United States Prevention, Pesticides EPA 738 R 06 014 Environmental Protection and Toxic Substances July 2006 Agency ( 7509P)

Reregistration Eligibility Decision ( RED) for Inorganic Chlorates ii REREGISTRATION ELIGIBILITY DECISION for Inorganic Chlorates Case No. 4049 Approved by:

______________________ Debra Edwards, Ph. D. Director, Special Review and Reregistration Division ________________________ Date iii TABLE OF CONTENTS Inorganic Chlorates Reregistration Eligibility Decision Team.................................................... v Glossary of Terms and Abbreviations ....................................................................................... vi Abstract .................................................................................................................................. viii I. Introduction....................................................................................................................... 1 II. Chemical Overview ....................................................................................................... 3 A. Regulatory History ........................................................................................................ 3 B. Chemical Identification   Sodium Chlorate ................................................................. 3 C. Use Profile...................................................................................................................... 3 D. Estimated Usage of Sodium Chlorate ........................................................................... 4 III. Summary of Inorganic Chlorates Risk Assessments ....................................................... 6 A. Human Health Risk Assessment ..................................................................................... 6 1. Toxicity of Sodium Chlorate ....................................................................................... 6 2. Carcinogenicity of Sodium Chlorate ........................................................................... 9 3. Sodium Chlorate Endocrine Effects ....................................................................... 10 4. Metabolites and Degradates .................................................................................... 10 5. Dietary Exposure and Risk ( Food)............................................................................ 11 6. Dietary Exposure and Risks ( Drinking Water) ...................................................... 13 7. Residential Exposure and Risk ............................................................................... 17 8. Aggregate Risk......................................................................................................... 20 9. Occupational Exposure and Risk............................................................................ 21 B. Environmental Fate and Effects Risk Assessment ..................................................... 27 1. Environmental Fate and Transport ........................................................................ 27 2. Ecological Exposure and Risk................................................................................... 28 IV. Risk Management, Reregistration, and Tolerance Reassessment.................................. 40 A. Determination of Reregistration Eligibility ................................................................... 40 B. Public Comments and Responses................................................................................ 40 C. Regulatory Position....................................................................................................... 41 1. Food Quality Protection Act Findings....................................................................... 41 2. Endocrine Disruptor Effects ................................................................................... 42 3. Cumulative Risks..................................................................................................... 42 4. Endangered Species................................................................................................. 43 D. Tolerance Reassessment Summary......................................................................... 44 E. Regulatory Rationale................................................................................................... 46 1. Human Health Risk Management .......................................................................... 46 2. Non Target Organism ( Ecological) Risk Management.......................................... 52 3. Summary of Mitigation Measures .......................................................................... 57 F. Other Labeling Requirements .................................................................................... 58 1. Endangered Species Considerations ....................................................................... 58 2. Spray Drift Management ........................................................................................ 59 V. What Registrants Need to Do ......................................................................................... 60 A. Manufacturing Use Products...................................................................................... 60 1. Generic Data Requirements .................................................................................... 60 2. Labeling for Manufacturing Use Products............................................................. 61 B. End Use Products........................................................................................................ 61 1. Additional Product Specific Data Requirements ................................................... 61 iv 2. Labeling for End Use Products............................................................................... 61 C. Labeling Changes Summary Table............................................................................. 61 D. Existing Stocks............................................................................................................. 61 v Inorganic Chlorates Reregistration Eligibility Decision Team Biological and Economic Analysis Assessment Rafael Prieto Alan Halvorson Nicole Zinn Andrew Lee Environmental Fate and Effects Risk Assessment Brian Anderson Silvia Termes Jim Goodyear Stephanie Syslo Health Effects Risk Assessment Susan Hummel Bonnie Cropp Kohlligian Abdullah Khasawinah Matthew Crowley Thurston Morton Gary Otakie Registration Support Juanita Gilchrist Jim Tompkins Risk Management Molly Clayton Kimberly Nesci Office of General Counsel Erin Koch vi Glossary of Terms and Abbreviations a. i. Active Ingredient aPAD Acute Population Adjusted Dose APHIS Animal and Plant Health Inspection Service ARTF Agricultural Re entry Task Force BCF Bioconcentration Factor CDC Centers for Disease Control CDPR California Department of Pesticide Regulation CFR Code of Federal Regulations ChEI Cholinesterase Inhibition CMBS Carbamate Market Basket Survey cPAD Chronic Population Adjusted Dose CSFII USDA Continuing Surveys for Food Intake by Individuals CWS Community Water System DCI Data Call In DEEM Dietary Exposure Evaluation Model DL Double layer clothing { i. e., coveralls over SL} DWLOC Drinking Water Level of Comparison EC Emulsifiable Concentrate Formulation EDSP Endocrine Disruptor Screening Program EDSTAC Endocrine Disruptor Screening and Testing Advisory Committee EEC Estimated Environmental Concentration. The estimated pesticide concentration in an environment, such as a terrestrial ecosystem. EP End Use Product EPA U. S. Environmental Protection Agency EXAMS Tier II Surface Water Computer Model FDA Food and Drug Administration FFDCA Federal Food, Drug, and Cosmetic Act FIFRA Federal Insecticide, Fungicide, and Rodenticide Act FOB Functional Observation Battery FQPA Food Quality Protection Act FR Federal Register GL With gloves GPS Global Positioning System HIARC Hazard Identification Assessment Review Committee IDFS Incident Data System IGR Insect Growth Regulator IPM Integrated Pest Management RED Reregistration Eligibility Decision LADD Lifetime Average Daily Dose LC50 Median Lethal Concentration. Statistically derived concentration of a substance expected to cause death in 50% of test animals, usually expressed as the weight of substance per weight or volume of water, air or feed, e. g., mg/ l, mg/ kg or ppm. LCO Lawn Care Operator LD50 Median Lethal Dose. Statistically derived single dose causing death in 50% of the test animals when administered by the route indicated ( oral, dermal, inhalation), expressed as a weight of substance per unit weight of animal, e. g., mg/ kg. LOAEC Lowest Observed Adverse Effect Concentration LOAEL Lowest Observed Adverse Effect Level LOC Level of Concern LOEC Lowest Observed Effect Concentration mg/ kg/ day Milligram Per Kilogram Per Day MOE Margin of Exposure MP Manufacturing Use Product MRID Master Record Identification ( number). EPA's system of recording and tracking studies submitted. vii MRL Maximum Residue Level N/ A Not Applicable NASS National Agricultural Statistical Service NAWQA USGS National Water Quality Assessment NG No Gloves NMFS National Marine Fisheries Service NOAEC No Observed Adverse Effect Concentration NOAEL No Observed Adverse Effect Level NPIC National Pesticide Information Center NTP National Toxicology Program NR No respirator OP Organophosphorus OPP EPA Office of Pesticide Programs ORETF Outdoor Residential Exposure Task Force PAD Population Adjusted Dose PCA Percent Crop Area PDCI Product Specific Data Call In PDP USDA Pesticide Data Program PF10 Protections factor 10 respirator PF5 Protection factor 5 respirator PHED Pesticide Handler's Exposure Data PHI Preharvest Interval ppb Parts Per Billion PPE Personal Protective Equipment PRZM Pesticide Root Zone Model RBC Red Blood Cell RAC Raw Agricultural Commodity RED Reregistration Eligibility Decision REI Restricted Entry Interval RfD Reference Dose RPA Reasonable and Prudent Alternatives RPM Reasonable and Prudent Measures RQ Risk Quotient RTU ( Ready to use) RUP Restricted Use Pesticide SCI GROW Tier I Ground Water Computer Model SF Safety Factor SL Single layer clothing SLN Special Local Need ( Registrations Under Section 24( c) of FIFRA) STORET Storage and Retrieval TEP Typical End Use Product TSH Thyroid Stimulating Hormone TGAI Technical Grade Active Ingredient TRAC Tolerance Reassessment Advisory Committee TTRS Transferable Turf Residues UF Uncertainty Factor USDA United States Department of Agriculture USFWS United States Fish and Wildlife Service USGS United States Geological Survey WPS Worker Protection Standard viii Abstract The Environmental Protection Agency ( EPA or the Agency) has completed the human health and environmental risk assessments for the Inorganic Chlorates and is issuing its risk management decision and tolerance reassessment. The risk assessments, which are summarized below, are based on the review of the required target database supporting the use patterns of currently registered products and additional information received through the public docket. After considering the risks identified in the revised risk assessments, comments received, and mitigation suggestions from interested parties, the Agency developed its risk management decision for uses of inorganic chlorates that pose risks of concern. As a result of this review, EPA has determined that inorganic chlorate containing products are eligible for reregistration, provided that risk mitigation measures are adopted and labels are amended accordingly. That decision is discussed fully in this document.

Sodium chlorate is an inorganic salt herbicide that was first registered in 1966. It is a defoliant and a desiccant that is primarily used on cotton, but it also has other agricultural and non agricultural uses. As a non selective herbicide it is used to kill grasses and weeds in industrial and non agricultural sites such as driveways, tennis courts, and recreational areas. The initial risk assessment indicated some ecological and occupational risks of concern. Risk assessments were revised based on refinements to the assessments as well as mitigation measures. Occupational and ecological risks resulting from non agricultural uses have been mitigated by reducing application rates, as well as limiting applications of sodium chlorate to spot treatments only. Use on rights of way and ditch banks will be cancelled. The Agency may require changes to the language of the sodium chlorate label in the future if deemed necessary under the Endangered Species Protection Program. 1 I. Introduction The Federal Insecticide, Fungicide, and Rodenticide Act ( FIFRA) was amended in 1988 to accelerate the reregistration of products with active ingredients registered prior to November 1, 1984. The amended Act calls for the development and submission of data to support the reregistration of an active ingredient, as well as a review of all submitted data by the U. S. Environmental Protection Agency ( referred to as EPA or " the Agency"). Reregistration involves a thorough review of the scientific database underlying a pesticide's registration. The purpose of the Agency's review is to reassess the potential hazards arising from the currently registered uses of the pesticide, to determine the need for additional data on health and environmental effects, and to determine whether or not the pesticide meets the " no unreasonable adverse effects" criteria of FIFRA.

On August 3, 1996, the Food Quality Protection Act ( FQPA) was signed into law. This Act amends FIFRA and the Federal Food, Drug, and Cosmetic Act ( FFDCA) to require reassessment of all existing tolerances for pesticides in food. FQPA also requires EPA to review all tolerances in effect on August 2, 1996, by August 3, 2006. In reassessing these tolerances, the Agency must consider, among other things, aggregate risks from non occupational sources of pesticide exposure, whether there is increased susceptibility of infants and children, and the cumulative effects of pesticides with a common mechanism of toxicity. When a safety finding has been made that aggregate risks are not of concern and the Agency concludes that there is a reasonable certainty of no harm from aggregate exposure, the tolerances are considered reassessed. EPA decided that, for those chemicals that have tolerances and are undergoing reregistration, tolerance reassessment will be accomplished through the reregistration process.

Of the inorganic chlorates listed as active ingredients ( i. e., sodium chlorate ( 073301), calcium chlorate ( 073302), potassium chlorate ( 073303), and magnesium chlorate ( 530200)), only sodium chlorate is present as an active ingredient in currently registered products. As such, sodium chlorate is the primary focus of the reregistration eligibility decision. 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. Since chlorite is also an active ingredient and is being considered in the chlorite/ chlorine dioxide reregistration eligibility decision ( case number 4043). The Agency will not consider the tolerances for chlorate reassessed until the assessment of chlorite is complete. As mentioned above, FQPA requires EPA to consider available information concerning the cumulative effects of a particular pesticide's residues and " other substances that have a common mechanism of toxicity." Potential cumulative effects of chemicals with a common mechanism of toxicity are considered because low level exposures to multiple chemicals causing a common toxic effect by a common mechanism could lead to the same adverse health effect as would a higher level of exposure to any one of these individual chemicals.

EPA has not made a common mechanism of toxicity finding as to parent sodium chlorate and any other substances, and sodium chlorate does not appear to produce a toxic metabolite that is in common with those produced by other substances. For the purposes of this reregistration eligibility decision ( RED), therefore, EPA has not assumed that the inorganic chlorates have a common mechanism of toxicity with other substances. For information regarding EPA's efforts 2 to determine which chemicals have a common mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the policy statements released by EPA's Office of Pesticide Programs concerning common mechanism determinations and procedures for cumulating effects from substances found to have a common mechanism on EPA's website at http:// www. epa. gov/ pesticides/ cumulative/.

This document presents EPA's revised human health and ecological risk assessments, its progress toward tolerance reassessment, and the reregistration eligibility decision for inorganic chlorates. The document consists of six sections. Section I contains the regulatory framework for reregistration/ tolerance reassessment; Section II provides a profile of the use and usage of the chemical; Section III gives an overview of the human health and environmental effects risk assessments; Section IV presents the Agency's decision on reregistration eligibility and risk management; and Section V summarizes the label changes necessary to implement the risk mitigation measures outlined in Section IV. Finally, the Appendices list related information, supporting documents, and studies evaluated for the reregistration decision. The revised risk assessments for inorganic chlorates are available in the Office of Pesticide Programs ( OPP) public docket under docket number OPP 2005 0507 available on the Agency's web page at http:// www. epa. gov/ oppsrrd1/ reregistration/ inorganicchlorates/. 3 II. Chemical Overview Of the inorganic chlorates listed as active ingredients ( i. e., sodium chlorate ( 073301), calcium chlorate ( 073302), potassium chlorate ( 073303), and magnesium chlorate ( 530200)), only sodium chlorate is present as an active ingredient in currently registered products. Sodium chlorate, calcium chlorate, and potassium chlorate are present as inert ingredients in currently registered products and exposures as a result of those uses are addressed herein. Sodium chlorate is a defoliant/ desiccant, and is used as an herbicide.

