite quail

(Colinus virginianus)	Triclosan 3.89%	LD50 = >2000

NOAEL = N.R.

	Relatively nontoxic	Yes (core for formulated product)

	410089-10



	These three acceptable acute oral toxicity studies indicate that
triclosan is slightly toxic to relatively nontoxic to birds on an acute
oral basis. The guideline requirement OPPTS 850.2100/(71-1) is
satisfied.  

(2)	Birds, Subacute

	A subacute dietary study using the TGAI may be required on a
case-by-case basis depending on the results of lower-tier ecological
studies and pertinent environmental fate characteristics in order to
establish the toxicity of a chemical to avian species.  This testing was
required for triclosan.  The preferred-test species is either the
mallard duck or bobwhite quail.  The results of two subacute dietary
toxicity studies, submitted for triclosan, are provided in the following
table (Table 2).



Table 2.  Subacute Oral Toxicity of Triclosan to Birds

Species	

Chemical,

% Active Ingredient

(a.i.)

Tested	

Endpoint

(ppm)	

Toxicity Category	

Satisfies Guidelines/

Comments	

Reference

(MRID No.)

Bobwhite quail

(Colinus virginianus)	Triclosan 99.7%	LC50 (diet) = >5000

NOAEC = 1250	Relatively nontoxic	Yes (core)

-	8-day test duration

-	13 days of age	430226-04

Bobwhite quail

(Colinus virginianus)	Triclosan 

3.89%	LC50 (diet) = >5000

NOAEC = N.R.	Relatively nontoxic	Yes (core for formulated product)

- 8-day test duration

- 7-10 days of age 	410089-11



	The results of these two acceptable studies indicate that triclosan is
relatively nontoxic to avian species through subacute dietary exposure.
These studies fulfill guideline requirement OPPTS 850.2100/ (71-2a –
Bobwhite quail/71-2b – Mallard duck). 

 (3)	Mammals, Acute and Chronic Toxicity

Wild mammal testing is not required by the Agency.  In most cases, rat
toxicity values obtained from studies conducted to support data
requirements for human health risk assessments substitute for wild
mammal testing.  Refer to the human toxicology chapter of this RED for
mammalian toxicity data.  Also, refer to the toxicology chapter for
information on triclosan’s potential as an endocrine disruptor.

B.	Toxicity to Aquatic Animals

	The Agency requested that aquatic toxicity studies be conducted with
triclosan since, under typical use conditions, it may be introduced into
the aquatic environment.

(1)	Freshwater Fish, Acute

	In order to establish the acute toxicity of triclosan to freshwater
fish, the Agency requires freshwater fish toxicity studies using the
TGAI.  The preferred test species are rainbow trout (a coldwater fish)
and bluegill sunfish (a warmwater fish).  The results of 5 freshwater
fish acute studies submitted for triclosan are presented in Table 3.



 Table 3.  Acute Toxicity of Triclosan to Freshwater Fish 

Species	

Chemical,

% Active Ingredient

(a.i.)

Tested	

Endpoint

(mg/L)	

Toxicity Category	

Satisfies Guidelines/

Comments	

Reference

(MRID No.)

Rainbow Trout (Oncorhynchus mykiss)	Triclosan

99.3%	LC50 = 0.288

NOAEC = 0.100	Highly toxic	Yes (core)

-	96-hr test duration

-	static test system	439693-01

Fathead minnow

(Pimephales promelas)	Triclosan

99.7%	LC50 = 0.26

LOEC = 0.18

NOAEC = 0.10

	Highly toxic	No (supplemental)

-	96-hr test duration

-	static test system

-  nominal concentrations not verified	430460-01

Bluegill sunfish (Lepomis macrochirus)	Triclosan 3.89%	LC50 = 37.2 

NOAEC = N.R.	Slightly toxic	Yes (core for formulated product)

-  96-hr test duration

-  static test system	410089-13

Rainbow Trout (Oncorhynchus mykiss)	Triclosan 3.89%	LC50 = 23.4

NOAEC = N.R.	Slightly toxic	Yes (core for formulated product)

-	96-hr test duration

-	static test system	410089-12



	Freshwater acute toxicity tests indicate that triclosan is highly toxic
to slightly toxic to fish on an acute basis.  These studies fulfill
guideline requirement OPPTS 850.1075 (72-1a&b).  Because acute toxicity
to fish is <1.0 mg/L, the environmental hazard section of triclosan
labels must state: “This pesticide is toxic to fish.”

