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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Code: 073301

DP Barcode: 429645

MEMORANDUM March 10, 2016

Subject: Inorganic Chlorates (Sodium Chlorate) Problem Formulation for Registration 

Review

To: Brittany Pruitt, Chemical Review Manager 

Tracy Perry, Team Leader

Kelly Sherman, Branch Chief

Risk Management and Implementation Branch 3

Pesticide Re-Evaluation Division (7508P)

Sandra O’Neill, Chemical Review Manager

Rose Kyprianou, Team Leader

Lance Wormell, Branch Chief

Regulatory Management Branch 2

Antimicrobials Division (7510P)

From: Stephen Carey, Biologist

Andrew Shelby, Physical Scientist

Environmental Risk Branch 6

Environmental Fate and Effects Division (7507P)

Diana Hsieh, Biologist

David Bays, Biologist

Siroos Mostaghimi, PhD, Senior Scientist 

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

Through: Mark Corbin, Branch Chief

Monica Wait, RAPL

Environmental Risk Branch 6

Environmental Fate and Effects Division (7507P)

Laura Parsons, Associate Branch Chief

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)
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The Environmental Fate and Effects Division (EFED) and the Antimicrobials Division (AD) 

have completed the problem formulation (PF) for the environmental fate and ecological risk

assessments to be conducted as part of the registration review of the inorganic salt sodium 

chlorate (PC Code 073301). The inorganic chlorates registration review case consists of multiple 

pesticidal active ingredients, including sodium chlorate, calcium chlorate, potassium chlorate, 

and magnesium chlorate. However, sodium chlorate is the only chemical that has active 

pesticidal product registrations, and thus it will be the focus of this registration review problem 

formulation. Sodium chlorate is registered for both conventional (herbicide and plant desiccant) 

uses and antimicrobial uses.

Sodium chlorate is registered for use on a wide variety of agricultural and non-agricultural uses 

nationwide. The agricultural uses include beans, corn, cotton, flax, guar, peas, peppers, potato, 

rice, safflower, sorghum, soybeans, sunflower, and wheat. According to the Screening Level 

Usage analysis (BEAD, 7/1/15), cotton, rice, and potatoes make up the bulk of the agricultural 

usage with an annual average of 700,000 lbs, 500,000 lbs, and 10,000 lbs of a.i. applied 

respectively. The non-agricultural uses of sodium chlorate include fallow land, ornamentals, and 

uncultivated land. 

Sodium chlorate is also registered for antimicrobial uses including: pulp/paper mill water 

systems, recirculating and once-through cooling water towers, drinking water treatment, textile 

mill water systems, sewage and wastewater systems, gas and oil fracturing fluid systems, 

disinfectants and sanitizers, ballast water treatments, and impounded lakes.

As the first stage of the risk assessment process for Registration Review, this problem 

formulation provides an overview of what is currently known about the environmental fate and 

ecological effects associated with sodium chlorate. It also describes the preliminary ecological 

risk hypothesis and analysis plan for evaluating and characterizing risk to non-target species and 

the environment in support of Registration Review.

Data Gaps

The ecological effects and environmental fate database is largely complete for sodium chlorate 

except for the following required studies under 40 CFR Part 158:

Environmental Fate

Conventional Uses:

• Terrestrial Field Dissipation (Guideline 835.6100) has never been waived. There is 

uncertainty on how long sodium chlorate (formulated) may remain active in the field. Of 

particular concern is persistence in use sites in semi-arid areas. Additional information and/or 

actual field studies are needed. The open literature information previously submitted by the 

registrant is not sufficient to decrease the uncertainty on field persistence of sodium chlorate 

products.
Page 3 of 33

• Environmental chemistry method (ECM) in water and a corresponding Independent 

Laboratory Validation (ILV) (Guideline 850.6100)

• Environmental chemistry method (ECM) in soil and a corresponding Independent Laboratory 

Validation (ILV) (Guideline 850.6100)

Antimicrobial Uses:

Sodium chlorate is used as a chlorine dioxide generator for its antimicrobial uses. No additional 

environmental fate data are necessary for the antimicrobial uses of sodium chlorate. 

Ecological Effects

Conventional Uses:

• Agricultural and non-agricultural outdoor applications of sodium chlorate may cause 

exposure to pollinators visiting off-site plants that are contaminated by spray drift. A 

complete set of honey bee toxicity data for adults and larvae have not been submitted for 

sodium chlorate, and these data are needed to fulfill the Agency’s recent policy on pollinator 

protection. A Tier I study on the toxicity of residues on foliage (OCSPP 850.3030) is not 

needed since results of the honey bee acute contact LD50 is >25 μg a.i./bee, above the 11 μg 

a.i./bee trigger criterion. To be consistent with the honey bee risk assessment framework, the 

following six Tier I, II and III honey bee studies, yet to be submitted for sodium chlorate, are 

required: 

o Honey bee larval acute oral toxicity study (following OECD 237, Tier I)

o Honey bee larval chronic oral toxicity study, special study, Tier I)

o Honey bee adult chronic oral (special study; Tier I)

o Semi-field testing for pollinators (special study, Tier II). 

o Field testing for pollinators (OCSPP 850.3040, Tier III)

o Field trial of residues in pollen and nectar (special study, Tier III)

For pollinator studies without finalized OECD guidelines, protocols should be submitted for 

EPA review and comment prior to study initiation. The need for higher Tier semi-field and 

full field pollinator studies for sodium chlorate will be determined after review of the Tier I 

studies.

• Acceptable avian acute oral toxicity data were not submitted for a passerine species exposed 

to sodium chlorate, which is now required under the 40 CFR Part 158 data requirements 

(Guideline 850.2100). Though the available bobwhite quail and mallard duck studies indicate 

sodium chlorate has low toxicity to bird species, it is uncertain whether passerines may be 

more or less sensitive to this chemical as a result of their higher metabolic rate and differing 

metabolic pathways. An avian oral toxicity study is needed for a passerine species. 

• A complete set of toxicity data for aquatic plants is not available. Guidelines 850.4400, 

850.4500, and 850.4550 require one aquatic vascular plant species and four aquatic 
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nonvascular plant species. Only the Lemna minor (an aquatic vascular plant) and 

Selenastrum capricornutum (one of the four aquatic nonvascular plants) plant species were 

submitted to satisfy the 850 guidelines for toxicity testing with aquatic plants. A marine 

diatom, a cyanobacteria, and a freshwater diatom have not been submitted, which are 

generally required for herbicide and some antimicrobial uses. Additional data under 

Guidelines 850.4500 and 850.4550 will be needed to address the uncertainty in the aquatic 

risk assessment for herbicides. However, these studies will not be required for the 

antimicrobial uses of this chemical, because the antimicrobial sodium chlorate products are 

all chlorine dioxide generators. Therefore, chlorine dioxide is the compound to which 

aquatic plants would potentially be exposed from the antimicrobial uses. The Agency has 

these studies on chlorine dioxide, which can be used in a risk assessment. 

Conventional and Antimicrobial Uses:

• Currently, acceptable chronic studies for aquatic organisms, except the daphnid, are not 

available. EFED and AD currently have data gaps for the Fish Early Life-Stage studies with 

freshwater and estuarine/marine fish species (Guideline 850.1400) and for a Life Cycle study 

with estuarine/marine invertebrates (Guideline 850.1350) to obtain a chronic toxicity value in 

order to assess the risks of sodium chlorate to these aquatic organisms. 