A. Regulatory History Sodium chlorate was first registered in February 23, 1966 by Value Gardens Supply, LLC, for use on both annual and perennial grasses and weeds for the following non agricultural use sites: garage areas, tennis courts, curbs, driveways, walks, and patios. On October 30, 1968, Helena Chemical Company registered it for use as a desiccant on agricultural sites ( sorghum and cotton). Currently, there are 56 active product registrations containing sodium chlorate as an active ingredient, including 11 technical ( manufacturing use) registrations, and 45 end use products ranging from 2.3% to 99.7% active ingredient. Sodium chlorate is currently manufactured by seven companies. The compound may be used in combination with other herbicides, such as atrazine, 2,4 D, bromacil, diuron, and sodium metaborate.

B. Chemical Identification   Sodium Chlorate Chemical Structure:

Common Names: Sodium chlorate, soda chlorate, chloric acid, sodium salt Chemical Name: Sodium chlorate Trade Names: Ferti Lome, Barespot, Tri Kil, Bareground, Prometon, Pramitol, Killsall, TriChlor Chemical Family: Inorganic salt Case Number: 4049 CAS Number: 7775 09 9 PC Code: 073301 Molecular Weight: 106.5 Empirical Formula: NaClO3 Technical Registrants: EKA Chemicals, ERCO Chemicals, Kerr McGee Chemical, Nexen Chemical USA, Moore Agricultural Products Company, Inc.

C. Use Profile The following is information on the currently registered uses of sodium chlorate, including an overview of use sites and application methods. A detailed table of the uses of sodium chlorate eligible for reregistration is available in Appendix A. 4 Type of Pesticide: Herbicide ( desiccant/ defoliant)

Target Pest: Broadleaf weeds Mode of Action: Non selective, contact herbicide that penetrates the cuticle causing cell death by altering the metabolic processes.

Use Sites Agricultural uses: Agriculturally, it is primarily used on cotton; however, it is also applied to a wide variety of other crops including, but not limited to, rice, corn, soybeans, dry beans, potatoes, sunflowers, flax, safflower, chili peppers ( for processing only), grain sorghum, and wheat.

Non agricultural Uses: Sodium chlorate is used on nonagricultural ( residential and industrial) areas such as rights of ways, building perimeters, ditch banks, bleachers, airport runways, vacant lots, fire hydrants, or as a pre paving treatment. It is also used by a small percentage of water treatment facilities for the generation of chlorine dioxide.

Use Classification: General Use Formulation Types: Agricultural products are all formulated as soluble concentrates/ liquids; non crop products are formulated as soluble concentrates/ liquids and granules or pellets/ tablets.

Application Methods: Sodium chlorate as a defoliant/ desiccant in agricultural settings is applied using aerial and groundboom equipment. As an herbicide in nonagricultural settings, it is applied using handheld equipment such as a low pressure handwands or sprinkling cans; it is also applied via groundboom or handgun sprayer application methods for larger commercial scenarios. Granular formulations can be applied using belly grinders, push type spreaders, tractor drawn spreaders, or by hand.

Application Rates: In agriculture, rates range from 6 pounds active ingredient per acre ( 6 lb ai/ A) to 12.5 lbs ai/ A. Industrial and other noncrop site rates range from 132 to 1032 lbs ai/ A, based on current labels. Sodium chlorate can be applied multiple times per year.

Application Timing: Sodium chlorate is applied post emergence.

D. Estimated Usage of Sodium Chlorate The primary non pesticidal use for sodium chlorate is as a precursor in chlorine dioxide generation through a closed system to bleach wood pulp/ paper. The pesticidal uses of sodium chlorate, including the agricultural uses as a defoliant/ desiccant, are a small percentage ( approximately 2%) of the total sodium chlorate used in the United States. According to Agency 5 data, approximately 2.8 million pounds of sodium chlorate are applied annually to agricultural, residential, and commercial use sites. A screening level usage analysis ( SLUA) of sodium chlorate from 1998 to 2005 indicates that approximately 2.1 million pounds of sodium chlorate are used annually on agricultural use sites in the United States. In terms of pounds applied, the greatest use is on cotton ( 1.9 million lbs ai per year); annually this represents approximately 5 percent of cotton acreage treated.

Exposure to the chlorate may also occur as a result of the drinking water disinfection process. This use and resulting exposure are explained in detail in this document. 6 III. Summary of Inorganic Chlorates Risk Assessments The following is a summary of EPA's revised human health and ecological risk assessments for inorganic chlorates, as presented fully in the documents, revised Inorganic Chlorates. HED Chapter of the Reregistration Eligibility Decision Document ( RED), dated January 26, 2006, and the revised Sodium Chlorate Ecological Risk Assessment, dated June 1, 2006. The purpose of this summary is to assist the reader by identifying the key features and findings of these risk assessments, and to help the reader better understand the conclusions reached in the assessments.

The human health and ecological risk assessment documents and supporting information listed in Appendix C were used to reach the safety finding and regulatory decision for sodium chlorate. While the risk assessments and related addenda are not included in this document, they are available from the OPP Public Docket, located at http:// www. regulations. gov, under docket number EPA HQ OPP 2005 0507.

EPA's use of human studies in the sodium chlorate risk assessment is in accordance with the Agency's Final Rule promulgated on January 26, 2006, related to Protections for Subjects in Human Research, which is codified in 40 CFR Part 26.

A. Human Health Risk Assessment The human health risk assessment incorporates potential exposure, hazard, and risks from all sources, which include food, drinking water, residential ( if applicable), and occupational scenarios. Aggregate assessments combine food, drinking water, and any residential or other non occupational ( if applicable) exposures to determine potential exposures to the U. S. population. The Agency's human health assessment considers all U. S. populations, including infants and young children. For more information on the inorganic chlorates human health risk assessment, see Revised Inorganic Chlorates. HED Chapter of the Reregistration Eligibility Decision Document ( RED) dated June 26, 2006.

1. Toxicity of Sodium Chlorate Toxicity assessments are designed to predict whether a pesticide could cause adverse health effects in humans ( including short term or acute effects such as skin or eye damage, and lifetime or chronic effects such as cancer, developmental effects, or reproductive effects), and the level or dose at which such effects might occur. The Agency has reviewed all toxicity studies submitted for sodium chlorate and has determined that the toxicological database is complete, reliable, and sufficient for reregistration. For more details on the toxicity and carcinogenicity of the inorganic chlorates, see Revised Inorganic Chlorates. HED Chapter of the Reregistration Eligibility Decision Document ( RED) dated January 26, 2006, which is available under docket number EPA HQ OPP 2005 0507.

a. Acute Toxicity Profile In acute toxicity tests, sodium chlorate is slightly toxic by the oral ( Toxicity Category IV), dermal ( Toxicity Category III), and inhalation routes ( Toxicity Category IV). Sodium chlorate crystals were mildly irritating to the rabbit eye ( Toxicity Category III), and were a 7 minimal to mild dermal irritant ( Toxicity Category III). Incident reports show that ingestion of toxic doses of sodium chlorate by humans produces gastritis, hemolysis, methemoglobinemia, hemoglobinurea, late toxic nephritis, and acute renal failure. Doses in excess of 100 mg/ kg are generally fatal to humans. The acute toxicity profile for sodium chlorate is summarized in Table 1 below.

Table 1. Acute Toxicity Profile  Sodium Chlorate Guideline Number Study Type MRID No. Results Toxicity Categorya 870.1100 Acute oral  Rats 41819901 LD50   5000 mg/ kg ( rat) IV 870.1200 Acute dermal  Rabbits 42497601 LD50 = > 2000 mg/ kg III 870.1300 Acute inhalation  Rats 41819903 LC50 = 5.59 mg/ L IV 870.2400 Acute eye irritation  Rabbit 00085090 00102998 41819904 mildly irritating III 870.2500 Acute dermal irritation  Rabbit 42497602 minimally irritating III 870.2600 Skin sensitization  guinea pigs 41819906 not a dermal sensitizer NA a. The technical acute toxicity values included in this document are for informational purposes only. The data supporting these values may or may not meet the current acceptance criteria.

b. FQPA Safety Factor Considerations The Federal Food, Drug, and Cosmetic Act ( FFDCA), as amended by the Food Quality Protection Act ( FQPA), directs the Agency to use an additional ten fold ( 10x) safety factor ( SF) to account for potential pre and postnatal toxicity and completeness of the data with respect to exposure and toxicity to infants and children. FQPA authorizes the Agency to modify the 10x FQPA SF only if reliable data demonstrate that the resulting level of exposure would be safe for infants and children.

For sodium chlorate, based on the hazard data and the exposure data, the FQPA SF was reduced to 1x. There was no pre or postnatal sensitivity or susceptibility observed in the submitted developmental studies in rats and rabbits or the 2 generation reproduction study in rats. However, there is a concern for developing offspring because of the effects of inorganic chlorate on thyroid function in rats. The thyroid hormone system plays a critical role in development, and it is therefore important to understand whether the thyroid hormone system in the developing young differs in response to thyroid toxicants compared to adults. There exists, therefore, an uncertainty regarding information on comparative thyroid response in young versus ( vs.) adult rats; however, a SF reflecting the uncertainty in comparative response is not necessary and the 10x FQPA SF can be removed ( reduced to 1x).

The rationale for removal of the FQPA SF lies in the comparative thyroid physiology of rats vs. humans. As a consequence of these dynamic differences, rats are much more sensitive to thyroid toxicants, such as chlorate, than humans and non human primates. As discussed in the section below, the chronic reference dose ( RfD) for inorganic chlorates is 0.03 mg/ kg/ day based on thyroid hypertrophy in adult rats. There is a study of the effects of chlorate on adult monkeys, in which the no observed adverse effects level ( NOAEL) for effects on blood thyroxine levels 8 was 58 mg/ kg/ day. If the NOAEL from the monkey study were used to derive a chronic RfD with uncertainty factors of 10x for interspecies extrapolation and 10X for intraspecies variability, and an FQPA SF of 10x reflecting uncertainties in effects to the young, the chronic RfD would be 0.06 mg/ kg/ day. The chronic RfD selected by the risk assessment team of 0.03 mg/ kg/ day derived from a chronic rat study, conducted by the National Toxicology Program ( NTP), is therefore protective of thyroid effects in primates ( including a 10X factor for uncertainty with respect to developing young) without the necessity of an additional uncertainty factor applied to the rat data.

In addition, the moderately refined dietary food assessment uses field trial data and percent crop treated estimates for all commodities, and the residential exposure assessment is based on reliable data; as such, exposure will not be underestimated. The dietary drinking water assessment uses residues in finished drinking water collected from water treatment facilities, which use chlorine dioxide or hypochlorite to treat drinking water. See Revised Inorganic Chlorates. HED Chapter of the Reregistration Eligibility Decision Document ( RED) dated January 26, 2006, for additional details.

c. Toxicological Endpoints The toxicological endpoints used in the human health risk assessment for sodium chlorate are listed in Table 2 below. Although several studies were considered, an acute reference dose ( aRfD) was not identified. None of the available studies provided an endpoint of toxicity attributable to a single exposure.

Sodium chlorate is unlikely to be absorbed by the skin based on its high water solubility and ionic nature; therefore, a risk assessment for dermal exposure is not needed and a dermal endpoint was not selected. For inhalation absorption, a default factor of 100% was used since, per Agency policy, the inhalation dose was derived from an oral endpoint.

The usual interspecies uncertainty factor is 10x, but there are several important quantitative dynamic differences between rats and humans with respect to thyroid function that permit an interspecies factor of less than 10x for a thyroid toxicant like sodium chlorate. The half life of thyroid hormone T4 in rats is approximately 12 hours, whereas in humans, the halflife is 5 9 days. The shorter half life in rats is likely related to a high affinity binding globulin for thyroxin that is present in humans, but absent in rodents. In the absence of a functional thyroid gland, a rat requires approximately 10 times more T4 than an adult human for full reconstitution. Constitutive thyroid stimulating hormone ( TSH) levels are nearly 25 times higher in rats than in humans, reflecting the increased activity of the thyroid pituitary axis in rats. Therefore, the 10x interspecies factor can be reduced to 3x based on dynamic considerations. The uncertainty factors ( UF) and safety factors used to account for interspecies extrapolation, intraspecies variability, and susceptibility of infants and children ( FQPA SF) are also described in Table 2. 9 Table 2. Summary of Toxicological Doses and Endpoints for Chlorate per se for Use in Human Risk Assessments for Inorganic Chlorates Exposure Scenario Dose, Uncertainty Factors FQPA Safety Factor and Level of Concern Study and Endpoint for Risk Assessment Acute Dietary Acute RfD= not applicable Although several studies were considered, an acute reference dose ( aRfD) was not identified. None of the available studies provided an endpoint of toxicity attributable to a single exposure.

Chronic Dietary ( all populations) BMDL1 = 0.9 mg/ kg/ day UF = 30 ( 3x interspecies and 10x intraspecies)

Chronic RfD = 0.03 mg/ kg/ day FQPA SF = 1X cPAD = Chronic RfD FQPA SF cPAD= 0.03 mg/ kg/ day Chronic Study in rats ( NTP, 2004). The LOAEL= 5 mg/ kg/ day based on increased thyroid gland follicular cell hypertrophy and follicular cell mineralization.

