2 of 22

Bronopol products are currently registered for use in aquatic and terrestrial oil and gas 

production areas to control bacteria and fungi in flood waters, fracturing fluids, oil process water, 

oil and gas pipelines, and tank maintenance. It is also used in industrial recirculating water 

cooling tower and evaporative condensers, paper mill process water, air scrubber units, and as a 

material preservative in such products as adhesives, metalworking cutting fluids, absorbent clays, 

starch, pigment, mineral slurries, paints and emulsions systems, paper (bulk pulp), water based

printing inks and fount solutions.

Science Findings

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

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

was the 1995 Bronopol RED. The findings are summarized below.

Product Chemistry Summary (99% TGAI)

Common Name: Bronopol

Chemical/CAS Name: 2-Bromo-2-nitro-1,3-propanediol

IUPAC Name: 2-Bromo-2-nitropropane-1,3-diol

Trade Names: Bioban; Rocima; Onyxide 500, others

CAS Registry Number: 52-51-7

OPP Chemical Code: 216400

Case: 2770

Molecular Formula: C3H6BrNO4

Molecular weight: 199.987 g/mol

Molecular Structure:

Color: White to pale yellow

Physical State: Crystalline solid

Odor: Odorless

Stability: Stable to normal temperature, but at 140°C exothermic 

decomposition occurs.

Oxidation/Reduction: Can be reduced electronically and has some weak oxidizing 

potential of no practical significance.

Flammability-Flash Point: Non-flammable

Explodability: Not explosive
3 of 22

Storage Stability: Storage stability tests on a batch of bronopol (initially 100% pure) 

showed no degradation after 52 weeks at 20 to 25°C and 45°C 

(both at normal relative humidity). At 90% RH and 20 to 25°C the 

bronopol content was 99.2%.

Miscibility: N/A

Corrosion Characteristics: Pure bronopol has very little potential to corrode but increasing the 

sodium bromide and water content increases the possibility of 

corrosion of materials such as mild steel, galvanized iron, cast iron 

and aluminum.

Dielectric Breakdown Voltage: N/A

pH: 4.5 to 7.0 (1% solution at 20°C)

UV/Visible Absorption: N/A

Viscosity: N/A, Bronopol is a crystalline solid.

Melting Point: About 130°C.

Boiling Point: N/A. At temperatures above 140°C Bronopol will decompose. 

Density: 9.18 lb/US Gallon (1.1 g/cm3)

Specific Gravity: 1.1

Dissociation Constant: Not applicable as bronopol degrades above pH 7.0. An 

experimental pKa of 9.56 is likely to be a composite pKa 

associated with bronopol and its decomposition products.

Log Kow: 0.18 at 20°C

Solubilities: Soluble in water (280 g/l) and organic solvents

Water: 28% @ 22-25°C (2.5 x 105 mg/L)

Ethanol: 58%

Propylene glycol: 52%

Vapor Pressure: 1.26 x 10-5 mm Hg at 20°C

1.68 x 10-3 Pa (20°C)

Henry's Law Constant: 1.3 x 10-11 atm-m3/mole at 25 °C

Enforcement

Analytical Method: HPLC

IR Spectroscopy
4 of 22

Gas chromatography

Thin-layer chromatography

All product chemistry data requirements have been satisfied for the active ingredient

bronopol. (Source: MRIDs 108808, 141875, 141876, 163783, & 45199101).

Environmental Fate Summary

The Agency has reviewed two environmental fate studies for bronopol and the 

environmental fate guideline study results are summarized in Table 1 and the degradates are 

listed in Table 2. The Agency's conclusions for the degradation studies are as follows.

Degradation Studies (Abiotic)

a. Hydrolysis

An adequate hydrolysis study exists. Hydrolysis is strongly correlated with temperature 

and pH. Hydrolysis may or may not occur appreciably, depending on conditions. An acceptable 

study, conducted under conditions different from the Agency's present testing guidelines, 

concluded that bronopol is stable against hydrolysis in "typical" natural settings. At elevated 

temperatures (30, 40, 50, and 60°C), in ambient laboratory light and at concentrations of 2000 

ppm or higher, the half-lives were extrapolated to be the following at 20°C: about 18 years at pH 

