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
-------
REREGISTRATION ELIGIBILITY
DECISION
for
Inorganic Chlorates
Case No. 4049
Approved by:
Debra Edwards, Ph.D.
Director, Special Review and
Reregistration Division
Date
-------
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
HI. 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 Disrupter 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
in
-------
2. Labeling for End-Use Products 61
C. Labeling Changes Summary Table 61
D. Existing Stocks 61
IV
-------
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
v
-------
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 Disrupter Screening Program
EDSTAC Endocrine Disrupter 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/1, 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
LOG 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.
VI
-------
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
POP 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
vn
-------
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.
Vlll
-------
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
-------
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/oppsrrdl/reregistration/inorganicchlorates/.
-------
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:
\
//
Cl 0- Ha1
Common Names:
Chemical Name:
Trade Names:
Chemical Family:
Case Number:
CAS Number:
PC Code:
Molecular Weight:
Empirical Formula:
Technical Registrants:
C.
Use Profile
Sodium chlorate, soda chlorate, chloric acid, sodium salt
Sodium chlorate
Ferti-Lome, Barespot, Tri-Kil, Bareground, Prometon, Pramitol,
Killsall, TriChlor
Inorganic salt
4049
7775-09-9
073301
106.5
NaClO3
EKA Chemicals, ERCO Chemicals, Kerr-McGee Chemical,
Nexen Chemical USA, Moore Agricultural Products Company, Inc.
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.
-------
Type of Pesticide:
Target Pest:
Mode of Action:
Use Sites
Agricultural uses:
Non-agricultural Uses:
Use Classification:
Formulation Types:
Application Methods:
Application Rates:
Herbicide (desiccant/defoliant)
Broadleaf weeds
Non-selective, contact herbicide that penetrates the cuticle causing
cell death by altering the metabolic processes.
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.
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.
General Use
Agricultural products are all formulated as soluble
concentrates/liquids; non-crop products are formulated as soluble
concentrates/liquids and granules or pellets/tablets.
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.
In agriculture, rates range from 6 pounds active ingredient per acre
(6 Ib ai/A) to 12.5 Ibs ai/A. Industrial and other noncrop site rates
range from 132 to 1032 Ibs 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
-------
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 Ibs 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.
-------
HI. 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
-------
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
870.1100
870.1200
870.1300
870.2400
870.2500
870.2600
Study Type
Acute oral -Rats
Acute dermal - Rabbits
Acute inhalation - Rats
Acute eye irritation - Rabbit
Acute dermal irritation -
Rabbit
Skin sensitization - guinea
pigs
MRID No.
41819901
42497601
41819903
00085090
00102998
41819904
42497602
41819906
Results
LD50>5000 mg/kg (rat)
LD50 = > 2000 mg/kg
LC50 = 5.59 mg/L
mildly irritating
minimally irritating
not a dermal sensitizer
Toxicity Category"
IV
III
IV
III
III
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 (lOx) 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 lOx 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 Ix. 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 lOx FQPA SF can be removed (reduced to Ix).
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
-------
was 58 mg/kg/day. If the NOAEL from the monkey study were used to derive a chronic RfD
with uncertainty factors of lOx for interspecies extrapolation and 10X for intraspecies variability,
and an FQPA SF of lOx 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 lOx, 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 lOx for a thyroid toxicant like sodium chlorate. The
half-life of thyroid hormone T4 in rats is approximately 12 hours, whereas in humans, the half-
life 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 lOx 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.
-------
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 lOx intraspecies)
Chronic RfD = 0.03
mg/kg/day
FQPA SF = IX
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 = IX
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 = IX
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
-------
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 hypoxanthine-
guanine 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 Disrupter 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 (C1(V), chlorite (CICV), and chloride (Cl"). Based on published rat metabolism data,
10
-------
terminal residues of sodium chlorate in animal tissues are also expected to be chlorate (C1CV), chlorite
(CICV), and chloride (CY).
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 (CICV,
oxidation state III) and hypochlorite (CIO", 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 (CICV) 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 (C1(V) 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
11
-------
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 chemical-
specific 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
All populations
All infants (< 1 year old)
cPAD
(mg/kg/day)
0.03
Exposure (mg/kg/day)
0.002730
0.004511
% cPAD
9
15
12
-------
Table 3. Results of Chronic Dietary (Food only) Exposure Analysis
Children 1-2 years old
Children 3-5 years old
0.008376
0.006906
28
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 DEEM-
FCID™ 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/non-
crop 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 (DBF). 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
13
-------
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 |ig/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 (C1(V) 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 (CICV) 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.
14
-------
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
15
-------
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
Number of Public Water Systems
Number of Water Treatment Plants
Hypochlorite
Plants3
44
61
Chlorine Dioxide
Plants'1
22
29
Combined Hypochlorite
and Chlorine Dioxide
Plants
66
90
Chlorate Concentration Qa.g/L)
10th Percentile
20th Percentile
50th Percentile (Median)
80th Percentile
90th Percentile
Maximum
23
37
99
155
239
502
52
79
129
217
264
691
24
53
108
179
242
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 0.1 Img/L, the risk was 25%
16
-------
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
Population Subgroup
General U.S. Population
All Infants (< 1 yr)
Children l-2yrs
Children 3-5 yrs
Children 6-12 yrs
Youth 13-19 yrs
Adults 20-49 yrs
Adults 50+ yrs
Females 13-49 yrs
cPAD
mg/kg/day
0.03
% cPAD
Water Estimated
at the
Highest Annual
Average
(0.69 mg/L)
49
159
72
67
47
35
45
48
45
Water Estimated
at the
90th Percentile
Annual Average
(0.24 mg/L)
17
55
25
23
16
12
16
17
16
Water
Estimated at the
Median Annual
Average
(0.11 mg/L)
8
25
12
11
7
6
7
8
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 lOOx (lOx to
account for interspecies extrapolation and lOx for intraspecies variation), plus any additional
FQP A SF retained due to concerns unique to the protection of infants and children. The FQP A
SF for sodium chlorate is reduced tolx for reasons explained above; thus, the Agency's LOG 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
17
-------
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 LOG.
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 #)
Mixing/loading/applying liquids with a
low pressure hand wand sprayer
Loading/applying RTU liquid with a
trigger pump sprayer
Mixing/loading/applying liquids with a
sprinkler can
Applying liquid with a RTU sprinkler
can
Applying granules by hand
Loading and applying granules with a
Daily Area
Treated
1000 ft2/day
1 gallon/day
1000 ft2/day
1 gallon /day
1000 ft2/day
1000 ft2/day
Crop/Target
Spot/edging treatment
Spot/edging treatment
Spot/edging treatment
Spot/edging treatment
Spot/edging treatment
Spot/edging treatment
Application
Rate
23.7
Ib ai/1000 ft2
0.196
Ib ai/gallon
23.7
Ib ai/1000 ft2
0.27
Ib ai/gallon
12
Ib ai/1000 ft2
12
Inhalation
MOE2
3000
87000
5200
710000
370
2800
18
-------
Table 6. Sodium Chlorate Residential Risk Estimates1
Exposure Scenario (Scenario #)
belly grinder
Loading and applying granules with a
push-type spreader
Daily Area
Treated
1000 ft2/day
Crop/Target
Spot/edging treatment
Application
Rate
Ib ai/1000 ft2
12
Ib ai/1000 ft2
Inhalation
MOE2
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-to-
mouth, 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
19
-------
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
Child
Scenario
Hand-to-Mouth
Object-to-Mouth
Soil Ingestion
Route
Oral
Oral
Oral
MOE
29000
110000
8600000
Combined MOE
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 non-
occupational 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.
20
-------
Table 8. Short-Term Aggregate Risk Calculations
Population
Adult
Target Aggregate
MOE
100
MOE
Food +
water
1715
MOE inhalation
400
Aggregate MOE
(food + water + residential)
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 LOG. 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
Population Subgroup"
General US Population
All Infants (< 1 yr)
Children l-2yrs
Children 3-5 yrs
cPAD
(mg/kg/day)
0.03
% cPAD (food + drinking water)
Highest Annual
Average
(0.69 mg/L)
58
174
100
90
90th Percentile
Annual
Average
(0.24 mg/L)
26
70
53
47
Median Annual
Average
(0.11 mg/L)
17
40
39
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.