Short and Intermediate Term Incidental Oral Oral NOAEL = 30 mg/ kg/ day UF = 100 FQPA SF = 1X Residential LOC for MOE = 100 Subchronic study in rats McCauley et al, 1995. Pituitary effects ( vacuolization) and thyroid gland effects ( colloid depletion), body weight decrease and organ weight changes and reduction in erythrocyte counts and hemoglobin content at the LOAEL of 100 and 150 mg/ kg/ day in males and females, respectively Short, Intermediate, and Long Term Dermal Not applicable Dermal absorption is unlikely due to the ionic nature and water solubility of sodium chlorate Short, Intermediate, and Long Term Inhalation NOAEL = 30 mg/ kg/ day2 UF = 100 FQPA SF = 1X Residential LOC for MOE = 100 Occupational LOC for MOE = 100 McCauley et al, 1995 Cancer ( Oral, dermal, inhalation) Classification: Not likely to be carcinogenic to humans at doses that do not alter thyroid hormone homeostasis.

UF = uncertainty factor, FQPA SF = FQPA safety factor, NOAEL = no observed adverse effect level, LOAEL = lowest observed adverse effect level, PAD = population adjusted dose ( a = acute, c = chronic), RfD = reference dose, MOE = margin of exposure, LOC = level of concern, NA = Not Applicable 1. A NOAEL was not identified in this study. Therefore a bench mark dose ( BMD) analysis was performed and a BMDL of 28 mg sodium chlorate/ L ( 22 mg chlorate/ L) was calculated. This corresponds to 0.9 mg chlorate/ kg/ day oral dose. 2. A 100% inhalation absorption factor is used for extrapolating from an oral endpoint of toxicity.

2. Carcinogenicity of Sodium Chlorate Sodium chlorate is a thyroid toxicant producing thyroid gland follicular cell hypertrophy in rats and mice following chronic exposures. The Agency classified sodium chlorate as not likely to be carcinogenic to humans at doses that do not alter thyroid hormone homeostasis in accordance with the EPA policy, Assessment of Thyroid Follicular Cell Tumors, dated March 10 1998. This policy states that nonmutagenic pesticides that induce elevated levels of TSH and thyroid follicular cell tumors in the rat are classified as not likely to be carcinogenic to humans at doses that do not alter thyroid hormone homeostasis.

The preliminary results of a draft 2 year National Toxicology Program ( NTP) bioassay study on sodium chlorate to determine the potential of this chemical to induce tumors in laboratory animals ( rats and mice) ( NTP, 2004) showed evidence of thyroid gland follicular cell hyperplasia and follicular cell tumors in male rats. The effects may be attributed to changes in levels of thyroid hormones seen after administration of high doses of sodium chlorate. A final study report is expected later this year. In female mice there was equivocal and marginal evidence of increased pancreatic islet carcinoma. Sodium chlorate was negative in most bacterial gene mutation assays and in several cytogenetics tests, including a hypoxanthineguanine phosphoribosyl transferase ( HGPRT) assay in Chinese hamster ovaries and a micronucleus assay.

The Agency selected a chronic endpoint based on the thyroid effects from the NTP bioassay study using a benchmark dose analysis approximation of the NOAEL. This endpoint is protective for all populations, including children because children are not expected to be more susceptible to chlorate induced thyroid effects than adults. Therefore, the current chronic risk assessments presented in this document are protective of any cancer related effects for all populations. For more information, see the document Revised Inorganic Chlorates. HED Chapter of the Reregistration Eligibility Decision Document ( RED) dated January 26, 2006.

3. Sodium Chlorate Endocrine Effects The EPA is required under the FFDCA, as amended by FQPA, to develop a screening program to determine whether certain substances ( including pesticides active and other ingredients) " may have an effect in humans similar to an effect produced by a naturally occurring estrogen, or other such endocrine effects as the Administrator may designate." Following recommendations of its Endocrine Disruptor and Testing Advisory Committee ( EDSTAC), EPA determined that there was a scientific basis for including, as part of the program, the androgen and thyroid hormone systems, in addition to the estrogen hormone system.

The available toxicity studies on sodium chlorate demonstrate the thyroid gland to be its target of toxicity. The endpoints selected to assess chronic dietary risk and short and intermediate term oral and inhalation risks in this document are protective of the observed thyroid effects seen in the available toxicity studies. When additional appropriate screening and/ or testing protocols being considered under the Agency's Endocrine Screening Disruption Program have been developed, sodium chlorate may be subject to further screening and/ or testing to better characterize effects related to endocrine disruption.

4. Metabolites and Degradates The Agency reviewed the metabolism of the inorganic chlorates, and concluded that there are several residues of concern in food. In plants, the terminal residues of sodium chlorate in/ on plants are likely chlorate ( ClO3 ), chlorite ( ClO2 ), and chloride ( Cl). Based on published rat metabolism data, 11 terminal residues of sodium chlorate in animal tissues are also expected to be chlorate ( ClO3 ), chlorite ( ClO2 ), and chloride ( Cl).

In the environment, because chlorate is a strong oxidizing agent ( oxidation state V), it gets reduced to chlorine species in lower oxidation states, such as the oxyanions chlorite ( ClO2 , oxidation state III) and hypochlorite ( ClO, oxidation state I), chlorine dioxide ( oxidation state IV), and chloride ( oxidation state  I). Thus, at least some, and possibly a substantial, reduction of the chlorate resulting from the application of sodium chlorate is likely to occur in the field prior to any runoff to surface water. Under environmental ( terrestrial field) redox conditions, and based on chemical equilibria alone, the thermodynamically favored, end reduction product of chlorate in soil and in water is the chloride anion. Any intermediate chlorine dioxide that may form under environmental conditions will undergo photochemical reactions when exposed to sunlight. The chlorine oxyanions, chlorite and hypochlorite ( other possible more reduced intermediates in the ultimate reduction of chlorate to chloride), are strong oxidizers in themselves; thus, they are also reduced and/ or undergo disproportionation reactions. Although reduction reactions of chlorate, chlorite, and hypochlorite are said to occur very fast, how fast they occur is not known ( i. e., the actual rate constants in the environment are not known). Therefore, at any given time the distribution of reduced species ( type and concentration) cannot be estimated. However, it is unlikely that a single reduced species would be present. Chlorite is being considered in the chlorite/ chlorine dioxide reregistration eligibility decision ( case number 4043). ( See Revised Inorganic Chlorates. HED Chapter of the Reregistration Eligibility Decision Document ( RED) dated January 26, 2006, for additional details.)

5. Dietary Exposure and Risk ( Food)

Dietary exposure ( food only) to inorganic chlorates as the chlorate ion ( ClO3 ) may be expected from the following dietary exposure routes: 1) from sodium chlorate as an active ingredient in conventional ( agricultural) pesticides used on food crops; 2) from sodium chlorate and potassium chlorate as inert ingredients in conventional pesticides used on food crops or in poultry premises; 3) from secondary residues in meat/ milk/ poultry/ eggs due to residues in animal feedstuffs; 4) from sodium chlorate and calcium chlorate as inert ingredients in antimicrobial agents used as fruit, vegetable, and egg sanitizing washes, as treatments to mushrooms to control bacterial blotch, as treatments to seed used for sprouting, for conditioning live oysters, in poultry drinking water, in fish filleting, and in pecan cracking/ dyeing; and 5) as a potential redox of chlorine dioxide and sodium chlorite in conventional and antimicrobial pesticides; ( 6) from degradation of hypochlorites in antimicrobial agents used as fruit and vegetable washes; and, ( 7) from translocation of very small amounts of chlorate ion ( ClO3 ) by plants ( translocation of significant amounts would be phytotoxic to plants) from the environment which may be present as a result of inorganic chlorate pesticide uses.

No acute dietary endpoint was selected because effects attributable to a single dose were not seen in the available data. Chronic and cancer dietary analyses were conducted for the general U. S. population and various population subgroups.

a. Exposure Assumptions A chronic dietary risk assessment was conducted using the Dietary Exposure Evaluation 12 Model software with the Food Commodity Intake Database ( DEEM FCID   , Version 2.03), which uses food consumption data from the USDA's Continuing Surveys of Food Intakes by Individuals ( CSFII) from 1994 1996 and 1998. No food monitoring data are available for this risk assessment; therefore, exposure estimates in food were based on field trial data or, in the case of fruit/ vegetable/ other washes, were derived from a film thickness model. No chemicalspecific livestock metabolism or feeding data are available; exposure estimates in meat, milk, poultry, and eggs were derived from rat metabolism data, field trial data, and livestock reference information concerning feed consumption, tissue weights, and milk production. Default concentration factors ( no chemical specific processing data are available) and the effects of washing after foliar treatments were also incorporated into the risk assessment. Percent crop treated data were used in this analysis. Exposures were single point estimates; no residue decline was utilized.

b. Population Adjusted Dose A population adjusted dose, or PAD, is the reference dose ( RfD) adjusted for the FQPA SF. A risk estimate that is less than 100% of the acute PAD ( aPAD), the dose at which an individual could be exposed over the course of a single day and no adverse health effects would be expected, does not exceed EPA's level of concern. Likewise, a risk estimate that is less than 100% of the chronic PAD ( cPAD), the dose at which an individual could be exposed over the course of a lifetime and no adverse health effects would be expected, does not exceed EPA's level of concern. c. Acute Dietary Risk ( Food)

No acute dietary endpoint was selected because effects attributable to a single dose were not seen in the available data; therefore, an acute dietary risk assessment was not conducted.

d. Chronic Dietary Risk ( Food)

A chronic ( non cancer) dietary risk assessment was conducted for all potential chlorate dietary exposure routes using food consumption data from 1994 1996 and 1998. The chronic dietary exposure and risk estimates resulting from food intake were determined for the general U. S. population and various population subgroups.

The chronic ( non cancer) dietary ( food only) risk is below the Agency's level of concern for the general US population and all population subgroups. The most likely highest exposed population subgroup, children 1 2 years of age, was at 28% of the cPAD. See Table 3 below for details.

Table 3. Results of Chronic Dietary ( Food only) Exposure Analysis Population Subgroup cPAD ( mg/ kg/ day) Exposure ( mg/ kg/ day) % cPAD All populations 0.002730 9 All infants (< 1 year old) 0.03 0.004511 15 13 Table 3. Results of Chronic Dietary ( Food only) Exposure Analysis Children 1 2 years old 0.008376 28 Children 3 5 years old 0.006906 23 A cancer dietary risk assessment was conducted for all potential chlorate dietary exposure routes, using the same dietary ( food only) exposure estimates used in the chronic ( non cancer) dietary risk assessment for the US population. As discussed above, sodium chlorate is a thyroid toxicant producing thyroid gland follicular cell hypertrophy in rats and mice following chronic exposures, and may be producing follicular cell tumors in rats. The lack of mutagenicity indicates that the thyroid tumors are induced by a non mutagenic mechanism. Children are not expected to be more susceptible to chlorate induced thyroid effects than adults, and the endpoint selected for the thyroid effects is protective for all populations, including children. Therefore, as shown in Table 3 above, the chronic ( food only) dietary risk assessment is protective for cancer for the general US population, since the estimated risk does not exceed 100% of the cPAD.

6. Dietary Exposure and Risks ( Drinking Water)

Drinking water exposure to pesticides can occur through surface and groundwater contamination. Chronic dietary ( water only) risk assessments were conducted using DEEMFCID   Version 2.03 and drinking water consumption data from the USDA's CSFII from 1994 1996 and 1998. Exposures were single point estimates; no residue decline was utilized.

Drinking water exposure can result from several different uses for sodium chlorate. Agriculturally, sodium chlorate is used as a defoliant and dessicant, primarily on cotton; however, it is also applied to a wide variety of other crops including, but not limited to, rice, corn, soybeans, dry beans, potatoes, sunflowers, flax, safflower, chili peppers ( for processing only), grain sorghum, and wheat. As a non selective herbicide, it is applied to industrial/ noncrop areas such as rights of ways, building perimeters, ditch banks, bleachers, airport runways, vacant lots, fire hydrants, or as a pre paving treatment. Sodium chlorate is also used to generate chlorine dioxide, which is then used to bleach wood pulp/ paper and, in some cases, treat drinking water. All of these uses could result in chlorate reaching water systems. However, the majority of chlorate in drinking water is a result of drinking water disinfection treatment practices.

In the US, there are two primary methods of drinking water treatment. The first method is the generation of chlorine dioxide. In the second method, either gaseous chlorine or hypochlorite is used to produce free chlorine. Each of these methods, except the use of gaseous chlorine, produce chlorate as a disinfection byproduct ( DBP). The American Water Works Association ( AWWA) Disinfection Systems Committee tracks disinfection practices in US community water systems. AWWA's most recent comprehensive survey ( completed in 1998) estimated that, of all community water systems ( CWS), approximately 20% of CWSs serving populations greater than 10,000 use sodium hypochlorite ( 2% generated it on site), 8% use chlorine dioxide, and < 1% use calcium hypochlorite. For CWSs using groundwater and serving populations less than 10,000, the survey estimated that approximately 34% use sodium hypochlorite, none use chlorine dioxide, and at least 4.5% use calcium hypochlorite. For CWSs 14 using surface water and serving less than 10,000, the survey estimated that 17% use sodium hypochlorite, 6% use chlorine dioxide, and 9% use calcium hypochlorite.

For chlorine dioxide generation, both sodium chlorate and sodium chlorite are used as precursor materials, and both typically result in chlorate byproduct in finished drinking water. Sodium chlorite is more commonly used than sodium chlorate. The free chlorine disinfection process involves the use of either gaseous chlorine, or sodium or calcium hypochlorite, as precursor materials. Historically, gaseous chlorine has far more widely been used than hypochlorite to produce free chlorine. In recent years, primarily as a result of various homeland security measures, many drinking water systems are switching from gaseous chlorine to hypochlorite. While the use of gaseous chlorine does not result in chlorate byproduct in finished drinking water, the use of either sodium or calcium hypochlorite can produce chlorate byproduct, and this will be discussed in greater detail later in this section.

