-'.~EO S1"-4~ V""" ~Q\ 

~ =u UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

~ Z WASHINGTON D.C., 20460 - w ]) (!J \ ; ~ f\{J 

~t PR01~v 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

December 15,2011 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

TO: 

Product Chemistry, Environmental Fate, and Ecological Effects Scoping 

Document in Support of Registration Review ofBis (trichloromethyl) 

sulfone (BTS). 

PC Code: 035601 DP Barcode: 394301 

Decision No.: 455121 Registration Nos.: See Table 1 

Petition No(s).: NA Regulatory Action: Ecological 

Environmental Scoping Document 

for Registration Review 

Risk Assessment Type: Single chemical Case No.: 2055 

TXRNo.:NA CAS No.: 3064-70-8 

MRID Nos.: See Table 3 & Pg. nos. 7, 40 CFR: None 

8,9, 10, 11, 12, & 13. 

." C ~ 

~ 

~ -

James 

Zoe 

rinivas 

Layton, 

Breithaupt, 

Gowda, 

Biologist 

MicrObiOIOg Agronomist 

~ 

~U"-.cL- N 6 -

11, 

I \ t; I 

'\ 

~ 

Risk Assessment and Sc e S pport Branch (RASSB) 

Antimicrobials Division 7510 ) 

v!1 v ' f 

t...,?'\ ~-- Nader Elkassabany, Branch C~ c::..- ~ . Donna Randall, Peer Reviewer ~ .' (JAA..y\a,...Q..O 

Risk 

Antimicrobials 

Assessment 

Division 

and Science 

(7510P) 

Support Branch ( ~ 

Mark Hartman, Branch Chief 

Lance Wormell, Team Leader 

Seiichi Murasaki, Chemical Review Manager 

Regulatory Management Branch II 

Antimicrobials Division (751 OP) 

Page 1 of40 
Page 2 of 40

Executive Summary

Bis (trichloromethyl) sulfone (BTS) is an organo-sulfur compound registered for use as 

an algicide, bactericide, slimicide and fungicide for use in industrial process and water systems 

such as pulp and papermill process water systems, recirculating cooling towers, and oil and gas 

field injection water systems;, and as a material preservative in paper additive system (nonfood 

contact) such as pastes and adhesive systems, polymers and latex emulsion systems, pigmented 

slurries, coating systems, in-container preservative for water-soluble and water dispersed 

adhesives and tackifiers, in-container preservative for water soluble and water dispersed 

construction and household products, manufacture and storage preservative for dispersed 

pigments; and as a fuel preservative. BTS was first registered in the United States in 1967 as a 

fungicide. A Reregistration Eligibility Decision (RED) for BTS was completed in September 

1996. Currently there are three companies that have nine active registrations. One of these 

products is registered as a technical with an active ingredient declaration of 98%, and two are 

manufacturing use products with active ingredient declarations of 35 and 39.2%. The remaining

six products are end-use products with active ingredient declarations of 3.3 to 20%; these 

products consist of soluble ready-to-use solutions and a flowable emulsifiable concentrate. All 

product chemistry data requirements have been satisfied for this active ingredient BTS.

At the time of the RED, risk assessments were not conducted for industrial microbiocides 

unless products had a once-through cooling water system use. To regulate these industrial 

microbiocide uses and associated risks to the aquatic environment, the Agency required that 

labels for BTS products require that discharges to aquatic environments comply with a National 

Pollutant Discharge Elimination System (NPDES) permit. As part of the registration review 

process, risk assessments for the pulp and papermill process water systems, recirculating cooling 

tower, and oil and gas field injection water systems will be conducted. For BTS applied to fuel, 

the types of BTS combustion products are expected to be essentially the same as those found 

from combustion of fuel alone, and at concentrations that would not be discernable from 

background level.

To conduct these assessments, the Agency data base for evaluating the environmental fate and 

transport of BTS is incomplete. The environmental fate data gaps for this pesticide include

activated sludge sorption isotherm, activated sludge respiration inhibition, and one of four waste 

biodegradability tests (ready biodegradability, porous pot test, or one of two simulation tests). 

The purpose of these tests is to address discharge of fluids from industrial process and water 

systems, paper additive systems, and oil and gas field water systems to waste water treatment 

facilities followed by release to receiving waters and/or direct release to receiving waters. The 

major route of dissipation of BTS in the environment is microbial degradation with an estimated 

half-life of <1 day in aquatic aerobic conditions and <0.5 days in aquatic anaerobic conditions. 

Two metabolites are pentachlorodimethylsulfone, found under anaerobic and aerobic conditions,

and hexachloroethane, found under anaerobic conditions. One aquatic dissipation study was 

submitted, which measured concentrations of BTS in paper mill effluent. The water going into 

the paper machine was treated at 484 ppb (0.484 ppm), with BTS concentrations of 34, 7-8, and 

2 ppb in machine effluent, water samples from the mill, and lagoon water, respectively. The 

degradate, pentachlorodimethylsulfone, ranged from 5-6 ppb in machine water, mill water, and 

lagoon water; hexachloroethane was not detected. 
Page 3 of 40

BTS is practically non-toxic to avian species on an acute oral and subacute dietary basis; 

slightly toxic to small mammals on an acute oral basis; very highly toxic to freshwater fish and 

estuarine/marine invertebrates. BTS was classified as highly toxic to freshwater invertebrates 

and marine fish, but this is based on supplemental data which is expected to greatly 

underestimate the toxicity of BTS. In order to perform an ecological risk assessment, including 

an endangered species assessment for all uses, the Agency anticipates requiring several effect 

studies. This list includes resubmittal of a number of acute aquatic studies (freshwater fish both 

cold water and warm water; freshwater daphnid; estuarine/marine fish) for the TGAI because 

BTS would not be stable under the static conditions these studies were conducted, and no 

analytical measurements were made to document actual exposure concentrations. While the very 

highly toxic classification under even under these serves for labeling issues, these results are not 

adequate for assessing risk. Additional TGAI studies include: an estuarine/marine crustacean 

acute study; a guideline algal toxicity (Tier II) study for a freshwater green alga, Selenastrum 

capricornutum, a freshwater diatom, Navicula pelliculosa, a marine diatom, Skeletonema 

costatum, and a cyanobacteria study using Anabaena flos-aqua; a guideline Lemna toxicity (Tier 

II) study; a freshwater fish early-life stage study; an aquatic freshwater invertebrate life-cycle 

study; and an activated sludge respiration inhibition test. Because of the short half-life of BTS, 

aquatic organisms may also be exposed to the major degradate pentachlorodimethylsulfone of 

which there is currently no effects data. To evaluate risk to total toxic residues of BTS, effects 

data with this degradate for the following is required: a freshwater acute invertebrate study; a 

marine/estuarine crustacean and a mollusk acute study; a freshwater fish acute study; an 

estuarine/marine invertebrate life cycle study; a freshwater early life stage study; an algae (Tier 

II) study using only the most sensitive of the TGAI algae species; a guideline Lemna (Tier II) 

study; a seedling emergence (Tier II) test using rice; and an activated sludge respiration 

inhibition study.
Page 4 of 40

Introduction

BTS was first registered in the U.S. in 1967 as a fungicide. BTS is registered for use as 

an algicide, bactericide, slimicide and fungicide in industrial process and water systems such as 

pulp and papermill process water systems, recirculating cooling towers, secondary oil-recovery 

injection water systems, evaporative-condenser water systems, heat exchanger systems, and as a 

material preservative in adhesives, latexes, construction products and household products (such 

as caulking materials, mastics, ceramic, glazes, concrete, concrete admixtures, plasters etc.), 

dispersed pigment preservative, paints coatings and stains, paper coating preservation, photo 

processing system preservation, polymer latex preservation, and fuel preservation. Currently nine 

products are registered for the uses indicated above which are listed in Table 1. A Reregistration 

Eligibility Decision (RED) was issued by EPA for bis(trichloromethyl) sulfone in September 

19951

.

Table 1. Registered Products of Bis(trichloromethyl) sulfone

Registration

# Registration Name Company Name

Formulation

Type

% of Active 

Ingredient

1706-177 Nalcon® 7642 Nalco Company Ready-to-Use Solution 3.33

67869-14 N-1386 Technical Verichem, Inc. Technical Chemical 98

67869-15 N-1386 Hexylene Glycol Verichem, Inc. Formulation 

Intermediate 35

67869-16 N-1386 Naptha Han Verichem, Inc. Manufacturing Use 

Product 39.2

67869-32 N-1386 PEG-EU 20 Verichem, Inc. Emulsifiable Conc. 20

74655-3 Spectrum RX-36 Hercules 

Incorporated Ready-to-Use Solution 20

74655-6 Spectrum RX-38 Hercules 

Incorporated Ready-to-Use Solution 17

74655-10 Spectrum RX-65 Hercules 

Incorporated Ready-to-Use Solution 18

74655-15 Spectrum RX-10 Hercules 

Incorporated Ready-to-Use Solution 5.3

The Agency has conducted a review of the available product chemistry, environmental 

fate, and ecotoxicity data for BTS. The primary source of information for this assessment was 

the 1995 bis(trichloromethyl) sulfone RED. The findings are summarized below.

 1

http:/www.epa.gov/oppsrrd1/REDs/2055red.pdf
Page 5 of 40

A. Product Chemistry Summary of Bis(trichloromethyl)sulfone (98-100% TGAI)

Common Name: Bis(trichloromethyl) sulfone

Chemical Name: Hexachlorodimethyl sulfone

Sulfonyl bis(trichloromethane)

Trade and Other Names: N-1386®

OPP Chemical Code: 35601

CAS Registry Number: 3064-70-8

Molecular Formula: C2 Cl6 O2S

Molecular weight: 301 g/mole

Molecular Structure:

Color: White to Off-white Crystal

Physical State: Solid (Crystals) at 25°C

Odor: Pungent aromatic odor

Stability: Relatively stable at room temperature 25°C. Does not react 

with steel or iron.

Oxidation/Reduction: Not required. Product does not contain any oxidizing or 

reducing agents.

Flammability: Not required for products which do not contain combustible 

liquids.

Explodability: Not required. Contains no explosive ingredients.

Storage Stability: Ave. % w/w A.I.

Initial: 99.2

After 3 months: 99.0

After 6 months: 99.2

After 1 year: 99.2

Miscibility: Not required. Product is not an emulsifiable liquid and is 

not intended to be diluted with petroleum solvents.
Page 6 of 40

Corrosion Characteristics: No degradation or deterioration of the packaging (55-

gallon, epoxy lined steel drum) was observed during or 

after the one-year storage at room temperature.

A laboratory immersion testing for corrosivity showed 

product to be corrosive to stainless steel and cold rolled 

steel. Coupons of fiber glass HDPE, LOPE, cross-linked 

HDPE and polystyrene were not affected by the product.

Dielectric breakdown

voltage: Not required for products not intended to be used around 

electrical equipment.

pH: Not Applicable for solids.

UV/Visible absorption: Not Reported.

Viscosity: Not applicable for solid products.

Melting point: 36-38 °C.

Boiling Point: Not applicable for solids.

Density: 2.00 g/ml at 20°C.

Dissociation Constant: Not applicable. TGAI Does not dissociate in water.

Log Ko/w: 3.3

Solubilities: Water: 70 ppm by weight at 20-22°C

Essentially insoluble in water.

Ethylene glycol: 6.2% by weight

Dimethyl sulfoxide: 90.0% by weight at 70°F/25°C

82.0% by weight at 48°F/9°C

75.0% by weight at 67°F/20°C

Acetonitrile: 93.0% by weight at 67°F/20°C

86.0% by weight at 50°F/10°C

81.0% by weight at 41°F/5°C

Vapor Pressure: 0.00108 mm Hg at 25°C (Source: EPI Suite)

Henry's Law Constant: 1.19E-008 atm-m3

/mole (Source: EPI Suite)

Enforcement Analytical

Method: Gas Chromatograph GC/MS
Page 7 of 40

All product chemistry data requirements have been satisfied for the active 

ingredients BTS. (Source: MRIDs 152324, 152327, 156932, 162129, 42384501, 

42413301, 45614801, 41888602, 456311-01, and 92010003).

B. Environmental Fate Summary

No environmental fate assessment was performed for BTS at the time of the registration. 

Available environmental fate guideline studies and the results are summarized below.

The Agency's conclusions for the degradation, metabolism, mobility, and dissipation 

studies are as follows.

1. Degradation Studies (Abiotic)

a. Hydrolysis (161-1)

BTS did not hydrolyze in sterile aqueous buffered solutions at pH 4, 7, or 9 when 

incubated at 25°C. The study is classified as acceptable (MRID # 418887-01).

b. Photodegradation in water (161-2)

BTS photodegraded when irradiated with a non-specified sunlamp at pH 7 at 

25°C degraded to bicarbonate, chloride, and sulfate ions. Photodegradation 

half-lives were 39 days in water and 6 days in water sensitized with 1% acetone. 

