REGISTRATION REVIEW DOCUMENT 

PRODUCT CHEMISTRY, ENVIRONMENTAL FATE AND 

 ECOLOGICAL EFFECTS SUMMARY FOR TETRAKIS 

(HYDROXYMETHYL)PHOSPHONIUM SULFATE 

Important Note on the Chemistry:

Tetrakis (hydroxymethyl) phosphonium sulfate is an organophosphate-like chemical but 

has not been classified within this class of chemicals. Phosphorous is quatnerized in this 

chemical. It was classified as a benign and safe biocide and under EPA’s Toxics Program 

of Green Chemistry, THPS was awarded a Green Chemical Award in 1997 to the parent 

Company Albright & Wilson, now Rhodia, (EPA Document number 744K10003, June 

2010, www.epa.gov). The Agency conducted a number of open literature searches and 

found the following information on Dow Chemical Co. Website: 1) “THPS is 

manufactured in a batch process that involves the chemical reaction of phosphine gas 

with aqueous formaldehyde in the presence of sulfuric acid and water. THPS exists in 

equilibrium with tris (hydroxymethyl)phosphine and methylene glycol. Under 

manufacturing and shipping conditions, the equilibrium strongly favors the formation the 

formation of THPS” (This reference is for the AQUCAR THPS 75 product of Dow). The 

Agency assumes that it is likely to contain formaldehyde as an impurity and it is likely a 

formaldehyde releaser. This is confirmed in a recent publication by Li Ya et al as 

discussed below. 

THPS degrades by the following reaction series: 

[(CH2OH)8 P2)]+2 SO4

-2 -----Æ 2 P(CH2OH)3 (trihydroxymethyl phosphine) + 2HCHO 

(formaldehyde) + SO4

-2 (aq)--------------------------------------------------(1) 

Hence one mole of THPS produces 2 moles of formaldehyde. 

P (CH2OH)3 + H2O ----------------------------P(CH2OH)3O (Phosphine oxide) --------(2) 

(Source: Li,Ya, Saho Shuangxi, Shi, Kaiqi, and Jaing Lan) in the Journal of the Society 

of Leather Technologists and Chemists: July/August 2008: 92(4), pp 167-169. The 

research indicates that in the tanning process of leather, THPS releases formaldehyde, 

and the release of formaldehyde is pH dependent. It was further determined that 

formaldehyde release is controlled by adding hydrogen peroxide during the tanning 

process. 

2 
 Table 1: Use patterns 

Chemical name Use patterns/use sites 

Cytec: CYPHOS B1 

(77%) 

For repackaging and formulating antimicrobial end use 

products in oil field operations and systems, oil drilling muds, 

and packer fluids, recirculating water cooling towers, paper 

and paperboard manufacturing, air conditioning and 

refrigeration’s condensate water systems, air washing systems, 

heat exchanger water systems, industrial processing water, 

industrial fresh water systems, industrial wastewater systems,

fire protection systems, service water and auxiliary systems, 

solution/emulsions, and laboratory equipment water baths. 

TOLCIDE PS75 (75%) Used in air conditioning/refrigeration condensate water 

systems, recirculating commercial/industrial water cooling 

systems, heat exchanger water systems, industrial processing 

water, laboratory equipment water baths, and oil recovering, 

drilling muds packers fluids 

TOLCIDE PS 50A 

(50%) 

Same as CYPHOS B1 

Tolcide PS 200 (20%) Besides CYTEC CYPHOS B1 additional application sites are: 

Gas storage well system, well remediation operations, 

hydrotesting, pipeline pigging and scraping operation 

TOLCIDEW PS70AF 

(70%) 

Same as CYTEC CYPHOS B1 

TOLCIDE PS70A 

(70%) 

Same as CYTEC CYPHOS B1. In addition, Gas storage well 

system, well remediation operations, hydrotesting, pipeline 

pigging and scraping operation 

AQUCAR THPS 75 

(76.5%) 

Same as CYTEC CYPHOS B1. In addition, Gas storage well 

system, well remediation operations, hydrotesting, pipeline 

pigging and scraping 

MAGNACIDE 575S 

(50%) 

Oil filed waters, Drilling muds and workover or completion 

fluids, well stimulation and fracturing 

ACUCAR THPS 75 

MFG (76.5%): 

Same as AQUCAR THPS 75 

ALL-CLEAR End-Use 

Formulation (2.85% 

THPS; 0.43% 

Benzalkonium 

chloride) 

Surface Disinfectant for hard inanimate non-porous surfaces: 

floors, walls, rails, chairs, shower stalls, urinals, bath tubs, and 

non-food contact surfaces, including tables, and counters, 

homes, schools, hospitals, cafeteria, restaurant, offices, 

industrial and commercial buildings, exterior of structures, 

areas of mass gathering such as stadiums, and convention 

centers, or outdoor on vehicles, farm equipment and poultry 

premises 

3 
 

Regulatory History: TBA

Table 2: Registered Active Products for: Tetrakis (hydroxymethyl) phosphonium 

Sulfate 

EPA Reg. 

Number 

Product Name Formulation 

Type 

% Active Ingredient Registrant 

68387-9 CYPHOS B1 

PHOSPHONIUM 

SALT 

Aqueous 

solution 

77.7 (conditionally 

registered 

CYTEC 

Industries, Inc 

464-8127 AQUA THPS 

75FW 

76.6 (Registered) Dow Chemical 

Co. 

464-8126 AQUATHPS 

75 

76.5(Registered) Dow Chemical 

Co. 

33677-3 TOLCIDE 

PS75 

75(Conditionally 

registered) 

Rhodia UK, Ltd

33677-7 TOLCIDE 

PS75LT 

75(Conditionally 

registered) 

Rhodia UK, Ltd

4564-20 TOLCIDE 

PS70A 

70(Conditionally 

registered) 

Rhodia, Inc. 

4564-19 TOLCIDE 

PS70FA 

70(conditionally 

registered) 

Rhodia, Inc 

4564-RA TOLCIDE 

PS50D 

50 (status uncertain) Rhodia Inc 

10707-57 MAGNACIDE 

575S 

50(Conditionally 

registered) 

Baker Petrolite 

Corp 

4564-17 TOLCIDE 

PS50A 

50(Registered) Rhodia Inc. 