	(2)	Freshwater Invertebrates, Acute

	The Agency requires a freshwater aquatic invertebrate study using the
TGAI to establish the acute toxicity to freshwater invertebrates.  The
preferred test species is Daphnia magna.  The results of three studies
submitted for triclosan are provided in the following table (Table 4). 
Note that in a search of the available data on triclosan, the U.S.
EPA’s Office of Water found an EC50 as low as 0.13 mg/L for the
Cladoceran Ceriodaphnia dubia (U.S. EPA, 2007).



	Table 4.  Acute Toxicity of Triclosan to Freshwater Invertebrates

 

Species	

Chemical,

% Active Ingredient

(a.i.)

Tested	

Endpoint

(mg/L)	

Toxicity Category	

Satisfies Guidelines/

Comments	

Reference

(MRID No.)

Waterflea (Daphnia magna)	Triclosan

99.7%	EC50 = 0.39 

NOAEC = 0.10 (a.i.)	Highly toxic	No (supplemental)

-	48-hr test duration

-	static test system

-  nominal concentrations not verified	430460-02

Waterflea (Daphnia magna)	Triclosan 

3.89%	LC50 = 0.42

NOAEC = N.R.	Highly toxic	No (supplemental)

-  48-hr test                duration

-  static test system

-  lack of pH and DO measurements and formulated product used	410089-14





	The results of these studies indicate that triclosan is highly toxic to
freshwater invertebrates.  These studies do not fulfill guideline
requirement OPPTS 850.1010 (72.2a).  Because the acute aquatic
invertebrate toxicity values are < 1.0 mg/L, the environmental hazard
section of triclosan labels must state:  “This pesticide is toxic to
aquatic invertebrates.”

(3)	Estuarine and Marine Organisms, Acute

	Acute toxicity testing with estuarine and marine organisms using the
TGAI is required when the end-use product is intended for direct
application to the marine/estuarine environment or effluent containing
the active ingredient is expected to reach this environment.  The
preferred fish test species is the sheepshead minnow.  The preferred
invertebrate test species are mysid shrimp and eastern oysters.  At this
time this testing is not required for triclosan, but is dependent upon
the results of environmental fate data which may be required.  (See
triclosan environmental fate chapter and comments above on potential
data requirements).  No studies have been submitted to fulfill these
data requirements (OPPTS 850.1075/(72-3a), OPPTS 850.1035/(72-3c) and
OPPTS 850.1025/(72-3b)).



(4)	Aquatic Organisms, Chronic

	Chronic toxicity testing (fish early life stage and aquatic
invertebrate life cycle) is required for pesticides when certain
conditions of use and environmental fate apply.  The preferred
freshwater fish test species is the fathead minnow.  The preferred
freshwater invertebrate is Daphnia magna.  At this time this testing is
not required for triclosan, but is dependent upon the results of
environmental fate data which may be required.  (See triclosan
environmental fate chapter and comments above on potential data
requirements).

The results of one toxicity study submitted for triclosan is presented
in Table 5.  Note that in a search of the available data on triclosan,
the U.S. EPA’s Office of Water found a NOEC as low as 0.006 mg/L for
the Cladoceran Ceriodaphnia dubia (U.S. EPA, 2007).

Table 5.  Chronic Toxicity of Triclosan to Freshwater Organisms

Species	

Chemical,

% Active Ingredient

(a.i.)

Tested	

Endpoint

(mg/L)	

Satisfies Guidelines/

Comments	

Reference

(MRID No.)

Waterflea 

(Daphnia magna)	Triclosan

% purity unknown	LOEC = <0.1388

NOAEC = N.R.

	No (supplemental)

-  21-day test             duration 

-  static renewal test     system

-  growth not measured as a chronic endpoint

-  % a.i. not given 

-  raw data missing

-  concentration analysis insufficient	437407-01

	

No fathead minnow study has been submitted. The study on the waterflea
does not fulfill the guideline requirement for a chronic aquatic
invertebrate study (OPPTS 850.1300).