The study is classified as supplemental (MRID #s 00156819, 00156935).

c. Combustion in fuel

No study has been conducted to identify the types and exact amounts of 

combustion products of BTS that would occur when fuel, with BTS added is 

burned. However, the combustion by-products of BTS that are likely to form 

when burned with hydrocarbon fuels is listed in the following table. This list is 

by no means complete but provides the ones most likely to form in the greatest 

quantities, and be released to the atmosphere. The active ingredient can extract 

hydrogen from the hydrocarbon fuel to form some of these by-products; this can 

commonly occur in such systems. Quantities provided are estimates for the 

highest label application rate and assumes that 100% of the BTS is converted to 

the designated by-product. The highest label application rate is 1.5 gallons of 

the formulation (20% a.i.; EPA Registration # 67869-32) in 10,000 gallons of 

fuel, which occurs under the worst conditions (system is really fouled), this 

translates to 30 ppm

2

 2 150 gallons of formulation per 1,000,000 gallons x 0.2 a.i. fraction of formulation = 30 parts per million

of the active in fuel. The levels of sulfur and chlorine 

added are within background levels found in crude oils (see the following 

paragraph), and a majority of the chlorine in fossil fuels is expected to be 

released predominately as hydrogen chloride (HCl) and chloromethane (CH3Cl) 

(McCulloch et al. 1999; MDNR 1999).
Page 8 of 40

Table 2. Possible Combustion By-Products of BTS in Fuel

Combustion By-Products of BTS Air Emission Levels per

gallon of fuel

Hexachloroethane (C2Cl6) 30 ppm

Chloroform (CHCl3) 30 ppm

Dichloromethane (CH2Cl) 30 ppm

Sulfur oxides, could be SO2 or SO3 30 ppm each

Hydrochloric acid (6 HCl) 180 ppm

Thionyl chloride (SO2Cl) 30 ppm

Sulfur is a natural occurring element in crude oil with reported content in 

domestic and foreign crude oil ranging from <100 ppm to >20,000 ppm (BLM 

1975). The average monthly sulfur content of crude oil in the United States in 

2011 ranged from 0.57% (5700 ppm) to 2.28% (22,800 ppm)3

. An average 

crude oil contains 1-3% (10,000 – 30,000 ppm) sulfur4

. The level of sulfur that 

would be added by BTS is within background levels of crude oil. Sulfur content 

of processed fuel oils will differ based on the origin of the crude oil and the 

extent upon the methods of refining. For example, in a 1999 MDNR review of 

sulfur and chloride content of fuel oils for boilers, the reported sulfur content for 

No. 2 oil and low sulfur No. 6 oil is around 0.41% (4100 ppm) and 0.49% (4900 

ppm), respectively, No. 5 oil contained 1.42% (14,200 ppm), and high sulfur 

No. 6 oil contained 1.66% (16,600 ppm) (MDNR, 1999). The sulfur content of 

fuel oils is regulated in some cases such as diesel fuel which has standards 

ranging from 15 ppm (ultra low) sulfur content upto 1000 ppm5

; special 

processing is needed to obtain the ultra low sulfur content fuels.

In the 1999 MDNR review of the sulfur and chlorine (reported as chloride)

content of fuel oils for boilers, No. 2, No. 5, and No. 6 fuel oil contained 

between 0.02% (200 ppm) and 0.05% (500 ppm) chlorine (MDNR, 1999). 

2. Metabolism Studies (Biotic)

a. Anaerobic Aquatic Metabolism (162-3)

An anaerobic aquatic metabolism study conducted with a sandy loam sediment 

and pond water shows that the major route of dissipation of BTS is rapid 

microbial degradation with an estimated half-life of <0.5 days. The metabolite 

pentachlorodimethyl sulfone was minor (<10 % of applied parent compound, 

but hexachloroethane reached 76.3 % of applied by 14 days and degraded to 

53% by the end of the study (9 months). The study is classified as acceptable

(MRID # 403171-01). 

 3 http://205.254.135.7/dnav/pet/pet_pnp_crq_a_EPC0_YCS_pct_m.htm Website accessed 12/14/2011 4 http://www.osha.gov/dts/osta/otm/otm_iv/otm_iv_2.html

5 http://www.epa.gov/otaq/fuels/dieselfuels/index.htm
Page 9 of 40

b. Aerobic Aquatic Metabolism (162-4)

The calculated aerobic aquatic metabolism half-life of parent is 0.7 days. The 

carbon-14-labeled (

14C-labeled) residue mass balance accountability had a mean 

of 97.9% based on initial concentration for the month long study. Extractability 

decreased from approximately 80% at day 0 to 28% at 1 month. Test water 

residues increased from approximately 11% at day 0 to 46% at 1 month. There 

was no significant change in non-extractable residues as a percent of initial 

concentration. Liquid scintillation analysis of trapping solutions shows that 14Cvolatiles accounted for a mean of less than 4% of mass balance accountability. 

The degradates pentachlorodimethyl sulfone and hexachloroethane were formed 

in significant (>10%) quantities. Pentachlorodimethyl sulfone was 1.5 μg/g at 

the beginning of the study, increased to 4.4 μg/g (100 % of parent compound) 

by 14 days, and decreased to non-detectable concentrations by 7-14 days. 

Hexachloroethane was first detected at 7 days, and varied between 2.4 and 3.6 

μg/g (55-82 % of applied parent compound) until 21 days. The study is 

classified as acceptable (MRID # 401932-03).

3. Mobility Studies

a. Leaching/adsorption/desorption (163-1)

In a leaching adsorption/desorption study, Freundlich Kads values from five 

(autoclaved) U.S. soils ranged from 6-52 mL/g, which indicates low mobility. 

The study is classified as acceptable (MRID #s 00156936, 00162362).

4. Dissipation Study

a. Aquatic Field Dissipation Study (164-2)

One aquatic dissipation study was submitted. This study followed the dissipation 

of bis (trichloromethyl) sulfone in a pulp/paper mill from paper machine water, to 

mill water, and further to lagoon water that was then released to a stream. The 

water going into the paper machine was treated at 4.84 x 102 ppb (0.484 ppm) bis 

(trichloromethyl) sulfone. Effluent from the machine contained 34 ppb, water 

samples from the mill contained 7-8 ppb, and lagoon water contained 2 ppb bis 

(trichloromethyl) sulfone. One degradate, pentachlorodimethyl sulfone, ranged 

from 5-6 ppb in machine water, mill water, and lagoon water. The second 

degradate, which was referred to as a hydrolysis product, hexachloroethane, was 

not recovered from any of the samples during the study (MRID # 403171-03).

In summary, the registrant has submitted an acceptable hydrolysis study, and an 

acceptable anaerobic aquatic metabolism study (hydrolysis, MRID # 418887-01; anaerobic 

aquatic metabolism, 403171-01; aerobic aquatic metabolism study, MRID # 401932-03) and 

other studies which are considered to be supplemental that adequately describe the 
Page 10 of 40

environmental fate of BTS and its major degradates. BTS is stable to hydrolysis, but degrades 

by photodegradation in water with half-lives of 39 days (corrected) and 6 days (uncorrected) for 

non-sensitized and sensitized solutions, respectively (MRID #s 00156819, 00156935). An 

anaerobic aquatic metabolism study (MRID 403171-01) conducted with a sandy loam sediment 

and pond water shows that the major route of dissipation of BTS is microbial degradation with 

an estimated half-life of <0.5 days. Two metabolites are pentachlorodimethyl sulfone and 

hexachloroethane. One aquatic dissipation study (MRID 403171-03) was submitted, which 

measured concentrations of BTS in paper mill effluent. The water going into the paper machine 

was treated at 484 ppb (0.484 ppm), with effluent from the machine containing 34 ppb, water 

samples from the mill containing 7-8 ppb, and lagoon water containing 2 ppb BTS. One 

degradate, pentachlorodimethyl sulfone, ranged from 5-6 ppb in machine water, mill water, and 

lagoon water. The second degradate, which was referred to as a hydrolysis product, 

hexachloroethane, was not recovered from any of the samples during the study.

In a leaching adsorption/desorption study, Freundlich K ads values from five 

(autoclaved) U.S. soils ranged from 6-52 mL/g, which indicates relatively low to low mobility 

in tested soils (MRID #s 00156936, 00162362).

At this time, the Agency did not conduct an environmental fate assessment for the 

material preservatives and industrial process and water systems uses of BTS because of lack of 

data on those studies listed on page 11 of this document. Once these studies are submitted, the 

Agency will then assess the fate and transport of BTS from the uses that create waste products 

that may pass through waste water treatment plants (WWTPs) and be discharged into terrestrial 

and aquatic environments. These uses include material preservatives and industrial slimicides 

used in recirculating water cooling towers and pulp and paper mills.

Water Quality

BTS is not identified as a cause of impairment for any water bodies listed as impaired 

under section 303(d) of the Clean Water Act, based on information provided at the Agency’s 

National Pesticides Cause of Impairment of Waters website (searched April 7, 2011)6. In 

addition, no Total Maximum Daily Loads (TMDLs) have been developed for BTS, based on 

information provided at the Agency’s National Pesticide TMDL web site (searched April 7, 

2011)7. More information on impaired water bodies and TMDLs can be found at 

http://www.epa.gov/owow/tmdl/. The Agency invites submission of water quality data for this 

pesticide. To the extent possible, data should conform to the quality standards in Appendix A of 

the OPP Standard Operating Procedure: Inclusion of Impaired Water Body and Other Water 

Quality Data in OPP’s Registration Review Risk Assessment and Management Process (see: 

http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1-sop.pdf ), in order to ensure 

they can be used quantitatively or qualitatively in pesticide risk assessments.

 6 . http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885 7

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_

group_name=PESTICIDES
Page 11 of 40

C. Ecological Effects Summary

No quantitative ecological risk assessment was performed for BTS at the time of the 

registration. Available ecotoxicity guideline studies and the results are summarized in Table 3. 

The Agency's conclusions for the terrestrial and aquatic effects studies are as follows.

a. Toxicity to Terrestrial Animals

Birds, Acute and Subacute

In order to establish the toxicity of BTS to birds, the following tests are required 

for industrial microbiocides using the technical grade material: one avian singledose oral (LD50) study on one species (preferably the bobwhite quail or mallard 

duck) and one subacute dietary study on one species (preferably the bobwhite 

quail). These studies have been submitted and their results are presented in Table 

3. These results indicate that BTS is practically non-toxic to avian species on an 

acute oral and subacute dietary basis. The acute oral study contained overt signs 

of toxicity at the highest dose tested. The guideline requirements are fulfilled 

(MRID #’s 156817, 156818, and 156820).

Toxicity to Mammals

Wild mammal testing is required on a case-by-case basis, depending on the results 

of the lower tier studies such as acute and subacute testing, intended use pattern, 

and pertinent environmental fate characteristics. In most cases, however, an acute 

oral LD50 from an acute oral toxicity study is used to determine toxicity to 

mammals. The acute LD50 for rats (small mammal surrogate), discussed in the 

Human Health Assessment, was determined to be 535 mg/kg (MRID #152875). 

This result indicates that BTS is slightly toxic to small mammals on an acute oral 

basis.

b. Toxicity to Aquatic Animals

1. Freshwater Fish 

In order to establish the toxicity of BTS to freshwater fish, the minimum data 

required on the technical grade of the active ingredient for discharge to receiving 

waters is one warm water fish toxicity study and one cold water fish toxicity 

study. The preferable cold water species is rainbow trout and the preferable warm 

water species is the bluegill sunfish. Two studies were found in the files, but both 

of these studies provide only supplemental information8

 8 These studies were originally classified as acceptable, but the issues of stability were not noted or discussed. 

These studies were downgraded to supplemental because the studies do not document the stability and fate 

information indicates that stability was not likely. These results are expected to greatly underestimate the acute 

sensitivity of BTS to fish.

. The studies are 

conducted under static conditions and no analytical measurements were made of 
Page 12 of 40

for the test substance. Given that the aquatic aerobic half-life of BTS is <1 day, 

the parent was not likely stable under test conditions. To maintain stable 

exposure concentrations given the expected half-life, the tests should have been 

conducted under flow-through conditions and analytical measurements made at a 

frequency and timing to document stability throughout the study duration. The 

results of these supplemental studies are listed in Table 3 and they are expected to 

greatly underestimate the acute sensitivity of BTS to fish; however, they still 

indicate that BTS can be expected to be very highly toxic to both cold and warm 

water fish. The data requirements are not fulfilled (MRID #s 156814 and 

156815).

To establish the toxicity of the major degradate, pentachlorodimethylsulfone, to 

freshwater fish, one fish acute toxicity study using the most sensitive TGAI 

species is required. No acute fish toxicity data for this degradate is available. 

The data requirement for the major degradate, pentachlorodimethylsulfone, is not 

fulfilled.

No chronic data is available for either BTS or its major degradate with freshwater 

fish. Because uses of BTS will result in repeated discharge of the antimicrobial 

and its major degradate, pentachlorodimethyl-sulfone, to aquatic environment a 

fish early life stage test with TGAI BTS and a test with the degradate is required. 

There should be an acute toxicity test available for the same species for each of 

these.

