UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

MEMORANDUM

February 23, 2011

SUBJECT: Acibenzolar-S-methyl

Acibenzolar-S-methyl 

PC Code: 061402

Decision No.: 443561

Petition No.: 7E7818

Risk Assessment Type: Single Chemical Aggregate

TXR No.: NA

MRID No.: NA

FROM: Becky Daiss, Biologist 

James Scott Miller

Thurston Morton, 

Abdallah Khasawinah, Toxicologist

Risk Assessment Branch 

Health Effects Division (7509

THROUGH: Elissa Reaves, PhD, 

Susan V. Hummel, Branch Senior Scientist

Risk Assessment

TO: Sydney Jackson, Risk Manager Review

Risk Integration, Minor Use & Emergency Response Branch

Registration Division 

This document provides the 

acibenzolar-S-methyl on low growing berries, crop subgroup 13

Page 1 of 47

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

methyl Human Health Risk Assessment for Propos

methyl on Low Growing Berries Crop Subgroup 13

DP Barcode: 387071

Registration No.: 100-RGAG

Regulatory Action: Section 3 Registration

Single Chemical Aggregate Case No.: 7031

CAS No.: 135158-54-2

40 CFR: 180.561

, Biologist 

Miller, Environmental Scientist

, Chemist

Abdallah Khasawinah, Toxicologist

Risk Assessment Branch 4

Health Effects Division (7509P)

PhD, Chief

Susan V. Hummel, Branch Senior Scientist

Branch 4, HED (7509P)

, Risk Manager Review

Risk Integration, Minor Use & Emergency Response Branch

Registration Division (7505P)

the Health Effects Division’s (HED’s) risk assessment of 

low growing berries, crop subgroup 13-07G. 

Human Health Risk Assessment for Proposed Use of 

Low Growing Berries Crop Subgroup 13-07G.

RGAG

Section 3 Registration

Health Effects Division’s (HED’s) risk assessment of use of 
Page 2 of 47

TABLE OF CONTENTS

pg.

1.0 EXECUTIVE SUMMARY .................................................................................................4

2.0 HED RECOMMENDATIONS............................................................................................6

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

2.2 Tolerance Considerations.....................................................................................................6

2.2.1 Enforcement Analytical Method..............................................................................6

2.2.2 International Harmonization ....................................................................................6

2.2.3 Recommended Tolerances.......................................................................................6

2.2.4 Revisions to Petitioned-For Tolerances...................................................................7

3.0 INGREDIENT PROFILE....................................................................................................7

3.1 Chemical Identity ................................................................................................................7

3.2 Physical/Chemical Properties ..............................................................................................8

3.3 Pesticide Use Pattern............................................................................................................8

3.3.1 Registered Products .................................................................................................8

3.3.2 Registered and Proposed New Uses ........................................................................8

3.4 Anticipated Exposure Pathways ..........................................................................................9

3.5 Consideration of Environmental Justice ..............................................................................9

4.0 HAZARD CHARACTERIZATION/ASSESSMENT.........................................................9

4.1 Toxicology Studies Available for Analysis.........................................................................9

4.2 Absorption, Distribution, Metabolism, & Elimination ........................................................9

4.3 Toxicological Effects.........................................................................................................10

4.4 Safety Factor for Infants and Children...............................................................................11

4.4.1 Completeness of the Toxicology Database............................................................12

4.4.2 Evidence of Neurotoxicity .....................................................................................12

4.4.3 Evidence of Sensitivity/susceptibility in the Developing or Young......................12

4.4.4 Residual Uncertainty in the Exposure Data Base ..................................................13

4.5 Toxicity Endpoint and Point of Departure Selections.......................................................13

4.5.1 Dose-Response Assessment...................................................................................13

4.5.2 Recommendation for Combining Exposure Routes ..............................................14

4.5.3 Cancer Classification ............................................................................................14

4.5.4 Summary of Points of Departure Used in Risk Assessment..................................15

5.0 DIETARY AND DRINKING WATER RISK ASSESSMENT........................................16

5.1 Metabolite/Degradate Residue Profile...............................................................................16

5.1.1 Summary of Plant and Animal Metabolism Studies..............................................16

5.1.2 Comparison of Metabolic Pathways......................................................................16

5.1.3 Environmental Fate and Transport.........................................................................16

5.1.4 Residues of Concern Summary and Rationale.......................................................17

5.2 Food Residue Profile..........................................................................................................18

5.2.1 Residues in Crops, Livestock and Poultry .............................................................18

5.3 Water Residue Profile ........................................................................................................18
Page 3 of 47

5.3.1 Estimated Drinking Water Concentrations............................................................18

5.4 Dietary and Drinking Water Exposure and Risk ...............................................................19

5.4.1 Acute Dietary Exposure and Risk..........................................................................19

5.4.2 Chronic Dietary Exposure and Risk ......................................................................20

6.0 RESIDENTIAL EXPOSURE AND RISK........................................................................20

6.1 Residential Bystander Postapplication Inhalation Exposure .............................................20

6.2 Spray Drift .........................................................................................................................21

7.0 AGGREGATE EXPOSURE AND RISK ASSESSMENT...............................................21

7.1 Short-Term Aggregate Risk to Residential Applicators....................................................22

8.0 CUMULATIVE RISK.......................................................................................................22

9.0 OCCUPATIONAL EXPOSURE AND RISK...................................................................23

9.1 Exposure Scenarios............................................................................................................23