33677-6 TOLCIDE 

PS352C 

35(Conditionally 

registered) 

Rhodia UK Ltd 

4564-18 TOLCIDE 

PS20A 

20(Registered) Rhodia Inc. 

4564-15 TOLCIDE 

PS200 

20(Conditionally 

Registered) 

Rhodia Inc. 

82932-1 ALL CLEAR 3(Registered) KIDDE Fire 

Fighting 

82932-1 ALL CLEAR 0.5(Registered) 

contains ADBAC as a 

second active 

KIDDE Fire 

Fighting 

Based on the label searches and label analysis, the use sites/use patterns of THPS are as 

follows: 

4 
For repackaging and formulating antimicrobial end use products in oil field operations 

and systems, oil drilling muds, and packer fluids, recirculating water cooling towers, 

paper and paperboard manufacturing, air conditioning and refrigeration’s condensate 

water systems, air washing systems, heat exchanger water systems, industrial processing 

water, industrial fresh water systems, industrial wastewater systems, fire protection 

systems, service water and auxiliary systems, solution/emulsions, and laboratory 

equipment water baths. Surface disinfectant for hard inanimate non-porous surfaces 

Table 3. Chemical Identity 

Common Name THPS 

Chemical Name Tetrakis(hydroxymethyl)phosphonium sulfate 

IUPAC Name Same 

Molecular Weight 406.28 

PC Code 129058 

CAS Registry Number 55566-30-8 

Molecular Formula/Empirical 

Formula 

C8H24 O12 P2S 

Registration Review Case No. 5034 

Registration Review Case Name THPS 

Classification: Organic Derivative of quat. Phosphorous 

Structure: 

 

 

Science Findings:

The following tables summarize the science data for each discipline, and lists some data 

gaps. 

5 
Product Chemistry Summary

Table 4: Physical and Chemical Properties of Tetrakis(hydroxymethyl) 

phosphonium sulfate

Guideline 

No. 

Physical and Chemical Properties Value 

830.1550 Product identity and composition Refer to Table 2 

830.1600 Description of materials used to 

produce the product 

CBI 

830.1620 Description of production process CBI 

830.1650 Description of formulation process CBI 

830.1670 Discussion of formation of impurities CBI 

830.1700 Preliminary analysis CBI 

830.1750 Certified limits CBI 

830.1800 Enforcement analytical method CBI 

830.1900 Submittal of samples CBI 

830.6302 Color Colorless; MRID: 466599-022

830.6303 Physical State Viscous liquid at 20 o C; MRID:466599-02 

830.6304 Odor Antiseptic Odor: MRID: 466599-02 

830.6313 Stability to sunlight, normal and 

elevated temperature 

N/A: Product is not expected to come in contact 

with either metals or metal ions during storage: 

MRID: 466599-02 

830.6314 Oxidation/Reduction: Chemical 

Incompatibility 

Compatible with: water, 10% monoammonium 

phosphate solution, zinc granules, and kerosene. 

Incompatible with10% potassium permanganate 

solution. MRID: 466599-02 

830.6315 Flammability 

Flash Point 

Product is water-based and does not contain 

flammable liquids. MRID: 466599-02 

830.6316 Explodability Not thermal or shock explosive: MRID: 466599-02 

830.6317 Storage Stability No significant change in physical or chemical 

change during storage at 25 o

 C:MRID: 466599-02 

830.6319 Miscibility N/A> product is not intended to be diluted with 

petroleum solvents. MRID: 466599-02 

830.6320 Corrosion Characteristic No signs of corrosion or degradation of translucent 

plastic HDPE bottle during storage at 25 o C for12 

months. MRID: 466599-02 

830.6321 Dielectric breakdown voltage N/A; product is not intended to be used around 

electrical equipment; MRID: 466599-02 

830.7000 pH 3.02 25 o C; MRID:466599-02 

830.7050 UV/Visible absorption spectra Not reported: 

830.7100 Viscosity 38.6 mm2 /s at 20 o C; 18.5 mm2 /s at 40 o C; 

MRID: 466599-02 

830.7200 Melting Point N/A; product is manufactured in situ and 

therefore it is never isolated in a form suitable for 

testing as the technical grade or purified active 

ingredient; MRID: 466599-02; MP for the 

technical: 298.83 o C (EPI Suite) 

830.7220 Boiling point N/A; product is manufactured in situ and therefore 

it is never isolated in a form suitable for testing as 

the technical grade or purified active ingredient; 

MRID: 466599-02; BP for the technical:

830.7300 Density/ Bulk density 1.41 g/cc 20 o C: MRID: 466599-02 

830.7370 Dissociation Constants in water Product has no acid, base or alcoholic 

6 
Guideline 

No. 

Physical and Chemical Properties Value 

functionality; MRID: 466599-02

830.7520 Particle size NA 

830.7550 Octanol/water partition coefficient 

(KOW) (Log Kow ) 

 logKo/w: ~ -4.42 MRID: 466599-02 

830.7840 Solubility in water N/A: product is manufactured in situ and therefore 

is never isolated in a form suitable for testing as 

purified active ingredient; MRID: 466599-02 

830-7840 Solubility in organic solvents in g/100 

ml 

 Not reported; MRID: 466599-02

830.7950 Vapor pressure 1.27 x 10-5 mm Hg at 25 o C; MRID: 466599-02 

Product Chemistry: Data Gaps

830.7840: Solubility in organic solvents in g/100 ml 

Environmental Fate and Transport Data Summary:

Table 4 Summarizes the Environmental Fate Data Summary for THPS (based on test 

guidelines and open literature) 

 Table 4 

Environmental Fate Profile of Tetrakis (hydroxymethyl) phosphonium sulfate (THPS) 

Guideline #/Study 

Type 

Results Reference 

835.2120/ 

Hydrolysis 

THPS hydrolyzed in sterile 

aqueous/buffered medium 

and observed half lives are: 

131 days at pH 5, 72 days 

at pH 7, and 7 days at pH 

9. At all pH’s the 

degradation products 

identified (through NMR 

studies) were: 

trishydroxymethyl 

phosphine (THP), and in 

turn THP hydrolyzes to tris 

hydroxymethyl phosphine 

oxide (THPO). 

