Document ID: EPA-HQ-OPP-2011-0569-0005
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2012-09-19T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                            WASHINGTON, D.C.  20460
                                                                               
                                                                               
                                                      OFFICE OF CHEMICAL SAFETY
\* MERGEFORMAT
                                                       AND POLLUTION PREVENTION

MEMORANDUM

Date:  		6/6/2012

SUBJECT:	Clopyralid.  Human Health Risk Assessment for New Uses on Apples, Teff, Brassica Leafy Greens, and Rapeseed 
 
PC Code:  117403 (acid)
         117401 (alkanolamine salt) 
DP Barcode:  D391397, D401055 
Decision No.:  450262, 463332 
Registration Nos.:  62719-73, 62719-80,
                62719-81, and 62719-84  
Petition No.:  1E7882, 2E8013 
Regulatory Action:  Section 3 Registration 
Risk Assessment Type:  Single Chemical
                    Aggregate
Case No.:  NA 
TXR No.:  NA 
CAS No.: 1702-17-6 (acid)
        57754-85-5 (monoethanolamine salt)
MRID No.: NA
40 CFR:  §180.431

FROM:	Douglas A. Dotson, Ph.D., Chemist
		Linnea Hansen, Ph.D., Toxicologist
		Suku Oonnithan, Ph.D., Biologist
		Registration Action Branch II
		Health Effects Division (7509P)

THROUGH:	Karlyn Middleton, M.S., Toxicologist
		Michael A. Doherty, Ph.D., Chemist
		Margarita Collantes, M.S., Biologist
		Christina Swartz, Branch Chief
		Registration Action Branch II
		Health Effects Division (7509P)
		
TO:		Laura Nollen/Barbara Madden, RM Team 5
		RIMUERB
		Registration Division (7505P)

1.0	Executive Summary	4
2.0	HED Recommendations	7
2.1	Data Deficiencies/Conditions of Registration	7
2.2	Tolerance Considerations	7
2.2.1	Enforcement Analytical Method	7
2.2.2	International Harmonization	7
2.2.3	Recommended Tolerances	8
2.2.4	Revisions to Petitioned-For Tolerances	8
2.3	Label Recommendations	8
3.0	Introduction	9
3.1	Chemical Identity	9
3.2	Physical/Chemical Characteristics	9
3.3	Pesticide Use Pattern	9
3.4	Anticipated Exposure Pathways	10
3.5	Consideration of Environmental Justice	11
4.0	Hazard Characterization and Dose-Response Assessment	17
4.1	Toxicology Studies Available for Analysis	11
4.1.1	Sufficiency of Studies/Data	11
4.2	Absorption, Distribution, Metabolism, & Elimination (ADME)	12
4.2.1	Dermal Absorption	12
4.3	Toxicological Effects	12
4.4	Safety Factor for Infants and Children (FQPA Safety Factor)	13
4.4.1	Completeness of the Toxicology Database	14
4.4.2	Evidence of Neurotoxicity	14
4.4.3	Evidence of Sensitivity/Susceptibility in the Developing or Young Animal	14
4.4.4	Residual Uncertainty in the Exposure Database	14
4.5	Toxicity Endpoint and Point of Departure Selections	14
4.5.1	Dose-Response Assessment	14
4.5.2	Recommendation for Combining Routes of Exposures for Risk Assessment	16
4.5.3	Cancer Classification and Risk Assessment Recommendations	16
4.5.4	Summary of Points of Departure and Toxicity Endpoints 	16
5.0	Dietary Exposure and Risk Assessment	17
5.1	Metabolite/Degradate Residue Profile	17
5.1.1	Summary of Plant and Animal Metabolism Studies	18
5.1.2	Summary of Environmental Degradation	18
5.1.3	Comparison of Metabolic Pathways	18
5.1.4	Residues of Concern Summary and Rationale	18
5.2	Food Residue Profile	19
5.3	Water Residue Profile	20
5.4	Dietary Risk Assessment	20
5.4.1	Description of Residue Data Used in Dietary Assessment	20
5.4.2	Percent Crop Treated Used in Dietary Assessment	21
5.4.3	Acute Dietary Risk Assessment	21
5.4.4	Chronic Dietary Risk Assessment	21
5.4.5	Cancer Dietary Risk Assessment	21
5.4.6	Summary Table	21
6.0	Residential (Non-Occupational) Exposure/Risk Characterization	22
6.1	Residential Handler Exposure and Risk	22
6.2	Residential Post-application Exposure	23
6.3	Combined Residential Risk Estimates	24
6.4	Spray Drift	24
7.0	Aggregate Exposure/Risk Characterization	24
7.1	Acute Aggregate Risk Estimates	24
7.2	Short-Term Aggregate Risk Estimates	25
7.3	Intermediate-Term Aggregate Risk Estimates	25
7.4	Chronic Aggregate Risk Estimates	26
7.5	Cancer Aggregate Risk Estimates	26
8.0	Cumulative Exposure/Risk Characterization	26
9.0	Occupational Exposure/Risk Characterization	26
9.1	Short-/Intermediate-Term Handler Risk	26
9.2	Occupational/Commercial Post-application Risk	29
9.2.1	Post-application Inhalation Exposure	29
10.0	References	30
Appendix A.  Toxicology Profile and Executive Summaries	31
A.1	Toxicology Data Requirements	31
A.2	Toxicity Profiles	32
A.3	Hazard Identification and Endpoint Selection	36
A.4	Executive Summaries	39
Appendix B.  Clopyralid Physical/Chemical Properties	50
Appendix C.  Review of Human Research	51

1.0	Executive Summary

The Interregional Research Project Number 4 (IR-4) submitted a tolerance petition proposing the use of the herbicide clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) on apples.  As part of the same tolerance petition, IR-4 proposed to amend the Stinger[(R)] Herbicide label to expand the mustard greens use to the entire Brassica leafy greens subgroup (5B), and to expand the use on canola, crambe, and rapeseed to the entire Rapeseed subgroup (20A), except gold of pleasure.  In addition, IR-4 submitted a separate tolerance petition for the use of clopyralid on teff.

Clopyralid is a pyridine herbicide registered for use on a variety of food and feed crops in the U.S. for the postemergence control of broadleaf weeds, particularly thistles and clover.  The end-use product that IR-4 proposed for use on these commodities is Stinger[(R)] Herbicide (EPA Reg. No. 62719-73), which is a 3 lb acid equivalent (ae)/gal emulsifiable concentrate (EC) formulation of the monoethanolamine salt of clopyralid.

The toxicology database for clopyralid is considered to be complete for characterizing hazard and assessing human health risk.  Toxicity was observed in the rat and dog after chronic exposure, and the mouse after subchronic and chronic exposure, but consistent target organs were not identified.  In dogs, reductions in red blood cell parameters, increased liver weight, and vacuolated adrenal cortical cells were observed, with skin lesions and clinical chemistry changes at the highest dose.  In rats, stomach lesions were observed at the LOAEL, and decreased body weight was observed at the high dose.  In mice, the only observed effects were decreased body weight and weight gain.  No effects were seen in a rabbit 21-day dermal study.

The available studies did not indicate any potential for neurotoxicity, immunotoxicity, or reproductive toxicity, and there is no evidence of increased qualitative or quantitative susceptibility of fetuses or offspring in developmental and reproduction studies.  Additionally, the exposure estimates are based on conservative, health-protective assumptions. 
Therefore, HED has reduced the required 10x Food Quality Protection Act (FQPA) Safety Factor to 1x.

Clopyralid is classified as "not likely to be carcinogenic to humans," based on the lack of treatment-related tumors in the rat and mouse carcinogenicity studies and negative results of the genotoxicity assays.

HED selected endpoints for assessment of human health risk for chronic dietary exposure, occupational and residential inhalation exposure, and residential incidental oral exposure, based on the proposed and existing use patterns and the submitted toxicology studies.  Acute dietary risk was not evaluated because an appropriate endpoint (toxicity from a single dose) was not identified.  Chronic dietary risk (food and drinking water) was evaluated based on gastric lesions in the rat chronic toxicity/carcinogenicity study.  Short-term incidental oral exposure of young children was evaluated based on decreased maternal body weight gain in the rat developmental toxicity study.  Dermal exposure was not evaluated because of the lack of toxicity via the dermal route.  Inhalation exposure was assessed using endpoints and doses obtained from oral studies and route-to-route extrapolation.  Short-term inhalation exposure was evaluated based on decreased maternal body weight gain in the rat developmental toxicity study.  Intermediate-term inhalation exposure was evaluated based on gastric lesions observed by six months' exposure in the rat chronic toxicity/carcinogenicity study, which is considered to be protective for potential portal-of-entry effects to the lungs.  

The nature of the residue in plants and livestock is adequately understood based on acceptable metabolism studies in cabbage, grass, barley, wheat, goats, and poultry.  In plants, the major residue was the parent compound.  In livestock, the major residues are clopyralid and its glycine conjugate.  No changes to the livestock tolerances are being made as a result of the new uses.

In the environment, clopyralid has a low rate of soil sorption, is stable to photolysis and anaerobic metabolism, and is moderately stable to aerobic metabolism.  Because of its stability and high mobility, clopyralid is likely to persist in groundwater.  Based on the available information, OPP has determined that the residue of concern in drinking water is the parent compound only.

The submitted residue data are adequate to support the proposed uses.  The data include adequate field trial studies, processing studies, and storage stability data.  The data support a tolerance at the limit of quantitation (LOQ) of 0.05 ppm for apple fruit.  For the other commodities in the petition, the tolerances are being translated from other commodities with established tolerances.

There is no acute dietary endpoint for clopyralid and clopyralid is classified as "not likely to be carcinogenic to humans."  As a result, an acute dietary exposure assessment was not conducted for the chemical, and there is no cancer risk.  The chronic dietary exposure assessment is highly conservative with regard to protecting human health.  The assessment is based on tolerance-level residues for all commodities and the assumption that 100% of all commodities with tolerances will be treated (i.e., 100% crop treated).  Modeled estimates of clopyralid residues in drinking water have been incorporated into the analyses.  The combined dietary risk estimates from exposure to residues of clopyralid in food and drinking water are not of concern for the U.S. population or any of the population subgroups.  The general U.S. population uses 9.3% of the chronic population-adjusted dose (cPAD).  The population subgroup Children 1-2 years old is estimated to have the highest dietary exposure to clopyralid.  This subgroup uses 25% of the cPAD.  Because such conservative assumptions were made in the assessment, HED is confident that the chronic dietary exposure assessment does not underestimate risk to the general U.S. population or any population subgroup or life stage.  

Although no new residential uses are being proposed, several clopyralid formulations are registered for weed control on lawns, turf, and ornamentals in residential and public areas.  For the purpose of conducting an aggregate risk assessment, a previous residential exposure assessment was updated to incorporate the revisions to the Standard Operating Procedures for Residential Exposure Assessment (Residential SOPs, 2012).  Scenarios assessed include short-term inhalation exposure for residential handlers and post-application oral exposure for children playing on treated lawns.  All residential handler and post-application scenarios resulted in estimated MOEs >=100 and are not of concern.

 The chronic aggregate risk estimates are equivalent to the corresponding dietary (food plus water) risk estimates, which are not of concern.  Short-term aggregate assessments were performed for adults and children.  For the adult short-term aggregate risk assessment, the residential handler inhalation exposure estimate was aggregated with the chronic dietary exposure estimate.  For children, the incidental oral exposure estimate was aggregated with the chronic dietary exposure estimate.  The short-term aggregate risk estimates were not of concern (MOEs >=100).  No specific concerns with respect to environmental justice were identified for clopyralid.       
 
No chemical-specific handler exposure data were submitted in support of this registration.  It is HED policy to use the best available data to assess handler exposure.  Sources of generic handler data, used as surrogate data in the absence of chemical-specific data, include the Pesticide Handlers Exposure Database Version 1.1 (PHED 1.1), the AHETF database, or other registrant-submitted occupational exposure studies.  Some of these data are proprietary (e.g., AHETF data), and subject to the data protection provisions of FIFRA.  Default assumptions established by the HED ExpoSAC were used for parameters such as body weight, acres treated, and amount handled per day.

Occupational handler assessments are based only on inhalation exposures, because clopyralid does not cause systemic toxicity via the dermal route.  The short-term handler inhalation risk estimates are not of concern at the baseline level of personal protective equipment (PPE), which consists of long-sleeved shirt, long pants, socks and shoes.  Further, for intermediate-term exposure, MOEs were >=180,000 assuming baseline PPE.

As stated above, the label amendments that expand the uses of clopyralid on mustard greens and rapeseed commodities to the entire crop subgroups are being proposed without any changes to the registered use patterns.  As a result, a separate occupational exposure assessment is not required to support the proposed label amendments.  Also a separate exposure assessment is not required for the use of Stinger[(R)] Herbicide on teff because the SLN registration is being proposed without any change to the use pattern for wheat. 

Dermal post-application exposure is not of concern because there is no hazard associated with exposure to clopyralid via the dermal route.  Although there is potential for post-application inhalation exposure, a quantitative post-application inhalation exposure assessment was not performed.  However, an inhalation exposure assessment was performed for occupational handlers and the risk estimates were not of concern.  This exposure is likely to result in higher risk than post-application exposure.  Therefore, it is expected that these handler inhalation exposure estimates would be protective of occupational post-application inhalation exposure scenarios.  The submitted parent label for Stinger[(R)] Herbicide is for a monoethanolamine salt of clopyralid acid and has a restricted entry interval (REI) of 12 hours, which is appropriate.

This risk assessment is based, in part, on data from studies in which adult human subjects were intentionally exposed to a pesticide or other chemical.  These studies are compliant with applicable ethics requirements.  Additional information concerning human studies is provided in Appendix C.

2.0	HED Recommendations

HED recommends in favor of granting the requested registrations and establishing the tolerances listed in Table 2.2.3.  

2.1	Data Deficiencies/Conditions of Registration

None

2.2	Tolerance Considerations

2.2.1	Enforcement Analytical Method

Plant Commodity Enforcement Method

The Pesticide Analytical Manual (PAM) Vol. II lists a GC/ECD method for determining clopyralid residues in/on plant commodities (Method I or Method ACR 75.6).  For this method, residues are extracted with dilute NaOH (0.25% or 0.1%) and filtered.  The extract is then acidified and salinized, and residues are partitioned into ethyl ether.  Residues are then methylated using diazomethane and cleaned up on an activated alumina column.  Residues are then determined by GC/ECD using external standards.  The reported LOQs are 0.5 ppm for grains and 2.0 ppm for green forage.  The data gathering method used in the apple field trials is almost identical to the analytical enforcement method, the only difference being the type of alumina column used for sample clean-up.  The method was adequately validated in conjunction with analysis of field trial samples.  The method LOQ and LOD are 0.05 ppm and 0.02 ppm, respectively.

Livestock Commodity Enforcement Method

The Pesticide Analytical Manual (PAM) Vol. II lists a GC/ECD method for the determination of clopyralid residues in animal commodities (Method II or Method ACR 86.1).  Method II is essentially the same as Method I, except that aqueous potassium hydroxide is used for extraction instead of sodium hydroxide.  The reported detection limits are 0.1 ppm for milk and eggs, and 0.2 ppm for liver.
 
Multiresidue Methods

The FDA Pestrak database (PAM Vol. I, Appendix dated 11/6/90) indicates that the existing FDA multiresidue methods are not likely to recover clopyralid.  Clopyralid does appear to be adequately recovered by the "QuEChERS" multiresidue method (http://www.quechers.com).