21
-------
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:
22
-------
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 Ib ai per acre (MOE = 42) and 523 Ib ai per acre (MOE = 84);
Loading granules for tractor-drawn spreader applications to industrial/non-crop
sites at 523 Ib ai per acre (MOE = 59);
• Applying sprays to industrial/non-crop sites using groundboom equipment (open
cab) at 1032 Ib ai per acre (MOE = 69); at 523 Ib ai per acre (MOE = 140);
Mixing/Loading/Applying liquids for low pressure handwand applications to
industrial/non-crop sites at 1032 Ib ai per acre (MOE = 34) and 523 Ib ai per acre
(MOE = 67); and
Loading/Applying granules to industrial/non-crop sites using a belly grinder at
523 Ib 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 Ib 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.
23
-------
Table 10. Sodium Chlorate: Short- and Intermediate-Term Occupational Inhalation Exposure
Exposure
Scenario
Daily
Area
Treated1
Crop/Target
Application
Rate
(Ib ai/A)
Baseline
Inhalation
MOE2
PPE3
Engineering
Controls
Mixer/Loaders
Mixing/Loading
liquids for aerial
application
Mixing/Loading
liquids for
groundboom
application
Mixing/Loading
liquids for rights-
of-way sprayer
application
Loading granules
for tractor-drawn
spreader
application
1200
350
200
80
40
5
40
Cotton, Corn, Rice, Dry
Beans, Grain Sorghum,
Flax, Safflower,
Sunflower, Soybeans
Fallow Land, Wheat
Chili Peppers (for
processing only), Potatoes
Ornamental Gourds,
Cucurbits (grown for seed)
Guar Beans, Southern Peas
Cotton, Corn, Rice, Dry
Beans, Grain Sorghum,
Flax, Safflower,
Sunflower, Soybeans
Fallow Land, Wheat
Chili Peppers (for
processing only), Potatoes
Ornamental Gourds,
Cucurbits (grown for seed)
Guar Beans, Southern Peas
Industrial/Non-Crop Sites
Rights-of-Way &
Industrial/Non-Crop Sites
Industrial/Non-Crop Sites
7.5
6
12.5
6
7.5
7.5
6
12.5
6
7.5
1032
523
132
1032
523
132
523
240
161
190
240
400
830
670
1200
1500
1800
3600
2900
42
84
330
340
670
2700
59
130
190
210
420
300
Applicators
Aerial spray
applications
(enclosed cockpit)
1200
Cotton, Corn, Rice, Dry
Beans, Grain Sorghum,
Flax, Safflower,
Sunflower, Soybeans
7.50
3400
24
-------
Table 10. Sodium Chlorate: Short- and Intermediate-Term Occupational Inhalation Exposure
Exposure
Scenario
Groundboom
spray applications
Rights-of-way
sprayer
applications
Tractor-drawn
spreader
applications
Daily
Area
Treated1
350
1200
350
40
5
40
Crop/Target
Fallow Land, Wheat
Guar Beans, Southern Peas
Chili Peppers (for
processing only), Potatoes
Ornamental Gourds,
Cucurbits (grown for seed)
Cotton, Corn, Rice, Dry
Beans, Grain Sorghum,
Flax, Safflower,
Sunflower, Soybeans
Fallow Land, Wheat
Guar Beans, Southern Peas
Chili Peppers (for
processing only), Potatoes
Ornamental Gourds,
Cucurbits (grown for seed)
Industrial/Non-Crop Sites
Rights-of-Way &
Industrial/Non-Crop Sites
Industrial/Non-Crop Sites
Application
Rate
(Ib ai/A)
6
7.5
12.5
6
7.5
6
7.5
12.5
6
1032
523
132
1032
523
132
523
240
161
Baseline
Inhalation
MOE2
1900
2400
4700
2800
5900
69
140
540
110
210
820
84
180
270
PPE3
340
420
Engineering
Controls
4300
12000
7100
15000
1200 (closed
cab)
2300 (closed
cab)
9200 (closed
cab)
460 (closed
cab)
990 (closed
cab)
1500 (closed
cab)
Flaggers
Flagging for
aerial spray
applications
350
Various Agricultural
Crops
12.5
1400
Mixer/Loader/Applicators & Loader/Applicators
M/L/A liquids
with a low
pressure
handwand sprayer
2
Industrial/Non-Crop Sites
1032
523
132
34
67
270
170
330
25
-------
Table 10. Sodium Chlorate: Short- and Intermediate-Term Occupational Inhalation Exposure
Exposure
Scenario
M/L/A liquids
with a handgun
sprayer
L/A granules with
a belly grinder
L/A granules with
a push-type
spreader
Daily
Area
Treated1
5
1
5
Crop/Target
Industrial/Non-Crop Sites
Industrial/Non-Crop Sites
Industrial/Non-Crop Sites
Application
Rate
(Ib ai/A)
1032
523
132
523
240
161
523
240
161
Baseline
Inhalation
MOE2
230
450
1800
65
140
210
110
240
360
PPE3
320
Engineering
Controls
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.
26
-------
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
27
-------
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 (CIO 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.
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.
28
-------
Table 11. EPA's Ecological Levels of Concern (LOCs) and Risk Presumptions
If a calculated RQ is greater than the LOG presented, then the Agency presumes
that...
Acute Risk . . .there is potential for acute risk; regulatory action may be warranted in
addition to restricted use classification
Acute Endangered Species ...endangered species maybe adversely affected
Chronic Risk . . .there is potential for chronic risk
LOC
terrestrial
animals
0.5
0.1
1
LOC
aquatic
animals
0.5
0.05
1
LOC
plants
1.0
1.0
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
Chili peppers; white/Irish potatoes
Cotton
Corn; flax, guar; southern peas; rice;
safflower; sorghum; soybeans; sunflower
Maximum labeled
application rate
12.5 Ibs ai/A
7.5 Ibs ai/A
7.5 Ibs ai/A
No. of
applications
1
2
1
Application
interval
N/A
30 days
N/A
29
-------
Table 12. Input Parameters for Sodium Chlorate Used in ELL-FATE
Crop
Agricultural fallow land; dried beans; corn;
cucurbits, flax, gourds; guar; southern peas;
white/Irish potatoes; rice; safflower; sorghum;
soybeans; sunflower
Maximum labeled
application rate
6 Ibs ai/A
No. of
applications
1
Application
interval
N/A
The predicted upper 90th percentile and mean chlorate EECs (agricultural and non-
agricultural 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
short
grass
tall grass
broadleaf
forage,
small
insects
fruit,
pods,
seeds,
small
insects
Predicted Mean Residue Levels
short
grass
tall grass
broadleaf
forage,
small
insects
fruit,
pods,
seeds,
small
insects
Agricultural Uses (Spray Applications)
Chili peppers;
white/Irish potatoes
Cotton
Corn; flax, guar;
southern peas; rice;
safflower; sorghum;
soybeans; sunflower
Agricultural fallow
land; dried beans; corn;
cucurbits, flax, gourds;
guar; southern peas;
white/Irish potatoes;
rice; safflower;
sorghum; soybeans;
sunflower
3000
2800
1800
1400
1400
1300
830
660
1700
1600
1000
810
190
170
110
90
1100
990
640
510
450
420
270
220
560
520
340
270
88
81
53
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
30
-------
Table 13. EECs (mg ai/kg-food item) for Terrestrial Animal Risk Assessment for Sodium Chlorate
Crops
Parking lots, fence
lines, building
perimeters, ditch banks,
picnic areas, vacant
lots, wood decks,
bleachers, cemeteries,
fuel tanks, runways,
helo pads, etc.
Predicted 90th Percentile Residue Levels
short
grass
125,000
tall grass
57,000
broadleaf
forage,
small
insects
70,000
fruit
pods,
seeds,
small
insects
7800
Predicted Mean Residue Levels
short
grass
44,000
tall grass
19,000
broadleaf
forage,
small
insects
23,000
fruit
pods,
seeds,
small
insects
3600
For granular applications, estimation of chlorate loading per unit area (mg/ft ) 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
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.
Around buildings, storage areas, fences, pumps, machinery, fuel
tanks, recreational areas, roadways, guard rails, airports, rights of
ways.
Application Rate
(Ibs ai/A)
520
160
EEC (mg/ft2)3
5400
1700
a. EEC = Application rate (Ibs/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.
31
-------
Table 15. Toxicity Reference Values for Mammals and Birds for Sodium Chlorate.
Exposure
Scenario
Species
Toxicity Value Used in
Risk Assessment
Effect
Mammals
Acute
Chronic
Rat
Rat
LD50 = > 5000 mg/kg-bw
NOAEC = 500 mg/kg-bw,
highest dose tested
(approx. 10,000 ppm)
At 5000 mg/kg-bw, 1/10 animals died.
No reproductive effects
Birds
Acute
Chronic
Mallard duck
Bobwhite
quail
LD50 > 25 10 mg/kg-bw
NOAEC = 271 ppm
No mortality and no clinical signs of toxicity
were observed.
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
LOG 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
Chili peppers; white/Irish potatoes
Cotton
Corn; flax, guar; southern peas; rice;
safflower; sorghum; soybeans;
sunflower
Agricultural fallow land; dried beans;
corn; cucurbits, flax, gourds; guar;
southern peas; white/Irish potatoes;
rice; safflower; sorghum; soybeans;
sunflower
Short grass
11.0
10.0
6.6
5.2
Tall grass
5.2
4.8
3.1
2.4
Broadleaf forage,
small insects
6.3
5.9
3.7
3.0
Fruit, pods, seeds,
small insects
0.7
0.63
0.41
0.33
Chronic RQs for birds are not presented for chlorate's non-agricultural uses (granular or
32
-------
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 non-
agricultural 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
Short grass
Tall grass
Broadleaf
plants/small insects
Fruits, pods, large
insects
Size of mammal
(grams)
15
35
1000
15
35
1000
15
35
1000
15
35
1000
Adjusted lowest
observed toxic dose
(mg/kg-bw)
10,989
8891
3846
10,989
8891
3846
10,989
8891
3846
10989
8891
3846
Range of EECs
(mg/kg-bw)a
1400 - 2900
950 - 2000
200 - 450
630 - 1300
440-910
99-210
770 - 1600
540-1100
120 - 250
86 - 180
59 - 120
14-28
Ratio of lowest
observed toxic dose
to the upper 90th
percentile EEC
(unitless)
0.13-0.26
0.11-0.22
0.052-0.12
0.057-0.12
0.049-0.10
0.026-0.055
0.070-0.15
0.061-0.12
0.031-0.065
<0.01 -0.016
0.01-0.013
O.01 -O.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 LOG of 1.0 and 0.1, respectively, with the exception of small
33
-------
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 LOG 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 LOG 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
LDso has not been established. The highest dose tested in the available toxicity studies (5000
mg/kg-bw) induced 10% mortality. The proximity of the LDso 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 non-
agricultural 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
Short grass
Tall grass
Broadleaf
plants/small
insects
Fruits, pods,
large insects
Size of
mammal
(grams)
15
35
1000
15
35
1000
15
35
1000
15
35
1000
Adjusted lowest observed
toxic dose
(mg/kg-bw)
10989
8891
3846
10989
8891
3846
10989
8891
3846
10989
8891
3846
Range of EECs
(mg/kg-bw)a
11,900-119,000
8200 - 82,000
1900 - 19,000
5400 - 54,000
3800 - 38,000
860 - 8600
6700 - 67,000
4600 - 46,000
1100-11,000
740 - 7400
520 - 5200
120 - 1200
Ratio of lowest observed toxic
dose to the upper 90th
percentile EEC (unitless)
1.1- 11
0.93-9.3
0.49-4.9
0.49-4.9
0.43-4.3
0.22-2.2
0.61-6.1
0.52-5.2
0.27-2.7
0.07-0.7
0.06-0.6
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 Ibs ai/A and 520 Ibs 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
34
-------
EECs (mg/ft ). 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 LOG 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
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.