THPS is, therefore stable 

under abiotic conditions at 

pH’s 5, and 7 (beyond 

thirty days), and can be 

regarded as persistent at 

pH’s 5, and 7. It degrades 

fast at pH 9. In all cases 

MRID#: 422363343 

J. O’Connor: 

Tetrakis(hydroxymethyl)Phosphonium 

Sulfate (THPS): Determination of the 

Hydrolysis as a Function of pH: Lab 

Project #: 91/0737, prepared by Life 

Science Research Ltd; pp 78 

Purity of the pesticide used for the 

study: 75%. 

7 
same degradation products 

are produced: THP, and 

THPO. 

The study is acceptable 

Non-Guideline 

Study: 

Mechanistic 

Modeling of 

Anaerobic THPS 

Biocide 

Degradation 

Under Alkaline 

Conditions. 

The review was 

done internally, 

and no DER was 

produced. 

This study showed that that 

the degradation of THPS in 

seawater was strongly 

dependent on temperature, 

and pH, that is, it increases 

as the pH and temperature 

increased. The study was 

conducted in Persian Gulf 

sea water in the presence 

of steel coupons. 

In Persian Gulf seawater 

(at pH 8.1, and temperature 

8.1) the half life was about 

5 days (initial 

concentration of THPS was 

100 ppm); In artificial 

seawater at pH 7.9, and 

temperature 31 C, the half 

life was about 6 days 

August 2009, Kahli Zhao, Jie Wen, 

Tingyue Gu, Ardjan Kopliku, and 

Ivan Cruz 

Materials Performance, pp 62-664

EPA’s Screening Model Program EPI SUITE5 (version 4.1) lists the following product 

chemistry and environmental characteristics for THPS: 

1. Log Kow = -20.39 

2. Henry Law Constant = 1.7 x10-6 atm-m3 /mole 

3. Half-life in air (estimated against hydroxy radical interaction) = 4.706 hours 

4. Log Koc = 2.1533 

5. Biodegradation Predictions: a) linear model: biodegrades fast; b) non-linear 

biodegradation: biodegrades fast; c) ultimate biodegradation time frame: degrades 

within days/weeks; d) primary biodegradation timeframe: hours/days; MITI linear 

model prediction: biodegrades fast; e) MITI-non-linear model predictions: 

biodegrades fast; f) anaerobic model prediction: biodegrades fast; g) ready 

biodegradability: YES. 

Environmental Fate and Transport Conclusions: 

THPS appear to be stable and persistent under abiotic conditions at pHs 5, and 7 with half 

lives greater than 30 days. However, at pHs above 8 (basic conditions), it degrades within 

7 days. The degradation products have been identified as: trishydroxymethyl phosphine 

(THP) and subsequently into trishydroxymethyl phosphine oxide (THPO) 8. Open 

literature study also shows that THPS degrades in artificial seawater (ph 7.9) with a half 

life of 6 days. EPA’s EPI Suite model indicates that THPS is easily biodegradable (fast 

8 
biodegradability) ultimate biodegradability is fast as well. Primary biodegradation half 

life is estimated at hours/days. 

Its estimated Log Kow varies from -4.42 to -20.39; it is not likely to bioaccumulate in the 

aquatic organisms. It does not appear to be persistent in air as its estimated half life 

(measured against hydroxyl radical) is less than 5 hours. The major uses of this pesticides 

are outdoor, and it is hydrolytically stable, a number of environmental fate studies are 

triggered as the exposure form these uses will be in soils and water. Leaching and 

adsorption/desorption studies will clearly show if the chemical easily migrates into the 

soils and sediments and Kd values determined from adsorption/desorption studies will 

show if the binding with soils is strong or weak. Metabolism studies and 

biodegradability will show if the pesticide degrades in actual environmental medium. All 

the studies listed below are required for these scenarios. 

Environmental Fate and Transport Data Gaps 

Its use patterns involve recirculating cooling water systems and industrial wastewater 

treatments. The Agency anticipates requiring the following environmental fate studies: 

1. 835.2240: Aquatic Photodegradation at pH 7 

2. 835.1230: Leaching study from soils (migration) 

3. 835.1240: Adsorption/Desorption Study (Kd) 

4. 835.4300: Aerobic Aquatic Metabolism study 

5. 835.4400: Anaerobic Aquatic Metabolism Study 

6. 835.3110: Ready Biodegradability 

Ecological Effects Data Summary:

Table 5 summarizes the eco-toxicity data that AD has in its data base. 

 Table 5 

 Ecotoxicity Data6,7

Guideline 

#/Study type 

MRID#/Reference 

Information/Study 

Classification 

Dosing/Organism 

Information 

Results 

850.1035: 

Estuarine/marine 

acute toxicity 

(Mysid Shrimp) 

MRID#: 442796-01 

Boeri, et al (1995) 

Acute toxicity of THPS to 

Mysid, Mysidopsis hahia 

under flow through 

conditions (final report) 

Core: Acceptable.

Guideline 

THPS administered 

at 0, 1.3, 2.3, 3.6, 

6.1, and 10 ppm 

2 replicates by 20 

test organisms/level 

Purity: 76.8% 

LC50 = 7.30 

ppm; 

NOEAC= 3.49 

ppm 

Moderately 

toxic 

850.55: Bivalve 

acute toxicity test 

MRID#: 442796-03 

Boeri et al: Acute flow 

through Mulluse Shell 

Deposition Test with THPS 

THPS was 

administered at 0, 

0.26, 0.44, 0.72, 1.2 

and 2.00 ppm 

EC50 = 1.6 

ppm; 

NOEAL = 

0.67 ppm 

9 
(final report) 

Core: Accepted/ Guideline

20 test 

organisms/level 

Purity: 76.8% 

Moderately 

toxic 

850.1075: 

Fish acute 

toxicity test 

(Bluegill) 

MRID#: 422363-25 

Jenkins, w (1989): 

THPS: acute toxicity to 

Bluegill Sunfish 

Core/Acceptable; 

Guideline 

THPS administered 

for 96 hours at 

0,22.7, 37.8, 63, 

105, and 175 mg/L 

10 fish/treatment 

level 

Purity: 75% 

96 hour LC50

= 98 mg/L 

The test 

material is 

slightly toxic 

to Bluegill 

sunfish 

850.1075: fish 

acute toxicity test 

(Rainbow Trout) 