Toxicity to Plants

	Non-target plant phytotoxicity testing is required for pesticides when
certain conditions of use and environmental fate apply.  At this time
this testing is not required for triclosan, but is dependent upon the
results of environmental fate data which may be required.  (See
triclosan environmental fate chapter and comments above on potential
data requirements).  However, testing has been conducted with triclosan
on several aquatic plant species.  Testing is normally conducted with
one species of aquatic vascular plant (Lemna gibba) and four species of
algae:  (1) freshwater green alga, Selenastrum capricornutum, (2) marine
diatom, Skeletonema costatum, (3) freshwater diatom, Navicula
pelliculosa, and (4)  bluegreen cyanobacteria, Anabaena flos-aquae.  The
rooted aquatic macrophyte rice (Oryza sativa) is also tested in seedling
emergence and vegetative vigor tests.

	Four studies that evaluate the toxicity of triclosan to freshwater
aquatic plants have been submitted. Results of these studies are
presented in Table 6.  Note that in a search of the available data on
triclosan, the U.S. EPA’s Office of Water found an EC50 as low as
0.0007 mg/L for the green alga Scenedesmus subspicatus and an EC25 as
low as 0.00067 mg/L for the blue-green alga Anabaena flos-aquae (U.S.
EPA, 2007).

Table 6.  Toxicity of Triclosan to Aquatic Plants

Species	

Chemical,

% Active Ingredient

(a.i.)

Tested	

Endpoint 

(mg/L)	

Satisfies Guidelines/

Comments	

Reference

(MRID No.)

Marine Diatom (Skeletonema costatum)	Triclosan 

99.5%	EC50 = >0.066

NOEC = 0.0126	Yes (core)

-  96-hour test duration

-  static test system	444228-01

Freshwater Diatom (Navicula pelliculosa)	Triclosan 

99.5%	EC50 = 0.016

NOEC = 0.005	Yes (core)

-  96-hour test duration

-  static test system	444228-01

Bluegreen Cyanobacteria (Anabaena flos-aquae)	Triclosan 

99.5%	EC50 = 0.0012

NOEC = N.R.	Yes (core)

-  96-hour test duration

-  static test system	444228-01

Duckweed (Lemna gibba)	Triclosan 

99.5%	EC50 = >0.0625

NOEC = 0.0125	Yes (core)

-	7-day test duration

-	static test system	444228-01



	The guideline requirement for an algal toxicity test (850.5400, 123-2)
is partially fulfilled.  One additional algal toxicity test under
850.5400 is outstanding: a test with the freshwater green alga,
Selenastrum capricornutum.  The other non-target aquatic plant toxicity
requirement, floating freshwater aquatic macrophyte duckweed (Lemna
gibba) – guideline 850.4400 - is satisfied.  Studies on the rooted
freshwater macrophyte rice (Oryza sativa) – 850.4225 and 850.4250 (2
tests on seedling emergence and vegetative vigor) -- have not been
submitted.

II.	Risk Assessment and Characterization

	The triclosan uses that EPA regulates are classified as “indoor”
uses.  An ecological risk assessment is not typically conducted for the
types of uses registered for triclosan.  However, since triclosan has
been detected in natural waters (see triclosan environmental fate
chapter), EPA has performed a qualitative environmental risk assessment
using monitoring levels of triclosan found in waterways and toxicity
values from the tables in section I to develop risk quotients (RQs) and
compare them to levels of concern (LOCs) for triclosan.

	 A.        Environmental Fate Assessment Summary 

	Triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol] is a white
crystalline powder with low solubility in water (12 ppm).  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 has been identified, DCP (2,4-dichlorophenol),
which was a maximum of 93.8-96.6% of the applied at 240 minutes
post-treatment.

	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 exists partially 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 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.

	  SEQ CHAPTER \h \r 1 Of the 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 trickle down filtration ranging from 58-86% (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.  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).