2.2.2	International Harmonization

There are no Codex or Mexican maximum residue limits (MRLs) for residues of clopyralid in/on the proposed commodities.  However, there is a Canadian MRL for residues of clopyralid in or on flax at 0.2 ppm.  This MRL does not harmonize with the existing U.S. tolerance of 3.0 ppm for flax seed (or the proposed tolerance of 3.0 ppm for the Rapeseed subgroup).  Based on the differing use patterns and the available residue data, the recommended tolerance for the Rapeseed subgroup cannot be harmonized with the Canadian MRL on flax.

2.2.3	Recommended Tolerances

Table 2.2.3 provides a summary of the proposed tolerances, the recommended tolerances, and the correct commodity definitions.

Table 2.2.3.  Tolerance Summary for Clopyralid
                                       
                      Commodity as Proposed by Registrant
                           Proposed Tolerance (ppm)
                         Recom-mended Tolerance (ppm)

Comments
(correct commodity definition)
                              40 CFR §180.431(a)
Apple
                                     0.05
                                     0.05
Adequate field trial data are available.
Leafy Brassica greens subgroup 5B
                                      5.0
                                      5.0
Based on the existing tolerance for mustard greens, the representative commodity of the Leafy Brassica greens subgroup
(Brassica, leafy greens, subgroup 5B)
Rapeseed subgroup 20A, except Gold of pleasure, seed
                                      3.0
                                      3.0
Based on the existing tolerance of 3.0 ppm for rapeseed, canola, and flax seed
(Rapeseed, subgroup 20A, except gold of pleasure)
Rapeseed subgroup 20A, except Gold of pleasure, meal
                                      6.0
                                      6.0
Based on the existing tolerance of 6.0 ppm for canola meal and flax meal
(Rapeseed, meal)
Rapeseed subgroup 20A, except Gold of pleasure, forage
                                      3.0
                                     None
Tolerance is not needed because rapeseed forage is not a significant livestock feed item.
Teff, forage
                                      9.0
                                      9.0
Based on wheat forage (9.0 ppm)
Teff, grain
                                      3.0
                                      3.0
Based on wheat and barley grain (3.0 ppm)
Teff, hay
                                      9.0
                                      9.0
Based on barley hay (9.0 ppm)
Teff, straw
                                      9.0
                                      9.0
Based on wheat and barley straw (9.0 ppm)

2.2.4	Revisions to Petitioned-For Tolerances

None

2.3	Label Recommendations

The submitted supplemental labels for apples, teff, Brassica leafy greens, and the Rapeseed subgroup are adequate.  HED has no label recommendations.

  
3.0	Introduction

3.1	Chemical Identity

Table 3.1.   Clopyralid Nomenclature
Compound
                                       
Common Name
Clopyralid, monoethanolamine salt
Company Experimental Name
Dowco 290
IUPAC Name
3,6-dichloropyridine-2-carboxylic acid, monoethanolamine salt
CAS Name
3,6-dichloro-2-pyridinecarboxylic acid, monoethanolamine salt
CAS Registry Number
1702-17-6 (acid)
57754-85-5 (monoethanolamine salt)
End-use Products (EUP)
Stinger[(R)] Herbicide (EPA Reg. No. 62719-73), 3 lb ae/gal EC

3.2	Physical/Chemical Characteristics

Clopyralid has a relatively low octanol/water partition coefficient.  The log KOW value is -1.81 at a pH of 5 (KOW = 0.015).  Based on this value, the chemical would not bioaccumulate to any great extent.  The relatively low KOW value also decreases clopyralid's potential for dermal absorption.   Clopyralid has a vapor pressure of 1.0 x 10[-][5] mm Hg at 25ºC.  As a result, there is the potential for inhalation exposure.  See Appendix B for a table of clopyralid's physical and chemical properties.     

3.3	Pesticide Use Pattern

A 3.0 lb ae/gal EC formulation of clopyralid is currently registered to Dow AgroSciences (Stinger[(R)]; EPA Reg. No. 62719-73) for control of postemergence weeds in:  (1) mustard greens, (2) canola (rapeseed) and crambe, and (3) barley, oats, and wheat.  IR-4 submitted supplemental labels for the Brassica leafy greens subgroup and the Rapeseed subgroup.  The use directions on those supplemental labels are consistent with the use directions for the commodities from which the tolerances are being extended.  IR-4 also submitted a supplemental label for apples.  Finally, IR-4 submitted a FIFRA 24(c) SLN label for teff.  The use directions are based on the use directions on the Stinger[(R)] label for barley, oats, and wheat.  The proposed use directions are summarized below in Table 3.3. 

Table 3.3.   Summary of Directions for Use of Clopyralid
Applic. Timing, Type, and Equip. [1]
                                  Formulation
                                [EPA Reg. No.]
                                 Applic. Rate 
                                   (lb ae/A)
                          Max. No. Applic. per Season
                          Max. Seasonal Applic. Rate
                                   (lb ae/A)
                                      PHI
                                       
                      Use Directions and Limitations [2]
                                     Apple
Apply to non-bearing (well-established, 1 year or older) and bearing trees.  Apply to actively growing weeds.  Apply with ground equipment only.
                     Stinger, 3.0 lb ae/gal EC [62719-73]
                                  0.094-0.25
                                       1
                                     0.25
                                      30
                                     days
Apply in a minimum of 10 gal/A.  Do not use in Florida or in Nassau or Suffolk Counties, New York.  Do not apply by aircraft.
                     Leafy Brassica Greens Subgroup 5B[3]
Apply to actively growing weeds.  Apply with ground equipment only.
                     Stinger, 3.0 lb ae/gal EC [62719-73]
                                   0.06-0.25
                                       2
                                      0.5
                                      30
                                     days
Apply in a minimum of 10 gal/A, with a minimum RTI of 14 days.  Do not apply by aircraft.
                Rapeseed Subgroup 20A, Except Gold of Pleasure
Apply in the 2- to 6-leaf stage of crop growth.  Apply to actively growing weeds.  Apply with ground and aerial equipment only.
                     Stinger, 3.0 lb ae/gal EC [62719-73]
                                  0.113-0.25
                                       1
                                     0.25
                                       7
                                     days
Use in the State of Oregon only.  Apply in a minimum of 20 gal/A.  Do not use with a surfactant.  Apply with ground and aerial equipment only.
                                     Teff
Apply when crop is from 3-leaf stage up to early boot stage of growth.
                     Stinger, 3.0 lb ae/gal EC [62719-73]
                                  0.094-0.125
                                       1
                                     0.125
                                Not Speci-fied
Do not harvest hay from treated grain fields.[4]
[1]	Do not apply through any type of irrigation system.
[2]	The label for the 3 lb ae/gal EC contains the following rotational crop restrictions:  barley, canola, cole crops, flax, garden beets, grasses, corn (field, pop and sweet), oats, spinach, sugar beets, turnips and wheat may be planted at anytime following a treated crop.  Depending on the amount of soil organic matter, rainfall and location (state), the plant-back intervals for all other crops range from 10.5 to 18 months.
[3]	For use and distribution only in the states of AZ, AR, CA, CO, DE, FL, GA, MD, MI, MO, NJ, NM, NY, NC, OH, OK, PA, SC, TX, VA and WI.  Not for sale or distribution in Nassau and Suffolk Counties in New York State.
[4]	Do not permit lactating dairy animals or meat animals being finished for slaughter to forage or graze treated grain fields within one week after treatment.

The PPE for applicators and other handlers on the registered Stinger(R) Herbicide label is baseline clothing (long-sleeved shirt, long pants, and shoes plus socks), chemical-resistant gloves made of any waterproof material, and protective eyewear.   
  

3.4	Anticipated Exposure Pathways

The Registration Division requested that HED perform an assessment of human health risk to support the proposed new uses of clopyralid.  Humans could be exposed to clopyralid residues through dietary intake of apples, teff, Brassica leafy greens, rapeseed commodities, and drinking water.  The proposed use also results in the potential for occupational (handler/post-application) exposures.

3.5	Consideration of Environmental Justice

Potential areas of environmental justice concerns, to the extent possible, were considered in this human health risk assessment, in accordance with U.S. Executive Order 12898, "Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations," (http://www.eh.doe.gov/oepa/guidance/justice/eo12898.pdf.  As a part of every pesticide risk assessment, OPP considers a large variety of consumer subgroups according to well-established procedures.  In line with OPP policy, HED estimates risks to population subgroups from pesticide exposures that are based on patterns of that subgroup's food and water consumption, and activities in and around the home that involve pesticide use in a residential setting.  Extensive data on food consumption patterns are compiled by the USDA under the Continuing Surveys of Food Intakes by Individuals (CSFII) and are used in pesticide risk assessments for all registered food uses of a pesticide.  These data are analyzed and categorized by subgroups based on age, season of the year, ethnic group, and region of the country.  Additionally, OPP is able to assess dietary exposure to smaller, specialized subgroups, and exposure assessments are performed when conditions or circumstances warrant.  Whenever appropriate, non-dietary exposures based on home use of pesticide products and associated risks for adult applicators and for toddlers, youths, and adults entering or playing on treated areas post-application are evaluated.  Further considerations are currently in development, as OPP has committed resources and expertise to the development of specialized software and models that consider exposure to bystanders and farm workers as well as lifestyle and traditional dietary patterns among specific subgroups.

4.0	Hazard Characterization and Dose-Response Assessment

4.1	Toxicology Studies Available for Analysis

4.1.1	Sufficiency of studies/data	

The toxicology database for clopyralid is considered to be complete.  Studies submitted include a 21-day dermal toxicity study in the rabbit and the following oral studies:  subchronic toxicity in the mouse, chronic toxicity in the dog, chronic toxicity/carcinogenicity in the rat, carcinogenicity in the mouse, prenatal toxicity in the rat and rabbit, reproductive toxicity in the rat, metabolism in the rat, and immunotoxicity in the rat.  In addition, there is a complete battery of genotoxicity studies.  Subchronic studies for rats and dogs are not available; however, requirements for these studies were satisfied by the chronic studies.  

Based on the toxicology data requirements outlined in the recently revised 40 CFR Part 158, acute and subchronic neurotoxicity studies in the rat are required for food use chemicals.  However, HED's Hazard and Science Policy Council (HASPOC) concluded that these studies are not required for clopyralid, based on the lack of evidence of neurotoxicity in the available studies conducted with clopyralid as well as with other structurally related compounds.  HASPOC also determined that a 28-day inhalation toxicity study in the rat (§870.3465) is not required, based on the low volatility, low acute inhalation toxicity, and selection of conservative, adequately protective points of departure from oral studies.

4.2	Absorption, Distribution, Metabolism, & Elimination (ADME)

Metabolism of clopyralid following oral dosing was evaluated in the rat.  Clopyralid was essentially completely absorbed (95-115% of administered dose, or AD) at both low (5 mg/kg/day) and high (150 mg/kg/day) doses.  There were no significant differences in metabolic disposition between males and females or dose groups.  Excretion was primarily via the urine (91-113% AD at 72 hrs post-dosing, with 74-98% AD excreted within 6-12 hrs post-dosing), whether by oral or intravenous dosing.  Less than 4% of the excretion was via feces.  Radioactivity was not retained in tissues (<0.01% AD at 72 hrs post-dosing).  Plasma pharmacokinetic parameters were not evaluated.  There was no evidence of metabolism; only parent compound was identified in the urine and feces.

4.2.1	Dermal Absorption

A dermal absorption study was not required or submitted for clopyralid.  However, absorption appears to be low, based on the lack of toxicity observed at the limit dose in the 21-day rabbit dermal study.  This is consistent with the low Kow identified for clopyralid.

4.3	Toxicological Effects

Clopyralid is an herbicide of the pyridinoxy acid chemical group that is used to control broadleaf weeds.  It is structurally similar to plant auxins and acts as an "auxin imitator," disrupting plant growth by binding to auxin receptors.  However, the mode of action for mammalian toxicity has not been characterized.  

Toxicity was observed in the rat and dog following chronic exposure, but consistent target organs were not identified.  In a one-year dog study, reductions in red blood cell parameters, increased liver weight (males), and vacuolated adrenal cortical cells (females) were reported.  Skin lesions and clinical chemistry changes (decreased serum glucose, protein, albumin) were observed at the highest dose.  In the rat, epithelial hyperplasia and thickening of the limiting ridge of the stomach were observed at the LOAEL, and decreased body weight was observed at the highest dose.  Only decreased body weight/weight gain and food efficiency in males were observed in the mouse carcinogenicity study at doses exceeding the limit dose.  Subchronic data were available only for the mouse, where decreased body weight was observed in a 90-day oral study in males and females at dietary levels exceeding the limit dose (1000 mg/kg/day).  No systemic toxicity or local dermal irritation was observed in rabbits following dermal exposure to the limit dose for 21 days.  A rat immunotoxicity study showed no treatment-related effects on the immune system, and immunotoxicity was also not observed in other studies.  

There was no indication of increased qualitative or quantitative pre- and/or postnatal susceptibility.  No developmental toxicity was observed in the rat at doses that caused maternal mortality and decreased maternal body weight gain.  Decreased fetal body weight and hydrocephalus were observed in the rabbit but only at a dose that caused significant maternal toxicity, including mortality, clinical signs of toxicity, decreased body weight gain, and gastric mucosal lesions.  Reproductive toxicity was not observed in the rat, but mean pup weights (Day 28) were reduced, and relative liver weights were increased at doses that caused parental toxicity (decreased body weight/weight gain and food consumption; gastric lesions).

There were no direct clinical or histopathological indications of neurotoxicity in the available studies at doses up to or exceeding the limit dose.  Hydrocephalus was observed in the young in the rabbit developmental study in the presence of significant maternal toxicity, including a high rate of mortality.  However, no indications of neurotoxicity were observed in maternal animals at the same dose, in other species, or in studies on other structurally related chemicals.  Therefore, acute and subchronic neurotoxicity studies in the rat are not required based on lack of evidence of neurotoxicity for clopyralid and related chemicals.  

Clopyralid is classified as "not likely to be carcinogenic to humans."  No evidence of carcinogenicity was observed in rat and mouse 2-year bioassays at doses exceeding the limit dose.  No positive findings for mutagenicity or clastogenicity were observed in a battery of mutagenicity studies (in vitro and in vivo host mediated assays in Salmonella and Saccharomyces, in vivo chromosomal aberrations, unscheduled DNA synthesis, and dominant lethal assay). 

Clopyralid is rapidly absorbed and excreted, predominantly as parent compound, and primarily in the urine with very low fecal excretion.  It is not retained in tissues (see Section 4.2, above).

The acute toxicity of clopyralid is low (Toxicity Category III or IV) via oral, inhalation and dermal exposure, and it is not a dermal irritant or sensitizer.  However, in its acid form, clopyralid is a severe eye irritant (Category I).

4.4	Safety factor for Infants and Children (FQPA Safety Factor)

HED recommends reduction of the 10x FQPA safety factor for protection of infants and children to 1x.  This recommendation is based on the following considerations:  1) the toxicity database is complete, with required studies either submitted or waived; 2) there is no evidence of increased qualitative or quantitative pre- and/or postnatal susceptibility in the developmental or 2-generation reproduction toxicity studies; 3) there is no evidence of neurotoxicity, and a developmental neurotoxicity study is not required; and 4) the exposure assessments are based on conservative, health-protective assumptions that will not underestimate exposure and risk.

4.4.1	Completeness of the Toxicology Database

The database for clopyralid is considered to be adequate for FQPA assessment.  Acceptable developmental toxicity studies in the rat and rabbit and a two-generation reproduction study in the rat are available for FQPA assessment.  As previously discussed (Section 4.1.1), the required acute and subchronic neurotoxicity and 28-day inhalation studies in the rat have been waived.  Therefore, no additional uncertainty factors are needed to account for missing data.  