Around buildings, storage areas, fences,
pumps, machinery, fuel tanks, recreational
areas, roadways, guard rails, airports,
rights of ways.
Body Weight
(g)
15
35
1000
15
35
1000
Rat LD50
mg/kg-bw
10,989
8891
3846
10,989
8891
3846
EEC (rag/ft2)3
5400
5400
5400
1700
1700
1700
Ratio of LD50
to EEC
33
17
1.4
10
5.4
0.43
a. EEC = Application rate (Ibs/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 LOG 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 Ibs ai/A
Chili peppers; white/Irish
potatoes
Short Grass
2.6
2.2
1.2
35
-------
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 Ibs ai/A
Chili peppers; white/Irish
potatoes
Tall Grass
Broadleaf
plants/small
insects
Fruits/pods/large
insects
1.2
1.5
0.16
1.0
1.3
0.14
0.55
0.67
0.07
Multiple applications (7.5 Ibs ai/A, 2 applications, 30-day interval)
Cotton
Short Grass
Tall Grass
Broadleaf
plants/small
insects
Fruits/pods/large
insects
2.4
1.1
1.4
0.15
2.1
0.95
1.2
0.13
1.1
0.51
0.62
0.07
Single application (7.5 Ibs ai/A)a
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
Short Grass
Tall Grass
Broadleaf
plants/small
insects
Fruits/pods/large
insects
1.6
0.72
0.88
0.10
1.3
0.61
0.75
0.08
0.72
0.33
0.40
0.04
a. EECs and RQs are similar for the 7.51bs a.i/A (corn, et al.) and 6.0 Ibs a.i./A (agricultural fallow land, et al.) and
single applications, and LOG exceedances are equivalent; therefore, only results from the single application of 7.5
Ibs 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.
36
-------
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 LCso to the
highest concentration tested (1000 mg/L) could not be estimated. Although 1000 mg/L is not an
LCso, 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 LOG of 0.5 and the acute
endangered species LOG 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
37
-------
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 ECso of 920 mg/L (daphnids)
and EECs calculated by GENEEC-2; these are presented in Table 21 below. All RQs are below
the acute LOG of 0.5 and the endangered species acute LOG 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
Agricultural uses
Non-agricultural uses
Application Rate Range
4.5-7.5 Ib ai/A
132-520 Ib ai/A
Maximum EEC
0.91 mg/L
39 mg/L
EC50
920 mg/L
920 mg/L
RQ
0.01
0.042
For saltwater invertebrates, acute RQs were not calculated, because the proximity of the
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 LOG of 0.5, in addition to the
endangered species acute LOG 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 (ECso) 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 ECso values.. For sodium chlorate, the LOG (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
Agricultural
Non-agricultural
Maximum Peak
EEC
Up to 0.9 mg/L
Up to 39 mg/L
Algal EC50
133 mg/L
133 mg/L
Duckweed EC50
43 mg/L
43 mg/L
Algal RQ
O.01
Up to 0.29
Duckweed RQ
0.02
0.91
The RQs for endangered aquatic plants are presented in Table 23. The Agency calculates
38
-------
RQs for endangered aquatic plants by dividing EECs by NOAECs. For endangered aquatic
plants, the Agency's LOG (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
Agricultural
Non-Agricultural
Maximum Peak
EEC
Up to 0.9 mg/L
Up to 39 mg/L
Algal ECSO
62.5 mg/L
62.5 mg/L
Duckweed ECSO
3.1 mg/L
3.1 mg/L
Algal RQ
Up to 0.0 14
Up to 0.62
Duckweed RQ
Up to 0.29
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
39
-------
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,
40
-------
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
LOG, 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
41
-------
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 IX 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 Disrupter 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 Disrupter 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 Disrupter 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/.
42
-------
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 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.
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.
Following this future species-specific analysis, a determination that there is a likelihood
of potential impact to a listed species or its critical habitat may result in: limitations on the use
of sodium chlorate, other measures to mitigate any potential impact; or consultations with the
Fish and Wildlife Service or the National Marine Fisheries Service as necessary. If the Agency
determines use of sodium chlorate "may affect" listed species or their designated critical habitat,
EPA will employ the provisions in the Services regulations (50 CFR Part 402). Until that
species-specific analysis is completed, the risk mitigation measures being implemented through
this RED will reduce the likelihood that endangered and threatened species may be exposed to
sodium chlorate at levels of concern. EPA is not requiring specific sodium chlorate label
language at the present time relative to threatened and endangered species. If, in the future,
specific measures are necessary for the protection of listed species, the Agency will implement
them through the Endangered Species Protection Program.
43
-------
D. Tolerance Reassessment Summary
Table 24 summarizes the reassessment of the sodium chlorate tolerance exemptions
pending a safety finding can be made for sodium chlorite. 40 CFR must be updated to reflect the
tolerance exemptions in the table below. The tolerance exemptions listed in 40 CFR must be
reorganized in order to: (i) incorporate the recommendations made by the Agency concerning the
sodium chlorate residues of concern that need to be regulated for plant and animal commodities;
(ii) include tolerance exemptions that are needed to cover sodium chlorate residues of concern
in/on the raw agricultural commodities and processed commodities of rotational crops; and (iii)
conform with the requirements of FQPA.
Table 24. Tolerance Reassessment Summary for Sodium Chlorate
Listed under 40 CFR 180.1020(a)
Commodity
Beans, dry, edible
Corn, fodder
Corn, forage
Corn, grain
Cottonseed
Flaxseed
Flax, straw
Guar beans
Peas, southern
Potatoes
Peppers, chili
Rice
Rice, straw
Safflower, grain
Sorghum, grain
Sorghum, fodder
Sorghum, forage
Soybeans
Current
Tolerance
(ppm)
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Tolerance
Reassessment
(ppm)
Exempt
Exempt
Exempt
Exempt
Revoke
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
Exempt
[Correct Definition]
Comments
[Bean, dry, seed]
[Com, field, stover; Corn, field, forage; Corn, field,
grain; Corn, sweet, stover; Corn, pop, stover; Corn,
pop, grain; Corn, sweet, forage]
[Cotton, undelinted seed]
[Flax, seed]
Flax straw is not listed in Table 1 of OPPTS
860.1000
[Guar, seed]
[Pea, southern, seed]
[Potato]
[Pepper, nonbell]
[Rice, grain; Rice, straw]
[Safflower, seed]
[Sorghum grain, grain; Sorghum, grain, stover;
Sorghum, grain, forage]
[Soybean, seed]
44
-------
Table 24. Tolerance Reassessment Summary for Sodium Chlorate
Listed under 40 CFR 180.1020(a)
Sunflower seed
Wheat
Exempt
None
Exempt
Exempt
[Sunflower, seed]
[Wheat, grain]
Listed under 40 CFR 180.1020(b)
Wheat
Exempt
Revoke
[Wheat, grain] Time-limited exemption currently
expires on 12/3 1//2006
Existing Exemptions
Sodium chlorate is currently registered for preharvest and foliar applications as a
defoliant or desiccant to the following food/feed crops: beans, corn, cotton, flax, guar, chili
peppers, potatoes, rice, safflower, sorghum (grain), southern peas (i.e., cowpeas), soybeans, and
sunflowers.
Sodium chlorate exemptions under 40 CFR 180.1020(a) from the requirement of a
tolerance should be amended as follows to: (1) specify defoliant and desiccant use only, (2)
specify use on crops rather than raw agricultural commodities, and (3) include an exemption for
wheat (grain).
40 CFR 180.1020(a) Sodium chlorate is exempt from the requirement of a tolerance for residues
when used as a defoliant or desiccant in accordance with good agricultural practice on the
following crops: Bean (dry, seed), Corn (field, stover), Corn (field, forage), Corn (field, grain),
Corn (sweet, stover), Corn (pop, stover), Corn (pop, grain); Corn (sweet, forage), Cotton
(undilented seed), Flax (seed), Guar (seed), Peas (southern, seed), Peppers (nonbell), Potatoes,
Rice (grain), Rice (straw), Safflower (seed), Sorghum (grain, grain), Sorghum (grain, stover),
Sorghum (grain, forage), Soybean (seed), and Sunflower (seed).