Chlorine Dioxide The use of chlorine dioxide can introduce chlorate into the finished water by several routes. Drinking water plants generally use sodium chlorite as a starting material ( i. e., feedstock) in the production of chlorine dioxide. Chlorate ion may be present as a contaminant in the sodium chlorite feedstock ( usually less than four percent of the active chlorite is chlorate). A typical range of chlorate carryover to the finished water from chlorite feedstock contamination is about 50 µ g/ L for a 1 mg/ L dose of chlorine dioxide. Technology to generate chlorine dioxide using sodium chlorate is now available to the drinking water industry, which introduces the possibility of chlorate carryover to the finished water from the chlorate feedstock. However, since this method is more technically complicated than the method used with sodium chlorite, sodium chlorite is far more commonly used in the generation of chlorine dioxide than sodium chlorate.

Chlorate ion ( ClO3 ) may also be produced due to inefficient generation of chlorine dioxide. Excess chlorine will favor the production of chlorate over chlorine dioxide, as will keeping the generator mixtures at highly alkaline ( pH > 11) or acidic ( pH < 3) conditions. If the concentrations of feedstock reactants are too low, or too much dilution water is added during the reaction, chlorate formation is also favored.

Chlorite ion ( ClO2 ) is a major degradation product resulting from the reaction of chlorine dioxide with inorganic and organic constituents in the water. When free chlorine is used after the application of chlorine dioxide in the treatment process, chlorite is oxidized to chlorate. This conversion will continue over time as the water travels through the distribution system. Chlorate ion is also formed by photodecomposition of chlorine dioxide when treated water is exposed to bright sunlight in open basins.

There are ways that water systems can control the levels of chlorate in drinking water, and these will be discussed in Section 4 of this document. 15 Hypochlorite Chlorine based disinfectants, such as free chlorine, are also used by drinking water treatment systems to treat drinking water. Some of these water systems use sodium hypochlorite or calcium hypochlorite as their source of free chlorine. Chlorate ion can be formed in these products during the manufacturing process, but the decomposition of hypochlorite solutions during storage is the more significant source of chlorate ion in systems using hypochlorite.

Chlorate ion concentrations increase between the time of manufacture and delivery to the water plant. The rate at which hypochlorite ion disproportionates to chlorate is influenced by concentration of hypochlorite, pH, and temperature. As with the chlorine dioxide methods, there are several ways that water systems using hypochlorite can control the levels of chlorate; these will be discussed in Section 4 of this document.

a. Drinking Water Exposure Data on the occurrence of chlorate ion in drinking water were available from two primary sources: 1) the Information Collection Rule ( ICR) Auxiliary 1 Database, Version 5.0, and 2) the American Water Works Association Research Foundation ( AwwaRF) study on the control of chlorate ion in hypochlorite solutions. The ICR data is the more extensive data set, and the water systems represented in the ICR database serve 60% of the total US population. The EPA Office of Water ( OW) issued the ICR in order to collect data to support future regulation of microbial contaminants, disinfectants, and disinfection byproducts. Monitoring for chlorate was included in the ICR, since chlorate is a disinfection byproduct. Source water and drinking water were monitored for chlorate ion between July 1997 and December 1998. Water systems serving a population of at least 100,000 were required to monitor for chlorate ion at treatment plants using chlorine dioxide or hypochlorite solutions in the treatment process. Plants using chlorine dioxide collected monthly samples of the source water entering the plant, the finished water leaving the plant, and at three sample points in the distribution system ( near the first customer, an average residence time, and a maximum residence time). Plants using hypochlorite solutions were required to collect quarterly samples of the water entering and leaving the plant. If chlorine dioxide or hypochlorite solutions were used intermittently at a plant, chlorate ion samples were only required in sample periods in which they were in use.

The ICR Database was considered the more appropriate data source for estimating average chlorate concentrations in drinking water from individual water treatment plants. The AwwaRF study is a less robust data set, consisting of only one sample per utility, whereas the ICR database included multiple samples over an 18 month period. Both the AwwaRF study and the ICR data reveal high concentrations of chlorate ion to be a local problem affecting a relatively small number of systems.

Based on the ICR monitoring data, the Agency was able to assess exposure to chlorate in drinking water. The ICR data confirm the presence of chlorate in untreated source water which may be the result of agricultural and other uses of sodium chlorate. However, the chlorate concentrations in ambient water are generally very low and are minor compared to those observed in drinking water treated with chlorine dioxide or hypochlorite. Table 4 below 16 summarizes the annual chlorate concentrations calculated for each plant. The data listed for hypochlorite plants is the average chlorate concentrations, taken from samples collected at the entry point to a distribution system. The figures for chlorine dioxide in the next two columns ( chlorine dioxide plans and combined hypochlorite and chlorine dioxide plants) represent the distribution system average chlorate concentrations. As previously explained, for chlorine dioxide plants, samples were collected from three points in the distribution systems; the data from these three collection points were used to calculate a distribution system average. Monitoring in the distribution system was required by the ICR, since chlorate concentrations are expected to change as the water travels through the distribution system. The concentration changes, because many of the chlorine dioxide systems use chlorine to maintain a disinfectant residual in the distribution system, and chlorine reacts with the chlorite ion to form chlorate ion.

Table 4. Distribution of Average Annual Chlorate Concentrations  ICR Data Hypochlorite Plantsa Chlorine Dioxide Plants b Combined Hypochlorite and Chlorine Dioxide Plants Number of Public Water Systems 44 22 66 Number of Water Treatment Plants 61 29 90 Chlorate Concentration ( µ g/ L)

10th Percentile 23 52 24 20th Percentile 37 79 53 50th Percentile ( Median) 99 129 108 80th Percentile 155 217 179 90th Percentile 239 264 242 Maximum 502 691 691 a. Concentrations for hypochlorite plants are an average of samples collected from distribution system entry points. b. For chlorine dioxide pants, the distribution system average concentration was calculated for each WTP using the three distribution system sample points.

b. Acute Dietary Risk ( Drinking Water)

No acute dietary endpoint was selected because effects attributable to a single dose were not seen in the available data; therefore, an acute dietary ( drinking water only) risk assessment was not conducted.

c. Chronic Dietary Risk ( Drinking Water)

The chronic dietary ( water only) risk assessment for chlorate in drinking water, using the highest annual average concentration estimated at 0.69 mg/ L, is below 100% of the cPAD, and therefore, is below the Agency's level of concern for the general US population and all population subgroups except infants (< 1 year of age). The highest exposed subgroup, infants, was 159% of the cPAD, based on the highest annual average concentration of chlorate in Table 4 ( 0.69 mg/ L). Using the 90th percentile annual average concentration estimated at 0.24 mg/ L, the chronic ( non cancer) dietary ( water only) risk for infants was 55% of the cPAD. Also for infants, using the median annual average concentration estimated at 0.11mg/ L, the risk was 25% 17 of the cPAD. See Table 5 below for details.

Table 5. Sum Table 5. Summary of Estimated Chronic Dietary ( water only) Exposure and Risk for Sodium Chlorate by Average Annual Concentration in Large Drinking Water Systems % cPAD Population Subgroup cPAD mg/ kg/ day Water Estimated at the Highest Annual Average ( 0.69 mg/ L) Water Estimated at the 90th Percentile Annual Average ( 0.24 mg/ L) Water Estimated at the Median Annual Average ( 0.11 mg/ L)

General U. S. Population 49 17 8 All Infants (< 1 yr) 159 55 25 Children 1 2 yrs 72 25 12 Children 3 5 yrs 67 23 11 Children 6 12 yrs 47 16 7 Youth 13 19 yrs 35 12 6 Adults 20 49 yrs 45 16 7 Adults 50+ yrs 48 17 8 Females 13 49 yrs 0.03 45 16 7 7. Residential Exposure and Risk Residential exposure assessments consider all potential non occupational pesticide exposure, other than exposure due to residues in foods or in drinking water. For sodium chlorate, the Agency has evaluated potential exposure and risk to sodium chlorate for homeowners who handle ( mix, load, and apply) products containing sodium chlorate. The Agency also evaluated potential post application exposure and risk to adults and children entering sodium chlorate treated areas, such as lawns, or patio areas. Since the episodic nature of residential exposure for sodium chlorate is inconsistent with the mechanism of chlorate carcinogenicity, a residential cancer risk assessment was not conducted.

To estimate residential non cancer ( dermal and inhalation) risks, the Agency calculates a margin of exposure ( MOE), which is the ratio of the NOAEL selected for risk assessment to the exposure. This MOE is compared to a level of concern which is the same value as the uncertainty factor ( UF) applied to a particular toxicity study. The standard UF is 100x ( 10x to account for interspecies extrapolation and 10x for intraspecies variation), plus any additional FQPA SF retained due to concerns unique to the protection of infants and children. The FQPA SF for sodium chlorate is reduced to1x for reasons explained above; thus, the Agency's LOC is 100.

a. Residential Handler Risks The Agency determined that there is the potential for residential handlers to be exposed to sodium chlorate in outdoor residential settings during the application of conventional pesticide 18 products containing sodium chlorate as the active ingredient. Sodium chlorate can be used as a non selective herbicide in outdoor residential environments as a spot treatment or edging treatment around patios, along fence lines, lawn edges, around foundations, underneath or around wood decks, and in cracks and crevices of driveways. Although there is the potential for dermal exposure by residential handlers, sodium chlorate is an inorganic salt; therefore, significant absorption of sodium chlorate through intact skin is not expected. Hence, only a short term risk assessment for residential handlers exposed to sodium chlorate via the inhalation exposure route was conducted.

The risk assessment considered seven residential exposure scenarios based on the types of equipment and techniques that can potentially be used to make sodium chlorate applications, such as handheld equipment ( hand wand sprayers) and ready to use ( RTU) methods ( sprinkler cans). The use patterns assessed are representative of the range of sodium chlorate residential uses.

The Agency considered residential handler exposure scenarios to be short term ( 1 30 days) only due to infrequency of use associated with homeowner products. The residential risk assessment is also based on estimates of what and how much homeowners would typically treat, such as the size of the lawn or garden, based on the Agency's standard operating procedures for residential exposures. For more information on the daily volume handled and the area treated used in each residential handler scenarios, refer to Inorganic Chlorates: Residential and Occupational Exposure Assessment for the Reregistration Eligibility Decision Document, dated January 26, 2006.

Risk to homeowners handling sodium chlorate products are below the Agency's LOC. The inhalation MOEs for all scenarios assessed are greater than 100 ( ranging from 370 to 710,000). See Table 6 for further detail.

Table 6. Sodium Chlorate Residential Risk Estimates1 Exposure Scenario ( Scenario #) Daily Area Treated Crop/ Target Application Rate Inhalation MOE2 Mixing/ loading/ applying liquids with a low pressure hand wand sprayer 1000 ft2/ day Spot/ edging treatment 23.7 lb ai/ 1000 ft2 3000 Loading/ applying RTU liquid with a trigger pump sprayer 1 gallon/ day Spot/ edging treatment 0.196 lb ai/ gallon 87000 Mixing/ loading/ applying liquids with a sprinkler can 1000 ft2/ day Spot/ edging treatment 23.7 lb ai/ 1000 ft2 5200 Applying liquid with a RTU sprinkler can 1 gallon / day Spot/ edging treatment 0.27 lb ai/ gallon 710000 Applying granules by hand 1000 ft2/ day Spot/ edging treatment 12 lb ai/ 1000 ft2 370 Loading and applying granules with a 1000 ft2/ day Spot/ edging treatment 12 2800 19 Table 6. Sodium Chlorate Residential Risk Estimates1 Exposure Scenario ( Scenario #) Daily Area Treated Crop/ Target Application Rate Inhalation MOE2 belly grinder lb ai/ 1000 ft2 Loading and applying granules with a push type spreader 1000 ft2/ day Spot/ edging treatment 12 lb ai/ 1000 ft2 200000 1. Residential exposures assessments do not include personal protective equipment ( PPE). 2. Inhalation MOE = Oral NOAEL ( 30 mg/ kg/ day) / Daily Inhalation Dose. The LOC for MOE is 100.

b. Residential Post Application Risks The Agency uses the term " post application" to describe exposures to individuals that occur as a result of being in an environment that has been previously treated with a pesticide. Unlike residential handler exposure, where the EPA assumed only adults will be handling and applying sodium chlorate products, individuals of varying ages can potentially be exposed when reentering or performing activities in areas that have been previously treated. For products containing sodium chlorate as the active ingredient, a post application exposure assessment was not conducted for the following reasons:

  Although potential for post application dermal exposure in residential and occupational settings exists, sodium chlorate is an inorganic salt; therefore, significant absorption of sodium chlorate through the skin is not expected.   Post application inhalation exposure is not expected due to a negligible vapor pressure.   Post application exposure assessments for residential settings ( dermal and incidental oral) are not typically performed for spot treatments/ edging treatments.

However, for products containing sodium chlorate as an inert ingredient, there is the potential for post application exposure in outdoor residential settings from entering areas previously treated. Therefore, a residential post application risk assessment was conducted based on this use. As an inert ingredient in herbicide formulations professionally broadcast on residential sites, there is potential for children to have incidental oral exposures ( i. e., hand tomouth object to mouth, and soil ingestion). As stated above, residential post application exposures via dermal and inhalation routes are not of concern. Although there is the potential for post application dermal exposure in residential settings, sodium chlorate is an inorganic salt; therefore, significant dermal absorption of sodium chlorate through intact skin is not expected. Post application inhalation exposure for sodium chlorate is not expected due to negligible vapor pressure.