2. Freshwater Invertebrates

The minimal testing required establishing the acute toxicity of a microbiocide to 

freshwater invertebrates is a freshwater aquatic invertebrate toxicity test, 

preferably using first instar Daphnia magna or early instar amphipods, stoneflies, 

mayflies, or midges. One study was found in the files, but the study provides only 

supplemental information9

. The study was conducted under static conditions and 

no analytical measurements were made of for the test substance. Given that the 

aquatic aerobic half-life of BTS is <1 day, the parent was not likely stable under 

test conditions. To maintain stable exposure concentrations given the expected 

half-life, the test should have been conducted under at least renewal conditions 

and analytical measurements made at a frequency and timing to document 

stability throughout the study duration. The classification of BTS as highly toxic 

to aquatic invertebrates (Table 3) based on the supplemental information is likely

an underestimate of the sensitivity of BTS to freshwater invertebrates. The 

guideline requirement is not fulfilled (MRID #156816).

 9 The study was originally classified as acceptable, but the issues of stability were not noted or discussed. The study 

was downgraded to supplemental because it does not document the stability and fate information indicates that 

stability was not likely. These results are expected to greatly underestimate the acute sensitivity of BTS to 

freshwater invertebrates.
Page 13 of 40

To establish the toxicity of the major degradate, pentachlorodimethylsulfone, to 

freshwater invertebrates, one freshwater invertebrate acute toxicity study using 

the same TGAI tested species is required. No acute freshwater invertebrate 

toxicity data for this degradate, pentachlorodimethylsulfone, is available.

No chronic data is available for either BTS or its major degradate with freshwater 

invertebrates. Because uses of BTS will result in repeated discharge of the 

antimicrobial and its major degradate, pentachlorodimethyl-sulfone, to aquatic 

environment a life cycle test with TGAI BTS and a life cycle test with the 

degradate is required. 

3. Estuarine and Marine Animals

For uses where the antimicrobial is expected to reach estuarine or marine 

environments, one estuarine/marine acute fish toxicity study, one acute crustacean 

toxicity study, and one mollusk study are required. One sheepshead minnow 

study was found in the files, but the study provides only supplemental 

information10. The study was conducted under static conditions and no analytical 

measurements were made of for the test substance. Given that the aquatic aerobic 

half-life of BTS is <1 day, the parent was not likely stable under test conditions. 

To maintain stable exposure concentrations given the expected half-life, the test 

should have been conducted under flow through conditions and analytical 

measurements made at a frequency and timing to document stability throughout 

the study duration. One mollusk embryo larvae study was found in the files, and 

is acceptable; while the study was conducted under static conditions the mollusk 

embryo larvae guideline study is a static exposure test because of life stage 

handling limitations. No acute estuarine/marine crustacean study was found. 

Based on the embryo larvae mollusk study, BTS is classified as very highly toxic 

to marine/estuarine mollusks. The classification of BTS as only high toxic to 

estuarine/marine fish based on the supplemental information is potentially an 

underestimate of the sensitivity of BTS to estuarine/marine fish. The guideline 

requirement is fulfilled for the marine mollusk (MRID # 40193201) but is not 

fulfilled for the estuarine/marine fish (MRID # 40193201) or crustacean.

No acute estuarine/marine fish or invertebrate toxicity data for this degradate, 

pentachlorodimethylsulfone, is available. To establish the toxicity of the major 

degradate, pentachlorodimethylsulfone, which is also expected to reach estuarine 

or marine environments from discharge of waste waters, a mollusk embryo larvae 

study, the most sensitive test and species as indicated by the supplemental data, is 

required. A chronic test with a crustacean species is also required (see paragraph 

below) and to be able to calculate an acute-to-chronic ratio for this species, an 

acute test with the mysid is also required. Data on an estuarine/marine fish using 

 10 The study was originally classified as acceptable, but the issues of stability were not noted or discussed. The 

study was downgraded to supplemental because it does not document the stability and fate information indicates that 

stability was not likely. These results are expected to greatly underestimate the acute sensitivity of BTS to 

estuarine/marine fish.
Page 14 of 40

the same species as that tested with the TGAI is also desired. However, in the 

absence of such data, factors derived from a comparison of TGAI and 

pentachlorodimethylsulfone for freshwater fish and crustacean data will be 

applied. As the mode of action for mollusks may differ from that of the fish and 

crustaceans, there would be a high level of uncertainty in the application of a 

factor derived from a fish or crustacean to mollusks.

No chronic data is available for either BTS or its major degradate with 

estuarine/marine fish or invertebrates. Because uses of BTS will result in 

repeated discharge of the antimicrobial and its major degradate, pentachlorodimethylsulfone, to aquatic environment, chronic exposure has the potential to 

occur. A mysid life cycle test with the major degradate, pentachlorodimethylsulfone is required. This data would allow confirmation that the acuteto-chronic ratio does not differ between saltwater and freshwater organisms (i.e., 

indication that mode of action does not differ greatly between saltwater and 

freshwater species) for the degradate. Additionally a fish early life stage test 

(using the same fish species as used in acute testing) is desired for both BTS and 

its major degradate pentachlorodimethylsulfone and an invertebrate (crustacean) 

life cycle test (using the same species used in the acute test) with BTS is desired. 

If these desired BTS and degradate fish early life stage and a BTS invertebrate life 

cycle test are not submitted the acute-to-chronic ratios derived from freshwater 

species will be applied.

c. Toxicity to Aquatic Plants

Algae

No algal toxicity data have been submitted for either BTS or its major degradate 

pentachlorodimethylsulfone. For the ecological risk assessment, including an 

endangered species assessment for all uses, the Agency anticipates needing the 

algal toxicity data for BTS with four species: a green alga, a freshwater diatom, a 

saltwater diatom, and a cyanobacterium. For the major degradate, 

pentachlorodimethylsulfone, a test with the most sensitive of these is required.

Vascular, Nonrooted

No toxicity testing with an aquatic vascular Lemna sp. has been submitted for 

either BTS or its major degradate pentachlorodimethylsulfone. One test with the 

TGAI and one test with the major degradate pentachlorodimethylsulfone are 

required.
Page 15 of 40

Vascular Emergent Rooted Plants

No seedling emergence and growth test for BTS or its major degradate is 

available. For uses where the antimicrobial is expected to reach aquatic 

environments, a seedling emergence and growth study with rice is required. 

Because of the rapid degradation of BTS in the environment, the major degradate 

pentachlorodimethylsulfone is required.

Table 3. Ecotoxicity Data Summary for Bis (trichloromethyl) sulfone

Guideline 

Number*

Common Name/

Taxonomic Name

Test

Type % a.i. Study Duration

Dose 

Type

Toxicity MRID No./

Study 

Classification/

Comments

Toxicity

Classification Value Units

Avian Acute Oral Toxicity

850.2100 

(71-1)

Mallard duck/

Anas platyrhynchos O Tech 14 days LD50 >2250 mg/kg-bw 00156817/Acceptable/

practically 

non-toxic

Avian Subacute Dietary Toxicity

850.2200 

(71-2b)

Mallard duck/

Anas platyrhynchos D Tech 8 days LC50 >5000 ppm

00156820/

Acceptable/

Overt signs of 

toxicity were 

observed at the 

highest 

concentration 

tested (5000 

ppm)

practically 

non-toxic

850.2200 

(71-2a)

Bobwhite quail/

Colinus virginianus

D Tech 8 days LC50 >5620 ppm

00156818/

Acceptable

practically 

non-toxic

Freshwater Fish Acute Toxicity

72-1 Rainbow trout/

Oncorhynchus mykiss S 99** 96 hr LC50 29 ppb 00156814/Supplemental/

very highly 

toxic

72-1 Bluegill sunfish/

Lepomis macrochirus S 99** 96 hr LC50 58 ppb 00156815/Supplemental

very highly 

toxic

Freshwater Invertebrate Acute Toxicity

72-2 Water flea/

Daphnia magna S 99** 48 hr EC50 173 ppb 00156816/Supplemental highly toxic

Estuarine/Marine Acute Toxicity

850.1055 

(72-3b)

Embryo 

larvae 

study

Quahog clam/

Mercenaria mercenaria S 99.9 48 hr EC50 9.2 ppb 40193201/

Acceptable

very highly 

toxic

72-3 Sheepshead minnow/

Cyprinodon variegatus S 99 96 hr LC50 400 ppb 40138102/Supplemental highly toxic

Test Type—O: oral; D: dietary; S: static.

Toxicity Units—mg/kg-bw: milligrams per kilogram-body weight; ppm: parts per million (equivalent to milligrams per kilogram-diet (mg/kgdiet) for dietary exposure and milligrams per liter (mg/L) for aquatic organisms); ppb: parts per billion (equivalent to micrograms per liter (μg/L) 

for aquatic organisms.

Categories of acute toxicity for aquatic organisms (U.S. EPA, 2004) based on EC50 or LC50 (mg/L): < 0.1 very highly toxic; 0.1-1 highly toxic; 
Page 16 of 40

Guideline 

Number*

Common Name/

Taxonomic Name

Test

Type % a.i. Study Duration

Dose 

Type

Toxicity MRID No./

Study 

Classification/

Comments

Toxicity

Classification Value Units

>1-10 moderately toxic; >10-100 slightly toxic; >100 practically nontoxic.

Categories of acute toxicity to terrestrial animals, avian and mammalian (U.S. EPA, 2004). LC50 (ppm): < 50 very highly toxic; 50 - 500 

highly toxic; 501 – 1000 moderately toxic; 1001-5000 slightly toxic; >5000 practically non-toxic. LD50 (mg/kg-bw): < 10 very highly toxic; 10 -

50 highly toxic; 51 - 500 moderately toxic; 501-2000 slightly toxic; >2000 practically non-toxic.

*Brackets indicate the test guideline that the study was conducted under; the non-brackets identify the current test guideline.

**The % a.i. in the test substance was not given but the same compound (N-1386) was analyzed in an acute mysid shrimp study and found to 

contain 99% a.i.

Adverse Ecological Incidents

There are no reported incidents in the Agency's Ecological Incident Information System 

(EIIS) regarding BTS. The absence of documented incidents does not necessarily mean that 

such incidents did not occur.

Ecological Effects Risk Assessment

An ecological risk assessment was not conducted previously on BTS’s use patterns 

described in this document. BTS’s uses that have potential for environmental exposure are 

discharges from industrial processes and water systems, specifically: use in pulp and papermill 

process water systems, recirculating cooling towers, and secondary oil-recovery injection water 

systems, and as a preservative in adhesives. The Agency needs to conduct environmental fate 

and ecological risk assessments for uses that potentially pass through waste water treatment 

plants (WWTPs) and may be discharged into terrestrial and aquatic environments. For this 

ecological risk assessment, including an endangered species assessment for all uses, the Agency 

anticipates needing the ecotoxicity data outlined on pages 17 and 18 of this document.

The Agency has not conducted previously an ecological risk assessment for BTS that 

supports a complete endangered species effects determination. The ecological risk assessment 

planned during registration review will allow the Agency to determine whether BTS uses have 

“no effect or “may affect” federally listed threatened or endangered species (listed species) or 

their designed critical habitats. When an assessment concludes that a pesticide’s use “may affect” 

a listed species or its designated critical habitat, the Agency will consult with the U.S. Fish and 

Wildlife Service and/or National Marine Fisheries Services (the Services), as appropriate.

Environmental Fate and Ecotoxicity Data Gaps and Anticipated Work

The Agency needs to conduct environmental fate and ecological risk assessments for 

material preservatives and industrial slimicides used in recirculating water cooling towers, pulp 

and paper mills, and oil and gas well development water systems that potentially pass through 

waste water treatment plants (WWTPs) and may be discharged into terrestrial and aquatic 

environments. Therefore, the Agency anticipates needing the proposed environmental fate and 

ecotoxicity data for BTS and/or any of its major degradation products that are of potential 

concern for all registered uses of BTS. The following environmental fate and ecotoxicity data 

are needed to conduct an environmental fate and ecological risk assessment:
Page 17 of 40

• The Agency anticipates needing the following data to conduct a complete 

environmental fate assessment for pulp and papermill process water system, 

recirculating cooling tower uses, and oil and gas well development water systems:

o Activated Sludge Sorption Isotherm—TGAI (GLN 835.1110);

o Activated Sludge Sorption Isotherm—major degradate, pentachlorodimethylsulfone (GLN 835.1110);

o Ready biodegradability (GLN 835.3110), Porous Pot Test (GLN 835.3220), or 

Simulation Tests to Assess the Biodegradability of Chemicals Discharged to 

Wastewater (GLN 835.3280), or Simulation Test-Aerobic Sewage Treatment: 

A. Activated Sludge Units—TGAI (GLN 835.3240) 11

o Ready biodegradability (GLN 835.3110), Porous Pot Test (GLN 835.3220), or 

Simulation Tests to Assess the Biodegradability of Chemicals Discharged to 

Wastewater (GLN 835.3280), or Simulation Test-Aerobic Sewage Treatment: 

A. Activated Sludge Units— major degradate pentachlorodimethyl-sulfone 

(GLN 835.3240) 4.