While the current uses trigger the 40 CFR Part 158 criteria for requiring these chronic aquatic 

studies, the studies are not needed at this time based on the low chronic toxicity observed in 

the available information and the anticipated environmental exposure. A comparison of the 

highest estimated environmental exposure (EEC) of 0.9 mg/L for agricultural uses (obtained 

from the RED) and the daphnid No Observed Adverse Effect Concentration (NOAEC) of 

500 mg/L (MRID 46731301) indicates a chronic toxicity value would have to be 555 times 

more sensitive than the daphnid NOAEC (the only data available to assess the potential risk 

to aquatic organisms from chronic exposure) in order to result in an level of concern (LOC)

exceedance, which is unlikely. Also, the NOAEC of 500 mg/L in the daphnid chronic study 

was at the highest treatment level tested with no effects observed., . In the absence of data, 

conservative assumptions may be used in the registration review risk assessment, if needed. 
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Problem Formulation of the Environmental Fate and 

Ecological Risk in Support of the Registration Review 

of Inorganic Chlorates (Sodium Chlorate)

Sodium Chlorate

CAS Registry No.: 7775-09-9

PC Code: 073301

Prepared by:

Environmental Fate and Effects Division:

Environmental Risk Branch VI

Stephen Carey, Biologist

Andrew Shelby, Physical Scientist

U. S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch VI

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Antimicrobials Division:

Risk Assessment and Science Support 

Branch

Diana Hsieh, Biologist

David Bays, Ph.D. Biologist

Siroos Mostaghimi, Ph.D., Senior Scientist

Reviewed by:

Laura Parsons, Associate Branch Chief

Reviewed by:

Monica Wait, RAPL

Mark Corbin, ERB6 Branch Chief

March 10, 2016

Office of Chemical Safety 

and Pollution Prevention
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Contents

1. Introduction.............................................................................................................................. 7

2. Use Characterization................................................................................................................ 7

3. Conclusions from Previous Assessments............................................................................... 10

3.1. Previous Ecological Risk Assessments.......................................................................... 10

3.2 Previous Drinking Water Exposure Assessment ............................................................ 10

3.3. Clean Water Act and Safe Drinking Water Act Programs ............................................. 11

4. Environmental Fate and Transport......................................................................................... 11

4.1. Transformation Products................................................................................................. 13

5. Receptors................................................................................................................................ 13

5.1. Effects to Aquatic Organisms......................................................................................... 13

5.2. Effects to Terrestrial Organisms..................................................................................... 14

5.3. Ecological Incidents........................................................................................................ 15

6. Exposure Pathways of Concern ............................................................................................. 16

7. Analysis Plan ........................................................................................................................... 16

7.1. Stressors of Concern ....................................................................................................... 16

7.2. Measures of Exposure.................................................................................................... 16

7.3. Measures of Effect .......................................................................................................... 17

7.4. Endangered Species Assessments................................................................................... 17

7.5. Endocrine Disruptor Screening Program........................................................................ 18

8. Environmental Fate and Ecological Effects Data ................................................................. 18

8.1. Environmental Fate............................................................................................................ 18

8.2. Effects................................................................................................................................ 20

9. References................................................................................................................................ 24

Appendix 1. STIR..................................................................................................................... 32

Appendix 2. SIP........................................................................................................................ 33
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1. Introduction

EFED and AD evaluated the most recent ecological risk assessments for sodium chlorate in 

association with the updated toxicity, exposure, and usage information to determine if sufficient 

data are available and if further updates are needed to support registration review. EFED and AD 

will use application scenarios that result in upper bound exposure scenarios for the registered 

uses of sodium chlorate for the risk assessment. 

Sodium chlorate is a strong oxidizer and may be reduced to a variety of chemical species 

depending on the environmental conditions. As a consequence of its reaction as an oxidant, 

sodium chlorate generates reduced chloro species (i.e., chlorine in lower oxidation states than 

chlorate), such as chlorite and hypochlorite.

In addition to its registered use as a pesticide active ingredient, sodium chlorate is approved as an 

inert ingredient in pesticide formulations, is listed as an impurity in some pesticide formulations,

and has non-pesticidal uses as a bleaching agent particularly in paper production. The 

registration review ecological assessment will not address the inert and non-pesticidal uses of 

sodium chlorate, but they will be included in the water monitoring data obtained from the EPA 

Office of Water.

Some trade names for conventional products containing sodium chlorate include Purate®, Drexel 

Defol®, Weed and Grass Killer®, Ureabor®, Monobor-Chlorate®, Cotton Defoliant Concentrate®, 

EKA SC BC 47, Ercocide®, Pramitol®, Drew®, and Puremax®. End-use products are formulated 

as flowable concentrates, granulars, impregnated materials, pelleted/tableted, ready-to-use 

solutions, and soluble concentrates. 

Some trade names for antimicrobial products containing sodium chlorate include Purate®, EKA,

Ercocide, and PureMax. End-use products are formulated as aqueous solutions and soluble 

concentrates.

2. Use Characterization

Sodium chlorate is currently registered for use on a wide range of agricultural crops, fallow or 

uncultivated land, and industrial uses. Crop and land uses range from pre-emergence to preharvest in the timing of application. Table 1 details the registered uses of sodium chlorate.

Table 1. Sodium Chlorate Application Rates for the Various Agricultural and Nonagricultural Conventional and Antimicrobial Uses.

Crop Maximum 

Single 

Application 

Rate 

(lb a.i./A)

Number of 

Applications

Maximum 

Application 

Rate 

(Annual or 

crop cycle)

Reapplicati

on 

Interval

Method of 

Application

AGRICULTURAL DRAINAGE 

SYSTEMS NDC NS NS NS

Water 

treatment.

AGRICULTURAL 6 NS NS NS Spray.
Page 8 of 33

Table 1. Sodium Chlorate Application Rates for the Various Agricultural and Nonagricultural Conventional and Antimicrobial Uses.

Crop Maximum 

Single 

Application 

Rate 

(lb a.i./A)

Number of 

Applications

Maximum 

Application 

Rate 

(Annual or 

crop cycle)

Reapplicati

on 

Interval

Method of 

Application

FALLOW/IDLELAND / 

CONSERVATION RESERVE

AGRICULTURAL 

FALLOW/IDLELAND / 

CONSERVATION RESERVE 6 NS NS NS Spray.

BEANS, DRIED-TYPE 6 NS NS NS Spray.

COMMERCIAL/INDUSTRIAL 

WATER COOLING SYSTEMS NDC NS NS NS Water treatment 

CORN (ALL OR 

UNSPECIFIED) 6 NS NS NS Spray.

COTTON (UNSPECIFIED) 6 2 NS NS

Foliar 

treatment.

FLAX 6 NS NS NS Spray.

DRINKING WATER 

TREATMENT NDC NS NS NS Water treatment

GUAR 6 NS NS NS Spray.

INDUSTRIAL PROCESSING 

WATER NDC NS NS NS

Water 

treatment.

LAKES/PONDS/RESERVOIRS 

(WITHOUT HUMAN OR 

WILDLIFE USE) NDC NS NS NS

Water 

treatment.

NONAGRICULTURAL 

UNCULTIVATED 

AREAS/SOILS 0.9* NS NS NS

Prepaving 

treatment.

NONAGRICULTURAL 

UNCULTIVATED 

AREAS/SOILS 143.3 1 NS NS Broadcast

ORNAMENTALS 

(UNSPECIFIED) 6 NS NS NS Spray.

PASTEURIZER/WARMER/CA

NNERY COOLING WATER 

SYSTEMS NDC NS NS NS

Water 

treatment.

PEAS, SOUTHERN 6 NS NS NS Spray.

PEPPER (CHILI TYPE) 7.5 NS NS NS Spray.

POTATO, WHITE/IRISH (OR 

UNSPECIFIED) 6 NS NS NS Spray.

PULP/PAPER MILL WATER 

SYSTEMS NDC NS NS NS

Preservative 

treatment.

PULP/PAPER MILL WATER 

SYSTEMS NDC NS NS NS

Water 

treatment.

RICE 6 NS NS NS Spray.

SAFFLOWER (UNSPECIFIED) 6 NS NS NS Spray.