4, about 1.5 years at pH 6, and approximately 2 months at pH 8. At higher temperatures and/or 

pHs, as may occur in industrial applications, hydrolysis is greatly accelerated. At 60°C (140°F), 

half-lives ranged roughly from 4 days at pH 4 to only 3 hours at pH 8. This degradation is based 

on heat decomposition, not hydrolysis. Under accelerated conditions, degradation is extensive, 

and formaldehyde is a major hydrolysate. Other degradates produced under these circumstances 

are 2-hydroxymethyl-2-nitropropane-1,3-diol (Tris Nitro); 2-bromo-2-nitroethanol; unidentified 

products which were possibly polymers; bromide ion; nitrite (not nitrate); and other trace 

products such as aliphatic nitro compounds and lightweight gases, but not carbon dioxide (MRID

Nos. 00164535 and 00163783).

b. Photodegradation in water

A partially satisfactory photodegradation in water study indicates that bronopol rapidly 

photodegrades at pH 4 under continuous xenon irradiation at 25°C; approximately one-half of its 

activity remained after about 24 hours. An equivalent exposure time under natural sunlight 

would be approximately 2 days (assuming 12 hours each of light and dark). Tris (2-

hydroxymethyl-2-nitropropane-1,3-diol), also named tris-hydroxymethyl-nitromethane, was a 

tentatively identified major degradate (up to about 60 percent), which appears to further degrade, 

but at a slower rate. Another major, but unidentified, "relatively polar" product (component "B") 

steadily increased, and at the end of the 168 hour (one week) study was up to about 30 percent of 

the dose. Component "B" was not the putative degradate, 2-bromo-2-nitroethanol. Steadily 

increasing levels of labeled carbon dioxide derived from the central carbon atom of bronopol 

indicate that at least one reaction leads to extensive degradation. Although carbon dioxide 
5 of 22

increased in parallel with the unknown component "B," formation of component "B" and carbon 

dioxide appears to occur by separate pathways (MRID 429413-03).

Table 1. Environmental Fate Data Summary for Bronopol

OPP 

Guideline Fate Studies Half-Life Degradates Study Status

161-1 Hydrolysis

pH 4

pH 6

pH 8

18 years

1.5 years

2 months

Stable at pH 4, 6, & 8 at 20°C.

Minor Degradates:

Formaldehyde

Bomonitroethanol

Tris Nitro

Acceptable

MRID 

00164535

00163783

Acc # 265943

161-2 Aqueous 

Photolysis at pH 4 24.3 hours (equivalent to 2 

days under natural sunlight 

conditions) at 25°C.

Three Major photodegradates:

1. Tris-(hydroxymethyl)-

nitromethane.

2. Unidentified relatively polar 

major degradation product.

3. CO2

Supplemental

MRID

429413-03

Table 2. Degradates of Bronopol

Hydrolysates

 (Tris-Nitro)

Formaldehyde

Photoproducts:

(Tris-Nitro)

The Agency did not conduct an environmental fate assessment for bronopol because of 

lack of data. However, the Agency needs to conduct an environmental fate assessment for 

material preservatives (including bronopol) and industrial slimicides used in recirculating water 

cooling towers and paper mills that may potentially pass through waste water treatment plants 

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

the Agency anticipates needing those data outlined on page 11 of this document.
6 of 22

Water Quality

Bronopol 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)2

. 

In addition, no Total Maximum Daily Loads (TMDL) have been developed for Bronopol, based 

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

2011)3. 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.

Ecological Effects Summary

The registrant has submitted ecological effects studies for both terrestrial and aquatic 

animals. These data are adequate to provide the Agency with sufficient information to determine 

appropriate label precautions, and may be seen in Table 3.

a. Toxicity to Terrestrial Animals

(1) Birds, Acute and Subacute

Bronopol is slightly toxic to birds on an acute oral basis; and practically nontoxic 

to slightly toxic to birds on a subacute dietary basis.

(2) Mammals

Bronopol is moderately toxic to mammals on an acute oral basis.

There were no developmental effects that could be attributed to the administration 

of bronopol.

Systemic toxicity was observed mostly in the mid-dose (70 mg/kg/day) and highdose (200 mg/kg/day) groups, in both generations. Reproductive toxicity was 

observed only in the high-dose group as evidenced by a slight decrease in the 

female fertility index during the F1a mating (75% vs 87.5% in the controls).

 2 . http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885 3

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

group_name=PESTICIDES
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b. Toxicity to Aquatic Animals

(1) Freshwater Fish and Estuarine/Marine Fish

Bronopol is not more than slightly toxic to cold/warm water fish and marine fish.

Freshwater fish early-life stage toxicity study is classified as supplemental and 

may potentially underestimate the sensitivity of freshwater fish to bronopol. 

Further testing listed on page 10 of this document are required.