9.2 Handler Exposure...............................................................................................................23

9.2.1 Handler Exposure Scenarios..................................................................................23

9.2.2 Handler Exposure Data ..........................................................................................23

9.2.3 Handler Exposure Assumptions.............................................................................23

9.2.4 Handler Exposure and Risk Estimates...................................................................24

9.3 Post Application Exposure.................................................................................................25

9.3.1 Post Application Exposure Scenarios....................................................................25

9.3.2 Post Application Exposure Assumptions...............................................................25

9.3.3 Post Application Exposure and Risk Estimates.....................................................26

9.3.4 Restricted Entry Interval........................................................................................26

10.0 REFERENCES ..................................................................................................................26

Appendix A. Toxicity Profile and Executive Summaries..............................................................28

A.1 Toxicity Data Requirements..................................................................................28

A.2 Toxicity Profiles.....................................................................................................29

A.3 Hazard Identification and Endpoint Selection .......................................................29

A.4 Executive Summaries.............................................................................................39

Appendix B. Metabolism ..............................................................................................................45

Appendix C. Physical/Chemical Properties...................................................................................47

Appendix D. Review of Human Research.....................................................................................47
Page 4 of 47

1.0 EXECUTIVE SUMMARY

This assessment provides information to support an amended Section 3 registration for 

the use of acibenzolar-S-methyl on low growing berries, crop subgroup 13-07G. This document 

addresses the exposures and 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.

 

Use Profile

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 vegetables 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.

Acibenzolar-S-methyl acts to protect plants against invading pathogens by inducing a natural 

defense reaction that enhances the plants ability to ward off disease. Agricultural applications 

may be made using ground or aerial equipment. Acibenzolar-S-methyl is also registered for 

residential application to turf grass using handheld spray equipment. 

 

Proposed New Uses

The Interregional Research Project No. 4 (IR-4), on behalf of the Agricultural 

Experiment Stations of CO, NM, UT, ID, and WA, is requesting to amend the product label for 

Actigard® (EPA Reg. No. 100-922), a water-dispersible granule (WG) formulation containing 

50% acibenzolar-S-methyl to add a new use on the low growing berry crop subgroup 13-07G. 

Actigard® is proposed for multiple foliar applications on the low growing berry subgroup using 

ground or aerial equipment at a maximum of 0.023 lb ai/A per application, a maximum seasonal 

rate of 0.188 lb ai/A, and a 0-day pre-harvest interval (PHI). 

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. 
Page 5 of 47

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, or 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 showed no significant toxicity in a battery of acute toxicity tests 

(Toxicity Category III or IV in all tests) but showed considerable skin-sensitivity. 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 is being reviewed. Based on a preliminary

review, the study is acceptable and indicates no evidence of immunotoxicity. 

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 RfD for the general population was 

not selected because no effect attributable to a single day oral exposure was observed in animal 

studies. Acute and chronic RfD’s for females 13-49 were selected from a developmental 

neurotoxicity toxicity study in rats based on changes in brain morphometrics in the cerebellum. 

A chronic RfD 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 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 new uses of acibenzolar-S-methyl on low growing berries. A 

new residential assessment is not required because the proposed new use does not include 

residential applications or exposures. Refined acute and screening level chronic dietary and 

drinking water risk assessments for acibenzolar-S-methyl showed 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 
Page 6 of 47

and post-application 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

2.1 Data Deficiencies/Conditions of Registration 

Submission of a reference standard for the metabolite CGA 210007, and a revised 

Section F are required. An immunotoxicity study required as part of new 40 CFR Part 158 data 

requirements for registration of a pesticide has been submitted and is being reviewed. Based on 

a preliminary review, the study is acceptable and indicates no evidence of immunotoxicity.

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 CGA210007 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-Smethyl in/on any commodity. Therefore, international harmonization is not an issue. 

2.2.3 Recommended Tolerances

HED has examined the residue chemistry database for acibenzolar-S-methyl. Pending 

submission of a revised Section F (see requirements under Proposed Tolerances), there are no 

residue chemistry issues that would preclude granting a Section 3 registration for the requested 

use of acibenzolar-S-methyl on crop subgroup 13-07G, or the establishment of a tolerance for 

residues of acibenzolar-S-methyl, as follows:
Page 7 of 47

Table 1. Tolerance Summary for Acibenzolar-S-methyl.

Commodity Established 

Tolerance (ppm)

Proposed 

Tolerance (ppm)

Recommended 

Tolerance (ppm)

Comments; Correct 

Commodity Definition

Tolerances to be listed under 40 CFR §180.561(a):

Berry, low growing

subgroup 13-07G

-- 0.15 0.15

Note to Registration Division: Tolerances have been established under 40 CFR §180.561 for 

residues of acibenzolar-S-methyl. HED continues to recommend that the appropriate tolerance 

expression for acibenzolar-S-methyl read as follows. 

Tolerances are established for residues of acibenzolar-S-methyl, benzo(1,2,3)thiadiazole7-carbothioic acid-S-methyl ester, including its metabolites and degradates, in or on the 

commodities in the table below. Compliance with the tolerance levels specified below 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 the commodity.

2.2.4 Revisions to Petitioned-For Tolerances

There are no revisions to the petitioned for tolerance.

3.0 INGREDIENT PROFILE 

3.1 Chemical Identity

Table 2. Acibenzolar-S-Methyl Nomenclature.