4.4.2	Evidence of Neurotoxicity

There are no direct clinical or micropathological indications of neurotoxicity in the available subchronic and chronic studies in multiple species.  Hydrocephalus was observed in the young in the rabbit developmental study in the presence of significant maternal toxicity, including mortality.  However, no indications of neurotoxicity were observed in maternal animals at the same dose, in other species, or in structurally related chemicals.  Therefore, acute and subchronic neurotoxicity studies in the rat are not required based on lack of evidence of neurotoxicity for clopyralid and related chemicals. 

4.4.3	Evidence of Sensitivity/Susceptibility in the Developing or Young Animal

There was no evidence of increased qualitative or quantitative sensitivity/susceptibility in the developing or young animal.  In the rat developmental toxicity study, no developmental toxicity was observed at a maternally toxic dose.  In the rat two-generation reproductive toxicity study, decreased pup weight (postnatal day 28) and increased relative liver weights were observed at the parental LOAEL.  As noted above, hydrocephalus and decreased mean fetal weight were observed in the rabbit developmental study, but at a dose that also caused significant maternal toxicity, including mortality:  the fetal findings were therefore considered to be comparable to those of adult animals.
  
4.4.4	Residual Uncertainty in the Exposure Database

There are no residual uncertainties with regard to dietary and residential exposure.  The dietary exposure assessment is based on conservative, health-protective assumptions that ensure that exposures to clopyralid are not underestimated.  These assumptions include tolerance-level residues and 100% crop treated estimates for all commodities.  Actual exposures and risk estimates from the use of clopyralid will likely be lower.  Furthermore, conservative, upper-bound assumptions were used to determine exposure through drinking water and residential sources, such that these exposures have not been underestimated.  

4.5	Toxicity Endpoint and Point of Departure Selections

4.5.1	Dose-Response Assessment

For acute oral exposure, an endpoint resulting from a single exposure was not identified.  As a result, an aRfD was not determined.  The finding of hydrocephalus in the young in the rabbit developmental study was not considered to be an appropriate endpoint because it was observed only at the highest dose tested in the presence of severe maternal toxicity, including a high rate of mortality.

For chronic dietary exposure, the NOAEL of 15 mg/kg/day from the rat chronic toxicity/carcino-genicity study was selected, based on increased epithelial hyperplasia and thickening of the limiting ridge of the stomach in both sexes at the LOAEL of 150 mg/kg/day.  The study was selected because it was of the appropriate route and duration.  This histological finding was considered to be the result of direct irritation of the stomach by the test material, and it provided the most sensitive NOAEL for this risk assessment scenario.
  
For incidental oral short-term exposure, the maternal toxicity NOAEL of 75 mg/kg/day from the rat developmental toxicity study was selected based on mortality, decreased maternal body weight gain, and decreased food consumption at the LOAEL of 250 mg/kg/day.  This study was selected because it was of the appropriate duration and route, and it provided the most sensitive NOAEL.

For short- and intermediate-term dermal exposure, an appropriate endpoint was not identified.  No systemic toxicity was observed in a 21-day rabbit dermal study which tested up to the limit dose of 1000 mg/kg/day.  Developmental toxicity in the rabbit was only seen in the presence of significant maternal toxicity (maternal/developmental NOAEL = 250 mg/kg/day), and in the rat developmental study was not observed up to a maternally toxic dose (250 mg/kg/day).  In the rat reproduction study, fetal body and liver weight effects were seen at doses causing decreased maternal body weight.  Therefore, no pre- and/or postnatal toxicity would be expected at dermal doses up to and including the limit dose. 

A 28-day inhalation toxicity study is not available or required; therefore, oral studies were considered for use with route-to-route extrapolation for inhalation exposure assessment.  For short-term inhalation exposure, the maternal toxicity NOAEL of 75 mg/kg/day from the rat developmental toxicity study was selected based on mortality, decreased maternal body weight gain, and decreased food consumption at the LOAEL of 250 mg/kg/day.  This study was selected because it was of the appropriate duration and route, and it provided the most sensitive NOAEL.  This endpoint is protective of pre- and/or postnatal toxicity because developmental toxicity in the rabbit was only seen in the presence of significant maternal toxicity (maternal/developmental NOAEL = 250 mg/kg/day), and developmental toxicity in the rat was not observed up to a maternally toxic dose.

For intermediate-term inhalation exposure, the NOAEL of 15 mg/kg/day from the rat dietary chronic toxicity/carcinogenicity study was selected based on increased epithelial hyperplasia and thickening of the limiting ridge of the stomach in both sexes at the LOAEL of 150 mg/kg/day.  Although it is of chronic duration, it was selected to be protective of gastric irritation that might result from oral exposure of intermediate duration because it was observed at the interim sacrifices (6 and 12-month) in some animals.  As such, it is considered to be a conservative endpoint for this exposure scenario.

4.5.2	Recommendation for Combining Routes of Exposures for Risk Assessment

HED has considered oral, dermal, and inhalation routes of exposure in its assessment of clopyralid.  It is appropriate to combine routes of exposure when such exposures are expected to co-occur and result in the same toxicological effects.  For aggregate assessments, adults are only exposed via the inhalation and oral (food + water) routes, and these exposures should be combined and compared to the short-term inhalation endpoint and dose.  For children, the only relevant exposures consist of postapplication oral exposure to residues on lawns and oral dietary (food + water) exposure.  These exposures should be combined and compared to the short-term incidental oral endpoint and dose.  For occupational workers, only inhalation exposure and risk are being assessed.

4.5.3	Cancer Classification and Risk Assessment Recommendation

In accordance with the EPA's Final Guidelines for Carcinogen Risk Assessment (March, 2005), clopyralid is classified as "not likely to be carcinogenic to humans."  There was no evidence of treatment-related increases in tumor incidence in the 2-year rat and mouse dietary studies.  Both studies included a high dose that exceeded the limit dose.  Genotoxicity studies were negative.  

4.5.4	Summary of Points of Departure and Toxicity Endpoints Used in Human Risk Assessment

Table 4.5.4.1.  Toxicological Doses and Endpoints for Clopyralid for Use in Dietary and Residential Human Health Risk Assessments.
                                   Exposure/
                                   Scenario
                              Point of Departure
                        Uncertainty/FQPA Safety Factors
                     Level of Concern for Risk Assessment
                        Study and Toxicological Effects
Acute Dietary (All populations including infants and children) 
An appropriate endpoint for a single exposure was not identified.
Chronic Dietary
(All populations including infants and children)
                              NOAEL= 15 mg/kg/day
                                   UFA= 10X
                                   UFH= 10X
                                   SFFQPA=1
                              cRfD=0.15 mg/kg/day
                                       
                              cPAD=0.15 mg/kg/day
2-Year Combined Chronic Toxicity/Carcinogenicity (oral)  -  rat
LOAEL = 150 mg/kg/day, based on increased epithelial hyperplasia and thickening of the limiting ridge of the stomach in both sexes.
Incidental Oral, Short-term (1-30 days)

                              NOAEL= 75 mg/kg/day
                                   UFA= 10X
                                   UFH= 10X
                                   SFFQPA=1
                         Residential LOC for MOE= 100
                                       
Developmental Toxicity (oral)  -  rat
Maternal LOAEL = 250 mg/kg/day, based on decreased body weight gain and food consumption during GD 6-9.
Dermal, Short-term
(1-30 days) 
No dermal or systemic toxicity was observed at the limit dose (1000 mg/kg/day) in a rabbit 21-day dermal toxicity study and there are no developmental or reproductive concerns.
Inhalation, Short-term
(1-30 days)
Oral study
NOAEL = 75 mg/kg/day
(inhalation toxicity assumed to be equivalent to toxicity via the oral route)
                                   UFA= 10X
                                   UFH= 10X
                                   SFFQPA=1
                         Residential LOC for MOE = 100
Developmental Toxicity (oral)  -  rat
Maternal LOAEL = 250 mg/kg/day, based on decreased body weight gain and food consumption during GD 6-9.
Inhalation Intermediate-term (1-6 months)

Oral study NOAEL=  15 mg/kg/day (inhalation toxicity assumed to be equivalent to toxicity via the oral route)
                                   UFA= 10X
                                   UFH= 10X
                                   SFFQPA=1
                         Residential LOC for MOE= 100
2-Year Combined Chronic Toxicity/Carcinogenicity (oral)  -  rat
LOAEL 150 mg/kg/day, based on increased epithelial hyperplasia and thickening of the limiting ridge of the stomach in both sexes.
Cancer (all routes)
 "Not likely to be carcinogenic to humans."  Cancer risk is not of concern.
Point of Departure (POD) = A data point or an estimated point that is derived from observed dose-response data and  used to mark the beginning of extrapolation to determine risk associated with lower environmentally relevant human exposures.  NOAEL = no observed adverse effect level.  LOAEL = lowest observed adverse effect level.  UF = uncertainty factor.  UFA = extrapolation from animal to human (interspecies).  UFH = potential variation in sensitivity among members of the human population (intraspecies).  SFFQPA = FQPA Safety Factor.  PAD = population adjusted dose (a = acute, c = chronic).  RfD = reference dose.  MOE = margin of exposure.  LOC = level of concern.  

Table 4.5.4.2.  Summary of Toxicological Doses and Endpoints for Clopyralid for Use in Occupational Human Health Risk Assessments.
                                   Exposure/
                                   Scenario
                              Point of Departure
                              Uncertainty Factors
                     Level of Concern for Risk Assessment
                        Study and Toxicological Effects
Dermal, Short- and Intermediate-term (1-30 days and 1-6 months, respectively)
No dermal or systemic toxicity was observed at the limit dose (1000 mg/kg/day) in a 21-day dermal toxicity study and there are no developmental or reproductive concerns.
Inhalation, Short-term 
(1-30 days)
NOAEL = 75 mg/kg/day (inhalation toxicity assumed to be equivalent to toxicity via the oral route)
                                   UFA= 10X
                                   UFH= 10X
                                       
                           Occupational LOC for MOE
                                     = 100
Developmental Toxicity (oral)  -  rat

Maternal LOAEL = 250 mg/kg/day, based on decreased body weight gain and food consumption during GD 6-9.
Inhalation, Intermediate- term 
(1-6 months)
NOAEL = 15 mg/kg/day (inhalation toxicity assumed to be equivalent to toxicity via the oral route)
                                   UFA = 10X
                                   UFH = 10X
                                       
                           Occupational LOC for MOE
                                     = 100
2-Year Combined Chronic Toxicity/Carcinogenicity (oral)  -  rat

LOAEL = 150 mg/kg/day, based on increased epithelial hyperplasia and thickening of the limiting ridge of the stomach in both sexes.
Point of Departure (POD) = A data point or an estimated point that is derived from observed dose-response data and  used to mark the beginning of extrapolation to determine risk associated with lower environmentally relevant human exposures.  NOAEL = no observed adverse effect level.  LOAEL = lowest observed adverse effect level.  UF = uncertainty factor.  UFA = extrapolation from animal to human (interspecies).  UFH = potential variation in sensitivity among members of the human population (intraspecies).  MOE = margin of exposure.  LOC = level of concern.  N/A = not applicable.

5.0	Dietary Exposure and Risk Assessment 

5.1	Metabolite/Degradate Residue Profile

5.1.1	Summary of Plant and Animal Metabolism Studies

The nature of the residue in plants is adequately understood based on acceptable cabbage, grass, barley, and wheat metabolism studies.  In each of these studies, the major [14]C-residue was determined to be only parent compound.  HED concludes that the residue of concern in plants for purposes of this petition is clopyralid.  Although the available crop metabolism data all indicate that the parent compound is the only major residue, the data are from only two dissimilar crops (leafy vegetable and cereal grain).  Additional metabolism studies might be required in the future should the petitioner request the establishment of clopyralid tolerances for additional crops.
The nature of the residue in livestock commodities is adequately understood based on acceptable goat and poultry metabolism studies.  In livestock, the major residues are the parent clopyralid and its glycine conjugate (3,6-DCPA-glycine).

5.1.2	Summary of Environmental Degradation
      
In the environment, clopyralid has a low rate of soil sorption, is stable to photolysis and anaerobic metabolism, and is moderately stable to aerobic metabolism.  Because of its stability and high mobility, clopyralid is likely to persist in groundwater.  Based on the available information, OPP has determined that the residue of concern in drinking water is the parent compound only.

5.1.3	Comparison of Metabolic Pathways

Data depicting the metabolism of clopyralid in plants and animals have been submitted to the Agency.  In rats, there was no evidence of metabolism.  Only parent compound was identified in the rat urine and feces.  Clopyralid was essentially completely absorbed at both low and high doses (5 and 150 mg/kg/day, respectively).  Excretion was primarily via the urine.  Less than 4% of the excretion was via feces.  Radioactivity was not retained in tissues (<0.01% AD at 72 hrs postdosing).  Plant metabolism studies were performed on cabbage, grass, barley, and wheat.  In all of these studies, the major residue was determined to be parent compound.  Livestock metabolism studies were performed on goats and poultry.  In livestock, the major residues are the parent clopyralid and its glycine conjugate (3,6-DCPA-glycine).  Finally, parent clopyralid is also the predominant compound found in drinking water.  In effect, parent clopyralid is the predominant compound in rats, plants, livestock, and drinking water.  In livestock, glycine conjugates of clopyralid are also found.  As a result, the primary metabolites and degradates to which humans would be exposed are accounted for in the rat metabolism study.   

5.1.4	Residues of Concern Summary and Rationale

As stated above, the nature of the residue in plants is adequately understood for purposes of this petition based on acceptable cabbage, grass, barley, and wheat metabolism studies.  In each of these studies, the major residue was determined to be only parent compound.  HED concludes that the residue of concern in plants for purposes of this petition is clopyralid.  In livestock, the major residues are the parent clopyralid as well as its glycine conjugate (3,6-DCPA-glycine).  In the environment, clopyralid has a low rate of soil sorption, is stable to photolysis and anaerobic metabolism, and is moderately stable to aerobic metabolism.  Because of its stability and high mobility, clopyralid is likely to persist in groundwater.  Based on the available information, OPP has determined that the residue of concern in drinking water is the parent compound only.

Table 5.1.  Summary of Metabolites and Degradates to be included in the Risk Assessment and Tolerance Expression
Matrix
Residues included in Risk Assessment
Residues included in Tolerance Expression
Plants
Primary Crop
Clopyralid
Clopyralid

Rotational Crop
Clopyralid
Clopyralid
Livestock
Ruminant
Clopyralid + Glycine Conjugate
Clopyralid

Poultry
Clopyralid + Glycine Conjugate
Clopyralid
Drinking Water
Clopyralid
Not Applicable

5.2	Food Residue Profile

The only study that IR-4 submitted in support of the current tolerance petition was a combined field trial/processing study for apples.  For the other commodities, IR-4 is proposing that currently established tolerances be extended to the proposed commodities.  As a result, no new field trial data were submitted for the Brassica leafy greens subgroup, the Rapeseed subgroup, or teff.

The submitted apple field trial data are adequate and support the proposed use.  IR-4 performed an adequate number of trials and they were performed in the recommended EPA growing zones.  The application rate was 1x the maximum proposed rate, and the samples were collected at the proposed PHI.  Residues of clopyralid in/on each commodity were determined using an adequate GC/ECD method, and the duration and conditions of sample storage are supported by the available storage stability data.  The available field trial data support an LOQ tolerance of 0.05 ppm for apple fruit.  Table 5.2 provides a summary of the apple field trial data.