(2) Freshwater and Estuarine/Marine Invertebrates

Bronopol is moderately toxic to freshwater invertebrates and moderately to highly 

toxic to estuarine/marine invertebrates.

c. Toxicity to Aquatic Plants

Aquatic plant toxicity data are classified as supplemental and may potentially 

underestimate the sensitivity of aquatic plants to bronopol. Therefore, further 

plant toxicity testing listed on page 11 of this document are required.

Algal toxicity data indicate that bronopol is detrimental at less than 1.0 ppm to 

freshwater green algae and freshwater diatoms. Therefore, seedling emergence 

and vegetative vigor, Tier II-dose response studies listed on page 11 of this 

document are required.

Table 3. Ecotoxicity Data Summary for Bronopol

MRID COMMON

NAME TAXONOMIC GUIDELINE TYPE % AI STUDYTIME

DOSE

TYPE

TOXI

CITY

TOX

LEVEL NOEL STUDYSTATUS

TOX CATEGORY

Avian Acute Oral Toxicity

00104689 Mallard 

duck

Anas 

platyrhynchos

850.2100

(71-1)

O 99.4 14 day LD50 509 mgk 100 Acceptable Slightly toxic

Avian Subacute Dietary Toxicity

00148562 Bobwhite 

quail

Colinus 

virginianus

850.2200

(71-2a)

D 100 8 day LC50 4487 ppm 500 Acceptable Slightly toxic

00148941 Mallard 

duck

Anas 

platyrhynchos

850.2200

(71-2b)

D 100 8 day LC50 >10000 ppm N.R. Acceptable Practically non-toxic

Freshwater Fish Acute Toxicity

247196 Rainbow 

trout

Oncorhynchus 

mykiss

850.1075

(72-1)

S 99.4 96 hr LC50 20 ppm 10 Supplemental Slightly toxic

00148563 Rainbow 

trout

Oncorhynchus 

mykiss

850.1075

(72-1)

F 100 96 hr LC50 41.5 ppm 23 Acceptable Slightly toxic

00148940 Bluegill 

sunfish

Lepomis 

macrochirus

850.1075

(72-1)

F 99.7 96 hr LC50 36 ppm 20 Acceptable Slightly toxic

Estuarine/Marine Fish Acute Toxicity

00148939 Sheepshead 

minnow

Cyprinodon 

variegatus

850.1075

(72-3)

F 99.7 96 hr LC50 59 ppm 18 Acceptable Slightly toxic
8 of 22

MRID COMMON

NAME TAXONOMIC GUIDELINE TYPE % AI STUDYTIME

DOSE

TYPE

TOXI

CITY

TOX

LEVEL NOEL STUDYSTATUS

TOX CATEGORY

Freshwater Invertebrate Acute Toxicity

00098404 Water flea Daphnia 

magna

850.1010

(72-2)

S 99.4 48 hr EC50 1.6

1.4

ppm 0.56 Acceptable Moderately toxic

Freshwater Fish Early-Life Stage Toxicity - Embryo to juvenile (swim-up fry)

45838101 Rainbow 

trout

Oncorhynchus 

mykiss

850.1400

(OECD 210)

F 99.8% 49 day LC50

LOAEC

39

40 

nominal

7.48

mean 

measured

ppm

21

nominal

1.94 

mean 

measured

Supplemental

Estuarine/Marine Mysid Acute Toxicity - Invertebrates

00150674 Mysid 

Shrimp

Americamysis 

bahia

850.1035

(72-3)

F 99.7 96 hr LC50 5.9 ppm 2.4 Acceptable Moderately toxic

Estuarine/Marine Oyster Acute Toxicity (Shell Deposition) - Invertebrates

46965403 Eastern 

Oyster

Crassostrea 

virginica

850.1025 F 99.7 96 hr EC50 0.35 ppm 0.15 Supplemental Highly toxic

Estuarine/Marine Bivalve (Oyster) Acute Toxicity (embryo larval) – Invertebrates

00148979 Pacific 

oyster

Crassostrea 

gigas

850.1055

(72-3b)