MRID 422363-24 

Jenkins, W (1990) 

THPS acute toxicity to 

Rainbow Trout 

Guideline/Core/Acceptable

THPS administered 

for 96 hours at 

0,18.1, 30.2, 50.4, 

84, and 140 mg/L 

10 fish/treatment 

level 

Purity: 75% 

96 hour LC50 = 

94 mg/L 

The test 

material is 

slightly toxic 

to Rainbow 

Trout 

850.1075: Fish 

acute toxicity test 

(Sheepshead 

Minnow) 

MRID#: 442796-02 

Boeri et al. (1995) 

Actue toxicity of THPS to 

the Sheepshead Minnow 

under flow-through 

conditions 

Core/Acceptable/Guideline

THPS administered 

for 96 hours at 0, 13, 

22, 36, 60, and 100 

mg/L 

20 replicates of 20 

fish/treatment level 

Purity 76.8 % 

LC50 = 72 ppm; 

NOEAL = 41 

ppm 

Slightly toxic 

850.2100: 

Avian Oral 

Toxicity test 

(Mallard Duck) 

MRID#: 422363-21 

Roberts, N (1987) 

THPS: acute oral toxicity 

(LD50 )of DP 435 to the 

Mallard Duck 

Acceptable-guideline/Core 

THPS administered 

at 0, 70, 126, 227, 

408 and 735 mg/Kg 

5 Mallard 

Duck/sex/dose 

Purity 75% 

LD50 = 324 

mg/kg; 

NOEAL =70 

mg/Kg 

THPS is 

moderately 

toxic to 

Mallard 

Ducklings 

850.2200: Avian 

acute toxicity test 

(Mallard duck) 

MRID#: 422363-22: 

Roberts, N (1987);THPS: 

dietary toxicity (LC50 ) of 

DP 435 to the Mallard Duck 

Acceptable-guideline/Core 

THPS administered 

at 0, 300, 570, 1083, 

2058, 3910, and 

7428 ppm 

10 ducks/dose 

Purity: 75% 

LC50 = 1313 

ppm; NOEAC 

not achieved 

due to all dose 

levels had 

reduced food 

consumption 

and decreased 

body weight 

gains 

THPS may be 

classified as 

slightly toxic 

10 
to Mallard 

Ducks 

850.2200: Avian 

acute dietary 

toxicity test 

(Bobwhite Quail) 

MRID#: 422363-23 

Roberts, N (1987) 

THPS dietary toxicity 

(LC50) of DP 435 to the Bob 

white Quail 

Acceptable-guideline/Core 

THPS administered 

at 162.5, 325, 650, 

1300, 2600, 5200 

ppm 

10 chicks/test level 

Purity: 75% 

Reduced body 

weight gain 

THPS is 

slightly toxic 

to Bobwhite 

Quail 

Ecotoxicity Conclusions 

THPS have been determined to show moderate acute toxicity to estuarine/marine 

organisms like Mysid Shrimp as well as to bivalves. THPS shows slight to moderate 

acute toxicity to Bluegill Sunfish and Rainbow Trout while it is only slightly toxic to 

Sheephead Minnow. For Avian Toxicity Testing, it shows moderate oral toxicity to 

Mallard Duck while only slight dietary acute toxicity is observed with Mallard Duck and 

Bobwhite Quail. As the uses of this pesticide are in the outdoors, a number ecotoxicity 

are triggered as listed below. 

Table 5 provides the toxicity categories for terrestrial and aquatic organisms based on 

end points: 

 Table 5

 Ecotoxicty Categories 

Birds Mammals 

LD50(mg/kg) LD50(ppm) 

 Category Aquatic organisms 

LC50 (ppm); EC50(ppm) 

<10 < 50 Very highly toxic < 0.1 

10-50 50-500 Highly toxic 0.1-1 

51-500 501-1000 Moderately toxic > 1-10 

501-2000 1001-5000 Slightly toxic >10-100 

>2000 >5000 Practically non-toxic > 100 

Ecotoxicity Data Gaps: 

The Agency anticipates requiring the following ecotoxicity studies: 

1. 850.1010: Acute Freshwater Invertebrates Toxicity 

2. 850.1300/ 850.1350: Acute Invertebrate Life-Cycle 

3. 850.1400: Fish Early Life Cycle 

4. 850.4400: Aquatic Plant Growth (Aquatic Vascular Plant), tier II-dose Response 

5. 850.5400: Aquatic growth, Tier II, four species. 

Endangered Species Determination: 

The Agency has not conducted an ecological risk assessment that supports a complete 

endangered species determination. The ecological risk assessment planned during the 

11 
registration review will allow the Agency to determine whether THPS’s use has “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 US Fish and Wildlife Service and/or National Marine Fisheries Services as 

appropriate 

BIBLIOGRAPHY FOR: PRODUCT CHEMISTRY, ENVIRONMENTAL FATE 

AND TRANSPORT, AND ECO-EFFECTS 

1. ( Li,Y, saho Shuanggxi, Shi, Kaiqi, and Jaing Lan) in the Journal of the Society of 

Leather Technologists and Chemists: July/August 2008: 92(4), pp 167-169. 

2. MRID: 466599-02: P/chem. properties of THPS. 

3. MRID#: 42236334 J. O’Connor: Tetrakis(hydroxymethyl)Phosphonium Sulfate 

(THPS): Determination of the Hydrolysis as a Function of pH: Lab Project #: 

91/0737, prepared by Life Science Research Ltd; pp 78 

4. August 2009, Kahli Zhao, Jie Wen, Tingyue Gu, Ardjan Kopliku, and Ivan Cruz 

Materials Performance, pp 62-66

5. EPI Suite, version 4.1 

6. RASSB Memo from Allen Vaughan to Norm Cook: (2002) 

7. RASSB Memo from Rick Petrie to Norm Cook: (2002) 

8. Product Safety Assessment AQUCAR THPS 75 Water Treatment Microbiocide: 

http://www.dow.com/homepage/term.asp. Created: July 26, 2010 

12 
 APPENDIX 

 DATA JUSTIFICATIONS FOR THPS 

 ECOTOXICITY 

Guideline Number: 850.5400 

Study Title: Algal toxicity (Tier II)

Rationale for Requiring the Data

As part of a Tier I risk assessment, one indicator plant species is tested for phytotoxicity. This study 

would allow the Agency to categorize THPS as toxic or non-toxic to plants. If toxic, additional higher 

tier plant tests would be needed. An endangered species assessment for endangered or threatened plants 

is not possible without this study.