Chemical structure

Common name acibenzolar-S-methyl

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-bensothiadiazole-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

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

N

N

S

O S

CH3

N

N

S

COOH
Page 8 of 47

3.2 Physical/Chemical Characteristics 

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

provided in Appendix B. Acibenzolar-S-methyl exhibits relatively low solubility in water and 

higher solubility in solvents. It has a very low vapor pressure. It does not present significant 

concerns for bioaccumulation based on its lipophilicity and mammalian metabolism studies. 

3.3 Pesticide Use Pattern

3.3.1 Registered Products

There are currently 7 active acibenzolar-S-methyl registrations including four Section 3

registrations and five special local needs (SLNs) or 24(c) registrations. 

Table 3. Summary Report of Supported Registered Acibenzolar-S-methyl Products

Reg # Name Company Name %AI

100-921 Acibenzolar-S-Methyl Technical

Syngenta Crop Protection, Inc.

99

100-922 Actigard 50WG 50

100-1363 Bion 500 SF 54

100-1364 Daconil Action 0.11

FL030003

Actigard 50 WG Plant Activator

50

GA020005 50

NC020007 50

SC030004 50

VA030002 50

3.3.2 Proposed New Uses 

The Interregional Research Project No. 4 (IR-4), on behalf of the Agricultural 

Experiment Stations of CO, NM, UT, ID, and WA, is requesting to amend the product label for 

Actigard® (EPA Reg. No. 100-922), a water-dispersible granule (WG) formulation containing 

50% acibenzolar-S-methyl to add a new use on the low growing berry crop subgroup 13-07G. 

Actigard® is proposed for multiple foliar applications on the low growing berry subgroup using 

ground or aerial equipment at a maximum of 0.023 lb ai/A per application, a maximum seasonal 

rate of 0.188 lb ai/A, and a 0-day pre-harvest interval (PHI). 

Table 4. Proposed New Use of Acibenzolar-S-Methyl on Low Growing Berries

Applic. 

Timing, Type, 

and Equip.

Formulation

[EPA Reg #]

Applic. 

Rate 

(lb ai/A)

Max. No. 

Applic. 

per Season

Max. 

Seasonal 

App Rate

(lb ai/A)

PHI

(days) Use Directions and Limitations

Postemergence

Foliar or 

banded

Ground /Aerial

50% WG

[100-922]

0.016-

0.023 8 (Implied) 0.188 0

Actigard® should be applied to healthy, 

actively growing plants. Do not apply prior 

to thinning or within 5 days of transplanting. 

Do not apply Actigard® to plants that are 

stressed due to drought, excessive moisture, 

cold weather, or herbicide injury, etc. Avoid 

spray overlap as injury may occur.
Page 9 of 47

3.4 Anticipated Exposure Pathways

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

acibenzolar-s-methyl on low growing berries. 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 proposed new uses on low growing berries. 

3.5 Considerations 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. 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 postapplication 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/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. An immunotoxicity study required as part of new 40 CFR Part 158 data 

requirements for registration of a pesticide has been submitted and is being reviewed. Based on 

a preliminary review, the study is acceptable and indicates no evidence of immunotoxicity.

4.2 Absorption, Distribution, Metabolism and Excretion

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 
Page 10 of 47

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 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 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. 

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

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 
Page 11 of 47

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 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 enduse 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 NOAELs and LOAELs have been identified for all effects of concern, a clear dose 
Page 12 of 47

response has been well defined, and 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.

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 and subchronic neurotoxicity. The 

immunotoxicity study required under 40 CFR Part 158 data requirements has been submitted and 

is being reviewed. Based on a preliminary review, the study is acceptable and indicates no 

evidence of 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 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 subchronic neurotoxicity study in rats no compound-related effects were observed in 

the FOB, motor activity, gross 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. Based on the results of developmental toxicity and 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 preand/or postnatal toxicity since NOAELs and LOAELs have been identified for all effects of 

concern, a clear dose response has been well defined, and the points of departure (PODs)

selected for risk assessment are protective of the fetal/offspring effects. There are no residual 

uncertainties with regard to pre- and/or postnatal toxicity. 
Page 13 of 47

4.4.4 Residual Uncertainty in the Exposure Database 

There are no residual uncertainties in the exposure database. The dietary risk assessment 

is conservative and will not underestimate dietary and/or non-dietary residential exposure to 

acibenzolar-S-methyl.

4.5 Toxicity Endpoint and Point of Departure

4.5.1 Dose-Response Assessment

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 are presented in Appendix A. 

An acute POD of 8.2 mg/kg/day (NOAEL) was selected for all populations from an 

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 0.1 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 13-50 years old since they occur in utero and to young children 

based on post-natal effects. 

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

old was assessed for acute dietary exposure based on in utero effects. However, based on a 

reevaluation of the DNT study regarding the potential for post-natal toxicity, the acute dietary

analysis has been expanded to all populations in order to include children for this and more 

recent previous assessments (D379425, 8/19/10).]

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 0.1 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 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) of 25 mg/kg/day was selected for adult males 

and females (50+ years) based on hemolytic effects seen in chronic dog study and other co-
Page 14 of 47

critical toxicity studies. 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 0.25 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) 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 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 45% was used for the dermal exposure assessment

based on a dermal absorption study in rats An MOE 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 Recommendations for Combining Exposure Routes

When there are potential residential exposures to the pesticide, aggregate risk assessment 

must consider exposures from three major sources: oral, dermal and inhalation exposures. There 

is potential residential post-application exposure to adults via the dermal route and to children 

via dermal and incidental oral routes of exposure. Dietary, dermal and incidental oral endpoints 

for acibenzolar-S-methyl are based on common toxicological effects for females 13-49 years old 

and children. Therefore, exposures from food and non-food oral and dermal routes should be 

aggregated for those subpopulations for this assessment. In addition, dermal, and inhalation 

exposures should be aggregated for acibenzolar-S-methyl, because the same oral toxicity

endpoint was selected for both exposure routes. 