SECONDARY OIL 

RECOVERY INJECTION 

WATER NDC NS NS NS

Water 

treatment.

SEWAGE SYSTEMS NDC NS NS NS

Water 

treatment.
Page 9 of 33

Table 1. Sodium Chlorate Application Rates for the Various Agricultural and Nonagricultural Conventional and Antimicrobial Uses.

Crop Maximum 

Single 

Application 

Rate 

(lb a.i./A)

Number of 

Applications

Maximum 

Application 

Rate 

(Annual or 

crop cycle)

Reapplicati

on 

Interval

Method of 

Application

SORGHUM 6 NS NS NS Spray.

SOYBEANS (UNSPECIFIED) 6 NS NS NS Spray.

SUNFLOWER 6 NS NS NS Spray.

WHEAT 6 NS NS NS Spray.

NDC – No dosage conversion

NS – Not specified

BEAD’s screening level usage analysis (SLUA, 7/1/2015) characterizes agricultural usage of 

sodium chlorate from 2004 through 2013. The SLUA does not include usage of sodium chlorate 

as an antimicrobial pesticide or for industrial or non-agricultural uses. The largest use patterns in 

agriculture are cotton and rice. Average annual agricultural usage from 2004 through 2013 was 

more than one million pounds per year. See Table 2 for details on usage below.

Table 2. Screening Level Estimates of Agricultural Uses of Sodium Chlorate

Annual Average Percent Crop Treated

Crop Lbs. A.I. Average Maximum

Corn 1,000 <2.5 <2.5

Cotton 700,000 <2.5 10

Peppers 1,000 <1 <2.5

Potatoes 10,000 <1 <2.5

Pumpkins+ <500 <1 <2.5

Rice 500,000 5 5

Sorghum 2,000 <2.5 5

Squash+ <500 <2.5 <2.5

Watermelons+ <500 <1 <2.5

All numbers are rounded.

<500: less than 500 pounds of active ingredients.

 <2.5: less than 2.5 percent of crop is treated.

<1: less than 1 percent of crop is treated.

+ : Removal of the cuburbit sites from the labels occurred before and during the timeframe of the 

SLUA. 

SLUA data sources include: 

USDA-NASS (United States Department of Agriculture's National Agricultural Statistics 

Service) 

Private Pesticide Market Research

California DPR (Department of Pesticide Regulation)

These results reflect amalgamated data developed by the Agency and are releasable to the public.
Page 10 of 33

3. Conclusions from Previous Assessments

3.1. Previous Ecological Risk Assessments

The Agency has previously conducted ecological risk assessments for inorganic chlorates that 

serve as a basis for this problem formulation. These assessments are briefly summarized below. 

The sodium chlorate reregistration ecological risk assessment was conducted in 2006 (DP 

303884, 6/1/2006). The major ecological conclusions presented in previous risk assessments for 

inorganic chlorate uses were as follows:

Summary of Risk Concerns Identified for Sodium Chlorates in the Previous Assessment (RED)

Taxa with 

Acute LOC 

Exceedances

Taxa with 

Chronic LOC 

Exceedances

Taxa with 

No LOC 

Exceedances

BCF Persistence Degradates of 

Concern

Terrestrial 

plants, Birds1, 

Mammals2

, 

Aquatic 

vascular plants

Birds, Mammals Aquatic

organisms 

and Aquatic 

nonvascular 

plants3

No No Not an ecological 

concern

1 Acute risk to birds cannot be precluded for non-ag uses. No mortality occurred in the studies at the highest concentration 

tested; however, EECs on several food items for some of the non-ag uses are significantly higher than 5620 mg/kg-diet. 2 Acute risk to mammals cannot be precluded for non-ag uses even though chlorate is of low toxicity to mammals (10% 

mortality occurred at 5000 mg/kg-bw). Some of the non-ag uses could result in ingestion of chlorate at levels that are 

significantly higher than 5000 mg/kg-bw for some food items. 3 LOCs for algae (aquatic nonvascular plants) were not exceeded; however, aquatic nonvascular plant toxicity data in 

several required species have not been submitted. Thus, potential risk to aquatic nonvascular plants may have been 

underestimated. Also, open literature data suggest that brown algae may be considerably more sensitive than green algae.

3.2 Previous Drinking Water Exposure Assessment

The most recent drinking water assessment (DWA) for sodium chlorate was for the 

Reregistration Eligibility Decision (RED) (D303556, January 5, 2005). An addendum to this 

DWA was issued on February 23, 2005 (D303568).

The modeled drinking water assessment conducted for the RED utilized FIRST for Estimated 

Drinking Water Concentrations (EDWCs) from surface water and SCI-GROW for EDWCs from 

groundwater. However, the predicted chlorate concentrations were believed to be theoretical 

maximums because the chemical speciation of chlorate could not be considered in modeling. The 

highest EDWC for chlorate was 784 ppb for the 12.5 lbs a.i./A use on potatoes and chili peppers. 

There are no longer registered uses on potatoes and chili peppers with application rates as high as 

the previously assessed rates. However, broadcast use on non-agricultural uncultivated areas has a 

maximum application rate of 143.3 lbs a.i./A and was not considered in the estimation of RED 

EDWCs. The DWA addendum explains the conservatism of EDWCs presented in the original 

assessment as each estimate of chlorate, chlorite, and hypochlorite assumes all sodium chlorate 

reduces to the given single reduced species. Due to the conservative nature of the modeled 

EDWCs, the revised RED drinking water assessment used finished (i.e., from the tap) drinking 
Page 11 of 33

water monitoring data from the EPA Office of Water to estimate chlorate concentrations in drinking 

water. 

3.3. Clean Water Act and Safe Drinking Water Act Programs 

Chlorates are not identified as a cause of impairment for any water bodies listed as impaired 

under section 303(d) of the Clean Water Act. However, impairment is noted in one case for one 

transformation product of sodium chlorate, chlorine dioxide. The impairment is in the Upper 

San Antonio River within San Antonio, TX. 

No Total Maximum Daily Load (TMDL) criteria have been developed for sodium chlorate or its 

transformation products. Aquatic life benchmarks have not been developed for sodium chlorate 

or its transformation products.

Chlorate is monitored under the Unregulated Contaminant Monitoring Rule (UCMR) for 

consideration under the Safe Drinking Water Act. Under the rule, public water systems are 

sampled within the drinking water distribution system. Results for UCMR 3 (published in 

October 2015) are summarized with respect to chlorate’s minimum reporting level (20 μg/L) and 

reference concentration (210 μg/L). Of 55,990 water samples taken in connection with the 

required monitoring, 55% were above the minimum reporting level and 15% were above the 

reference concentration. 4,749 public water systems reported results for UCMR 3 (USEPA, 

2015).

4. Environmental Fate and Transport

Chlorate is fully ionized in water, and is expected to dissociate immediately when added to moist 

soil. The very low vapor pressure and very high solubility of chlorate in water suggest that 

volatilization of chlorate from soil and water is an unlikely transport route. In addition, the very 

low octanol-water partition coefficient indicates that it is not a lipophilic chemical and therefore, 

has low potential to bioaccumulate in fish or other aquatic organisms.

As an anion, chlorate is not likely to adsorb to soil/sediment particulates. Therefore, on this basis 

alone, chlorate has a high leaching and run-off potential, particularly when heavy rainfall occurs 

immediately after application, when it can be washed off of the application site. These general 

routes of dissipation assume that chlorate remains as "chlorate". That is, potential redox reactions 

of chlorate are not taken into account.

The pesticide active species in sodium chlorate is the chlorate anion (ClO3

-

). Sodium chlorate is a 

strong oxidizer (electron acceptor), and its mode of action as a defoliant/desiccant is linked to its 

oxidizing properties. As an oxidizer (electron acceptor), the reactions of sodium chlorate in the 

environment are dominated by natural electron donor chemical species (reductants). 