  

B.	Environmental Exposure and Qualitative Environmental Risk Assessment

Risk assessment integrates the results of the exposure and ecotoxicity
data to evaluate the likelihood of adverse ecological effects. One
method of integrating the results of exposure and ecotoxicity data is
called the quotient method.  For this method, risk quotients (RQs) are
calculated by dividing exposure estimates by ecotoxicity values, both
acute and chronic:  

       

           RQ = EXPOSURE/TOXICITY 

 

RQs are then compared to levels of concern (LOCs).  These LOCs are
criteria used by OPP to indicate potential risk to nontarget organisms
and the need to consider regulatory action.  The criteria indicate that
a pesticide used as directed has the potential to cause adverse effects
on nontarget organisms.  LOCs currently address the following risk
presumption categories: (1) acute - the potential for acute risk is
high, regulatory action may be warranted in addition to restricted use
classification; (2) acute restricted use - the potential for acute risk
is high, but this may be mitigated through restricted use
classification; (3) acute endangered species - the potential for acute
risk to endangered species is high, and regulatory action may be
warranted, and (4) chronic risk - the potential for chronic risk is
high, and regulatory action may be warranted, (5) non-endangered plant
risk – potential for effects in non-target plants, and (6) endangered
plant risk – potential for effects in endangered plants.   Currently,
EFED does not perform assessments for chronic risk to plants, acute or
chronic risks to nontarget insects, or chronic risk from granular/bait
formulations to birds or mammals.

The ecotoxicity test values (measurement endpoints) used in the acute
and chronic risk quotients are derived from required studies.  Examples
of ecotoxicity values derived from short-term laboratory studies that
assess acute effects are: (1) LC50 (fish and birds), (2) LD50 (birds and
mammals), (3) EC50 (aquatic plants and aquatic invertebrates) and (4)
EC25 (terrestrial plants).  Examples of toxicity test effect levels
derived from the results of long-term laboratory studies that assess
chronic effects are: (1) LOAEC (birds, fish, and aquatic invertebrates),
and (2) NOAEC (birds, fish and aquatic invertebrates). For birds and
mammals, the NOAEC generally is used as the ecotoxicity test value in
assessing chronic effects, although other values may be used when
justified. However, the NOAEC is used if the measurement endpoint is
production of offspring or survival.

Risk presumptions, along with the corresponding RQs and LOCs are
tabulated below.



Risk Presumptions for Terrestrial Animals



Risk Presumption	

RQ	

LOC



Birds and Wild Mammals



Acute Risk	

EEC1/LC50 or LD50/sqft2 or LD50/day3	

0.5



Acute Restricted Use	

EEC/LC50 or LD50/sqft or LD50/day (or LD50 < 50 mg/kg)	

0.2



Acute Endangered Species	

EEC/LC50 or LD50/sqft or LD50/day 	

0.1



Chronic Risk	

EEC/NOAEC	

1

 1  abbreviation for Estimated Environmental Concentration (ppm) on
avian/mammalian food items   

 2    mg/ft2             	3  mg of toxicant consumed/day

   LD50 * wt. of bird             	LD50 * wt. of bird  

Risk Presumptions for Aquatic Animals	 



Risk Presumption	

RQ 	

LOC



Acute Risk	

EEC1/LC50 or EC50	

0.5



Acute Restricted Use	

EEC/LC50 or EC50	

0.1



Acute Endangered Species	

EEC/LC50 or EC50	

0.05



Chronic Risk	

EEC/MATC2 or NOAEC	

1



 1  EEC = (ppm or ppb) in water

 2  MATC = maximum allowable toxicant concentration

Risk Presumptions for Plants	

	





Risk Presumption	

RQ	

LOC



Terrestrial and Semi-Aquatic Plants 



Acute Risk	

EEC/EC25	

1



Acute Endangered Species	

EEC/EC05 or NOAEC	

1



Aquatic Plants



Acute Risk	

EEC1/EC50	

1



Acute Endangered Species	

EEC/EC05 or NOAEC 	

1



EEC = (ppb/ppm) in water 

	Triclosan was found in approximately 36 US streams (Klopin 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 of
triclosan was 40 ng/L and the maximum concentration detected was 280
ng/L (Klopin et al., 2002).  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 the toxicity tables in section I above, the highest toxicity in an
acceptable fish study was achieved in a study on the rainbow trout
(Oncorhynchus mykiss).  The LC50 value obtained in this study was 0.288
mg/L (MRID 439693-01).  There were no acceptable acute toxicity studies
for freshwater invertebrates or estuarine and marine organisms nor were
there any acceptable chronic toxicity studies available for aquatic
organisms.  Therefore, risk to these species cannot be assessed.  The
highest toxicity in an acceptable aquatic plant toxicity study was
achieved in a study on the bluegreen cyanobacteria (Anabaena
flos-aquae).  The EC50 value obtained in this study was 0.0012 mg/L and
no NOEC was reported (MRID 444228-01).   