; and

• The Agency anticipates needing the following ecotoxicity data in order to conduct a 

complete ecological risk assessment, including an endangered species assessment:

o Freshwater invertebrate acute toxicity, Daphnia magna—TGAI (GLN 

850.1010);

o Freshwater invertebrate acute toxicity, Daphnia magna—major degradate, 

pentachlorodimethylsulfone (GLN 850.1010);

o Estuarine/marine invertebrate acute toxicity—TGAI (GLN 850.1035);

o Estuarine/marine invertebrate acute toxicity— major degradate, pentachlorodimethylsulfone (GLN 850.1035);

o Embyro larvae study using Mercenaria mercenaria—major degradate, pentachlorodimethylsulfone (GLN 850.1055);

o Freshwater fish acute toxicity, coldwater species—TGAI (GLN 850.1075);

o Freshwater fish acute toxicity, warmwater species—TGAI (GLN 850.1075);

o Freshwater fish acute toxicity, most TGAI sensitive species—major 

degradate, pentachlorodimethylsulfone (GLN 850.1075);

o Aquatic invertebrate life-cycle, freshwater Daphnia magna—TGAI (GLN 

850.1300);

o Aquatic invertebrate life-cycle, freshwater Daphnia magna—major degradate, 

pentachlorodimethylsulfone (GLN 850.1300);

 11 The results of the Activated Sludge Respiration Inhibition Test (ASRI) determine which of these three 

biodegradation tests are required. If the ASRI test EC50 is less than or equal to 20 mg/L, then either the (i) 

Biodegradation in Activated Sludge Study or (ii) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge 

Units or (iii) the Porous Pot Test is required. If the ASRI test EC50 is greater than 20 mg/L, then the applicant must 

choose either: (i) Ready Biodegradability or (ii) a) Biodegradation in Activated Sludge or b) Simulation Test –

Aerobic Sewage Treatment: A. Activated Sludge Units or c) the Porous Pot Test. If the Ready Biodegradability 

study is conducted and the test substance passes, then no further testing is required. If, however, the test substance

fails the Ready Biodegradability study, then the (i) Biodegradation in Activated Sludge or (ii) Simulation Test –

Aerobic Sewage Treatment: A. Activated Sludge Units, or (iii) the Porous Pot study is required.
Page 18 of 40

o Aquatic invertebrate life-cycle, saltwater Americamysis bahia—major 

degradate, pentachlorodimethylsulfone (GLN 850.1350);

o Fish early-life stage toxicity test, freshwater species with the most sensitive 

TGAI acute species—TGAI (GLN 850.1400); 

o Fish early-life stage toxicity test, freshwater species with the same species 

acute toxicity testing was conducted—major degradate, pentachlorodimethylsulfone (GLN 850.1400); 

o Seedling emergence (Tier II) with rice—major degradate, pentachlorodimethylsulfone (GLN 850.4225);

o Aquatic plant toxicity test using Lemna spp.—TGAI (GLN 850.4400);

o Aquatic plant toxicity test using Lemna spp.— major degradate, 

pentachlorodimethylsulfone (GLN 850.4400);

o Algal toxicity (Tier II) for a freshwater green alga, Selenastrum 

capricornutum; for a freshwater diatom, Navicula pelliculosa, for a marine 

diatom, Skeletonema costatum, and for the cyanobacteria species Anabaena 

flos-aquae—TGAI (GLN 850.5400);

o Algal toxicity (Tier II) for the most TGAI sensitive species—major degradate, 

pentachlorodimethylsulfone (GLN 850.5400);

o Activated Sludge Respiration Inhibition—TGAI (GLN 850.6800 or OECD 

209); and

o Activated Sludge Respiration Inhibition—major degradate

pentachlorodimethylsulfone (GLN 850.6800 or OECD 209).

Facility Emissions to WWTP Modeling

For assessing the fate of BTS and its major degradate, pentachlorodimethylsulfone,

emitted to receiving waters from industrial process water uses of BTS such as at pulp and paper 

mills, for recirculating cooling towers, and oil and gas well development the Agency anticipates 

using the available environmental fate information from guideline studies for BTS and its major 

degradate, pentachlorodimethylsulfone, and the following emission scenarios.

• Potential environmental releases and associated exposures of concern for antimicrobial 

uses related to the Pulp, Paper, and Board Industry will be those identified in "Emission 

Scenario Documents on Pulp, Paper, and Board Industry", Number 23 of OECD Series 

on Emission Scenario Documents dated July 8, 2009.

• Potential environmental releases and associated exposures of concern for antimicrobial 

uses related to the Oil and Gas Well Production Industry will be those identified in the 

latest version of the OECD Emission Scenario Document for the Oil Well Production 

Industry or those identified in the latest version of Generic Scenarios developed by the 

Chemical Engineering Branch of EPA/OCSPP/OPPT/CEB (Chemical Engineering 

Branch). On-shore operations assume potential for disposal of drilling fluids and produce 

water to public or industrial waste treatment facilities and off-shore operations assume 

emissions directly to the surrounding water, post-treatment for removal of oil.

• Potential environmental releases and associated exposures of concern for uses of 

antimicrobial uses related to recirculating cooling towers will be assessed using the 
Page 19 of 40

Generic Scenarios for recirculating cooling towers developed by the Chemical 

Engineering Branch of EPA/OCSPP/OPPT/CEB and modified for use for antimicrobials 

by the Antimicrobial Division.

Facility information needed to estimate aquatic exposures from emissions to WWTP for each 

emission scenario and directly to water from the oil and gas well development sites include the 

following:

• The number of pulp and paper mill sites using BTS or the maximum annual production 

volume of BTS used in pulp and paper mills in the United States and its territories;

• The number of recirculating cooling tower sites using BTS or the maximum annual 

production volume of BTS used in cooling towers in the United States and its territories; 

• The number of oil and gas well development sites using BTS or the maximum annual 

production volume of BTS used in oil and gas well development in the United States and 

its territories; 

• How many of each of these facilities has on-site and/or off-site wastewater treatment.

In the absence of information on the number of these facilities that use BTS and how 

many of these facilities have on-site and/or off-site wastewater treatment, the Agency will 

assume that all such facilities in the United States have the potential to use BTS.

In the absence of appropriate test data on biodegradation during wastewater 

treatment, the Agency will assume that there is no removal of BTS and its major degradate 

during wastewater treatment and that the amount of BTS and its major degradate released with 

the effluent from a wastewater treatment facility will be the same as the amount entering the 

wastewater treatment facility. In the absence of data on the percent removal of BTS and its

major degradate during drinking water treatment the Agency will assume there is no removal of 

BTS or its major degradate, pentachlorodimethylsulfone.

D. References

Maryland Department of Natural Resources (MDNR). 1999. Hydrogen Chloride (HCl) 

Emissions from Maryland Utility Boilers. Prepared by R. Harkov and J. Ross, 

Environmental Resources Management, Annapolis, MD for the Maryland Department of 

Natural Resources Maryland Power Plant Research Program. Report number PPRP-118. 

46 pp. http://esm.versar.com/pprp/hcl/pprp-118pdf.pdf

McCulloch, A., M. Aucott, C. Benkovitz, T. Graedel, G. Kleiman, P. Midgley, and Y. Li. 1999. 

Global emissions of hydrogen chloride and chloromethane from coal combustion, 

incineration and industrial activities: reactive chlorine emissions inventory. Journal of 

Geophysical Research 104(D7):8391-8403.
Page 20 of 40

Appendix A. Environmental Fate Guideline Study Justifications

Study Title: Activated Sludge Sorption Isotherm

Guideline Number: 835.1110

Test Substance: Technical grade active ingredient, bis (trichloromethyl) sulfone

Rationale for Requiring the Data

Data from this study are needed to determine the sorption potential of activated sludge for the removal 

of specific chemical compounds in biological wastewater treatment plants (WWTPs). No data is 

currently available. If the chemical is not sorbed or biodegraded, then it would pass through a 

biological treatment system unaffected, potentially contaminating surface and drinking waters where it 

may then have the potential to adversely affect non-target organisms. EPA needs activated sludge 

sorption study data to assess the distribution of the antimicrobial chemical among the solid, aqueous, 

and vapor phases of WWTPs. Specifically, this study identifies those chemicals which sorb to sludge 

biomass.

Practical Utility of the Data

1. How will the data be used? 

The data will be used to assess removal of the antimicrobial as a result of sorption to activated sludge. 

Percent removal via sorption to activated sludge and percent removal via biodegradation are used to 

determine overall removal of the antimicrobial during wastewater treatment. Overall removal during 

wastewater treatment is a key input used to determine concentrations of the antimicrobial in surface water 

immediately downstream of wastewater treatment plants. The concentrations of antimicrobial pesticide 

immediately downstream of wastewater treatment plants are used to assess exposure and risk to non-target 

endangered and non-endangered species. Exposure data are integral parts of the risk equation for 

determining the impact of pesticides to beneficial nontarget organisms through direct exposure from their 

food sources and habitat.

In addition, the data will be used to determine whether or not additional studies and/or label restrictions are 

needed. If the data indicate that the chemical does not sorb to sludge and instead partitions more readily to 

water and that the chemical does not biodegrade to an appreciable extent then the chemical has the potential 

to pass through the WWTP and therefore could be discharged in to the aquatic environment. This 

determination could trigger further data requirements to assess the chemical’s impact upon release. If the 

data indicates relatively high potential to sorb to sludge, a screening assessment of potential exposure to 

ecological organisms as a result of biosolids use and disposal would be performed.

2. How could the data impact the Agency’s future decision-making?

If the data show that removal of the chemical during wastewater treatment is negligible, then the risk 

assessments for this chemical would reflect the magnitude of potential risk derived from this chemical’s 

negligible removal. The risk assessment may result in the Agency requiring label restrictions that would be 

necessary for the products to meet the “no unreasonable adverse effects” requirements of FIFRA (e.g., 

changes to the directions for disposal).

In addition, EPA is required by section 7(a)(2) of the ESA to ensure that any action it authorizes or takes 

“...is not likely to jeopardize the continued existence of any endangered or threatened species or result in 

the destruction or adverse modification of critical habitat” and to use the best scientific data available” in 

carrying out this obligation. The data EPA intends to call in are necessary to inform the determination 

required by the ESA as to whether continued registration of a pesticide is not likely to jeopardize the 

species or its critical habitat. Absent this data EPA may not be able to conclude that this pesticide will not 

harm endangered species and may therefore need to consider other limitations on the use of the pesticide in 

order to fulfill the Agency’s statutory obligations under the ESA. The lack of these data will limit the 

flexibility that the Agency and registrants have in coming into compliance with the ESA and could result in 
Page 21 of 40

use restrictions which are unnecessarily severe. 

Study Title: Activated Sludge Sorption Isotherm

Guideline Number: 835.1110

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

Data from this study are needed to determine the sorption potential of activated sludge for the removal 

of specific chemical compounds in biological wastewater treatment plants (WWTPs). No data is 

currently available. If the chemical is not sorbed or biodegraded, then it would pass through a 

biological treatment system unaffected, potentially contaminating surface and drinking waters where it 

may then have the potential to adversely affect nontarget organisms. EPA needs activated sludge 

sorption study data to assess the distribution of a major degradate of the antimicrobial chemical among 

the solid, aqueous, and vapor phases of WWTPs. Specifically, this study identifies those chemicals 

which sorb to sludge biomass.

Practical Utility of the Data

1. How will the data be used? 

The data will be used to assess removal of the major degradate, pentachlorodimethylsulfone, of the 

antimicrobial as a result of sorption to activated sludge. Percent removal via sorption to activated sludge 

and percent removal via biodegradation are used to determine overall removal of this degradate during 

wastewater treatment. Overall removal during wastewater treatment is a key input used to determine 

concentrations of the major degradate in surface water immediately downstream of wastewater treatment 

plants. The concentrations of the major degradate immediately downstream of wastewater treatment plants 

are used to assess exposure and risk to non-target endangered and non-endangered species. Exposure data 

are integral parts of the risk equation for determining the impact of pesticides and their major degradates to 

beneficial nontarget organisms through direct exposure from their food sources and habitat.

In addition, the data will be used to determine whether or not additional studies and/or label restrictions are 

needed. If the data indicate that the chemical does not sorb to sludge and instead partitions more readily to 

water and that the chemical does not biodegrade to an appreciable extent then the chemical has the potential 

to pass through the WWTP and therefore could be discharged in to the aquatic environment. This 

determination could trigger further data requirements to assess the chemical’s impact upon release. If the 

data indicates relatively high potential to sorb to sludge, a screening assessment of potential exposure to 

ecological organisms as a result of biosolids use and disposal would be performed.

2. How could the data impact the Agency’s future decision-making?

If the data show that removal of the chemical during wastewater treatment is negligible, then the risk 

assessments for this chemical would reflect the magnitude of potential risk derived from this chemical’s 

negligible removal. The risk assessment may result in the Agency requiring label restrictions that would be 

necessary for the products to meet the “no unreasonable adverse effects” requirements of FIFRA (e.g., 

changes to the directions for disposal).