Under 40 CFR 180.1020(b), a time-limited exemption from the requirement of a
tolerance is established for residues of the defoliant/desiccant in connection with use of the
pesticide under section 18 emergency exemptions granted by EPA. This exemption was granted
for wheat and expires 12/31/06. The use of sodium chlorate on wheat is also addressed herein
with the intention to convert the time-limited exemption status to a permanent exemption from
the requirement of a tolerance under 40 CFR. 1020 (a). The proposed use rate is for a single
application of sodium chlorate to wheat at 6 Ibs ai/A with a 3-day PHI.
Needed Exemptions
Sodium chlorate (873301) as an inert ingredient in herbicide formulation products can be
applied professionally to agricultural (corn, guava, macadamia nuts, sorghum grain, sugarcane,
wheat), commercial (non-agricultural), and residential sites. These conventional pesticide
products contain < 1 % sodium chlorate and can be applied at rates no greater than 0.07 Ib (as
sodium chlorate) per acre.
45
-------
Potassium chlorate (900583) as an inert ingredient in fungicide products can be applied in
poultry premises. These conventional pesticide products contain < 20% potassium chlorate and
can be applied at rates not greater than 0.01 Ib (as potassium chlorate) per 500 ft3. See Table 25
below for the tolerance exemptions needed for sodium chlorate.
Table 25. Tolerance Exemptions Needed for sodium chlorate
Tolerance Exemption
Expression
Sodium chlorate
Potassium chlorate
PC Code
873301
900583
CAS Reg No.
7775-09-9
3811-04-9
40 CFR §
180.920 l
180.930 2
Use
(Pesticidal)
Stabilizer
Oxidizer
List
Classification
3
3
1. Residues listed in 40 CFR §180.920 [formerly 40 CFR§ 180.100(d)] are exempted from the requirement of a
tolerance when used in accordance with good agricultural practice as inert (or occasionally active) ingredients in
pesticide formulations applied to growing crops only.
2. Residues listed in 40 CFR §180.930 [formerly 40 CFR§ 180.100(e)] are exempted from the requirement of a
tolerance when used in accordance with good agricultural practice as inert (or occasionally active) ingredients in
pesticide formulations applied to animals.
Codex/International Harmonization
There are no Codex maximum residue limits (MRLs) for sodium chlorate.
E. Regulatory Rationale
The following is a summary of the rationale for managing risks associated with the use of
sodium chlorate for sodium chlorate products to be eligible for reregistration. Where labelling
revisions are warranted, specific language is set forth in Table 28 of Section V.
1. Human Health Risk Management
a. Dietary (Food) Risk Mitigation
Acute Dietary (Food) Risk
No acute dietary endpoint was selected for sodium chlorate, because effects attributable
to a single dose were not seen in the available data. Therefore, dietary acute risk is not of
concern to the Agency, and no mitigation measures are required to address acute risk.
Chronic Dietary (Food) Risk
The chronic dietary risk assessment for food only is below the Agency's level of concern
(LOG) for the general US population and all population subgroups. The most highly exposed
population subgroup, children 1-2 years of age, was at 28% of the chronic Population Adjusted
Dose (cPAD). Since this is less than 100% of the cPAD, no mitigation is needed.
46
-------
b. Residential Risk Mitigation
All residential (non-occupational) handler and post-application risk estimates for
inorganic chlorates, as active or inert ingredients in conventional pesticide products used in
residential environments, are below the Agency's LOG (i.e., MOEs are greater than the LOG of
100). The handler inhalation MOEs ranged from 370 to 710,000. The post-application
combined MOE (for inert ingredients) was 23,000 for all potential routes of exposure to children;
therefore, no residential mitigation is necessary.
c. Aggregate Risk Mitigation
As discussed in Section III of this RED, aggregate risk refers to the combined risk from
food, drinking water, and residential exposures. Aggregate risk can result from one-time (acute),
short-term and/or chronic exposures.
Acute Aggregate Risk
For sodium chlorate, acute aggregate risk was not assessed, because effects attributable to
a single dose were not seen in the available data. Therefore, acute aggregate risk is not of
concern to the Agency.
Short-Term Aggregate Risk
Short-term aggregate risk was quantitatively assessed for adults only, using the highest
exposure scenario (inhalation exposure while applying granules by hand) resulting in an MOE of
324. Short-term aggregate risk for children was qualitatively assessed and not of concern to the
Agency because the short-term residential risk to children from the use of sodium chlorate as an
inert is minimal (MOE of 23,000). All short-term aggregate risks are below the Agency's LOG
(i.e., MOEs are greater than 100); therefore, no mitigation is necessary.
Chronic Aggregate Risk
Since no chronic residential (non-dietary) exposure scenarios have been identified for
sodium chlorate, the chronic aggregate risk assessment considers exposure only through food
and drinking water. The Agency believes there is no chronic risk of concern, for the US general
population or any subpopulation group, for the reasons described below.
The chronic dietary (water only) risk assessment for chlorate in drinking water, using the
highest annual average concentration from ICR data of 0.69 mg/L, is below the Agency's level
of concern for the general US population and all subgroups except all infants <1 year of age.
The highest exposed population subgroup, all infants <1 year of age, was 159% of the cPAD.
Using the 90th percentile annual average concentration of 0.24 mg/L, the chronic dietary (water
only) risk for all infants <1 year of age was <55% of the cPAD; using the median annual average
concentration estimated at 0.11 mg/L, estimated chronic risk from drinking water was 25% of the
cPAD. The contribution of exposure from food sources increases total dietary risk (food +
drinking water) to 174% of the cPAD for infants <1 year of age at the highest annual average,
47
-------
but remains below EPA's level of concern at the 90th percentile (70% of the cPAD).
Data on the occurrence of chlorate ion in drinking water were available from two primary
sources: the Information Collection Rule (ICR) Auxiliary 1 Database, Version 5.0, and the
AwwaRF research study on the control of chlorate ion in hypochlorite solutions. The most
extensive data are from the ICR where 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. Although the ICR water systems represent
roughly one percent of the total number of drinking water systems in the United States, these
systems serve almost 60% of the population. Under the ICR, 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). Samples were taken throughout the distribution
systems for plants using chlorine dioxide, since the concentration of chlorate is expected to
change within the system due to the conversion of chlorine dioxide to chlorate that occurs in the
presence of chlorine. Plants using hypochlorite solutions were required to collect quarterly
samples of the water entering and leaving the plant.
The AwwaRF data consists of samples collected in 1993 by 111 water treatment plants
using hypochlorite. The majority of the systems in the AwwaRF project serve populations less
than 100,000, and a large subset of those serve populations less than 10,000. Samples of source
water, hypochlorite solution, and finished drinking water from 111 of water systems were
analyzed for chlorate. Only one set of samples was collected for each system, and samples were
not collected at plants using chlorine dioxide. Furthermore, the background information on the
111 water systems that participated in the project was not linked to the samples they provided;
therefore, the chlorate concentrations can not be directly related to the size of the water system or
type of hypochlorite solution in use.
The AwwaRF samples were typically found to have higher concentrations of chlorate
than the samples collected from the larger ICR systems. The difference in chlorate
concentrations could be the result of a number of factors, such as: 1) The AwwaRF data
represents a single point in time, while the ICR data reflects an average over 18 months; 2) most
of the AwwaRF samples were collected from utilities that served populations of less that
100,000, while all of the ICR samples were from utilities serving at least 100,000; and 3)
hypochlorite treatment plant practices may have changed between when the AwwaRF samples
were collected (1993) and the ICR samples were collected (1997-1998). When the AwwaRF
study was conducted, utilities were just becoming aware of the formation of chlorate ion in
hypochlorite solutions. The AwwaRF project was funded in order to provide water treatment
facilities with information on how to minimize the formation of chlorate byproduct; it is possible
that facilities consequently revised their treatment practices.
The ICR Database was considered the more appropriate source for estimating exposure
averages from individual water treatment plants, primarily because the AwwaRF study is a less
robust data set consisting of only one sample per utility, whereas the ICR database collected
multiple samples over an 18 month period, from plants using both hypochlorite and chlorine
48
-------
dioxide. Both the AwwaRF study and the ICR data reveal high concentrations of chlorate ion to
be a local situation affecting a relatively small number of systems. Of the ICR data set, only four
water treatment plants had average chlorate ion concentrations that exceeded the Agency's level
of concern (i.e., 370 ppb or 0.37 mg/L, for the infant subpopulation) including one treatment
plant serving 218,000 people that had the highest annual average (0.69 mg/L). Of the four plants
that exceeded, two treatment plants used chlorine dioxide, and two used hypochlorite. The total
number of people served by the four water treatment plants exceeding 0.37 mg/L represents
0.5% of the ICR population, or 621,000 people. All three exposure ranges (highest average, 90th
percentile, and median) are presented in Section III. Only the "highest average" exposures
resulted in potential chronic risk estimates that were above the Agency's LOG, and only for
infants. Over 99% of the ICR population receives finished water below the Agency's LOG of
0.37 mg/L.
The chlorate ion (CIO 3") is a disinfection byproduct (DBF) of water treatment which can
be formed during the on-site generation of chlorine dioxide (CIO 2"), the decomposition of
chlorine dioxide in the water treatment system, the decomposition of hypochlorite (OC1") during
storage, and the interaction of chlorite ion and free chlorine. Treatment of public water supplies
is necessary to kill pathogens that may exist in the drinking water, such as cholera, typhoid, and
dysentery. Outbreaks of these diseases decreased significantly when disinfection of the water
systems was introduced in the early 1900s. While there are many important public functions of
water treatment, the Agency is taking steps to limit the exposure of chlorate ion as a DBF to the
public.