A series of conservative assumptions and exposure factors served as the basis for completing the residential post application risk assessment, and those assumptions and factors are listed in detail in the previously referenced Inorganic Chlorates: Residential and Occupational Exposure Assessment for the Reregistration Eligibility Decision Document, dated January 26, 2006. The risk estimates for incidental oral exposures to sodium chlorate as an inert ingredient in other pesticide formulations and the highest exposed population subgroup are 20 shown in Table 7. The combined oral MOE of 23,000 is greater than 100; therefore, the risk is below the Agency's level of concern.

Table 7. Residential Post application Risk Estimates for Sodium Chlorate as an Inert Ingredient in Herbicide Products Applied Professionally to Residential Sites Population Subgroup Scenario Route MOE Combined MOE Hand to Mouth Oral 29000 Object to Mouth Oral 110000 Child Soil Ingestion Oral 8600000 23000 8. Aggregate Risk The FQPA amendments to the Federal Food, Drug, and Cosmetic Act ( FFDCA, Section 408( b)( 2)( A)( ii)) require " that there is a reasonable certainty that no harm will result from aggregate exposure to the pesticide chemical residue, including all anticipated dietary exposures and other exposures for which there is reliable information." Aggregate exposure will typically include exposures from food, drinking water, residential uses of a pesticide, and other nonoccupational sources of exposure.

In accordance with FQPA, the Agency must consider and aggregate pesticide exposures and risks from three major sources: food, drinking water, and if applicable, residential or other non occupational exposures. In an aggregate assessment, exposures from relevant sources are added together and compared to quantitative estimates of hazard ( e. g., a NOAEL), or the risks themselves can be aggregated. When aggregating exposures and risks from various sources, the Agency considers both the route and duration of exposure. Aggregate exposure and risk assessments for sodium chlorate include the following scenarios: short term ( food + water + residential handler) and chronic dietary ( food + drinking water). Results of the aggregate risk assessment are summarized here, and are discussed more extensively in the document: Revised Inorganic Chlorates. HED Chapter of the Reregistration Eligibility Decision Document ( RED) dated January 26, 2006, which is available in the public docket and on the internet.

a. Short Term Aggregate Risk ( food + drinking water)

Short term aggregate risk was assessed for adults only, using the highest exposure scenario ( inhalation exposure while applying granules by hand). Short term aggregate risk for children would be less than the short term aggregate risk for adults ( MOE of 324), because the short term MOE for residential risk to children from the use of sodium chlorate as an inert is significantly greater ( i. e., lower risk) than the residential handler short term MOE for adults. Thus, all short term aggregate risks are below the Agency's level of concern ( i. e., MOEs are greater than 100), as presented in Table 8. 21 Table 8. Short Term Aggregate Risk Calculations Population Target Aggregate MOE MOE Food + water MOE inhalation Aggregate MOE ( food + water + residential)

Adult 100 1715 400 324 b. Chronic Aggregate Risk ( food + drinking water)

Since no chronic residential ( non dietary) exposure scenarios have been identified, the chronic aggregate risk assessment considers exposure only through food and drinking water. To assess aggregate risks from chronic food and drinking water exposure, the Agency used conservative Tier 1 chronic food estimates and incorporated drinking water monitoring data collected under the Information Collection Rule ( ICR). For chronic aggregate dietary risks, using the estimated highest annual average of drinking water concentrations, food and drinking water chronic exposure estimates were above the Agency's level of concern for all infants (< 1 year old), the most highly exposed population, at 174% cPAD. Chronic aggregate dietary risks were at the Agency's level of concern ( 100 % cPAD) for children 1 2 years of age. All other population subgroups were < 100 % cPAD, and therefore, below the Agency's level of concern. At the 90th percentile and median annual average water concentration, all population subgroups are below the Agency's LOC. The results of this assessment for sodium chlorate are presented below in Table 9.

Table 9. Summary of Chronic Dietary Aggregate ( food + drinking water) Risk for Sodium Chlorate % cPAD ( food + drinking water)

Population Subgroupa cPAD ( mg/ kg/ day) Highest Annual Average ( 0.69 mg/ L) 90th Percentile Annual Average ( 0.24 mg/ L) Median Annual Average ( 0.11 mg/ L)

General US Population 58 26 17 All Infants (< 1 yr) 174 70 40 Children 1 2 yrs 100 53 39 Children 3 5 yrs 0.03 90 47 34 9. Occupational Exposure and Risk The occupational risk assessment addresses risks to workers who may be exposed to sodium chlorate when mixing, loading, or applying a pesticide ( i. e., handlers), and when entering treated sites for routine tasks ( post application). Please see Table 2 for the toxicological endpoints used in the sodium chlorate occupational assessment. Based on the registered use patterns of sodium chlorate, short term ( 1 30 days) and intermediate term ( 1 6 months) occupational exposures were assessed; long term (> 6 months) exposure is not expected. 22 Exposure for workers generally occurs via the dermal or inhalation route; however, since sodium chlorate is an inorganic salt, and significant absorption of sodium chlorate through the skin is not expected, a dermal toxicological endpoint was not selected. As such, a risk assessment for dermal exposure was not performed. Similarly, post application exposure was not assessed due to the physical and chemical characteristics of sodium chlorate as an inorganic salt; no significant amount of sodium chlorate is expected to be absorbed through the skin, and the vapor pressure is negligible. Further, for the antimicrobial use of sodium chlorate in chlorine dioxide generation for drinking water treatment, exposure to chlorate is expected to be negligible because of its conversion to chlorine dioxide inside the closed generators. Post application exposure to chlorine dioxide will be addressed in the chlorine dioxide risk assessment and RED.

The occupational assessment estimates non cancer risks using the MOE approach. MOEs greater than 100 are below the Agency's level of concern for short and intermediate term occupational exposure.

Occupational exposure to sodium chlorate was assessed using data from the Pesticide Handler Exposure Database ( PHED) and Outdoor Residential Exposure Task Force ( ORETF). In addition, standard default assumptions pertaining to average body weight, work day, and area treated daily were used to calculate risk estimates. Application rates used in this assessment are derived directly from current sodium chlorate labels. Worker exposure and risk estimates are based on the best data currently available to the Agency.

The occupational risk assessment is summarized here. For further detail, see the following documents: ( 1) Revised Inorganic Chlorates. HED Chapter of the Reregistration Eligibility Decision Document ( RED) dated January 26, 2006; ( 2) Inorganic Chlorates: Occupational and Residential Exposure Assessment for the Reregistration Eligibility Decision ( RED) Document ( Case 4049), dated June 13, 2005; and ( 3) Sodium Chlorate: Occupational and Residential Exposure Assessment of Antimicrobial Uses for the Reregistration Eligibility Decision Document dated January 24, 2005.

a. Handler Risks Occupational handler exposure assessments are conducted by the Agency using different levels of protection. The Agency typically evaluates all exposures with minimal protection and then adds protective measures in a tiered approach to determine the level of protection necessary to obtain appropriate MOEs. The lowest level ( baseline) includes long sleeve shirts, long pants, shoes, and socks. A single layer of PPE includes the addition of chemical resistant gloves to the baseline attire of long sleeves, long pants, shoes, and socks. A respirator may also be added if there is a concern for inhalation exposure. If MOEs at that level of PPE are less than 100, increasing levels of PPE are applied ( i. e., coveralls are added to provide a double layer of protective clothing or respirators). If MOEs are still less than 100 with maximum PPE, then engineering controls are applied ( i. e., enclosed cabs or cockpits and closed mixing/ loading systems). Note that the lower levels of PPE protect against dermal exposure, and dermal exposure is not anticipated for sodium chlorate. The types of protection, including PPE and engineering controls, which were used to calculate inhalation occupational exposure from sodium chlorate are as follows: 23 ° Baseline: No respirator ° PPE: Dust/ mist respirator with an 80% reduction factor ° Engineering Controls: Enclosed cockpits or enclosed cabs Anticipated use patterns and current labeling for sodium chlorate indicate several major occupational exposure scenarios that can result in handlers receiving inhalation exposures to sodium chlorate, including the antimicrobial use of sodium chlorate to generate chlorine dioxide for drinking water treatment. These exposure scenarios are based on the chemical formulations, equipment, and techniques that handlers can use to make sodium chlorate applications. Exposures are also considered based on their duration. The Agency assessed short ( 1 to 30 days) and intermediate term ( 30 days to several months) exposures to sodium chlorate, though the results were essentially the same because the toxicological endpoints for short and intermediate term exposures are the same in the case of sodium chlorate. For short and intermediate term exposures, MOEs greater than 100 are not of concern to the Agency.

Risks to handlers treating water systems are below the Agency's level of concern, with inhalation MOEs of 800 to 95,000 depending on the size of the generator. All sodium chlorate applications to chlorine dioxide generators occur in closed delivery systems. In addition, risk for most occupational handler scenarios do not exceed the Agency's level of concern of 100 ( i. e, most scenarios had MOEs > 100) at the baseline level of protection. However, risks for the following occupational scenarios did exceed the Agency's level of concern at baseline level of protection:

° Mixing/ Loading liquids for groundboom application to industrial/ non crop sites at 1032 lb ai per acre ( MOE = 42) and 523 lb ai per acre ( MOE = 84); ° Loading granules for tractor drawn spreader applications to industrial/ non crop sites at 523 lb ai per acre ( MOE = 59); ° Applying sprays to industrial/ non crop sites using groundboom equipment ( open cab) at 1032 lb ai per acre ( MOE = 69); at 523 lb ai per acre ( MOE = 140); ° Mixing/ Loading/ Applying liquids for low pressure handwand applications to industrial/ non crop sites at 1032 lb ai per acre ( MOE = 34) and 523 lb ai per acre ( MOE = 67); and ° Loading/ Applying granules to industrial/ non crop sites using a belly grinder at 523 lb ai per acre ( MOE = 65);

Inhalation handler risk for these scenarios did not exceed the Agency's level of concern with the addition of a dust/ mist respirator ( with an 80% reduction factor). Additionally, risks for certain scenarios were below the Agency's level of concern, without the application of PPE or engineering controls, once lower application rates were used. All risks of concern were at the high end of application rates (> 523 lb ai per acre), whereas at lower rates the risks were not of concern. Table 10 summarizes the risk results for short term and intermediate term occupational handlers. 24 Table 10. Sodium Chlorate: Short and Intermediate Term Occupational Inhalation Exposure Exposure Scenario Daily Area Treated1 Crop/ Target Application Rate ( lb ai/ A) Baseline Inhalation MOE2 PPE3 Engineering Controls Mixer/ Loaders Cotton, Corn, Rice, Dry Beans, Grain Sorghum, Flax, Safflower, Sunflower, Soybeans 7.5 190   1200 Fallow Land, Wheat 6 240

Chili Peppers ( for processing only), Potatoes 12.5 400

Ornamental Gourds, Cucurbits ( grown for seed) 6 830   Mixing/ Loading liquids for aerial application 350 Guar Beans, Southern Peas 7.5 670

Cotton, Corn, Rice, Dry Beans, Grain Sorghum, Flax, Safflower, Sunflower, Soybeans 7.5 1200   200 Fallow Land, Wheat 6 1500

Chili Peppers ( for processing only), Potatoes 12.5 1800

Ornamental Gourds, Cucurbits ( grown for seed) 6 3600   80 Guar Beans, Southern Peas 7.5 2900

1032 42 210

523 84 420  Mixing/ Loading liquids for groundboom application 40 Industrial/ Non Crop Sites 132 330

1032 340

523 670   Mixing/ Loading liquids for rightsof way sprayer application 5 Rights of Way & Industrial/ Non Crop Sites 132 2700

523 59 300

240 130   Loading granules for tractor drawn spreader application 40 Industrial/ Non Crop Sites 161 190

Applicators Aerial spray applications ( enclosed cockpit) 1200 Cotton, Corn, Rice, Dry Beans, Grain Sorghum, Flax, Safflower, Sunflower, Soybeans 7.50   3400 25 Table 10. Sodium Chlorate: Short and Intermediate Term Occupational Inhalation Exposure Exposure Scenario Daily Area Treated1 Crop/ Target Application Rate ( lb ai/ A) Baseline Inhalation MOE2 PPE3 Engineering Controls Fallow Land, Wheat 6   4300 Guar Beans, Southern Peas 7.5   12000 Chili Peppers ( for processing only), Potatoes 12.5   7100 350 Ornamental Gourds, Cucurbits ( grown for seed) 6   15000 Cotton, Corn, Rice, Dry Beans, Grain Sorghum, Flax, Safflower, Sunflower, Soybeans 7.5 1900   1200 Fallow Land, Wheat 6 2400

Guar Beans, Southern Peas 7.5 4700

Chili Peppers ( for processing only), Potatoes 12.5 2800   350 Ornamental Gourds, Cucurbits ( grown for seed) 6 5900

1032 69 340 1200 ( closed cab)

523 140  2300 ( closed cab) Groundboom spray applications 40 Industrial/ Non Crop Sites 132 540  9200 ( closed cab)

1032 110

523 210   Rights of way sprayer applications 5 Rights of Way & Industrial/ Non Crop Sites 132 820

523 84 420 460 ( closed cab)

240 180  990 ( closed cab) Tractor drawn spreader applications 40 Industrial/ Non Crop Sites 161 270  1500 ( closed cab)

Flaggers Flagging for aerial spray applications 350 Various Agricultural Crops 12.5 1400

Mixer/ Loader/ Applicators & Loader/ Applicators 1032 34 170

523 67 330  M/ L/ A liquids with a low pressure handwand sprayer 2 Industrial/ Non Crop Sites 132 270   26 Table 10. Sodium Chlorate: Short and Intermediate Term Occupational Inhalation Exposure Exposure Scenario Daily Area Treated1 Crop/ Target Application Rate ( lb ai/ A) Baseline Inhalation MOE2 PPE3 Engineering Controls 1032 230

523 450   M/ L/ A liquids with a handgun sprayer 5 Industrial/ Non Crop Sites 132 1800

523 65 320

240 140   L/ A granules with a belly grinder 1 Industrial/ Non Crop Sites 161 210

523 110

240 240   L/ A granules with a push type spreader 5 Industrial/ Non Crop Sites 161 360

1. Amount treated is presented in acres/ day. 2. Inhalation MOE = Oral NOAEL ( 30 mg/ kg/ day) / Daily Inhalation Dose. LOC for MOE is 100. 3. PPE dust/ mist respirator with an 80% reduction factor.

a. Incident Reports Available sources of incident data in humans were reviewed for the active ingredients sodium chlorate and calcium chlorate ( not currently registered). No data were found in any of the available databases on calcium chlorate, so this review exclusively addresses sodium chlorate. Data were available from the following sources: OPP Incident Data System ( IDS) consisting of reports submitted to EPA by registrants, other federal and state health and environmental agencies, and the public, since 1992; Poison Control Centers ( 1993 2001); California Department of Pesticide Regulation for pesticide poisoning since 1982; National Pesticide Telecommunications Network ( NPTN) for ranking of the top 200 active ingredients for which phone calls were received during calendar years 1984 1991; and National Institute of Occupational Safety and Health's Sentinel Event Notification System for Occupational Risks ( NIOSH SENSOR) from 1998 2002.