S 99.7

Tech

48 hr EC50 0.78 ppm 0.16 Acceptable Highly toxic

Freshwater Aquatic Vascular Plant Toxicity

47178202 Duckweed Lemna gibba 850.4400 S 99.7 7 day EC50 38 ppm 5.4 Supplemental Toxic

Algal Toxicity

47178203 Marine 

diatom

Skeletonema 

costatum

850.5400 99.7 96 hr EC50 180 ppb 120 Supplemental Detrimental effects

47178204 Freshwater 

diatom

Navicula 

pelliculosa

850.5400 99.7 96 hr EC50 419 ppb 212 Supplemental Detrimental effects

47178205 Freshwater 

Green algae

Scenedesmus 

subspicatus

850.5400 99.7 96 hr EC50 20 ppb 12 Supplemental Detrimental effects

47178206 Freshwater

Bluegreen 

algae

Anabaena

flos-aquae

850.5400 99.7 96 hr EC50 34 ppb 12 Supplemental Detrimental effects

47256602 Freshwater

Green algae

Selenastrum 

capricornutum

850.5400 98.6 96 hr EC50 220 ppb 65 Supplemental Detrimental effects

Mammalian Acute Oral Toxicity

00098396 Rat 870.1100

(81-1)

99 LD50

LD50

307(M)

342(F)

mg/kgbwAcceptable Moderatetly toxic 

(II)

Mammalian Subchronic Oral Toxicity -Rats

00098384 Rat 870.3100 98.8 13 wks LOEL 80 mg/kgbw/day20 Acceptable Sever gastrointestinal irritant.

Mammalian Subchronic Oral Toxicity -Dogs

00098399 Beagle dogs 870.3100 99.2 13 wks LOEL 20 mg/kgbw/day8 Acceptable

Two-Generation Reproductive Toxicity in Rats

40660901

41916502

40660907

Charles 

River COBS 

CD strain 

Rat

870.3800

83-4

99.9 LOEL

for systemic 

toxicity

70 mg/kgbw/day25 Acceptable Systemic toxicity at 

70 mg/kg/day dose: 

increase in kidney 

weight; decreased 

liver weight; and 

increased incidence 

of nephropathy.
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MRID COMMON

NAME TAXONOMIC GUIDELINE TYPE % AI STUDYTIME

DOSE

TYPE

TOXI

CITY

TOX

LEVEL NOEL STUDYSTATUS

TOX CATEGORY

LOEL

for

reproductive 

toxicity

200 mg/kgbw/day70 Acceptable

Systemic toxicity at 

200 mg/kg/day dose:

decreased body 

weights; decreased 

food consumption; 

increases in organ 

weights (adrenals, 

kidneys and 

thyroid/parathyroid); 

decreases in liver 

weight; and an 

increased incidence 

of nephropathy.

Reproductive 

toxicity was 

observed only at 200 

mg/kg-bw/day dose: 

slight decrease in 

the female fertility 

index.

Oral Developmental Toxicity

43598701

43608501

SpragueDawley 

Rats

83-3 98

(99.5)

LOEL

Maternal

Developmental

mg/kgbw/day

>80

>80

Acceptable There were no 

developmental 

effects that could be 

attributed to the 

administration of 

bronopol.

42319601

42648201

New 

Zealand 

White 

Rabbits

83-3 LOEL

Maternal

Toxicity

Developmental

Toxicity

80

80

mg/kgbw/day

40

40

Acceptable The effects observed 

only in the 80 

mg/kg/day group 

include decreased 

fetal body weight in 

both sexes (10%), 

and an increase in 

fetuses with major 

external/visceral and 

skeletal 

abnormalities (6.9% 

- 29.5%).

In-vitro Bacterial Mutagenicity Testing (Ames Test)

40660902

92198025

Salmonella Salmonella 

typhimurium 

strains TA1535, 

TA1537, 

TA1538, TA98 

and

TA100, with 

and without 

metabolic 

activation.

870.5140

84-2(a)

99.7 Acceptable Negative for mutagenicity in the Ames 

test. The highest 

concentrations of 

bronopol tested were

125 ug and 62.5 

ug/plate, in the 

presence and absence 

of S-9, respectively. 

Concentrations of 

bronopol higher than 

these tested were too 

toxic for Salmonella

Test Type—O: oral; D: dietary; S: static; F: flow-through

Tox Level—mgk: milligrams per kilogram-body weight; ppm: parts per million (equivalent to milligrams per kilogram-diet (mg/kg-diet) for dietary 

exposure and milligrams per liter (mg/L) for aquatic exposures); ppb: parts per billion (equivalent to micrograms per liter (μg/L) for aquatic exposure)

Categories of acute toxicity for aquatic organisms (U.S. EPA, 2004) based on EC50/LC50(mg/L): < 0. 1 very highly toxic; 0.1-1 highly toxic; >1-10 

moderately toxic; >10-100 slightly toxic; >100 practically nontoxic. Toxicity categories for terrestrial plants have not been defined.