In order to help reduce potential exposure to chlorate, the Agency's Office of Pesticide
Programs (OPP), in conjunction with the Office of Water (OW), is working with the American
Water Works Association (AWWA), the Chlorine Institute, and individual water communities to
provide community water systems with information on Best Management Practices (BMPs) for
use in drinking water treatment. BMPs may include measures such as production modifications,
operational changes, materials substitution, materials and water conservation, and other such
measures. For example, water systems that use hypochlorite solutions can minimize the levels of
chlorate ion by purchasing high quality hypochlorite solutions and through careful storage during
use. While decomposition of hypochlorite solutions cannot be avoided, the rate of
decomposition can be managed. Among the major factors affecting stability are the following:
concentration of the hypochlorite solution, temperature of the solution, pH of the solution, and
exposure to light sources. The pH of the solution should be in the 12 to 13 range to minimize
decomposition. Hypochlorite solutions should be protected from high temperatures and sunlight,
and storage time should be minimized, both from the time of manufacture to delivery, and from
the time of delivery to use. The solutions can also be diluted to control decomposition as long as
the proper pH is maintained and high quality dilution water is used. The primary ways in which
water systems using chlorine dioxide can control the levels of chlorate in the finished water is
through high efficiency operation of their chlorine dioxide generators and by reducing chlorite
ion concentrations prior to the addition of free chlorine. The BMPs could also include additional
training of the water systems employees on the proper handling of these chemicals.
The Agency believes that sodium chlorate does not constitute a risk of concern to the
general population or any population subgroups, since the LOG exceedances are associated with
49
-------
a small number of water treatment facilities and inappropriate treatment practices. Furthermore,
the Agency anticipates that the community water system outreach strategy previously discussed
will greatly reduce potential drinking water byproduct exposure.
d. Occupational Risk Mitigation
With the consideration of mitigation measures proposed by registrants and the use of
engineering controls (enclosed cockpits or cabs), all occupational handler risks for the use of
inorganic chlorates as an active or inert ingredient in conventional pesticides are below the
Agency's LOG (i.e., MOEs are greater than the LOG of 100). For sodium chlorate, occupational
exposure durations are short- (1-30 days) and intermediate term (1-6 months) only. Long-term
(> 6 months) exposure is not expected based on the use pattern for sodium chlorate. Post-
application dermal and inhalation exposures are negligible due to the chemical's physical and
chemical characteristics as an inorganic salt. No significant amount of sodium chlorate is
expected to be absorbed through the skin and the vapor pressure is negligible; therefore, a post-
application exposure assessment was not conducted.
Antimicrobial Uses of Sodium Chlorate
Risks to handlers treating water systems are below the Agency's LOG; therefore, no
mitigation measures are necessary.
Agricultural Uses of Sodium Chlorate
With the exception of aerial applications, for which enclosed cockpits are required, the
handler and flagger MOEs for sodium chlorate's agricultural uses are below the Agency LOG at
baseline level of protection (long sleeve shirt, long pants, shoes, and socks). MOEs range from
190 (mixing/loading liquids for aerial application on cotton, corn, et al.) to 3600 (mixing/loading
liquids for groundboom application on ornamental gourds and cucurbits). Further, the maximum
application rate for use on cotton will be reduced from 7.5 Ibs ai/A to 6 Ibs ai/A, with a limitation
of one application (except for California, where two applications will be allowed). No additional
mitigation is required for occupational risk resulting from the agricultural uses of sodium
chlorate.
Non-agricultural Uses of Sodium Chlorate
The Agency's review of sodium chlorate labels, in addition to discussions with
registrants, indicates that the current non-agricultural use labels are not reflective of actual use
practices. The non-agricultural use labels currently allow for larger application rates than are
necessary for efficacy, as well as allow for unlimited treatment areas, although sodium chlorate's
non-agricultural formulations are typically used as spot treatments.
Mitigation measures for sodium chlorate's non-agricultural uses to be included on
product labels will reduce risk from the occupational and ecological exposures to sodium
chlorate. The registrants have agreed to the following non-agricultural use mitigation measures
for sodium chlorate:
50
-------
• All non-agricultural uses will be limited to spot treatments only (with the exception of the
granular formulation for use under asphalt, although this use will be limited to an 8000 ft2
treatment area). The uses limited to spot treatments include, but are not limited to:
building perimeters (including farm buildings), driveways, parking lots, fence rows,
military installations, pipelines, railroads, lumberyards, industrial sites (transformers,
generators, utility poles, etc.), tennis court perimeters, picnic areas, bleachers, cemeteries,
fuel tanks, airport runways, helo pads, wood decks, guard rails, highway medians,
sidewalks/walkways, vacant lots, fire hydrants, recreational areas, and other similar areas.
• Use on rights-of-way and ditch banks will be cancelled.
• The label will specify a maximum application rate of 0.9 Ib ai/100 ft2
The Agency generally converts application rates to a per acre basis for assessment
purposes; therefore, the rate of 0.9 Ib ai/100 ft2 is referred to as 392 Ib ai/A in this document.
However, because all non-agricultural uses will be limited to spot treatment applications only, all
392 pounds of a.i. will not be applied on any one given acre. Assuming only one acre is
considered for treatment, sodium chlorate can only be applied to up to 8000 ft2, which equates to
up to approximately 78 Ibs ai being applied to any given acre. It is assumed that more than one
acre will be treated.
Risk calculations have been developed to better represent the current, actual use pattern
for sodium chlorate, and occupational risk was reassessed based on the revised use pattern
discussed above (i.e., application rates, target sites, and amount treated). Following is a
summary of the Inorganic Chlorates: Addendum to the Occupational and Residential Exposure
Assessment for the Reregistration Eligibility Decision (RED) Document, dated May 18, 2006.
All data, factors, and assumptions used in the addendum are the same as those used in the
previous occupational risk assessment. These include, but are not limited to:
• body weight (70 kg representing adult handlers);
• toxicological endpoints (short-/intermediate-term oral NOAEL of 30 mg/kg/day) and
uncertainty factors (Level of Concern (LOG) for the MOE is 100);
• application rates (in Ib ai/A - presented as a range to encompass the various registered
products); and,
• unit exposures (from PHED and/or ORETF database, both of which have undergone
appropriate review by the Human Studies Review Board).
However, factors regarding application equipment used and daily area treated were
revised based on updated use pattern information and proposed product label revisions. The
previous assessment, summarized in Section III, was based on applications with larger, industrial
equipment such as tractor spreaders or groundboom sprayers. As a result of mitigation measures
agreed to by the technical registrants, sodium chlorate applications to non-agricultural areas (i.e.,
building perimeters, ditch banks, bleachers, airport runways, vacant lots, fire hydrants, or as a
pre-paving treatment) will be limited to "handheld" equipment such as rotary spreaders and
51
-------
pump or power sprayers. In addition, the standard Agency assumptions for the amount applied
per work day is based on the application equipment used to determine exposure and risk. Since
submitted information indicates that no more than 8,000 ft2 of an acre (approximately 20%) will
be treated with sodium chlorate, the Agency has adjusted the standard assumptions for acres
treated per day to reflect this spot treatment-type scenario.
Based on the revised assumptions for the daily area treated and on application methods
suitable for spot treatments (low-pressure handwand sprayers, belly grinders, push-type
spreaders), the risks for all non-agricultural uses, even at the currently labeled application rate
(523 Ibs ai/A instead of 392 Ib ai/A), are below the Agency LOG. The higher application rate of
523 Ib ai/A was used, because at the time the Inorganic Chlorates: Addendum to the
Occupational and Residential Exposure Assessment for the Reregistration Eligibility Decision
(RED) Document, dated May 18, 2006, was prepared, the 392 Ib ai/A maximum application rate
mitigation measure was not yet finalized. The mitigation measures outlined above reduce the
occupational risk from all of sodium chlorate's non-agricultural uses to below the Agency's level
of concern at baseline level of protection (long sleeve shirt, long pants, shoes, and socks). The
risks based on the revised non-agricultural use patterns for sodium chlorate are summarized in
Table 26 below.
Table 26: Sodium Chlorate: Short- and Intermediate-Term Occupational Inhalation Exposure
Exposure Scenario
Daily Area
Treated
(Acres/day)
Crop/Target
Application
Rate
(Ibs ai/Acre)a
Inhalation
MOE
(at baseline)
Mixer/Loader/Applicators & Loader/Applicators
Mixing/Loading/Applying
liquids with a low-
pressure handwand
sprayer
M/L/A liquids with a
handgun sprayer
L/A granules with a belly
grinder
L/A granules with a push-
type spreader
0.4
1
0.2
1
Industrial/Non-Crop Sites
Industrial/Non-Crop Sites
Industrial/Non-Crop Sites
Industrial/Non-Crop Sites
523
132
523
132
523
240
161
523
240
161
330
1300
2200
8800
320
710
1100
550
1200
1800
a. Application rate will be reduced to 0.9 Ib ai/100 fir (392 Ib ai/A).