Practical Utility of the Data

1. How will the data be used? 

This study would be used to evaluate the toxicity of THPS to non-target plants in terrestrial and aquatic 

ecosystems.

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

Adverse effects to non-target plants in terrestrial and aquatic ecosystems may result in mitigation to 

protect species at risk. Mitigation might include reduced label dosages, neutralization of effluents prior 

to discharge into water, restrictions on use in sensitive ecosystems or where endangered species are 

present, or other mitigation measures. 

3. What is triggering the need for this data?

Increased concern from state regulators and the public to evaluate impacts on WWTP operations, 

endangered species, and persistence in the environment, since initial registration, have triggered the need 

for this study. Green algae are critical to ecosystem health and productivity. 

13 
Guideline Number: 850.1075 

Data Requirement: Acute Fish Toxicity (estuarine/marine)

Rationale for Requiring the Data 

Sport fishing and commercial fishing have a high impact on the United States economy. The acute 

toxicity tests with estuarine/marine fish are designed to measure mortality during short-term (96-h) 

aquatic exposure to a range of concentrations of the pesticide in water. The preferred test species is 

Atlantic silverside (Menidia menidia) for salt water.

Practical Utility of the Data 

1. How will the data be used? 

Data would be used to determine concentration-response curves and calculate LC50's (with 95% 

confidence intervals) for 24, 48, 72, and 96 h. Additionally, a NOEC for 96 h is reported. The 

results from these studies may also provide information for a concentration-selection rationale for 

fish early-life stage study (OPPTS 850.1400) and the fish life cycle study (OPPTS 850.1500). 

2. How could the data affect the risk assessment? 

There are many estuarine/marine fish species that are listed as threatened and endangered in the 

United States. Although the Atlantic silverside is the preferred species, the sheepshead minnow is 

considered a surrogate species to represent all marine/estuarine fish species in the risk assessment 

process. As part of the acute risk assessment for aquatic animals, the lowest EC50 or LC50 for 

estuarine/marine fish is used in the RQ equation. An acute RQ > 0.5 would indicate an acute LOC, 

defined as the potential for acute risk to non-target organisms which may warrant regulatory action 

in addition to restricted use classification. An acute RQ > 0.1 would result in an acute restricted use 

LOC, defined as the potential for acute risk to non-target organisms, which may be mitigated 

through restricted use classification. An acute RQ > 0.05 would fall under the LOC for acute 

endangered species. 

3. What is triggering the need for this data? 

Data are needed in order to conduct an ecological risk assessment for the proposed use of THPS and 

determine the acute toxicity of THPS to estuarine/marine fish.

Guideline Number: 850.1400 

Study Title: Freshwater Fish Early Life Stage using Rainbow Trout, Fathead Minnow, Zebra Fish, 

or Rice Fish 

Rationale for Requiring the Data 

Fish early-life stage study is less expensive to conduct than the full life cycle study. Fish early-life 

stage study gives us some indications if the pesticide is toxic to fish reproduction and survival. In the 

fish early-life stage study, fertilized eggs are placed in test chambers and exposed to the pesticide in 

water at least until all the control fish are free-feeding. Lethal and sublethal effects are assessed and 

compared with control values to determine the LOEC and the NOEC.

Practical Utility of the Data 

1. What is the value of the study? 

Data are needed in order to conduct an ecological risk assessment for the proposed use of THPS and 

determine the effects of THPS on fish development and survival during early life stages.

2. How will the data be used? 

The data are used to determine embryo hatch rate, time to hatch, time to swim-up, growth (length and 

weight), and any clinical or pathology findings 

3. How could the data affect the risk assessment?

As part of the chronic risk assessment for aquatic animals, the lowest NOEC for estuarine/marine fish 

14 
is used in the RQ equation. A chronic LOC is defined by an RQ > 1, and would indicate that there is 

the potential for chronic risk that may warrant regulatory action and that endangered species may 

potentially be affected through chronic exposure. 

Guideline Number: 850.1350 

Study Title: Marine Aquatic Invertebrate Mysidopsis bahia

Rationale for Requiring the Data 

Invertebrates serve as food for fish, birds, crustaceans, and even whales. The protection of non-target 

invertebrates is essential to the food chain in any healthy ecosystem. The value in the Daphnid (850.1300) 

and Mysid (850.1350) chronic toxicity tests are that they provide information on the effects of pesticides on 

mortality, growth, and reproduction over a longer term (21 days for Daphnids and 28 days for Mysids) 

compared to acute studies. Data are obtained from the first generation (G1) and the second generation (G2), 

thus allowing examination of the complete invertebrate life cycle for toxicity. 

Practical Utility of the Data 

1. What is the value of the study? 

Data are needed in order to conduct an ecological risk assessment for the use of THPS to determine the 

chronic toxicity of THPS to freshwater and marine invertebrates using life-cycle studies. 

2. How will the data be used? 

Data would be used to calculate LC50’s for mortality, EC50’s for growth, a NOAEC, and a MATC 

(maximum acceptable toxicant concentration). The data would allow the Agency to determine chronic 

effects, including effects on reproductive success and growth, to freshwater and marine invertebrates from 

water column exposure to THPS 

.

3. How could the data affect the risk assessment?

Because acute toxicity data alone are not a reliable indicator of chronic toxicity, chronic toxicity data are also 

required. The Agency cannot make the assumption that a chemical is not chronically toxic at much lower 

concentrations than some ratio of the LC50 value would suggest. The results 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 organisms which feed on them. Daphnia magna (for fresh water) and 

Mysidopsis bahia (for salt water) are used to represent all invertebrate species living in the water column in 

the risk assessment process. Additionally, the use of the most sensitive species ensures the protection of other 

species within that taxon. As part of the chronic risk assessment for aquatic animals, the lowest NOAEC for 

estuarine/marine invertebrates is used in the RQ equation. A chronic LOC is defined by an RQ > 1, and 

would indicate that there is the potential for chronic risk that may warrant regulatory action and that 

endangered species may potentially be affected through chronic exposure. 