A selection of sodium chlorate environmental fate and transport properties are summarized in 

Table 3 below.
Page 12 of 33

Table 3. Physical Chemical and Environmental Fate Properties of Sodium Chlorate.

Parameter Value Source/Comment

Selected Physical/Chemical Parameters

Chemical 

Structure

Sodium Chlorate RED

Empirical 

Formula

NaClO3 Sodium Chlorate RED

IUAPC Name Sodium chlorate Sodium Chlorate RED

CAS No. 7775-09-9 Sodium Chlorate RED

PC Code No. 073301 Sodium Chlorate RED

SMILES string: [Cl](=O)(=O)O.[Na] Sodium Chlorate RED

Molecular 

Weight 

106.5 g/mol Sodium Chlorate RED

Physical state Crystalline Solid Sodium Chlorate RED

Vapor pressure 7.3 x 10-16 (torr) Sodium Chlorate RED

Aqueous 

solubility 

1 x 106 mg/L at 25 deg C Sodium Chlorate RED

Henry’s Law 

Constant

1.0 x 10-22 atm-m3/mole Sodium Chlorate RED

log Kow -7.08 Sodium Chlorate RED

Persistence

Hydrolysis halflife (pH 5, 7, 9)Stable The chlorate anion is not expected to react with 

water

Aqueous 

photolysis halflife

Stable The chlorate anion does not absorb energy in the 

wavelength range of sunlight. Therefore, it lacks 

the necessary condition for a chemical to undergo 

direct photolysis.

Aerobic soil 

metabolism halflife (range in 

days)

Stable Persistence in soil is highly dependent on type

of soil, pH, other chemical species present in

soil, soil moisture temperature, precipitation

(i e., high spatial and temporal variability). A

registrant submitted open literature study 

indicates effects to sawa millet (a bioassay) 8 to 

22 weeks after application to soil (MRID 

05016686). The reference study reflects 

dissipation as chlorate is a soil sterilant and 

cannot be metabolized.

Anaerobic 

aquatic 

metabolism halflife 

Stable See “Aerobic soil metabolism”

Aerobic aquatic 

metabolism halflife (total 

system)

Stable See “Aerobic soil metabolism”
Page 13 of 33

Table 3. Physical Chemical and Environmental Fate Properties of Sodium Chlorate.

Parameter Value Source/Comment

Mobility

Adsorption/

desorption 

Miscible in water Chlorate is an anion. Thus, it is expected to be 

highly mobile in soils (high leaching and runoff 

potential). In addition, it has a very low potential 

to volatilize from soils and water (very low vapor 

pressure and extremely high solubility in water). 

4.1. Transformation Products

The major transformation products of sodium chlorate are chlorite (ClO2

-

), hypochlorite (ClO-), 

chlorous acid (HClO2), chlorine dioxide (ClO2), chlorine (Cl2), and chloride (Cl-). Chemical 

transformation from chlorate to the oxyanions and chlorine gases is dependent on redox 

conditions in the environment and transformation from chlorate to another oxyanion does not 

preclude transformation back to chlorate in differing redox conditions. The primary use of 

sodium chlorate as an antimicrobial pesticide is as a chlorine dioxide generator which is formed 

by mixing sodium chlorate with strong acids. Chlorate may also be oxidized to form perchlorate;

however this requires high pressure, electrical charge, heat, or high pH, and therefore the 

formation of perchlorate is considered unlikely under standard pesticidal use conditions.

5. Receptors

Tables 4 and 5 provide summaries of the most sensitive endpoints for the aquatic and terrestrial 

taxonomic groups, respectively, and most sensitive surrogate species tested to characterize the 

potential acute and chronic ecological effects of sodium chlorate. In addition, the tables provide 

a preliminary overview of the potential acute toxicity of sodium chlorate by providing the acute 

toxicity classifications. Additional details are provided below. 

5.1. Effects to Aquatic Organisms

Table 4. Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for 

Sodium chlorate

Taxonomic 

Group

Study 

Type

Surrogate 

Species

Toxicity Value

(mg a.i./L)

Acute Toxicity 

Classification or 

Adverse Effect 

Observed

Source

(Study 

classification)

Freshwater fish1

Acute Rainbow trout LC50 >1,000 Practically nontoxic

41887203

(Supplemental)

Chronic N/A N/A N/A No data

Freshwater 

invertebrates

Acute

Water flea 

EC50 = 920 Practically nontoxic

4374801

(Supplemental)

Chronic

NOAEC = 500

(no effects at 

highest level)

-- 46731301

(Acceptable)
Page 14 of 33

Table 4. Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for 

Sodium chlorate

Taxonomic 

Group

Study 

Type

Surrogate 

Species

Toxicity Value

(mg a.i./L)

Acute Toxicity 

Classification or 

Adverse Effect 

Observed

Source

(Study 

classification)

Estuarine/marine 

fish

Acute Sheepshead 

minnow

LC50 >1,000 Practically nontoxic

41887207

(Supplemental)

Chronic N/A -- No data2

Estuarine/marine 

invertebrates

Acute Mysid shrimp EC50 >1,000 Practically nontoxic

41887206

(Supplemental)

Chronic N/A -- No data2

Whole sediment; 

saltwater 

invertebrates

Chronic Saltwater 

amphipod N/A -- No data3

Whole sediment; 

freshwater 

invertebrates

Chronic Freshwater 

amphipod N/A -- No data3

Whole sediment; 

freshwater 

invertebrates

Chronic Freshwater 

midge N/A -- No data3

Aquatic plants 

and algae

Vascular Lemna minor EC50 = 133

NOAEC = 62.5 -- 46687601(Acceptable)

Nonvascular

Freshwater 

algae

(Selenastrum 

capricornutum)

EC50 = 43

NOAEC = 3.1 -- 41887201

(Acceptable)

1 Freshwater fish are surrogates for aquatic-phase amphibians. 2 The acute-to-chronic ratio (ACR) could not be employed since acceptable chronic studies were not available for

calculations. Conservative assumptions will be made in absence of data. 3 Not triggered per 40 CFR Part 158 based on chemical characteristics.

5.2. Effects to Terrestrial Organisms

Table 5. Summary of the Most Sensitive Endpoints from Terrestrial Toxicity Studies for 

Sodium chlorate

Taxonomic 

Group

Study 

Type

Surrogate 

Species

Toxicity Value Acute Toxicity 

Classification or 

Chronic Effects 

Observed

Source 

(Study 

classification)

Passerine Acute oral N/A No data N/A No data

Birds1

Acute oral Mallard 

duck

LD50 >2,510 mg a.i./kgbw Practically non-toxic 42149401

(Supplemental)

Subacute 

Dietary

Bobwhite 

quail

LC50 >5,620 mg a.i./kgdiet Practically non-toxic 41819908

(Acceptable)

Chronic NOAEC = 271 mg a.i./kgdiet 

Affected Endpoint: At 

964 mg a.i./kg-diet, 

effects were observed on 

egg production and 

thickness, embryonic 

survival, and hatchling 

body weight.