Table 5.2.  Summary of Residue Data from Crop Field Trials with Clopyralid
                                   Commodity
                                       
                             Total Applic. Rate[2]
                                   (lb ae/A)
                                      PHI
                                    (days)
                            Residue Levels (ppm)[1]
                                       
                                       
                                       
                                       n
                                     Min.
                                     Max.
                                    HAFT[3]
                                    Median
                                     Mean
                                   Std. Dev.
                                  Apple Fruit
                                 0.244 - 0.275
                                     28-30
                                      25
                                   <0.05
                                   < 0.05
                                   < 0.05
                                   < 0.05
                                   < 0.05
                                     NA[4]
1 These values represent residues of clopyralid
2 One foliar application of Stinger Herbicide at approximately 0.25 lb ae/A was made.
3 HAFT = Highest Average Field Trial.
[4]NA = Not applicable

In the apple processing study, no detectable residues were found in the samples of apple fruit, apple juice, or wet apple pomace.  Because of phytotoxicity concerns, IR-4 did not perform an exaggerated rate study.  No residues were found in the processed commodities; which indicates that if concentration did occur, it was not to a considerable extent.

5.3	Water Residue Profile

The estimated drinking water concentrations (EDWCs) used in the dietary risk assessment were provided by the Environmental Fate and Effects Division (EFED) in the following memorandum: "Tier I Drinking Water Assessment for Proposed New Use of Clopyralid on Apple, Leafy Brassica Greens Subgroup 5B, and Rapeseed Subgroup 20A, except Camelina (Gold of Pleasure)" (D391398, W. Shaughnessy, 12/19/2011) and incorporated directly into the dietary assessment.  Water residues were incorporated in the DEEM-FCID into the food categories "water, direct, all sources" and "water, indirect, all sources."  
 
A modeled upper-bound estimate of the clopyralid concentration in surface water (11.9 ppb) from the FQPA Index Reservoir Screening Tool (FIRST) Model was used for the assessment (Table 5.3).  This estimate is greater than that for groundwater from the Screening Concentration in Ground Water (SCIGROW) Model.  The same value was used in the previous dietary exposure assessment.  The drinking water models and their descriptions are available at the EPA internet site:  http://www.epa.gov/oppefed1/models/water/. 

Table 5.3.  Maximum Tier 1 Estimated Drinking Water Concentrations
 
                             Drinking Water Source
                              Model Used and Rate
                                  EDWC (ppb)
Groundwater
NAWQA (Oregon)
                                    0.2588
Surface Water (Acute)
FIRST (non-food crop, one application per year @ 0.5 lb ai/A)
                                      45
Surface Water (Chronic)
FIRST (non-food crop, one application per year @ 0.5 lb ai/A)
                                     11.9

5.4	Dietary Risk Assessment

5.4.1	Description of Residue Data Used in Dietary Assessment

There is no acute dietary endpoint for clopyralid.  As a result, an acute dietary exposure assessment was not conducted for the chemical.  A chronic dietary (food + drinking water) exposure and risk assessment was conducted for  clopyralid using the Dietary Exposure Evaluation Model DEEM-FCID(TM), Version 2.03 which uses food consumption data from the U.S. Department of Agriculture's Continuing Surveys of Food Intakes by Individuals (CSFII) from 1994-1996 and 1998.  The assessment is highly conservative with regard to protecting human health.  The assessment is based on tolerance-level residues for all commodities.  DEEM Version 7.81 default processing factors were used for all processed commodities for which they were available.  Modeled estimates of clopyralid residues in drinking water have been incorporated into the analyses.  Because such conservative assumptions were made in the assessment, the resulting exposure and risk estimates are considered to be conservative as well.  HED is confident that the chronic dietary exposure assessment significantly overestimates risk to the general U.S. population and its various population subgroups.
Clopyralid is classified as "not likely to be carcinogenic to humans."  As a result, cancer risk is not an issue for this chemical.

5.4.2	Percent Crop Treated Used in Dietary Assessment

The chronic dietary exposure assessment was based on the assumption that 100% of all commodities with clopyralid tolerances will be treated.

5.4.3	Acute Dietary Risk Assessment

An acute dietary endpoint was not selected for clopyralid.  As a result, an acute dietary exposure assessment was not performed.

5.4.4	Chronic Dietary Risk Assessment

Chronic risk estimates are below HED's level of concern for the general U.S. population and all population subgroups.  The U.S. population uses 9.3% of the cPAD.  The population subgroup Children 1-2 years old has the highest estimated dietary exposure to clopyralid.  This subgroup uses 25% of the cPAD.  Generally, HED is concerned about dietary risk when the exposure estimate exceeds 100% of the PAD.  The combined dietary risk from exposure to residues of clopyralid in food and drinking water are not of concern for the general U.S. population or any of the population subgroups.  The chronic dietary risk estimates are given in Table 5.4.6.

5.4.5	Cancer Dietary Risk Assessment

Clopyralid is classified as "not likely to be carcinogenic to humans."  As a result, cancer risk is not an issue for clopyralid.

5.4.6	Summary Table

 
 Table 5.4.6.  Summary of the Combined Dietary (Food + Drinking Water) Exposure and Risk Estimates
         for Clopyralid
 
 Population Subgroup
                                     Acute
                                    Chronic
                                     Cancer
 
                          Dietary Exposure (mg/kg/day)
                                     % aPAD
                                Dietary Exposure
                                  (mg/kg/day)
                                     % cPAD
                                Dietary Exposure
                                  (mg/kg/day)
                                      Risk
 General U.S. Population
                                      NA

                                      NA
                                       
                                       
                                       
                                       
                                       
                                       
0.013895
9.3
                                      N/A
                                        
                                        
                                        
                                      N/A
                                        
                                        
                                        
 All Infants (< 1 year old)
                                       
                                       
0.013726
9.2
 
 
 Children 1-2 years old*
                                       
                                       
0.037039
25
 
 
 Children 3-5 years old
                                       
                                       
0.033869
23
 
 
 Children 6-12 years old
                                       
                                       
0.022590
15
 
 
 Youth 13-19 years old
                                       
                                       
0.013383
8.9
 
 
 Adults 20-49 years old
                                       
                                       
0.010847
7.2
 
 
 Adults 50+ years old
                                       
                                       
0.009407
6.3
 
 
 Females 13-49 years old
                                       
                                       
0.010170
6.8
 
 
 *The most highly exposed population subgroup
 
 6.0 Residential (Non-Occupational) Exposure/Risk Characterization
 
No new residential uses for clopyralid are being proposed at this time.  However, for the purpose of performing an aggregate human health risk assessment, the previous residential exposure and risk estimates (D270507, S. Wang, 9/26/2007) were updated in accordance with the Revised Standard Operating Procedures for Residential Exposure (Residential SOPs, 2012).
Several clopyralid formulations are registered for weed control on residential lawns and/or professionally maintained turf areas.  HED previously reviewed two clopyralid formulations for residential exposures:  Lawn Fertilizer Plus Confront[(R)] Weed Control (EPA Reg. No. 62719-263), a granule plus fertilizer mix containing 0.18 % clopyralid (0.12 % ae) and Lontrel[(R)] Turf and Ornamental (EPA Reg. No. 62719-305), an EC formulation containing 40.9% clopyralid (or 3.0 lb ae/gal).  The granule has an application rate of 15.55 lbs of product per 4,500 sq. ft. (0.19 lb ae/A) and the EC has a maximum single application rate of 1(1/3) pt./A (0.5 lb ae/A) on turf.
 
6.1	Residential Handler Exposure and Risk

Based on the use pattern on home lawns, homeowners would be exposed via dermal and inhalation routes for a short-term duration only.  A quantitative short-term dermal residential handler exposure assessment was not conducted because of the lack of toxicity via the dermal route.  The estimated short-term inhalation handler MOEs ranged from 340,000 to 24,000,000.  All residential handler scenarios resulted in estimated MOEs greater than 100, with no risks of concern (Table 6.1).

Table 6.1.  Summary of Residential Handler Exposure and Risk Estimates for Clopyralid[1]
                                   Exposure 
                                   Scenario 
                             Application Rate [2] 
                     Area Treated or Gallons Used/Day) [3]
                                   Unit Exp.
                                (mg/lb ae) [3]
                             Short-term Inhalation
                                       
                                       
                                       
                                       
                                     Dose
                               (mg/kg/day) [4] 
                                    MOE [5]
Granule: Applied with push-type spreader
                                    0.19 lb
                                     ae/A
                                     0.5 A
                                    0.0026
                                  3.1x10[-6]
                                  24,000,000
EC: Mixing and applying spray with hose-end sprayer
                                      0.5
                                    lb ae/A
                                     0.5 A
                                     0.022
                                  6.9x10[-5]
                                   1,100,000
EC: Mixing and applying spray with back-pack sprayer
                                     0.025
                                   lb ae/gal
                                  5 Gallons 
                                     0.14
                                  2.2x10[-4]
                                    340,000
EC: Mixing and applying with manually pressurized handwand sprayer
                                     0.025
                                   lb ae/gal
                                  5 Gallons 
                                     0.018
                                  2.8x10[-5]
                                   2,700,000
1.  The previous estimate (S. Wang, D270507, 9/26/2007) was recalculated using unit exposures and area treated from the revised Residential SOP (2012).
2.  Application rate is expressed either in lb ae/A or in lb ae/gal.  The EC formulation (Lontrel Turf and Ornamental, (EPA Reg. No. 62719-305) recommends a minimum spray volume of 20 gal/A.  Therefore, for back-pack and handwand sprayers, the application rate was calculated in lb ae/gal (0.5 lb ae/A/20 gal=0.025 lb ae/gal).
3.  Area treated/A or spray vol. used/day assumptions are from the Lawn and Turf, Residential SOP (2012).
4.  Inhalation Dose (mg/kg/day) = [Appl. Rate (lb ae/A or lb ae/gal) * Area Treated/day (acres or spray volume
     * Inhal. Unit Exp. (mg/lb ae) * Inhalation Absorption (100%)] / body wt (80 kg).
5. Short-term Inhalation MOE = Short-term NOAEL (75 mg/kg/day) / Inhalation Dose (mg/kg/day).

6.2	Residential Post-application Exposure

The only short-term residential post-application exposure quantitatively assessed was for children playing on treated lawns, and in the absence of a dermal endpoint, only incidental oral exposure was included in the assessment.

There is a potential for post-application inhalation exposure to both adults and children following applications to lawns.  However, based on the Agency's current practices, a quantitative residential postapplication inhalation exposure assessment was not performed for clopyralid primarily because it has low inhalation toxicity and is applied as a soil directed spray to control broadleaf weeds.  However, volatilization of pesticides may be a potential source of postapplication inhalation exposure to individuals nearby to agricultural pesticide applications.  The Agency sought expert advice and input on issues related to volatilization of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel (SAP) in December 2009.  The Agency received the SAP's final report on March 2, 2010 (http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html).  The Agency is in the process of evaluating the SAP report and may, as appropriate, develop policies and procedures to identify the need for and, subsequently, the way to incorporate postapplication inhalation exposure into the Agency's risk assessments.  If new policies or procedures are put into place, the Agency may revisit the need for a quantitative postapplication inhalation exposure assessment for clopyralid.

Provided in Table 6.2, below, are risk estimates associated with incidental oral post-application exposure (i.e., hand to mouth, object to mouth, and soil and granule ingestion) for children following use of clopyralid granules and liquids on recreational and home lawns.  All MOEs range from 10,000 to 4,600,000, and are not of concern.

Table: 6.2.  Summary of Children's Post-application Exposure and Risk Estimates for Clopyralid.[1]
                               Formulation Type
                                   Exposure 
                                   Scenario 
                               Application Rate
                                    lb/AE/A
                          Short-term incidental oral
                                       
                                       
                                       
                                     Dose
                                (mg/kg/day) [2]
                                    MOE [3]
                                      EC
Hand-to-mouth
                                      0.5
                                    0.00745
                                    10,000
                                       
Objects-to-mouth
                                      0.5
                                    0.00023
                                    330,000
                                       
Soil ingestion  
                                      0.5
                                   0.000016
                                   4,600,000
                                    Granule
Hand-to-mouth
                                     0.19
                                    0.00028
                                    270,000
                                       
Objects-to-mouth
                                     0.19
                                    0.00009
                                    860,000
                                       
Granule ingestion (episodic)
                                       -
                                      - 
                              Not applicable [4]
1.  Revised estimates based on new Residential SOP for Exposure (2012).  Original estimates: D270507, S. Wang, 9/26/2007
2.  Oral doses were calculated based on new Residential SOP for Exposure (2012).
3.  Short-term incidental oral MOE = NOAEL 75 (mg/kg/day) / oral dose (mg/kg/day).
4.  Granule ingestion is viewed as an acute oral exposure.  As there is no acute dietary endpoint for clopyralid, exposure from granule ingestion was not assessed.

 

6.3      Combined Residential Risk Estimates

HED believes that combining children's post-application exposures, such as hand-to-mouth, object-to-mouth, and soil and granule ingestion resulting from EC and granule formulations of clopyralid on home lawns, would be overly conservative.  Although these exposures might occur simultaneously based on the use pattern of the pesticide and the behavior associated with the exposed population, the inputs used in calculating the risk estimates are conservative, and combining these conservative exposure and risk estimates would result in an unrealistically high estimate of exposure and risk.  In the case of clopyralid on turf, the scenario with the highest oral exposure for children (hand-to-mouth, MOE=10,000) is considered to be protective of all children's post-application exposure and risk, and should be used in the aggregate exposure and risk calculations.
 
6.4	Spray Drift

Spray drift is always a potential source of exposure to residents in close proximity to spraying operations.  This is particularly the case with aerial application, but, to a lesser extent, could also be a potential source of exposure from the ground application method employed for clopyralid.  The Agency has been working with the Spray Drift Task Force, EPA Regional Offices, State Lead Agencies for pesticide regulation, and other parties to develop the best spray drift management practices (see the Agency's Spray Drift website for more information at http://www.epa.gov/opp00001/factsheets/spraydrift.htm).  On a chemical by chemical basis, the Agency is now requiring interim mitigation measures for aerial applications that must be placed on product labels/labeling.  The Agency has completed its evaluation of the new database submitted by the Spray Drift Task Force, a membership of U.S. pesticide registrants, and is developing a policy on how to appropriately apply the data and the AgDRIFT computer model to its risk assessments for pesticides applied by air, orchard airblast, and ground hydraulic methods.  After the policy is in place, the Agency may impose further refinements in spray drift management practices to reduce off-target drift with specific products with significant risks associated with drift.

 7.0 Aggregate Exposure/Risk Characterization
In accordance with the FQPA, HED must consider and aggregate (add) pesticide exposures and risk estimates from three major sources:  food, drinking water, and residential exposures.  In an aggregate assessment, exposures from relevant sources are added together and compared to quantitative estimates of hazard (e.g., a NOAEL or PAD), or the risk estimates themselves can be aggregated.  When aggregating exposures and risks from various sources, HED considers both the route and duration of exposure.

7.1	Acute Aggregate Risk Estimates

Acute aggregate risk results from exposure to residues in food and drinking water alone.  An acute dietary endpoint was not selected for clopyralid.  As a result, an acute aggregate risk assessment was not performed.