4.5.3 Classification of Carcinogenic Potential

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. 
Page 15 of 47

4.5.4 Summary of Points of Departure Used in Risk Assessment

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

provided in Tables 5 and 6.

Table 5. Summary of Toxicological Doses and Endpoints for Acibenzolar-S-methyl for Use in Dietary Human 

Health Risk Assessments

Exposure/

Scenario

Point of 

Departure

Uncertainty/F

QPA Safety 

Factors

RfD, PAD, 

LOC for Risk 

Assessment

Study and Toxicological Effects

Acute Dietary 

(General 

Population)

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 & Young 

Children)

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 

(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 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.
Page 16 of 47

Table 6. 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 = 40%

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 AND DRINKING WATER EXPOSURE AND RISK ASSESSMENT

5.1 Metabolite/Degradate Residue Profile

5.1.1 Summary of Plant Metabolism Studies

No new plant metabolism studies were submitted. 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 CGA-210007 at the C-4 and C-5 positions 

results in the formation of the minor metabolites CGA-324041 (all crops tested) and CGA323060 (lettuce and tomato), which may also form acyl sugar conjugates. 

5.1.2 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 

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

5.1.3 Environmental Fate and Transport

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

potential to leach to ground water nor move to surface water based on its short resident times in 
Page 17 of 47

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 250C pH 3.6-3.8 v. 7.7 ppm at 250C 

pH 7.5-7.9). CGA 210007 has longer resident field times than parent (aerobic soil half-life at 

16.5 days) and based on the batch equilibrium and aged soil column leaching studies, is 

considerably more mobile. Acibenzolar is not considered a bioconcentrate nor is it highly

bioaccumulative. 

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 expression are residues convertible to 

benzo(1,2,3)thiadiazole-7-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 acibenzolar-S-methyl. These residues occur in significant quantities in lettuce and 

tomato. At this time, 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. Table 7 provides a summary

of the MARC decisions regarding residues of concern for acibenzolar-S-methyl.

Table 7. Summary of MARC Decisions for Acibenzolar-S-methyl

Matrix Residues of Concern 1

For Risk Assessment 2 For Tolerance Expression

Plants 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

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
Page 18 of 47

5.2 Food Residue Profile

5.2.1 Residues in Crops

The registrant submitted crop field trial data from field trial conducted on strawberry as 

the representative crop of the low growing berry subgroup 13-07G. Crop field trials conducted 

on strawberry as the representative are in accordance with the guideline for strawberry as the 

representative crop of the low growing berry subgroup 13-07G. The number and locations of 

field trials are in accordance with OPPTS guideline requirements. The trials reflect the proposed 

maximum seasonal rate and pre-harvest interval (PHI), and there are adequate storage stability

data to validate sample storage conditions and duration. The majority of the tank mixes 

contained an adjuvant. The maximum residues of acibenzolar-S-methyl (i.e., residues 

convertible to CGA-210007) were 0.087 ppm in/on strawberry. The residue data were entered 

into the OECD MRL Calculator. The available strawberry field trial data are deemed adequate 

to support a tolerance of 0.15 ppm for residues of acibenzolar-S-methyl in/on the low growing 

berry subgroup 13-07G.

Adequate confined rotational crop data have been submitted previously. Based on the 

available field rotational crop data for wheat, turnip, and lettuce, tolerances are not needed for 

rotational crops provided a 30-day plant-back interval is established for all crops not listed as 

target crops. The existing rotational crop restrictions on the Actigard® label are adequate.

5.3 Water Residue Profile

5.3.1 Estimated Drinking Water Concentrations 

Drinking water residues provided by the Environmental Fate and Effects Division 

(EFED) (D353745, R. Miller, 9/2/10) were incorporated directly into the acute and chronic 

dietary analyses. The surface water estimates were based on EFED’s Tier II model Pesticide 

Root Zone Model. The residues of concern for drinking water include acibenzolar-S-methyl and 

residues convertible to CGA-210007. The estimated drinking water concentrations (EDWCs) for 

use of acibenzolar-S-methyl on cucumbers were used for the drinking water assessment because 

this use represents the highest use rate of the existing and proposed registered uses. The SCIGROW estimated ground water drinking water concentrations for acibenzolar is not expected to 

exceed 1.25 x 10-5μg/L and CGA 210007 is not expected to exceed 8.12 x 10-2μg/L. Surface 

water EDWCs for acibenzolar-S-methyl, which were used in the exposure assessment, are 

provided in Table 8. CGA-210007 drinking water residues were included in the dietary exposure 

assessment as acibenzolar-S-methyl equivalents. 