46729701

(Acceptable)
Page 15 of 33

Table 5. Summary of the Most Sensitive Endpoints from Terrestrial Toxicity Studies for 

Sodium chlorate

Taxonomic 

Group

Study 

Type

Surrogate 

Species

Toxicity Value Acute Toxicity 

Classification or 

Chronic Effects 

Observed

Source 

(Study 

classification)

Mammals

Acute Oral

Laboratory 

rat

LD50 >5,000 mg a.i./kgbw Practically non-toxic 41819901

(Acceptable)

Chronic

NOAEL = 500 mg a.i./kgdiet Affected Endpoint: 

None 

46524001

(Acceptable)

Terrestrial 

Invertebrates

Acute 

Contact -

Adults

Honey bee 

LD50 >116 μg a.i./bee

Practically non-toxic

47216001

(Acceptable)

Acute Oral 

- Adults LC50 >75 μg a.i./bee

Acute Oral 

- Larval No data N/A No data

Chronic 

Oral –

Adults

No data N/A No data

Chronic 

Oral -

Larval

No data N/A No data

Terrestrial 

plants

Seedling 

Emergence

Dicot 

(Lettuce)

EC25 >15.7 lb a.i./A

NOAEC = 1.72 lb a.i./A -- 47882301

Monocot (Supplemental)

(All)

EC25 >15.4 lb a.i./A

NOAEC = 15.4 lb a.i./A --

Vegetative 

Vigor

Dicot 

(Soybean)

EC25 = 3.68 lb a.i./A

NOAEC = 0.557 lb a.i./A -- 47882302

Monocot (Supplemental)

(Onion)

EC25 = 7.28 lb a.i./A

NOAEC = 0.177 lb a.i./A --

1 Birds represent surrogates for terrestrial-phase amphibians and reptiles. 

5.3. Ecological Incidents

The ecological incident information system (EIIS) is an OPP database that houses ecological 

incidents that have been reported to the Agency. When available, EIIS includes date and 

location of an incident, type and magnitude of effects observed in various species, use(s) of 

pesticides known or suspected of contributing to the incident, and results of any chemical residue 

analysis or other analyses conducted during incident investigation. EIIS incidents are 

categorized according to the certainty that the incident resulted from pesticide exposure. The 

Avian Monitoring System (AIMS) is a database administered by the American Bird Conservancy 

that contains publicly available data on reported avian incidents involving pesticides. Many of 

the incidents listed in this database are also in the EIIS. 

As of December 10, 2015, no incidents for sodium chlorate have been found in the databases.

The absence of reported incidents should not be construed as the absence of incidents. Incident 

reports for non-target organisms typically provide information only on mortality events and plant 

damage. Sublethal effects in organisms such as abnormal behavior, reduced growth and/or 
Page 16 of 33

impaired reproduction are rarely reported, except for some phytotoxic effects in terrestrial plants. 

EPA's changes in the registrant reporting requirements for incidents in 1998 may also account 

for a reduced number of reported incidents.

6. Exposure Pathways of Concern

The environmental fate and toxicity profile for sodium chlorate suggests that direct spray, spray 

drift, leaching and runoff represent the likely exposure pathways for terrestrial and aquatic nontarget organisms. Surface water and inhalation exposure pathways for ecological risk were also 

screened during development of this Problem Formulation using the SIP (Screening Imbibition 

Program) and STIR (Screening Tool for Inhalation Risk) screening methods to determine if they 

are potential pathways of concern or support requesting data. The results of the screening are not 

meant to provide a definitive analysis about any potential concern. STIR indicates the exposure

pathway via inhalation is of low concern for terrestrial vertebrates since volatilization of chlorate 

from soil and water is an unlikely transport route and chlorate is practically nontoxic to terrestrial 

vertebrates. SIP, on the other hand, indicates the exposure pathway via drinking water is of a 

potential concern for chronic effects to terrestrial vertebrates but not a concern on an acute 

exposure basis. This pathway will be explored further with the development of SIP v.2.0 in a 

future Ecological Risk Assessment. SIP and STIR are described in detail on EPA’s website1

, and 

the modeling can be found in Appendices 1 and 2.

7. Analysis Plan

7.1. Stressors of Concern

Ecological Risk Assessment

Based on available ecological toxicity data, it appears that the stressor of ecological concern for 

terrestrial and aquatic organisms is parent sodium chlorate only.

7.2. Measures of Exposure 

For conventional uses, EFED will use standard available models to evaluate potential exposures 

to aquatic and terrestrial organisms and/or exposure routes as described at 

http://www2.epa.gov/pesticide-science-and0assessing-pesticide-risks/models-pesticide-riskassessment.

For the antimicrobial uses, the active sodium chlorate labels result in five antimicrobial major 

use patterns: industrial processes and water systems, agricultural premises and equipment, 

commercial, institutional and industrial premises and equipment, antifouling coating and ballast 

water treatments, and aquatic areas. Specifically, sodium chlorate is used as a chlorine dioxide 

generator in: pulp/paper mill water systems, pasteurizer/cannery/retort water systems, 

recirculating and once-through cooling water towers, drinking water treatment systems, textile 

 1 http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/models-pesticide-risk-assessment#terrestrial
Page 17 of 33

mill water systems, sewage and wastewater systems, gas and oil recovery injection water 

systems, gas and oil fracturing fluid systems, ultrasonic tank water, photo processing wash water, 

leather processing water, animal drinking water, disinfectants and sanitizers for use in 

commercial, institutional, and industrial settings, ballast water treatments, and impounded lake, 

pond and reservoir water (including industrial wastewater). The chlorine dioxide Final Work 

Plan (docket number EPA-HQ-OPP-2015-0267-0005) states that EPA intends to conduct a 

down-the-drain assessment for chlorine dioxide used in once through cooling towers and it will 

be modeled for the revised risk assessment at that time. Therefore, no chlorine dioxide 

assessment will be done here.

Chemicals that are released down-the-drain can typically take from a few to several hours to 

reach wastewater treatment plant (WWTP) intakes following their discharge; and from several 

hours to roughly a day following their discharge down-the-drain to subsequently be discharged 

from WWTP to surface water. Data on WWTP dissipation have not been submitted for sodium 

chlorate, however sodium chlorate is completely ionized in water, thus producing sodium (Na+) 

and the chlorate (ClO3

-

) anion. Anions do not bind readily to soil or sediment particulates and, 

therefore, are expected to be very mobile. If chlorate did not undergo any redox reactions, it 

would be expected to be very mobile and to partition predominantly into the water. However, 

extensive redox reactions are expected to occur in the environment that will reduce the 

concentration of chlorate in the water column.

The Agency has created conceptual models for potential routes of environmental exposure which 

are included in “Conceptual Models for Environmental Exposure Pathways of Antimicrobial 

Pesticides,” (EPA-HQ-OPP-2014-0638-0002), found in the docket at www.regulations.gov.

Conceptual models for the uses listed above for sodium chlorate may be found at that docket. 

7.3. Measures of Effect 

Toxicity data presented in Section 5 of this problem formulation will be used to calculate risk 

quotients. Any additional information submitted by the registrant or found in the open literature 

prior to conduct of the risk assessment also will be considered. The open literature studies are 

identified using EPA’s ECOTOXicology database (ECOTOX) (USEPA, 2007c), which employs 

a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, 

and wildlife. The publically available database is available at http://www2.epa.gov/chemicalresearch/ecotoxicology-database. The evaluation of both sources of data can also provide insight 

into the direct and indirect effects of pesticides on biotic communities from loss of species that 

are sensitive to the chemicals and from changes in structure and functional characteristics of the 

affected communities.

7.4. Endangered Species Assessments

Consistent with EPA’s responsibility under the Endangered Species Act (ESA), the Agency will 

evaluate risks to federally listed threatened and endangered (listed) species from registered uses 

of pesticides in accordance with the Joint Interim Approaches developed to implement the 

recommendations of the April 2013 National Academy of Sciences (NAS) report, Assessing 
Page 18 of 33

Risks to Endangered and Threatened Species from Pesticides. The NAS report outlines 

recommendations on specific scientific and technical issues related to the development of 

pesticide risk assessments that EPA and the Services must conduct in connection with their 

obligations under the ESA and FIFRA. EPA will address concerns specific to sodium chlorate in 

connection with the development of its final registration review decision for sodium chlorate.

In November 2013, EPA, the U.S. Fish and Wildlife Service, National Marine Fisheries (the 

Services), and USDA released a white paper containing a summary of their joint Interim 

Approaches for assessing risks to listed species from pesticides. These Interim Approaches were 

developed jointly by the agencies in response to the NAS recommendations, and reflect a 

common approach to risk assessment shared by the agencies as a way of addressing scientific 

differences between the EPA and the Services. Details of the joint Interim Approaches are 

contained in the November 1, 2013 white paper2, Interim Approaches for National-Level 

Pesticide Endangered Species Act Assessments Based on the Recommendations of the National 

Academy of Sciences April 2013 Report.

