Acibenzolar-S-Methyl Human Health Risk Assessment DP No. 424596 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

Date: Aug 13, 2015 

MEMORANDUM 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: Acibenzolar-S-Methyl. Human Health Risk Assessment to support Section 3 

Use of Acibenzolar-S-Methyl Uses on Citrus Crop Group 10-10, and Pome Crop 

Group 11-10. 

PC Code: 061402 

Decision No.: 490192 

Petition No.: 4F8269 

DP Barcode: 424596 

Registration Nos.: 100-921 (tech), I 00-922 

Regulatory Action: Section 3 Registration 

Risk Assessment Type: Single Case No.: 7031 

Chemical Aggregate 

TXRNo.: NA 

MRID No.: NA 

FROM: 

CAS Nos.: 135158-54-2 

40 CFR: 180.561 

Dennis McNeilly, Risk Assessor 9.-- /v'J- { ,/A 

Bonnie Cropp-Kohlligian, Environmental S~i;n9;t ~.... ?-

Shirley Keel, Ph.D., Biologist ~ ( f,L(_ 

Ivan Nieves, Biologist {1---e,;/_;__ . Abdallah Khasawinah, Toxicologist /1 {~ Risk Assessment Branch 4 

Health Effects Division (7509P) 

THROUGH: Charles Smith, Acting Branch Chiu_~, Risk Assessment Branch 4 

Health Effects Division (7509P) 

TO: Erik Kraft/Heather Garvie (RM 24) 

Fungicide Branch 

Registration Division (7505P) 

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Table of Contents

1.0 Executive Summary............................................................................................................. 4

2.0 HED Recommendations...................................................................................................... 6

2.1 Data Deficiencies/Conditions of Registration...................................................................6

2.2 Tolerance Considerations..................................................................................................7

2.2.1 Enforcement Analytical Method ............................................................................7

2.2.2 International Harmonization ..................................................................................7

2.2.3 Recommended Tolerances .....................................................................................7

2.2.4 Revisions to Petitioned-For Tolerances .................................................................8

2.3 Label Recommendations...................................................................................................8

2.3.1 Recommendations from Residue Reviews.............................................................8

2.3.2 Recommendations from Occupational Assessment...............................................8

2.3.3 Recommendations from Residential Assessment ..................................................8

3.0 Introduction ......................................................................................................................... 8

3.1 Chemical Identity ..............................................................................................................8

3.2 Physical/Chemical Characteristics....................................................................................9

3.3 Pesticide Use Pattern.........................................................................................................9

3.4 Anticipated Exposure Pathways......................................................................................11

3.5 Consideration of Environmental Justice .........................................................................11

4.0 Hazard Characterization and Dose-Response Assessment................................................ 12

4.1 Toxicology Studies Available for Analysis ....................................................................12

4.2 Absorption, Distribution, Metabolism, & Elimination (ADME)....................................12

4.2.1 Dermal Absorption...............................................................................................13

4.3 Toxicological Effects ......................................................................................................13

4.4 Safety factor for Infants and Children (FQPA Safety Factor) ........................................14

4.4.1 Completeness of the Toxicology Database ..........................................................15

4.4.2 Evidence of Neurotoxicity ...................................................................................15

4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal.......15

4.4.4 Residual Uncertainty in the Exposure Database ..................................................15

4.5 Toxicity Endpoint and Point of Departure Selections.....................................................16

4.5.1 Dose-Response Assessment .................................................................................16

4.5.2 Recommendation for Combining Routes of Exposures for Risk Assessment.....17

4.5.3 Cancer Classification and Risk Assessment Recommendation ...........................17

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

Assessment .........................................................................................................................17

5.0 Dietary Exposure and Risk Assessment ............................................................................ 19

5.1 Metabolite/Degradate Residue Profile ............................................................................19

5.1.1 Summary of Plant and Animal Metabolism Studies............................................19

5.1.2 Summary of Environmental Degradation ............................................................20
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5.1.3 Comparison of Metabolic Pathways ....................................................................20

5.1.4 Residues of Concern Summary and Rationale.....................................................20

5.2 Food Residue Profile.......................................................................................................22

5.3 Water Residue Profile .....................................................................................................22

5.4 Dietary Risk Assessment.................................................................................................23

5.4.1 Description of Residue Estimates Used in Dietary Assessment ..........................23

5.4.2 Percent Crop Treated Used in Dietary Assessment .............................................24

5.4.3 Acute Dietary Risk Assessment...........................................................................24

5.4.4 Chronic Dietary Risk Assessment........................................................................25

6.0 Residential (Non-Occupational) Exposure/Risk Characterization .................................... 26

6.1 Residential Post-Application Exposure...........................................................................26

6.2 Residential Bystander Post-application Inhalation Exposure .........................................26

6.3 Spray Drift.......................................................................................................................27

6.4 Residential Risk Estimates for Use in Aggregate Assessment .......................................27

7.0 Aggregate Exposure/Risk Characterization....................................................................... 28

7.1 Short- and Intermediate-Term Aggregate Risk...............................................................28

8.0 Cumulative Exposure/Risk Characterization..................................................................... 29

9.0 Occupational Exposure/Risk Characterization.................................................................. 29

9.1 Short- and Intermediate-Term Handler Risk Estimates..................................................30

9.2 Short- and Intermediate-Term Post-Application Risk Estimates....................................33

9.2.1 Dermal Post-Application Risk Estimates.............................................................33

9.2.2 Inhalation Post-Application Risk Estimates.........................................................35

10.0 References ......................................................................................................................... 36

Appendix A. Toxicology Profile and Executive Summaries....................................................... 37

A.1 Guideline Data Requirements.........................................................................................37

A.2 Toxicity Profiles..............................................................................................................38

A.3 Toxicological Endpoints .................................................................................................44

A.3.1 Acute Reference Dose (aRfD) - General Population ...........................................44

A.3.2 Chronic Reference Dose (cRfD) - Females age 13-49 and Young Children.......44

A.3.3 Chronic Reference Dose (RfD) – Adult Males and Females 50+ years ..............45

A.3.4 Incidental Oral Exposure (Short- and Intermediate-Term)..................................47

A.3.5 Dermal Absorption...............................................................................................47

A.3.6 Dermal Exposure (Short and Intermediate-Term) ...............................................47

A.3.7 Inhalation Exposure (Short and Intermediate-Term) ...........................................48

A.4 Executive Summaries......................................................................................................49

Appendix B. Chemical Names and Structures of Metabolites .................................................... 55

Appendix C. Physical/Chemical Properties................................................................................. 57

Appendix D. Studies Reviewed for Ethical Conduct................................................................... 58
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1.0 Executive Summary

This assessment supports the Section 3 registration for use of acibenzolar-S-methyl on citrus and 

pome fruit. It addresses the exposures and human health risks associated with exposures from 

currently registered uses and the proposed new uses of acibenzolar-S-methyl. It also assesses 

potential enhanced sensitivity of infants and children from dietary and/or residential exposure as 

required under the Food Quality Protection Act (FQPA) of 1996.

Acibenzolar-S-methyl is a plant activator. It is a member of the benzothiadiazole class of 

compounds. Acibenzolar-S-methyl is registered to Syngenta Crop Protection, Inc for use on a 

number of leafy and fruiting vegetable crops and tobacco for the control or suppression of downy 

mildew, black rot, white rust, bacterial leaf spot and speck, and blue mold. Permanent tolerances 

ranging from 0.1-3.0 ppm are established under §180.561(a). Acibenzolar-S-methyl is also used 

in commercial seed treatment operations for protection against certain early season seed and 

seed-borne nematodes in cotton and on sod farms, golf courses, collegiate athletic fields, and 

lawns around commercial and industrial buildings to control turf diseases. Agricultural 

applications may be made using ground or aerial equipment.

 

Syngenta Crop Protection, LLC is requesting new uses of acibenzolar-S-methyl, formulated as a 

50% water dispersible granule (WDG; Actigard® 50WG; EPA Reg. No. 100-922), on citrus crop 

group 10-10 and pome crop group 11-10. Acibenzolar-S-methyl is proposed for multiple soil 

applications (i.e., drench, drip or micro-irrigation) on citrus crop group 10-10 and pome crop 

group 11-10 as well as for multiple foliar applications on pome crop group 11-10. It is also 

proposed for paint applications to pome fruit trees.

Acibenzolar-S-methyl has an active experimental use permit (100-EUP-115; expiration date 

12/31/2015) for use on apple, grapefruit and pear at rates similar to those under consideration, 

but allowing foliar use on grapefruit and a 30-day PHI for foliar use on apple, grapefruit, and 

pear.

Hazard Identification

The toxicology database for acibenzolar-S-methyl is adequate for evaluating and characterizing 

toxicity and selecting endpoints for purposes of this risk assessment. 

In subchronic and chronic oral studies in rats, dogs and mice, signs of mild regenerative 

hemolytic anemia were consistently observed in all three species. Additional toxic effects 

observed in these studies included decreases in body weight, body weight gain and/or food 

consumption. No other significant treatment-related effects of toxicological concern were 

observed in these subchronic and chronic oral studies. No neurotoxic effects were seen at the 

highest dose tested in a subchronic neurotoxicity study in rats. In a 28 day dermal toxicity study 

in rats, no systemic or dermal effects were seen at the limit dose.
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In a developmental toxicity and developmental neurotoxicity studies in rats, treatment related 

effects were observed in fetuses at levels that were not toxic to the parent indicating increased 

sensitivity of rat fetuses compared to adults. Increased sensitivity was not observed in a 

developmental toxicity study in rabbits, nor in 1- and 2-generation reproduction studies in rats. 

In a 28 day dermal developmental toxicity study in rats, no maternal or developmental toxicity 

was observed at dose levels up to 500 mg/kg/day, the highest dose level tested. 

Acibenzolar-S-methyl was classified by HED’s Hazard Identification Assessment Review 

Committee (HIARC) as “not likely” to be a human carcinogen based on negative carcinogenicity 

findings in male and female rats and mice and negative results in an acceptable battery of 

genotoxicity studies. 

Acibenzolar-S-methyl technical grade material showed no significant toxicity in a battery of 

acute toxicity tests (Toxicity Category III or IV in all tests) but showed considerable skinsensitivity. The end-use product (ActigardTM 50WG) displayed no significant acute toxicity and 

no dermal sensitizing potential.

An immunotoxicity study required as part of new 40 CFR Part 158 data requirements for 

registration of a pesticide has been submitted and reviewed. Acibenzolar-S-methyl did not 

produce systemic toxicity or immunotoxicity at any dose (up to 406 mg/kg/day) including the 

highest dose tested in this study.

Dose Response Assessment

Toxicological endpoints were selected for dietary/drinking water, occupational and residential 

exposure scenarios. Acute and chronic reference doses (RfDs) were selected for assessment of 

food and drinking water exposures. An acute POD of 8.2 mg/kg/day (NOAEL) was selected for 

females 13-49 years old and children 1-12 years old from a developmental neurotoxicity study in 

rats based on changes in brain morphometrics in the cerebellum at the LOAEL of 82 mg/kg/day. 

No acute endpoint was identified for adults. The developmental neurotoxic effects of concern are 

presumed to occur after a single exposure and are relevant to females aged 13-49 years old since 

they occur in utero and to young children based on post-natal effects. A chronic POD of 8.2 

mg/kg/day (NOAEL) was selected for females 13-49 and young children from a developmental

neurotoxicity study in rats based on changes in brain morphometrics in the cerebellum at the 

LOAEL of 82 mg/kg/day. The effects observed in this study can occur after single or multiple 

doses. Selection of a chronic endpoint from this study ensures that the chronic exposure 

assessment is protective of females of reproductive age and their offspring. A chronic RfD 

(cPAD=0.25 mg/kg/day) for the general population was selected on the basis of hemolytic

effects seen in a chronic feeding study in dogs and other co-critical toxicity studies.

Toxicological endpoints for inhalation, dermal, and incidental oral exposures were selected from 

the developmental neurotoxicity study in rats. A dermal absorption factor was selected from a 
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dermal absorption study in rats. An uncertainty factor of 100X was applied to endpoints selected 

for all exposure routes (10x for interspecies extrapolation, 10x for intraspecies variation).

Exposure/Risk Assessment and Risk Characterization

Risk assessments were conducted for dietary (food and water) and occupational exposure 

pathways based on the request for the use of acibenzolar-S-methyl on citrus and pome fruit. A 

revised residential assessment was conducted to update the residential exposures based on the 

revised SOPs. Refined acute and screening level chronic dietary and drinking water risk 

assessments for acibenzolar-S-methyl demonstrate that dietary and drinking water exposure 

estimates are below HED’s level of concern for the general population and all population 

subgroups. Occupational exposure and risk estimates indicate that worker handler and postapplication exposures are not of concern at the maximum allowable application rates for the 

proposed new uses. Aggregate risks are not of concern.

Use of Human Studies

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 studies, listed in Appendix D, have 

been determined to require a review of their ethical conduct. Some of these studies are also 

subject to review by the Human Studies Review Board. All of the studies used have received the 

appropriate review.

2.0 HED Recommendations

HED has no objection to granting the registrations for use of acibenzolar-S-methyl on the 

requested crops or to the establishment of permanent tolerances for residues of acibenzolar-Smethyl as specified in Section 2.2.3.

2.1 Data Deficiencies/Conditions of Registration

ORE: In accordance with 40 CFR 158, dislodgeable-foliar residue (DFR) data are required for 

all occupational (e.g., crop, nursery, greenhouse use sites) uses that could result in postapplication exposure to foliage. The proposed uses for acibenzolar-S-methyl could result in 

occupational post-application exposure; however, chemical-specific DFR data are not available.

Since the highest estimated occupational post-application exposure using default DFR values for 

acibenzolar-S-methyl is not minimal in comparison to the LOC (i.e., the calculated MOE is not 

greater than two times higher than the LOC, MOE = 160 compared to the LOC of 100); EPA is 

requiring the 40 CFR DFR data to facilitate any necessary exposure assessments refinements and 

to further EPA’s general understanding of the availability of dislodgeable foliar pesticide 

residues. These data should be submitted with any future uses of acibenzolar-S-methyl.
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2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

HPLC/UV Method AG-617A is available for tolerance enforcement. This method has undergone 

a successful tolerance method validation by the Analytical Chemistry Branch of BEAD. The 

method was forwarded to FDA for inclusion in PAM Volume II. Briefly, the method consists of 

an initial hydrolysis with NaOH to convert acibenzolar-S-methyl to CGA-210007 followed by 

methanol extraction. Residues are then diluted with HCl and purified by a series of solid-phase 

extraction steps. Prior to HPLC/UV analysis, residues are partitioned into ethyl acetate, dried 

down, and re-dissolved in phosphoric acid. This method has a limit of quantitation (LOQ) of 

0.02 ppm. The method includes optional detection via HPLC/MS, giving a means of residue 

confirmation.

2.2.2 International Harmonization

There are no Codex, Mexican, or Canadian maximum residue limits for acibenzolar-S-methyl 

in/on any commodity. Therefore, international harmonization is not an issue. 

2.2.3 Recommended Tolerances

HED recommends that 40 CFR §180.561 be amended by establishing tolerances for residues of 

acibenzolar-S-methyl in the plant commodities listed in Table 2.2.3, at the recommended levels 

shown therein.

TABLE 2.2.3 Tolerance Summary for Acibenzolar–S-Methyl

Commodity as Proposed by 

Petitioner

Proposed 

Tolerance (ppm)

Recommended 

Tolerance (ppm)

Correct Commodity Definition; 

Comments

Fruit, citrus, group 10-10 0.01 0.02 ppm Fruit, citrus, group 10-10*

(Tolerance is recommended at the LOQ 

of the enforcement method.)

Fruit, pome, group 11-10 0.03 0.03 ppm Fruit, pome, group 11-10*

*Note: Time-limited tolerances (expiration date 12/31/2015) are established under §180.561(a)(2) at 0.05 ppm in/on apple, 

grapefruit and pear to cover incurred residues from the experimental use permit (EUP) of acibenzolar-S-methyl on these crops 

(100-EUP-115 permit; expiration date 12/31/2015) at rates similar to those under consideration, except allowing foliar use on 

grapefruit and a much shorter PHI for foliar uses (30 days). As a result of the current risk assessment action, the permanent 

tolerances will be lower than the current temporary tolerances.

Tolerances are currently listed in 40 CFR §180.561 for residues of acibenzolar-S-methyl, 

benzo(1,2,3)thiadiazole-7-carbothioic acid-S-methyl ester, including its metabolites and 

degradates. Compliance with the tolerance levels specified is to be determined by measuring 

only those acibenzolar-S-methyl residues convertible to benzo(1,2,3)thiadiazole-7-carboxylic 

acid (CGA-210007), expressed as the stoichiometric equivalent of acibenzolar-S-methyl, in or on 
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the commodity. The current tolerance expression is in accordance with current guidance 

(Knizner, 5/27/09).

2.2.4 Revisions to Petitioned-For Tolerances

The recommended tolerance for fruit, pome, group 11-10 (0.03 ppm) is the same as the 

petitioned-for tolerance; however the recommended tolerance level for fruit, citrus, group 10-10 

(0.02 ppm) is at the LOQ of the enforcement method which is higher than the petitioned-for 

tolerance (0.01 ppm).

2.3 Label Recommendations

2.3.1 Recommendations from Residue Reviews

The revised draft label (dated 8/12/15) should be further revised, consistent with the supporting 

pome data, to specify a 30-day minimum RTI for the soil use on pome.