7.2 Short-Term Aggregate Risk Estimates

For a short-term aggregate risk assessment, exposures from the oral, dermal, and inhalation routes need to be added.  A dermal endpoint was not selected for clopyralid; as a result, only exposures from the oral and inhalation routes need to be aggregated.  The incidental oral and inhalation endpoints were selected from the same study:  the rat developmental toxicity study.  The toxicological effects were decreased body weight gain and food consumption during gestation days 6 through 9.  The LOC for short-term aggregate risk is an MOE of 100.

Adults are exposed to clopyralid through the residential handler inhalation route of exposure; however, they are not exposed through the incidental oral route.  As a result, the residential handler inhalation exposure estimate only needs to be aggregated with the chronic dietary exposure estimate, which serves as a background exposure level.  As the oral and inhalation endpoints are the same, the additive dose approach can be used for aggregating adult short-term exposures.  The adult population subgroup with the highest exposure estimate is Adults 20-49; however, the general U.S. population has a higher dietary exposure estimate.  As a result, the dietary exposure estimate for the general U.S. population was used to determine aggregate risk.  The residential exposure estimate that resulted in the lowest MOE was that for mixing/loading/applying sprays with a backpack sprayer, so exposure from this scenario was combined with exposure from food and water.  The resulting aggregate exposure estimate yields an MOE of 5,300, which exceeds the LOC of 100 and is not of concern. 

Children are exposed to clopyralid through the incidental oral route of exposure.  The incidental oral exposure estimate was aggregated with the chronic dietary exposure estimate, which serves as a background exposure level.  As the oral route is the only route of exposure, the additive dose approach can be used for aggregating children's short-term exposures.  The population subgroup with the highest exposure estimate is Children 1-2, so this exposure was combined with the oral hand-to-mouth exposure estimate.  The resulting aggregate risk estimate is an MOE of 1,700, which exceeds the LOC of 100 and is not of concern. 

The aggregate risk estimates for adults and children are given in Table 7.2.  As stated in the two preceding paragraphs, the MOEs given in the table are worst-case scenarios because the short-term MOEs for any other population subgroups would be higher than those given in Table 7.2.  In effect, short-term aggregate risk estimates are not of concern for any population subgroup.
 
 Table 7.2.  Residential Short-Term Aggregate Risk Calculations
                                        
                                        
                                   Population
                              Short-Term Scenario
                                        
                                        
                                     NOAEL
                                   mg/kg/day
                                        
                                        
                                     LOC[1]
                   Average Food and Water Exposure mg/kg/day
                   Residential Inhalation Exposure mg/kg/day
                        Hand-to-Mouth Exposure mg/kg/day
                          Total Exposure[2] mg/kg/day
                Aggregate MOE (food, water, and residential)[3]
 Children 1-2
                                       75
                                      100
                                    0.037039
                                       NA
                                    0.00745
                                    0.044489
                                     1,700
 U.S. Population
                                       75
                                      100
                                    0.013895
                                    0.000218
                                       NA
                                    0.010916
                                     5,300
1.  An UF of 100x was applied to account for interspecies extrapolation (10x) and intraspecies variation (10x).  No additional uncertainty factors/safety factors are required.
2.  Total Exposure = Avg Food & Water Exposure + Residential Exposure
3.  Aggregate MOE = [NOAEL (75 mg/kg/day)/ (Avg Food & Water Exposure + Residential Exposure)]
87.2 Intermediate-Term Aggregate Risk Estimates

There are no residential uses for clopyralid that result in intermediate-term exposures.  As a result, no intermediate-term aggregate risk assessments were performed.

7.4	Chronic Aggregate Risk Estimates

There are no residential scenarios that result in long-term exposure.  As a result, the chronic aggregate risk assessment includes long-term exposure to residues in food and drinking water only.  The chronic dietary exposure analysis included both food and drinking water and, therefore, the chronic aggregate risk assessment is equivalent to the chronic dietary risk assessment discussed in Section 5.4.4, above.  All risk estimates are not of concern.

7.5	Cancer Aggregate Risk Estimates

Clopyralid is classified as "not likely to be carcinogenic to humans."  As a result, cancer risk is not an issue for the chemical.

 6.0 Cumulative Exposure/Risk Characterization
Unlike other pesticides for which EPA has followed a cumulative risk approach based on a common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as to clopyralid and any other substances, and clopyralid does not appear to produce a toxic metabolite produced by other substances.  For the purposes of this risk assessment, therefore, EPA has not assumed that clopyralid has 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/.

 7.0 Occupational Exposure/Risk Characterization
9.1	Short-/Intermediate-Term Handler Risk

Occupational Handlers

The proposed use pattern for apples is expected to result in short-term (1-30 days) exposure for most handlers.  However, as commercial applicators might apply Stinger(R) Herbicide at several locations during the crop season, intermediate-term (1-6 months) handler exposure could occur, and therefore an intermediate-term assessment was also conducted.

The label amendment to expand uses on individual crops to entire crop subgroups are based on registered use patterns.  The proposed use pattern for the Brassica leafy greens subgroup is the same as the registered use pattern on mustard greens, and the proposed use pattern for the Rapeseed subgroup is the same as the registered use pattern for canola, crambe, and rapeseed.  Similarly the request to register the use of clopyralid on teff is based on the registered use pattern for wheat.  Because these actions are being proposed without changes to the registered use patterns, separate occupational exposure assessments are not required.

Potential Exposure Scenarios:  Exposure scenarios describe the handler activities (mixer, loader and applicator) and type of application equipment.  Based on the proposed use pattern, the following exposure scenarios were identified:

::	mixing of EC formulation and loading diluted spray in groundboom sprayer
::	applying the spray using groundboom equipment
::	mixing, loading and applying the EC formulation using a back-pack sprayer for spot treatment.

The registrant has not submitted a chemical-specific exposure study to select unit exposures required for estimating handler exposure.  HED's policy is to use the best available data to assess handler exposure.  Sources of generic handler data, used as surrogate data in the absence of chemical-specific data, include the PHED Version 1.1, AHETF, Outdoor Residential Exposure Task Force (ORETF) databases, or other registrant-submitted occupational exposure studies.  Some of these data are proprietary (e.g., AHETF data), and are subject to the data protection provisions of FIFRA.  The standard values recommended for use in predicting handler exposure that are used in this assessment, known as "unit exposures," are outlined in the "Occupational Pesticide Handler Unit Exposure Surrogate Reference Table" (http://www.epa.gov/opp00001/science/handler-exposure-table.pdf), which, along with additional information on HED policy on use of surrogate data, including descriptions of the various sources, can be found at http://www.epa.gov/pesticides/science/handler-exposure-data.html.

Other inputs from ExpoSAC's Policy No. 9.1 (Standard Values of Daily Acres Treated) were used to estimate handler exposure.  Regardless of what the proposed label stipulates for PPE, HED typically conducts an initial assessment at the baseline level of personal protection consisting of a long-sleeve shirt, long pants, shoes and socks (no gloves and no respirator).  Additional PPE and mitigation measures, such as gloves, respirators, engineering, and administrative controls are added, if required, to obtain a risk level that does not exceed HED's LOC. 

Table 9.1 summarizes the short- and intermediate-term inhalation risk estimates for handlers resulting from the proposed use of Stinger[(R)] EC Herbicide on apples applied as broadcast and spot treatments.  No dermal endpoint and dose were selected for clopyralid because of the lack of dermal toxicity and, therefore, there is no risk associated with exposure via the dermal route.  At baseline PPE, the short-term (MOE >= 880,000) and intermediate-term (MOE >= 180,000) inhalation risk estimates are significantly above HED's LOC of an MOE of 100, and are not of concern.

 Table 9.1.  Occupational Handler Inhalation Exposure and Risk Estimates from Applying Clopyralid in Apple Orchards.
                               Handler Scenario
                              Used for Apple [1]
                                  Application
                                   Rate [2]
                                 Area Treated
                                  or Gallons
                                 Used/day [3]
                                     Risk
                             Mitigation Level [4]
                                  Inhalation
                    Unit Exp.              (ug/lb ae) [5]
                               Inhalation Dose 
                                (mg/kg/day) [6]
                         Short- term        Inhalation
                                    MOE [7]
                                 Interm.-term
                                  Inhalation
                                    MOE [8]
Mixing/Loading Liquids for Groundboom (AHETF)
                                 0.25 lb ae/A
                                   80 acres
                                   Baseline
                                     0.219
                                    5.5E-5
                                   1,400,000
                                    270,000
Applying by Groundboom (AHETF) 
                                 0.25 lb ae/A
                                   80 acres
                                   Baseline
                                     0.34
                                    8.5E-5
                                    880,000
                                    180,000
Mixing/Loading/Applying by backpack Sprayer (MRID 44339801) (ground-directed - orchards)
                               0.025 lb ae/gal)
                                    40 gals
                                   Baseline
                                     2.58
                                    3.2E-5
                                   2,300,000
                                    470,000
1.  Occupational Pesticide Handler Unit Exposure Surrogate Reference Table used for each scenario is indicated in parenthesis.
2.  The parent label (62719-73 recommends a minimum spray volume of 10 gal/A for ground application and therefore, for back-pack sprayer, application rate  
  was calculated as 0.25 lb ae/A/10 gal/A = 0.025 lb ae/gal.   
3.  Area treated per day assumptions are from ExpoSAC (SOP No. 9.1).  
4.  Baseline PPE includes long-sleeved shirt, long pants, shoes and socks, and no respirator. 
5.  From http://www.epa.gov/pesticides/science/handler-exposure-data.html
6.  Inhalation Dose (mg/kg/day) = [Appl. Rate (lb ae/A or lb ae/gal) * Area Treated/day (acres or spray volume) * Inhal. Unit Exp. (ug/lb ae/1000) * Inhalation Absorption (100%)] / Body Wt (80 kg). 
7.  Short-term Inhalation MOE = Short-term NOAEL (75 mg/kg/day) / Inhalation Dose (mg/kg/day).
8.  Intermediate-term Inhalation MOE = intermediate-term NOAEL (15 mg/kg/day) / Inhalation Dose (mg/kg/day).

9.2	Occupational/Commercial Post-application Risk 

Post-application workers can be exposed to residues of clopyralid through dermal and inhalation routes when they enter treated areas to perform post-application activities, such as thinning, irrigation, scouting, etc.  As there is no systemic toxicity associated with dermal exposure to clopyralid, a dermal post-application exposure assessment was not conducted, and there is no risk associated with post-application exposure via the dermal route. 

9.2.1	Post-application Inhalation Exposure

Based on the Agency's current practices, a quantitative post-application inhalation exposure assessment is not being performed for clopyralid at this time primarily because of the low acute inhalation toxicity (Toxicity Category IV) of the end-use product formulation (M. Hashim, D291712, 10/16/2003), low vapor pressure, and the low proposed use rate (0.25 lb ae/A).  However, there are multiple potential sources of post-application inhalation exposure to individuals performing post-application activities in previously treated fields.  These potential sources include volatilization of pesticides and re-suspension of dusts and/or particulates that contain pesticides.  The Agency sought expert advice and input on issues related to volatilization of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel (SAP) in December 2009, and received the SAP's final report on March 2, 2010 (http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html).  The Agency is in the process of evaluating the SAP report as well as available post-application inhalation exposure data generated by the Agricultural Reentry Task Force and may, as appropriate, develop policies and procedures, to identify the need for and, subsequently, the way to incorporate occupational post-application inhalation exposure into the Agency's risk assessments.  If new policies or procedures are put into place, the Agency may revisit the need for a quantitative occupational post-application inhalation exposure assessment for clopyralid.

Although a quantitative occupational post-application inhalation exposure assessment was not performed, an inhalation exposure assessment was performed for occupational/commercial handlers.  Handler exposure resulting from application of pesticides to crops is likely to result in higher exposure than exposure to workers if they enter treated fields.  Therefore, it is expected that the handler inhalation exposure estimates are protective of most occupational post-application inhalation exposure scenarios.

The registrant has provided supplemental labels for Stinger[(R)] Herbicide (EPA Reg. No. 62719-73) with this submission.  The active ingredient in Stinger[(R)] is the monoethanolamine salt of clopyralid acid and has a 12-hour REI, which is appropriate.

10.0	References

D361316, M. Doherty, et al., 12/3/2009, Clopyralid  -  Human Health Risk Assessment to Evaluate New Uses on Swiss Chard, Bushberry Subgroup (13-07B), and Strawberry (Regional Restriction)

D391747, D. Dotson, 6/6/2012, Clopyralid.  Petition for the Section 3 Registration and the Establishment of Tolerances on Apples, Brassica Leafy Greens (Subgroup 5-B), Teff, and Rapeseed (Subgroup 20-A) Except Gold of Pleasure.  Summary of Analytical Chemistry and Residue Data

D399390, D. Dotson, 6/6/2012, Clopyralid Chronic Aggregate Dietary (Food and Drinking Water) Exposure and Risk Assessment for the Section 3 Registration Action on Apples, Teff, the Leafy Brassica Greens Subgroup (5-B), and the Rapeseed Subgroup (20-A) 

D391398, W. Shaughnessy, 12/19/2011, Tier I Drinking Water Assessment for Proposed New Use of Clopyralid on Apple, Leafy Brassica Greens Subgroup 5B, and Rapeseed Subgroup 20A, Except Camelina (Gold of Pleasure)

D391748, S. Oonnithan, 4/30/2012, Clopyralid: Occupational Exposure Assessment for a New Use on Apples; Expansion of Crop Group 5B; and Revised Residential Exposure Assessment for use on Turf.