Given that the agencies are continuing to develop and work toward implementation of the 

Interim Approaches to assess the potential risks of pesticides to listed species and their 

designated critical habitat, this ecological problem formulation supporting the Preliminary Work 

Plan for sodium chlorate does not describe the specific ESA analysis, including effects 

determinations for specific listed species or designated critical habitat, to be conducted during 

registration review. While the agencies continue to develop a common method for ESA analysis, 

the planned risk assessment for the registration review of sodium chlorate will describe the level 

of ESA analysis completed for this particular registration review case. This assessment will 

allow EPA to focus its future evaluations on the types of species where the potential for effects 

exists, once the scientific methods being developed by the agencies have been fully vetted. Once 

the agencies have fully developed and implemented the scientific methods necessary to complete 

risk assessments for listed species and their designated critical habitats, these methods will be 

applied to subsequent analyses of sodium chlorate as part of completing this registration review.

7.5. Endocrine Disruptor Screening Program

Sodium chlorate was not included in the first group of chemicals issued an order to conduct Tier 

1 EDSP testing. For additional information the EDSP program, visit 

http://www2.epa.gov/endocrine-disruption/endocrine-disruptor-screening-program-edspoverview.

8. Environmental Fate and Ecological Effects Data

8.1. Environmental Fate

 2 http://www2.epa.gov/endangered-species/interim-approaches-pesticide-endangered-species-act-assessments-basednas-report
Page 19 of 33

Table 6 identifies environmental fate studies by MRID that offer data for each guideline 

requirement, as well as study classifications and whether or not further data are needed in order 

to support risk assessment.

Table 6. Submitted Environmental Fate Studies and Data Needs for Sodium Chlorate

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct risk 

assessment?

Justification and 

Assumptions 

EPA will Make

in Absence of 

Data

835.2120 Hydrolysis 47116303 Waived No

835.2240 Aqueous photolysis 47116303 Waived No

835.2410 Soil photolysis 47116303 Waived No

850.3300

Activated Sludge 

Respiration Inhibition 

Test (ASRI)

No data N/A No No exposure to 

sodium chlorate

expected for AD 

uses, therefore data 

are not needed.

835.3110

835.3220

835.3240

835.3280

Biodegradability or 

Simulation Test No data N/A No

835.4100 Aerobic soil 

metabolism 47623303 Waived No

835.4300 Aerobic aquatic 

metabolism 47623303 Waived No

835.4400 Anaerobic aquatic 

metabolism 47623303 Waived No

835.1230

835.1240

Adsorption/ 

desorption and 

leaching

47623303 Waived No

835.6100 Terrestrial field 

dissipation

140486

5016686 Not Acceptable

Yes

(conventional 

uses)

EPA needs 

terrestrial field 

dissipation data

because our usual

models are not 

sufficient for 

estimating exposure 

to inorganic 

compounds reliant 

on redox chemistry 

for dissipation.

850.1730 Fish bioconcentration 47623303 Waived No

Environmental

Chemistry

Method: Water 

& its ILV

850.6100

Analytical method in 

water - -

Yes

(conventional 

uses)
Page 20 of 33

Table 6. Submitted Environmental Fate Studies and Data Needs for Sodium Chlorate

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct risk 

assessment?

Justification and 

Assumptions 

EPA will Make

in Absence of 

Data

Environmental

Chemistry

Method: Soil & 

its ILV

850.6100

Analytical method in 

soil - -

Yes

(conventional 

uses)

8.2. Effects

Tables 7 and 8 identify ecological effects studies by MRID that offer data for each guideline 

requirement, as well as study classifications and whether or not further data are needed in order 

to support risk assessment. Only technical grade active ingredient (TGAI) sodium chlorate data 

needs are discussed; studies with sodium chlorate formulated products and/or sodium chlorate 

transformation products are not being requested at this time. Rationales for the additional data 

requested are presented below.

Table 7. Submitted Aquatic Ecological Effects Studies and Data Needs for Sodium 

Chlorate

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data needed for 

assessment?

Justification 

and 

Assumptions 

EPA will 

Make in 

Absence of 

Data

850.1010

Freshwater 

invertebrate 

acute toxicity

41887204 Supplemental No --

850.1025

850.1035

Estuarine/Marine 

invertebrate 

acute toxicity 

41887205

41887206

Supplemental

Supplemental No --

850.1075 Freshwater fish 

acute toxicity 

41887202

41887203

Supplemental

Supplemental No --

850.1075

Estuarine/Marine 

fish acute 

toxicity 

41887207 Supplemental No --

850.1300

Freshwater 

invertebrate life 

cycle 

46731301 Acceptable No --

850.1350

Estuarine/Marine 

invertebrates life 

cycle 

No data N/A No

Triggered per 

40 CFR Part 

158 based on 
Page 21 of 33

Table 7. Submitted Aquatic Ecological Effects Studies and Data Needs for Sodium 

Chlorate

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data needed for 

assessment?

Justification 

and 

Assumptions 

EPA will 

Make in 

Absence of 

Data

850.1400

Estuarine/Marine 

fish early-life 

stage 

No data N/A No

use pattern but 

not needed

based on low 

chronic toxicity 

observed in the 

available 

information and 

the anticipated 

environmental 

exposure.

However, it is a 

data gap.

850.1400 Freshwater fish 

early-life stage No data N/A No

850.1500 Fish life cycle (None) (N/A) No

Not triggered 

per 40 CFR Part 

158 based on 

results of acute 

studies

850.1735 Whole sediment; 

acute 

invertebrate: 

freshwater

(None) (N/A) No Not triggered 

per 40 CFR Part 

158 based on 

chemical 

characteristics

850.1740 Whole sediment; 

acute 

invertebrate: 

marine

(None) (N/A) No

850.4400

Aquatic plant 

growth: Vascular 

plants

46687601 Acceptable No --

850.4500 Aquatic Plant 

Growth: Algal 41887201 Acceptable Yes (conventional uses)

1

Studies with 

the freshwater 

and marine 

diatoms and 

Cyanobacteria

are necessary 
Page 22 of 33

Table 7. Submitted Aquatic Ecological Effects Studies and Data Needs for Sodium 

Chlorate

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data needed for 

assessment?

Justification 

and 

Assumptions 

EPA will 

Make in 

Absence of 

Data

850.4550

Aquatic Plant 

Growth: 

Cyanobacteria

No data N/A Yes (conventional uses)

1

to satisfy 

standard data 

requirement 

for herbicides.

Without data, 

risk would be 

presumed for 

aquatic nonvascular 

plants, 

including listed 

species. 

1. These data are needed for conventional but not for antimicrobial uses since the antimicrobial uses are 

chlorine dioxide generators. The Agency has data for chlorine dioxide. 

Table 8. Submitted Terrestrial Ecological Effects Studies and Data Needs for 

Sodium Chlorate*

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

assessment?

Current Additional 

Data Need

850.2100 Avian oral 

toxicity 42149401 Supplemental

Yes

(conventional 

uses)

A passerine bird 

study is needed to 

satisfy standard data 

requirement for 

outdoor uses. Without 

data, risk would be 

presumed for 

passerines, including 

listed small-sized bird 

species.

850.2200 Avian dietary 

toxicity

41819907

41819908

Acceptable

Acceptable No --

850.2300 Avian 

reproduction

46729701

48097301

Acceptable

Acceptable No --

NonguidelineAvian 

inhalation (None) (N/A) No

The STIR model 

indicates exposure 

through inhalation is 

not a concern for birds. 
Page 23 of 33

Table 8. Submitted Terrestrial Ecological Effects Studies and Data Needs for 

Sodium Chlorate*

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

assessment?