Section B of the petition should be revised, consistent with the supporting pome data, as follows: 

(1) specify 60-day PHIs for the proposed foliar and paint uses on pome and (2) specify 30-day 

and 7-day minimum retreatment intervals (RTIs) for the proposed soil and foliar uses on pome, 

respectively.

2.3.2 Recommendations from Occupational Assessment

None.

2.3.3 Recommendations from Residential Assessment

None.

3.0 Introduction

3.1 Chemical Identity

Table 3.1. Acibenzolar-S-Methyl Nomenclature.

Chemical structure

N

N

S

O S

CH3

Common name acibenzolar-S-methyl
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Table 3.1. Acibenzolar-S-Methyl Nomenclature.

Company experimental 

name

CGA-245704

IUPAC name benzo[1,2,3]thiadiazole-7-carbothioic acid-S-methyl ester

CAS name S-methyl, 1,2,3-benzothiadiazole-7-carbothioate

CAS registry number 135158-54-2

End-use product (EP) Actigard® 50 WG (EPA Reg. No. 100-922)

Structure of metabolite 

CGA-210007

N

N

S

COOH

1,2,3-benzothiadiazole-7-carboxylic acid

3.2 Physical/Chemical Characteristics

A detailed description of the physiciochemical properties of acibenzolar-S-methyl is provided in 

Appendix C. Acibenzolar-S-methyl exhibits relatively low solubility in water and higher 

solubility in organic solvents. It has a very low vapor pressure. Acibenzolar-S-methyl does not 

present significant concerns for bioaccumulation based on the lipophilicity of the compound and 

mammalian metabolism studies.

3.3 Pesticide Use Pattern

Under Section B of the petition, Syngenta has submitted directions for proposed uses of 

acibenzolar-S-methyl on citrus and pome formulated as a water dispersible granule (WDG) 

containing 50% acibenzolar-S-methyl as the sole active ingredient (Actigard® 50WG; EPA Reg. 

No. 100-922). Subsequent to the submission of Section B of the petition, Syngenta submitted a 

revised draft label (dated 8/12/15) to provide updated and more complete proposed use 

directions. The revised draft label (dated 8/12/15) is the basis for the following proposed use 

rate discussion.

Acibenzolar-S-methyl is proposed for multiple soil (i.e., drench, drip or micro-irrigation) 

applications on citrus/pome, multiple foliar applications on pome and paint applications to pome 

trees. The proposed maximum use rate, for any of these treatments, is 0.1 lb ai/A/application 

(0.4 lb ai/A/year) with a 0-day pre-harvest interval (PHI) for soil treatment and a 60-day PHI for 

foliar or paint treatment. The use directions, based on the revised draft label (dated 8/12/15), are 

summarized in Table 3.3.
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Table 4. Summary of Directions for Use of Acibenzolar-S-methyl1

Applic. 

Timing, Type, 

and Equip.

Formulation

[EPA Reg. 

No.]

Applic. 

Rate 

(lb ai/A)

Max. No. 

Applic. per 

Season

Max. 

Seasonal 

Applic. 

Rate

(lb ai/A)

PHI

(days) Use Directions and Limitations

Citrus Crop Group 10-10

Soil drench/ 

Chemigation2; 

Ground Equip.3

using ≥ 10 gal/A3

Note: Aerial 

application is not 

indicated for use 

on this crop.3

50% WDG

[100-922]

0.1 4 (Implied) 0.4 0 day For suppression of citrus canker: Apply 

around the tree base at 0.0012 to 0.035 oz 

Actigard®/tree - within the first 4-6 inches

around the tree base. Determine rate based 

on tree age. For prevention, make up to 12 

applications on a 30-day minimum 

retreatment interval (RTI).

General Use Instruction3

Adjuvants may be used. 

Do not apply using ultra-low volume (ULV) 

spray systems.

Pome Crop Group 11-104

Foliar;

Ground Equip.3

using ≥ 10 gal/A3

Note: Aerial 

application is not 

indicated for use 

on this crop.3

50% WDG

[100-922]

0.1 4 (Implied) 0.4 60 days4 For suppression of fire blight:

Apply 2-3 times between 20% bloom and 

petal fall in a tank mix with antibiotic 

products to achieve best results. The 

minimum RTI is 7-days.4

General Use Instruction3

Adjuvants may be used. 

Do not apply using ultra-low volume (ULV) 

spray systems.

Soil drench/ 

Chemigation2;

Ground Equip.3

using ≥ 10 gal/A3

Note: Aerial 

application is not 

indicated for use 

on this crop.3

0 day For suppression of fire blight: 

Application should begin at green tip. Apply 

around the tree base at 0.0012 to 0.035 oz 

Actigard®/tree - within the first 4- to 6-

inches around the tree. Determine rate based 

on tree age. The minimum RTI is not 

specified.4

General Use Instruction3

Adjuvants may be used. 

Do not apply using ultra-low volume (ULV) 

spray systems.

Paint Application 60-days4 For suppression of fire blight: 

Paint application after canker cut-outs or 

grafts. Mix 1 oz Actigard® in 1 quart of 1% 

Pentrabark or similar penetrant. Apply to 

the branch area immediately below canker 

after cutting to an area extending 1 to 1.5 

feet. One quart will treat approximately 500 

cuts. 

1 Based on the revised draft label (dated 8/12/15) that was submitted subsequently to Section B of the petition. providing 

updated and more complete use directions.

2 May be applied via drip irrigation or microsprinkler irrigation. 
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3 Not specified in Section B of the petition but listed under general use instructions for the end-use product on the revised draft 

label (dated 8/12/15) as appropriate unless otherwise indicate under crop-specific directions.

4 For pome, use directions in Section B of the petition differed from the revised draft label (dated 8/12/15) as follows: (1) 

specified a 30-day PHI for foliar use; (2) did not specify a PHI for paint use; (3) specified a 7-day RTI for soil use; and (4) did 

not specify a RTI for foliar use.

Conclusions. The use directions are adequate to assess the proposed uses. Based on the revised 

draft label (dated 8/12/15) that provided updated and more complete proposed use directions 

than the earlier Section B of the petition, the submitted use information is considered adequate to 

allow evaluation of the residue data relative to the proposed uses of acibenzolar-S-methyl on 

citrus and pome fruit. 

The revised draft label (dated 8/12/15) should be further revised, consistent with the supporting 

pome data, to specify a 30-day minimum RTI for the soil use on pome. 

Section B of the petition should be revised, consistent with the supporting pome data, as follows: 

(1) specify 60-day PHIs for the proposed foliar and paint uses on pome and (2) specify 30-day 

and 7-day minimum retreatment intervals (RTIs) for the proposed soil and foliar uses on pome, 

respectively.

3.4 Anticipated Exposure Pathways

Dietary (food and water) and residential exposures are expected based on existing uses of 

acibenzolar-S-methyl and the proposed uses of acibenzolar-S-methyl on citrus, and pome fruit. A 

residential exposure assessment is not required for this assessment because there are no 

residential uses or exposures associated with the proposed new use. The short-term aggregate 

exposure assessment, which takes into account residential exposure plus average exposure levels 

to food and water, has been updated to incorporate dietary exposure from the use of acibenzolarS-methyl on citrus and pome fruit.

 

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 

Survey of Food Intake by Individuals (CSFII) and/or the CDC under the National Health and 

Nutrition Examination Survey/What We Eat in America (NHANES/WWEIA), and are used in 

pesticide risk assessments for all registered food uses of a pesticide. These data are analyzed and 
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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

The toxicology database for acibenzolar-S-methyl is adequate for evaluating and characterizing 

acibenzolar-S-methyl toxicity and selecting endpoints for purposes of this risk assessment

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

The absorption, distribution, metabolism, and excretion of acibenzolar-S-methyl were studied in 

rats. In the rat metabolism study [U14C Phenyl] acibenzolar-S-methyl was administered by 

stomach tube to male and female rats at single doses of 0.5 (low dose) or 100 mg/kg (high dose) 

or at a single dose of 0.5 mg/kg following 14 repeated daily doses of 0.5 mg/kg of nonlabeled 

acibenzolar-S-methyl. 

For all treatment groups, acibenzolar-S-methyl was rapidly and nearly completely absorbed 

(>90% of the administered dose) from the gastrointestinal tract into the general circulation. Peak 

blood levels were reached at 15-30 minutes after the low dose and at 4-8 hours after the high 

dose. Tissue levels of radioactivity were highest in blood, liver, kidney, skeletal muscle, heart 

and lungs. Radioactivity was rapidly excreted predominantly in the urine (88-95% within 48 

hours). Only a small amount of radioactivity was excreted in the feces (3.1-4.5% within 48 

hours). Insignificant radioactivity was excreted in the expired air. There was no significant 

enterohepatic circulation. After 7 days, levels of radioactivity remaining in the tissues were

extremely low. Absorption, distribution, pharmacokinetic and excretion profiles were largely 

independent of dose level and sex.

Three urinary fractions were identified. Fraction U3 (79-92% of the administered dose) was 

identified as the carboxylic acid derivative of the parent. Fraction U2 (0.4-2%) was identified as 

the corresponding glycine derivative of the carboxylic acid (fraction U3) derivative. Fraction U1 

(1- 4.5%) was a mixture of at least three polar compounds that were not identified due to 

insufficient sample material. No parent compound was detected in the urine. Radioactivity in the 

feces represented <5% of the administered dose. No single metabolite in the feces exceeded 3% 

of the administered dose. Fraction F2 (0.7-3% of the administered dose) was identified as the 
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carboxylic acid derivative of the parent. Fraction F3 (0.1-1%) was identified as parent 

compound. Fraction F1 (0.2-0.4%) was a very polar compound(s) that was not further identified. 

The metabolic fate of acibenzolar-S-methyl was independent of dose level, sex, and 

pretreatment.

4.2.1 Dermal Absorption

In a dermal absorption study in rats, acibenzolar-S-methyl was applied dermally to a shaved 

dorsal area of 10 cm2 at two dose levels of 10 μg/cm2 and 100μg/cm2 to two groups of animals 

consisting of six animals/group. Two animals from each group were sacrificed at 4, 8, and 24 

hours after dosing, and the amount of radioactivity in blood, urine, feces, liver, kidneys, spleen, 

and remaining carcass was determined. Amount of radioactivity remaining in/on the skin and on 

the cover was also determined. For the groups for which the skin was washed after 8 hours, mean 

dermal absorption values were 43.55% and 5.92%, and mean radioactivity levels remaining at 

the skin were 46.64%, and 90.22%, respectively at 10μg/cm2 and 100 μg/cm2 dose levels. Given 

the uncertainty regarding actual dermal deposition under actual field conditions, it is considered 

appropriate to derive an estimate of dermal absorption based on the results from the low dose 

group (10 μg/cm2

), since percent dermal absorption was greatest at this dose level. Based on the 

likely worker exposure time frame, it is considered most appropriate to adopt the dermal 

absorption value calculated for the group of animals for which the skin site was washed after 8 

hours. Mean dermal absorption for this group of animals was 43.55%. (TXR 0054866 and/or 

MRID 47430503)

4.3 Toxicological Effects

In subchronic and chronic oral studies in rats, dogs and mice, signs of mild regenerative 

hemolytic anemia were consistently observed in all three species. These signs frequently 

included decreased erythrocyte counts, decreased hemoglobin, decreased hematocrit, increased 

reticulocyte counts, increased hemosiderosis in the spleen, liver and/or bone marrow, 

extramedullary hematopoiesis in the spleen, and increased spleen weights in both males and 

females. A compensatory response (increased erythrocyte production) regularly followed the 

initial anemia. Additional toxic effects observed in these same studies included decreases in body 

weight, body weight gain and/or food consumption. No other significant treatment-related effects 

of toxicological concern were observed in these subchronic and chronic oral studies. In a 28-day 

dermal study in rats, no systemic or dermal effects were observed at dose levels up to 1000 

mg/kg/day, the limit dose. No neurotoxic effects were observed at any dose in a subchronic 

neurotoxicity study in rats.

Treatment-related developmental malformations, anomalies and variations were observed in a 

developmental toxicity study in rats at or below the no observable adverse effect level (NOAEL)

for maternal toxicity. At the highest dose tested in this study (400 mg/kg/day), both maternal 

toxicity (hemorrhagic perineal discharge) and considerable developmental toxicity (including 

total litter resorptions, fetal malformations, anomalies and variations) were observed. The fetal 
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malformations noted at this dose included treatment-related effects on nervous system tissues 

(hydrocephaly, craniorachisis and anophthalmia/ microphthalmia). At the next lower dose tested 

(200 mg/kg/day), treatment-related visceral malformations and skeletal variations were 

demonstrated in the absence of significant maternal toxicity. A similar increased sensitivity of 

fetuses or pups (as compared to adults) was not observed in a developmental toxicity study in 

rabbits or in 2-generation and 1-generation (range-finding) studies in rats. In a dermal 

developmental toxicity study in rats, no maternal or developmental toxicity was observed at dose 

levels up to 500 mg/kg/day, the highest dose tested.

In a battery of mutagenicity studies, results were negative in all studies except in an in vitro

chromosome aberration study in Chinese hamster ovary (CHO) cells, in which there was 

evidence of a clastogenic response in the absence of S-9 activation. 

In a 2-year chronic toxicity/carcinogenicity study in rats and an 18-month carcinogenicity study 

in mice, acibenzolar-S-methyl was negative for carcinogenicity when administered at dose levels 

adequate for the testing of carcinogenic potential. 

Acibenzolar-S-methyl showed no significant toxicity in a battery of acute toxicity tests (Toxicity 

Category III or IV in all tests). Considerable skin sensitizing (contact allergenic) potential was 

demonstrated in a dermal sensitization study in guinea pigs. The formulated end-use product 

(ActigardTM 50 WG) also demonstrated no significant acute toxicity; additionally, the end-use 

product did not show dermal sensitization in guinea pigs.

The complete toxicity profile for acibenzolar-S-methyl is provided in Appendix A. 

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

The FQPA factor for increased susceptibility to infants and children is reduced to 1x based on 

the following considerations. The toxicology database for acibenzolar-S-methyl is complete and 

adequate for assessing increased susceptibility under FQPA. The pre- and postnatal toxicity 

database for acibenzolar-S-methyl includes developmental toxicity studies in rats and rabbits, a 

DNT study in rats, and a two-generation reproduction toxicity study in rats. Based on the 

developmental toxicity in rats and the developmental neurotoxicity studies in rats, there is 

concern for increased qualitative and/or quantitative susceptibility following in utero exposure to 

acibenzolar-S-methyl. However, the degree of concern for the increased susceptibility seen in 

these studies is low, as there are no residual uncertainties with regard to pre- and/or postnatal 

toxicity since (1) NOAELs and LOAELs have been identified for all effects of concern, (2) a 

clear dose response has been well defined, and (3) the points of departure (PODs) selected for 

risk assessment are protective of the fetal/offspring effects. Additionally, the dietary and 

residential risk assessments are conservative and will not underestimate dietary exposure, and

there are no residual uncertainties in the exposure database. Further discussion may be found in 

the following sections.
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4.4.1 Completeness of the Toxicology Database

The toxicity database for acibenzolar-S-methyl is sufficient for a full hazard evaluation and is 

considered adequate to evaluate risks to infants and children. Acceptable studies are available for 

developmental, reproduction, developmental, subchronic neurotoxicity and immunotoxicity.

4.4.2 Evidence of Neurotoxicity

In a developmental neurotoxicity study, a maternal LOAEL was not observed. The maternal 

NOAEL is 326 mg/kg/day, the highest dose tested. No treatment-related offspring effects were 

seen on survival, clinical signs, FOB, developmental land marks, brain weights or 

neuropathology. No conclusions can be drawn on the effects of the compound on motor activity 

due to the lack of consistency in the observations. Significant morphometric changes (decreased 

thickness of the molecular layer of the cerebellum) were observed in male offspring on PND 63 

at 82 mg/kg/day. At the high dose, treatment-related offspring effects included decreased body 

weights, increased auditory startle response and increased thickness in the corpus callosum in 

females. In a subchronic neurotoxicity study in rats, no compound-related effects were observed

in the FOB, motor activity, gross pathology or neuropathology at the highest doses (575/628 

mg/kg/day, M/F) tested.

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

In the rat developmental toxicity study treatment related visceral malformations and skeletal 

variations were observed in fetuses at 200 mg/kg/day, the NOAEL for maternal toxicity. In the 

developmental neurotoxicity study, offspring toxicity was observed at 82 mg/kg/day while no 

maternal toxicity was observed at 326 mg/kg/day, the highest dose tested. Additional 

developmental toxicity studies in rats and rabbits and reproduction studies in rats provided no 

indication of increased susceptibility of rat or rabbit fetuses or neonates compared to adult 

animals.

4.4.4 Residual Uncertainty in the Exposure Database

There are no residual uncertainties in the exposure database. The refined acute dietary 

assessment utilizes maximum percent crop treated estimates but is still considered conservative, 

since it is based on field trial data evaluating samples taken at the shortest preharvest interval and 

treated at the maximum use rate. The chronic dietary and residential risk assessments are also 

conservative. These assessments will not underestimate dietary and/or non-dietary residential 

exposure to acibenzolar-S-methyl.
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4.5 Toxicity Endpoint and Point of Departure Selections

Toxicity endpoints and points of departure (PODs) for dietary (food and water), occupational, 

and residential exposure scenarios are summarized below. A detailed description of the studies 

used as a basis for the selected endpoints is presented in Appendix A.