Guideline Number: 850.4400 

Study Title: Aquatic Macrophyte Study using Lemna gibba

Rationale for Requiring the Data 

Aquatic plants are essential components of any healthy ecosystem. Plants provide food, shelter, and 

oxygen to animal species. Lemna represents floating aquatic macrophytes. As part of a Tier I risk 

assessment, one freshwater aquatic plant indicator species, (Lemna gibba or L. minor), is exposed to a 

range of concentrations of THPS in fresh water to measure phytotoxicity.

Practical Utility of the Data 

1. What is the value of the study? 

15 
Data are needed in order to conduct an ecological risk assessment for the uses of THPS and determine 

its effects on aquatic plants because they are critical to ecosystem health and productivity.

2. How will the data be used? 

This study would be used to evaluate the toxicity of THPS to non-target plants in aquatic ecosystems. 

Data from these studies would be used to plot concentration response curves for total frond number, 

growth rate (as number of fronds per day), and mortality (percentage of dead fronds to total number of 

fronds). EC05s, EC50s, and EC90s would be calculated from the curves. Tier II (definitive) testing is 

not required if Tier I testing results in an EC50 greater than 1000 mg/L or less than the analytical 

detection limit. Tier II tests may also include endpoints such as measurements of chlorophyll 

pigments, biomass, and more detailed observations of frond appearance (i.e., decrease in size, necrosis, 

chlorosis, or sinking). 

3. How could the data affect the risk assessment?

Lemna spp. are used to represent all aquatic plants in the risk assessment process. Adverse effects to 

non-target plants in aquatic ecosystems may result in mitigation to protect species at risk. Mitigation 

might include reduced label dosages, neutralization of effluents prior to discharge into water, 

restrictions on use in sensitive ecosystems or where endangered species are present, or other 

mitigation measures. 

Aquatic plants may be affected when THPS is used as an antimicrobial. If EPA is unable to evaluate 

the potential risks to aquatic plants associated with the uses of THPS, these risks must be presumed. 

As part of the risk assessment for aquatic vascular plants, the lowest EC50 is used in the RQ equation. 

The LOC for endangered and non- endangered plants is defined as a RQ > 1.

16 
Guideline Number: 850.5400 

Study Title: Aquatic Plants (4) using Selenastrum capricornutum (green algae), Anabaena flos-aquae

(blue-green cyanobacteria), Navicula pelliculosa (freshwater diatom), and Skeletonema costatum

(marine diatom) 

Rationale for Requiring the Data 

As part of a Tier I risk assessment, one indicator plant species is tested for phytotoxicity. This study 

would allow the Agency to categorize THPS as toxic or non-toxic to plants. If toxic, additional higher 

tier plant tests would be needed. An endangered species assessment for endangered or threatened plants 

is not possible without this study.

Practical Utility of the Data 

1. What is the value of the study? 

Increased concern from state regulators and the public to evaluate impacts on WWTP operations, 

endangered species, and persistence in the environment, since initial registration, have triggered the need 

for this study. Green algae are critical to ecosystem health and productivity.

2. How will the data be used? 

This study would be used to evaluate the toxicity of THPS to non-target plants in terrestrial and aquatic 

ecosystems.

3. How could the data affect the risk assessment?

Adverse effects to non-target plants in terrestrial and aquatic ecosystems may result in mitigation to 

protect species at risk. Mitigation might include reduced label dosages, neutralization of effluents prior to 

discharge into water, restrictions on use in sensitive ecosystems or where endangered species are present, 

or other mitigation measures. 

Guideline Number: 850.1010 

Study Title: Acute Aquatic Invertebrate 

Rationale for Requiring the Data 

This study will allow the Agency to determine the toxicity of THPS to freshwater daphnids. An 

endangered species assessment for endangered or threatened freshwater daphnids is not possible 

without this study. Therefore, this study is required. 

Practical Utility of the Data 

1. How did the Agency make its re-registration decision without this data?

The Agency imposed risk mitigation through labeling changes as an interim measure. 

2. How will the data be used? 

The study will be used for hazard labeling in the event a spill of manufacturing use product occurs. 

This study will be used to generate a freshwater invertebrate endpoint so that the Agency can evaluate 

the toxicity of m-Cresol to non-target and endangered/threatened freshwater daphnids in freshwater 

aquatic ecosystems. 

17 
 

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

If the acute freshwater fish toxicity is 1.0 mg/L or less, the label must state: “This pesticide is toxic to 

fish.” A freshwater fish endpoint will allow the Agency to determine if endangered or threatened 

species are at risk or if freshwater fish are impacted after residues pass through waste water treatment 

plants into surface waters. Mitigation might include reduced label dosages, neutralization of effluents 

prior to discharge into water, restrictions on use in sensitive ecosystems or where endangered species 

are present, or other mitigation measures which require refined scientific assessments. 

Guideline Number: 850.1300 

Data Requirement: Aquatic invertebrate chronic NOAEC using Daphnia magna 

Guideline Number: 850.1350 

Data Requirement: Aquatic invertebrate chronic NOAEC using mysid shrimp

Rationale for Requiring the Data 

Invertebrates serve as food for fish, birds, crustaceans, and even whales. The protection of nontarget invertebrates is essential to the food chain in any healthy ecosystem. The value in the Daphnid 

(850.1300) and Mysid (850.1350) chronic toxicity tests are that they provide information on the 

effects of pesticides on mortality, growth, and reproduction over a longer term (21 days for Daphnids 

and 28 days for Mysids) compared to acute studies. Data are obtained from the first generation (G1) 

and the second generation (G2), thus allowing examination of the complete invertebrate life cycle for 

toxicity.

Practical Utility of the Data 

1. How will the data be used? 

Data would be used to calculate LC50's for mortality, EC50's for growth, a NOEC, and a MATC 

(maximum acceptable toxicant concentration). The data would allow the Agency to determine 

chronic effects, including effects on reproductive success and growth, to freshwater and marine 

invertebrates from water column exposure to THPS.

2. How could the data affect the risk assessment? 

Because acute toxicity data alone are not a reliable indicator of chronic toxicity, chronic toxicity 

data are also required. The Agency cannot make the assumption that a chemical is not chronically 

toxic at much lower concentrations than some ratio of the LC50 value would suggest. The results 

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 organisms which 

feed on them. Daphnia magna (for fresh water) and Mysidopsis bahia (for salt water) are used to 

represent all invertebrate species living in the water column in the risk assessment process. 