For aquatic animals the LOC ranges from 0.05 for endangered species to 1
for chronic risks.  Comparing the maximum concentration of triclosan
found in U.S. surface waters (2.3 µg/L or 0.0023 mg/L) to the highest
toxicity found in a fish acute study (0.288 mg/L), an RQ of 0.008 is
obtained.  This is less than all LOCs for aquatic animals and therefore
the potential for triclosan to cause adverse effects on fish is not
high.

For aquatic plants the LOC is 1.  Comparing the maximum concentration of
triclosan found in US streams (2.3 µg/L or 0.0023 mg/L) to the highest
toxicity found in aquatic plants (0.0012 mg/L), an RQ of 1.92 is
obtained.  This is higher than the LOC and therefore the potential for
acute risk to aquatic plants from triclosan exists.

      Endangered Species Considerations

Section 7 of the Endangered Species Act, 16 U.S.C. Section 1536(a)(2),
requires all federal agencies to consult with the National Marine
Fisheries Service (NMFS) for marine and anadromous listed species, or
the United States Fish and Wildlife Services (FWS) for listed wildlife
and freshwater organisms, if they are proposing an "action" that may
affect listed species or their designated habitat.  Each federal agency
is required under the Act to insure that any action they authorize,
fund, or carry out is not likely to jeopardize the continued existence
of a listed species or result in the destruction or adverse modification
of designated critical habitat.  To jeopardize the continued existence
of a listed species means "to engage in an action that reasonably would
be expected, directly or indirectly, to reduce appreciably the
likelihood of both the survival and recovery of a listed species in the
wild by reducing the reproduction, numbers, or distribution of the
species.  "50 C.F.R. 402.02”.

To facilitate compliance with the requirements of the Endangered Species
Act subsection (a)(2) the Environmental Protection Agency, Office of
Pesticide Programs has established procedures to evaluate whether a
proposed registration action may directly or indirectly reduce
appreciably the likelihood of both the survival and recovery of a listed
species in the wild by reducing the reproduction, numbers, or
distribution of any listed species (U.S. EPA 2004).  After the
Agency’s screening-level risk assessment is performed, if any of the
Agency’s Listed Species LOC Criteria are exceeded for either direct or
indirect effects, a determination is made to identify if any listed or
candidate species may co-occur in the area of the proposed pesticide
use.  If determined that listed or candidate species may be present in
the proposed use areas, further biological assessment is undertaken. 
The extent to which listed species may be at risk then determines the
need for the development of a more comprehensive consultation package as
required by the Endangered Species Act.

For certain use categories, the Agency assumes there will be minimal
environmental exposure, and only a minimal toxicity data set is required
(Overview of the Ecological Risk Assessment Process in the Office of
Pesticide Programs U.S. Environmental Protection Agency - Endangered and
Threatened Species Effects Determinations, 1/23/04, Appendix A, Section
IIB, pg.81).  Chemicals in these categories therefore do not undergo a
full screening-level risk assessment.

	This preliminary analysis indicates that there is a potential for
triclosan use to overlap with listed species and that a more refined
assessment is warranted, to include direct, indirect and habitat
effects.  The more refined assessment should involve clear delineation
of the action area associated with proposed use of triclosan and best
available information on the temporal and spatial co-location of listed
species with respect to the action area.  This analysis has not been
conducted for this assessment.  An endangered species effect
determination will not be made at this time.  