In addition, EPA is required by section 7(a)(2) of the ESA to ensure that any action it authorizes or takes 

“...is not likely to jeopardize the continued existence of any endangered or threatened species or result in 

the destruction or adverse modification of critical habitat” and to use the best scientific data available” in 

carrying out this obligation. The data EPA intends to call in are necessary to inform the determination 

required by the ESA as to whether continued registration of a pesticide is not likely to jeopardize the 

species or its critical habitat. Absent this data EPA may not be able to conclude that this pesticide will not 

harm endangered species and may therefore need to consider other limitations on the use of the pesticide in 

order to fulfill the Agency’s statutory obligations under the ESA. The lack of these data will limit the 
Page 22 of 40

flexibility that the Agency and registrants have in coming into compliance with the ESA and could result in 

use restrictions which are unnecessarily severe. 

Study Titles: Ready Biodegradability; Porous Pot Test; Simulation Test – Aerobic Sewage 

Treatment: A. Activated Sludge Units; or Simulation Tests to Assess the Biodegradability of 

Chemicals Discharged to Wastewater (particularly Biodegradation in Activated Sludge); or 

Guideline Numbers: 835.3110, 835.3220, 835.3240, or 835.3280 respectively

Test Substance: Technical grade active ingredient, bis (trichloromethyl) sulfone

Rationale for Requiring the Data

For antimicrobial chemicals that go down-the-drain and reach a WWTP, as part of its screening-level 

environmental fate assessment, EPA will analyze the potential impact of the antimicrobial chemical on the 

microorganisms in the biological treatment processes of a WWTP. Biodegradation is an important 

environmental pathway in which the antimicrobial is broken down by bacteria. This study results supply 

information on the rate of biological breakdown and the completeness of the degradation to carbon dioxide 

and water. A ready biodegradability study would allow the Agency to determine whether or not the 

chemical achieves ‘‘pass levels’’ for ready biodegradability (e.g., 70% removal of dissolved organic 

carbon). The results of the Activated Sludge Respiration Inhibition Test (ASRI) determine which of these 

three biodegradation tests are required. If the ASRI test EC50 is less than or equal to 20 mg/L, then either 

the (i) Biodegradation in Activated Sludge Study, or (ii) Simulation Test – Aerobic Sewage Treatment: A. 

Activated Sludge Units, or (iii) the Porous Pot Test is required. If the ASRI test EC50 is greater than 20 

mg/L, then the applicant must choose either: (i) Ready Biodegradability or (ii) a) Biodegradation in 

Activated Sludge, or b) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units or c) the 

Porous Pot Test. If the Ready Biodegradability study is conducted and the antimicrobial passes, then no 

further testing is required. If, however, the antimicrobial fails the Ready Biodegradability study, then the 

(i) Biodegradation in Activated Sludge, or (ii) Simulation Test – Aerobic Sewage Treatment: A. Activated 

Sludge Units, or (iii) the Porous Pot study is required.

Practical Utility of the Data

1. How will the data be used?

The data from a biodegradation study will be used to determine the percent removal of the antimicrobial as 

a result of biodegradation of the antimicrobial by activated sludge microorganisms. Percent removal via 

biodegradation is a key input used to determine concentrations of the antimicrobial in surface water 

immediately downstream of wastewater treatment plants. The concentrations of antimicrobial pesticide 

immediately downstream of wastewater treatment plants are used to assess exposure and risk to non-target 

endangered and non-endangered species. Exposure data are integral parts of the risk equation for 

determining the impact of pesticides to beneficial non-target organisms through direct exposure from their 

food sources and habitat.

In addition, the data will be used to determine whether or not additional studies and/or label restrictions 

are needed. If the chemical does not achieve a ‘‘pass level’’ for ready biodegradability, then the Agency 

would determine that the chemical has the potential to pass through the WWTP and therefore may be 

discharged in to the aquatic environment potentially resulting in exposure to non-target species. This 

determination would trigger further data requirements to assess the chemical’s impact on the aquatic 

environment upon release.

2. How could the data impact the Agency’s future decision-making?

If the chemical is found to be readily biodegraded, then activated sludge microorganisms would be 

identified as highly biodegradable (90% removal via biodegradation). This result would be used in 

conjunction with wastewater treatment plant influent volume and measurement endpoints for aquatic 

organisms to determine concentrations of antimicrobial pesticide downstream of wastewater treatment 

plants. If high inhibition of activated sludge microorganisms (i.e., EC50 less than or equal to 20 mg/L) is 
Page 23 of 40

determined in an activated sludge respiration inhibition test, then higher-tiered wastewater treatment plant 

(WWTP) biodegradation studies and/or an activated sludge sorption isotherm study may be triggered. If 

results of higher-tier WWTP biodegradation tests indicate low or negligible removal by biodegradation, the 

risk assessments for this chemical would reflect the magnitude of potential risk derived from the chemical’s 

lack of biodegradability. The risk assessment may result in the Agency requiring label restrictions that 

would be necessary for the products to meet the “no unreasonable adverse effects” requirements of FIFRA 

(e.g., changes to the directions for disposal).

In addition, EPA is required by section 7(a)(2) of the ESA to ensure that any action it authorizes or takes 

“...is not likely to jeopardize the continued existence of any endangered or threatened species or result in 

the destruction or adverse modification of critical habitat” and to use the best scientific data available” in 

carrying out this obligation. The data EPA intends to call in are necessary to inform the determination 

required by the ESA as to whether continued registration of a pesticide is not likely to jeopardize the 

species or its critical habitat. Absent this data EPA may not be able to conclude that this pesticide will not 

harm endangered species and may therefore need to consider other limitations on the use of the pesticide in 

order to fulfill the Agency’s statutory obligations under the ESA. The lack of these data will limit the 

flexibility that the Agency and registrants have in coming into compliance with the ESA and could result in 

use restrictions which are unnecessarily severe.

Study Titles: Ready Biodegradability; Porous Pot Test; Simulation Test – Aerobic Sewage 

Treatment: A. Activated Sludge Units; or Simulation Tests to Assess the Biodegradability of 

Chemicals Discharged to Wastewater (particularly Biodegradation in Activated Sludge); or 

Guideline Numbers: 835.3110, 835.3220, 835.3240, or 835.3280 respectively

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

For antimicrobial chemicals and their major degradates that go down-the-drain and reach a WWTP, as part 

of its screening-level environmental fate assessment, EPA will analyze the potential impact of the major 

degradate on the microorganisms in the biological treatment processes of a WWTP. Biodegradation is an

important environmental pathway in which the major degradate is broken down by bacteria. This study 

results supply information on the rate of biological breakdown and the completeness of the degradation to 

carbon dioxide and water. A ready biodegradability study would allow the Agency to determine whether or 

not the chemical achieves ‘‘pass levels’’ for ready biodegradability (e.g., 70% removal of dissolved organic 

carbon). The results of the Activated Sludge Respiration Inhibition Test (ASRI) determine which of these 

three biodegradation tests are required. If the ASRI test EC50 is less than or equal to 20 mg/L, then either 

the (i) Biodegradation in Activated Sludge Study, or (ii) Simulation Test – Aerobic Sewage Treatment: A. 

Activated Sludge Units, or (iii) the Porous Pot Test is required. If the ASRI test EC50 is greater than 20 

mg/L, then the applicant must choose either: (i) Ready Biodegradability or (ii) a) Biodegradation in 

Activated Sludge, or b) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units or c) the 

Porous Pot Test. If the Ready Biodegradability study is conducted and the test substance passes, then no 

further testing is required. If, however, the test substance fails the Ready Biodegradability study, then the 

(i) Biodegradation in Activated Sludge, or (ii) Simulation Test – Aerobic Sewage Treatment: A. Activated 

Sludge Units, or (iii) the Porous Pot study is required.
Page 24 of 40

Practical Utility of the Data

1. How will the data be used?

The data from a biodegradation study will be used to determine the percent removal of the antimicrobial as 

a result of biodegradation of the antimicrobial by activated sludge microorganisms. Percent removal via 

biodegradation is a key input used to determine concentrations of the antimicrobial in surface water 

immediately downstream of wastewater treatment plants. The concentrations of antimicrobial pesticide 

immediately downstream of wastewater treatment plants are used to assess exposure and risk to non-target 

endangered and non-endangered species. Exposure data are integral parts of the risk equation for 

determining the impact of pesticides to beneficial non-target organisms through direct exposure from their 

food sources and habitat.

In addition, the data will be used to determine whether or not additional studies and/or label restrictions 

are needed. If the chemical does not achieve a ‘‘pass level’’ for ready biodegradability, then the Agency 

would determine that the chemical has the potential to pass through the WWTP and therefore may be 

discharged in to the aquatic environment potentially resulting in exposure to non-target species. This 

determination would trigger further data requirements to assess the chemical’s impact on the aquatic 

environment upon release.

2. How could the data impact the Agency’s future decision-making?

If the chemical is found to be readily biodegraded, then activated sludge microorganisms would be 

identified as highly biodegradable (90% removal via biodegradation). This result would be used in 

conjunction with wastewater treatment plant influent volume and measurement endpoints for aquatic 

organisms to determine concentrations of antimicrobial pesticide downstream of wastewater treatment 

plants. If high inhibition of activated sludge microorganisms (i.e., EC50 less than or equal to 20 mg/L) is 

determined in an activated sludge respiration inhibition test, then higher-tiered wastewater treatment plant 

(WWTP) biodegradation studies and/or an activated sludge sorption isotherm study may be triggered. If 

results of higher-tier WWTP biodegradation tests indicate low or negligible removal by biodegradation, the 

risk assessments for this chemical would reflect the magnitude of potential risk derived from the chemical’s 

lack of biodegradability. The risk assessment may result in the Agency requiring label restrictions that 

would be necessary for the products to meet the “no unreasonable adverse effects” requirements of FIFRA 

(e.g., changes to the directions for disposal).

In addition, EPA is required by section 7(a)(2) of the ESA to ensure that any action it authorizes or takes 

“...is not likely to jeopardize the continued existence of any endangered or threatened species or result in 

the destruction or adverse modification of critical habitat” and to use the best scientific data available” in 

carrying out this obligation. The data EPA intends to call in are necessary to inform the determination 

required by the ESA as to whether continued registration of a pesticide is not likely to jeopardize the 

species or its critical habitat. Absent this data EPA may not be able to conclude that this pesticide will not 

harm endangered species and may therefore need to consider other limitations on the use of the pesticide in 

order to fulfill the Agency’s statutory obligations under the ESA. The lack of these data will limit the 

flexibility that the Agency and registrants have in coming into compliance with the ESA and could result in 

use restrictions which are unnecessarily severe.
Page 25 of 40

Appendix B: Ecological Guideline Study Justifications

Study Title: Aquatic Invertebrate Acute Toxicity Test, Freshwater

Guideline Number: 850.1010

Test Substance: TGAI

Rationale for Requiring the Data

No scientifically sound acceptable data are available to assess the potential acute lethal risks of BTS to 

freshwater invertebrates. There is supplemental information but the study was conducted under static 

conditions and no analytical measurements were made at any time during the study to document exposure 

concentrations. BTS half-life is <1 day in aquatic aerobic fate studies, so the exposure concentration 

throughout the supplemental study is unknown. Use of such data would greatly underestimate the 

sensitivity and underestimate risk for freshwater invertebrates. Scientifically sound aquatic invertebrate 

data for BTS is necessary because freshwater invertebrates may be exposed based on BTS’s use pattern 

and monitoring data. BTS is used as an algicide, bactericide, slimicide and fungicide for use in 

industrial process and water systems, cooling towers, and it is also used for oil and gas well 

development water systems which may result in discharge of BTS and its major degradate, pentachlorodimethylsulfone to surface waters. The requested data would allow EPA to estimate risks to 

freshwater invertebrates, including defining an action area for endangered species. Without these data, 

the Agency is unable to evaluate the potential risks to freshwater invertebrates associated with acute

exposure to BTS.

Practical Utility of the Data 

1. How will the data be used? 

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The freshwater invertebrate acute study data would allow the 

Agency to analyze acute lethal effects to freshwater invertebrates from acute exposures due to BTC use. 

The effects data would be used to determine the likelihood that the acute risks can potentially impact 

aquatic communities, either by direct effects on invertebrates or by indirect effects by reducing food 

resources to species that rely on invertebrates as a food resource.

2. How could the data impact the Agency’s future decision-making?

Risk estimates (i.e., risk quotients or concentration of concern values) cannot be evaluated without these 

data. In the absence of data, acute risks to freshwater invertebrates would use the supplemental data but 

this would lead to an underestimation of risk, and the degree of underestimation would be unknown. The 

lack of these data will limit the flexibility the Agency and registrants have in addressing risks or having 

confidence in declaring no affects to non-listed and listed species and in coming into compliance with the 

Endangered Species Act, and could result in use restrictions or withdrawal of uses for BTS which may 

otherwise be avoided, or which are unnecessarily severe.