Table 8. EDWCs for use in screening the human health risk assessment (FL Cucumber)

Drinking Water 

Source Chemical 1-in-10 year 

annual acute 

conc. (μg/L)

1-in-10 year avg 

annual (chronic) 

concentration (μg/L)

30-year avg. annual 

concentration(μg/L)

Surface Water Acibenzolar-S-Methyl1

0.72 0.02 0.02

Surface Water CGA 2100072

20.02 8.09 4.68

1 Aerial application method

2 Degradation product formed after application 
Page 19 of 47

5.4 Dietary and Drinking Water Exposure and Risk

Refined acute and screening-level chronic dietary and drinking water exposure and risk 

assessments were conducted using the Dietary Exposure Evaluation Model with the Food 

Commodity Intake Database (DEEM-FCIDTM). Dietary risk assessment incorporates both 

exposure and toxicity of a given pesticide. For acute and chronic dietary assessments, the risk is 

expressed as a percentage of a maximum acceptable dose (i.e., the dose which HED has 

concluded will result in no unreasonable adverse health effects). This dose is referred to as the 

population adjusted dose (PAD). The PAD is equivalent to the reference dose (RfD) divided by 

the additional Safety Factor, if applied. For acute and non-cancer chronic exposures, HED is 

concerned when estimated dietary risk exceeds 100% of the PAD. 

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

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

acibenzolar-S-methyl convertible to the benzo(1,2,3) thiadiazole-7-carboxylic acid (CGA210007). 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-323060 and CGA-324041). 

5.4.1 Acute Dietary and Drinking Water Analysis

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

population and all population subgroups. The acute analysis assumed a distribution of residues 

based on field trial data. Empirical and DEEM default processing factors were used to modify

the field trial data. 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 entire time distribution of 

EDWCs adjusted to account for CGA-210007. Acute dietary risk estimates are not of concern 

for general population or other population subgroups. The subgroup with the highest risk 

estimate was children 3-5 years old with a 99.9th percentile acute exposure estimates of 35% of 

the aPAD. The 99.9th percentile aPAD for the general U.S. population was 17%. 

Table 9: Summary of Acute Dietary Exposure and Risk for Acibenzolar-S-Methyl

Population Subgroup aPAD (mg/kg/day) Acute (99th Percentile)

Exposure (mg/kg/day) % aPAD

General U.S. Population

0.082

0.014091 17

All Infants (< 1 year old) 0.012951 16

Children 1-2 years old 0.025042 31

Children 3-5 years old 0.028536 35

Children 6-12 years old 0.019902 24

Youth 13-19 years old 0.015095 18

Adults 20-49 years old 0.009060 11

Adults 50+ years old 0.010614 13

Females 13-49 years old 0.009540 12
Page 20 of 47

5.4.2 Chronic Dietary and Drinking Water Analysis

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. DEEM default and empirical processing factors were used to modify the 

tolerance values. The chronic analysis incorporated the 10 year average surface drinking water 

estimate from application of acibenzolar-S-methyl to cucurbit vegetables. 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 subgroups with the highest risk estimate were 

children 1-2 and 3-5 years old with a cPAD of 11%. The cPAD for the general U.S. population 

was 2%. 

Table 10: Summary of Chronic Dietary Exposure and Risk to Female and Child Population for 

Acibenzolar-S-Methyl 

Population Subgroup cPAD (mg/kg/day)

Chronic

Exposure (mg/kg/day) % cPAD

Females 13-49 years old

0.082

0.003646 4

All Infants (< 1 year old) 0.003808 5

Children 1-2 years old 0.009207 11

Children 3-5 years old 0.008706 11

Children 6-12 years old 0.008706 7

Table 12: Summary of Chronic Dietary Exposure and Risk to Adults 50+ and Adult Males (13+)

Acibenzolar-S-Methyl

Population Subgroup cPAD (mg/kg/day) Chronic

Exposure (mg/kg/day) % cPAD

General U.S. Population

0.25

0.004366 5

Males 13-19 0.003893 2

Males 20+ 0.003654 2

Adults 50+ years old 0.003852 2

6.0 RESIDENTIAL EXPOSURE AND RISK ASSESSMENT

A new residential exposure assessment is not required for the proposed new use of 

acibenzolar-S-methyl on low growing berries because there are no homeowner uses and/or 

applications to residential areas associated with this use.

 

6.1 Residential Bystander Postapplication Inhalation Exposure

Based on the Agency's current practices, a quantitative residential bystander 

postapplication inhalation exposure assessment was not performed for acibenzolar-S-methyl at 

this time. However, volatilization of pesticides may be a potential source of postapplication 

inhalation exposure to individuals nearby to pesticide applications. The Agency sought expert 

advice and input on issues related to volatilization of pesticides from its Federal Insecticide, 

Fungicide, and Rodenticide Act Scientific Advisory Panel (SAP) in December 2009. The 

Agency received the SAP’s final report on March 2, 2010 
Page 21 of 47

(http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html). The Agency is in the 

process of evaluating the SAP report and may, as appropriate, develop policies and procedures, 

to identify the need for and, subsequently, the way to incorporate postapplication inhalation 

exposure into the Agency's risk assessments. If new policies or procedures are put into place, the 

Agency may revisit the need for a quantitative postapplication inhalation exposure assessment 

for acibenzolar-S-methyl.

6.2 Spray Drift

Spray drift is always a potential source of exposure to residents nearby to spraying 

operations. This is particularly the case with aerial application, but, to a lesser extent, could also 

be a potential source of exposure from the ground application method employed for acibenzolarS-methyl. The Agency has been working with the Spray Drift Task Force, 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 at 

http://www.epa.gov/opp00001/factsheets/spraydrift.htm). On a chemical by chemical basis, the 

Agency is now requiring interim mitigation measures for aerial applications that must be placed 

on product labels/labeling. The Agency has completed its evaluation of the new database 

submitted by the Spray Drift Task Force, a membership of U.S. pesticide registrants, and is 

developing a policy on how to appropriately apply the data and the AgDRIFT computer model to 

its risk assessments for pesticides applied by air, orchard airblast and ground hydraulic methods. 