 List of Appendices
 
Appendix A.  Clopyralid Toxicology Profile and Executive Summaries 
Appendix B.  Clopyralid Physical/Chemical Properties
 Appendix C.  Review of Human ResearchAppendix A:  Toxicology Profile and Executive Summaries

Appendix A.1.  Toxicology Data Requirements
The requirements (40 CFR 158.340) for food use for clopyralid are in the table below. Use of the new guideline numbers does not imply that the new (1998) guideline protocols were used.
                                     Study
                                   Technical

                                   Required
                                   Satisfied
870.1100    Acute Oral Toxicity	
870.1200    Acute Dermal Toxicity	
870.1300    Acute Inhalation Toxicity	
870.2400    Primary Eye Irritation	
870.2500    Primary Dermal Irritation	
870.2600    Dermal Sensitization	
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
870.3100    Oral Subchronic (rodent)	
870.3150    Oral Subchronic (nonrodent)	
870.3200    21-Day Dermal	
870.3250    90-Day Dermal	
870.3465    28-Day Inhalation	
                                      yes
                                      yes
                                      yes
                                      no
                                     no[4]
                                      yes
                                     yes[1]
                                      yes
                                       -
                                       -
870.3700a  Developmental Toxicity (rodent)	
870.3700b  Developmental Toxicity (nonrodent)	
870.3800    Reproduction	
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
870.4100a  Chronic Toxicity (rodent)	
870.4100b  Chronic Toxicity (nonrodent)	
870.4200a  Oncogenicity (rat)	
870.4200b  Oncogenicity (mouse)	
870.4300    Chronic/Oncogenicity	
                                      yes
                                      yes
                                      yes
                                      yes
                                      yes
                                     yes[2]
                                      yes
                                     yes[2]
                                      yes
                                      yes
870.5100    Mutagenicity -- Gene Mutation - bacterial	
870.5300    Mutagenicity -- Gene Mutation - mammalian	
870.5xxx    Mutagenicity -- Structural Chromosomal Aberrations	
870.5xxx    Mutagenicity -- Other Genotoxic Effects	
                                      yes
                                      yes
                                      yes
                                      yes
                                     yes[3]
                                      yes
                                      yes
                                      yes
870.6100a  Acute Delayed Neurotoxicity (hen)	
870.6100b  90-Day Neurotoxicity (hen)	
870.6200a  Acute Neurotoxicity Screening Battery (rat)	
870.6200b  90-Day Neurotoxicity Screening Battery (rat)	
870.6300    Develop. Neurotoxicity	
                                      no
                                      no 
                                     no[4]
                                     no[4]
                                      no
                                       -
                                      - 
                                       -
                                       -
                                       -
870.7485    General Metabolism	
870.7600    Dermal Penetration	
870.7800    Immunotoxicity	
                                      yes
                                      no
                                      yes
                                      yes
                                       -
                                      yes
Special Studies for Ocular Effects
         Acute Oral (rat)	
         Subchronic Oral (rat)	
         Six-month Oral (dog)	
                                       
                                      no
                                      no
                                      no
                                       
                                       -
                                       -
                                       -
   1 Satisfied by 870.4100b, chronic dog
   2 Satisfied by 870.4300, rat combined chronic toxicity/carcinogenicity
   3 Satisfied by overall negative genotoxicity database including host-mediated assay of S. typhimurium and S.             cerevisia
   4     Requirement waived by HED HASPOC based on a weight of evidence consideration of hazard, exposure,     	physicochemical properties, and structurally-related chemicals.  
Appendix A.2.  Toxicity Profiles

Table A.2.1.  Acute Toxicity Profile for Clopyralid
                               Guideline Number
                                  Study Type
                                Classification
                                     MRID
                                    Number
                                    Results
                               Toxicity Category
                                   870.1100
Acute-oral-rat
                                   41641301
LD50 (M/F) >5,000 mg/kg 
                                      IV
                                   870.1200
Acute-dermal-rat
                                   41641302
LD50 (M/F) > 5000 mg/kg
                                      IV
                                   870.1300
Acute-inhalation-rat
                                   41848301
LC50 (M/F) > 1 mg/L
                                      III
                                   870.2400
Acute-eye irritation-rabbit
                                   41641304
Severe irritation at 7 days (corrosive)
                                       I
                                   870.2500
Acute-dermal irritation-rabbit
                                   41641305
Not an irritant
                                      IV
                                   870.2600
Skin sensitization - guinea pig
                                   41641306
Not a sensitizer
                                       -

Table A.2.2	Subchronic, Chronic and Other Toxicity Profile for Clopyralid
                                Guideline No. 
                                  Study Type
                    MRID No. (year)/ Classification /Doses
                                    Results
                                   870.3100
90-Day oral toxicity (rat)
An acceptable study is not available.  Requirement satisfied by combined chronic oral toxicity/carcinogenicity study in the rat (870.4300).
                                   870.3100
                                       
90-Day oral toxicity (mouse) 

00127276  (2003)
Acceptable/guideline
0, 200, 750, 2000 or 5000 mg/kg/day
NOAEL = 2000 mg/kg/day
LOAEL = 5000 mg/kg/day based on decreased body weight gain.
                                   870.3150
                                       
90-Day oral toxicity (dog)
An acceptable study is not available.  Requirement satisfied by chronic oral study in the dog (870.4100).
                                   870.3200
                                       
21-Day dermal toxicity (rabbit)
41790701 (1990)
Acceptable/guideline
0, 100, 500 or 1000 mg/kg/day
Systemic NOAEL = 1000 mg/kg/day (limit dose)
Systemic LOAEL = not established (>1000 mg/kg/day).
Local dermal NOAEL < 100 mg/kg/day (LDT)
Local dermal LOAEL = 100 mg/kg/day, based on epithelial hyperplasia at application site
                                   870.3250
                                       
90-Day dermal toxicity 
Study not required,
                                   870.3465
                                       
28- Day inhalation toxicity (rat)
 Study not required.
                                   870.3700a
                                       
Prenatal developmental in (rat)
00127279 (1981)
Acceptable/guideline
0, 15, 75 or 250 mg/kg/day

Maternal NOAEL = 75 mg/kg/day
LOAEL = 250 mg/kg/day based on mortality, decreased body weight gains and reduced food consumption.
Developmental NOAEL =  250 mg/kg/day (HDT)
LOAEL = not established (>250 mg/kg/day).
                                   870.3700b
                                       
Prenatal developmental in (rabbit)
41649801, -02 (1990)
Acceptable/guideline
0, 50, 110 or 250 mg/kg/day by gavage
Maternal NOAEL =  110 mg/kg/day
LOAEL = 250 mg/kg/day based on mortality, decreased body weight gains, reduced food consumption and lesions in the gastric mucosa.
Developmental NOAEL = 110 mg/kg/day
LOAEL = 250 mg/kg/day based on decreased fetal body weight and hydrocephalus.
                                   870.3800
                                       
Reproduction and fertility effects
(rat)
00138155 (1983)
Acceptable/guideline
0, 150, 500 or 1500 mg/kg/day in diet

Parental  NOAEL = 500 mg/kg/day
(M/F)
LOAEL = 1500 mg/kg/day(M/F), based on decreased body weights and body weight gain in F0 and  F1 males; body weights in F1 and F2 females

Reproductive NOAEL >=1500 mg/kg/day
LOAEL = not attained based on lack of effects on reproductive parameters (>1500 mg/kg/day)

Offspring  NOAEL = 500 mg/kg/day (M/F)
LOAEL = 1500 mg/kg/day (M/F), based on decreased Day 28 body weights in F1 male pups and increased relative liver weights of  F1a male and female pups and F1b male pups.
                                   870.4100a
                                       
Chronic toxicity
(rat)
Requirement satisfied by 870.4300.
                                   870.4100b
                                       
Chronic toxicity (dog)
00158256 (1984)
Acceptable/guideline
0, 100, 320 or 1000 mg/kg/day by capsule

NOAEL = 100 mg/kg/day
LOAEL = 320 mg/kg/day based on decreases in RBC parameters, increased liver weight (males) and vacuolated adrenal cortical cells (females).  Clinical chemistry changes (decreased serum albumin, globulin, protein) and skin lesions were observed at high dose.
                                   870.4200a
Carcinogenicity
(rat)
Requirement satisfied by 870.4300.
                                   870.4200b
                                       
24-month Carcinogenicity
(mouse)
00162393, 00162434 (1984)
Acceptable/guideline
0, 100, 500 or 2000 mg/kg/day in the diet (24 months)
NOAEL = 500 mg/kg/day
LOAEL = 150 mg/kg/day based on decreased body weight/weight gain and reduced food efficiency.

(no) evidence of carcinogenicity
                                   870.4300
                                       
Chronic toxicity/carcinogenicity (rat)
00162393, 00162434 (1986)
Acceptable/guideline
0, 15, 150 or 1500 mg/kg/day in the diet (104 weeks)
NOAEL = 15 mg/kg/day
LOAEL = 150 mg/kg/day based on gastric lesions (epithelial hyperplasia and thickening of the limiting ridge).  At 1500 mg/kg/day, decreased body weight gains and food consumption were also observed.

(no) evidence of carcinogenicity
                                 Gene Mutation
                                   870.5100
Study not submitted.  Not required due to lack of tumorigenicity in rat and mouse bioassays and negative findings in all other genotoxicity assays, including host-mediated assays in Salmonella and Saccharomyces.
                                 Gene Mutation
                                   870.5300
In Vitro and In Vivo  Host Mediated Assay  (Salmonella  strains TA 1530, G-46 and Saccharomyces strain D-3) (1973)
In vivo assays were conducted using mice
00057086 (1973)
Acceptable/guideline
In vitro testing:  without S9 activation at 5% w/v solution
In vivo testing:  0, 4, 40 or 400 mg/kg by gavage to 10 mice
Negative  -  no evidence of induced mutant colonies over background levels in Salmonella or Saccharomyces strains tested in either the in vitro or the in vivo assays.
                                 Cytogenetics
                                   870. 5385
In Vivo Micronucleus assay, Rat
00073638 (1973)
Acceptable/guideline
0, 4, 40 or 400 mg/kg for one day or for 5 days to male rats; sacrifice at 6, 24 or 48 hrs postdosing for all groups.
Negative  -  no evidence of an increase in the formation of chromosomal aberrations in bone marrow at any dose tested.  
                                 Other Effects
                                   870.5450
Dominant Lethal Assay in Rats
00059053, 00099100 (1973)

Acceptable/guideline

4, 40 or 400 mg/kg/day for 5 days to male rats prior to mating
Negative  -  no evidence of treatment-related resorptions.
                                 Other Effects
                                   870.5550
Unscheduled DNA Synthesis, Rat Hepatocytes
00156387 (1985), 41790702 (1990)
Acceptable/guideline
5x10[-5], 1.56x10[-4], 5x10[-4], 1.56x10[-3], 5x10[-3], 1.56x10[-2], 5x10[-2] M, incubated for 18-20 hrs
Negative  -  no evidence of increased unscheduled DNA synthesis in the initial or supplementary assays testing up to insoluble/toxic concentrations.
                                   870.6200a
                                       
Acute neurotoxicity screening battery (rat)
Study not required.
                                   870.6200b
                                       
Subchronic neurotoxicity screening battery (rat)
Study not required.
                                   870.6300
                                       
Developmental neurotoxicity
Study not required.
                                   870.7485
                                       
Metabolism and pharmacokinetics
(rat)
41790703 (1991)
Acceptable/guideline
5.0 and 50 mg/kg, single oral dose; 5.0 mg/kg, single IV dose and 5.0 mg/kg/day, repeated daily dose for 14 days
Clopyralid was rapidly and completely absorbed and eliminated with 95 to 115% of the administered dose recovered by 72 hr, most within 6-12 hrs postdosing.  Almost all radioactivity was eliminated via the urine irrespective of dose or route of administration (91 to 113% of AD), with <4% excreted in the feces.  Tissue retention was negligible (<0.01% AD).  There was essentially no metabolism of clopyralid:  only parent compound was identified.  No significant gender, dose or exposure route differences were identified.
                                   870.7600
Dermal penetration 
Study not available.
                                   870.7800
Immunotoxicity (rat)
48300001 (2011)
Acceptable/guideline
0, 158, 530, or 1062 mg/kg/day
Systemic NOAEL = 1062 mg/kg/day (limit dose)
Systemic LOAEL = not established (>1062 mg/kg/day)
Immunotoxicity NOAEL = 1062 mg/kg/day
Immunotoxicity LOAEL = not established (>1062 mg/kg/day)

Appendix A.3.  Hazard Identification and Endpoint Selection

A.3.1	Acute Reference Dose (aRfD)  -  All Populations (Including Females Age 13-49 and Infants and Children)

This risk assessment was not performed.  An appropriate endpoint for acute oral exposure was 
not identified.  Although hydrocephalus was observed, it occurred only in the presence of severe 
maternal toxicity, including a high rate of mortality (considered treatment-related in 8/29 females), and was therefore not selected for this exposure scenario.  

A.3.2	Chronic Reference Dose (cRfD)  -  All Populations (Including Females Age 13-49 and Infants and Children)

Study Selected:  Combined Chronic/Carcinogenicity - rat (OPPTS 870.4300)
MRID Nos.:   00162393, 00162434
Dose and Endpoint for Risk Assessment: NOAEL = 15 mg/kg/day, based on histopathology in the stomach (epithelial hyperplasia and thickening of the limiting ridge) at the LOAEL of 150 mg/kg/day: 
Comments on Study/Endpoint/Uncertainty Factors:  The 2-year rat chronic toxicity/carcinogenicity study with a NOAEL of 15 mg/kg/day is via an appropriate route of administration (diet) and is the lowest NOAEL for all chronic studies in the dog, rat, and mouse.  The limiting ridge is the structure between the forestomach (nonglandular) and glandular portions of the rodent stomach.  Although the limiting ridge is absent in dogs and primates, the histological effects are believed to be due to the irritating properties of the chemical and, therefore, may be of potential toxicity in humans.  The finding was observed in some interim sacrifice animals at 6 and 12 months, as well as at terminal (24-month) sacrifice.  The endpoint is considered conservative because only 1-2 animals/sex were affected at 6 months.  Stomach lesions were also observed in the developmental rabbit study and rat reproduction study.  The NOAEL is lower than all endpoints for developmental and reproductive effects and therefore protective of potential pre- and/or postnatal toxicity.  An UF of 100 was applied to account for inter-species extrapolation (10X) and intra-species variation (10X).  

	Chronic RfD =    15 mg/kg/day (NOAEL)   = 0.15 mg/kg/day
                         100  (UF)

A.3.3	Incidental Oral Exposure (Short-Term) 	
      
Study Selected:  Developmental Toxicity Study  -  rat (OPPTS 870.3700a) 
MRID No.:  00127279
Dose and Endpoint for  Risk Assessment:  NOAEL = 75 mg/kg/day, based on maternal mortality and decreased body weight gain and food consumption during days 6-9 of gestation at the LOAEL of 250 mg/kg/day.  
Comments on Study/Endpoint:  This endpoint is based on a study of an appropriate duration and route.  The selected dose is protective of potential prenatal toxicity because fetal effects were seen only at the maternal LOAEL, and of potential postnatal toxicity based on the offspring NOAEL of 500 mg/kg/day in the rat reproduction study.  An UF of 100 was applied to account for inter-species extrapolation (10X) and intra-species variation (10X).

A.3.4	Incidental Oral Exposure (Intermediate-Term) 	

Study Selected:  Combined Chronic/Carcinogenicity - rat (OPPTS 870.4300)
MRID Nos.:   00162393, 00162434
Dose and Endpoint for Risk Assessment: NOAEL = 15 mg/kg/day, based on histopathology in the stomach (epithelial hyperplasia, thickening of the limiting ridge) at the LOAEL of 150 mg/kg/day: 
Comments on Study/Endpoint/Uncertainty Factors:  This study was of an appropriate route and effects were observed by six months' exposure duration. An UF of 100 was applied to account for inter-species extrapolation (10X) and intra-species variation (10X).  

A.3.5	Dermal Absorption	

Dermal absorption data are not available for clopyralid; however, a 21-day dermal toxicity study was available and showed no systemic toxicity up to the limit dose of 1000 mg/kg/day (see below).

A.3.6	Dermal Exposure (Short- and Intermediate-Term)	

This risk assessment was not performed.  No systemic toxicity was observed in a rabbit 21-day dermal study up to the limit dose of 1000 mg/kg/day (MRID 41790701).  In the rabbit, the more sensitive species for developmental effects, fetal toxicity was observed only in the presence of severe maternal toxicity (decreased maternal body weight, clinical signs of toxicity and mortality).  Therefore, these findings were not observed following dermal exposure in the same species, developmental effects would not be expected at the limit dose.  The 21-day study indicates that dermal absorption is low.  Based on comparison of the two studies, risk from exposure via the dermal route is not a concern.

A.3.7	Inhalation Exposure (Short-Term)	

Study Selected:  Developmental toxicity in rat
MRID No.:  00127276
Dose and Endpoint for Risk Assessment:  Maternal NOAEL = 75 mg/kg/day based on mortality, decreased body weight gain and food consumption at the LOAEL of 250 mg/kg/day. 
Comments about the Study/Endpoint:  This endpoint is based on an oral study because no inhalation studies are available.  Therefore, an oral study is selected to estimate risk using a route-to-route extrapolation.  The rat developmental study and endpoint were selected because they are protective of pre- and/or postnatal effects, including hydrocephalus as observed in the rabbit developmental study at 250 mg/kg/day (maternal and developmental NOAEL = 110 mg/kg/day).  The observed effects are a result of short-term exposure.  Absorption via inhalation is assumed to be equivalent to absorption via the oral route, i.e., 100% inhalation absorption is assumed in risk assessment.  An UF of 100 was applied to account for inter-species extrapolation (10X) and intra-species variation (10X).  An additional 10x UFDB was not applied for lack of the inhalation study because an inhalation study is not required, and the oral study is considered protective based on low vapor pressure and high inhalation MOEs estimated using the oral endpoint.