2. Non-Target Organism (Ecological) Risk Management
Chlorate is a strong oxidizer and may be reduced to other chemically related species
under some environmental conditions. The extent and rate to which this occurs will depend on
the redox chemical species (including organic matter) in the water or soil. Extensive spatial and
52
-------
temporal variability is expected for the reactions of chlorate in the environment. However, the
currently available simulation models do not allow for a quantitative evaluation of the potential
exposure levels of each the reduced products of chlorate (i.e., speciation and predominance) and
how fast these chemical species may form. Therefore, there is a high degree of uncertainty in the
ecological exposure and risk assessment. This is important because a reduction product of
chlorate (chlorite) is expected to be more toxic to most aquatic and terrestrial species,
particularly aquatic invertebrates.
a. Terrestrial Organisms
1. Birds and Mammals
EPA's screening-level risk assessment, based on currently labelled maximum application
rates, for both agricultural and non-agricultural uses for sodium chlorate, suggests potential acute
and chronic risk for birds
Avian Acute Risk
Avian acute risk was not calculated, since 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; therefore, acute risk to birds is not expected. However, the Agency cannot
preclude acute or subacute risk from the non-agricultural uses. Some labels have maximum
application rates up to 1032 Ibs ai/A, and the ecological assessment for risk from non-
agricultural uses was based on rates ranging from 52 to 523 Ibs ai/A, with corresponding EECs
from 12,500 and 125,000 ppm, respectively. These EECs are approximately 2.5 to 25-fold
higher than the highest concentration tested in the subacute bird toxicity studies. The non-
agricultural use mitigation outlined above, including the reduction of the maximum application
rate to 392 Ibs ai/A, and a limitation to spot treatments only (except for use under asphalt,
although this use is limited to no more than an 8000 ft2 area). Reducing the maximum
application rate from 520 Ibs ai/A to 392 Ibs ai/A will reduce the estimated environmental
concentrations of chlorate by approximately 25%. Further, to the extent that there is any
potential acute risk to birds from the non-agricultural uses, the fact that these uses will result in
small contiguously treated areas could limit avian exposure.
Avian Chronic Risk
Maximum chronic RQs, based on EECs derived with 90th percentile residue estimates
from the Kenaga nomogram, exceed the Agency's avian LOG of 1.0 for all agricultural uses
assessed for birds eating short grass, tall grass, broadleaf forage, and small insects. Chronic RQs
based on EECs derived with mean residue estimates from the Kenaga nomogram, although not
presented in Section III, would be approximately three times lower for any single application of
sodium chlorate. The highest agricultural use chronic RQ was 11 (chili peppers/white, Irish
potatoes and the short grass food category). The second highest RQs were for cotton (ranging
from 10.0 for the short grass food category, to 0.63 for fruits, pods, seeds, and small insects).
Cotton is also by far the most common agricultural use of sodium chlorate, with approximately
1,900,000 Ibs ai applied annually.
53
-------
To address the chronic risk to birds from use on cotton, the maximum application rate
will be reduced from 7.5 Ibs ai/A to 6 Ibs ai/A, and applications will be limited to a single
applications in all states except California, where a second application will be allowed. This
mitigation measure will reduce chronic risk to birds from use on cotton by approximately one-
half, with RQs ranging from 5.31 (on the short grass food category), to 0.33 (on fruits, pods,
seeds, and small insects) for all states except California. In California, the chronic avian RQs
based on the reduced maximum application rate of 6 Ibs ai/A, and two applications, will be
reduced to a range of 8.25 (on the short grass food category) to 0.52 (on fruits, pods, seeds, and
small insects).
Chronic avian RQs for sodium chlorate were based on a NOAEC of 271 ppm from the
bobwhite quail chronic reproductive toxicity test. However, maximum EECs for a majority of
the uses and classes of food items were also higher than the LOAEC in bobwhite quail of 964
ppm. At the LOAEC, reproductive effects occurred, including a 67% reduction in eggs laid and
64% reduction in number of hatchlings per egg laid. Therefore, if actual exposure is equivalent
to the maximum values calculated with the T-REX model, there is a greater certainty that frank
reproductive effects in birds might occur.
However, the duration of exposure needed to produce reproductive effects in birds is an
uncertainty. This uncertainty is significant in the case of sodium chlorate, because as a broad-
spectrum herbicide, its toxic effects on plants are visible within several days. Since the
vegetation in the treated area will die, it is uncertain whether or not this vegetation will be
attractive to birds as a feed item long enough for the chronic effects to occur.
Chronic RQs were not calculated for sodium chlorate's non-agricultural uses. However,
based on the high application rates and resulting high potential EECs, risks from sodium
chlorate's non-agricultural uses could be considerably higher than those described in Section III
for the agricultural uses. The non-agricultural use mitigation outlined above, including a
reduction in the maximum labeled application rate to 0.9 Ibs ai/100 ft2 (392 Ibs ai/A), would
reduce the EECs of chlorate by approximately 25% in the areas treated. Furthermore, the
limitation of most non-agricultural uses to spot treatments only is expected to reduce the
likelihood that a terrestrial organism will come into contact and consume all of its diet from a
treated area. However, RQs still exceed the chronic LOG for birds (1.0). See the Analysis of
proposed changes to sodium chlorate's application rates and maximum treated area on potential
ecological risks presented in EFED 's reregistration eligibility decision (RED) document, dated
June 13, 2006 for further detail.
Mammalian Acute Risk
Acute RQs were not calculated for mammals. The LDso 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
LDso to 5000 mg/kg-bw is uncertain. Although RQs were not calculated for mammals, Tables
17, 18 and 19 in Section III present a comparison of the body weight adjusted LD50s to EECs for
54
-------
agricultural spray, and the non-agricultural spray and granular, formulations, respectively. These
ratios can be used to estimate high-end risk to exposed mammals. Risk quotients would be lower
than the values in Section III.
For sodium chlorate's agricultural uses, all of the mammalian acute risk estimates are
below the Agency's acute and endangered species LOG of 1.0 and 0.1, respectively, with the
exception of small mammals eating short grass. The highest exceedence is for 15 gram
mammals eating short grass (risk ratio = 0.26); therefore, no mitigation is necessary.
For sodium chlorate's non-agricultural uses, the ratios indicate a potential acute concern
to mammals for both spray and granular formulations, with the highest ratios calculated for small
mammals (ratios =11 and 33 for spray and granular formulations, respectively). While the ratios
presented in Section III suggest that there could be acute risk to mammals of all sizes that forage
in the area where sodium chlorate is applied to non-agricultural use sites, the risk was likely
over-estimated, since an LD50 has not been established. Furthermore, as previously explained, a
reduction in the maximum application rate for the non-agricultural uses to 392 Ibs ai/A would
reduce the EEC's of chlorate in treated areas by approximately 25%. Limitation of the
treatments to spot treatments only would be expected to further reduce the likelihood that a
terrestrial organism will come into contact and consume all of its diet from that area.
Mammalian Chronic Risk
For mammals, the Agency typically evaluates the mammalian reproductive effects for
exposures greater than 30 days. The interpretation of the effects seen in the 2-generation rat
reproduction toxicity study, used to derive the mammalian reproduction toxicity endpoint for
sodium chlorate, is difficult in this respect. While effects were observed at 70 mg/kg-bw and
above, the effects are not clearly associated with reduced reproductive success or survival. The
mammalian reproductive NOAEC is based on the highest dose tested in this study (500 mg/kg-
bw), although no toxic or reproductive effects were observed at this level. Therefore, the
NOAEC could be higher than 500 mg/kg-bw, which would result in lower mammalian
reproduction risk estimates. However, the Agency calculated risk ratios based on the 500 mg/kg-
day NOAEL as a conservative estimate of risk, as presented in Section III. For the agricultural
uses of sodium chlorate, the chronic mammalian LOG 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 (RQs range from 2.6 to 0.07). The mitigation measures
previously outlined for sodium chlorate use on cotton (maximum application rate reduced from
7.5 Ibs ai/A to 6 Ibs ai/A, with the limitation of a single application, except in California, where a
second application will be allowed), will further reduced chronic mammalian risk. Furthermore,
based on the lack of observed reproductive effects in the chronic study and the slight LOG
exceedances for agricultural uses, the Agency does not anticipate a chronic risk of concern to
mammals from these uses.
As with the agricultural uses, mammalian reproduction RQs were not calculated for
sodium chlorate's non-agricultural uses. However, the higher application rates for the non-
agricultural uses, and the resulting higher EECs, suggest that the risk for these uses would be
higher than the risk estimates presented for the agricultural uses. Note that the mammalian
55
-------
reproduction RQs for the agricultural uses of sodium chlorate, presented in Section III, are a
conservative estimate of risk. Furthermore, as previously explained, to reduce risk from sodium
chlorate's non-agricultural uses, the maximum application rate will be reduced to 0.9 Ib ai/100
ft2. This mitigation measure will reduce the EECs by approximately 25%. In addition, the
limitation to spot treatments will reduce the likelihood that mammals will come into contact and
consume all of its diet from a treated area. See the Analysis of proposed changes to sodium
chlorate's application rates and maximum treated area on potential ecological risks presented in
EFED 's reregistration eligibility decision (RED) document, dated June 13, 2006, for further
detail.
2. Non-Target Insects
EPA currently does not estimate RQs for terrestrial non-target insects. In addition, the Agency
has no toxicity data for sodium chlorate. Therefore, EPA will require data to address this uncertainty.
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
1. Fish
There is no acute risk of concern, from either the agricultural or non-agricultural uses of
sodium chlorate, to freshwater or estuarine/marine fish. All risk ratios are less than 0.05, which
is below the Agency's acute LOG of 0.5 and below the acute endangered species LOG of 0.05.
However, some data suggest that brown trout (freshwater fish) could be substantially more
sensitive than other fish species tested to chlorate's toxicity. It is uncertain if these data are
reliable; therefore, the Agency will require additional testing in brown trout to address this area
of uncertainty.
No chronic fish toxicity studies are available to allow for chronic risk to fish to be
quantified. Therefore, the Agency will require data to address this uncertainty.