Confirmatory Data Required:

Freshwater invertebrate acute study (850.1010);

As outlined in the environmental fate chapter for triclosan, the
registrant is required to provide a scientific rationale, including
appropriate modeling (e.g., surface water modeling), that addresses and
quantifies the amounts of triclosan and triclosan transformation
products (e.g., triclosan methyl) occuring in various environmental
compartments (e.g., surface waters, biosolids, soil, fish, shellfish)
from triclosan antimicrobial pesticide uses;

Relative to the above requirement, if the registrant is not able to
provide a satisfactory scientific rationale that determines the
quantities of triclosan and triclosan transformation products in various
environmental compartments, then EPA will assume that the present levels
of triclosan and triclosan transformation products detected in such
compartments occurs because of registered antimicrobial use patterns. 
In this case, OPP will require the environmental fate data outlined in
the triclosan environmental fate chapter; and

Depending on the results of the environmental fate studies, which may be
required (see triclosan environmental fate chapter), additional acute
and chronic nontarget organism studies may be required.  These include
the following studies:

	a. Estuarine/marine fish acute study (850.1075) [Technical Grade Active
	Ingredient (TGAI)];

		b. Estuarine/marine shrimp acute study (850.1035) (TGAI);

	c. Estuarine/marine mollusk acute study (850.1025) (TGAI);

		d. Fish early life-stage (freshwater) study (850.1400) (TGAI);

		e. Aquatic invertebrate (freshwater) life-cycle study (850.1300)
(TGAI);

		f. Fish life-cycle study (850.1500);

		g. Fish bioconcentration study – BCF (850.1730) (TGAI);

		h. Acute sediment toxicity to freshwater invertebrates (850.1735)
(TGAI); 

		i. Acute sediment toxicity to estuarine invertebrates (850.1740)
(TGAI); 			and

			j. Additional plant toxicity testing:  an additional algal toxicity
test 					(850.5400) with the freshwater green alga, Selenastrum
capricornutum; 				and studies on the rooted freshwater macrophyte rice
(Oryza sativa) – 				850.4225 and 850.4250 (2 tests on seedling
emergence and vegetative 				vigor).

IV.	 Label Hazard Statements for Terrestrial and Aquatic Organisms:

Triclosan labels must state:  

“This pesticide is toxic to fish and aquatic invertebrates.”

"Do not discharge effluent containing this product into lakes, streams,
ponds, estuaries, oceans, or other waters unless in accordance with the
requirements of a National Pollutant Discharge Elimination System
(NPDES) permit and the permitting authorities are notified in writing
prior to discharge.  Do not discharge effluent containing this product
to sewer systems without previously notifying the local sewage treatment
plant authority.  For guidance contact your State Water Board or
Regional Office of the EPA."

V.  REFERENCES

41008910.  Terrell, Y.  1985.  Acute Oral Toxicity Study of Issue Plus
II; ID No. 88-472; Prepared by American Standards Biosciences Corp. for
Diversey Wyandotte Corporation, Wyandotte, Michigan.

41008911.  Terrell, Y.  1988.  Avian Dietary Quaily (Litmus Test) of
Issue Plus in Bobwhite Quail; Project No. 88-471; Prepared by American
Standard Biosciences Corp. for Diversey Wyandotte Corporation,
Wyandotte, Michigan.

41008912.  Terrell, Y.  1988.  The Acute Toxicity Bioassay of Issue Plus
on Rainbow Trout; Project No. 88-474; Prepared by American Standard
Biosciences Corp. for Diversey Wyandotte Corporation, Wyandotte,
Michigan.

41008913.  Terrell, Y.  1988.  The Acute Toxicity Bioassay of Issue Plus
on Bluegill Sunfish; Project No. 88-473; Prepared by American Standard
Biosciences Corp. for Diversey Wyandotte Corporation, Wyandotte,
Michigan.

41008914.  Terrell, Y.  1988.  Acute Toxicity of Issue Plus on Daphnia
magna; Project No. 88-475; Prepared by American Standard Biosciences
Corp. for Diversey Wyandotte Corporation, Wyandotte, Michigan.

42322101.  Boettcher, J.  1990.  Report on the Acute Toxicity (96h) of
FAT 80, 023/Q to Zebrafish.  Test No. G 069 04.  Prepared by Ciba-Geigy,
Ltd., D&C Product Ecotoxicology, Basel, Switzerland.  Submitted by
Ciba-Giegy Corporation, Greensboro, North Carolina.

42322102.  Wuethrich, V.  1990.  48-Hour Acute Toxicity of FAT 80, 023/Q
to Daphnia magna (OECD-Immobilization Test).  Project No. 262923. 
Prepared by RCC Umweltchemie AG, Itingen, Switzerland.  Submitted by
Ciba-Giegy Corporation, Greensboro, North Carolina.