4.5.1 Dose-Response Assessment

An acute POD of 8.2 mg/kg/day (NOAEL) was selected for females 13-49 years old and children

1-12 years old from a developmental neurotoxicity study in rats based on changes in brain 

morphometrics in the cerebellum at the LOAEL of 82 mg/kg/day. An uncertainty factor (UF) of 

100x (10x to account for interspecies extrapolation and 10x for intraspecies variation) was 

applied to the NOAEL to obtain an acute reference dose (aRfD) of 0.082 mg/kg/day. Since the 

FQPA factor has been reduced to 1X, the acute population adjusted dose (aPAD) is equivalent to 

the aRfD. The developmental neurotoxic effects of concern are presumed to occur after a single 

exposure and are relevant to females aged 13-49 years old since they occur in utero and to young 

children based on post-natal effects. No acute endpoint was appropriate for adults.

[Note: Based on a reevaluation of the DNT study regarding the potential for post-natal toxicity, 

the acute dietary analysis has been revised to include only females 13-49 years old and children

1-12 years old.]

A chronic POD of 8.2 mg/kg/day (NOAEL) was selected for females 13-49 and young children 

years old from a developmental neurotoxicity study in rats based on changes in brain 

morphometrics in the cerebellum at the LOAEL of 82 mg/kg/day. A UF 100x (10x to account for 

interspecies extrapolation and 10x for intraspecies variation) was applied to the dose to obtain a 

chronic reference dose (cRfD/cPAD) of 0.082 mg/kg/day. The effects observed in this study can 

occur after single or multiple doses. Selection of a chronic endpoint from this study ensures that 

the chronic exposure assessment is protective of females of reproductive age and their offspring. 

[Note: In earlier risk assessments (D361893, 3/3/09), only the subpopulation females 13-50 years 

old was assessed for chronic dietary exposure based on in utero effects observed in the DNT 

study. However, based on a reevaluation of the DNT study regarding the potential for post-natal 

toxicity, the chronic dietary analysis the chronic dietary exposure analysis has been revised to 

include an assessment of dietary risks to young children using the NOAEL from the DNT study 

for this and more recent previous assessments (D379425, 8/19/10).]

A chronic POD of 25 mg/kg/day (NOAEL) was selected for adult males and females (50+ years) 

based on hemolytic effects seen in a chronic dog study and other co-critical toxicity studies. A 

UF of 100x (10x to account for interspecies extrapolation and 10x for intraspecies variation) was 

applied to the dose to obtain a chronic reference dose (cRfD/cPAD) of 0.25 mg/kg/day. The 

NOAEL of 25 mg/kg/day, taken from the chronic dog study, is based on the totality of the 

database with a LOAEL of 105 mg/kg/day (the lowest LOAEL is from the reproduction study) 
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based on hemolytic anemia with compensatory response. The NOAEL and LOAEL 

recommended for use in the risk assessment come from different studies conducted in different 

species. Typically, a combination of NOAELs/LOAELs from studies conducted in different 

species is not recommended. However, in the case of acibenzolar-S-methyl, the same endpoint 

(hemolytic anemia) is observed across species at a relatively close range of LOAELs (105-312 

mg/kg/day). Therefore, the HED Toxicity Science Advisory Committee concluded that, in this 

instance, it would be appropriate to base the point of departure for the risk assessment on the 

NOAEL from the dog chronic toxicity study using the LOAEL from the reproduction study in 

rats for the basis of the endpoint (hemolytic anemia).

Short-term incidental oral and short- and intermediate term dermal and inhalation PODs of 8.2 

mg/kg/day were selected from the developmental neurotoxicity study in rats. The selected 

endpoint is protective of offspring effects from dermal exposure. Two acceptable dermal toxicity 

studies, including a dermal developmental study are available. However since neurological 

effects observed in the oral developmental neurotoxicity study are not measured in the dermal 

studies, the findings from these studies may not be protective of neurological effects. A dermal 

absorption factor (DAF) is applied when dermal exposure endpoints are selected from oral 

toxicity studies. The dermal factor converts the oral dose to an equivalent dermal dose for the 

risk assessment. A dermal absorption factor of 44% was used for the dermal exposure 

assessment based on a dermal absorption study in rats. An MOE of 100 is required for incidental 

oral, dermal and inhalation exposure scenarios based on the conventional uncertainty factor of 

100 (10x for interspecies extrapolation and 10x for intraspecies variation).

4.5.2 Recommendation for Combining Routes of Exposures for Risk Assessment

Risk assessment must consider exposures from three major sources: oral, dermal, and inhalation 

exposures. In the case of acibenzolar-S-methyl; incidental oral, dermal, and inhalation exposure 

routes may be combined where appropriate since the same toxicity study and effects were chosen 

to evaluate all three exposure routes.

4.5.3 Cancer Classification and Risk Assessment Recommendation

Acibenzolar-S-methyl has been designated by HED as “Not Likely to be Carcinogenic to 

Humans” in accordance with the 2005 EPA Guidelines for Carcinogenic Risk Assessment based 

on negative carcinogenicity studies in rats and mice and on generally negative mutagenicity 

studies.

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

Assessment

Toxicological doses/endpoints selected for the acibenzolar-S-methyl risk assessment are 

provided in Tables 4.5.4a and 4.5.4b.
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The acute endpoint (8.2 mg/kg/day) was derived from the developmental neurotoxicity study 

(DNT) based on changes in brain morphometrics in the cerebellum. The developmental 

neurological effects of concern are presumed to occur after a single exposure and are relevant to 

females aged 13-49 years old since they occur in utero and to young children based on post-natal 

effects. 

Also the same endpoint was applied for chronic endpoint for females age 13-49 and young 

children. The effects observed in this DNT study can occur after single or multiple doses. 

Selection of a chronic endpoint from this study ensures that the chronic exposure assessment is 

protective of females of reproductive age and their offspring.

This endpoint was not relevant for adult males and females 50+ years, so a different endpoint 

was selected for this population.

Table 4.5.4a. Summary of Toxicological Doses and Endpoints for Acibenzolar-S-methyl for 

Use in Dietary Human Health Risk Assessments

Exposure/

Scenario

Point of 

Departure

Uncertainty/

FQPA Safety 

Factors

RfD, PAD, 

LOC for Risk 

Assessment

Study and Toxicological Effects

Acute Dietary 

(Females 13-

49 years old & 

children 1-12 

years old)

NOAEL = 8.2 

mg/kg/day

UFA= 10x

UFH=10x

FQPA SF= 1x

Acute RfD = 

0.082 

mg/kg/day

aPAD = 0.082 

mg/kg/day

Developmental Neurotoxicity Toxicity - Rat 

Developmental LOAEL = 82 mg/kg/day 

based on changes in brain morphometrics in 

the cerebellum in offspring. 

Maternal LOAEL = was not observed 

NOAEL = 326.2 mg/kg/day HDT

Chronic 

Dietary 

(Females 13-

49 years old & 

children 1-12 

years old)

NOAEL = 8.2 

mg/kg/day

UFA= 10x.

UFH=10x

FQPA SF= 1x

Chronic RfD = 

0.082 

mg/kg/day

cPAD = 0.082 

mg/kg/day

Developmental Neurotoxicity Toxicity - Rat 

Developmental LOAEL = 82 mg/kg/day 

based on changes in brain morphometrics in 

the cerebellum in offspring. 

Maternal LOAEL = was not observed 

NOAEL = 326.2 mg/kg/day HDT

Chronic 

Dietary 

(Adult males 

and females 

50+ yrs.)

NOAEL = 25 

mg/kg/day

UFA= 10x

UFH=10x

FQPA SF= 1x

Chronic RfD = 

0.25

mg/kg/day

cPAD = 0.25 

mg/kg/day

Chronic Toxicity - Dog; Co-critical; 

Chronic/Cancer - Rat & Mouse, 

Reproduction Toxicity - Rat 

LOAEL = 105 mg/kg/day based on hemolytic 

anemia with compensatory response. 

Incidental Oral NOAEL= 8.2 

mg/kg/day

UFA= 10x

UFH=10x

Occupational 

LOC for MOE = 

100

Developmental Neurotoxicity Toxicity - Rat 

Developmental LOAEL = 82 mg/kg/day 

based on changes in brain morphometrics in 

the cerebellum in offspring. 

Maternal LOAEL = was not observed 

NOAEL = 326.2 mg/kg/day HDT

Cancer (all 

routes)

A “not likely” human carcinogen

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 
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effect level. UF = uncertainty factor. UFA = extrapolation from animal to human (interspecies). UFH = potential variation in sensitivity among members of the 

human population (intraspecies). UFL = use of a LOAEL to extrapolate a NOAEL. UFS = use of a short-term study for long-term risk assessment. UFDB = to 

account for the absence of key date (i.e., lack of a critical study). FQPA SF = FQPA Safety Factor. PAD = population adjusted dose (a = acute, c = chronic). RfD = 

reference dose. MOE = margin of exposure. LOC = level of concern. N/A = not applicable.

Table 4.5.4b. Summary of Toxicological Doses and Endpoints for Acibenzolar-S-methyl for 

Use in Occupational Human Health Risk Assessments

Exposure/

Scenario

Point of 

Departure

Uncertainty 

Factors

LOC for 

Risk 

Assessment

Study and Toxicological Effects

Dermal Short 

(1-30 days) and 

Intermediate (1-

6 months) Term

DAF = 44%

NOAEL= 

8.2 

mg/kg/day

UFA= 10x

UFH=10x

Occupational 

LOC for MOE = 

100

Developmental Neurotoxicity Toxicity - Rat 

Developmental LOAEL = 82 mg/kg/day 

based on changes in brain morphometrics in 

the cerebellum in offspring. 

Maternal LOAEL = was not observed 

NOAEL = 326.2 mg/kg/day HDT

Inhalation Short 

(1-30 days) and 

Intermediate (1-

6 months) Term

NOAEL= 

8.2 

mg/kg/day

UFA= 10x

UFH=10x

Occupational 

LOC for MOE = 

100

Developmental Neurotoxicity Toxicity - Rat 

Developmental LOAEL = 82 mg/kg/day 

based on changes in brain morphometrics in 

the cerebellum in offspring. 

Maternal LOAEL = was not observed 

NOAEL = 326.2 mg/kg/day HDT

Cancer (all 

routes)

A “not likely” human carcinogen

DAF = Dermal Absorption Factor. Since no inhalation absorption data are available, toxicity by the inhalation route is considered to be 

equivalent to the estimated toxicity by the oral route of exposure (100% absorption factor). 

5.0 Dietary Exposure and Risk Assessment 

5.1 Metabolite/Degradate Residue Profile

5.1.1 Summary of Plant and Animal Metabolism Studies

Adequate metabolism studies with [phenyl-U14C]acibenzolar-S-methyl on lettuce, tomato, rice, 

wheat, and tobacco have previously been submitted and reviewed. The metabolic pathway for 

acibenzolar-S-methyl was similar in all tested crops and involves the hydrolysis of the S-methyl 

ester to form the carboxylic acid metabolite (CGA-210007). Further hydroxylation of CGA210007 at the C-4 and C-5 positions results in the formation of the minor metabolites CGA324041 (all crops tested) and CGA-323060 (lettuce and tomato), which may also form acyl sugar 

conjugates. 

The nature of the residue in livestock is adequately understood based on recently submitted goat 

and hen metabolism studies. These metabolism studies demonstrated very low transfer of 

residues to milk, egg and muscle tissue (≤0.013 ppm TRR) from highly exaggerated feeding 

levels. The metabolic pathway for acibenzolar-S-methyl involves the hydrolysis of the S-methyl 
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ester to form the carboxylic acid metabolite, benzo(1,2,3)thiadiazole-7-carboxylic acid (CGA210007), which is the main component of the residue in milk, egg and tissues. CGA-210007 

may be subsequently conjugated; however, these conjugates were only minor components of the 

residues with the exception of the glycine conjugate (MET-2U) in milk and unidentified 

conjugates/metabolites in goat muscle and egg whites which were hydrolyzed to CGA-210007 

with 6N HCl at 100° C for 16 hours. No residues of parent were found in milk, egg and tissues.

5.1.2 Summary of Environmental Degradation

Laboratory and field studies indicate that acibenzolar-S-methyl does not have a high potential to 

leach to ground water or move to surface water based on its short resident times in soil and soil 

water. The major degradate observed was benzo[1,2,3]thiadiazole-7-carboxylic acid (CGA 

210007) in the hydrolysis and soil photolysis studies (up to 100 percent). CGA-210007 has a 

longer soil residence time, lower Freundlich Kd adsorption values, and is much more water 

soluble than acibenzolar-S-methyl, thereby exhibiting greater potential than the parent for lateral 

or vertical movement after application. Acibenzolar-S-methyl mainly degrades by photolysis and 

microbial action. Aqueous and soil photolysis irradiated half lives for parent are 0.6 hours and 1 

day, respectively. The aerobic soil metabolism, anaerobic aquatic metabolism and aerobic 

aquatic half lives are 5.3 hours, 4.0 and < 1 day(s) respectively. Field dissipation half-lives 

ranged from < 1 to 27 days. Under aerobic soil, aerobic aquatic, and anaerobic aquatic 

conditions, acibenzolar quickly degrades to CGA 210007. CGA 210007 is in its anionic form at 

environmentally significant pH’s (pH 6-9) and appears to be more soluble than its parent, 

although measured at much lower pH’s (approx. 225 ppm at 250OC pH 3.6-3.8 v. 7.7 ppm at 

250OC pH 7.5-7.9). CGA 210007 has longer resident field times than parent (aerobic soil halflife at 16.5 days) and, based on the batch equilibrium and aged soil column leaching studies, is 

considerably more mobile. Acibenzolar is not considered likely to bioaccumulative. 

5.1.3 Comparison of Metabolic Pathways

CGA 210007 represented the vast majority of the urinary radioactivity in the rat metabolism 

study and is therefore part of the total toxic mammalian exposure. CGA 210007 was also the 

principal metabolite in plant studies. As noted below, residues of the 4- and 5-hydroxy 

metabolites (CGA-324041 and CGA-323060) of CGA-210007 should be considered to be of 

equivalent toxicity to that of the parent compound acibenzolar-S-methyl.

5.1.4 Residues of Concern Summary and Rationale

The HED Metabolism Assessment Review Committee (MARC) determined that the residues of 

concern in plants for tolerance enforcement are residues convertible to benzo(1,2,3)thiadiazole7-carboxylic acid (CGA-210007), expressed as acibenzolar-S-methyl. For purposes of risk 

assessment, residues of the 4- and 5-hydroxy metabolites (CGA-324041 and CGA-323060) of 

CGA-210007 should also be considered. For this purpose, the toxicity of CGA-324041 and 

CGA-323060 should be considered to be equivalent to that of the parent compound acibenzolarS-methyl. These residues occur in significant quantities in lettuce and tomato. At this time, 
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acibenzolar-S-methyl does not have common metabolites with other agrochemicals. The 

residues of concern for drinking water are the same as those listed in the tolerance expression; 

that is, residues convertible to CGA-210007.

The residues of concern for drinking water are the same as those listed in the tolerance 

expression; that is, residues convertible to CGA-210007.

Based on the available metabolism data, the current acibenzolar-S-methyl risk assessment team 

has determined that the residues of concern in livestock for tolerance enforcement are residues of 

acibenzolar-S-methyl and its hydrolysis metabolite, benzo(1,2,3)thiadiazole-7-carboxylic acid 

(CGA-210007), expressed as acibenzolar-S-methyl. In addition residues of concern for risk 

assessment should include residues convertible to CGA-210007 for ruminant muscle and egg and 

the glycine conjugate of CGA-210007 (MET-U2) for milk. No livestock feeding studies have 

been submitted for acibenzolar-S-methyl and none are needed for the current petition since, 

based on the available data, there is no reasonable expectation of finite residues in livestock 

commodities for currently registered and proposed uses of acibenzolar-S-methyl. However, 

feeding studies might be required to support future uses (i.e., more likely foliar uses rather than 

soil uses) if livestock dietary burdens for acibenzolar-S-methyl increase significantly. In that 

event, only residues of parent and CGA-210007 need to be determined in milk, egg and tissues. 

Other residues of concern for risk assessment could be estimated from the available metabolism 

data.

Table 5.1.4 provides a summary of the MARC decisions regarding plant residues of concern for 

acibenzolar-S-methyl.