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.
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Adverse Ecological Incidents

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

(EIIS) regarding Bronopol. However, 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 on the bronopol’s use patterns 

described in this document. Bronopol uses that have potential for environmental exposure are 

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

paper mills discharges. The Agency anticipates conducting environmental fate and ecological 

risk assessments for material preservatives and industrial slimicides used in recirculating water 

cooling towers and paper mills 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 plant toxicity data outlined on page 11 of this document.

The Agency has not conducted a risk assessment for bronopol that supports a complete 

endangered species effects determination. The ecological risk assessment planned during 

registration review will allow the Agency to determine whether bronopol’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 U.S. Fish and Wildlife 

Service and/or National Marine Fisheries Services (the Services), as appropriate.
11 of 22

Environmental Fate and Ecotoxicity Data Gaps and Anticipated Work

Environmental fate and ecological risk assessments have not been conducted for 

bronopol. The Agency anticipates conducting environmental fate and ecological risk 

assessments for material preservatives, and industrial slimicides used in recirculating water 

cooling towers and paper mills 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 bronopol 

and/or any of its major degradation products that are of potential concern for all registered uses 

of bronopol. The following environmental fate and ecotoxicity data are needed to conduct an 

environmental fate and ecological risk assessment:

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

environmental fate assessment for material preservative use, industrial slimicides 

used in recirculating water cooling towers and paper mills:

o (GLN 850.6800) Modified Activated Sludge Respiration Inhibition;

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

(GLN 835.3280) Simulation Tests to Assess the Biodegradability of Chemicals 

Discharged to Wastewater4

.

• The Agency anticipates needing the following ecological effects data in order to 

conduct a complete ecological risk assessment, including an endangered species 

assessment for industrial slimicides used in recirculating water cooling towers and 

paper mills and material preservative uses of bronopol:

o (GLN 850.1300) Daphnid chronic toxicity test;

o (GLN 850.1400) Fish early-life stage toxicity test;

o (GLN 850.4225) seedling emergence, Tier II - dose response study on rice (Oryza 

sativa);

o (GLN 850.4250) vegetative vigor, Tier II - dose response study on rice (Oryza 

sativa);

o (GLN 850.4400) aquatic plant growth (aquatic vascular plant toxicity), Tier II -

dose response study on floating macrophyte Lemna gibba; and

o (GLN 850.5400) aquatic plant growth (algal toxicity), Tier II - dose response 

studies on Selenastrum capricornutum (green alga), Anabaena flos- aquae (bluegreen cyanobacteria), Navicula pelliculosa (freshwater diatom), and Skeletonema 

costatum (marine diatom).

 4 The results of the Activated Sludge Respiration Inhibition Test (ASRI) determine which of these biodegradation 

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

Sludge Study or 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) Biodegradation in Activated Sludge or the Porous Pot Test. If 

the antimicrobial passes the ready biodegradability study, then no further testing is required. If, however, the 

antimicrobial fails the ready biodegradability study, then the Biodegradation in Activated Sludge or the Porous Pot 

study is required.
12 of 22

Appendix A. Environmental Fate Guideline Study Justifications

Guideline Number: 850.6800; OECD 209

Study Title: Modified Activated Sludge, Respiration Inhibition Test for Sparingly Soluble 

Chemicals; Activated Sludge Respiration Inhibition Test

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 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 Biodegradation in Activated Sludge 

Study or 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) Biodegradation in Activated Sludge or the Porous Pot 

Test. If the antimicrobial passes the ready biodegradability study, then no further testing is required. If, 

however, the antimicrobial fails the ready biodegradability study, then the Biodegradation in Activated 

Sludge or 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. 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.
13 of 22

Guideline Numbers: 835.3110, 835.3220, or 835.3280

Study Titles: Ready Biodegradability, Porous Pot Test, or Simulation Tests to Assess the

Biodegradability of Chemicals Discharged to Wastewater (also referred to as Biodegradation in 

Activated Sludge), respectively

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 Biodegradation in Activated Sludge Study or 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) 

Biodegradation in Activated Sludge or the Porous Pot Test. If the antimicrobial passes the ready 

biodegradability study, then no further testing is required. If, however, the antimicrobial fails the ready 

biodegradability study, then the Biodegradation in Activated Sludge or 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 

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).
14 of 22

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.

Appendix B: Ecological Guideline Study Justifications

Guideline Number: 850.1300

Study Title: Daphnid chronic toxicity test

Practical Utility of the Data

1) What is the value of the study?