Study Title: Aquatic Invertebrate Acute Toxicity Test, Freshwater

Guideline Number: 850.1010

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

No data are available to assess the potential acute lethal risks of the major toxic degradate pentachlorodimethylsulfone to freshwater invertebrates. Aquatic invertebrate data for 

pentachlorodimethylsulfone is necessary because freshwater invertebrates may be exposed based on 

BTS’s use pattern, fate, and monitoring data. BTS is used as an algicide, bactericide, slimicide and 
Page 26 of 40

fungicide for use in industrial process and water systems, cooling towers, and it is also used for oil 

and gas well development water systems which can result in discharge of BTS and its major degradate, 

pentachlorodimethylsulfone to surface waters. The requested data would allow EPA to estimate risks 

to freshwater invertebrates from exposure to pentachlorodimethylsulfone, including defining an action 

area for endangered species. 

Practical Utility of the Data 

1. How will the data be used? 

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The freshwater invertebrate acute study data would allow the 

Agency to analyze acute lethal effects to freshwater invertebrates from acute exposures due to BTC use

and fate. The effects data with the degradate would be used to determine the likelihood that the acute 

risks can potentially impact aquatic communities, either by direct effects on invertebrates or by indirect 

effects by reducing food resources to species that rely on invertebrates as a food resource.

2. How could the data impact the Agency’s future decision-making?

Risk estimates (i.e., risk quotients or concentration of concern values) cannot be evaluated without these 

data. In the absence of data, if an acute toxicity test is available for BTS the toxicity of the degradate will 

be assumed to be equivalent to that of the parent BTS otherwise acute risks to freshwater invertebrates 

would be presumed; the Agency would have to assume that BTS and its degradate “may affect” 

endangered freshwater invertebrates directly (and endangered species from other taxa indirectly). The 

lack of these data will limit the flexibility the Agency and registrants have in addressing risks to nonlisted and listed species and in coming into compliance with the Endangered Species Act, and could result 

in use restrictions or withdrawal of uses for BTS which may otherwise be avoided, or which are 

unnecessarily severe.

Study Title: Estuarine/marine invertebrate acute toxicity test one crustacean species

Guideline Number: 850.1035

Test Substance: TGAI

Rationale for Requiring the Data

A crustacean (mysid) is one of two representative saltwater species used to evaluate acute effects for all 

estuarine/marine invertebrates. No acceptable acute study for BTS with an estuarine/marine crustacean 

species has been submitted; there is an acceptable acute mollusk study. An acute test using an 

estuarine/marine crustacean species is required because the active ingredient is expected to reach 

estuarine/marine environments based on its use patterns, monitoring data, and because physiological 

differences which allow estuarine/marine invertebrates to live in an estuarine/marine environments may 

result in this group being more sensitive than freshwater species. Without these data, there is uncertainty 

in the representation of the mollusk as the more sensitive species. Acute risks based on mollusk data can 

be calculated, but there would be uncertainty in whether the calculated risk is an underestimate, and the 

degree of underestimation.

Practical Utility of the Data

1. How will the data be used?

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The estuarine/marine invertebrate acute studies allow the 

Agency to analyze acute lethal effects to estuarine/marine invertebrates from acute exposures due to BTS

use. The effects data would be used to determine the likelihood that the acute risks can potentially 

impact aquatic communities, either by direct effects on invertebrates or by indirect effects by reducing 
Page 27 of 40

food resources to species that rely on invertebrates as a food resource. 

2. How could the data impact the Agency’s future decision-making?

In the absence of acute mysid data, acute risks to marine/estuarine invertebrates would be calculated 

based on the mollusk data alone. But there would be uncertainty in whether the calculated risk is an 

underestimate, and the degree of underestimation. Decisions may be made incorrectly based on these 

results.

Study Title: Estuarine/marine invertebrate acute toxicity test, one crustacean species study and 

one embryo larvae mollusk study

Guideline Number: 850.1035 and 850.1055, respectively

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

A crustacean (mysid) and mollusk test are representative saltwater species used to evaluate acute effects 

for all estuarine/marine invertebrates. No acceptable acute studies for the major degradate, pentachlorodimethylsulfone, with an estuarine/marine crustacean species or mollusk has been submitted. An acute 

test using an estuarine/marine mollusk species and crustacean is required because this major degradate is 

expected to reach estuarine/marine environments based on BTS use patterns, fate, and monitoring data. 

Additionally to calculate an acute-to-chronic ratio for this degradate for an estuarine/marine invertebrate 

species, the mysid acute study is required to pair with the chronic study discussed in the Justification 

Table for Estuarine/marine invertebrate, life cycle test. The mollusk embryo larvae study is also required 

because it tentatively appears likely to be the most sensitive of all aquatic organisms, both freshwater and 

estuarine/marine based on the acceptable BTS mollusk study and the supplemental freshwater fish and 

invertebrate data. The mode-of-action to mollusks may be different from that of crustaceans and fish, 

and therefore any BTS: pentachlorodimethylsulfone ratio or factor derived from crustacean or fish data 

may underestimate the degradate toxicity to mollusks. In the absence of data, the degradate would be 

assumed to be as toxic as the parent, BTS, for both the crustacean and the mollusk.

Practical Utility of the Data

1. How will the data be used?

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The estuarine/marine invertebrate acute studies allow the 

Agency to analyze acute lethal effects to estuarine/marine invertebrates from acute exposures due to BTS 

use. The effects data would be used to determine the likelihood that the acute risks can potentially 

impact aquatic communities, either by direct effects on invertebrates or by indirect effects by reducing 

food resources to species that rely on invertebrates as a food resource. 

2. How could the data impact the Agency’s future decision-making?

In the absence of acute mysid and mollusk data, acute risks to marine/estuarine invertebrates would be 

calculated assuming that the degradate is as toxic as the parent, and potentially be based on the mollusk 

alone if acute crustacean data for BTS is not submitted (see the Estuarine/marine invertebrate acute 

toxicity test one crustacean species Justification Table above) which may result in underestimation of 

risk.
Page 28 of 40

Study Title: Fish acute toxicity test (freshwater species, one cold water species study and one warm 

water species study)

Guideline Number: 850.1075

Test Substance: TGAI

Rationale for Requiring the Data

No scientifically sound acceptable data are available to assess the potential acute lethal risks of BTS to 

freshwater fish. There is supplemental information but the studies were conducted under static 

conditions and no analytical measurements were made at any time during the studies to document 

exposure concentrations. BTS half-life is <1 day in aquatic aerobic fate studies, so the exposure 

concentration throughout the supplemental studies is unknown. Use of such data would greatly 

underestimate the sensitivity and underestimate risk for freshwater fish. Scientifically sound freshwater 

fish data for BTS is necessary because freshwater fish may be exposed based on BTS’s use pattern and 

monitoring data. A warm water species study and a cold water species study are both necessary to 

capture and characterize if differences that allow these species to live in such different temperature 

regimes, such as metabolism and differences in activation and deactivation pathways, result in distinctive 

differences in sensitivity to BTS. The most sensitive value of the two is used to screen for risk concerns. 

BTS is used as an algicide, bactericide, slimicide and fungicide for use in industrial process and 

water systems, cooling towers, and it is also used for oil and gas well development water systems 

which may result in discharge of BTS and its major degradate, pentachlorodimethylsulfone to surface 

waters. The requested data would allow EPA to soundly estimate risks to freshwater fish, including 

defining an action area for endangered species. Without these data, the Agency would use the 

supplemental data which would underestimate risk to an unknown degree.

Practical Utility of the Data

1. How will the data be used?

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The freshwater fish acute study data would allow the Agency 

to analyze acute lethal effects to freshwater fish from acute exposures due to BTC use. The effects data 

would be used to determine the likelihood that the acute risks can potentially impact aquatic 

communities, either by direct effects on fish or by indirect effects by reducing food resources to species 

that rely on fish as a food resource.

2. How could the data impact the Agency’s future decision-making?

Risk estimates (i.e., risk quotients or concentration of concern values) cannot be evaluated without these 

data. In the absence of data, acute risks to freshwater fish would use the supplemental data but this 

would lead to an underestimation of risk, and the degree of underestimation would be unknown. The 

lack of these data will limit the flexibility the Agency and registrants have in addressing risks or having 

confidence in declaring no affects to non-listed and listed species and in coming into compliance with the 

Endangered Species Act, and could result in use restrictions or withdrawal of uses for BTS which may 

otherwise be avoided, or which are unnecessarily severe.

Study Title: Fish acute toxicity test (freshwater species, most sensitive of the TGAI species)

Guideline Number: 850.1075

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

No data are available to assess the potential acute lethal risks of the major toxic degradate

pentachlorodimethyl-sulfone to freshwater fish. Fish acute data for pentachlorodimethylsulfone, is
Page 29 of 40

necessary because freshwater fish may be exposed based on BTS’s use pattern, fate, and monitoring data. 

Only data for the most sensitive of the TGAI species is required, as this should also be the more sensitive 

species for the degradate. BTS is used as an algicide, bactericide, slimicide and fungicide for use in 

industrial process and water systems, cooling towers, and it is also used for oil and gas well 

development water systems which can result in discharge of BTS and its major degradate, 

pentachlorodimethylsulfone to surface waters. The requested data would allow EPA to estimate risks 

to freshwater fish from exposure to pentachlorodimethylsulfone, including defining an action area for 

endangered species. 

Practical Utility of the Data

1. How will the data be used?

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The freshwater fish acute study data would allow the Agency 

to analyze acute lethal effects to freshwater fish from acute exposures due to BTC use and fate. The 

effects data with the degradate would be used to determine the likelihood that the acute risks can 

potentially impact aquatic communities, either by direct effects on fish or by indirect effects by reducing 

food resources to species that rely on fish as a food resource.

2. How could the data impact the Agency’s future decision-making?

Risk estimates (i.e., risk quotients or concentration of concern values) cannot be evaluated without these 

data. In the absence of data, if an acute toxicity test is available for BTS the toxicity of the degradate will 

be assumed to be equivalent to that of the parent BTS otherwise if no TGAI or degradate data is available 

acute risks to freshwater fish would be presumed; the Agency would have to assume that BTS and its 

degradate “may affect” endangered freshwater fish directly (and endangered species from other taxa 

indirectly). The lack of these data will limit the flexibility the Agency and registrants have in addressing 

risks to non-listed and listed species and in coming into compliance with the Endangered Species Act, 

and could result in use restrictions or withdrawal of uses for BTS which may otherwise be avoided, or 

which are unnecessarily severe.

Study Title: Fish acute toxicity test (estuarine/marine species)

Guideline Number: 850.1075

Test Substance: TGAI

Rationale for Requiring the Data

No scientifically sound acceptable data are available to assess the potential acute lethal risks of BTS to 

estuarine/marine fish. There is supplemental information but the study was conducted under static 

conditions and no analytical measurements were made at any time during the study to document exposure 

concentrations. BTS half-life is <1 day in aquatic aerobic fate studies, so the exposure concentration 

throughout the supplemental study is unknown. Use of such data would greatly underestimate the 

sensitivity and underestimate risk for estuarine/marine fish. Scientifically sound estuarine/marine fish 

data for BTS is necessary because estuarine/marine fish may be exposed based on BTS’s use pattern and 

monitoring data. BTS is used as an algicide, bactericide, slimicide and fungicide for use in 

industrial process and water systems, cooling towers, and it is also used for oil and gas well 

development water systems which may result in discharge of BTS and its major degradate, 

pentachlorodimethylsulfone to surface waters. The requested data would allow EPA to soundly 

estimate risks to estuarine/marine fish, including defining an action area for endangered species. Without 

these data, the Agency would use the supplemental data which would underestimate risk to an unknown 

degree.
Page 30 of 40

Practical Utility of the Data

1. How will the data be used?

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The estuarine/marine fish acute study would allow the Agency 

to analyze acute lethal effects to estuarine/marine fish from acute exposures due to BTS use. The effects 

data would be used to determine the likelihood that the acute risks can potentially impact aquatic 

communities, either by direct effects on fish or by indirect effects by reducing food resources to species 

that rely on fish as a food resource. 

2. How could the data impact the Agency’s future decision-making?

Risk estimates (i.e., risk quotients or concentration of concern values) cannot be evaluated without these 

data. In the absence of data, acute risks to estuarine/marine fish would either use the supplemental data 

which would lead to an underestimation of risk, with the degree of underestimation unknown, or 

potentially depending on what results are provided for freshwater fish and invertebrates and their 

relationship to the supplemental data, some estimate of the degree to which underestimation may be 

occurring could be made or if the data indicates that mollusks are the most sensitive aquatic species of the 

existing freshwater fish and invertebrate data, then the sensitivity of estuarine/marine fish can be assumed 

to be equivalent to that of the mollusk results. The lack of these data will limit the flexibility the Agency 

and registrants have in addressing risks or having confidence in declaring no affects to non-listed and 

listed species and in coming into compliance with the Endangered Species Act, and could result in use 

restrictions or withdrawal of uses for BTS which may otherwise be avoided, or which are unnecessarily 

severe.