A total of 21 cases were recorded by the Poison Control Center from 1993 through 2001. Seven reported minor symptoms, and two reported moderate medical outcomes, primarily due to dermal effects such as swelling and rash. It is difficult to draw any conclusions from these reports because of the small number of cases.

Detailed descriptions of 36 cases submitted to the California Pesticide Illness Surveillance Program ( 1982 2002) were reviewed. However, sodium chlorate was determined to be the primary cause of illness in just four of these cases, and all four occurred in an agricultural setting ( three in cotton fields and one unknown). Two of these cases were classified as systemic and one each involved skin or eye effects. The two systemic cases involved applicators; one with nausea and the other with nausea, headache, and itching skin after spraying for one week. 27 Both of these cases were classified as " possibly" due to sodium chlorate. The skin case involved a worker exposed to drift from an adjacent field and the eye case occurred when a worker bumped into a spray nozzle while getting off the tractor and was splashed in the face. The skin case was classified as " probably," and the eye case as " definitely," due to sodium chlorate.

A number of suicidal ingestions of sodium chlorate have been reported in the literature, and many of these have led to death. The chance of ingesting a fatal dose accidentally is small unless the compound is mistaken for a drug and taken purposely. However, a near fatal poisoning occurred when a 13 year old boy " tasted" crystals of this weed killer which he found in his father's shed. In spite of intensive treatment, recovery did not begin until about the 15th day and required a little over 40 days.

Dermal absorption associated with agricultural use of sodium chlorate is not sufficient to cause systemic poisoning. Even by mouth, a large dose is required to produce illness. A 6.35% solution of potassium chlorate was long used as a gargle, or a 300 mg tablet was allowed to dissolve slowly in the mouth to treat pharyngitis before modern antibiotics became available. The toxicities of the sodium and potassium salts are similar. It was considered that a dose of 10,000 mg was fatal. The smallest recorded fatal dose was 7500 mg. However, vigorous treatment saved one person who had ingested about 40,000 mg.

B. Environmental Fate and Effects Risk Assessment A summary of the Agency's environmental fate and effects risk assessment is presented below. For detailed discussion of all aspects of the environmental risk assessment, please see the Revised Environmental Fate and Ecological Risk Assessment of Sodium Chlorate, dated June 1, 2006; it is available on the internet and in the public docket. This risk assessment was refined and updated to incorporate public comments and data received during the phase 3 public comment period.

1. Environmental Fate and Transport Sodium chlorate, an inorganic salt, is not a naturally occurring chemical. It is made by electrolysis of brine under controlled temperature and pH conditions to optimize the efficiency of the process and yield. Since targeted, guideline studies designed to understand the environmental fate of chlorate are not available, open, peer reviewed chemical literature and descriptive chemistry of the chlorine system were used as the basis for understanding the redox behavior of chlorate ( at least on a qualitative basis) and for generating a screening level environmental fate assessment.

Physical and chemical properties of a chemical can be used to identify potential routes of exposure. For example, the vapor pressure and Henry's Law Constant provide an indication of the potential to volatilize from soil and water ( partitioning into air), and the n octanol/ water partition coefficient provides an indication of the potential to bioaccumulate in fish or other aquatic organisms. Based on the very low vapor pressure and very high solubility of sodium chlorate in water, sodium chlorate is not expected to volatilize from soil or water. In addition, the low log n octanol/ water partition coefficient indicates that sodium chlorate has low potential 28 to bioaccumulate.

As stated above, sodium chlorate is highly soluble. In addition, sodium chlorate is completely ionized in water, thus producing sodium ( Na+) and the chlorate ( ClO 3 ) anion. Anions do not bind readily to soil or sediment particulates1 and, therefore, are expected to be very mobile. Assuming that chlorate does not undergo any redox reactions, it is 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 redox chemistry2 of chlorate affects its behavior in soils and natural water. Therefore, identification of the conditions under which chlorate and other oxyanions of chlorine may predominate is an important consideration in the environmental fate and risk assessment of chlorate. The oxidation reduction reactions of chlorate with organic matter and other inorganic chemical species are very complex and depend on the redox conditions of the media, nature and concentration of reductants, chlorate concentration, temperature, pH, and degree of moisture ( soils). For example, chlorate is generally more stable under alkaline than acidic conditions; however, when a chemical element ( chlorine) can exist in two or more oxidation states ( i. e., chlorite and chlorate), the redox potential of the media also effects the predominance of the reduction products. Nitrate concentrations in soil and water ( as well as other physical and chemical properties of soil and water) play an important role in the redox chemistry of chlorate in the environment.

2. Ecological Exposure and Risk To estimate potential ecological risk, EPA integrates the results of exposure and ecotoxicity studies using the risk quotient method. Risk quotients ( RQs) are calculated by dividing acute and chronic estimated environmental concentrations ( EECs) by ecotoxicity values for various wildlife and plant species. RQs are then compared to levels of concern ( LOCs), and when the RQ exceeds the level of concern for a particular category, the Agency presumes a risk of concern to that category. See Table 11 below for the Agency's ecological LOCs. Risk characterization provides further information on potential adverse effects and the possible impact of those effects by considering the fate of the chemical and its degradates in the environment, organisms potentially at risk, and the nature of the effects observed.

1 Unless they chemisorb to soil or sediment particulates. Chemisorption of chlorate is unlikely.

2 The term " redox chemistry" is used as an overall term for oxidation and reduction reactions. Other terms that are frequently used for oxidizers are " oxidants," " oxidizing agents." Reductants are frequently referred to as " reducing agents." All redox reactions require an oxidant and a reductant. Reductants are electron donors, while oxidants are electron acceptors. 29 Table 11. EPA's Ecological Levels of Concern ( LOCs) and Risk Presumptions If a calculated RQ is greater than the LOC presented, then the Agency presumes that  LOC terrestrial animals LOC aquatic animals LOC plants Acute Risk   there is potential for acute risk; regulatory action may be warranted in addition to restricted use classification 0.5 0.5 1.0 Acute Endangered Species   endangered species may be adversely affected 0.1 0.05 1.0 Chronic Risk   there is potential for chronic risk 1 1 NA a. Terrestrial Organisms 1. Birds and Mammals a. Exposure Sodium chlorate may be applied as a spray ( agricultural and nonagricultural uses) or as granules ( nonagricultural uses only). The Agency's methods for assessing exposure to terrestrial organisms are different for each of these application methods and are discussed below.

For spray applications, the Agency's terrestrial exposure model ( ELL FATE) was used to estimate exposures and risks to avian and mammalian species. Input values on avian and mammalian toxicity, as well as chemical application and foliar dissipation half life data, are required to run the model. The model provides estimates of both exposure concentrations and RQs. Specifically, the model provides estimates of concentrations ( maximum and average) of chemical residues on the surface of different types of foliage that may be sources of exposure to avian, mammalian, reptilian, or terrestrial phase amphibian receptors. The surface residue concentration ( ppm) is estimated by multiplying the application rate ( pounds active ingredient per acre) by a value specific to each food item. In all screening level assessments, the organisms are assumed to consume 100% of their diet as one food type. These exposure estimates are only applicable to the applied pesticide, sodium chlorate. It is uncertain to what extent exposure to reduced species of chlorate, such as chlorite, may occur.

ELL FATE was run for sodium chlorate for use on agricultural crops using the inputs provided in Table 12 below. In the absence of foliar dissipation half life data for sodium chlorate, the Agency's default half life value of 35 days was used for all scenarios.

Table 12. Input Parameters for Sodium Chlorate Used in ELL FATE Crop Maximum labeled application rate No. of applications Application interval Chili peppers; white/ Irish potatoes 12.5 lbs ai/ A 1 N/ A Cotton 7.5 lbs ai/ A 2 30 days Corn; flax, guar; southern peas; rice; safflower; sorghum; soybeans; sunflower 7.5 lbs ai/ A 1 N/ A 30 Table 12. Input Parameters for Sodium Chlorate Used in ELL FATE Crop Maximum labeled application rate No. of applications Application interval Agricultural fallow land; dried beans; corn; cucurbits, flax, gourds; guar; southern peas; white/ Irish potatoes; rice; safflower; sorghum; soybeans; sunflower 6 lbs ai/ A 1 N/ A The predicted upper 90th percentile and mean chlorate EECs ( agricultural and nonagricultural uses) on various wild animal food items are presented in Table 13 below.

Table 13. EECs ( mg ai/ kg food item) for Terrestrial Animal Risk Assessment for Sodium Chlorate Crops Predicted 90th Percentile Residue Levels Predicted Mean Residue Levels short grass tall grass broadleaf forage, small insects fruit, pods, seeds, small insects short grass tall grass broadleaf forage, small insects fruit, pods, seeds, small insects Agricultural Uses ( Spray Applications)

Chili peppers; white/ Irish potatoes 3000 1400 1700 190 1100 450 560 88 Cotton 2800 1300 1600 170 990 420 520 81 Corn; flax, guar; southern peas; rice; safflower; sorghum; soybeans; sunflower 1800 830 1000 110 640 270 340 53 Agricultural fallow land; dried beans; corn; cucurbits, flax, gourds; guar; southern peas; white/ Irish potatoes; rice; safflower; sorghum; soybeans; sunflower 1400 660 810 90 510 220 270 42 Non Agricultural Uses ( Spray Applications)

Industrial sites such as driveways, paths, brick walks, cobble gutters, tennis courts 12500 5700 7000 780 4400 1900 2300 360 31 Table 13. EECs ( mg ai/ kg food item) for Terrestrial Animal Risk Assessment for Sodium Chlorate Crops Predicted 90th Percentile Residue Levels Predicted Mean Residue Levels short grass tall grass broadleaf forage, small insects fruit, pods, seeds, small insects short grass tall grass broadleaf forage, small insects fruit, pods, seeds, small insects Parking lots, fence lines, building perimeters, ditch banks, picnic areas, vacant lots, wood decks, bleachers, cemeteries, fuel tanks, runways, helo pads, etc. 125,000 57,000 70,000 7800 44,000 19,000 23,000 3600 For granular applications, estimation of chlorate loading per unit area ( mg/ ft2) is calculated. This approach, which is intended to represent exposure via multiple routes ( e. g., incidental ingestion of contaminated soil, dermal contact with treated seed surfaces and soil during activities in the treated areas, preening activities, and ingestion of drinking water contaminated with pesticide) and not just direct ingestion, considers observed effects in toxicity studies and relates them to the amount of pesticide applied to surface area. The maximum labeled application rate for the active ingredient is the basis for the exposure estimate. The terrestrial EECs for sodium chlorate's non agricultural use granular applications are presented in Table 14 below.

Table 14. Range of Terrestrial EECs ( Granular Applications) for Sodium Chlorate Non Agricultural Uses Use Application Rate ( lbs ai/ A) EEC ( mg/ ft2) a Parking lots, under asphalt paving, fence lines, building perimeters, ditch banks, picnic areas, vacant lots, wood decks, bleachers, cemeteries, fuel tanks, runways, helo pads, etc. 520 5400 Around buildings, storage areas, fences, pumps, machinery, fuel tanks, recreational areas, roadways, guard rails, airports, rights of ways. 160 1700 a. EEC = Application rate ( lbs/ Acre) x 453,000 mg/ lb ÷ 43,600 sq ft/ Acre b. Toxicity Effects characterization describes the potential effects a pesticide can produce in a terrestrial organism, and is based on registrant submitted studies that describe acute and chronic toxicity effects for various terrestrial animals. Table 15 summarizes the toxicity effects and reference values used to assess risks for sodium chlorate to mammals and birds. 32 Table 15. Toxicity Reference Values for Mammals and Birds for Sodium Chlorate.

Exposure Scenario Species Toxicity Value Used in Risk Assessment Effect Mammals Acute Rat LD50 = > 5000 mg/ kg bw At 5000 mg/ kg bw, 1/ 10 animals died.

Chronic Rat NOAEC = 500 mg/ kg bw, highest dose tested ( approx. 10,000 ppm) No reproductive effects Birds Acute Mallard duck LD50 > 2510 mg/ kg bw No mortality and no clinical signs of toxicity were observed.

Chronic Bobwhite quail NOAEC = 271 ppm The LOAEC was 964 ppm based on effects on egg production and thickness, embryonic survival, and hatchling body weight.

c. Avian Risk Estimates Acute RQs for birds were not calculated, because no mortality or signs of toxicity were observed in the submitted subacute or acute toxicity studies at concentrations that are above the limit for these types of studies.