2. Aquatic Invertebrates
For freshwater invertebrates, acute RQs are below the acute LOG of 0.5 and the
endangered species acute LOG of 0.05, for both agricultural and non-agricultural uses of sodium
chlorate. Therefore, acute risk to freshwater invertebrates is not of concern to the Agency, and
no mitigation is required.
For saltwater invertebrates, the acute risk ratios for sodium chlorate's agricultural and
nonagricultural uses were below the Agency's acute LOG of 0.5, in addition to the endangered
species acute LOG of 0.05 (highest ratio = 0.04 for non-agricultural uses). Therefore, acute risk
56
-------
to saltwater invertebrates is not of concern to the Agency.
Chronic risk to invertebrates (freshwater and saltwater) was not assessed, since treatment-
related effects were not observed at any concentration in available studies.
3. Aquatic Plants
For non-endangered aquatic plants, the Agency's LOG of 1.0 was not exceeded for either
the agricultural or nonagricultural uses of sodium chlorate (highest RQ = 0.91 for non-
agricultural uses). Therefore, risk to non-endangered aquatic plants is not of concern to the
Agency.
For endangered aquatic plants, the Agency's LOG of 1.0 was not exceeded for sodium chlorate's
agricultural uses (highest RQ = 0.29), but the LOG was exceeded for sodium chlorate's non-
agricultural uses (highest RQ = 12.6). However, the mitigation measures listed above for the
non-agricultural uses of sodium chlorate, including a reduction in the application rate and treated
area, result in a reduction of the endangered vascular plant RQ from 12.6 to 1.5. While this is a
significant improvement, it is still above the Agency's endangered plant LOG of 1.0.
Furthermore, because of a lack of submitted data, there is uncertainty remaining on sodium
chlorate's toxicity to aquatic plants. The Agency will require data to address this area of
uncertainty.
3. Summary of Mitigation Measures
The following mitigation measures are necessary for sodium chlorate to be eligible for
reregistration. These include use restrictions, voluntary cancellations and/or use deletions, and
personal protective equipment.
Agricultural use mitigation:
• Engineering controls (enclosed cockpits) for aerial applications on agricultural crops.
• For cotton, the maximum application rate will be reduced from 7.5 Ibs ai/A to 6 Ibs ai/A,
and applications will be limited to a single applications in all states except California,
where a second application will be allowed.
Non-agricultural use mitigation:
• All non-agricultural uses will be limited to spot treatments only (with the exception of the
granular formulation for use under asphalt, although this use will be limited to an 8000 ft2
treatment area). The uses limited to spot treatments include, but are not limited to:
building perimeters (including farm buildings), driveways, parking lots, fence rows,
military installations, pipelines, railroads, lumberyards, industrial sites (transformers,
generators, utility poles, etc.), tennis court perimeters, picnic areas, bleachers, cemeteries,
fuel tanks, airport runways, helo pads, wood decks, guard rails, highway medians,
sidewalks/walkways, vacant lots, fire hydrants, recreational areas, and other similar areas.
57
-------
• Use on rights-of-way and ditch banks will be cancelled.
• The label will specify a maximum application rate of 0.9 Ib ai/100 ft2.
F. Other Labeling Requirements
To be eligible for reregistration, various use and safety information will be included in
the labeling of all end-use products containing sodium chlorate. For the specific labeling
statements and a list of outstanding data, refer to Section V of this RED document.
1. Endangered Species Considerations
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.
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 recommended in
this RED that are being implemented at that time.
Following this future species-specific analysis, a determination that there is a likelihood
of potential impact to a listed species or its critical habitat may result in: limitations on the use of
sodium chlorate, other measures to mitigate any potential impact, or consultations with the Fish
and Wildlife Service or the National Marine Fisheries Service as necessary. If the Agency
determines use of sodium chlorate "may affect" listed species or their designated critical habitat,
58
-------
EPA will employ the provisions in the Services regulations (50 CFR Part 402). Until that
species-specific analysis is completed, the risk mitigation measures being implemented through
this RED will reduce the likelihood that endangered and threatened species may be exposed to
sodium chlorate at levels of concern. EPA is not requiring specific sodium chlorate label
language at the present time relative to threatened and endangered species. If, in the future,
specific measures are necessary for the protection of listed species, the Agency will implement
them through the Endangered Species Protection Program.
2. Spray Drift Management
The Agency has been working closely with stakeholders to develop improved approaches
for mitigating risks to human health and the environment from pesticide spray and dust drift. As
part of the reregistration process, EPA will continue to work with all interested parties on this
important issue.
From its assessment of sodium chlorate, as summarized in this document, the Agency
concludes that certain drift mitigation measures are needed to address the risks from off-target
drift for sodium chlorate, including a requirement for medium to coarse droplet size. Label
statements implementing these measures are listed in the "spray drift management" section of the
label table (Table 28 in Section V of this RED document. In the future, sodium chlorate product
labels may need to be revised to include additional or different drift label statements.
59
-------
V. What Registrants Need to Do
A. Manufacturing-Use Products
1. Generic Data Requirements
The generic data base supporting the reregistration of sodium chlorate has been reviewed
and determined to be substantially complete. However, there are a few data gaps remaining, and
these data, presented in Table 27, must be submitted or the Agency may take regulatory action
on registrations of pesticide products containing sodium chlorate.
Table 27. Guideline Requirements for Sodium Chlorate
Data Requirement
Magnitude of the Residue- Meat/Milk/Poultry/Eggs
Submittal of Analytical Reference Standards
28-Day Inhalation Toxicity
Terrestrial Field Dissipation or Retrospective Monitoring Study
Freshwater Fish Early Life Stage
Avian Reproduction (1 -Generation, Duck)
Seedling Emergence (Tier II only)
Vegetative Vigor (Tier II only)
Aquatic Plant Toxicity, using Lemna spp. (Tier II)
Honey Bee Acute Contact Toxicity
Old Guideline
Number
171-4J
171-13
82-4
164-1
72-4 (a)
71-4b
123-1 (a)
123-1 (b)
123-2
141-1
New OPPTS
Guideline No.
860.1480
860.1650
870.3465
835.6100
850.1400
850.2300
850.4225
850.4250
850.4400
850.3020
While the terrestrial field dissipation (835.6100) guideline study may not be appropriate
for sodium chlorate, the Agency is still concerned about the prolonged use of sodium chlorate on
cotton (about 50 years). Terrestrial field dissipation data are not available for sodium chlorate,
and the guideline requirement for this study was never waived. There are some reports that
sodium chlorate can be persistent in the field (ranging from 6 months to 5 years, depending on
application rate, soil type, fertility, organic matter, moisture, and weather conditions). Also,
several labels report that sodium chlorate is effective for the control of weeds for up to a year,
which indicates that chlorate may persist for up to a year. Therefore, the range of persistence of
sodium chlorate in the field remains a major uncertainty in the environmental fate behavior of
this chemical. Use of sodium chlorate in the field requires that it be applied in conjunction with
a fire retardant to minimize fire incidents. It is unclear how the fire retardant could influence the
persistence in the field. Even though the persistence of chlorate in the field is uncertain, a
terrestrial field dissipation data from a study conducted as per guideline 835.6100 may not
provide adequate data because of the complexity of the chlorine oxyanion system and analytical
chemistry methodology. Given that chloride is the end chemical species of chlorate, it poses the
60
-------
question of increased chloride from year-after-year usage (i.e., salinization), and leaching of
chloride to ground water, particularly in areas where chloride is not a significant, natural
component in soil and/or ground water. Therefore, the Agency recommends a retrospective
monitoring study (soil; ground water) aimed to address the effect of prolong use of sodium
chlorate on cotton. The study must be conducted upon agreement of a protocol, but monitoring
sites in coastal areas should not be included.
2. Labeling for Manufacturing-Use Products
To ensure compliance with FIFRA, manufacturing-use product (MUP) labeling should be
revised to comply with all current EPA regulations, PR Notices, and applicable policies. The
MUP labeling should bear the labeling contained in Table 28.
B. End-Use Products
1. Additional Product-Specific Data Requirements
Section 4(g)(2)(B) of FIFRA calls for the Agency to obtain any needed product-specific
data regarding the pesticide after a determination of eligibility has been made. The registrant
must review previous data submissions to ensure that they meet current EPA acceptance criteria
and if not, commit to conduct new studies. If a registrant believes that previously submitted data
meet current testing standards, then the study MRID numbers should be cited according to the
instructions in the Requirement Status and Registrants Response Form provided for each
product. The Agency intends to issue a separate product-specific data call-in (PDCI) outlining
specific data requirements.
2. Labeling for End-Use Products
To be eligible for reregistration, labeling changes are necessary to implement measures
outlined in Section IV above. Specific language to incorporate these changes is provided in
Table 28. Generally, conditions for the distribution and sale of products bearing old
labels/labeling will be established when the label changes are approved. However, specific
existing stocks time frames will be established case-by-case, depending on the number of
products involved, the number of label changes, and other factors.
C. Labeling Changes Summary Table
For sodium chlorate to be eligible for reregistration, all sodium chlorate labels must be
amended to incorporate the risk mitigation measures outlined in Section IV. Table 28 describes
how language on the labels should be amended.
D. Existing Stocks
Registrants may generally distribute and sell products bearing old labels/labeling for 18
months after the date of approval of revised labels implementing the changes described in this
RED. Registrants and all other persons remain obligated to meet pre-existing label requirements
61
-------
and existing stocks requirements applicable to stocks they sell or distribute.