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.

2) How would 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 invertebrates from water 

column exposure to bronopol.

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) is 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.

4) What is triggering the need for this data?

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

in recirculating water cooling towers and paper mills and determine the chronic toxicity of bronopol to 

freshwater and marine invertebrates using life-cycle studies. Also data are needed in order to conduct 

an ecological risk assessment for material preservative use pattern of bronopol.
15 of 22

Guideline Number: 850.1400

Study Title: Fish early-life stage toxicity test

Practical Utility of the Data

1) What is the value of the study?

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 LOAEC and the NOAEC.

2) How would 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 NOAEC for estuarine/marine 

fish 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.

4) What is triggering the need for this data?

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

in recirculating water cooling towers and paper mills and determine the effects of bronopol on fish 

development and survival during early life stages. Also data are needed in order to conduct an 

ecological risk assessment for material preservative use pattern of bronopol.
16 of 22

Guideline Number: 850.4225

Study Title: Seedling emergence, Tier II - dose response using rice (Oryza sativa)

Practical Utility of the Data

1) What is the value of the study?

Plants prevent erosion and provide animals with food and shelter. The rooted aquatic plant, rice is 

used to represent exposure to all vascular rooted plants. Tier II (Definitive Studies) tests are initiated 

following a determination that a greater than 25% adverse effect occurred in the Tier I (Initial 

Screening Study) seedling emergence study for one or more plant species. These Tier II terrestrial 

nontarget plant phytotoxicity tests evaluate the acute toxicity of pesticides to 10 crop plant species, 

including six Dicots and four Monocots. Although rice (Oryza sativa) is not one of the surrogate 

terrestrial crop plants typically tested, its semiaquatic environment is applicable to run-off scenarios. If 

conducting tests under TSCA, the test material is applied daily with each watering for the duration of 

the study. Observations are carried out for at least 14 days after seedling emergence.

2) How would the data be used?

Along with vegetative vigor studies, results of these studies will be used to assess risks to of bronopol 

exposure to terrestrial, semiaquatic, and aquatic nontarget plants. Parameters of plant growth include 

percent emergence, number of emerged plants, seedling height, seedling dry weight, root length, root 

dry weight, and signs of phytotoxicity. Results are reported as EC05 (NOAEC), EC25, and EC50.

3) How could the data affect the risk assessment?

Because bronopol would not be directly applied to the field, information on environmental fate and 

transport would affect the risk identification and characterization to non-target plants. Nontarget plants 

include plants outside the area of intended application (which would typically include food and cover 

vegetation for animals, food, fiber, fuel, and ornamental plants for humans, and endangered and 

threatened plants). Terrestrial plants serve as food and shelter for fish and wildlife, help control 

erosion, and serve as air pollution filters. Shoreline vegetation buffers reduce siltation and provide an 

environment in which aquatic invertebrates can contribute to the food supply of fish, reptiles, and 

amphibians. Vegetation adjacent to streams serves to regulate water temperature, which in turn 

contributes to improved aquatic life. Decaying vegetation provides nutrients essential for the aquatic 

food chain. Hedgerows, woodlots, and other similar nontarget areas provide food and cover to 

mammalian and avian species.

There are many terrestrial plants that may be affected where bronopol is used as a slimicide in 

recirculating water cooling towers and paper mills. If EPA is unable to evaluate the potential risks to 

terrestrial plants associated with the new use of bronopol, these risks must be presumed. As part of the 

risk assessment for terrestrial plants (non-endangered and endangered), the lowest EC25 for monocots 

and dicots is used in the RQ equation. The LOC for endangered and non-endangered plants is defined 

as a RQ > 1.

4) What is triggering the need for this data?

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

in recirculating water cooling towers and paper mills and determine the effects of bronopol on seedling 

emergence.
17 of 22

Guideline Number: 850.4250

Study Title: Vegetative vigor, Tier II - dose response using rice (Oryza sativa)

Practical Utility of the Data

1) What is the value of the study?

Plants prevent erosion and provide animals with food and shelter. The rooted aquatic plant, rice is 

used to represent exposure to all vascular rooted plants. Tier II (Definitive Studies) tests are initiated 

following a determination that a greater than 25% adverse effect occurred in the Tier I (Initial 

Screening Study) vegetative vigor study for one or more plant species. These Tier II terrestrial 

nontarget plant phytotoxicity tests evaluate the acute toxicity of pesticides to 10 crop plant species, 

including six Dicots and four Monocots. Although rice (Oryza sativa) is not one of the surrogate 

terrestrial crop plants typically tested, its semiaquatic environment is applicable to both leaching and 

run-off scenarios. The test material is applied 2 to 4 weeks after the plants have emerged from the soil, 

and observations are carried out for at least 14 days.