Table 5.1.4. Summary of MARC Decisions for Acibenzolar-S-methyl

Matrix Residues of Concern 1

For Risk Assessment For Tolerance Expression

Plants2 Residues of acibenzolar-S-methyl, benzo(1,2,3) 

thiadiazole-7-carbothioic acid-S-methyl ester, 

convertible to benzo(1,2,3)thiadiazole-7-carboxylic acid 

(CGA-210007), expressed as acibenzolar-S-methyl &

4-hydroxy CGA-210007 (CGA-323060)

5-hydroxy CGA-210007 (CGA-324041)

Residues of acibenzolar-S-methyl, 

benzo(1,2,3) thiadiazole-7-carbothioic 

acid-S-methyl ester, convertible to 

benzo(1,2,3)thiadiazole-7-carboxylic 

acid (CGA-210007), expressed as 

acibenzolar-S-methyl

Livestock3 Residues of acibenzolar-S-methyl, benzo(1,2,3) 

thiadiazole-7-carbothioic acid-S-methyl ester and 

benzo(1,2,3)thiadiazole-7-carboxylic acid (CGA210007), expressed as acibenzolar-S-methyl & 

For ruminant muscle and egg, residues convertible to 

CGA-210007

For milk, the glycine conjugate of CGA-210007 (METU2)

Residues of acibenzolar-S-methyl, 

benzo(1,2,3) thiadiazole-7-carbothioic 

acid-S-methyl ester and 

benzo(1,2,3)thiadiazole-7-carboxylic 

acid (CGA-210007), expressed as 

acibenzolar-S-methyl

1 The residues of concern for drinking water are the same as those listed in the tolerance expression

2 If a future petition is received for rice, residues of CGA-379019 should be included in the risk assessment 3 No reasonable expectation of finite residues, i.e., Category 3 of 40CFR 180.6(a) for currently registered and proposed uses.
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5.2 Food Residue Profile

5.3 Water Residue Profile

Drinking water residues provided by the Environmental Fate and Effects Division (EFED) 

(D427617, C. Koper, 6/4/15) were incorporated directly into the acute and chronic dietary 

analyses. Surface water EDWCs were generated for the total residues of acibenzolar-S-methyl

and CGA 210007 using the Pesticide Root Zone Model/Exposure Analysis Modeling System 

(PRZM/EXAMS) model for all proposed uses. Exposure in ground water due to leaching was 

assessed with the Pesticide Root Zone Model for Ground Water (PRZM-GW) model. 

For surface water, the EDWCs for the citrus and pome fruit scenarios modeled in this new use 

assessment (Table 5.3) did not exceed the EDWCs reported in a previous drinking water 

assessment to support an Experimental Use Permit (D392519, R. Miller, 12/13/11) dated 13 

December 2011. It is important to note, however, that the recommended EDWCs were revised

using the current PCA adjustment factor of 0.91 for agricultural uses according to recently 

implemented PCA guidance and incorporating the TTR approach (previous recommended 

chronic values were for CGA-210007 only). Therefore, the recommended EDWCs for surface 

water include the acute concentration of 47.19 μg/L (citrus), and the annual mean concentration 

of 13.33 μg/L (apple) for the chronic analysis. 

For ground water, four applications at 0.1 lbs. a.i./acre for a maximum yearly application rate of 

0.4 lbs a.i/A were modeled for citrus and pome fruit using PRZM-GW to determine drinking 

water exposure in ground water based on the Actigard® 50 WG (EPA Reg. No.100-922) label.

Table 5.3. Recommended EDWCs for Acibenzolar–S-methyl following the Total Toxic Residue 

(TTR) Approach

Drinking Water Source Crop Scenario 1-in-10 year 

acute (μg/L)

1-in-10 year 

chronic (μg/L)

30- year average 

(μg/L)

Surface Water FL Citrus 1 47.19 -- --

PA Apple1 -- 13.33 8.45

Ground Water WI Corn Scenario

Central Sand Region2

(Pome Fruit use)

25.00 NA --

WI Corn Scenario

Central Sand Region

(Citrus use)

-- NA 22.70

1 Previously reported maximum EDWCs from Experimental Use Permit assessment generated using 

PRZM/EXAMS model for direct soil (citrus) and aerial (apple) applications (D392519, R. Miller, 12/13/11) 

with a revised PCA factor of 0.91. 

2 Highest EDWCs generated for New Use assessment using PRZM-GW model based on the maximum annual 

rate of 0.4 lbs a.i/A for Citrus and Pome Fruit (Actigard®50 WG (EPA Reg. No.100-922).

NA = not applicable 
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5.4 Dietary Risk Assessment

5.4.1 Description of Residue Estimates Used in Dietary Assessment

Acute and chronic aggregate dietary [food and drinking water] exposure and risk assessments were 

conducted using the Dietary Exposure Evaluation Model software with the Food Commodity 

Intake Database (DEEM-FCID) Version 3.16. This software uses 2003-2008 food consumption 

data from the U.S. Department of Agriculture’s (USDA’s) National Health and Nutrition 

Examination Survey, What We Eat in America, (NHANES/WWEIA).

In the chronic dietary exposure analysis, tolerance level residues were used and 100 percent crop 

treated was assumed for all commodities. DEEM default processing factors were used for apple 

juice, dried apples, cranberry juice, dried apple, dried pears, dried onion, dried banana, dried 

plantain, and dried tomato. A processing factor was not used for tomato paste because a separate 

tolerance has been established for this processed commodity. In the submitted tomato processing 

study (D246673, M. Doherty, 3/15/2000), processing factors of 1.0 and 2.9 were reported for 

tomato juice and tomato puree, respectively. These processing factors were used in the dietary 

exposure assessment. Residues of acibenzolar-S-methyl did not concentrate in citrus juice or oil 

based on a processing study, so a processing factor of 1.0 was used.

 

Available lettuce metabolism data for a 7-day PHI were used to determine the relative abundance 

of the hydroxy metabolites (CGA-323060 and CGA-324041) and residues convertible to the 

carboxylic acid metabolite (CGA-210007). Based on the lettuce metabolism data, a factor of 1.5x 

was applied to estimates of acibenzolar-S-methyl residues to account for all of the residues of 

concern for dietary risk (including CGA-210007, CGA-323060 and CGA-324041). Lettuce 

metabolism data are provided in Table 5.4.1. 

Table 5.4.1. Lettuce metabolism data (Washed, 7-day PHI)

Compound ppm Residues

Acibenzolar-S-Methyl 0.171

CGA-210007 0.255

CGA-323060 0.204

CGA-324041 0.006

Total Identified 0.636

1.5x = 0.636 / (0.171+0.255)

Residues Used in the Acute Analysis

A probabilistic assessment was performed for the acute analysis (D246852, D. McNeilly, 

7/28/15). Foods were classified as blended, partially blended, or nonblended based on guidance 

given in the Draft DEEM-FCID Classification of Food Forms with Respect to Level of Blending 

(F. Fort). The acute analysis assumed a distribution of residues based on field trial data for 

nonblended and partially blended commodities. For blended commodities, the mean field trial 
Acibenzolar-S-Methyl Human Health Risk Assessment DP No. 424596

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values were used as a point estimate. A value of 1⁄2 LOQ was used for samples that contained less 

than LOQ residues. Time-limited tolerance values were used (0.05 ppm) for the EUP 

commodities, i.e., apple, pear, and grapefruit. Section 3 tolerance-level residues were used for all 

other citrus and pome fruit commodities. DEEM default processing factors were used for apple 

juice, cranberry juice, dried apples, dried pears, dried onion, dried banana, dried plantain, and 

dried tomato. Empirical processing factors were used for citrus juice (1.0), tomato paste (7.1), 

tomato puree (2.9), and tomato juice (1.0). Residues of acibenzolar-S-methyl did not concentrate 

in citrus juice or oil. The acute analysis used available maximum percent crop treated estimates

from the Biological and Economic Analysis Division’s (BEAD’s) screening-level analysis (Dec 

6, 2012). If no percent crop treated data were available, 100% crop treated was assumed. As 

previously noted, a factor of 1.5X was applied to the estimate of residues convertible to CGA210007 for all commodities to account for all of the residues of concern for dietary risk.

5.4.2 Percent Crop Treated Used in Dietary Assessment

Acute Analysis 

The acute analysis used available maximum percent crop treated estimates from the Biological 

and Economic Analysis Division’s (BEAD’s) screening-level analysis (Dec 6, 2012). The 

following maximum percent crop treated estimates were used in the acute dietary risk assessment 

for the following crops that are currently registered for acibenzolar-S-methyl: broccoli: 10%; 

cabbage: 2.5%; cauliflower: 10%; lettuce: 10%; peppers: 10%; spinach: 50; and tomatoes: 10%. 

If no percent crop treated data were available 100% crop treated was assumed.

Chronic Analysis

100% percent crop treated estimates were used in the chronic dietary risk assessment.

5.4.3 Acute Dietary Risk Assessment

A refined (probabilistic) acute dietary exposure analysis was performed for the general 

population and all population subgroups. The acute analysis assumed time-limited tolerance level 

values (since the EUP is still active) for apple, pear, and grapefruit. The Section 3 HEDrecommended tolerance levels are used for all other Crop Group 10-10, and Pome Crop Group 

11-10 commodities. Maximum screening-level percent crop treated estimates were used for 

commodities for which data were available. If no percent crop treated data were available, 100% 

crop treated was assumed. The acute analysis incorporated the 1 in 10 year peak surface drinking 

water estimate from application of acibenzolar-S-methyl to citrus in FL. Acute dietary risk 

estimates are not of concern for females 13-49 years old, or children 1-12 years old. The 

subgroup with the highest risk estimate was children 1-2 years old with an exposure estimate of 

33% of the acute population adjusted dose (aPAD) at the 99.9th percentile of exposure. The 

percent aPAD for females 13-49 years old was 14% at the 99.9th percentile of exposure. 
Acibenzolar-S-Methyl Human Health Risk Assessment DP No. 424596

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Table 5.4.3: Summary of Acute Dietary Exposure and Risk (Food and Water) for Acibenzolar-S-Methyl

Population Subgroup aPAD (mg/kg/day) Acute (99.9th Percentile)

Exposure (mg/kg/day) % aPAD

Females 13-49 years old

0.082

0.011114 14

All Infants (< 1 year old) 0.019436 24

Children 1-2 years old 0.027120 33

Children 3-5 years old 0.025341 31

Children 6-12 years old 0.019608 24

5.4.4 Chronic Dietary Risk Assessment

A conservative chronic dietary exposure analysis was performed for the general U.S. population 

and various population subgroups. Tolerance level residues and 100% crop treated assumptions 

were used. Temporary tolerance values were used for apple, pear, and grapefruit, since they are 

higher that the new Section 3 tolerances, and do not expire until 12/31/2015. Section 3 tolerance 

levels are used for all other crop group 10-10, and pome crop group 11-10 commodities. DEEM 

default and empirical processing factors were used to modify the tolerance values. The chronic 

analysis incorporated the 1 in 10 year annual average surface drinking water estimate from 

application of acibenzolar-S-methyl to apples in Pennsylvania. The population subgroups 

females 13-49 and young children had a more protective chronic population adjusted dose 

(cPAD, 0.082 mg/kg/day) than the general U.S. population and all other population subgroups 

(0.25 mg/kg/day). Chronic dietary risk estimates are not of concern for general population or 

other population subgroups. The subgroup with the highest risk estimate was children 1-2 years 

old with a cPAD of 13%. The estimated cPAD for the general U.S. population was 2%.

The results of the chronic dietary exposure analysis are reported in Tables 5.4.4.a and 5.4.4.b. 

Table 5.4.1a: Summary of Chronic Dietary Exposure and Risk to Female (13-49) and Young Children 

Population for Acibenzolar-S-Methyl 

Population Subgroup cPAD (mg/kg/day)

Chronic

Exposure (mg/kg/day) % cPAD

Females 13-49 years old

0.082

0.003547 4.3

All Infants (< 1 year old) 0.005266 6.4

Children 1-2 years old 0.010647 13

Children 3-5 years old 0.009355 11

Children 6-12 years old 0.005724 7.0

Table 5.4.4.b: Summary of Chronic Dietary Exposure and Risk to Adults 50+ and Adult Males (13+) for 

Acibenzolar-S-Methyl

Population Subgroup cPAD (mg/kg/day) Chronic

Exposure (mg/kg/day) % cPAD

General U.S. Population

0.25

0.004189 1.7

Youth 13-19 0.003304 1.3

Adults 20-49 0.003562 1.4

Adults 50-99 years old 0.003522 1.4
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6.0 Residential (Non-Occupational) Exposure/Risk Characterization

There are no residential uses associated with this action, however, a revised postapplication 

residential exposure assessment was conducted to update the residential exposures based on the 

2012 revised Residential SOPs.

6.1 Residential Post-Application Exposure

There is the potential for post-application exposure for individuals exposed as a result of being in 

an environment that has been previously treated with acibenzolar-S-methyl. The quantitative 

exposure/risk assessment for residential post-application exposures is based on the following 

scenarios: Adult, 11 to <16 years old, and 6 to <11 years old dermal exposure from playing golf 

on treated lawn.

Short-term dermal exposure and risk estimates are summarized in Table 6.1. All assessed 

scenarios resulted above the LOC and therefore, are not of concern to HED (i.e. an MOE > 100). 

MOEs ranged from 21,000 to 25,000.

Table 6.1. Residential Post-application Non-cancer Exposure and Risk Estimates for Acibenzolar-S-Methyl.

Lifestage

Post-application Exposure 

Scenario Application 

Rate1 Dose (mg/kg/day)2 MOEs3

Use Site Route of Exposure

6 to <11 years

Golfing Dermal 0.022

0.00039 21,000

Adult &

11 to <16 years 0.00033 25,000

1 Based on registered or proposed label (Reg. No. 100-1364). 2 Dose (mg/kg/day) equations provided in Appendix A.

3 MOE = POD (mg/kg/day) ÷ Dose (mg/kg/day). 4 Combined MOE = 1 ÷ (1/dermal MOE) + (1/incidental oral MOE), where 

applicable.

In accordance with 40CFR158, TTR data are required for all occupational (e.g., sod farms, golf 

courses, parks, and recreational areas) or residential turf uses that could result in post-application 

exposure to turf. EPA is waiving the 40CFR TTR data requirement since the estimated 

residential turf post-application exposure for residential turf using default TTR values for 

acibenzolar-S-methyl is minimal in comparison to the level of concern (i.e., the calculated MOE 

is greater than 10 times higher than the level of concern, MOE = 21,000 compared to the LOC of 

100). In this instance, it is unlikely that chemical-specific TTR data would be needed to further 

refine exposure assessments or would add appreciably to our general understanding of the 

availability of turf transferable pesticide residues.

6.2 Residential Bystander Post-application Inhalation Exposure

Volatilization of pesticides may be a source of post-application inhalation exposure to 

individuals nearby pesticide applications. The Agency sought expert advice and input on issues 
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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 has evaluated the SAP report and has developed a Volatilization Screening Tool and a 

subsequent Volatilization Screening Analysis 

(http://www.regulations.gov/#!docketDetail;D=EPA-HQ-OPP-2014-0219). During Registration 

Review, the Agency will use this analysis to determine if data (i.e., flux studies, route-specific 

inhalation toxicological studies) or further analysis is required for acibenzolar-S-methyl. 

6.3 Spray Drift

Spray drift is a potential source of exposure to those nearby pesticide applications. This is 

particularly the case with aerial application, but, to a lesser extent, spray drift can also be a 

potential source of exposure from the ground application methods (e.g., groundboom and 

airblast) employed for acibenzolar. The Agency has been working with the Spray Drift Task 

Force (a task force composed of various registrants which was developed as a result of a Data 

Call-In issued by EPA), EPA Regional Offices, and 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). 1

 The Agency has also developed a policy on how to 

appropriately consider spray drift as a potential source of exposure in risk assessments for 

pesticides. The potential for spray drift will be quantitatively evaluated for each pesticide during 

the Registration Review process which ensures that all uses for that pesticide will be considered 

concurrently. The approach is outlined in the revised (2012) Standard Operating Procedures for 

Residential Risk Assessment (SOPs) - Residential Exposure Assessment Standard Operating 

Procedures Addenda 1: Consideration of Spray Drift. This document outlines the quantification 

of indirect non-occupational exposure to drift.

6.4 Residential Risk Estimates for Use in Aggregate Assessment

Table 6.4 reflects the residential risk estimates that are recommended for use in the aggregate 

assessment for acibenzolar-S-methyl.

• The recommended residential exposure for use in the adult aggregate assessment reflects 

post-application dermal potential risk from playing golf on treated turf.

• The recommended residential exposure for use in the 11 to <16 years old aggregate 

assessment reflects post-application dermal potential risk from playing golf on treated 

turf.

• The recommended residential exposure for use in the 6 to <11 years old aggregate 

assessment reflects post-application dermal potential risk from playing golf on treated 

turf.

 
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Table 6.4. Recommendations for the Residential Exposures for the Acibenzolar-S-Methyl Aggregate Assessment.

Lifestage Exposure 

Scenario

Dose (mg/kg/day)1 MOE2

Dermal Inhal. Oral Total Dermal Inhal. Oral Total

6 to <11 years 

old

Golfing

0.00039

N/A N/A

0.00039 21,000

N/A N/A

21,000

Adult &

11 to <16 years 

old

0.00033 0.00033 25,000 25,000

1 Dose = the highest dose for each applicable lifestage of all residential scenarios assessed. Total = dermal + incidental oral. 

2 MOE = the MOEs associated with the highest residential doses. Total = 1 ÷ (1/Dermal MOE) + (1/Incidental Oral MOE).

7.0 Aggregate Exposure/Risk Characterization

In accordance with the FQPA, HED must consider and aggregate (add) pesticide exposures and 

risks 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 risks themselves can be aggregated. When 

aggregating exposures and risks from various sources, HED considers both the route and 

duration of exposure.

Acute and chronic aggregate exposures include food plus drinking water exposures only for 

acibenzolar-S-methyl. Acute and chronic aggregate risks are not of concern (see Section 5.4.3 

and 5.4.4 above).