62
-------
Table 28. Summary of Labeling Changes for Sodium Chlorate
Description
Amended Labeling Language
Placement on Label
Manufacturing Use Products
For all Manufacturing
Use Products
"Only for formulation as a defoliant/dessicant applied to agricultural crops [Registrant insert crops
supported], as an herbicide applied in nonagricultural settings (residential, commercial, and
industrial) or as an antimicrobial for the following uses: - [Registrant, please insert]."
Directions for use
Environmental Hazards
Statements
"ENVIRONMENTAL HAZARDS"
"Do not discharge effluent containing this product into lakes, streams, ponds, estuaries, oceans, or
other waters unless in accordance with the requirements of a National Pollutant Discharge
Eliminations System (NPDES) permit and the permitting authority has been notified in writing
prior to discharge. Do not discharge effluent containing this product to sewer systems without
previously notifying the local sewage treatment plant authority. For guidance, contact your State
Water Board or Regional Office of the Environmental Protection Agency."
Precautionary Statements:
Environmental Hazards
63
-------
Table 28. Summary of Labeling Changes for Sodium Chlorate
Description
Amended Labeling Language
Placement on Label
End-Use Products Intended for Occupational Use (WPS and Non-WPS)
PPE Requirements for
All Formulations
"Personal Protective Equipment (PPE)"
"Some materials that are chemical-resistant to this product are [registrant inserts correct
material(s)]." For more options, follow the instructions for category [insert A, B, C, D, E, F, G or
H] on the chemical-resistance category selection chart.
"All mixers, loaders, applicators, and other handlers must wear:
- long-sleeved shirt and long pants, and
- shoes and socks"
"See engineering controls for additional requirements." Note: this statement should be placed on
labels containing agricultural crop scenarios. It should not be placed on labels where the sole uses
are in nonagricultural settings, including commercial, industrial, or residential.
Immediately
following^elow
Precautionary Statements:
Hazards to Humans and
Domestic Animals
Engineering Controls for
products within the scope
of the Worker Protection
Standard (WPS)
Enclosed Cockpits/Cabs
"Applicators must use an enclosed cockpit or enclosed cab that meets the requirements listed in the
Worker Protection Standard (WPS) for agricultural pesticides [40 CFR 170.240(d)(6)].
Precautionary Statements:
Hazards to Humans and
Domestic Animals
immediately following the
PPE requirements
64
-------
Table 28. Summary of Labeling Changes for Sodium Chlorate
Description
Amended Labeling Language
Placement on Label
User Safety
Requirements
"Follow manufacturer's instructions for cleaning/maintaining PPE. If no such instructions for
washables exist, use detergent and hot water. Keep and wash PPE separately from other laundry.
"Discard clothing or other absorbent materials that have been drenched or heavily contaminated
with this product's concentrate. Do not reuse them."
Precautionary Statements:
Hazards to Humans and
Domestic Animals
immediately following the
PPE requirements
User Safety
Recommendations
"User Safety Recommendations"
"Users should wash hands before eating, drinking, chewing gum, using tobacco, or using the
toilet."
"Users should remove clothing/ PPE immediately if pesticide gets inside, then wash thoroughly
and put on clean clothing."
"Users should remove PPE immediately after handling this product. Wash the outside of gloves
before removing. As soon as possible, wash thoroughly and change into clean clothing."
Precautionary Statements
under: Hazards to Humans
and Domestic Animals
(Must be placed in a box.)
Environmental Hazards
Statements
"ENVIRONMENTAL HAZARDS"
"Do not apply directly to water, or to areas where surface water is present, or to inter-tidal areas
below the mean high water mark. Do not contaminate water when cleaning equipment or
disposing of equipment washwater or rinsate."
Precautionary Statements:
Hazards to Humans and
Domestic Animals
Restricted-Entry Interval
For products within the
scope of the Worker
Protection Standard
(WPS)
"Do not enter or allow worker entry into treated areas during the restricted entry interval (REI) of
12 hours."
Directions for Use, in
Agricultural Use
Requirements box
65
-------
Table 28. Summary of Labeling Changes for Sodium Chlorate
Description
Amended Labeling Language
Placement on Label
Early Reentry Personal
Protective Equipment
For Products Subject to
WPS as required by
Supplement 3 of PR
Notice 93-7
"PPE required for early entry to treated areas that is permitted under the Worker Protection
Standard and that involves contact with anything that has been treated, such as soil or water, is
- coveralls,
- shoes and socks, and
- chemical-resistant gloves made of any waterproof material."
Directions for Use, in
Agricultural Use
Requirements Box
Entry Restrictions for
Non WPS Uses
Product applied as a spray:
"Do not enter of allow others to enter until treated areas have dried"
Products applied dry:
"Do not enter or allow other to enter until dusts have settled."
If no WPS uses on the
product label, place the
appropriate statement in the
Directions for Use Under
General Precautions and
Restrictions. If the product
also contains WPS uses,
then create a Non-
Agricultural Use
Requirements box as
directed in PR Notice 93-7
and place the appropriate
statement inside that box.
General Application
Restrictions
"Do not apply this product in a way that will contact workers or other persons, either directly or
through drift. Only protected handlers may be in the area during application."
Place in the Directions for
Use directly above the
Agricultural Use Box
Application Restrictions-
Agricultural Uses
For cotton, the maximum application rate is 6 Ibs ai/A per application. A maximum of one
application per year is permitted, except in California, where a maximum of two applications per
year is permitted.
Place in the Directions for
Use for applications to
cotton.
Application Restrictions-
Non-agricultural Uses
Application rates for products labeled for non-agricultural use must be amended to reflect the
maximum application rate: 0.9 Ib ai/100 ft2.
Liquid formulations:
"Non-agricultural uses are limited to spot treatments only. Broadcast applications are prohibited."
Place in the Directions
Under Application
Resrictions.
66
-------
Table 28. Summary of Labeling Changes for Sodium Chlorate
Description
Amended Labeling Language
Placement on Label
Use on rights-of-way and ditch banks is prohibited.
Granular formulations:
"Non-agricultural uses are limited to spot treatments with the exception of applications under
asphalt. Applications under asphalt may only be applied with handheld equipment such as a rotery
spreader and are limited to 8,000 square feet per site". Use on rights-of-way and ditch banks is
prohibited.
67
-------
Table 28. Summary of Labeling Changes for Sodium Chlorate
Description
Amended Labeling Language
Placement on Label
Spray Drift Label
Language for Products
Applied as a Spray to
Agricultural Sites
"Spray Drift Management"
"A variety of factors including weather conditions (e.g., wind direction, wind speed, temperature,
relative humidity) and method of application can influence pesticide drift. The applicator must
evaluate all factors and make appropriate adjustments when applying this product."
Wind Speed
"Do not apply at wind speeds greater than 15 mph."
Droplet Size
"Apply as a medium or coarser spray (ASAE Standard 572)"
Temperature Inversions
"If applying at wind speeds less than 3 mph, the applicator must determine if a) conditions of
temperature inversion exist, or b) stable atmospheric conditions exist at or below nozzle height.
Do not make applications into areas of temperature inversions or stable atmospheric conditions."
Other State and Local Requirements
"Applicators must follow all state and local pesticide drift requirements regarding application of
sodium chlorate. Where states have more stringent regulations, they must be observed."
Equipment
"All application equipment must be properly maintained and calibrated using appropriate carriers
or surrogates."
Additional requirements for aerial applications:
1. "The boom length must not exceed 75% of the wingspan or 90% of the rotor blade diameter."
2. "Release spray at the lowest height consistent with efficacy and flight safety. Do not release
spray at a height greater than 10 feet above the crop canopy unless a greater height is required for
aircraft safety."
3. "When applications are made with a crosswind, the swath must be displaced downwind. The
applicator must compensate for this displacement at the up and downwind edge of the application
area by adjusting the path of the aircraft upwind."
Directions for Use under
General Precautions or
Restrictions and/or
Application Instructions
68
-------
Table 28. Summary of Labeling Changes for Sodium Chlorate
Description
Amended Labeling Language
Additional requirement for groundboom application:
"Do not apply with a nozzle height greater than 4 feet above the crop canopy."
Placement on Label
End Use Products Primarily Used by Consumers/Homeowners
Environmental
Hazards Statement
Entry Restrictions
General Application
Restrictions
"ENVIRONMENTAL HAZARDS"
"This product is toxic to fish and shrimp. Do not apply directly to water. Do not contaminate
water when cleaning equipment or disposing of equipment washwaters or rinsate." "Drift and
runoff may be hazardous to aquatic organisms in water adjacent to treated areas."
Products applied as a spray:
"Do not allow adults, children, or pets to enter the treated area until sprays have dried."
Products applied dry:
"Do not allow adults, children, or pets to enter the treated area until dusts have settled."
"Do not apply this product in a way that will contact adults, children, or pets, either directly or
through drift."
Precautionary Statements
under Environmental
Hazards
Directions for use under
General Precautions and
Restrictions
Place in the Direction for
Use
69
-------
Table 28. Summary of Labeling Changes for Sodium Chlorate
Description
Amended Labeling Language
Placement on Label
Application Restrictions
Liquid Formulations
"Use is limited to spot treatments only. Broadcast applications are prohibited Use on ditch banks
is prohibited."
Granular Formulations
"Use is limited to spot treatments only, with the exception of applications under asphalt.
Applications under asphalt are limited to 8,000 square feet per site. Use on ditch banks is
prohibited. "
Application rates for products labeled for non-agricultural use must be amended to reflect the
maximum application rate: 0.9 Ib ai/100 ft2.
Place in the Directions
under Application
Restrictions
70
------- |