After the policy is in place, the Agency may impose further refinements in spray drift 

management practices to reduce off-target drift with specific products with significant risks 

associated with drift.

Although a quantitative residential post-application inhalation exposure assessment was 

not performed as a result of pesticide drift from neighboring treated agricultural fields, an 

inhalation exposure assessment was performed for flaggers. This exposure scenario is 

representative of a worse case inhalation (drift) exposure and may be considered protective of 

most outdoor agricultural and commercial post-application inhalation exposure scenarios. 

7.0 AGGREGATE EXPOSURE AND RISK ASSESSMENT 

In accordance with the FQPA, when there are potential residential exposures to a 

pesticide, aggregate risk assessment must consider exposures from three major routes: oral, 

dermal, and inhalation. There are three sources for these types of exposures: food, drinking 

water, and residential uses. 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. Acute and chronic aggregate risks are 

not of concern.
Page 22 of 47

7.1 Short- Term Aggregate Risk

To assess short--term aggregate risk likely to result from the new and existing uses, HED 

combined average food and water exposure values with estimates of residential exposure for 

adult handlers and with residential exposure for adult and child post-application activities Tables 

11 and 12. Exposure for adult and child golfers was used to aggregate adult post-application 

dermal exposure with dietary and drinking water exposure. The aggregate exposure assessment 

for children combines dermal and incidental oral post-application exposure with food and water 

exposure. 

Table 11. Short-Term Aggregate Risk Calculations - Residential Handler LOC =100

Population Subgroup

Average

Food & Water Exposure

mg/kg/day

Residential

Exposure1

mg/kg/day

Aggregate MOE

(food and

residential)2

Females 13-49 yrs 0.0038 0.0073 700

1 Residential Exposure = [Dermal exposure + Inhalation Exposure]. 

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

Table 12. Short-Term Aggregate Risk Calculations - Residential Post-Application Exposure LOC =100

Population Subgroup

Average

Food & Water Exposure

mg/kg/day

Residential 

Exposure1

mg/kg/day

Aggregate MOE

(food and

residential)2

Females 13-49 yrs 0.0038 0.00135 1600

Children 6-12 yrs 0.0059 0.00194 1000

Children 1-2 yrs 0.0093 0.0009 800

Children 3-5 yrs 0.0088 850

1 Residential Exposure = [Dermal exposure + Inhalation Exposure]. 

2 Aggregate MOE = [NOAEL (8.2 mg/kg/day (Avg Food & Water Exposure + Residential Exposure)] Adult residential postapplication exposure from golfer scenario. Child residential exposure includes incidental oral and dermal exposures.

8.0 CUMULATIVE RISK

Section 408(b)(2)(D)(v) of FFDCA requires that, when considering whether to establish, 

modify, or revoke a tolerance, the Agency consider “available information” concerning the 

cumulative effects of a particular pesticide's residues and “other substances that have a common 

mechanism of toxicity.”

EPA does not have, at this time, available data to determine whether acibenzolar-Smethyl has a common mechanism of toxicity with other substances. 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 which have tolerances in the U. S. For the purposes of this 

tolerance reassessment 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 OPP 

concerning common mechanism determinations and procedures for cumulating effects from 
Page 23 of 47

substances found to have a common mechanism on EPA’s website at 

http://www.epa.gov/fedrgstr/EPA_PEST/2002/January/Day_16/.

9.0 OCCUPATIONAL EXPOSURE/RISK CHARACTERIZATION

9.1 Exposure Scenarios

Occupational handler and post-application exposure scenarios were assessed for the risk 

assessment of the proposed new uses on low growing berries. Based on the product labels and 

information provided by the registrant, short- and intermediate-term exposure is assessed for 

occupational handlers and post-application activities. Dermal and inhalation exposures to 

workers are aggregated for acibenzolar-S-methyl because the toxicity endpoints for these 

exposure routes are based on common toxicological effects.

9.2 Handler Exposure 

The term “handler” applies to individuals who mix, load, and apply the pesticide product. 

The following handler exposure scenarios were assessed for proposed new acibenzolar-S-methyl

uses.

9.2.1 Handler Exposure Scenarios

- Open mixing/loading (dry flowable) for aerial application;

- Open mixing/loading (dry flowable) for groundboom application;

- Applying sprays via aerial applications;

- Applying sprays via groundboom applications

- Flagging for aerial applications

9.2.2 Handler Exposure Data

No chemical-specific handler exposure data were submitted in support of this 

registration. It is the policy of the HED to use surrogate data from the US Environmental 

Protection Agency, Office of Pesticide Programs , Occupational Pesticide Handler Unit 

Exposure Surrogate Reference Table, June 21, 2011, which summarizes and extracts surrogate 

data from the Pesticide Handlers Exposure Database Version 1.1 (PHED 1.1), the Agricultural 

Handler Exposure Task Force (AHETF) database, and the Outdoor Residential Exposure Task 

Force (ORETF) database. Some of these data, such as the industry task force data, are 

compensatory, subject to the data protection provisions of FIFRA. HED policies on use of 

surrogate data, including their sources, are presented on the internet at 

http://www.epa.gov/pesticides/science/handler-exposure-data.html . The “Occupational Pesticide 

Handler Unit Exposure Surrogate Reference Table” may be found at 

http://www.epa.gov/pesticides/science/handler-exposure-table.pdf.