A.3.8	Inhalation Exposure (Intermediate-Term)	

Study Selected:  Chronic toxicity/carcinogenicity in rats
MRID No.:  00162393, 00162434
Dose and Endpoint for Risk Assessment:  The NOAEL = 15 mg/kg/day, based on epithelial hyperplasia and thickening of the limiting ridge of the stomach in both sexes.
Comments about the Study/Endpoint:  No inhalation studies are available.  Therefore, an oral study was selected to estimate risk using route-to-route extrapolation.  The study and endpoint were selected because they were observed by six months' exposure and are protective of effects observed in all available studies, including maternal and developmental effects in the rabbit.  Absorption via inhalation is assumed to be equivalent to absorption via the oral route, i.e., 100% inhalation absorption is assumed in risk assessment.  An UF of 100 was applied to account for inter-species extrapolation (10X) and intra-species variation (10X).  An additional 10x UFDB was not applied for lack of the inhalation study because an inhalation study is not required and the oral study is considered to be protective based on low vapor pressure and high inhalation MOEs estimated using the oral endpoint.

Appendix A.4.  Executive Summaries

A.4.1	Subchronic Toxicity

	870.3100	90-Day Oral Toxicity - Rat

Satisfied by 870.4300 (Chronic Oral Toxicity/Carcinogenicity  -  Rat)

	870.3100	90-Day Oral Toxicity - Mouse

In a subchronic toxicity study (MRID #00127276) 3,6- dichloropicolinic acid (technical, 97% purity) was administered to groups of 10/sex/dose BSC3F1 mice at dietary levels of 0, 200, 750, 2000, or 5000 mg/kg body weight/day for approximately 13 weeks.

There was a statistically significant decrease in body weight in both sexes at 5000 mg/kg/day. Relative (to body) liver weight was significantly increased in both sexes at 5000 mg/kg/day. Males and females at 5000 mg/kg/day and females at 2000 mg/kg/day had centrilobular hepatocellular hypertrophy with altered tinctorial properties.  The increased liver weight and hepatocellular histopathology were considered reversible, adaptive effects resulting from the increased metabolic activity due to dietary intake of clopyralid.  

The LOAEL is 5000 mg/kg/day, based on decreased body weight in both sexes. The NOAEL is 2000 mg/kg/day.

This subchronic toxicity study is classified Acceptable/guideline and does satisfy the guideline requirement for a subchronic oral study (§870.3100) in the rodent (mouse).

	870.3150	90-Day Oral Toxicity - Dog

Satisfied by 870.4100b (Chronic Oral Toxicity  -  Dog)

	870.3200	21-Day Dermal Toxicity  -  Rat

In a 21-day repeated dose dermal toxicity study (MRID 41790701), groups of 5 male and 5 female New Zealand white rabbits were treated with Clopyralid (technical, 95.78%, Lot No. not given) at doses of 0, 100, 500, or 1000 mg/kg/day as a powder under moistened gauze. Animals were treated by dermal occlusion for 6 hours/day, 5 days/week for 3 weeks.

There were no treatment-related deaths or signs of systemic toxicity and no treatment-related effects on body weight, hematology, clinical chemistry, or organ weight. No evidence of skin irritation was observed in control rabbits; however, very slight erythema was observed on 1 mid- and 1 high-dose male and 1 mid-dose female at the end of the study. Treatment-related diffuse epidermal hyperplasia was observed on 1/5, 3/5, and 5/5 low-, mid- and high-dose males and 2/5, 1/5, and 5/5 low-, mid-, and high-dose females, respectively, at the end of the study. The effect was not observed in any control animals.  

The local dermal LOAEL was 100 mg/kg/day (LDT) based on diffuse epidermal hyperplasia on the skin of both males and females.  A dermal NOAEL was not identified (<100 mg/kg/day).

The systemic NOAEL is 1000 mg/kg/day based on a lack of biologically significant systemic toxicity. A systemic LOAEL was not identified (>1000 mg/kg/day).

This study is classified as Acceptable/Guideline and does satisfy the guideline requirements for a repeated-dose dermal study (§870.3200) in rabbits. Although a dermal NOAEL was not identified based on epithelial hyperplasia (1-5 animals affected) at all dose levels, no systemic toxicity was reported at any dose level.

	870.3465	28-Day Inhalation  -  Rat

Not required.

A.4.2	Prenatal Developmental Toxicity

	870.3700a Prenatal Developmental Toxicity Study - Rat

In a developmental toxicity study (MRID 00127279), 29-30 presumed pregnant Fischer 344 rats per group were administered Clopyralid (technical, 97.0%; Lot/Batch No. not provided) by gavage in cottonseed oil at doses of 0, 15, 75, and 250 mg/kg/day on gestation days (GD) 6-15, inclusive (Phase I). When a low number of malformations were observed at the highest dose tested in Phase I, additional control and high-dose groups (of 25 animals apiece) were evaluated later in Phase II. Controls were treated with cottonseed oil (vehicle). On GD 21, dams were sacrificed, maternal liver, kidney, and thymus weights were recorded, and all fetuses examined externally. Approximately one-half of each litter was processed for visceral examination, and all carcasses and the heads of the remaining one-half were processed for skeletal examination.

During Phase I, one rat in the 250 mg/kg/day group died on GD 11. Moistening of the hair of the perineal region, a thymus slightly decreased in size, and a gastrointestinal tract devoid of feed or fecal material were observed in this animal. During Phase II, two rats in the 250 mg/kg/day group died on GD 10. Both animals exhibited substantial weight loss and exudative material from the nares. Definitive diagnoses as to cause of death could not be made for any of these animals. No other treatment-related clinical signs of toxicity were observed in any other animals. Maternal necropsy was unremarkable.  In Phase I, absolute body weights of the high-dose dams were slightly decreased to 95-97% of I controls on GD 10, 16, and 21, and these differences were statistically significant (p <=0.05) on GD 10 and 16. Weight gain by the Phase I high-dose dams was significantly decreased (p <= 0.05) to 25-75% of the control group level during the treatment period. In Phase II, absolute body weights of the high-dose dams were statistically significantly decreased (p <= 0.05) to 94- 97% of controls on GD 10, 16, and 21. Weight gain by the Phase II high-dose dams was significantly decreased (p <= 0.05) to 42-74% of the control group level during the treatment period.  In both Phase I and II, animals of the 250 mg/kg/day group had significantly (p <=0.05) lower food consumption as compared with the controls during the treatment interval. No treatment- related differences in water consumption were observed between the treated and control groups.

The maternal toxicity LOAEL is 250 mg/kg/day, based on death, reduced body weight gains, and reduced food consumption, and the maternal toxicity NOAEL is 75 mg/kg/day.

There were no differences between the control group and the 15, 75, or 250 mg/kg/day groups during Phase I or Phase II for number of corpora lutea, number of implantation sites, live fetuses/dam, pre- and post-implantation losses, or fetal sex ratios. During Phase I, the mean fetal body weight in the 75 mg/kg/day group was slightly, but statistically significantly (p <=0.05), increased to 104% of control group level. No other statistically or biologically differences between treated and control animals were noted.  In Phase I, the overall incidence rates for liners containing fetuses with major external, visceral, and/or skeletal malformations in the 0, 15, 75, and 250 mg/kg/day groups were 0/29, 0/22, 0i25, and 2/26, respectively. In Phase II, the overall incidence rates for liners containing fetuses with major external, visceral, and/or skeletal malformations in the 0 and 250 mg/kg/day groups were 1/20 and 0/21.  No single malformation occurred at a statistically or biologically significant greater incidence in the treated groups, and the incidence of total major malformations was also not significantly increased for any of the treated groups as compared to controls.

The developmental toxicity NOAEL is 250 mg/kg/day.  A developmental toxicity LOAEL was not determined (>250 mg/kg/day).

This study is classified as Acceptable/Guideline and satisfies the requirements for a developmental toxicity study (§83-3a) in rats. Despite numerous deficiencies in the conduct of this study, an assessment of the developmental toxicity potential of the test article was possible.

	870.3700b Prenatal Developmental Toxicity Study - Rabbit

In a developmental toxicity study (MRID 41649801, 41649802), 26-34 presumed pregnant New Zealand White rabbits per group were administered Clopyralid (technical, 96.1-96.4% a.i., Lot No. AGR 233257) by gavage at doses of 0, 50, 110, and 250 mg/kg/day on gestation days (GD) 7-19, inclusive. The controls were given vehicle (corn oil) only for the same dosing period. On GD 28, all does were sacrificed, necropsied to assess gross pathology, and uteri and ovaries were removed. All fetuses were sexed, weighed, and examined for external malformations/variations prior to sacrifice. All of the fetuses were opened and checked viscerally then processed for skeletal examination.

Clinical signs of toxicity consisting of labored breathing, rales, shallow respiration, and/or coughing were observed in 11/29 does at 250 mg/kg/day. Eight of 13 deaths occurring at 250 mg/kg/day were considered treatment-related. Mean body weight gain was statistically significantly (p  0.05) decreased during the treatment period (GD 7-20) which correlates with a significant reduction in absolute body weight at GD 20 for 250 mg/kg/day animals. Histopathologic lesions of the gastric mucosa were observed in does (8/33) of the 250 mg/kg/day treatment group.

The maternal toxicity LOAEL is 250 mg/kg/day, based on clinical signs of toxicity, mortality, reduction in mean body weight, and lesions of the gastric mucosa during the treatment period.  The maternal toxicity NOAEL is 110 mg/kg/day.

A statistically significant (p<=0.05) reduction in fetal body weight (13.2%), observed at 250 mg/kg/day of Clopyralid, was considered treatment-related. Also at 250 mg/kg/day, 3/15 litters contained fetuses (total of eight) with hydrocephaly compared with 0/19 controls (n.s.).

The developmental toxicity LOAEL is 250 mg/kg/day, based on decreased fetal body weight and malformations.  The developmental NOAEL is 110 mg/kg/day.

This study is classified as Acceptable/Guideline and satisfies the guideline requirement for a developmental toxicity study in rabbits (§83-3b). No deficiencies were noted which would adversely affect the interpretation of this study.

A.4.3	Reproductive Toxicity

	870.3800 Reproduction and Fertility Effects - Rat

In a multigeneration reproduction study (MRID 00138155), DOWCO[(R)] 290 (96.7% a.i.; Identification No. ARG-l92532) was administered to groups of 30 Fischer-344 rats/sex/dose at dietary concentrations of 0, 150, 500, or 1500 mg/kg/day for two generations. Two litters were produced in both generations. F1 adults were chosen from the F1b pups and weaned onto the same diet as their parents. Test or control diets were administered to the F0 parental animals for up to 14 weeks and to the F1 parental animals for up to 17 weeks before the animals were mated within the same dose group. All animals were continuously exposed to test material either in the diet or via lactation until sacrifice.

Death of two F0 females and two F1 females was considered incidental to treatment; all other F0 and F1 males and females survived to terminal sacrifice. No treatment-related clinical signs of toxicity were observed in males or females of either generation at any time during the study. Gross necropsy and histological examination of the parental animals revealed a treatment-related effect in the gastric squamous mucosa in high dose males of both generations. Histopathology revealed slight focal hyperkeratotic changes in the gastric squamous mucosa of 1 of 30 F0 males and 2 of 30 F1 males of the high dose. Body weights, body weight gains, and food consumption of the low- and mid-dose F0 and F1 males and females were not affected in a biologically relevant manner.

Absolute body weights of the high-dose F0 males were significantly (p <= 0.05) decreased (96-97% of controls) during the premating interval. Overall weight gain by the high-dose males was 95 % (p<=0.05) of the control group mean. Food consumption by the high-dose male group was significantly (p <= 0.05) less than the controls for much of the premating interval. High-dose F0 females had significantly (p <= 0.05) lower absolute body weights (96-97% of the control levels). Overall mean body weight gain by the high-dose females was slightly reduced (88% of controls) during the premating interval. Food consumption by the high-dose female group was significantly (p <=0.05) less than the controls for a only few weeks of the premating interval. Mean body weight among high-dose F0 females was also decreased during the lactation intervals of both litters (93-97% of control).

Mean body weight among F1 males fed 1500 mg/kg/day was significantly (p <= 0.05) decreased (93 - 94 % of control values) beginning with day 27 and continuing throughout the study; mean overall body weight gain was 96 % (n.s.) of the control. Mean food consumption was significantly (p <= 0.05) decreased among males receiving 1500 mg/kg/day during a few weeks of the premating interval, values for this group were 92 - 95% of control. Mean body weight among females fed 1500 mg/kg/day was significantly (p <= 0.05) decreased beginning with day 55 of the premating exposure period; mean body weight for this group was consistently 96 % of the control means. Mean food consumption among F1 females fed 1500 mg/kg/day was not effected during the premating interval. Lactational body weight of dams was only sporadically affected during the nursing of either the F2a, or F2b litters.  

The LOAEL for parental systemic toxicity is 1500 mg/kg/day based on decreased body weights, body weight gains, and food consumption in the F0 and F1 males and females and slight focal hyperkeratotic changes in the gastric squamous mucosa of 1 of 30 F0 males and 2 of 30 F1 males. The parental systemic toxicity NOAEL is 500 mg/kg/day.

Mating, fertility, gestation, and parturition indices, and mean gestation length were similar between the treated and control female groups of both generations. 

The NOAEL for reproductive toxicity is 1500 mg/kg/day (HDT).  A LOAEL for reproductive toxicity was not determined (>1500 mg/kg/day).

Mean litter size, live births, and pup survival were also similar between the treated and control groups for both generations. No treatment-related clinical signs of toxicity were observed in the F1a, F1b, F2a, or F2b pups during lactation. Body weight was significantly decreased by 8-10% in Day 28 male pups of the high dose of the F1a and F1b litters of the F1 generation, but not the F2 generation in comparison to the controls. Relative liver weight was significantly increased in F1a pups (both sexes) and F1b males at the high dose in comparison to controls. No treatment-related effects were observed among treated pups compared to the controls upon histopathological examination.

The LOAEL for offspring toxicity is 1500 mg/kg/day based on the decreased Day 28 body weight of male pups of both litters of the F1 generation and the increased relative liver weight of F1a pups (both sexes) and F1b males of the F1 generation. The offspring toxicity NOAEL is 500 mg/kg/day.

This study is classified as Acceptable/Guideline and satisfies the requirements for a reproduction study (§870.3800) in rats.

A.4.4	Chronic Toxicity

	870.4100a (870.4300) Chronic Toxicity  -  Rat

In a chronic toxicity/carcinogenicity study (MRID 00162393 and 00162434), DOWCO(R) 290 (Clopyralid technical, 96.7% a.i.; lot number not reported) was administered in the diet to groups of 70 male and 70 female Fischer-344 rats at concentrations delivering doses of 0, 15, 150, or 1500 mg/kg/day. Groups of 10 rats per sex per dose were killed at 6 and 12 months for interim evaluations; the remaining 50 rats per sex per dose were maintained on treated or control diets for up to 24 months.