7.1 Short- and Intermediate-Term Aggregate Risk

There is potential short-term exposure to acibenzolar-S-methyl via the dietary pathway (which is 

considered background exposure) and the residential pathway. Since the short- and 

intermediate-term PODs are the same and short-term exposure estimates are greater than their 

intermediate-term counterparts, the short-term aggregate risk assessment is protective of the 

intermediate-term aggregate exposure. 

The short-term aggregate exposure assessment for adults and for children 11 to < 16 years old 

includes dietary (food and drinking water) and dermal postapplication exposures. For each 

population group assessed, the most conservative scenario was chosen. 

Table 7.1. Short-Term Aggregate Risk Calculations - Residential Post-Application Exposure

Population 

Subgroup

NOAEL 

mg/kg/day LOC1

Average Food 

and Water 

Exposure 

mg/kg/day

Residential Exposure 

mg/kg/day2

Total 

Exposure 

mg/kg/day3

Aggregate 

MOE (food, 

water, and 

residential)4

Children 6 to <11 

years old

8.2 

mg/kg/day 100 0.005724 0.00039 0.006114 1300

Adult &

Children 11 to <16 

years old

8.2 

mg/kg/day 100 0.005724 0.00033 0.006054 1400
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1 Indicate in this footnote the basis for the LOC (include the standard inter- and intra- species uncertainty factors totaling 100, as 

well as additional uncertainty factors/safety factors as appropriate.)

2 Residential Exposure = Aggregate MOE = [NOAEL (8.2 mg/kg/day)/ (Avg Food & Water Exposure + Residential Exposure)]. 

Adult residential post-application exposure from golfer scenario. 3 Total Exposure = Avg Food & Water Exposure + Residential Exposure)

4 Aggregate MOE = [NOAEL / (Avg Food & Water Exposure + Residential Exposure)]

8.0 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 acibenzolar-S-methyl and any other substances, and acibenzolar-S-methyl does not appear to 

produce a toxic metabolite produced by other substances. For the purposes of this tolerance 

action, therefore, EPA has not assumed that acibenzolar-S-methyl 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/.

9.0 Occupational Exposure/Risk Characterization

D426853, I. Nieves, 8/13/2015

Syngenta submitted directions for use of acibenzolar-S-methyl on citrus and pome fruit 

formulated as a water dispersible granule (WDG) containing 50% acibenzolar-S-methyl as the 

sole active ingredient (Actigard® 50WG; EPA Reg. No. 100-922). Acibenzolar-S-methyl is 

proposed for multiple soil (i.e., drench, drip or micro-irrigation) or foliar applications on pome 

fruit, and for soil applications on citrus fruit.

 

The Personal Protective Equipment (PPE) statement on the proposed label requires applicators 

and other handlers to wear: long-sleeved shirt and long pants, chemical-resistant gloves, and

shoes plus socks.

The end use product may be applied through a variety of application methods including: aerial, 

chemigation, groundboom, airblast, backpack, and hand held equipment. There is a potential for 

occupational exposure associated with handler activities (i.e., mixing, loading, and applying) as 

well as with post-application activities (i.e., re-entering treated areas). No data on the number of 

exposure days per year was provided. Based on the proposed label’s use pattern and directions,

only short- (1 to 30 days) and intermediate-term (1 to 6 months) exposures are expected for 

handlers.

Dermal and inhalation exposures to workers are combined for acibenzolar-S-methyl because the 

toxicity endpoints for these exposure routes are based on common toxicological effects.
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9.1 Short- and Intermediate-Term Handler Risk Estimates

HED uses the term handlers to describe those individuals who are involved in the pesticide 

application process. HED believes that there are distinct job functions or tasks related to 

applications, and that exposures can vary depending on the specifics of each task. Job 

requirements (e.g., amount of chemical used in each application), types of equipment used, the 

area treated or amount handled, and the level of protection used by a handler can cause exposure 

levels to differ in a manner specific to each application event. Detailed descriptions of the 

handler assessment are available in D426853 (I. Nieves, 8/13/2015) and a summary table of the 

handler exposure and risk estimates is provided. The occupational hander exposure and risk 

estimates rely on generic data from the Pesticide Handlers Exposure Database Version 1.1 

(PHED 1.1), the Outdoor Residential Exposure Task Force (ORETF) database and the 

Agricultural Handler Exposure Task Force (AHETF) database.

The occupational handler exposure and risk estimates indicate that the short- and intermediateterm dermal and inhalation combined MOEs are not of concern to HED (i.e., MOE > 100) with 

label required PPE (i.e., single layer of clothing, gloves, and no respirator). MOEs were 

presented at baseline and with label required PPE (i.e., gloves). Combined MOEs at baseline 

ranged from 58 to 4,100 and with label-required PPE from 320 to 19,000.
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Table 9.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Acibenzolar-S-Methyl.

Exposure 

Scenario

Crop 

or 

Target

Level of 

Concern

Dermal Unit 

Exposure (μg /lb 

ai)1

Inhalation 

Unit 

Exposure 

(μg /lb ai)1

Maximum 

Application 

Rate2

Area 

Treated 

or 

Amount 

Handled 

Daily3

Dermal Inhalation Total

Baseline/Gloves No 

Respirator

Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day)6 MOE7 MOE8

Mixer/Loader

M/L of liquids 

to support 

chemigation 

applications

Pome 

crop 

group 

11-10 

and 

Citrus 

crop 

group 

10-10

100 Baseline: 220

Gloves: 51.6 8.96 0.1 lb ai/A

350 A Baseline: 0.051

Gloves: 0.012

Baseline: 160

Gloves: 710

0.00012 1800 Baseline: 150

Gloves: 510

M/L of liquids 

to support 

airblast 

applications 40 A Baseline: 0.0058

Gloves: 0.0013

Baseline: 1,400

Gloves: 

6,300

0.000014 16000 Baseline: 1,300

M/L of liquids Gloves: 4,500

to support 

groundboom 

applications

Applicator

Airblast Baseline: 1,770

Gloves: 1,590 4.71

0.1 lb ai/A

40 A Baseline: 0.045

Gloves: 0.041

Baseline: 180

Gloves: 200 0.00027 30,000 Baseline: 180Gloves: 200

Groundboom Baseline: 78.6

Gloves: 16.1 0.34 40 A Baseline: 0.0020

Gloves: 0.00041

Baseline: 4,100

Gloves: 20,000 0.000020 420,000 Baseline: 4,100

Gloves: 19,000

Mixer/loader/Applicator

Backpack Pome 

crop 

group 

11-10 

and 

Citrus 

crop 

100

Baseline/Gloves: 

8,260 2.58

0.01 lb 

ai/gallon

40 

gallons

Baseline/Gloves: 

0.021

Baseline/Gloves: 

390 0.000015 550,000Baseline/Gloves: 

390

Mechanicallypressurized 

Handgun

Baseline:1300

Gloves:390 3.9 1000 

gallons

Baseline:0.083

Gloves:0.025

Baseline:99

Gloves: 330 0.00057 15,000

Baseline:98

Gloves:320
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Table 9.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Acibenzolar-S-Methyl.

Exposure 

Scenario

Crop 

or 

Target

Level of 

Concern

Dermal Unit 

Exposure (μg /lb 

ai)1

Inhalation 

Unit 

Exposure 

(μg /lb ai)1

Maximum 

Application 

Rate2

Area 

Treated 

or 

Amount 

Handled 

Daily3

Dermal Inhalation Total

Baseline/Gloves No 

Respirator

Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day)6 MOE7 MOE8

group 

10-10

Loader/Applicator

Brush/Roller

Pome 

crop 

group 

11-10 

and 

Citrus 

crop 

group 

10-10

100

Baseline:180,000

Gloves:24,000 280 0.12 lb 

ai/gallon 1 gallon Baseline:0.083

Gloves:0.025

Baseline:58

Gloves: 430 0.00050 16,000

Baseline:58

Gloves:420

1 Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (March 2014); Level of mitigation: Baseline, PPE (i.e.,gloves).

2 Based on registered or proposed label (Reg. No. 100-922).

3 Exposure Science Advisory Council Policy #9.1.

4 Dermal Dose = Dermal Unit Exposure (μg /lb ai) × Conversion Factor (0.001 mg/μg ) × Application Rate (lb ai/acre or gal) × Area Treated or Amount Handled (A or gal/day) × DAF (44%) ÷ BW 

(69 kg).

5 Dermal MOE = Dermal NOAEL (mg/kg/day) ÷ Dermal Dose (mg/kg/day).

6 Inhalation Dose = Inhalation Unit Exposure (μg /lb ai) × Conversion Factor (0.001 mg/μg ) × Application Rate (lb ai/acre or gal) × Area Treated or Amount Handled (A or gal/day) ÷ BW (kg).

7 Inhalation MOE = Inhalation NOAEL (mg/kg/day) ÷ Inhalation Dose (mg/kg/day).

8 Total MOE = NOAEL (mg/kg/day) ÷ Dermal Dose + Inhalation Dose OR Total MOE = 1 ÷ (1/Dermal MOE + 1/Inhalation MOE).
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9.2 Short- and Intermediate-Term Post-Application Risk Estimates

9.2.1 Dermal Post-Application Risk Estimates

Occupational workers who enter treated fields to perform post-application activities such as hand 

weeding and scouting may be exposed to acibenzolar-S-methyl residues. Based on the use 

pattern, workers may be exposed to short- and intermediate-term exposure durations. 

Exposure Duration: HED classifies exposures from 1 to 30 days as short-term and exposures 30 

days to six months as intermediate-term. For acibenzolar-S-methyl, short- and intermediate-term

exposures are expected since the use directions allow multiple applications per season. In 

addition, the short- and intermediate-term PODs are the same; therefore, short-term risk 

estimates are protective of longer-term exposures.

Table 9.2.1 provides a summary of the anticipated post-application activities and associated 

transfer coefficients for the proposed crops/use sites.

Table 9.2.1. Anticipated Post-Application Activities and Dermal Transfer Coefficients.

Proposed Crops

Policy Crop 

Group 

Category

Crop 

Height

Foliage 

Density

Transfer 

Coefficients 

(cm2/hr)

Activities

Pome crop group 11-10 Tree, “fruit”, 

deciduous 

High Full 3,600 Thinning Fruit

High Full 1,400 Hand Harvesting

High/Low Full 580 Hand Pruning; Training

High Full/Min 580 Scouting

Low Min 230 Transplanting

High Full 100 Orchard Maintenance; Propping

High/Low Full 100 Hand Weeding

Citrus crop group 10-

10

Tree, “fruit”, 

evergreen

High Full 1,400 Hand harvesting

High Full 580 Pruning

High/Low Full 580 Scouting

Low Full/Min 230 Transplanting

High Full 100 Baiting/Trapping; Orchard 

Maintenance

High/Low Full 100 Hand Weeding
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Occupational Post-application Non-Cancer Dermal Risk Estimates

The short- and intermediate-term post-application exposure scenarios associated with the 

proposed uses for acibenzolar-S-methyl are summarized in Table 9.2.2. All scenarios resulted in 

MOEs greater than the LOC of 100 (ranging from 160 to 5,700) on day 0 (12 hours after 

application) and, therefore, are not of concern to HED.

Table 9.2.2. Occupational Post-application Non-Cancer Exposure and Risk Estimates for Acibenzolar-S-methyl.

Crop/Site Activities Transfer Coefficient 

(cm2/hr)

DFR1

(μg/cm2)

Dermal Dose 

(mg/kg/day)2 MOE3

Short-& Intermediate-term

Pome crop group 11-10 Thinning Fruit 3,600

0.28

0.052 160

Pome crop group 11-10 

& Citrus crop group 10-

10

Hand Harvesting 1400 0.020 410

Hand Pruning; 

Scouting; Training 

(Pome fruit);

580 0.083 990

Transplanting 230 0.0033 2,500

Orchard 

maintenance; 

Propping (Pome

fruit); 

Baiting/Trapping 

(Citrus)

100 0.0014 5,700

1 DFR = Application Rate × F × (1-D)t × 4.54E8 μg/lb × 2.47E-8 acre/cm2; where F = 0.25 and D = 0.10 per day OR 

2 Daily Dermal Dose = [DFR (μg/cm2

) × Transfer Coefficient × 0.001 mg/μg × 8 hrs/day × dermal absorption (44%)] ÷ BW (69 kg).

3 MOE = POD (mg/kg/day) / Daily Dermal Dose.

In accordance with 40 CFR 158, DFR data are required for all occupational (e.g., crop, nursery, 

greenhouse use sites) or residential (e.g., ornamental and vegetable gardens, pick your own 

farms, retail tree farms) uses that could result in post-application exposure to foliage. In the 

absence of chemical-specific DFR data, EPA uses default values. The 2012 Standard Operating 

Procedures for Residential Pesticide Exposure Assessment includes an analysis of a number of 

DFR studies, which resulted in the selection of a revised default values for the fraction of the 

application rate available for transfer after a foliar application (FAR). These values are based on 

an analysis of 19 DFR studies. Since that time, the ARTF has submitted information (MRID 

49299201) that corrects an application rate error made in the original submission of “ARF039 –

Determination of Dermal and Inhalation Exposure to Reentry Workers During Chrysanthemum 

Pinching in a Greenhouse” (EPA MRID 45344501). As a result, the range of FAR values was 

revised from 2-89% to 2-7%. In these data, a large range of transferability is observed and this 

variability can potentially be attributable to many factors such as active ingredient, formulation, 

field conditions in the studies, weather conditions (e.g., humidity), and many other difficult-toquantify factors. Although witnessed across multiple chemicals, this range in FAR values is not 

expected when considering DFR data for a single chemical. At this time, the ARTF submission 

did not alter the selection of 25% as the reasonable, high-end default value. Because DFR data 

are not available for acibenzolar-S-methyl, EPA is using the default value of 25%. Although 

there may be a small degree of uncertainty in the use of the default DFR value for acibenzolar-S-
Acibenzolar-S-Methyl Human Health Risk Assessment DP No. 424596

Page 35 of 58

methyl (i.e., there is a small chance that the FAR value may exceed the applicable default value), 

it is likely that the health-protective aspects of EPA’s occupational post-application assessment 

methodology will more than compensate for this potential uncertainty. For example, when 

assessing residential and occupational post-application exposure to gardens and ornamentals, 

EPA assumes the following: exposures occur to zero-day (i.e., day of application ) residues 

every day of the assessed exposure duration (i.e., EPA assumes that no dissipation or degradation 

occurs, it doesn’t rain, etc); individuals perform the same post-application activities performed in 

the transfer coefficient study day after day (e.g., weeding, harvesting, pruning, etc.); and 

individuals engage in these post-application activities for a high-end amount of time every day 

(represented by data reflecting time spent gardening based on survey data).

Given the conservatisms discussed above and the potential compounding nature of these 

conservatisms, EPA is able to rely upon the calculated exposure estimates with confidence that 

exposure is not being underestimated. However, since the highest estimated occupational postapplication exposure using default DFR values for acibenzolar-S-methyl is not minimal in 

comparison to the LOC (i.e., the calculated MOE is not greater than two times higher than the 

LOC, MOE = 160 compared to the LOC of 100); EPA is requiring the 40 CFR DFR data to 

facilitate any necessary exposure assessments refinements and to further EPA’s general 

understanding of the availability of dislodgeable foliar pesticide residues.

Restricted Entry Interval

The REI specified on the proposed label is based on the acute toxicity of acibenzolar-S-methyl. 

This active ingredient is classified as Toxicity Category III via the dermal route, Toxicity 

Category IV for skin irritation potential, and Toxicity Category III for eye irritation. It is a skin 

sensitizer. Short- and intermediate-term post-application risk estimates were not a concern on 

day 0 (12 hours following application) for all post-application activities. Under 40 CFR 156.208 

(c) (2) (iii), ai’s classified as Acute III or IV for acute dermal, eye irritation and primary skin 

irritation are assigned a 12-hour REI. Therefore, the [156 subpart K] Worker Protection 

Statement interim REI of 12 hours is adequate to protect agricultural workers from postapplication exposures to acibenzolar-S-methyl.

9.2.2 Inhalation Post-Application Risk Estimates

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 resuspension 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 has 

evaluated the SAP report and has developed a Volatilization Screening Tool and a subsequent 

Volatilization Screening Analysis (http://www.regulations.gov/#!docketDetail;D=EPA-HQOPP-2014-0219). During Registration Review, the agency will utilize this analysis to determine 
Acibenzolar-S-Methyl Human Health Risk Assessment DP No. 424596

Page 36 of 58

if data (i.e., flux studies, route-specific inhalation toxicological studies) or further analysis is 

required for acibenzolar.

In addition, the Agency is continuing to evaluate the available post-application inhalation 

exposure data generated by the Agricultural Reentry Task Force. Given these two efforts, the 

Agency will continue to identify the need for and, subsequently, the way to incorporate 

occupational post-application inhalation exposure into the Agency’s risk assessments.

Although a quantitative occupational post-application inhalation exposure assessment was not 

performed previously, an inhalation exposure assessment was performed for 

occupational/commercial handlers. Handler exposure resulting from application of pesticides 

outdoors is likely to result in higher exposure than post-application exposure. Therefore, it is 

expected that the handler inhalation exposure estimates previously assessed would be protective 

of most occupational post-application inhalation exposure scenarios.

Furthermore, inhalation exposure during dusty mechanical activities such as shaking and 

mechanical harvesting is another potential source of post-application inhalation exposure.

However, the airblast applicator scenario is believed to represent a reasonable worst case 

surrogate estimate of post-application inhalation exposure during these dusty mechanical 

harvesting activities. The non-cancer inhalation risk estimate for commercial airblast application 

is not of concern (i.e., MOE > 100).