9.2.3 Handler Exposure Assumptions

The following standard exposure assumptions were used in estimating risks to workers 

from exposure to acibenzolar-S-methyl for the proposed new use on low growing berries. The 
Page 24 of 47

daily areas treated were defined for each handler scenario by determining the amount that can be 

reasonable treated in a single day. When possible, the assumptions for daily areas treated are 

taken from HED’s ExpoSAC Policy #9 (: “Standard Values for Daily Acres Treated in 

Agriculture”, which was revised on July 5, 2000.

• Average body weight of an adult handler is 60 kg.

• Exposure duration is short-term and intermediate-term for all workers assessed. 

• Maximum application rates as determined by label review were used for all types and 

methods of application. The maximum single application rate for low growing berries

is 0.023 lbs ai per acre.

• Estimated dermal absorption is 44%

• SOP daily volumes handled and/or area treated used for the scenarios assessed are: 

- 80 acres treated per day for groundboom mixer/loader and applicator

- 350 acres treated per day for applications with fixed wing aircraft and flagging 

9.2.4 Handler Exposure and Risk Estimates

A target LOC or MOE of 100 is considered adequate for inhalation and dermal exposure. 

All worker exposures are assessed as short-and intermediate-term based on label prescribed uses 

and expected exposure durations. Dermal and inhalation exposures to workers should be 

aggregated for acibenzolar-S-methyl because the same oral toxicity endpoint was selected for 

these exposure routes. Exposure and risk estimates indicate MOEs are not of concern (MOEs > 

100) at the maximum use rate for occupational handler activities for the proposed new uses. A 

summary of occupational handler exposure and risk calculations, assumptions, and results is 

provided in Table 13. 

Table 13: Short/Intermediate-Term Occupational Handler Exposure and Risk for Acibenzolar-S-Methyl for Application to Low 

Growing Berries

Exposure 

Scenario 

1

App 

Rate 

lbai/A2

Acres 

Treatd

/day

Unit Exposure3(ug/lb ai) Dose (mg/kg/Day)4,5 MOEs6

Dermal 

Inhal 

Dermal

Inhal

Dermal

Inhal

Combined

Derm & Inhal

Baseline Gloves BL G BL G BL G

Mixer/Loader (dry flowable)

Aerial 

0.023

350

227 52 8.96

0.013

3

0.003

0

0.001

2

620 2700 6800 570 1800

Ground

boom 80 0.0030

0.000

6

0.000

3

2500 11000 27000 2500 8000

Applicator (dry flowable)

Aerial

0.023

350 0.005

Eng. C N/A 0.068 0.0003

NA 9E-06 28000 NA 900000 25000 NA

Ground

boom 80 78.6 16.1 0.0003 0.0011

0.000

2

1E-05 7800 35000 790000 7700 37000

Flagger (dry flowable)

Aerial 0.023 350 11 12 0.35 0.000

6

0.000

7

5E-05 13000 12000 170000 12000 11000

1 Use patterns are from the proposed labels 

2 Application rates are based on maximum values based on proposed label. 

3 Unit exposures for baseline (no personal protective equipment (PPE) and PPE (e.g., gloves). Values are reported in the PHED 

Surrogate Exposure Guide dated August 1998 or are from data submitted by the Outdoor Residential Exposure Task Force dated 

May 2000. 
Page 25 of 47

4

Inhalation dose (mg/kg/day) = [unit exposure (ug/lb ai) * 0.001 mg/ug unit conversion * Inhalation absorption (100%) *

Application rate (lb ai/acre or lb ai/gallon) * Daily area treated/amount handled (acres or gallons)] / Body weight (60 kg).

5 Dermal Dose (mg/kg/day) = [unit exposure (mg/lb ai) * Application rate (lb ai/acre or lb ai/gallon) * Daily area treated/amount 

handled (acres or gallons) * Dermal Absorption Factor (44%)] / Body weight (60 kg).

6

 Aggregate MOE = NOAEL (8.2 mkd)/Daily Inhalation Dose + Daily Dermal Dose

9.3 Post Application Exposure 

HED uses the term “post-application” to describe those individuals who can be exposed 

to pesticides after entering areas previously treated with pesticides and performing certain tasks 

or activities. For acibenzolar-S-methyl, post-application dermal exposure to field workers 

following foliar applications is probable since acibenzolar-S-methyl is a fungicide that can be 

applied to all stages of growth. Since no post-application data were submitted in support of the 

registration action, dermal exposures during post-application activities were estimated using 

dermal transfer coefficients from the Science Advisory Council for Exposure Policy Number 3 

(http://www.epa.gov/pesticides/science/exposac_policy3.pdf). 

Based on the Agency's current practices, a quantitative occupational post-application 

inhalation exposure assessment was not performed for acibenzolar-S-methyl at this time. 

However, there are multiple potential sources of post-application inhalation exposure to 

individuals performing post-application activities in previously treated fields. These potential 

sources include volatilization of pesticides and re-suspension of dusts and/or particulates that 

contain pesticides. The Agency sought expert advice and input on issues related to volatilization 

of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory

Panel (SAP) in December 2009. The Agency received the SAP’s final report on March 2, 2010 

(http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html). The Agency is in the 

process of evaluating the SAP report as well as available postapplication inhalation exposure 

data generated by the Agricultural Reentry Task Force and may, as appropriate, develop policies 

and procedures, to identify the need for and, subsequently, the way to incorporate occupational 

post-application inhalation exposure into the Agency's risk assessments. If new policies or 

procedures are put into place, the Agency may revisit the need for a quantitative occupational 

post-application inhalation exposure assessment for acibenzolar-s-methyl.