Additionally, the use of the most sensitive species ensures the protection of other species within that 

taxon. As part of the chronic risk assessment for aquatic animals, the lowest NOEC for 

estuarine/marine invertebrates is used in the RQ equation. A chronic LOC is defined by an RQ > 1, 

and would indicate that there is the potential for chronic risk that may warrant regulatory action and 

that endangered species may potentially be affected through chronic exposure. 

3. What is triggering the need for this data? 

Data are needed in order to conduct an ecological risk assessment for the proposed use of THPS as a 

wood preservative and determine the chronic toxicity of THPS to freshwater and marine invertebrates 

using life-cycle studies. 

18 
 PRODUCT CHEMISTRY 

 DATA JUSTIFICATIONS FOR THPS 

Guideline Number: 830.7840xxxx 

Study Title: Solubility in Organic Solvents in g/100 Ml 

Rationale for Requiring the Data 

Pesticides, at use level are not necessarily soluble in water, and hence it is important for the agency to know 

the solubility in other solvents. The Agency has been asking this data for agricultural pesticides routinely. 

OECD also requires this data. This data will harmonize the data set for all major agencies 

Practical Utility of the Data 

What is the value of the study? 

It is part of the product chemistry data requirements (830 Series), and is needed to complete the 

database for product characteristics of THPS 

2. How will the data be used? 

This data will help the Agency to ascertain that this chemical is stable in some commonly available 

solvents, other than water. Also it will help the Agency to know that no unstable entities (dangerous 

or hazardous) are formed by this pesticide in organic solvents. 

3. How could the data affect the risk assessment?

The Agency would want to ascertain that risk studies are conducted properly in the presence of the right 

solvent (the solvent used when the pesticide is applied). The data can then be used for risk assessments.

19 
 ENVIRONMENTAL FATE AND TRANSPORT 

 DATA JUSTIFICATIONS 

Guideline Number: 835.3110 

Data Requirement: Ready Biodegradability

Rationale for Requiring the Data 

The ready biodegradability study would enable the Agency to determine the likelihood that the 

antimicrobial pesticide of biodegrading in aquatic environments under aerobic conditions.

Practical Utility of the Data 

1. How would the data be used? 

The results from the data would be used to determine the rate and extent of aerobic biodegradation 

of THPS when it is released into aquatic environments and would help establish if THPS is stable or 

not stable under real environmental conditions. 

2. How could the data affect the risk assessment? 

If the result shows low biodegradability then, THPS would occur in significant quantities in WWTP 

effluents (water and biosolids) and in environmental compartments (e.g., surface waters) such that 

potential adverse effects to nontarget organisms, found in such environmental compartments, may 

occur. 

3. What is triggering the need for this data? 

Data are needed to conduct environmental fate assessment and to determine the ready biodegradability 

of THPS

20 
Guideline Number: 835.2240 

Data Requirement: Photodegradation in water

Rationale for Requiring the Data 

Biocides introduced into aqueous systems in the environment can undergo photolytic transformation 

by sunlight. Results from the photolysis study will indicate the stability and persistence of THPS 

and potential degrades in an aquatic environment when exposed to sunlight. For outdoor wood 

preservative uses THPS can reach surface water through direct contact or discharge to WWTPs. 

THPS may also reach surface water or groundwater through run-off or leaching processes. The 

Agency will evaluate the potential risks of concern.

Practical Utility of the Data 

1. How will the data be used? 

The data would establish the significance of chemical photolysis as a route for degradation and 

identify, if possible, the photolytic degradation products formed that may adversely affect non-target 

organisms and may contaminate water and food source of aquatic organisms. The data would also 

help establish the photolytic halflife of THPS and possibly degrades, and assist in developing a degradation pathway. 

2. How could the data affect the risk assessment? 

The results of photolysis data would indicate if THPS is persistent or if it degrades into degradation 

products that may adversely affect non-target organisms and may contaminate their food. The 

results of the photolysis data would expand the understanding of the results of the hydrolysis data 

since environmental aquatic conditions usually involve exposure to sunlight. 

3. What is triggering the need for this data? 

Aqueous photo-degradation data is needed to conduct the fate assessment to support indoor and 

outdoor wood preservative uses for THPS.

21 
Guideline Number: 835.4300 

Data Requirement: Aerobic aquatic metabolism

Rationale for Requiring the Data 

The purpose of an aerobic aquatic metabolism study is to determine the nature and extent of 

microbial degradation under aerobic conditions in water/sediment systems, during the period of 

dispersal of the biocide throughout the aquatic environment, and to characterize the formation and 

decline of degrades. This information will determine the persistence and concentrations of THPS 

and potential degrades over time in representative aerobic water/sediment systems. The results will 

indicate the potential for THPS to contaminate the aquatic environment that may come in contact 

with the preserved wood since biocide residues may be taken up by irrigated crops and passed on to 

other parts of the aquatic food web. The Agency will evaluate the potential risks of concern.

Practical Utility of the Data 

1. How would the data be used? 

The data would establish the significance of aerobic aquatic microbial degradation of THPS as a 

route for degradation and identify, if possible, the degradation products formed that may adversely 

affect non-target organisms and may contaminate water and food sources of aquatic organisms. 

The data would also help establish the aerobic aquatic microbial half-life of THPS in 

water/sediment systems, and possibly it's degrades, and assist in developing a degradation pathway. 

2. How could the data affect the risk assessment? 

The results would indicate the nature and extent of formation and decline under aerobic aquatic 

conditions of THPS and its degradates that may be taken up by irrigated crops and passed on to 

other parts of the aquatic food web, and would facilitate assessment of potential disposal problems. 

The study helps to determine the degradation rate (half-life) of THPS in the presence of 

microorganisms in different natural water/sediment systems and determines what metabolites are 

formed under aerobic (oxygen-rich) conditions in the laboratory. 

3. What is triggering the need for this data? 

Aerobic aquatic metabolism data is needed to conduct the fate assessment to support indoor and 

outdoor wood preservative uses for THPS.