10.0 References

Acibenzolar-S-Methyl. Soil Treatment Use on Citrus Crop Group 10-10 and Soil/Foliar/Paint Treatment 

Uses on Pome Crop Group 11-10. Summary of Analytical Chemistry and Residue Data. B. CroppKohlligian, D426850, 8/13/15

Acibenzolar-S-Methyl. Acute and Chronic Dietary and Drinking Water Exposure and Risk Assessment to 

Support Section 3 Use of Acibenzolar–S-Methyl Uses on Citrus Crop Group 10-10, and Pome Crop 

Group 11-10. D. McNeilly, D 426852, 08/10/2015

Acibenzolar-S-Methyl: Acibenzolar-S-Methyl. Occupational and Residential Exposure Assessment for a 

Proposed Use on Pome Crop Group 11-10 and Citrus Crop Group 10-10. I. Nieves, D426853, 8/13/2015

Acibenzolar: Subchronic Neurotoxicity Study in Rats, K. Oo, D392694, 8/3/11 

Absorption and Excretion of [U14C]Phenyl CGA 245704 in the Rat after Dermal Application, K. Oo, 

D392695, 8/3/11.

Acibenzolar, Drinking Water Exposure Assessment – C. Koper, D427617, 6/4/15

Revised Residential SOPs: http://www.epa.gov/pesticides/science/residential-exposure-sop.html
Acibenzolar-S-Methyl Human Health Risk Assessment DP No. 424596

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Appendix A. Toxicology Profile and Executive Summaries

A. TOXICOLOGY DATA SUMMARY

A.1 Guideline Data Requirements

Table A.1. Guideline Data Requirements

Guideline 

No. Study Type Technical MRID No. Required Submitted

870.1100 

870.1200 

870.1300 

870.2400 

870.2500 

870.2500 

Acute Oral Toxicity ...................................................

Acute Dermal Toxicity ..............................................

Acute Inhalation Toxicity ..........................................

Primary Eye Irritation ................................................

Primary Dermal Irritation ..........................................

870.2600 Dermal Sensitization

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

44014214

44014216

44014219

44014220

44014220

44014225

870.3100

870.3150

870.3200

870.3250

870.3465

Subchronic (Oral) Toxicity - Rodent .........................

Subchronic (Oral) Toxicity - Non-Rodent.................

21/28-Day Dermal Toxicity.......................................

90-Day Dermal Toxicity

90-Day Inhalation Toxicity .......................................

Y

Y

N

N

N*

Y

Y

Y

N

N

44014230 

44014228

44014232

42090013

46950310

---

---

870.3700a

870.3700b

870.3800

Prenatal Developmental Toxicity - Rodent................

Prenatal Developmental Toxicity - Non-Rodent .......

Reproduction and Fertility Effects.............................

Y

Y

Y

Y

Y

Y

44014236

45089701

44014237

44014241

870.4100a

870.4100b

870.4200a

870.4200b

870.4300

Chronic (Oral) Toxicity - Rodent ..............................

Chronic (Oral) Toxicity - Non-Rodent (Dog)............

Carcinogenicity - Rat...........................................

Carcinogenicity - Mouse

Combined Chronic Toxicity /Carcinogenicity

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

44014325

44014234

44014243

44014325

44014325

870.5100 

870.5300

870.5375

870.5395

870.5550

Mutagenicity—Gene Mutation - bacterial .................

Mutagenicity—Gene Mutation - mammalian............

Mutagenicity—Structural Chromosomal 

Aberrations ................................................................

Mammalian erythrocyte micronucleus test.......

Mutagenicity—UDS rat primary hepatocytes............

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

44014247

44014246

44014245

44014244

44014248

870.6100a

870.6100b

870.6200a

870.6200b

870.6300

870.7800

Neurotoxicity - Acute Delayed Neurotox.- Hen ........

Neurotoxicity - Subchronic - Hen.............................

Neurotoxicity - Acute - Rat .......................................

Neurotoxicity -Subchronic - Rat................................

Developmental Neurotoxicity..................

Immunotoxicity.................................................

N

N

Y

Y

N

Y

N

N

Y

Y

Y

Y

---

---

---

45713601

46046401

48688301
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A.2 Toxicity Profiles

Table A.2 Acute Toxicity Profile Acibenzolar-S-methyl 

Acibenzolar-S-methyl

Guideline No./

Study Type

MRID No. Results Toxicity 

Category

870.1100 Acute oral toxicity 44014214 LD50 >5000 mg/kg IV

870.1200 Acute dermal toxicity 44014216 LD50 >2000 mg/kg IV

870.1300 Acute inhalation toxicity 44014219 LC50 >5.022 mg/L IV

870.2400 Acute eye irritation 44014220 minimal III

870.2500 Acute dermal irritation 44014220 slight IV

870.2600 Skin sensitization 44014225 positive NA

Actigard 50WG

870.1100 Acute oral toxicity 44014215 LD50 >5000 mg/kg IV

870.1200 Acute dermal toxicity 44014217 LD50 >2000 mg/kg IV

870.1300 Acute inhalation toxicity 44014218 LC50 >2.79 mg/L IV

870.2400 Acute eye irritation 44014221 minimal III

870.2500 Acute dermal irritation 44014223 moderate III

870.2600 Skin sensitization 44014224 negative NA
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Table A.3 Subchronic, Chronic and Other Toxicity Profile for Acibenzolar-S-methyl 

Guideline No.

Study Type

MRID No. (year)

Classification

Dose Levels

Results

870.3100

90-day oral toxicity rodents 

(rat)

44014230 (1993)

Acceptable/Guideline

M : 0, 2.42, 24.6, 126, 516 

mg/kg/day;

F: 0, 2.64, 26.3, 131, 554 

mg/kg/day

NOAEL:126 mg/kg/day Males or M); 131 mg/kg/day (Females or 

F)

LOAEL:516 mg/kg/day (M); 554 mg/kg/day females based 

decreased body weight, reduced food intake and efficiency and 

increased liver and spleen weights

870.3150

90-day oral toxicity nonrodents (dog)

44014232 (1994)

Acceptable/Guideline

M & F: 0, 10, 50, 200 

mg/kg/day (capsules)

NOAEL:50 mg/kg/day (M & F)

LOAEL:200 mg/kg/day (F) based on regenerative hemolytic 

anemia evidenced by decreased erythroid parameters, pigmentation 

in the liver and spleen, splenic congestion, and by activation of 

medullary (bone marrow) and extramedullary (splenic) 

erythropoiesis.

870.3100

90-day oral toxicity rodents 

(mice)

44014228 (1993)

Acceptable/Guideline

0, 30.6, 152, and 624 

mg/kg/day for males, and 0, 

47.4, 220, and 803 mg/kg/day 

for females, respectively.

NOAEL: 30.6 mg/kg/day (M); 47.4 mg/kg/day (F)

LOAEL:152 mg/kg/day (M); 220 mg/kg/day females based 

decreased body weight and body weight gain, increased spleen 

weight and microscopic changes in the spleen

870.3200

21/28-day dermal toxicity (rat)

44014233 (1994)

Acceptable/guideline

M & F: 0, 10, 100, 1000 

mg/kg/day

NOAEL = 1000 mg/kg/day

LOAEL = not identified

870.3700a

Developmental Toxicity in 

rodents (rat)

44014236 (1994)

Acceptable/guideline

F: 0,10, 50, 200, 400 

mg/kg/day

Maternal NOAEL 200 mg/kg/day

Developmental NOAEL 50 mg/kg/day

Maternal LOAEL 400 mg/kg/day based on clinical signs of 

hemorrhagic perineal discharge

Developmental LOAEL 200 mg/kg/day based on developmental 

malformations, anomalies, and skeletal variations

870.3700a

Developmental Toxicity in 

rodents (rat)

45089701 (1998)

Acceptable/guideline

of 0, 10, 75, 150, or 350 

mg/kg/day

Maternal NOAEL 350 mg/kg/day

Developmental NOAEL 200 mg/kg/day

Maternal LOAEL – not established (>350)

Developmental LOAEL 350 mg/kg/day based on increased 

incidences of rudimentary and long lumbar ribs

870.3700b

Developmental Toxicity in 

non- rodents (rabbit)

44014237 (1994)

Acceptable/guideline

F: 0, 10, 50, 300, 600 

mg/kg/day

Maternal NOAEL = 50 mg/kg/day

LOAEL = 300 mg/kg/day based on mortality, clinical signs of 

toxicity, decreased maternal body weight and food consumption.

Developmental NOAEL = 300 mg/kg/day

LOAEL = 600 mg/kg/day based on a marginal increase in vertebral 

anomalies.
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Table A.3 Subchronic, Chronic and Other Toxicity Profile for Acibenzolar-S-methyl 

Guideline No.

Study Type

MRID No. (year)

Classification

Dose Levels

Results

870.6300

Developmental Neurotoxicity 

Toxicity in rodents (rat)

46046401 (2002)

Acceptable/non-guideline

0/0, 8.2/15.5, 82.0/153.6, and 

326.2/607.8 mg/kg/day 

[gestation/lactation]. 

Maternal NOAEL 326.2 mg/kg/day

Developmental NOAEL 8.2 mg/kg/day

Maternal LOAEL Not Observed

Developmental LOAEL 82 based on changes in brain 

morphometrics in the cerebellum

870.3800

Reproduction and fertility 

effects in rats

4014241 (1995)

Acceptable/guideline

M & F: 0, 1-3, 11-31, 105-

288, 223-604 mg/kg/day

Parental/Systemic NOAEL = 11-31 mg/kg/day

LOAEL = 105-288 mg/kg/day based on increased weights and 

hemosiderosis of the spleen.

Reproductive NOAEL = 223-604 mg/kg/day

LOAEL > 223-604 mg/kg/day based on no effects.

Offspring NOAEL = 11-31 mg/kg/day

LOAEL = 105-288 mg/kg/day based on reduced pup body weight 

gains and lower pup body weights during lactation.

870.6200b 

Subchronic Neurotoxicity

45713601 (1997)

acceptable/nonguideline 

pending submission of 

positive control data for 

neuropathological and FOB 

assessments

0/0, 24/26, 126/143, and 

575/628 mg/kg/day [M/F], 

respectively

The study may be upgraded 

pending submission of 

acceptable positive control 

data.

NOAEL 126/143 mg/kg/day, M/F

LOAEL 575/628 mg/kg/day, M/F based on decreased body 

weights, body weight gains, and food consumption. 

870.4100

Chronic toxicity in dogs

44014234 (1996)

Acceptable/guideline

M & F: 0, 5, 25, 200 

mg/kg/day (capsules)

NOAEL 25 mg/kg/day

LOAEL 200 mg/kg/day based on hematological effects, 

hemosiderosis of the liver and spleen, extraniedullary 

hematopoiesis in the spleen, and increases in liver weight.

870.4300

Chronic toxicity/ 

carcinogenicity in rodents 

(mice)

44014325 (1996)

Acceptable/guideline

M: 0, 1.14, 11.1, 237, 698 

mg/kg/day

F: 0, 1.14, 10.8, 234, 696 

mg/kg/day

NOAEL 11.1/10.8 mg/kg/day, M/F

LOAEL 237/234 mg/kg/day based on mild hemolytic anemia and 

related microscopic changes (hemosiderosis) in the spleen, liver, 

and bone marrow and extramedullary hematopoiesis in the spleen.

870.4200

Carcinogenicity study in rat

44014243 (1996)

Acceptable/guideline

M: 0, 0.77, 7.77, 96.9, 312 

mg/kg/day

F: 0, 0.90, 9.08, 111, 388 

mg/kg/day

NOAEL 96.9/111 (M/F)

LOAEL 312/388 / 191.0 mg/kg/d (M/F) based on decreased body 

weights, body weight gain and food efficiency, mild hemolytic 

anemia, and increased incidence of alveolar foam cells (females 

only).
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Table A.3 Subchronic, Chronic and Other Toxicity Profile for Acibenzolar-S-methyl 

Guideline No.

Study Type

MRID No. (year)

Classification

Dose Levels

Results

870.5100

Bacterial reverse mutation 

assay (Ames test)

441014247 (1993)

Acceptable/guideline

312.5, 625, 1250, 2500, 5000 

μg/plate

Negative with and without S-9 activation at 5000 μg/plate and less.

870.5100

Bacterial reverse mutation 

assay (Ames test)

Test Material: CGA- 362020 

(isomer of acibenzolar-Smethyl)

44537025 (1998)

Acceptable/guideline

61.73 to 5000 μg/plate (+S-9)

30-86 to 2500 μg/plate (-S-9)

Positive in S. typhimurium strain TA1537 at 277.8 μg/plate and 

higher in the absence of S-9. Negative with S-9 activation at 5000 

μg/plate and less.

870.5100

Bacterial reverse mutation 

assay (Ames test)

Test Material: NOA- 419191 

(by-product of acibenzolar-Smethyl)

44537024 (1998)

Acceptable/guideline

312.5 to 5000 μg/plate (± S-9)

Negative with or without S-9 activation at 5000 μg/plate and less

870.5100

Bacterial reverse mutation 

assay (Ames test)

Test Material: CGA- 323060 

(plant metabolite of 

acibenzolar-S-methyl)

44537026 (1997)

Acceptable/guideline

312.5 to 5000 μg/plate (± S-9)

Negative with or without S-9 activation at 5000 μg/plate and less

870.5300

In vitro mammalian gene 

mutation assay 

44014246 (1993)

Acceptable/guideline

3.70 to 100 μg/ml (-S-9), 

37.04 to 1000 μg/ml (+S-9)

Negative with S-9 activation up to 1000μg/ml. Negative without 

S-9 activation up to 100μg/ml.

Compound tested to cytotoxic concentrations.

870.5375

In vitro mammalian 

chromosome aberration (CHO 

cells)

44014245 (1993)

Acceptable/guideline

7.5 to 60 μg/ml (-S-9 and +S9)

Suggestive of clastogenicity in the absence of S-9 activation at 30 

and 60 μg/mL at the 18-hour cell harvest time; effect observed only 

in the presence of cytotoxicity. Increase in polyploid cells at 30 

and 60 μg/mL at the 42 hour harvest time both with and without S9. Evidence of cell cycle arresting activity at G2.

870.5395

Mammalian erythrocyte 

micronucleus test

44014244 (1993)

Acceptable/guideline

1000, 2000, 4000 mg/kg (oral 

gavage)

Negative at 16, 24, and 48, hour sacrifices.

870.5550

UDS in primary rat 

hepatocytes

44014248 (1993)

Acceptable/guideline

9.77 to 500 μg/ml

Negative at 500 μg/ml and less.

870.7485

Metabolism and 

pharmacokinetics

rats

44014250 (1995)

Acceptable/guideline

0.5, 100 mg/kg

Following oral treatment of rats, acibenzolar-S-methyl was rapidly 

and nearly completely (>90% of administered dose) absorbed from 

the gastrointestinal tract into the general circulation. The majority 

(88- 95%) of the administered dose was excreted in the urine 

within the first 48 hours. The major metabolite (79- 92%) in the 

urine was the carboxylic acid derivative of the parent.
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Table A.3 Subchronic, Chronic and Other Toxicity Profile for Acibenzolar-S-methyl 

Guideline No.

Study Type

MRID No. (year)

Classification

Dose Levels

Results

870.7600

Dermal penetration

47430503 (1995)

Acceptable/guideline

10 μg/cm2 and 100μg/cm2

An estimate of dermal absorption based on the results from the low 

dose group (10 μg/cm2), was derived. Mean dermal absorption for 

this group of animals where the skin was washed after 8 hours of 

exposure was 43.55%.

Special studies:

28-Day dietary 

rats

44014227 (1992)

Acceptable/nonguideline

M: 0, 45.9, 403, 1070 

mg/kg/day; F: 0, 44.8, 376, 

1000 mg/kg/day

NOAEL = M: 403 mg/kg/day; F: 376 mg/kg/day

LOAEL = M: 1070 mg/kg/day; F: 1000 mg/kg/day based on 

decreased mean body weights, decreased liver weights, altered 

hematology parameters accompanied by increased spleen weights.

28-Day oral gavage

rats

44014229 (1993) 

Acceptable/nonguideline

0, 10, 100, 800 mg/kg/day 

NOAEL = 100 mg/kg/day

LOAEL = 800 mg/kg/day based on decreased body weights, and 

decreased hemoglobin-related parameters accompanied by 

hemosiderosis of the spleen, increased liver and spleen weights, 

and decreased thymus weights.

28-Day oral capsule dogs 44014231 (1994) 

Acceptable/nonguideline

0, 50, 250, 500 mg/kg/day

NOAEL = 50 mg/kg/day

LOAEL = 250 mg/kg/day based on decreased body weight, 

decreased hemoglobin-related parameters, hepatic and splenic 

hemosiderosis.

90-Day Dietary 

mice

44014228 (1993)

Acceptable/nonguideline

M: 0, 30.6, 152, 624 

mg/kg/day; F: 0, 47.4, 220, 

803 mg/kg/day

NOAEL = M: 30.6 mg/kg/day; F: 47.4 mg/kg/day

LOAEL = M: 152 mg/kg/day; F: 220 mg/kg/day based on 

decreased mean body weights and body weight gain in males, 

increased spleen weights and splenic histopathology in both sexes. 