Avian chronic RQs for agricultural crops, at the estimated upper 90th percentile residue levels, are presented in Table 16 below. RQ values for all crops and all avian food items assessed, except the fruits, pods, seeds, and small insects category, marginally exceeded the Agency's chronic LOC of 1.0. The highest chronic avian RQ was 11 ( chili pepper/ potato and short grass scenario). Chronic RQs based on mean EECs, although not presented here, would be approximately three times lower for most food items than those based on the 90th percentile residue levels shown below.

Table 16. Avian Chronic Risk Quotients for Sodium Chlorate Agricultural Uses Crops Short grass Tall grass Broadleaf forage, small insects Fruit, pods, seeds, small insects Chili peppers; white/ Irish potatoes 11.0 5.2 6.3 0.7 Cotton 10.0 4.8 5.9 0.63 Corn; flax, guar; southern peas; rice; safflower; sorghum; soybeans; sunflower 6.6 3.1 3.7 0.41 Agricultural fallow land; dried beans; corn; cucurbits, flax, gourds; guar; southern peas; white/ Irish potatoes; rice; safflower; sorghum; soybeans; sunflower 5.2 2.4 3.0 0.33 Chronic RQs for birds are not presented for chlorate's non agricultural uses ( granular or 33 spray). However, RQs would be considerably higher for birds foraging where chlorate is applied at the rates assessed for the non agricultural uses. EECs ranged from 12,500 to 125,000 ( short grass food item), which would result in chronic avian RQs of 46 to 460. The size of the treated areas for these uses is uncertain, and this will be discussed further in Section IV of this document; therefore, the likelihood that a bird would consume 100% of its diet from a nonagricultural area treated with sodium chlorate is uncertain.

d. Mammalian Risk Estimates Acute RQs were not calculated for mammals. The LD50 from a core acute oral toxicity study in rats was > 5000 mg/ kg bw. In this study, 10% ( 1/ 10) of the rats administered 5000 mg/ kg died. Mortality was not observed at any other dose. Therefore, the data were not sufficient to allow for characterization of the dose response relationship and the proximity of the LD50 to 5000 mg/ kg bw is uncertain. For this reason, acute RQs were not calculated. However, Tables 17 and 18 below present a comparison of the body weight adjusted LD50s to the agricultural and non agricultural EECs, respectively, based on current use rates and the spray application method. These ratios can be used to estimate high end acute risk to exposed mammals. Actual RQs would be lower than the values in Tables 17 and 18.

Table 17. Proximity of the lowest observed acute toxic dose in mammals to the upper 90th percentile EEC ( mg/ kg bw) for the range of maximum application rates for all agricultural uses Food item Size of mammal ( grams) Adjusted lowest observed toxic dose ( mg/ kg bw) Range of EECs ( mg/ kg bw) a Ratio of lowest observed toxic dose to the upper 90th percentile EEC ( unitless)

15 10,989 1400  2900 0.13  0.26 35 8891 950  2000 0.11  0.22 Short grass 1000 3846 200  450 0.052  0.12 15 10,989 630  1300 0.057  0.12 35 8891 440  910 0.049  0.10 Tall grass 1000 3846 99  210 0.026  0.055 15 10,989 770  1600 0.070  0.15 35 8891 540  1100 0.061  0.12 Broadleaf plants/ small insects 1000 3846 120  250 0.031  0.065 15 10989 86  180 < 0.01  0.016 35 8891 59  120 < 0.01  0.013 Fruits, pods, large insects 1000 3846 14  28 < 0.01  < 0.01 a. EECs were calculated by assuming that small, medium, and large mammals consume 95%, 66%, and 15% of their body weight daily. Only the highest and lowest EECs from chlorate's agricultural uses are used in this assessment.

For sodium chlorate's agricultural uses, all of the acute ratios are below the Agency's acute and endangered species LOC of 1.0 and 0.1, respectively, with the exception of small 34 mammals eating short grass. The highest exceedence is for 15 gram mammals eating short grass ( ratio = 0.26).

Based on current non agricultural use application rates, the only group that does not exceed the Agency's acute mammalian LOC of 1.0 is animals eating fruits, pods, or large insects ( ratios range from 0.3 to 0.7). The Agency's acute mammalian endangered species LOC of 0.1 is potentially exceeded for all size animals and food items. While the ratios presented in Table 18 suggest that there could be risk to mammals of all sizes that forage in the area where chlorate is used for the non agricultural spray applications, the risk was likely over estimated, since an LD50 has not been established. The highest dose tested in the available toxicity studies ( 5000 mg/ kg bw) induced 10% mortality. The proximity of the LD50 to 5000 mg/ kg bw is uncertain. Furthermore, many of the non agricultural uses will likely result in small contiguously treated areas; therefore, the likelihood that an animal will consume 100% of its diet from the areas treated with sodium chlorate is low for some of these uses. Nonetheless, the EECs were predicted to be up to 11 times higher than 5000 mg/ kg bw for the non agricultural uses. Therefore, there may be some acute risk to mammals at levels of concern to the Agency for nonagricultural uses.

Table 18. Proximity of the lowest observed acute toxic dose in mammals to the predicted EEC ( mg/ kg bw) for the range of maximum application rates for all non agricultural uses ( spray applications)

Food item Size of mammal ( grams) Adjusted lowest observed toxic dose ( mg/ kg bw) Range of EECs ( mg/ kg bw) a Ratio of lowest observed toxic dose to the upper 90th percentile EEC ( unitless)

15 10989 11,900  119,000 1.1  11 35 8891 8200  82,000 0.93  9.3 Short grass 1000 3846 1900  19,000 0.49  4.9 15 10989 5400  54,000 0.49  4.9 35 8891 3800  38,000 0.43  4.3 Tall grass 1000 3846 860  8600 0.22  2.2 15 10989 6700  67,000 0.61  6.1 35 8891 4600  46,000 0.52  5.2 Broadleaf plants/ small insects 1000 3846 1100  11,000 0.27  2.7 15 10989 740  7400 0.07  0.7 35 8891 520  5200 0.06  0.6 Fruits, pods, large insects 1000 3846 120  1200 0.03  0.3 a. EECs were calculated by assuming that small, medium, and large mammals consume 95%, 66%, and 15%, respectively, of their body weight daily, and were calculated using the lowest and highest labeled application rates ( 52 lbs ai/ A and 520 lbs ai/ A) that are most likely to result in exposure RQs were not calculated for acute risk for non agricultural granular applications for reasons previously discussed. However, Table 19 below presents a comparison of the body weight adjusted lowest observed toxic dose in rats ( 5000 mg/ kg day) to the granular application 35 EECs ( mg/ ft2). These ratios indicate a potential acute risk to mammals of all size classes, as the lowest ratio ( 0.43 for large mammals and the building and storage area perimeter scenario) exceeds the acute endangered species LOC of 0.1.

Table 19. Range of ratios of chlorate's body weight adjusted LD50 to granular EECs ( mg/ ft2) for sodium chlorate's non agricultural uses ( granular formulations)

Use Body Weight ( g) Rat LD50 mg/ kg bw EEC ( mg/ ft2) a Ratio of LD50 to EEC 15 10,989 5400 33 35 8891 5400 17 Parking lots, under asphalt paving, fence lines, building perimeters, ditch banks, picnic areas, vacant lots, wood decks, bleachers, cemeteries, fuel tanks, runways, helo pads, etc.

1000 3846 5400 1.4 15 10,989 1700 10 35 8891 1700 5.4 Around buildings, storage areas, fences, pumps, machinery, fuel tanks, recreational areas, roadways, guard rails, airports, rights of ways. 1000 3846 1700 0.43 a. EEC = Application rate ( lbs/ Acre) x 453,000 mg/ lb ÷ 43,600 sq ft/ Acre For mammals, the Agency typically evaluates the mammalian reproductive effects for exposures greater than 30 days. Interpretation of the RQs resulting from the NOAEL of 500 mg/ kg day observed in a 2 generation rat study is difficult in this respect. Although the study did indicate some chronic effects, reproduction effects were not observed at any dose level tested. Because 500 mg/ kg was the highest dose tested, it is uncertain whether there is a NOAEL for reproductive effects. In addition, if there is an actual NOAEL for reproductive effects, it could be much greater than 500 mg/ kg.

However, the Agency calculated RQs based on the 500 mg/ kg day NOAEL as a conservative estimate of risk, as presented in Table 20. Based on this conservative estimate, chronic mammalian LOC of 1.0 was only slightly exceeded for the smallest weight classes of mammals for most food items and the largest weight class of mammals feeding on short grass. Based on the lack of observed reproductive effects in the chronic study and the slight RQs exceedances for agricultural uses, the Agency does not anticipate a chronic risk of concern to mammals from agricultural uses of sodium chlorate.

Table 20. Mammalian Chronic Risk Quotients for Sodium Chlorate's Agricultural Uses ( Spay Application)

Use Food Item 15 gram mammal 35 gram mammal 1000 gram mammal Single application of 12.5 lbs ai/ A Chili peppers; white/ Irish potatoes Short Grass 2.6 2.2 1.2 36 Table 20. Mammalian Chronic Risk Quotients for Sodium Chlorate's Agricultural Uses ( Spay Application)

Use Food Item 15 gram mammal 35 gram mammal 1000 gram mammal Single application of 12.5 lbs ai/ A Tall Grass 1.2 1.0 0.55 Broadleaf plants/ small insects 1.5 1.3 0.67 Chili peppers; white/ Irish potatoes Fruits/ pods/ large insects 0.16 0.14 0.07 Multiple applications ( 7.5 lbs ai/ A, 2 applications, 30 day interval)

Short Grass 2.4 2.1 1.1 Tall Grass 1.1 0.95 0.51 Broadleaf plants/ small insects 1.4 1.2 0.62 Cotton Fruits/ pods/ large insects 0.15 0.13 0.07 Single application ( 7.5 lbs ai/ A) a Short Grass 1.6 1.3 0.72 Tall Grass 0.72 0.61 0.33 Broadleaf plants/ small insects 0.88 0.75 0.40 Corn; flax, guar; southern peas; rice; safflower; sorghum; soybeans; sunflower Agricultural fallow land; dried beans; corn; cucurbitsa, flax, gourds; guar; southern peas; white/ Irish potatoes; rice; safflower; sorghum; soybeans; sunflower Fruits/ pods/ large insects 0.10 0.08 0.04 a. EECs and RQs are similar for the 7.5lbs a. i/ A ( corn, et al.) and 6.0 lbs a. i./ A ( agricultural fallow land, et al.) and single applications, and LOC exceedances are equivalent; therefore, only results from the single application of 7.5 lbs ai/ A are presented.

Reproduction RQs were not calculated for chlorate's non agricultural uses ( spray or granular applications). However, based on the high application rates and resulting high potential EECs, risks from chlorate's non agricultural uses could be considerably higher than risks presented for agricultural uses.

2. Non Target Insects EPA currently does not estimate RQs for terrestrial non target insects. Furthermore, the Agency has no insect toxicity data for sodium chlorate. 37 3. Non Target Terrestrial Plants Based on chlorate's non selective mode of action and lack of adequate toxicity data, the Agency presumes risk to non target terrestrial plants at levels above the Agency's level of concern for all uses. The risks to plants cannot be quantified at this time due to lack of data; however, the Agency will require data to address this uncertainty.

b. Aquatic Organisms At the present time, there is no methodology to estimate exposure concentrations in water for non metal inorganic chemical species that can be found in different oxidation states ( e. g., for inorganic chemical species that can exhibit extensive pH pE dependent redox chemistry, such as the chlorine system). As an approximation on the impact of chlorate on surface water quality, the Tier I GENEEC 2 simulation model was used to estimate exposure concentrations in aquatic systems. Extreme assumptions in the environmental persistence of chlorate were made that resulted in high end exposure concentrations in the standard ecological pond scenario. The predicted chlorate concentrations are believed to be high because the chemical speciation of chlorate was not considered in the assessment. As previously discussed, under thermodynamic equilibrium conditions, chloride is likely the predominant species in natural environments. This analysis, however, indicates that chlorate can be reduced to chloride, but not how fast the reduction will occur. Since there are no input parameters for the model that take into account the redox behavior of chlorate, it was assumed that unchanged chlorate runs off into surface water, where it remains as chlorate.

Unlike the drinking water assessment described in the human health risk assessment section of this document, the exposure values used in the ecological risk assessment do not include the Index Reservoir ( IR) and Percent Cropped Area ( PCA) factor refinements. These factors represent a drinking water reservoir, not the variety of aquatic habitats relevant to a risk assessment for aquatic animals, such as ponds adjacent to treated fields. Therefore, the EEC values used to assess exposure and risk to aquatic animals are not the same as those used to assess exposure and risk to humans from pesticides in drinking water.

1. Fish Acute toxicity studies for both freshwater and marine/ estuarine fish were consistent with a " practically non toxic" designation for fish. No effects were observed in sheepshead minnows ( estuarine/ marine) or bluegill ( freshwater) fish at up to 1000 mg/ L. For inorganic chlorates, RQs were not calculated for freshwater or estuarine/ marine fish, since the proximity of the LC50 to the highest concentration tested ( 1000 mg/ L) could not be estimated. Although 1000 mg/ L is not an LC50, which is the toxicity value usually used to derive RQs, this value was used only to estimate high end risk to exposed fish. EECs for both agricultural and nonagricultural uses of sodium chlorate were more than 20 fold lower than the toxic concentration observed in fish of 1000 mg/ L ( all RQs would be less than 0.05, and below the Agency's acute LOC of 0.5 and the acute endangered species LOC of 0.05). Therefore, acute risk to freshwater and estuarine/ marine fish is not of concern to the Agency.