22 
Guideline Number: 835.4400 

Data Requirement: Anaerobic aquatic metabolism

Rationale for Requiring the Data 

The purpose of an anaerobic aquatic metabolism study is to determine the nature and extent of 

microbial degradation under anaerobic conditions in water/sediment systems (hydrosoils), during the 

period of dispersal of the biocide throughout the aquatic environment, and to characterize the 

formation and decline of degradates. This information will determine the persistence and 

concentrations of THPS and potential degradates over time in representative anaerobic 

water/sediment systems. The results will indicate the potential for THPS to contaminate the aquatic 

environment that may come in contact with the preserved wood since biocide residues may be taken 

up by irrigated crops and passed on to other parts of the aquatic food web. Additionally, anaerobic 

conditions are more likely to prevail where biocides are found in aquatic environments than in 

strictly terrestrial environments. The Agency will evaluate the potential risks of concern.

Practical Utility of the Data 

1. How would the data be used? 

The data would establish the significance of anaerobic aquatic microbial degradation of biobor as a 

route for degradation and identify, if possible, the degradation products formed that may adversely 

affect non-target organisms and may contaminate water and food sources of aquatic organisms. 

The data would also help establish the anaerobic aquatic microbial half-life of biobor in 

water/sediment systems, and possibly its degradates and, assist in developing a degradation 

pathway. 

2. How could the data affect the risk assessment? 

The results would indicate the nature and extent of formation and decline under anaerobic aquatic 

conditions of THPS and its degradates that may be taken up by irrigated crops and passed on to 

other parts of the aquatic food web, and would facilitate assessment of potential disposal problems. 

The study helps to determine the degradation rate (half-life) of THPS in the presence of 

microorganisms in different natural water/sediment systems and determines what metabolites are 

formed under anaerobic (oxygen-poor) conditions in the laboratory. 

3. What is triggering the need for this data? 

Anaerobic aquatic metabolism data is needed to conduct the fate assessment to support indoor and 

outdoor wood preservative uses for THPS.

23 
Guideline Number: 835.1240 

Data Requirement: Leaching and adsorption/desorption

Rationale for Requiring the Data 

Biocides introduced into the soil have the potential to leach through the soil profile or transport to 

and dispersion in the aquatic environment. This movement of biocide residues may cause 

contamination of food, result in loss of usable land and water resources to man due to contamination of 

groundwater supplies, or cause habitat loss to wildlife. Therefore, laboratory studies are required to 

predict: (1) the leaching potential of biocides and degradates through the soil profile at terrestrial 

sites; and (2) the movement of biocides and degradates to and dispersion in aquatic sites. Results 

from the soil column leaching study will provide information on the soil mobility of biobor and its 

transformation products and their potential to reach aquatic environments. For outdoor wood 

preservative uses, biobor can reach surface water through direct contact or discharge to WWTPs. 

Biobor may also reach surface water or groundwater through run-off or leaching processes. The 

Agency will evaluate the potential risks of concern.

Practical Utility of the Data 

1. How will the data be used? 

Adsorption/desorption coefficients (Kd) for THPS would be obtained for the representative soils or 

aquatic sediments tested; however, partition coefficient estimates from soil-column leaching studies 

have substantially less precision than those estimated using batch equilibrium studies, which are 

considered to be a much more direct measure of the parameter. The Kd values, along with the 

solubility data, would establish the extent of depth of leaching for THPS and its transformation 

products through the soil profile of different soil types representative of typical use sites. Since 

aquatic/aquatic impact uses are proposed for THPS, the data would also establish the extent of 

depth of leaching for THPS and its transformation products in sediments. The Kd values are used 

in simulation modeling for registration review and new use registrations. 

2. How could the data affect the risk assessment? 

The results would indicate if THPS and its degradates leach through the soil/sediment profile, 

causing possible contamination of food, loss of usable land and water resources to man due to 

contamination of groundwater supplies, or loss of habitat to wildlife. The results could yield an 

improved confidence in the results of drinking water and ecological risk assessments. 

3. What is triggering the need for this data? 

Soil column leaching data is needed to conduct the fate assessment to support indoor and outdoor 

wood preservative uses for THPS.

24 
25 

Guideline Number: 835.1230 

Data Requirement: Sediment and soil adsorption/desorption

Rationale for Requiring the Data 

Biocides introduced into the soil have the potential to leach through the soil profile or transport to 

and dispersion in the aquatic environment. This movement of biocide residues may cause 

contamination of food, result in loss of usable land and water resources to man due to contamination 

of groundwater supplies, or cause habitat loss to wildlife. Therefore, laboratory studies are required 

to predict: (1) the leaching potential of biocides and degradates through the soil profile at terrestrial 

sites; and (2) the movement of biocides and degradates and dispersion in aquatic sites. Results from 

the adsorption/desorption study will provide information on the soil mobility of THPS and its 

transformation products and their potential to reach aquatic environments. For outdoor wood 

preservative uses, THPS can reach surface water through direct contact or discharge to WWTPs. 

THPS may also reach surface water or groundwater through run-off or leaching processes. The 

Agency will evaluate the potential risks of concern.

Practical Utility of the Data 

1. How will the data be used? 

The data would establish the significance of leaching as a route for THPS and/or its degradates to 

disperse and potentially reach aquatic environments. The study would help define the leaching 

behavior of THPS and/or its degradates by characterizing their adsorption/desorption coefficients 

(Kd) in representative soils and aquatic sediments. If the Freundlich equation is used, examples of 

calculations for 1/n and K values would also be provided. The adsorption/desorption coefficients 

calculated from a batch equilibrium study are used along with solubility data to predict the extent of 

depth of biocide leaching in the different soil types representative of typical use sites. Since 

aquatic/aquatic impact uses are proposed for THPS, the data would also establish the extent of 

depth of leaching for THPS and its degradates in sediments. The Kd values are used in simulation 

modeling for registration review and new use registrations. 

2. How could the data affect the risk assessment? 

The results would indicate if THPS and its degradates have the potential to leach through the 

soil/sediment profile, causing possible contamination of food, loss of usable land and water 

resources to man due to contamination of groundwater supplies, or loss of habitat to wildlife. The 

results could yield an improved confidence in the results of drinking water and ecological risk 

assessments. 

3. What is triggering the need for this data? 

Adsorption/ desorption data is needed to conduct the fate assessment to support indoor and outdoor 

uses for THPS.