2) How would the data be used?

Along with the seedling emergence studies, results of these studies will be used to assess risks to 

terrestrial and aquatic plants from exposure to bronopol. Parameters of plant growth include plant 

height, plant dry weight, root length, root dry weight, and signs of phytotoxicity. Results are reported 

as EC05 (NOAEC), EC25, and EC50.

3) How could the data affect the risk assessment?

Because bronopol would not be directly applied to the field, information on environmental fate and 

transport would affect the risk identification and characterization to non-target plants. There are many 

terrestrial plants that are listed as threatened and endangered in the United States where bronopol is 

used as a slimicide in recirculating water cooling towers and paper mills. If EPA is unable to evaluate 

the potential risks associated with the recirculating cooling water systems and paper mills uses of 

bronopol, these risks must be presumed. As part of the risk assessment for terrestrial plants (nonendangered and endangered), the lowest EC25 for monocots and dicots is used in the RQ equation. The 

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

4) What is triggering the need for this data?

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

in recirculating water cooling towers and paper mills and determine the effects of bronopol on 

vegetative vigor.
18 of 22

Guideline Number: 850.4400

Study Title: Aquatic Plant Toxicity Test Using Lemna spp., Tiers II

Practical Utility of the Data

1) What is the value of the study?

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 bronopol in fresh water to measure phytotoxicity.

2) How would the data be used?

This study would be used to evaluate the toxicity of bronopol 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 where bronopol is used as a material preservative and industrial 

slimicides used in recirculating water cooling towers and paper mills. If EPA is unable to evaluate the 

potential risks to aquatic plants associated with the material preservative and industrial slimicides used 

in recirculating water cooling towers and paper mills use of bronopol, 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.

4) What is triggering the need for this data?

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

preservatives and industrial slimicides used in recirculating water cooling towers and paper mills and 

determine the effects of bronopol on aquatic plants because they are critical to ecosystem health and 

productivity. Aquatic plants may be exposed via indoor uses from bronopol used in material 

preservatives and industrial slimicides used in recirculating water cooling towers and paper mills that 

pass through WWTPs.
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Guideline Number: 850.5400

Study Title: Algal Toxicity, Tier II (Selenastrum capricornutum, Anabaena flos-aquae, 

Navicula pelliculosa and Selenastrum Capricornutum)

Practical Utility of the Data

1) What is the value of the study?

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

oxygen to animal species. Green algae, blue-green cyanobacterium, and diatoms (marine and 

freshwater), represents thousands of algae species. As part of a Tier I risk assessment for microphytic 

toxicity, freshwater green algae (Selenastrum capricornutum), marine diatom (Skeletonema costatum), 

the freshwater diatom (Navicula pelliculosa), and the blue-green alga or cyanobacterium (Anabaena 

flos-aquae) are tested for phytotoxicity.

2) How would the data be used?

This study would be used to evaluate the toxicity of bronopol to algae in aquatic ecosystems. The 

algal growth response (number or weight of algal cells/mL) is measured at the end of the 96 h test. 

The percentage inhibition or stimulation of growth for each concentration, concentration response 

curves, and EC50s are determined from these data. Tier II (definitive) testing may not be necessary if 

the highest chemical concentration tested (water saturation concentration or 1000 mg/L) results in less 

than 50% reduction in growth. However, if the lowest concentration tested (analytical detection limit) 

results in greater than a 50% reduction in growth, definitive testing is required.

3) How could the data affect the risk assessment?

Because algae are critical to ecosystem health and productivity, any adverse effects to algae 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. As part of the risk 

assessment for algae, the lowest EC50 is used in the RQ equation. The LOC for plants is defined as a 

RQ > 1.

4) What is triggering the need for this data?