Study Title: Aquatic Invertebrate Life-Cycle (freshwater species)

Guideline Number: 850.1300

Test Substance: TGAI

Rationale for Requiring the Data

No chronic life cycle toxicity data for a freshwater invertebrate species has been submitted for BTS. 

Chronic aquatic invertebrate data for BTS is necessary because based on BTS’s use pattern, fate, and 

monitoring data freshwater invertebrates may be repeatedly exposed to BTS and its major degradate, 

pentachlorodimethylsulfone. BTS is used as an algicide, bactericide, slimicide and fungicide for use

in industrial process and water systems, cooling towers, and it is also used for oil and gas well 

development water systems which can result in discharge of BTS and its major degradate, 

pentachlorodimethylsulfone to surface waters. The requested data would allow the Agency to estimate 

chronic risks to freshwater invertebrates from exposure to BTS, including defining an action area for 

endangered species. Without these data, the Agency is unable to evaluate the potential chronic risks to 

freshwater invertebrates associated with chronic exposure to BTS. The Agency would have to presume 

chronic risk to listed and non-listed freshwater invertebrates, but would not be able to quantify the risk.
Page 31 of 40

Practical Utility of the Data

1. How will the data be used? 

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The aquatic invertebrate life-cycle study would allow the 

Agency to analyze chronic effects, including effects on reproductive success, survival and growth, to 

freshwater invertebrates due to exposure to BTS. The effects data would be used to determine the 

likelihood that the chronic risks can potentially impact aquatic communities, either by direct effects on 

invertebrates or by indirect effects on fish by reducing their food sources. 

2. How could the data impact the Agency’s future decision-making?

In the absence of data, chronic risks would be presumed to freshwater invertebrates under chronic exposure 

conditions. The lack of these data will limit the flexibility the Agency and registrants have in addressing 

risks to non-listed and listed species and in coming into compliance with the Endangered Species Act, and 

could result in use restrictions or withdrawal of uses for BTS which may otherwise be avoided, or which 

are unnecessarily severe.

Study Title: Aquatic Invertebrate Life-Cycle (freshwater species)

Guideline Number: 850.1300

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

No chronic life cycle toxicity data for a freshwater invertebrate species has been submitted for the major 

degradate pentachlorodimethylsulfone. Chronic aquatic invertebrate data for this degradate is necessary 

because based on BTS’s use pattern, fate, and monitoring data freshwater invertebrates may be repeatedly 

exposed to BTS and its major degradate, pentachlorodimethylsulfone. BTS is used as an algicide, 

bactericide, slimicide and fungicide for use in industrial process and water systems, cooling 

towers, and it is also used for oil and gas well development water systems which can result in discharge of 

BTS and its major degradate, pentachlorodimethylsulfone to surface waters. The requested data would 

allow the Agency to estimate chronic risks to freshwater invertebrates from exposure to this degradate, 

including defining an action area for endangered species. Without these data, the Agency would have to 

assume that the degradate is at least as toxic as the parent, BTS. However, there is no chronic data for the 

parent either, so without these data, the Agency is unable to evaluate the potential risks to freshwater 

invertebrates associated with chronic exposure to BTS or its degradate. The Agency would have to 

presume chronic risk to listed and non-listed freshwater invertebrates, but would not be able to quantify the 

risk.
Page 32 of 40

Practical Utility of the Data

1. How will the data be used? 

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The aquatic invertebrate life-cycle study would allow the 

Agency to analyze chronic effects, including effects on reproductive success, survival and growth, to 

freshwater invertebrates due to exposure to the degradate, pentachlorodimethylsulfone. The effects data 

would be used to determine the likelihood that the chronic risks can potentially impact aquatic 

communities, either by direct effects on invertebrates or by indirect effects on fish by reducing their food 

sources. 

2. How could the data impact the Agency’s future decision-making?

In the absence of data, the Agency would have to assume that the degradate is at least as toxic as the parent, 

BTS. However, there is no chronic data for the parent either, so without these data, the Agency is unable to 

evaluate the potential risks to freshwater invertebrates associated with chronic exposure to BTS or its

degradate. The lack of these data will limit the flexibility the Agency and registrants have in addressing 

risks to non-listed and listed species and in coming into compliance with the Endangered Species Act, and 

could result in use restrictions or withdrawal of uses for BTS which may otherwise be avoided, or which 

are unnecessarily severe.

Study Title: Aquatic Invertebrate Life-Cycle (estuarine/marine species)

Guideline Number: 850.1350

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

No chronic life cycle toxicity test for an estuarine/marine invertebrate species has been submitted for the 

degradate, pentachlorodimethylsulfone. Chronic aquatic invertebrate data for this degradate is necessary 

because based on BTS’s use pattern, fate, and monitoring data freshwater invertebrates may be repeatedly 

exposed to BTS and its major degradate, pentachlorodimethylsulfone. BTS is used as an algicide, 

bactericide, slimicide and fungicide for use in industrial process and water systems, cooling 

towers, and it is also used for oil and gas well development water systems which can result in discharge of 

BTS and its major degradate, pentachlorodimethylsulfone to surface waters. A chronic study with BTS 

was not requested because tentatively the mollusk appears to be more sensitive than estuarine/marine fish 

and freshwater invertebrates. If the acute mysid toxicity data with BTS results in mysid being more 

sensitive than the mollusk, the acute-to-chronic ratio derived from the degradate and from freshwater 

invertebrate data for BTS can be used to estimate a BTS chronic value for the mysid. Without the

estuarine/marine life-cycle data for the degradate, the Agency is unable to evaluate the potential risks to 

estuarine/marine invertebrates associated with chronic exposure to the degradate or the parent. The Agency 

would have to presume chronic risk to listed and non-listed estuarine/marine invertebrates, but would not 

be able to quantify the risk.
Page 33 of 40

Practical Utility of the Data

1. How will the data be used? 

The aquatic invertebrate life-cycle study would allow the Agency to analyze chronic effects, including 

effects on reproductive success, survival and growth, to estuarine/marine invertebrates. The effects data 

would be used to determine the likelihood that the chronic risks can potentially impact aquatic 

communities, either by direct effects on invertebrates or by indirect effects to organisms preying on 

estuarine/marine invertebrates. 

2. How could the data impact the Agency’s future decision-making?

In the absence of data, chronic risks would be presumed to estuarine/marine invertebrates under chronic 

exposure conditions. The lack of these data will limit the flexibility the Agency and registrants have in 

addressing risks to non-listed and listed species and in coming into compliance with the Endangered 

Species Act, and could result in use restrictions or withdrawal of uses for TTPC which may otherwise be 

avoided, or which are unnecessarily severe.

Study Title: Fish Early-life Stage Toxicity Test (freshwater species)

Guideline Number: 850.1400

Test Substance: TGAI

Rationale for Requiring the Data

No fish early-life stage toxicity test for BTS has been submitted. The fish early-life stage toxicity test 

provides the lethal and sublethal effects of a test substance on fish species. The study is necessary for 

BTS because the antimicrobial use patterns and environmental fate characteristics are expected to result in 

repeated exposure of freshwater organisms. The requested data would allow the Agency to estimate 

chronic risks to freshwater fish from exposure to BTS, including defining an action area for endangered 

species. Without these data, the Agency is unable to evaluate the potential risks to freshwater fish and 

aquatic-phase amphibians (for which fish serve as surrogates) associated with chronic exposure to BTS. 

If the test is not conducted with the most acutely sensitive species, an acute toxicity test for the species 

used in the early life stage test needs to be conducted to allow calculation of an acute-to-chronic ratio for 

use in predicting an early life stage result for the most acutely sensitive species.

Practical Utility of the Data

1. How will the data be used? 

The data from the fish early life stage test will be used to estimate the chronic risks to freshwater fish and 

amphibians associated with chronic exposures to BTS. The data will reduce uncertainties associated with 

potential risks to freshwater fish and amphibians thereby facilitating sound environmental management of 

natural resources, particularly, freshwater fisheries. 

2. How could the data impact the Agency’s future decision-making?

In the absence of data, chronic risks would be presumed to freshwater fish/amphibians under chronic 

exposure conditions. The lack of these data will limit the flexibility the Agency and registrants have in 

addressing risks to non-listed and listed species and in coming into compliance with the Endangered 

Species Act, and could result in use restrictions or withdrawal of uses for TTPC which may otherwise be 

avoided, or which are unnecessarily severe.
Page 34 of 40

Study Title: Fish Early-life Stage Toxicity Test (freshwater species)

Guideline Number: 850.1400

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

No fish early-life stage toxicity test for the major degradate, pentachlorodimethylsulfone, has been 

submitted. The fish early-life stage toxicity test provides the lethal and sublethal effects of a test 

substance on fish species. Chronic aquatic invertebrate data for this degradate is necessary because based 

on BTS’s use pattern, fate, and monitoring data freshwater invertebrates may be repeatedly exposed to 

BTS and its major degradate, pentachlorodimethylsulfone. BTS is used as an algicide, bactericide, 

slimicide and fungicide for use in industrial process and water systems, cooling towers, and it is 

also used for oil and gas well development water systems which can result in discharge of BTS and its

major degradate, pentachlorodimethylsulfone to surface waters. The requested data would allow the 

Agency to estimate chronic risks to freshwater fish from exposure to this degradate, including defining an 

action area for endangered species. Without these data, the Agency is unable to evaluate the potential 

risks to freshwater fish and aquatic-phase amphibians (for which fish serve as surrogates) associated with 

chronic exposure to the degradate. If the test is not conducted with the most acutely sensitive species, an 

acute toxicity test for the species used in the early life stage test needs to be conducted to allow 

calculation of an acute-to-chronic ratio for use in predicting an early life stage result for the most acutely 

sensitive species.

Practical Utility of the Data

1. How will the data be used? 

The data from the fish early life stage test will be used to estimate the chronic risks to freshwater fish and 

amphibians associated with chronic exposures to BTS and its degradate. The data will reduce 

uncertainties associated with potential risks to freshwater fish and amphibians thereby facilitating sound 

environmental management of natural resources, particularly, freshwater fisheries. 

2. How could the data impact the Agency’s future decision-making?

In the absence of data, the toxicity of the degradate would be assumed to be the same as that of the parent, 

if chronic data for the parent was submitted, or if this data is not available either chronic risks would be

presumed to freshwater fish/amphibians under chronic exposure conditions. The lack of these data will 

limit the flexibility the Agency and registrants have in addressing risks to non-listed and listed species 

and in coming into compliance with the Endangered Species Act, and could result in use restrictions or 

withdrawal of uses for TTPC which may otherwise be avoided, or which are unnecessarily severe.

Study Title: Seedling emergence Tier II

Test Species: Rice, Oryza sativa

Guideline Number: 850.4225

Test Substance: Degradate, pentachlorodimethylsulfone

Application method: Homogenously mixed into support media

Unit of Expression: milligrams per kilogram of bulk support media (dry wt)

Rationale for Requiring the Data

No seedling emergence and growth toxicity data for a rooted emergent vascular plant has been submitted

for BTS or its major degradate. Based on the fate of BTS, it is not expected to be persistent in the water 

column or sediment. However, the major degradate is more persistent and may sorb onto organic and 

inorganic particles in water and depositing with them in sedimentary areas such as lakes, and freshwater 

and saltwater marshes. Uses of BTS in industrial process and water systems, cooling towers, and 
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discharges from oil and gas well development water systems are expected to lead to exposure of wetland 

plants due to transportation, and deposition of pentachlorodimethylsulfone sorbed onto particles in the 

waste stream from use sites. Without this data, the Agency is unable to evaluate the potential risks to 

rooted vascular emergent plants associated with exposure to pentachlorodimethylsulfone. In the study, a 

minimum of four replicates are necessary to allow a nonparametric statistical analysis, if the resulting data 

fail normality or homogeneity of variance assumptions.

Practical Utility of the Data

1. How will the data be used?

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. Emergent wetland plants, in association with soil or sediments, 

determine the structure and function of wetlands; they provide habitat in the form of nursery areas and 

cover for wildlife, and regulate the temperature and flow of water. The emergent vascular plant study

would allow the Agency to analyze to a critical component of the structure and function of an aquatic 

ecosystem. A toxicity study on an emergent vascular plant species is used to establish a dose response 

relationship of BTS with in terms of yield, growth rate, and area under the growth curve. The effects data 

would be used to determine the likelihood that losses to emergent plants will occur and that such losses 

would indirectly lead to loss of other aquatic organisms through impacts such as loss of a food resource, 

habitat, or habitat quality. 

2. How could the data impact the Agency's future decision-making?

In the absence of data, risks to emergent aquatic plants could not be calculated. Therefore, until 

additional data become available, risks to emergent vascular plants (both Federally-listed and non-listed 

species) will be assumed in future BTS risk assessments. The lack of these data will limit the flexibility 

the Agency and registrants have in addressing risks to non-listed and listed species and in coming into 

compliance with the Endangered Species Act, and could result in use restrictions or withdrawal of uses 

for TTPC which may otherwise be avoided, or which are unnecessarily severe.