43022602.  Pedersen, C.A. and B.R. Helsten.  1993.  Triclosan (IRGASAN
DP300(): 14-Day Acute Oral LD50 Study in Bobwhite Quail.  Study
performed by Bio-Life Associates, Ltd., Neillsville, Wisconsin. 
Laboratory Project No. 102-024-03.  Submitted by CIBA-GEIGY Corporation,
Greensboro, North Carolina.

43022603.  Pedersen, C.A. and B.R. Helsten.  1993.  Triclosan (IRGASAN
DP300(): 14-Day Acute Oral LD50 Study in Mallard Ducks.  Study performed
by Bio-Life Associates, Ltd., Neillsville, Wisconsin.  Laboratory
Project No. 102-023-04.  Submitted by CIBA-GEIGY Corporation,
Greensboro, North Carolina.

43022604.  Pedersen, C.A. and B.R. Helsten.  1993.  Triclosan (IRGASAN
DP300(): 8-Day Acute Dietary LC50 Study in Bobwhite Quail.  Study
performed by Bio-Life Associates, Ltd., Neillsville, Wisconsin. 
Laboratory Project No. 102-022-01.  Submitted by CIBA-GEIGY Corporation,
Greensboro, North Carolina.

43046001.  Bowman, J.H.  1990.  Acute Toxicity of D1063.01 (Triclosan:
Irgasan DP300) to Fathead Minnow (Pimephales promelas).  Laboratory
Project ID No. 38655.  Prepared by Analytical Bio-Chemistry
Laboratories, Inc, Columbia, Missouri.  Submitted jointly by Proctor and
Gamble Company and Ciba-Geigy Corp.

43046002.  Forbis, A.D. and J.G. Muckerman.  1990.  Acute Toxicity of
D1063.01 (Triclosan: Irgasan DP300) to Daphnia magna.  Laboratory
Project ID No. 38656.  Prepared by Analytical Bio-Chemistry
Laboratories, Inc, Columbia, Missouri.  Submitted jointly by Proctor and
Gamble Company and Ciba-Geigy Corp.

43740701.  Wuethrich, V.  1990.  Influence of FAT 80023/Q (Irgasan
DP300) on Reproduction of Daphnia magna.  Project No. 262934.  Prepared
by RCC Umweltchemie AG, Itingen, Switzerland.  Submitted by Ciba-Giegy
AG, Basel, Switzerland.

43969301.  Sword, M.C.  1996.  Static Acute Toxicity of Triclosan to
Rainbow Trout.  Study performed by ABC Laboratories, Inc., Columbia,
Missouri.  Laboratory Report No. 42997.  Sponsored by CIBA Chemical
Division, Greensboro, North Carolina.

44422801.  Staveley, J.P. and T.L. Williams.  1997.  Effects of
Triclosan on the Growth and Reproduction of Aquatic Plants.  Study
performed by Carolina Ecotox, Inc., Durham, North Carolina.  Laboratory
Report ID: 21-02-1.  Sponsored by Ciba-Geigy Corporation, Greensboro,
North Carolina.

Federle, T.W., Kaiser, S.K., and Nuck, B.A. 2002. Fate and Effects of
Triclosan in Activated Sludge.  Environmental Toxicology and
Chemistry/SETAC.  21(7): 1330-7.

Kanda, R., Griffin, P., and James, H.A., et al. 2003. Pharmaceutical and
Personal Care Products in Sewage Treatment Works.  Journal of
Environmental Monitoring.  5(5): 823-30.

Klopin, D.W., Furlong, E.T., Meyer, M.T., et al. 2002. Pharmaceuticals,
Hormones, and Other Organic Wastewater Contaminants in U.S. Streams,
1999-2000: A National Reconnaissance. Environmental Science and
Technology. 36(6): 1202-11.

McAvoy, D.C., Schatowitz, B., Martin, J., et al. 2002. Measurement Of
Triclosan In Wastewater Treatment Systems. Environmental Toxicology and
Chemistry. 21 (7): 1323-9.

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.

 The Agency is making this statement because triclosan and triclosan
transformation products are being detected in various environmental
components (see triclosan environmental fate chapter).

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