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

in recirculating industrial cooling tower water systems and paper mills and determine the effects of 

bronopol on algae because they are critical to ecosystem health and productivity. In addition to the 

environmental outdoor exposure to effluent discharges of bronopol from recirculating cooling water 

systems, algae species may be exposed via indoor uses from bronopol used in pulp and paper mill 

water systems that pass through WWTP. Also data are needed in order to conduct an ecological risk 

assessment for material preservative use pattern of bronopol.
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Appendix C

Registered Products of Bronopol

Registration # Registration Name Company Name Formulation 

Type

% of Active 

Ingredient

464-675 BiobanTM BP-Plus 

Preservative The Dow Chemical Co. Ready-to-Use Solution 99

464-676 Bioban BP-40 

Preservative The Dow Chemical Co. Ready-to-Use Solution 40.8

464-680 Bioban BP-10 

Preservative The Dow Chemical Co. Ready-to-Use Solution 10

464-685 Bioban BP 30 

Preservative The Dow Chemical Co. Ready-to-Use Solution 30

464-687 Bioban BP-M 

Preservative The Dow Chemical Co. Technical Chemical 99

707-295 ROCIMATM 607 Rohm & Haas Co. Ready-to-Use 

Solution 10

707-315 ROCIMATM 586 Rohm & Haas Co. Soluble 

Concentrate 7.5

1258-1290 Proxel BN Preservative Arch Chemicals, Inc. Soluble 

Concentrate 6.5

1529-58 Nuosept W International Specialty 

Products 

Flowable 

Concentrate 7

1529-59 Nuosept W Concentrate International Specialty 

Products 

Soluble 

Concentrate 14

3876-147 S3876 DE-1220 GE Betz, Inc. Ready-to-Use 

Solution 5.3

3876-151 Betz® DE-5556 GE Betz, Inc. Ready-to-Use 

Solution 5.3

5383-106 Mergal K12N Troy Chemical Corp Ready-to-Use 

Solution 7.1

9386-45 AMA®-4900B Kemira Chemicals, Inc, Ready-to-Use 

Solution 10

10707-53 X-CIDE® 600 Industrial 

Microbiocide Baker Petrolite Corporation Water Soluble Packaging 98.45

33753-3 Myacide AS BASF Corporation Technical 

Chemical 99

33753-5 Myacide AS Plus BASF Corporation Crystalline 99

33753-7 Myacide S2 BASF Corporation Ready-to-Use 40.8
21 of 22

Registration # Registration Name Company Name Formulation 

Type

% of Active 

Ingredient

Solution

33753-17 Myacide S15 BASF Corporation Ready-to-Use 

Solution 10

33753-18 2K7 Bugstick BASF Corporation Pelleted/Tableted 84.5

33753-20 Myacide S30 BASF Corporation Ready-to-Use 

Solution 30

39967-28 Biochek 721M LANXESS Corporation Ready-to-Use 

Solution 6

39967-59 Preventol P 100 LANXESS Corporation Technical 

Chemical 99.74

39967-61 Preventol P 100 

Preservative LANXESS Corporation Soluble Concentrate 99.74

39967-64 Preventol P 30 LANXESS Corporation Soluble 

Concentrate 30

39967-79 Preventol P 91 LANXESS Corporation Emulsifiable 

Concentrate 9.97

49403-33 Nipacide GSF-A Clariant Corporation Ready-to-Use 

Solution 5.35

67071-16 Acticide LA Thor GmbH Ready-to-Use 

Solution 8.8

67071-18 Acticide SR 2060 Thor GmbH Ready-to-Use 

Solution 5.2

67071-45 Acticide MBL 5515 Thor GmbH Soluble 

Concentrate 15

67071-46 Acticide MBL Thor GmbH Ready-to-Use 

Solution 8

67071-50 Acticide LA 2605-F Thor GmbH Soluble 

Concentrate 5.3

67071-52 Acticide MBL 5505 Thor GmbH Soluble 

Concentrate 5

67212-1 BBJ Microbiocide BBJ Environmental, LLC Ready-to-Use 

Solution 95

67212-2 BBJ Maintain C-1 For 

Floors And Walls BBJ Environmental, LLC Soluble Concentrate 3.25

67212-3 BBJ Mold Control BBJ Environmental, LLC Ready-to-Use 

Solution .05

67420-1 2K7 Bugstick OSP Microcheck Inc Water Soluble 84.5
22 of 22

Registration # Registration Name Company Name Formulation 

Type

% of Active 

Ingredient

Packaging

67420-2 2K7 Water Soluble Paks OSP Microcheck Inc Crystalline 99

67869-37 Vericide Bronopol Verichem, Inc. Crystalline 99

67869-38 Vericide Bronopol 

Solution Verichem, Inc. Soluble Concentrate 10

68708-9 EC9086A Nalco Company Ready-to-Use 

Solution 8.8

74655-14 Spectrum RX-96 Hercules Incorporated Ready-to-Use 

Solution 5.3