Study Title: Aquatic plant growth, floating vascular species (Lemna sp.), Tier II

Guideline Number: 850.4400

Test Substance: TGAI

Rationale for Requiring the Data

No non-rooted vascular aquatic plant toxicity data has been submitted for BTS. BTS is used as an 

algicide, bactericide, slimicide and fungicide for use in industrial process and water systems, 

cooling towers, and it is also used for oil and gas well development water systems which can result in 

discharge of BTS and its major degradate, pentachlorodimethylsulfone to surface waters. Without 

these data, the Agency is unable to evaluate the potential risks to non-rooted vascular aquatic plants 

associated with exposure to BTS. 

Practical Utility of the Data

1. How will the data be used?

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. Mats of floating non-rooted aquatic plants provide habitat for 

small invertebrates, food and shelter for fish and amphibians, and food for waterfowl and marsh birds. 

The floating vascular aquatic plant study would allow the Agency to evaluate effects to a critical 

component of the structure and function of the aquatic plant community. A toxicity study on a non-rooted 

vascular aquatic plant species is used to establish a dose response relationship of BTS with effects to nonrooted aquatic plants in terms of yield, growth rate, and area under the growth curve. The effects data 

would be used to determine the likelihood that losses to non-rooted aquatic vascular plants will occur and 
Page 36 of 40

that such losses would indirectly lead to loss of other aquatic organisms through impacts such as loss of a 

food resource, habitat, or habitat quality. 

2. How could the data impact the Agency's future decision-making?

In the absence of data, risks could not be calculated for aquatic nonrooted macrophytes. Therefore, until 

additional data become available, risks to non-rooted vascular plants (both Federally-listed and non-listed 

species) will be assumed in future BTS risk assessments. The lack of these data will limit the flexibility 

the Agency and registrants have in addressing risks to non-listed and listed species and in coming into 

compliance with the Endangered Species Act, and could result in use restrictions or withdrawal of uses 

for BTS which may otherwise be avoided, or which are unnecessarily severe.

Study Title: Aquatic plant growth, floating vascular species (Lemna sp.), Tier II

Guideline Number: 850.4400

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

No non-rooted vascular aquatic plant toxicity data has been submitted for the major degradate

pentachlorodimethylsulfone. BTS is used as an algicide, bactericide, slimicide and fungicide for use

in industrial process and water systems, cooling towers, and it is also used for oil and gas well 

development water systems which can result in discharge of BTS and its major degradate, 

pentachlorodimethylsulfone to surface waters. The requested data would allow the Agency to 

estimate risks to aquatic plants from exposure to pentachlorodimethylsulfone, including defining an 

action area for endangered species.

Practical Utility of the Data

1. How will the data be used?

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. Mats of floating non-rooted aquatic plants provide habitat for 

small invertebrates, food and shelter for fish and amphibians, and food for waterfowl and marsh birds. 

The floating vascular aquatic plant study would allow the Agency to evaluate effects to a critical 

component of the structure and function of the aquatic plant community. A toxicity study on a non-rooted 

vascular aquatic plant species is used to establish a dose response relationship of 

pentachlorodimethylsulfone with effects to non-rooted aquatic plants in terms of yield, growth rate, and 

area under the growth curve. The effects data would be used to determine the likelihood that losses to 

non-rooted aquatic vascular plants will occur and that such losses would indirectly lead to loss of other 

aquatic organisms through impacts such as loss of a food resource, habitat, or habitat quality. 

2. How could the data impact the Agency's future decision-making?

In the absence of data, the toxicity of the degradate would be assumed to be the same as that of the parent, 

if data for the parent was submitted, or if this data is not available either risks would be presumed for 

listed and nonlisted aquatic plants. The lack of these data will limit the flexibility the Agency and 

registrants have in addressing risks to non-listed and listed species and in coming into compliance with 

the Endangered Species Act, and could result in use restrictions or withdrawal of uses for BTS which may 

otherwise be avoided, or which are unnecessarily severe.
Page 37 of 40

Study Title: Aquatic plant growth, non-vascular species (one freshwater green alga species, one 

freshwater diatom species, one estuarine/marine species, and one cyanobacterium species), Tier II

Guideline Number: 850.5400

Test Substance: TGAI

Rationale for Requiring the Data

No nonvascular aquatic plant toxicity data has been submitted for BTS. A battery of four species, 

representing different morphological characteristics and environmental habitats are required for use 

patterns resulting in emissions to surface waters. Uses of BTS in industrial process and water systems, 

cooling towers, and discharges from oil and gas well development are expected to lead to exposure of 

aquatic organisms due to the repeated release and transport of BTS and its major degradate from use sites 

into aquatic ecosystems. Without these data, the Agency is unable to evaluate the potential risks to nonvascular aquatic plants associated with exposure to BTS. The Agency would have to presume risk to 

federally listed and non-listed non-vascular plants, but would not be able to quantify the risk.

Practical Utility of the Data

1. How will the data be used?

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The four aquatic nonvascular plant studies would allow the 

Agency to analyze effects on primary production. A toxicity study on non-vascular aquatic plant species 

is used to establish a dose response relationship of BTC with primary productivity in terms of yield, 

growth rate, and area under the growth curve. The effects data would be used to determine the likelihood 

that losses to primary production will occur and that such losses would indirectly lead to loss of other 

aquatic organisms through impacts such as loss of a food resource, habitat, or habitat quality. 

2. How could the data impact the Agency's future decision-making?

In the absence of data, risks to nonvascular primary productivity could not be calculated. Therefore, until 

additional data become available, risks to aquatic non-vascular plants (both Federally-listed and nonlisted species) will be assumed in future BTS risk assessments. The lack of these data will limit the 

flexibility the Agency and registrants have in addressing risks to non-listed and listed species and in 

coming into compliance with the Endangered Species Act, and could result in use restrictions or 

withdrawal of uses for BTS which may otherwise be avoided, or which are unnecessarily severe.
Page 38 of 40

Study Title: Aquatic plant growth, non-vascular species (most sensitive of the TGAI tested species), 

Tier II

Guideline Number: 850.5400

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

No nonvascular aquatic plant toxicity data has been submitted for the major degradate

pentachlorodimethylsulfone. Uses of BTS in industrial process and water systems, cooling towers, and 

discharges from oil and gas well development are expected to lead to exposure of aquatic organisms due 

to the repeated release and transport of BTS and its major degradate from use sites into aquatic 

ecosystems. A battery of four non-vascular tests with the parent BTS have been requested, only a test 

with the most sensitive of these species is needed to evaluate the toxicity of the degradate relative to the 

parent. Without this degradate data, the Agency would have to assume that the degradate is as toxic as 

the parent and if there is no parent data the Agency would be unable to calculate risk for BTS and its

major degradate. The Agency would have to presume risk to federally listed and non-listed non-vascular 

plants, but would not be able to quantify the risk.

Practical Utility of the Data

1. How will the data be used?

These data are needed for a registration review decision and for an endangered species assessment, which 

will be conducted as part of that decision. The aquatic nonvascular plant study would allow the Agency

to analyze effects on primary production from exposure to the degradate. A toxicity study on nonvascular aquatic plant species is used to establish a dose response relationship of the degradate with 

primary productivity in terms of yield, growth rate, and area under the growth curve. The effects data 

would be used to determine the likelihood that losses to primary production will occur and that such 

losses would indirectly lead to loss of other aquatic organisms through impacts such as loss of a food 

resource, habitat, or habitat quality. 

2. How could the data impact the Agency's future decision-making?

In the absence of data, the toxicity of the degradate would be assumed to be the same as that of the parent, 

if data for the parent was submitted, or if this data is not available then risks would be presumed to listed 

and nonlisted aquatic plants. Therefore, until additional data become available, risks to aquatic nonvascular plants (both Federally-listed and non-listed species) will be assumed in future BTS risk 

assessments. The lack of these data will limit the flexibility the Agency and registrants have in 

addressing risks to non-listed and listed species and in coming into compliance with the Endangered 

Species Act, and could result in use restrictions or withdrawal of uses for BTS which may otherwise be 

avoided, or which are unnecessarily severe.

Study Title: Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals; 

Activated Sludge Respiration Inhibition Test

Guideline Number: 850.6800 or OECD 209, respectively

Test Substance: TGAI, bis (trichloromethyl) sulfone

Rationale for Requiring the Data

An activated sludge, respiration inhibition test (ASRI) is needed to identify whether this pesticide could 

harm activated sludge microorganisms found in biological wastewater treatment systems. The Agency 

will use these data to determine the potential impact of this chemical on waste water treatment plants 

(WWTPs) as a result of respiration inhibition of activated sludge microorganisms. This test is also 

necessary to enable the Agency to establish correct concentrations for use in the biodegradability test, if 

that test is determined to be adequate for assessing biodegradation potential. Furthermore, the results of 

the Activated Sludge Respiration Inhibition Test (ASRI) determine which biodegradation test is required. 
Page 39 of 40

If the ASRI test EC50 is less than or equal to 20 mg/L, then either the (i) Biodegradation in Activated 

Sludge Study or (ii) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units, or (iii) the 

Porous Pot Test is required. If the ASRI test EC50 is greater than 20 mg/L, then the applicant must choose 

either: (i) Ready Biodegradability or (ii) a) Biodegradation in Activated Sludge or b) Simulation Test –

Aerobic Sewage Treatment: A. Activated Sludge Units, or c) the Porous Pot Test. If the Ready 

Biodegradability study is conducted and the antimicrobial passes, then no further testing is required. If, 

however, the antimicrobial fails the Ready Biodegradability study, then the (i) Biodegradation in Activated 

Sludge or (ii) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units or (iii) the Porous 

Pot study is required.

Practical Utility of the Data

1. How will the data be used?

The data will be used to assess potential adverse effects to activated sludge microorganisms from BTS. In 

addition, the data will be used to determine whether or not label restrictions are needed. The study will 

identify the inhibitory effect of this chemical on the treatment plant’s microorganisms’ respiration at 

different concentrations of the test substance and will identify the EC50, the effective concentration of the 

test substance at which the respiration rate is 50% of that shown by the control under conditions in this 

guideline. The data will also determine suitable non-inhibitory concentrations to be used in 

biodegradability tests.

2. How could the data impact the Agency’s future decision-making?

If the data indicate a high degree of activated sludge respiration inhibition, a more rigorous test for 

biodegradation in wastewater treatment will be required than the Ready Biodegradability test. Also, if a 

high degree of respiration inhibition is demonstrated and biodegradation and/or sorption is indicated to be 

negligible, the Agency may require label restrictions or mitigation measures to insure that activated sludge 

microorganisms will not be adversely impacted.

Study Title: Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals; 

Activated Sludge Respiration Inhibition Test

Guideline Number: 850.6800 or OECD 209, respectively

Test Substance: Degradate, pentachlorodimethylsulfone

Rationale for Requiring the Data

An activated sludge, respiration inhibition test (ASRI) is needed to identify whether this major degradate

could harm activated sludge microorganisms found in biological wastewater treatment systems. The 

Agency will use these data to determine the potential impact of this chemical on waste water treatment 

plants (WWTPs) as a result of respiration inhibition of activated sludge microorganisms. This test is also 

necessary to enable EPA to establish correct concentrations for use in the biodegradability test, if that 

test is determined to be adequate for assessing biodegradation potential. Furthermore, the results of the 

Activated Sludge Respiration Inhibition Test (ASRI) determine which biodegradation test is required. If 

the ASRI test EC50 is less than or equal to 20 mg/L, then either the (i) Biodegradation in Activated Sludge 

Study, or (ii) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units, or (iii) the Porous 

Pot Test is required. If the ASRI test EC50 is greater than 20 mg/L, then the applicant must choose either: 

(i) Ready Biodegradability or (ii) a) Biodegradation in Activated Sludge, or b) Simulation Test – Aerobic 

Sewage Treatment: A. Activated Sludge Units, or c) the Porous Pot Test. If the Ready Biodegradability 

study is conducted and the test substance passes the ready biodegradability study, then no further testing is 

required. If, however, the test substance fails the Ready Biodegradability study, then the (i) Biodegradation 

in Activated Sludge, or (ii) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units, or 

(iii) the Porous Pot study is required.
Page 40 of 40

Practical Utility of the Data

1. How will the data be used?

The data will be used to assess potential adverse effects to activated sludge microorganisms. In addition, 

the data will be used to determine whether or not label restrictions are needed. The study will identify the 

inhibitory effect of this chemical on the treatment plant’s microorganisms’ respiration at different 

concentrations of the test substance and will identify the EC50, the effective concentration of the test 

substance at which the respiration rate is 50% of that shown by the control under conditions in this 

guideline. The data will also determine suitable non-inhibitory concentrations to be used in 

biodegradability tests.

2. How could the data impact the Agency’s future decision-making?

If the data indicate a high degree of activated sludge respiration inhibition, a more rigorous test for 

biodegradation in wastewater treatment will be required than the ready biodegradability test. Also, if a 

high degree of respiration inhibition is demonstrated and biodegradation and/or sorption is indicated to be 

negligible, the Agency may require label restrictions or mitigation measures to insure that activated sludge 

microorganisms will not be adversely impacted.