90-Day Dietary 

dog

44014232 (1994)

Acceptable/nonguideline

0, 10, 50, or 200 mg/kg/day

NOAEL = 50 mg/kg/day

LOAEL = 200 mg/kg/day in male and female dogs, based on 

regenerative hemolytic anemia evidenced by decreased erythroid 

parameters, pigmentation in the liver and spleen, splenic 

congestion, and by activation of medullary (bone marrow) and 

extramedullary (splenic) erythropoiesis.

90-Day Dietary 

rat

44014230 (1993)

Acceptable/nonguideline

males: 0,2.42, 24.6, 126, or 

516 mg/kg/day; females: 

0,2.64,26.3, 131, or 554 

mg/kg/day)

NOAEL = 126 mg/kg/day in males and 131 mg/kg/day

in females 

LOAEL = 516 mg/kg/day males and 554 mg/kg/day females based 

on decreased mean body weights, reduced food intake, reduced 

food efficiency, and increased liver and spleen weights with 

correlates for the liver and spleen of glycogen deposition and 

hemosiderosis, respectively. 

Special

Developmental toxicity 

rats

44014238 (1994)

Acceptable/nonguideline

300 mg/kg/day, GD 6-15, 6-7, 

8-9, 10-11, 12-13, or 14-15

Maternal and developmental NOAELS and LOAELS could not be 

identified by this protocol. The most pronounced maternal and 

developmental toxicity occurred when dams were treated on GD 6-

15.
Acibenzolar-S-Methyl Human Health Risk Assessment DP No. 424596

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Table A.3 Subchronic, Chronic and Other Toxicity Profile for Acibenzolar-S-methyl 

Guideline No.

Study Type

MRID No. (year)

Classification

Dose Levels

Results

Special

Developmental toxicity

rats

44014239 (1994)

Acceptable/nonguideline

400 mg/kg/day, GD 6-7, 8-9, 

10-11, 12-13, or 14-15

Maternal and developmental NOAELS and LOAELS could not be 

identified by this protocol. The most pronounced maternal and 

developmental toxicity occurred when dams were treated on GD 6-

7 and 8-9.

Dermal developmental toxicity

rats

44014240 (1994)

Acceptable/nonguideline

0, 10, 100, 500 mg/kg/day, 

GD 6-15

Maternal NOAEL ≥500 mg/kg/day

LOAEL >500 mg/kg/day based on no effects.

Developmental NOAEL ≥500 mg/kg/day

LOAEL >500 mg/kg/day based on no effects.

Range-finding 

1-generation reproduction 

rats

44681301 (1993)

Acceptable/nonguideline

0, 199-209, 382-410, 700-728 

mg/kg/day

Parental/Systemic NOAEL = 209 mg/kg/day

LOAEL = 410 mg/kg/day based on decreased body weight gain 

and food consumption in females.

Reproductive NOAEL = 410 mg/kg/day

LOAEL = 728 mg/kg/day based on total resorptions in all dams.

Offspring NOAEL = 209 mg/kg/day

LOAEL = 410 mg/kg/day based on reduced pup body weight gains 

and lower pup body weights during lactation.
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A.3 Toxicological Endpoints

A.3.1 Acute Reference Dose (aRfD) – Females 13-49 years old and Children 1-12 years old

Selected Study: Developmental Neurotoxicity in Rats (MRID 46046401). 

See Section 3.2.3

Dose and Endpoint for Establishing an aRfD: 8.2 mg/kg/day based on an offspring 

NOAEL of 8.2 mg/kg/day and an offspring LOAEL of 82 mg/kg/day based on changes in brain 

morphometrics in the cerebellum. 

Uncertainty Factor (UF): 100 – 10x for interspecies extrapolation and 10x for intraspecies 

variation.

Comments about Study/Endpoint: The developmental neurological effects of concern are 

presumed to occur after a single exposure and are relevant to females aged 13-50 years old since 

they occur in utero and to young children based on post-natal effects. 

[Note: Based on a reevaluation of the DNT study regarding the potential for post-natal 

toxicity, the acute dietary analysis should include females 13-49 and children 1-12 for this 

assessment.]

 

A.3.2 Chronic Reference Dose (cRfD) - Females age 13-49 and Young Children

Selected Study: Developmental Neurotoxicity in Rats (MRID 46046401). 

See Section 3.2.3

Dose and Endpoint for Establishing a cRfD: 8.2 mg/kg/day based on an offspring 

NOAEL of 8.2 mg/kg/day and an offspring LOAEL of 82 mg/kg/day based on changes in brain 

morphometrics in the cerebellum. 

Uncertainty Factor (UF): 100 – 10x for interspecies extrapolation and 10x for intraspecies 

variation.

Comments about Study/Endpoint: The effects observed in this study can occur after 

single or multiple doses. Selection of a chronic endpoint from this study ensures that the chronic 

exposure assessment is protective of females of reproductive age and their offspring. 

 Acute RfD = 8.2 mg/kg (NOAEL) = 0.0.082 mg/kg/day

 (General Population) 100 (UF)
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[Note: In the previous risk assessment (D361893, 3/3/09) only the subpopulation females 

13-50 years old was assessed for chronic dietary exposure based on in utero effects observed in 

the DNT study. However, based on a reevaluation of the DNT study regarding the potential for 

post-natal toxicity, the chronic dietary analysis the chronic dietary exposure analysis has been 

revised to include an assessment of dietary risks to children using the NOAEL from the DNT 

study.]

A.3.3 Chronic Reference Dose (RfD) – Adult Males and Females 50+ years

Selected Studies: Co-critical studies Chronic Feeding Study in Dogs (MRID 44014234); 

Oncogenicity Study Mouse (MRID 44014235); Chronic/Oncogenicity Study Rat (MRID 

44014243); Reproductive Study Rat (44014241)

Chronic Dog Study - In a chronic oral toxicity study acibenzolar-S-methyl was 

administered to 4 beagle dogs per sex per dose level in gelatin capsules at levels of 0, 5, 25, or 

200 mg/kg/day for 52 weeks. No biologically significant toxic effects were observed in either 

males or females receiving 25 mg/kg/day or less of the test material. At 200 mg/kg/day, there 

was an indication of hemolytic anemia in dogs of both sexes i.e., effects consistent with prior or 

current hemolytic anemia including hematological effects, hemosiderosis of the liver and spleen, 

extraniedullary hematopoiesis in the spleen, and increases in liver weight. Significant treatmentrelated changes were found in clinical chemistry in the dogs fed the test, substance at 200 

mg/kg/day, (increase in triglycerides in both sexes, increase of cholesterol in females at week 13, 

decrease in total protein in males at weeks 26 and 52, and decrease in albumin in both sexes at 

week 13. These clinical chemistry changes are suggestive of possible nutritional deficiencies. 

The LOAEL is 200 mg/kg/day in both sexes based on effects consistent with prior or current 

hemolytic anemia. The NOAEL is 25 mg/kg/day. 

Oncogenicity Mouse Study - In an oncogenicity study acibenzolar-S-methyl was 

administered in the diet to groups of 60 male and 60 female Tif:MAGf (SPF) mice at 

concentrations of 0, 10, 100, 2000, or 6000 ppm (1.14, 11.11, 237, and 698 mg/kg/day for males 

and 1.14, 10.8, 234, and 696 mg/kg/day for females) for 18 months. Ten mice per group were 

reserved for measurements of hematology parameters after 12 and 18 months of treatment. 

Treatment did not result in a significant decrease in survival. The overall food efficiency was 

decreased in females by 22% at 6000 ppm. The red blood cell count, hemoglobin, and 

hematocrit at 53 and 79 weeks were decreased in females at 2000 ppm and 6000 ppm. Mean 

corpuscular volume was decreased in high dose males at 79 weeks. Mean corpuscular 

hemoglobin concentration distribution increased at 6000 ppm. Reticulocyte counts in high-dose 

females was significantly increased. The hematology data are consistent with hemolytic anemia 

 Chronic RfD = (NOAEL) 8.2 mg/kg = 0.082

 (Females 13-49/Young Children) (UF) 100
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especially in females at 2000 and 6000 ppm. Macroscopic and microscopic findings consistent 

with a mild hemolytic anemia in both sexes included increased incidences of enlarged spleen, 

increased incidences of hemosiderosis in liver, spleen, and bone marrow. Incidence of 

extramedullary hematopoiesis in the spleen and pancreatic exocrine hyperplasia was increased in 

males at 2000 and 6000 ppm. Incidences of alveolar foam cells in the lungs were increased at 

6000 ppm in both sexes. The LOAEL is 2000 ppm (237/234 mg/kg/day males/females), based 

on mild hemolytic anemia and related microscopic changes (hemosiderosis) in the spleen, liver, 

and bone marrow and extramedullary hematopoiesis in the spleen. The NOAEL was 100 ppm 

(11.1 mg/kg/day males; 10.8 mg/kg/day females).

Chronic/Oncogenicity Rat Study - In a chronic toxicity/oncogenicity study, acibenzolarS-methyl was administered in the diet to groups of 80 male and 80 female (Tif:RAIf (SPF)) 

Sprague-Dawley derived rats at concentrations of 0, 20, 200, 2500, or 7500 ppm (0, 0.77, 7.77, 

96.9, and 312 mg/kg/day male and 0, 0.90, 9.08, 111, and 388 mg/kg/day female). Ten animals 

per sex per dose were sacrificed at 52 weeks for interim evaluation; the remaining animals were 

used for hematologic and clinical chemistry evaluation (20 per sex per group) and evaluation of 

carcinogenic potential (50 animals per sex per group). No treatment-related effects were 

observed at 20, 200 or 2500 ppm for any parameter. Treatment related effects on body weight, 

weight gain, food consumption, and food efficiency were observed in both sexes at 7500 ppm. 

Other treatment-related effects at 7500 ppm included a slight hemolytic anemia in both sexes as 

evidenced by decreases in erythrocyte count, increased mean corpuscular volume, elevated 

reticulocyte counts, increased serum bilirubin, increased severity of hemosiderin deposition in 

the spleen, and increased incidence of hemosiderin deposition in Kupifer cells of the liver. 

Hemosiderin deposition in the spleen was accompanied by a statistically significant increase in 

spleen weight. There was also a statistically significant increase in the incidence of foam cells in 

the lungs of females fed the 7500-ppm diet. The LOAEL was 7500 ppm (312/388 mg/kg/day 

males/females) based on decreased body weights, body weight gain and food efficiency, mild 

hemolytic anemia, and increased incidence of alveolar foam cells (females only). The NOAEL 

was 2500 ppm (96.9 mg/kg/day males and 111 mg/kg/day females). 

Reproductive Study in Rats - See Section 3.2.2

Dose and Endpoint for Establishing cRfD: 25 mg/kg/day based on a NOAEL of 25 

mg/kg/day from the chronic dog study and a LOAEL of 105 mg/kg/day from the rat reproduction 

study based on hemolytic anemia with compensatory response. 

Uncertainty Factor(s): 100 – 10x for interspecies extrapolation and 10x for intraspecies 

variation.

Comments about Study/Endpoint/Uncertainty Factor: The NOAEL of 25 mg/kg/day, 

taken from the chronic dog study, is based on the totality of the database with a LOAEL of 105 

mg/kg/day (the lowest LOAEL is from the reproduction study) based on hemolytic anemia with 

compensatory response. The NOAEL and LOAEL recommended for use in the risk assessment 
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come from different studies conducted in different species. Typically, a combination of 

NOAELs/LOAELs from studies conducted in different species is not recommended. However, 

in the case of acibenzolar-S-methyl the same endpoint (hemolytic anemia) is observed across 

species at a relatively close range of LOAELs (105-312 mg/kg/day). Therefore, the ToxSAC

concluded that, in this instance, it would be appropriate to base the point of departure for the risk 

assessment on the NOAEL from the dog chronic toxicity study using the LOAEL from the 

reproduction study in rats for the basis of the endpoint (hemolytic anemia).

A.3.4 Incidental Oral Exposure (Short- and Intermediate-Term)

Selected Study: Developmental Neurotoxicity in Rats (MRID 44014236). 

See Section 3.2.3

Dose and Endpoint: 8.2 mg/kg/day based on an offspring NOAEL of 8.2 mg/kg/day and 

an offspring LOAEL of 82 mg/kg/day based on changes in brain morphometrics in the 

cerebellum. 

Uncertainty Factor (UF): 100 – 10x for interspecies extrapolation and 10x for intraspecies 

variation.

Comments about Study/Endpoint: This endpoint is considered appropriate based on the 

post-natal component of the DNT. 

A.3.5 Dermal Absorption

A dermal absorption factor (DAF) is applied when dermal exposure endpoints are 

selected from oral toxicity studies. The dermal factor converts the oral dose to an equivalent 

dermal dose for the risk assessment. A DAF of 44% was selected for use in risk assessment 

based on a dermal absorption study in rats. 

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

Selected Study: Developmental Neurotoxicity in Rats (MRID 44014236). 

See Section 3.2.3

Dose and Endpoint: 8.2 mg/kg/day based on an offspring NOAEL of 8.2 mg/kg/day and 

an offspring LOAEL of 82 mg/kg/day based on changes in brain morphometrics in the 

cerebellum. 

 Chronic RfD = 25 mg/kg/day (NOAEL) = 0.25 mg/kg/day

 (Adult Male) 100 (UF)
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Uncertainty Factor (UF): 100 – 10x for interspecies extrapolation and 10x for intraspecies 

variation.

Comments about Study/Endpoint: Two acceptable dermal toxicity studies, including a 

dermal developmental study were available. However since neurological effects observed in the 

oral developmental neurotoxicity study are not measured in the dermal developmental study, the 

findings from the dermal study may not be protective of these neurological effects. Since an oral 

NOAEL was selected for dermal risk assessment, a dermal absorption factor of 44% should be 

used. This factor is based on a dermal absorption study in rats.

A.3.7 Inhalation Exposure (Short and Intermediate-Term)

Selected Study: Developmental Neurotoxicity in Rats (MRID 44014236). 

See Section 3.2.3

Dose and Endpoint: 8.2 mg/kg/day based on an offspring NOAEL of 8.2 mg/kg/day and 

an offspring LOAEL of 82 mg/kg/day based on changes in brain morphometrics in the 

cerebellum. 

Uncertainty Factor (UF): 100 – 10x for interspecies extrapolation and 10x for intraspecies 

variation.

Comments about Study/Endpoint: Since an oral NOAEL was selected for inhalation risk 

assessment, an inhalation absorption factor of 100% should be used
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A.4 Executive Summaries

870.3700 Developmental Toxicity

In a non-guideline developmental toxicity study (MRID 44014238), twelve presumed pregnant 

Tif:RAT f(SPF) (hybrids of RTT/1 x RII/2) rats per group were administered CGA 245704 

Technical (97.9%; Batch No. P.303011) in a 0.5% aqueous solution of sodium 

carboxymethylcellulose by gavage at a dose of 300 mg/kg/day. Groups 2-7 were administered 

test article on gestation days (GD) 6-15,6- 7, 8-9, 10-11, 12-13, or 14-15, respectively. Group 1 

consisted of twelve animals which served as controls and were treated with 0.5% sodium 

carboxymethylcellulose on GD 6-15. On GD 21, dams were sacrificed, subjected to gross 

necropsy, and all fetuses examined externally. Visceral and skeletal examinations were not 

performed. All animals survived until scheduled sacrifice on GD 21. Bloody, vaginal discharge 

was observed in 8/12 dams in Group 2, 3/12 dams in Group 3, 5/12 dams in Group 4, 4/12 dams 

in Group 5, and in 5/12 dams in Group 6. This finding was observed for one to four days starting 

on GD 13 and was not observed in controls or in animals in Group 7. No other treatment-related 

clinical signs of toxicity were observed. No statistically significant differences in absolute body 

weights or body weight changes occurred at any time between the treated groups and the control 

group. Body weight gain by Group 2 was 80% of the control level during the treatment interval 

(GD 6- 16), with the greatest reduction in weight gain (77% of controls) during GD 11-16. Food 

consumption was not affected. There were no statistically significant differences between control 

and treatment groups for number of corpora lutea, number of implantation sites, live fetuses/dam, 

pre- and post-implantation loss, or fetal sex ratios. Fetal body weights from the Group 2 dams 

were significantly (p <0.01) less than the controls. Although not statistically significant, Group 2 

dams also had fewer live fetuses per litter (10.9 vs 14.8 for controls) and a greater post

implantation loss (30.1% vs 2.9% for controls) from early resorptions due to one dam with whole 

liner resorption (17/17) and 2 additional dams with 13/16 and 8/9 resorptions/number of 

implantation sites. The overall incidence rates for litters containing fetuses with major external 

malformations in Groups 1-7 were 0/12, 1/10, 0/10, 1/11, 0/11, 0/10, and 0/12, respectively. In 

one Group 2 litter, generalized edema was observed in 5/14 fetuses. In addition, two of the five 

also had a position anomaly of the hindlimb and one of the two also had gastroschisis. These five 

fetuses also had greatly reduced body weights. Generalized edema was also seen in one fetus 

from Group 4. Maternal and developmental toxicity NOAELs and LOAELs could not be 

identified by this protocol, which investigated the critical period of organogenesis. The most 

pronounced maternal and developmental toxicity occurred when dams were treated on GD 6-15, 

inclusive at a dose level of 300 mg/kg/day. This study is classified as Acceptable/non-guideline 

as a developmental toxicity study (83-3a) in rats.