Current Additional 

Data Need

850.3020

Adult honey 

bee acute 

contact 

toxicity

47216001 Acceptable No --

SS

Adult honey 

bee acute oral 

toxicity

47216001 Acceptable No --

850.3030

Honey bee 

residue on 

foliage

No data No data No

No data is available; 

however, EFED is not 

asking for the toxicity 

of residue on foliage 

since the bee contact 

LD50 was >25 μg 

a.i./bee, which is above 

the 11 μg a.i./bee 

criterion that triggers 

the study. AD will not 

require toxicity of 

residue data because 

sodium chlorate is not 

expected to be applied 

to wood used to 

construct honey bee 

enclosures.

850.3040 Field testing 

for pollinators No data No data

Yes

(conventional 

uses)

Pollinator Tier I, II 

and III studies with 

the honeybees are 

necessary to satisfy 

standard data 

requirement. Without 

data, risk would be 

presumed for 

pollinators, including 

listed species.

SS

Larval honey 

bee chronic 

oral toxicity

No data No data

Yes

(conventional 

uses)

SS

Adult honey 

bee chronic 

oral toxicity

No data No data

Yes

(conventional 

uses)

SS

Larval honey 

bee acute oral

toxicity

No data No data

Yes

(conventional 

uses)

SS

Field testing of 

residues in 

pollen and 

nectar

No data No data

Yes

(conventional 

uses)

SS

Semi-field 

testing for 

pollinators

No data No data

Yes

(conventional 

uses)
Page 24 of 33

Table 8. Submitted Terrestrial Ecological Effects Studies and Data Needs for 

Sodium Chlorate*

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

assessment?

Current Additional 

Data Need

850.4100

Tier I or II 

seedling 

emergence

47882301 Supplemental No

--

850.4150

Tier I or II 

vegetative 

vigor

47882302 Supplemental No

* No terrestrial assessment is considered necessary for the antimicrobial use patterns.

9. References 

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and 

Toxic Substances, Office of Pesticide Programs, Washington DC. January 23, 2004.

USEPA. 1998. Guidelines for Ecological Risk Assessment. Risk Assessment Forum, Office of 

Research and Development, Washington, D.C. EPA/630/R-95/002F. April 1998.

USEPA 2006. Environmental Fate and Effects Division RED for the Reregistration of

Inorganic Organics. Dated July 2006.

U.S. EPA, Office of Pesticide Programs, Antimicrobial Division, Risk Assessment and Science 

Support Branch. August 4, 2014. Conceptual Models for Environmental Exposure 

Pathways of Antimicrobial Pesticides. EPA-HQ-OPP-2014-

0638. http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2014-0638-0002

USEPA 2015. The Third Unregulated Contaminant Monitoring Rule (UCMR 3): Data Summary. 

Office of Water. October 2015. EPA 815-S-15-003
Page 25 of 33

Environmental Fate Bibliography 

161-1 Hydrolysis

MRID Citation Reference

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

161-2 Photodegradation-water

MRID Citation Reference

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

161-3 Photodegradation-soil

MRID Citation Reference

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

162-3 Anaerobic aquatic metab.

MRID Citation Reference

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

164-1 Terrestrial field dissipation

MRID Citation Reference

136388 Interregional Research Project No. 4 (1979) Results of Tests Concerning the 

Amount of Sodium Chlorate Residue Remaining in or on Guar Including a 

Description of the Analytical Method Used. (Compilation; unpublished study 

received Jun 15, 1979 under 9E2220; CDL:098331-A) 

140486 Interregional Research Project No. 4 (1976) The Results of Tests on the Amount 

of Sodium Chlorate Residue Remaining on or in Rice and Rice Straw Including a 

Description of the Analytical Method Used. (Compilation; unpublished study 

received Apr 6, 1976 under 6E1996; CDL:097358-A) 
Page 26 of 33

5016686 Konnai, M.; Takeuchi, Y.; Takematsu, T. (1974) Ringyoyo josozai no dojochu 

niokeru zanryu oyobi ido nikansuru kisoteki kenkyu_ ?Basic studies on the 

residues and movements of forestry herbicides in soil_| Utsunomiya Daigaku 

Nogakubu Gakujutsu Hokoku. ?Bulletin of the College of Agriculture, Utsunomiya 

University.| 9(1):95-112. 

164-2 Aquatic field dissipation

MRID Citation Reference

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

165-4 Bioaccumulation in fish

MRID Citation Reference

47623303 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

835.1230 Sediment and soil absorption/desorption for parent and 

degradates

MRID Citation Reference

47324203 Rice, C. (2008) Ecological Effects and Environmental Fate: Waiver Requests: 

Purate BWT. Unpublished study prepared by Ecochlor, Inc. 29 p.

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

835.1240 Soil column leaching

MRID Citation Reference

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

835.2120 Hydrolysis of parent and degradates as a function of pH 

at 25 C

MRID Citation Reference
Page 27 of 33

47116303 Rice, C. (2007) Application for Pesticide Registration Amendment Purate: 

Ecological Effects and Environmental Fate Waiver Requests. Unpublished study 

prepared by Keller and Heckman LLP and Eka Chemicals Inc. 19 p.

47324203 Rice, C. (2008) Ecological Effects and Environmental Fate: Waiver Requests: 

Purate BWT. Unpublished study prepared by Ecochlor, Inc. 29 p.

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

835.2240 Direct photolysis rate of parent and degradates in water

MRID Citation Reference

47116303 Rice, C. (2007) Application for Pesticide Registration Amendment Purate: 

Ecological Effects and Environmental Fate Waiver Requests. Unpublished study 

prepared by Keller and Heckman LLP and Eka Chemicals Inc. 19 p.

47324203 Rice, C. (2008) Ecological Effects and Environmental Fate: Waiver Requests: 

Purate BWT. Unpublished study prepared by Ecochlor, Inc. 29 p.

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

835.2410 Photodegradation of parent and degradates in soil

MRID Citation Reference

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

835.4100 Aerobic soil metabolism

MRID Citation Reference

47116303 4023 Rice, C. (2007) Application for Pesticide Registration Amendment Purate: 

Ecological Effects and Environmental Fate Waiver Requests. Unpublished study 

prepared by Keller and Heckman LLP and Eka Chemicals Inc. 19 p.

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

835.4300 Aerobic aquatic metabolism

MRID Citation Reference
Page 28 of 33

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

835.4400 Anaerobic aquatic metabolism

MRID Citation Reference

47623303 4035 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

835.6200 Aquatic field dissipation

MRID Citation Reference

47623303 4023 Rice, C. (2008) Purate BWT: Ecological Effects and Environmental Fate Waiver 

Requests. Project Number: 4023. Unpublished study prepared by Keller and 

Heckman LLP. 29 p.

Ecological Effects Bibliography (Acceptable or Supplemental studies 

only)

850.1010 Daphnid acute toxicity test

MRID Citation Reference

41887204 Ward, T.; Boeri, R. (1991) Acute Flow-through Toxicity of Sodium Chlorate to the 

Daphnid, Daphnia magna: Lab Project Number: 90144-AW. Unpublished study 

prepared by Resource Analysts, Inc. 23 p. 

850.1025 Oyster acute toxicity test (shell deposition)

MRID Citation Reference

41887205 Ward, T.; Boeri, R. (1991) Acute Flow-through Mollusc Shell Deposition Test of 

Sodium Chlorate: Lab Project Number: 90116-DE. Unpublished study prepared by 

Resource Analysts, Inc. 23 p. 

850.1035 Mysid acute toxicity test

MRID Citation Reference
Page 29 of 33

41887206 Ward, T.; Boeri, R. (1991) Acute Flow-through Toxicity of Sodium Chlorate to the 

Mysid, Mysidopsis bahia: Lab Project Number: 90117-DE. Unpublished study 

prepared by Resource Analysts, Inc. 23 p. 