No chronic toxicity studies in fish have been submitted to the Agency, nor were any 38 identified in the ECOTOX database. However, the Agency will require data to address this area of uncertainty.

2. Aquatic Invertebrates For freshwater invertebrates, acute RQs are based on the EC50 of 920 mg/ L ( daphnids) and EECs calculated by GENEEC 2; these are presented in Table 21 below. All RQs are below the acute LOC of 0.5 and the endangered species acute LOC of 0.05; therefore, acute risk to freshwater invertebrates is not of concern to the Agency.

Table 21. Acute Freshwater Aquatic Invertebrate Risk Quotients Use Application Rate Range Maximum EEC EC50 RQ Agricultural uses 4.5  7.5 lb ai/ A 0.91 mg/ L 920 mg/ L < 0.01 Non agricultural uses 132  520 lb ai/ A 39 mg/ L 920 mg/ L < 0.042 For saltwater invertebrates, acute RQs were not calculated, because the proximity of the LC50 from a supplemental 96 hr study ( mysid shrimp) to the highest concentration tested ( 1000 mg/ L), could not be estimated. However, the ratios of chlorate's EECs ( agricultural and nonagricultural uses) to the concentration of 1000 mg/ L were calculated, and the highest resulting value was 0.04. As this is well below the acute LOC of 0.5, in addition to the endangered species acute LOC of 0.05, acute risk to saltwater invertebrates is not of concern to the Agency.

Chronic risk to invertebrates was not assessed, since treatment related effects were not observed at any concentration in available studies.

3. Aquatic Plants Toxicity ( EC50) and exposure ( EEC) values, as well as RQs, for non endangered aquatic plants are shown in Tables 22. For non endangered aquatic plants, the Agency calculates RQs by dividing EECs by EC50 values.. For sodium chlorate, the LOC ( 1.0) was not exceeded for either the agricultural or nonagricultural uses of chlorate; therefore, risk to non endangered aquatic plants is not of concern to the Agency.

Table 22. Risk Quotients for Non endangered Aquatic Plants Use Maximum Peak EEC Algal EC50 Duckweed EC50 Algal RQ Duckweed RQ Agricultural Up to 0.9 mg/ L 133 mg/ L 43 mg/ L < 0.01 0.02 Non agricultural Up to 39 mg/ L 133 mg/ L 43 mg/ L Up to 0.29 0.91 The RQs for endangered aquatic plants are presented in Table 23. The Agency calculates 39 RQs for endangered aquatic plants by dividing EECs by NOAECs. For endangered aquatic plants, the Agency's LOC ( 1.0) was exceeded for sodium chlorate's non agricultural uses ( RQ = 12.6). However, the EECs for the non agricultural use sites are likely conservative; therefore, additional information on use patterns would allow for characterization of potential risks to aquatic plants. Also, testing on three additional required plant species is required for herbicides. Overall, additional data are needed to allow for a full characterization of potential risk to aquatic plants.

Table 23. Endangered Species Algal Risk Quotients Agricultural and Non Agricultural Uses Use Maximum Peak EEC Algal EC50 Duckweed EC50 Algal RQ Duckweed RQ Agricultural Up to 0.9 mg/ L 62.5 mg/ L 3.1 mg/ L Up to 0.014 Up to 0.29 Non Agricultural Up to 39 mg/ L 62.5 mg/ L 3.1 mg/ L Up to 0.62 Up to 12.6 c. Endangered Species The Agency's screening level assessment results in the determination that sodium chlorate will have no acute risks to birds, no acute risks to fish ( freshwater and estuarine/ marine), and no acute or chronic risks to aquatic invertebrates ( freshwater and estuarine/ marine).

However, the preliminary risk assessment for endangered species indicates that RQs exceed endangered species LOCs for chronic risks to birds ( RQs up to 11 for agricultural uses and greater for non agricultural uses); acute risks to mammals ( RQs up to 33); chronic risks to mammals ( RQs up to 1.2 for agricultural uses and greater for non agricultural uses); and risks to aquatic plants ( RQs up to 13). Risks could not be calculated for terrestrial plants and for chronic risks to fish; however, the Agency will be requiring data.

Further, potential indirect effects to any species dependent upon a species that experiences effects from use of sodium chlorate can not be precluded based on the screening level ecological risk assessment. These findings are based solely on EPA's screening level assessment and do not constitute " may affect" findings under the Endangered Species Act.

d. Ecological Incidents A review of the Ecological Incident Information System ( EIIS) database for ecological incidents involving chlorate was completed on October 25, 2004. There were no chlorate incidents in the database 40 IV. Risk Management, Reregistration, and Tolerance Reassessment A. Determination of Reregistration Eligibility Section 4( g)( 2)( A) of FIFRA calls for the Agency to determine, after submission of relevant data concerning an active ingredient, whether or not products containing the active ingredient are eligible for reregistration. The Agency has previously identified and required the submission of the generic ( i. e., active ingredient specific) data required to support reregistration of products containing sodium chlorate as an active ingredient. The Agency has completed its review of these generic data, and has determined that the data are sufficient to support reregistration of all products containing sodium chlorate.

The Agency has completed its assessment of the dietary, occupational, residential, and ecological risk associated with the use of pesticide products containing the active ingredient sodium chlorate. Based on a review of these data and on public comments on the Agency's assessments for the active ingredient sodium chlorate, the Agency has sufficient information on the human health and ecological effects to make decisions as part of the tolerance reassessment process under FFDCA and reregistration process under FIFRA, as amended by FQPA. The Agency has determined that sodium chlorate containing products are eligible for reregistration provided that: ( i) the risk mitigation measures outlined in this document are adopted, ( ii) label amendments are made to reflect these measures, and ( iii) a safety finding can be made for sodium chlorite. Label changes are described in Section V. Appendix A summarizes the uses of sodium chlorate that are eligible for reregistration. Appendix B identifies the generic data requirements that the Agency reviewed as part of its determination of reregistration eligibility of sodium chlorate, and lists the submitted studies that the Agency found acceptable. Data gaps are identified as generic data requirements that have not been satisfied with acceptable data.

Based on its evaluation of sodium chlorate, the Agency has determined that sodium chlorate products, unless labeled and used as specified in this document, would present risks inconsistent with FIFRA. Accordingly, should a registrant fail to implement any of the risk mitigation measures identified in this document, the Agency may take regulatory action to address the risk concerns from the use of sodium chlorate. If all changes outlined in this document are incorporated into the product labels, then all current risks for sodium chlorate will be adequately mitigated for the purposes of this determination under FIFRA. Once an Endangered Species assessment is completed, further changes to these registrations may be necessary as explained in Section III. B. 2. c. of this document.

B. Public Comments and Responses Through the Agency's public participation process, EPA worked with stakeholders and the public to reach the regulatory decisions for sodium chlorate. EPA released its sodium chlorate preliminary risk assessments for public comment on February 1, 2006, for a 60 day public comment period ( Phase 3 of the public participation process). During the public comment period on the risk assessments, which closed on April 3, 2006, the Agency received comments from the sodium chlorate task force, technical registrants, and private citizens. These comments in their entirety, 41 responses to the comments, as well as the preliminary and revised risk assessments, are available in the public docket ( OPP 2005 0507) at http: www. regulations. gov.

C. Regulatory Position 1. Food Quality Protection Act Findings a. " Risk Cup" Determination As part of the FQPA tolerance reassessment process, EPA assessed the risks associated with this pesticide. The Agency has determined that, if the mitigation described in this document is adopted and labels are amended, and a safety finding can be made for sodium chlorite, human health risks as a result of exposures to sodium chlorate are within acceptable levels. In other words, EPA has concluded that the exemptions from tolerances for sodium chlorate meet FQPA safety standards. In reaching this determination, EPA has considered the available information on the special sensitivity of infants and children, as well as exposures to sodium chlorate from all possible sources.

b. Determination of Safety to U. S. Population The Agency has determined that provided a safety finding can be made for sodium chlorite, the Agency has determined that the established tolerance exemptions for sodium chlorate, with amendments and changes as specified in this document, meet the safety standards under the FQPA amendments to section 408( b)( 2)( D) of the FFDCA, and that there is a reasonable certainty no harm will result to the general population or any subgroup from the use of sodium chlorate. In reaching this conclusion, the Agency has considered all available information on the toxicity, use practices and exposure scenarios, and the environmental behavior of sodium chlorate. As discussed in Section III, the acute, chronic, and cancer dietary ( food and drinking water) risks from sodium chlorate are below the Agency's acute and chronic LOC, provided that mitigation measures outlined in this document are adopted and labels are amended.

c. Determination of Safety to Infants and Children EPA has determined that the established tolerance exemptions for sodium chlorate, with amendments and changes as specified in this document, and provided that a safety finding can be made for sodium chlorite, meet the safety standards under the FQPA amendments to section 408( b)( 2)( C) of the FFDCA, that there is a reasonable certainty of no harm for infants and children. The safety determination for infants and children considers factors on the toxicity, use practices and environmental behavior noted above for the general population, but also takes into account the possibility of increased dietary exposure due to the specific consumption patterns of infants and children, as well as the possibility of increased susceptibility to the toxic effects of sodium chlorate residues in this population subgroup.

In determining whether or not infants and children are particularly susceptible to toxic effects from exposure to residues of sodium chlorate, the Agency considered the completeness of 42 the hazard database for developmental and reproductive effects, the nature of the effects observed, and other information. On the basis of this information, the FQPA SF has been reduced to 1X for sodium chlorate. The rationale for the decisions on the FQPA SF can be found in Section III and the following document: HED Chapter of the Reregistration Eligibility Decision Document ( RED), dated January 26, 2006.

2. Endocrine Disruptor Effects EPA is required under the FFDCA, as amended by FQPA, to develop a screening program to determine whether certain substances ( including all pesticide active and other ingredients) " may have an effect in humans that is similar to an effect produced by a naturally occurring estrogen, or other endocrine effects as the Administrator may designate." Following recommendations of its Endocrine Disruptor Screening and Testing Advisory Committee ( EDSTAC), EPA determined that there was a scientific basis for including, as part of the program, the androgen and thyroid hormone systems, in addition to the estrogen hormone system. EPA also adopted EDSTAC's recommendation that EPA include evaluations of potential effects in wildlife. For pesticides, EPA will use FIFRA and, to the extent that effects in wildlife may help determine whether a substance may have an effect in humans, FFDCA authority to require the wildlife evaluations. As the science develops and resources allow, screening for additional hormone systems may be added to the Endocrine Disruptor Screening Program ( EDSP).

The available toxicity studies on sodium chlorate demonstrate the thyroid gland to be its target of toxicity. The endpoints selected to assess chronic dietary risk and short and intermediate term oral and inhalation risks in this document are protective of the observed thyroid effects seen in the available toxicity studies. When additional appropriate screening and/ or testing protocols being considered under the Agency's EDSP have been developed, sodium chlorate may be subjected to further screening and/ or testing to better characterize effects related to endocrine disruption.

3. Cumulative Risks The FFDCA, as amended by the FQPA, requires that the Agency consider " available information" concerning the cumulative effects of a particular pesticide's residues and " other substances that have a common mechanism of toxicity." The reason for consideration of other substances is due to the possibility that low level exposures to multiple chemical substances that cause a common toxic effect by a common toxic mechanism could lead to the same adverse health effect as would a higher level of exposure to any of the substances individually. The EPA has not made a common mechanism of toxicity finding as to sodium chlorate and any other substances. For the purposes of this reregistration eligibility decision ( RED), therefore, EPA has not assumed that the inorganic chlorates have a common mechanism of toxicity with other substances. For information regarding EPA's efforts to determine which chemicals have a common mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the policy statements released by EPA's Office of Pesticide Programs concerning common mechanism determinations and procedures for cumulating effects from substances found to have a common mechanism on EPA's website at http:// www. epa. gov/ pesticides/ cumulative/. 43 4. Endangered Species The Agency's screening level assessment results in the determination that sodium chlorate will have no acute risks to birds, no acute risks to fish ( freshwater and estuarine/ marine), and no acute or chronic risks to aquatic invertebrates ( freshwater and estuarine/ marine).

However, the preliminary risk assessment for endangered species indicates that RQs exceed endangered species LOCs for chronic risks to birds ( RQs up to 11 for agricultural uses and greater for non agricultural uses); acute risks to mammals ( RQs up to 33); chronic risks to mammals ( RQs up to 1.2 for agricultural uses and greater for non agricultural uses); and risks to aquatic plants ( RQs up to 13). Risks could not be calculated for terrestrial plants and for chronic risks to fish; however, the Agency will be requiring data.

Further, potential indirect effects to any species dependent upon a species that experiences effects from use of sodium chlorate cannot be precluded based on the screeninglevel ecological risk assessment. These findings are based solely on EPA's screening level assessment and do not constitute " may affect" findings under the Endangered Species Act.

The Agency has developed the Endangered Species Protection Program to identify pesticides whose use may cause adverse impacts on endangered and threatened species, and to implement mitigation measures that address these impacts. The Endangered Species Act ( ESA) requires federal agencies to ensure that their actions are not likely to jeopardize listed species or adversely modify designated critical habitat. To analyze the potential of registered pesticide uses that may affect any particular species, EPA uses basic toxicity and exposure data developed for the REDs and considers it in relation to individual species and their locations by evaluating important ecological parameters, pesticide use information, geographic relationship between specific pesticide uses and species locations, and biological requirements and behavioral aspects of the particular species, as part of a refined species specific analysis. When conducted, this species specific analysis will take into consideration any regulatory changes in this RED that are being implemented at that time.