No treatment-related effects were observed on mortality or clinical signs of toxicity at any dose. Mean body weights were significantly decreased by 2-5% (p<=0.05) in male rats fed 1500 mg/kg/day and by 2-9% (p<=0.05) (except for an 11% decrease at last time point) in 1500 mg/kg/day group females compared with the weights of controls. Males in the 1500 mg/kg/day group gained 5% less weight than controls during the first year of the study and 7% less weight overall, whereas 1 500-mg/kg/day group females gained 11% less during the first year and 1:6% less weight overall. Food consumption by 1500 mg/kg/day group male and female rats was significantly decreased by as much as 8% and 7%, respectively, at sporadic time points during the study. No treatment-related effects were observed on body weights or food consumption in the 15 or 150 mg/kg/day groups.

Statistically significant changes were observed for hematologic parameters, serum chemistry parameters, and relative organ weights, but none were considered treatment related. The changes showed no dose-related trend, were transient in duration, or the magnitude of the change was not considered biologically significant.  The primary target for DOWCO(R) 290 was the limiting ridge of the stomach. No gross or microscopic lesions affecting the limiting ridge were observed in 15 mg/kg/day groups. Gross examination showed that the limiting ridge was increased in size in almost all male and female rats receiving 1500 mg/kg/day for 12 or 24 months. Microscopic examination showed epithelial hyperplasia of the limiting ridge in almost all 1500 mg/kg/day group male and female rats at 6, 12, and 24 months. The same lesion was observed in one or two male or female rats receiving 150 mg/kg/day for 6 and 12 months and in 52% of males and 42% of females at 24 months. The limiting ridge was thickened in two to seven male and female rats receiving 1500 mg/kg/day for 6 and 12 months and in 80% of males and 58% of females at 24 months. The limiting ridge was also thickened in one or two males or females receiving the 150 mg/kg/day dose for up to 24 months. Other treatment-related stomach lesions observed at 1500 mg/kg/day included chronic active inflammation in 6/10 males at 12 months compared with 0/10 in the control group, and mononuclear cell aggregates in the stomach mucosa in 23/50 (p>0.05) males and 25/50 (p<=0.05) females compared with 12/50 controls of each sex. In addition, a statistically significant increase in the incidence of mononuclear cell aggregates in the lacrimal/Harderian gland was observed in males receiving 1500 mg/kg/day (21/50 vs 9/50 for controls, p<=0.05).

The LOAEL is 150 mg/kg/day for male and female rats based on histopathologic findings in the stomach (epithelial hyperplasia and thickening of the limiting ridge). The corresponding NOAEL is 15 mg/kg/day.
There was no evidence of potential carcinogenicity of the test material at the doses given in this study. No neoplastic lesions occurred in treated groups at incidences significantly higher than the incidences in control animals. The doses administered were adequate for testing carcinogenicity as evidenced by histopathologic lesions in the stomach at the 150 and 1500 mg/kg/day doses. In addition, the high dose of 1500 mg/kg/day exceeded EPA's limit dose of 1000 mg/kg/day. 

This chronic toxicity/carcinogenicity study in the rat is Acceptable/Guideline and it satisfies the guideline requirement for a chronic toxicity/carcinogenicity oral study [OPPTS §870.4300] in rats. Deficiencies were noted, but none affected the interpretation of the results.

	870.4100b Chronic Toxicity - Dog

In a chronic oral feeding toxicity study (MRID 00158256), Clopyralid (Batch No. AGR 192532, 95.8% purity) was administered to groups of six male and six female beagle dogs for 52 weeks at doses of 0, 100, 320, or 1000 mg/kg/day in the diet.

No animals died as a result of treatment, and no treatment-related clinical signs of toxicity were observed. There were no treatment-related effects on mean body weight, body weight gain, or food consumption. Red blood cell count and its associated parameters showed a dose-related, statistically significant reduction in both sexes of mid- and high-dose dogs. These changes are judged to be adverse and toxicologically significant, based on their magnitude (10-28% reduction in RBCs). Clinical chemistry changes (decreased albumin, globulin, or serum protein at one or more sampling times) at the high dose in both sexes were highly statistically significant and considered treatment related. Highly significant increased absolute and relative liver weight in both sexes of high dose dogs and absolute liver weight in mid dose males was considered toxicologically significant although in the absence of associated findings.  Gross and histological changes seen in the lungs of treated dogs were evidently an inflammatory response to inhaled food particles, caused by the dogs "mouthing" their food, and not the result of systemic toxicity. Microscopically observed skin findings were increased in incidence and severity at the high dose in both sexes and included acanthosis (m,f), hyperkeratosis (m), and acute ulcerative dermatitis (f) and were considered treatment related. A dose-related increase in both incidence and severity of slight to mild focal vacuolation of adrenal cortical cells at the mid dose of females and high dose of both sexes was considered a significant toxicological effect.

The chronic oral toxicity LOAEL for dogs is 320 mg/kg/day for both sexes, based on a reduction in the hematological parameters, increased absolute liver weight in males, and vacuolated adrenal cortical cells in females. The NOAEL is 100 mg/kg/day.

This chronic oral toxicity study is classified as Acceptable/Guideline and satisfies the guideline requirement for a chronic oral toxicity study (§870.4100b) in dogs.

A.4.5	Carcinogenicity

	870.4200a Carcinogenicity Study - rat

See 870.4100a (870.4300)(Chronic oral toxicity/carcinogenicity  -  rat)
	870.4200b Carcinogenicity (feeding) - Mouse

In an oncogenicity study (MRID 00157783), DOWCO[(R)] 290 (technical, 96.7% a.i., batch/lot no. not supplied) was administered to groups of 70 male and 70 female B6C3F1 mice in the diet at concentrations providing 0, 100, 500, or 2000 mg/kg/day for up to 24 months. The dietary concentrations were adjusted weekly or monthly to maintain the target dose level using the food intake and body weights. Ten animals per sex per group were utilized for 6 month and for 12 month interim studies.

Treatment with DOWCO[(R)] 290 did not result in a significant decrease in survival or increases in clinical signs in treated groups compared with the control groups. Group mean body weights of males at 2000 mg/kg/day were decreased by 5% to 13% (p <=0.05) from treatment days 91 to 708 compared to the controls. The mean overall body weight gain in males was decreased by about 15% at 2000 mg/kg/day and by 8% at 100 and 500 mg/kg/day compared to the control group. The overall food efficiency in males was also 18% lower at 2000 mg/kg/day than that of the control group. The body weight and weight gain in females were not affected by treatment with DOWCO[(R)] 290 and the food efficiency in females was higher in the treated groups than in the control.

No treatment-related changes were seen in hematology parameters. Group mean blood glucose levels were increased in males by 20% and 27% (p <=0.05) at 500 and 2000 mg/kg/day, respectively, after 6 months of treatment, and by 42% and 36% (p <= 0.05) after 24 months. Blood glucose levels were also increased in females by 28%, 9%, (NS) and 34% (p <=0.05) at 100, 500, and 2000 mg/kg/day, respectively, after 6 months, but were not significantly increased at 12 or 24 months. The toxicological significance of the changes in blood glucose levels in treated animals is compromised by the use of non-fasted animals, the lack of a clear dose effect in females at 6 months and males at 24 months, and the lack of significant changes at 12 months in both sexes and at 24 months in females. A decrease in alkaline phosphatase activity of 51% was seen in females at 2000 mg/kg/day compared to the control after 24 months of treatment. The decreased activity appears to be associated, at least in part, with a decrease in the incidence of bone fibrous osteodystrophy in high-dose females (control, 35/50; 2000 mg/kg/day, 26/50, NS). A slight decrease in the incidence of sciatic nerve axon degeneration was seen in high-dose males at 24 months (control, 16/50; 2000 mg/kg/day, 8/50, p <=0.05). No treatment- related adverse effects were seen during the histopathologic examinations.

The LOAEL is 2000 mg/kg/day based on decreased body weight, body weight gain, and food efficiency for males. The LOAEL was not identified for females (>2000 mg/kg/day). The NOAEL was 500 mg/kg/day for males; 2000 mg/kg/day for females.

There was no evidence of oncogenic potential under the conditions of this study. Major organs examined included liver, kidney, testes, lung, ovary, bladder, brain, and thyroid. The dosing based on toxic response was marginal in males and inadequate in females. The high dose of 2000 mg/kg/day was above the limit dose for non-toxic agents and, therefore, was considered adequate for the oncogenicity study.  This study is classified as Acceptable/guideline and does satisfy the guideline requirement for an oncogenicity study (§870.4200b) in mice.

A.4.6	Mutagenicity

	Gene Mutation
870.5300, in vitro (Salmonella and Saccharomyces) and in vivo  (mouse) host-mediated gene mutation assay
MRID  00057086
Acceptable/Guideline
Negative for evidence of induction of mutant colonies over background levels in Salmonella or Saccharomyces strain D-3 at doses in the presence or absence of S9.  Mice exposed to 4, 40 or 400 mg/kg by gavage.

	Cytogenetics
870.5385, in vivo micronucleus assay in the rat
MRID 00073638
Acceptable/guideline
Negative for evidence of increased incidence of treatment-related bone marrow chromosomal aberrations at 4, 40 or 400 mg/kg/day.

	Other Genotoxicity
870.5450, dominant lethal assay in the rat
MRID 00059053, 00099100
Acceptable/guideline
Negative for evidence of increased incidence of treatment-related resorptions at 4, 40 or 400 mg/kg/day for 5 days prior to mating.
870.5550, unscheduled DNA synthesis in the rat
MRID 00156387, 41790702
Acceptable/guideline
Negative for evidence of increased unscheduled DNA synthesis up to insoluble concentrations when tested at concentrations between  9.6 to 9600 ug/mL for 18 to 20 hrs.

A.4.7	Neurotoxicity

	870.6200 Subchronic Neurotoxicity Screening Battery (Acute and Subchronic)

Not required.

A.4.8	Metabolism

	870.7485	Metabolism - Rat

In a metabolism study (MRID 41790703), groups of five male and five female rats were given a single oral dose of [[14]4C]-Clopyralid (5 or 150 mg/kg; Lot no. 805 [ref. no. GHD-2775-l0a, purity >96%), a single intravenous dose (5 mg/kg) of radiolabeled test article, or 14-day repeated 5 mg/kg/day oral doses of non-radiolabeled Clopyralid (Lot no. AGR 233257; radiochemical purity >99%) followed by a single 5 mg/kg oral dose of radiolabeled test article. Additionally, a pretest experiment to assess pulmonary excretion was performed in which two male and two female rats were given a single oral dose (5 mg/kg). An untreated control group consisted of one male and one female rat.

There were no deaths or overt signs of toxicity reported. Radioactivity inventory indicated an acceptable recovery (95-115%) of the administered dose among the experimental groups in the definitive phase of the study.  Clopyralid was nearly completely absorbed at the doses tested. Under the conditions of this study, tissue and carcass burdens were negligible for all groups, suggesting little potential for accumulation. Minimal radioactivity (<=0.0 1% at 72 hours) was found in the gastrointestinal tract and organs associated with excretion (e.g., liver, kidneys). Urinary excretion accounted for most (91-113% at 72 hours postdose) of the administered test material regardless of the administration route or dose. There did not appear to be any biologically relevant gender- dependent differences in total urinary excretion or excretion rates. Most urinary excretion (74-98% of administered dose) occurred within 6 hours after administration for all low dose groups and within 12 hours for the repeated-dose group. Fecal excretion was negligible and, at 72 hours, accounted for <4% of the administered dose in all treatment groups.  HPLC and TLC analysis of urine and fecal samples indicated that the radioactivity inventory represented only parent compound. There was no evidence of metabolites.

This metabolism study in rats is classified as Acceptable/Guideline and satisfies the guideline requirement for a Metabolism and Pharmacokinetics study in the rat (§870.7485).

A.4.9	Immunotoxicity

	870.7800	Immunotoxicity

In an immunotoxicity study (MRID 483000001) Clopyralid (95.9% a.i., Lot No. 910905 5P) was administered to male F344/DuCrl rats in the diet designed to give nominal dose levels of 0 (vehicle control and positive control), 150, 500, or 1000 mg/kg bw/day (actual dose levels of 0, 158, 530, and 1062 mg/kg bw/day, respectively) (10 animals/dose) for 29 days (Day 1-29).  On Day 25, animals in all groups were immunized with a suspension of sheep red blood cells (SRBC) by intravenous injection (2x10[8] SRBC/animal, 0.5 mL/animal dose volume).  Animals in the positive control group received an intraperitoneal injection of cyclophosphamide on Days 24-28 at a dose of 20 mg/kg bw (1 mL/kg bw dose volume).  All animals were evaluated for mortality, clinical signs, body weight changes, and gross pathology.  The vehicle control and test substance treatment groups also were evaluated for food consumption, hematologic parameters, and histopathology.  Immunotoxicity was assessed for all animals by ELISA assay; spleen and thymus weights were determined at necropsy.  
 
There were no test substance-related effects on mortality, clinical signs, body weight changes, food consumption, hematologic parameters, histopathology or gross pathology. A LOAEL for systemic toxicity could not be determined for Clopyralid in male rats (i.e., greater than the nominal dose of 1000 mg/kg bw/day, actual dose of 1062 mg/kg bw/day, highest dose tested) based on the evaluated parameters.  The NOAEL for systemic toxicity is 1000 mg/kg bw/day (actual dose of 1062 mg/kg bw/day), highest dose tested and the limit dose.
There were no test substance-related effects on serum anti-SRBC IgM antibody levels as measured by ELISA assay, on thymus and spleen weights, or on hematologic parameters.  A LOAEL for immunotoxicity could not be determined for Clopyralid in male rats (i.e., greater than the nominal dose of 1000 mg/kg bw/day, actual dose of 1062 mg/kg bw/day, highest dose tested) based on the evaluated parameters.  The NOAEL for immunotoxicity is 1000 mg/kg bw/day (actual dose of 1062 mg/kg bw/day), highest dose tested and the limit dose.

This immunotoxicity study is classified as acceptable/guideline and satisfies the guideline requirement for an immunotoxicity study (OPPTS 870.7800) in the rat.  Information regarding the stability of the test substance, storage conditions of the test substance and dietary formulations, and references for the historical control thymus weight data should be submitted.

Appendix B.  Clopyralid Physical/Chemical Properties

Physicochemical Properties of the Technical Grade Clopyralid 
Parameter
Value
References
Physical State
Solid
A world Compendium, The Pesticide Manual, 14[th]  Edition. C.D. S Tomlin (Editor), 2006.
Color
Colorless

Melting Point/Range
151-152°C

Dissociation Constant (pKa)
2

Density at 20°C
1.57 g/cm3 

Vapor Pressure at 25°C
1.0 x 10[-5] mm Hg (1.33 mPa)

Water Solubility at 20°C
7.85 g/L

Solvent solubility (g/L) at 20°C
Acetone:  250
Ethyl acetate:  102
Xylene:  4.6
Hexane:  6.0

Octanol/water partition coefficient, Log (KOW)
-1.81 (pH 5) 
-2.63 (pH 7) 
-2.55 (pH 9)

Appendix C.  Review of Human Research

This risk assessment relies in part on data from studies in which adult human subjects were intentionally exposed to a pesticide or other chemical.  These data, which include studies from the Pesticide Handlers Exposure Database Version 1.1 (PHED 1.1); the Agricultural Handler Exposure Task Force (AHETF) database; and other registrant-submitted exposure monitoring studies (MRID 44339801), are subject to ethics review pursuant to 40 CFR 26, have received that review, and are compliant with applicable ethics requirements.  For certain studies, that review may have included review by the Human Studies Review Board.  Descriptions of data sources as well as guidance on their use can be found at:  http://www.epa.gov/pesticides/ science/handler-exposure-data.html and http://www.epa.gov/pesticides/science/post-app-exposure-data.html.