850.1075 Fish acute toxicity test, freshwater and marine

MRID Citation Reference

41887202 Ward, T.; Boeri, R. (1991) Acute Flow-through Toxicity of Sodium Chlorate to the 

Bluegill Sunfish, Lepomis macrochirus: Lab Project Number: 90142-AW. 

Unpublished study prepared by Resource Analysts, Inc. 23 p. 

41887203 Ward, T.; Boeri, R. (1991) Acute Flow-through Toxicity of Sodium Chlorate to the 

Rainbow Trout, Oncorhynchus mykiss: Lab Project Number: 90143-AW. 

Unpublished study prepared by Resource Analysts, Inc. 23 p. 

41887207 Ward, T.; Boeri, R. (1991) Acute Flow-through Toxicity of Sodium Chlorate to the 

Sheepshead Minnow, Cyprinodon variegatus: Lab Project Number: 90115-DE. 

Unpublished study prepared by Resource Analysts, Inc. 23 p. 

850.1300 Daphnid chronic toxicity test

MRID Citation Reference

46731301 Thomas, P (2004) Chronic toxicity of Sodium Chlorate to Daphnia magna Under 

Semi-Static Conditions in a 21 Day Reproduction Test. Lab Project No. ICS-103 

Final Research Report; CER F03043 T 02006 ODC. Unpublished study prepared 

by Akzo Nobel Chemicals Research Environmental Chemistry Department, 

Arnhem, the Netherlands. 

850.2100 Avian acute oral toxicity test

MRID Citation Reference

42149401 Fink, R. (1990) Acute Oral LD50-Mallard Duck: [Sodium Chlorate]: Final Report: 

Project Nos. 176-101; WI-704. Unpublished study prepared by Wildlife 

International. 18 p. 

43412301 Harrison, E. (1980) Addendum to MRID #42149401: Acute Oral LD50-Mallard 

Duck: (Sodium Chlorate). Unpublished study prepared by Kerr-McGee Chemical 

Co. 5 p. 

850.2200 Avian dietary toxicity test

MRID Citation Reference

41819907 Long, R.; Beavers, J.; Smith, G. (1991) Sodium Chlorate: A Dietary LC50 Study 

with the Northern Bobwhite: Lab Project Number: 311-101. Unpublished study 

prepared by Wildlife International Ltd. 19 p. 
Page 30 of 33

41819908 Long, R.; Beavers, J.; Smith, G. (1991) Sodium Chlorate: A Dietary LC50 Study 

with the Mallard: Lab Project Number: 311-102. Un- published study prepared by 

Wildlife International Ltd. 19 p. 

850.2300 Avian reproduction test

MRID Citation Reference

48097301 Davidson, M. (2010) Sodium Chlorate: Avian Reproduction Study with the Mallard 

(Anas platyrhynchos): Final Report. Project Number: 09001. Unpublished study 

prepared by Genesis Laboratories, Inc. 229 p.

46729701 Arch, A. (2004) Sodium Chlorate: Assessment to Determine the Effects on 

Reproduction in the Bobwhite Quail (Colinus virginianus): Final Report. Project 

Number: K3AK1008. Unpublished study prepared by Central Science Laboratory. 

171 p.

850.3020 Honey bee acute contact toxicity

MRID Citation Reference

47216001 Wilkins, P. (2003) Acute Contact and Oral Toxicity of Sodium Chlorate to Honey 

Bees (Apis mellifera L.). Project Number: K3AK1001. Unpublished study prepared 

by Central Science Laboratory. 40 p.

850.4100 Seedling emergence, Tier II

MRID Citation Reference

47882301 Porch, J.; Krueger, H.; Kendall, T. (2009) Sodium Chlorate: A Toxicity Test to 

Determine the Effects of the Test Substance on Seedling Emergence of Ten 

Species of Plants: Final Report. Project Number: 680/101. Unpublished study 

prepared by Wildlife International, Ltd. 97 p.

850.4150 Vegetative vigor, Tier II

MRID Citation Reference

47882302 Porch, J.; Krueger, H.; Kendall, T. (2009) Sodium Chlorate: A Toxicity Test to 

Determine the Effects of the Test Substance on Vegetative Vigor of Ten Species 

of Plants: Final Report. Project Number: 680/102. Unpublished study prepared by 

Wildlife International, Ltd. 136 p.

850.4400 Aquatic plant toxicity test using Lemna spp. Tiers I and II

MRID Citation Reference
Page 31 of 33

46687601 Scheerbaum, D. (2003) Sodium Chlorate Aquatic Plant Toxicity Test, Lemna 

minor, Static, 7 days. Lab Project No. 030724AT/TLA93762. Unpublished study 

prepared by Dr. U. Noack Laboratorien, Sarstedt, Deutschland.

850.4500 Algal toxicity, Tiers 1 and II

MRID Citation Reference

41887201 Ward, T.; Boeri, R. (1991) Static Acute Toxicity of Sodium Chlorate to the 

Freshwater Alga, Selenastrum capricornutum: Lab Project Number: 90161-AW. 

Unpublished study prepared by Resource Analysts, Inc. 23 p. 
Page 32 of 33

Appendix 1. STIR

Input

Application and Chemical Information

Enter Chemical Name

Inorganic 

Chlorates

Enter Chemical Use All

Is the Application a Spray? (enter y or n) y

If Spray What Type (enter ground or air) air

Enter Chemical Molecular Weight (g/mole) 106.5

Enter Chemical Vapor Pressure (mmHg) 7.30E-16

Enter Application Rate (lb a.i./acre) 12.5

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) >2510

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 1.58

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) >5000

Enter Lowest Rat Inhalation LC50 (mg/L) >3.9

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3) 4.18E-12

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 5.26E-13

Adjusted Inhalation LD50 >7.87E+00

Ratio of Vapor Dose to Adjusted Inhalation LD50 <6.68E-14 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.20E+00

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 <1.53E-01 Exposure not Likely Significant

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3) 4.18E-12

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 6.61E-13

Adjusted Inhalation LD50 >2.32E+02

Ratio of Vapor Dose to Adjusted Inhalation LD50 <2.85E-15 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.51E+00

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 <6.50E-03 Exposure not Likely Significant
Page 33 of 33

Appendix 2. SIP

Table 1. Inputs

Parameter Value

Chemical name Sodium Chlorate

Solubility (in water at 25oC; mg/L) 1.00E+06

Mammalian LD50 (mg/kg-bw) >5000

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 25

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Avian LD50 (mg/kg-bw) >2510

Avian test species mallard duck

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 300

Bobwhite quail NOAEC (mg/kg-diet) 271

NOAEC (mg/kg-diet) for other bird species

Body weight (g) of other avian species

NOAEC (mg/kg-diet) for 2nd other bird species

Body weight (g) of 2nd other avian species

Table 2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 172000.0000 172000.0000

Adjusted toxicity value (mg/kg-bw) >3845.8028 19.2290

Ratio of exposure to toxicity <44.7241 8944.8163

Conclusion*

Drinking water alone is 

NOT a potential concern 

for mammals

Exposure through drinking 

water alone is a potential 

concern for mammals

Table 3. Avian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 810000.0000 810000.0000

Adjusted toxicity value (mg/kg-bw) >2884.2971 14.8838

Ratio of exposure to acute toxicity <0.0042 54421.6999

Conclusion*

Drinking water alone is 

NOT a potential concern 

for mammals

Exposure through drinking 

water alone is a potential 

concern for birds

*Conclusion is for Surface water exposure alone. This does not combine all routes of exposure. Therefore, 

when aggregated with other routes (i.e., diet, inhalation, dermal), pesticide exposure through Surface water

may contribute to a total exposure that has potential for effects to non-target animals.