In a non-guideline developmental toxicity study (MRID 44014239), eight presumed pregnant 

Tif: RAT f (SPF) (hybrids of RII/1 x RII2) rats per group were administered CGA 245704 

Technical (97.9%; Batch No. P.303011) by gavage at a dose of 400 mg/kg/day. Groups 2-6 were 

administered test article on gestation days (GD) 6-7, 8-9, 10-11, 12-13, or 14-15, respectively. 

Group 1 consisted of eight animals which served as controls and were treated with 0.5% 
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carboxymethylceliulose (vehicle) on GD 6-15. On GD 21, dams were sacrificed, subjected to 

gross necropsy, and all fetuses examined externally. Visceral and skeletal examinations were not 

performed. One Group 2 dam was found dead on GD 20. Prior to death, this animal had bloody 

perineal discharge and necropsy findings including mottled kidney and thymus. One Group 4 

dam delivered on GD 20 and was sacrificed. All other animals survived until scheduled sacrifice 

on GD 21. Bloody, perineal discharge was observed in 4/8 dams in Group 3. This finding was 

observed for three to four days starting on GD 16. The same 4 dams were later observed to have 

total lifter resorptions. No other treatment-related clinical signs of toxicity were observed. No 

statistically significant differences in body weights, body weight gains, or food consumption 

occurred at any time between the treated groups and the control group. There were no 

differences between the control group and Groups 4, 5, and 6 for number of corpora lutea, 

number of implantation sites, live fetuses/dam, pre- and post-implantation loss, fetal body 

weights, or fetal sex ratios. Group 2 had a slightly greater number of early resorptions/dam (2.7 

vs 0.9 for controls) and an increased postimplantation loss (18.7% vs 5.4% for controls). The 

four Group 3 dams observed with bloody discharge had complete litter resorption resulting in 

increased postimplantation loss (53.4%). Group 3 also had an increase in early rcsorptions 

(8.0/dam vs 0.9/dam for controls) and decreased mean live fetuses/litter (8.5 vs 16.0 for 

controls). Another Group 3 dam had fused placenta between two fetuses. The overall incidence 

rates for liners containing fetuses with major external malformations in Groups 1-6 were 0/8, 0/6, 

0/4, 1/7, 0/8, and 0/8, respectively. One Group 4 fetus had cleft palate and another fetus from the 

same lifter had a kinked tail. No treatment-related external malformations /variations were 

observed in any fetus from any group. Maternal and developmental toxicity NOAELs and 

LOAELs could not be identified by this protocol, which investigated the critical period of 

organogenesis. Pronounced maternal and developmental toxicity occurred when dams were 

treated on GD 6-7 and 8-9 at a dose level of 400 mg/kg/day.

870.7600 Dermal Toxicity Studies

In a dermal developmental toxicity study (MRID 44014240), 24 pregnant Tif: RAIf (SPF) rats 

(Sprague-Dawley derived) per group were administered acibenzolar-S-methyl (97.9% a.i.) in 

aqueous carboxymethylcellulose (0.5% w/w) in 0.1% aqueous Polysorbate 80, by dermal 

application at doses of 0 (vehicle), 10, 100, or 500 mg/kg/day on gestation days (GD) 6-15, 

inclusive. Exposure duration was 6 hours per day. On GD 21, all dams were sacrificed and all 

fetuses were sexed, weighed, and examined for external malformations/variations, then 

sacrificed. Approximately one-half of each litter was placed in Bouin’s fixative for subsequent 

visceral examination and the remainder were prepared and stained for skeletal examination. All 

animals survived until scheduled sacrifice. No clinical signs of toxicity were observed at any 

treatment level. Gestational body weights, body weight changes, and food consumption were not 

statistically significantly different for any treatment level throughout the gestational period.

Therefore, the maternal toxicity NOAEL is 500 mg/kg/day based on no adverse maternal effects 

at the highest administered dose. The maternal toxicity LOAEL was >500 mg/kg/day. No 

treatment-related effects were observed for gravid uterine weights, number of fetuses/litter, preand post-implantation losses, numbers of corpora lutea/dam, number of implantations/dam, 
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resorptions/dam, fetal body weights, or fetal sex ratios. No biologically relevant statistically 

significant differences in the incidence rates of any external, visceral, or skeletal malformations/

anomalies/variations were observed in the treated litters as compared to the controls. There were 

statistically significantly decreased incidences of absent ossification of the proximal phalanx of 

anterior digit-2 in all treatment groups and poor ossification of the proximal phalanx of posterior 

digit-2 in the 500 mg/kg/day treatment group as compared to the control group. However, these 

decreases were not considered to be biologically significant. Therefore, the developmental 

toxicity NOAEL is 500 mgfkglday based on no adverse developmental effects at the highest dose 

administered. The developmental toxicity LOAEL was >500 mg/kg/day.

In a 28- day repeated dose dermal toxicity study (MRID 44014233), groups of 5 females Tif: 

RAIf (SPF) albino rats were treated with acibenzolar-S-methyl technical in 0.5% (w/v) 

carboxymethyl cellulose/0.1% (w/v) aqueous polysobate 80 at doses of 0, 1, 10, 100 or 1000 

mg/kg/day. Animals were treated by dermal occlusion for 6 hours/day, 5 days/week for 4 weeks. 

No animals died during the study. There were no treatment- related clinical signs, dermal 

effects, effects on body weight, food consumption, hematology, clinical chemistry, or organ 

weight. No gross or microscopic pathology were noted at necropsy. The systemic and dermal 

NOAEL is the limit dose of 1000 mg/kg/day. A dermal and systemic LOAEL were not 

identified. 

870.3800 Reproduction

In a 1-generation range-finding reproduction study in rats (Nonguideline study, MRID 

44014241) CGA 245704 Technical (97.9% a.i.; Batch No. P.303011) was administered to groups 

of 15 male and 15 female Tif: RAT f (SPF), hybrids of RTTI 1 x P11/2 (Sprague-Dawley 

derived) rats at dietary concentrations of 0, 2000, 4000, or 8000 ppm for one generation (MRID 

44681301). In this range- finding study, F0 adults were administered test or control diet for two 

weeks prior to mating. Premating doses were 199.4, 382.0, and 700.1 mg/kg/day, respectively, 

for F0 males and 208.7, 409.9, and 727.8 mg/kg/day, respectively, for F0 females. Males were 

terminated at the end of mating and females were terminated at weaning of their pups. All 

offspring, except five litters per dose group, were necropsied at weaning. After weaning, five 

litters per dose group were retained on treatment for an additional three weeks and then 

necropsied. The only clinical sign of toxicity in the parental animals was perineal hemorrhage 

during late gestation in five high-dose females. Gross necropsy was unremarkable. Absolute 

body weights, body weight gains, and food consumption values for the low- and mid-dose males 

and low-dose females were similar to the controls throughout the study. High-dose males had 

significantly (p > 0.01; 88-91% of control) lower body weights than the controls beginning on 

day 8 and continuing until study termination. Overall weight gain by the high-dose males was 

69% of the control level. Body weights and body weight gains of the high-dose females were 

significantly (p > 0.01; body weights 88-90% of controls) Tess than the controls during the 

premating interval. Overall body weight gain by the high- dose group was only 30% of the 

control group level. Mid-dose females had significantly (p > 0.05) lower body weight gains than 

the controls during days 1-8. Reduced body weight gains in the high- dose males and females 
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and mid-dose females correlated with significantly (p > 0.05 or 0.01) reduced food consumption 

by these treated groups during study days 1-8. Lower body weights, body weight gains, and food 

consumption continued for the mid- and high-dose females during gestation and lactation. Body 

weights of the high-dose group were significantly (p > 0.05 or 0.01) lower than the controls 

throughout gestation with overall weight gain by the high-dose females during gestation 27% (p 

> 0.01) of the control group level. Mid-dose females had significantly (p > 0.05 or 0.01) lower 

body weights than the controls on GD 21 and on lactation days 7, 14, and 21. Weight gains by 

the mid-dose group during gestation and lactation were 92% and 83%, respectively of the control 

group levels. Food consumption by the high-dose group was significantly (p > 0.05 or 0.01) less 

than the controls throughout gestation. Food consumption by the mid-dose group was 

significantly (p > 0.01) less than the controls throughout lactation. Therefore, the LOAEL for 

parental toxicity is 4000 ppm based on reduced food consumption and lower body weight gains 

in F0 females. The parental toxicity NOAEL is 2000 ppm. Mating and fertility indices, mean 

precoital interval, mean gestation length, and mean numbers of corpora lutea and implantation 

sites per dam were similar between the treated and control groups. Mating and fertility indices 

for the high-dose group were similar to the control group, but no live lifters were produced by 

the high-dose group (i.e. all pregnancies were lost). Live births and pup survival were similar 

between the low- and mid-dose groups and the control group. Therefore, the LOAEL for 

reproductive toxicity is 8000 ppm based on total resorptions in all dams. The reproductive 

toxicity NOAEL is 4000 ppm. No treatment-related clinical signs of toxicity were observed in 

the pups during lactation. Absolute body weights of pups in the low-dose group were similar to 

the controls throughout lactation. Body weights of the mid-dose pups were significantly (p >

0.05 or 0.01; 76-89% of controls) less than the controls beginning on lactation day 7 and 

continuing throughout lactation and postweaning. The lower body weights of the mid-dose pups 

were a result of significantly (p > 0.05 or 0.01; 69-89% of controls) lower body weight gains 

from postnatal day 4 through postnatal day 28. Recovery of body weight gains occurred during 

the postweaning intervals of days 28-35 and 35-42. Therefore, the LOAEL for developmental 

toxicity is 4000 ppm based on reduced pup body weight gains and lower pup body weights 

during lactation and early postweaning. The developmental toxicity NOAEL is 2000 ppm.

870.6200b Subchronic Neurotoxicity

In a subchronic neurotoxicity study (MRID 45713601), CGA-245704 (Acibenzolar, 97.9% a.i., 

Batch No. P.303011) was administered in the diet to 10 Sprague-Dawley derived rats/sex/group

at dose levels of 0, 400, 2000, or 8000 ppm (equivalent to 0/0, 24/26, 126/143, and 575/628 

mg/kg/day [M/F], respectively) for at least 90 days. Neurobehavioral assessment (functional 

observational battery [FOB] and motor activity testing) was performed using all rats at predosing and Weeks 4, 8, and 13. At study termination, 5 rats/sex/group were anesthetized and 

perfused in situ for neuropathological examination. The tissues from the perfused animals in the 

control and 8000 ppm groups were subjected to histopathological evaluation of brain and 

peripheral nervous system tissues. Positive control data were not provided.No compound-related 

effects were observed in mortality, clinical signs of toxicity, FOB, motor activity, or gross or 

neuropathology. At 8000 ppm, body weights were generally decreased throughout the study in 
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the males (decreased 11-14%, not statistically significant) and females (decreased 8-13%, 

attaining statistical significance at Weeks 2-5, 7 and 8, and 11-13). Also at this dose, cumulative 

body weight gains were decreased throughout the study in the males (decreased 19-35%, 

attaining statistical significance at Weeks 2-4 and 6-9), and in the females (decreased 24-40%). 

A decreasing trend (p<0.01) in body weight and body weight gain was also generally noted in 

both sexes at this dose. These decreases in body weight gain corresponded with decreases in 

food consumption which was sporadically decreased in the 8000 ppm males (decreased 9-21% at 

Weeks 1-3, 5-7, and 11, but only attaining statistical significance during Week 1), and females 

(decreased 14-18%, p<0.01 at Weeks 1 and 3). A decreasing trend (p<0.01) in food 

consumption was also generally noted in the males at 8000 ppm during the weeks reported 

above. No neurological effects were observed at any dose in either sex.

The LOAEL was 8000 ppm (equivalent to 575/628 mg/kg/day, M/F) based on decreased body 

weights, body weight gains, and food consumption. The NOAEL is 2000 ppm (equivalent to 

126/143 mg/kg/day, M/F).

The subchronic neurotoxicity study in rats (MRID 45713601) on Acibenzolar had been reviewed 

and is classified as acceptable/non-guideline. 

870.5100, 870-5300, 870.5375, 870.5900 Mutagenicity 

Five acceptable mutagenicity studies on technical grade acibenzolar-S-methyl are available:

1. Reverse gene mutation, S. typhimuriumlE. Coli (MRID 44014247)

2. Forward gene mutation, Chinese hamster V79 lung cells in culture/HGPRT locus (MRID

44014246)

3. Chromosome aberration, Chinese hamster ovary (CHO) cells in culture (MRID 44014245)

4. Unscheduled DNA synthesis assay, primary rat hepatocytes in culture (MRID 44014248)

5. In vivo cytogenetics, micronucleus assay in mice (MRID 44014244)

Results in all five studies were negative for genotoxicity. The five studies on the technical 

grade product satisf’ the new revised mutagenicity guideline requirements for a new 

chemical (published in 1991). 

Three additional acceptable mutagenicity studies on a) an isomer (CGA-362020) of acibenzolar 

S-methyl, b) a by-product (NOA 419191) of acibenzolar-S-methyl, and c) a plain metabolite 

(CGA-323060) of acibenzolar-S-methyl are also available.

1. Reverse gene mutation, S. typhimuriumlE. Coli; Test Material: CGA-362020 (MRID

44537025). This study was POSITIVE for evidence of induced mutant colonies over 

background in S. typhimurium strain TA1537 at concentrations of 277.8 and higher in the 

absence of 59-mix.

2. Reverse gene mutation, S. typhimuriumlE. Coli; Test Material: NOA 419191 (MRID

44537024). This study was negative.
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3. Reverse gene mutation, S. typhimuriumfE. Coli; Test Material: CGA-323060 (MRlD

44537026). This study was negative
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Appendix B. Chemical Names and Structures of Metabolites

N

N

S

O SCH3

Acibenzolar N

N

S

COOH

CGA 210007

N

N

S

COOH

HO

CGA 324041

N

N

S

COOH

OH

CGA 323060

S

COOH

O

CH3

CGA 379019

CGA 379789

S

COOH

O

CH3

O

CGA 379018

S

COOH

CH3

TRR, % ppm 

Lettuce 0.6 0.006

Tomato

 Fruit 7.3 0.023

 Leaves 1.5 0.011

Wheat

 Forage 2.4 0.007

 Straw 1.3 0.004

 Grain 4.8 <0.001

Rice

 Straw 0.5 0.009

TRR, % ppm 

Lettuce 20.1 0.204

Tomato

 Fruit 4.8 0.015

 Leaves 6.1 0.044

Wheat

 Forage 2.4 0.007

 Straw 1.3 0.004

 Grain 4.8 <0.001

TRR, % ppm 

Lettuce 25.1 0.255

Tomato

 Fruit 65.2 0.203

 Leaves 19.2 0.138

Wheat

 Forage 57.9 0.168

 Straw 43.5 0.149

 Grain 39.3 0.001

Rice

 Grain 5.6 0.005

 Hulls 16.8 0.027

 Straw 56.2 1.120

TRR, % ppm 

Lettuce 16.9 0.171

Tomato

 Fruit 0.8 0.002

 Leaves ND ND

Wheat ND ND

Rice ND ND

TRR, % ppm 

Rice

 Grain 18.8 0.016

 Hulls 7.9 0.013

 Straw 8.8 0.175

also found in paddy water

TRR, % ppm 

Rice

 Grain 3.6 0.003

 Straw 0.1 0.002

also found in paddy water

TRR, % ppm 

Rice

 Straw 0.7 0.014

also found in paddy water
Acibenzolar-S-Methyl Human Health Risk Assessment DP No. 424596

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Acibenzolar-S-Methyl Human Health Risk Assessment DP No. 424596

Page 57 of 58

Appendix C. Physical/Chemical Properties

Physicochemical Properties of Acibenzolar-S-Methyl.

Parameter Value Reference

Melting point/range 133 oC DP# 250963, 2/10/99, H. 

Podall pH 7.9 (1% solution in water) at 25 

oC

Density 1.54 g/cc at 22 oC (bulk 

density)

Water solubility 0.0077 g/L

Solvent solubility Methanol 4.2 g/L

Acetone 28 g/L

Toluene 36 g/L

n-Octanol 5.4 g/L

n-Hexane 1.3 g/L

Ethyl acetate 25 g/L

Dichloromethane 160 g/L 

European Commission, 

6506/VI/99-final, 5/21/02

Vapor pressure 3.6 x 10-6 Torr at 25 oC DP# 250963, 2/10/99, H. 

Podall

Dissociation constant, pKa No dissociation constant in an

accessible pH range (1.0 - 9.0)

European Commission, 

6506/VI/99-final, 5/21/02

Octanol/water partition 

coefficient, Log(KOW)

Log (POW) 3.1 at 25 oC DP# 250963, 2/10/99, H. 

Podall

UV/visible absorption spectrum 253 nm ε : 14.7 103 l mol-1 cm-1

288 nm ε : 5.4 103

324 nm ε : 7.2 103

European Commission, 

6506/VI/99-final, 5/21/02
Acibenzolar-S-Methyl Human Health Risk Assessment DP No. 424596

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Appendix D. Studies Reviewed for Ethical Conduct

The PHED Task Force, 1995. The Pesticide Handlers Exposure Database, Version 1.1. Task 

Force members Health Canada, U.S. Environmental Protection Agency, and the National 

Agricultural Chemicals Association, released February, 1995.

Agricultural Re-entry Task Force (ARTF) data base (SOP #3.1)