9.3.1 Post Application Exposure Scenarios

• Handweeding

• Scouting 

• Transplanting

• Hand harvesting, scouting, and raking

• Irrigating

9.3.2 Post Application Exposure Assumptions

• Average body weight is 60 kg.

• Transferrable residue is application rate times the fraction initially available (20%). 

• Maximum transfer coefficient for post-application activities is 1900 cm2/hour 

(irrigation).

• Exposure duration is 8 hours day.
Page 26 of 47

• Exposure is assumed to occur on the day of application (day 0).

9.3.3 Post-Application Exposure and Risk Estimates

A target LOC or MOE of 100 is considered adequate for dermal exposure. Exposure and 

risk estimates indicate MOEs are not of concern (MOEs > 100) at the maximum use rate for 

occupational post-application exposure activities for the proposed new uses. A summary of postapplication exposure and risk calculations, assumptions, and results is provided in Table 14.

Table 14. Summary of Estimated Post-application MOEs for Agricultural Crops

Crop

Application 

Rate

(lb ai/A) 1

DAT2 DFR 3

(μg/cm2)

TC 4

(cm2/hr) Activity 4 Short-/IntTerm MOE5

Low Growing 

Berries 0.023 0 0.052

70 Hand weeding 39,000

210 Scouting 13,000

230 Transplanting 12,000

1,100 Hand harvesting, 

Scouting, Raking 2,500

1,900 Irrigation 1,400

1 Maximum application rate from proposed label 

 2 DAT = Days after treatment needed to reach the LOC of 100; DAT 0 = the day of treatment/ assumed to be approx. 12 hours. 

 3 DFR (μg/cm2

) = dislodgeable foliar residues corresponding to DAT, based on 20% of application rate.

 4 TC (cm2

/hr) = transfer coefficients and associated activities from ExpoSAC Policy Memo #003.1, 8/17/2000.

 5 MOE = MOE on the corresponding DAT. MOE = NOAEL / Daily Dose. 

 Daily Dose = [(DFR x TC x 40% Dermal absorption x 8-hr Exposure Time)] / [(CF: 1000 μg/mg) x (60-kg Body Weight) 

 Short-/intermediate-term NOAEL = 8.2 mg/kg/day. The LOC is 100

9.3.4 Restricted Entry Interval

Acibenzolar-S-methyl has been classified in Toxicity Category III for acute dermal and 

eye irritation and Category IV for primary skin irritation. Per the Worker Protection Standard 

(WPS), a 12-hr restricted entry interval (REI) is required for chemicals classified under Toxicity

Category III/IV. 

10. REFERENCES

Acibenzolar-S-Methyl. Petition for the Establishment of Permanent Tolerances on Low 

Growing Berries (Subgroup 13-07G). Summary of Analytical Chemistry and Residue Data, T. 

Morton, D386364, 2/23/12

Acibenzolar-S-Methyl –Acute and Chronic Dietary and Drinking Water Exposure and Risk 

Assessment to support a Section 3 Request for Use of Acibenzolar-S-Methyl on Low Growing 

Berries Crop Subgroup 13-07G, T. Morton, D387069, 2/23/12

Occupational Exposure Assessment to Support the Request for Registration of Acibenzolar-SMethyl on Low Growing Berries (subgroup 13-07 G), J.S. Miller, D387841, 2/23/12

Acibenzolar: Subchronic Neurotoxicity Study in Rats, K. Oo, D392694, 8/3/11 
Page 27 of 47

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 – R. Miller, D353745, 9/2/10
Page 28 of 47

APPENDICES

A. TOXICOLOGY DATA SUMMARY

A.1 Guideline Data Requirements

Guideline 

No. Study Type Technical MRID 

Required Submitted No.

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

870.6100a

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

* Studies have been submitted and are under review 
Page 29 of 47

A.2 Toxicity Profiles

Table 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

Table 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
Page 30 of 47

Table 3 Subchronic, Chronic and Other Toxicity Profile for Acibenzolar-S-methyl 

Guideline No.

Study Type

MRID No. (year)

Classification

Dose Levels

Results

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.

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.
Page 31 of 47

Table 3 Subchronic, Chronic and Other Toxicity Profile for Acibenzolar-S-methyl 

Guideline No.

Study Type

MRID No. (year)

Classification

Dose Levels

Results

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).

870.5100

Bacterial reverse mutation 

assay (Ames test)

441014247 (1993)

Acceptable/guideline

312.5, 625, 1250, 2500, 5000 

g/plate

Negative with and without S-9 activation at 5000 g/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 g/plate (+S-9)

30-86 to 2500 g/plate (-S-9)

Positive in S. typhimurium strain TA1537 at 277.8 g/plate and 

higher in the absence of S-9. Negative with S-9 activation at 5000 

g/plate and less.
Page 32 of 47

Table 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)

Test Material: NOA- 419191 

(by-product of acibenzolar-Smethyl)

44537024 (1998)

Acceptable/guideline

312.5 to 5000 g/plate (± S-9)

Negative with or without S-9 activation at 5000 g/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 g/plate (± S-9)

Negative with or without S-9 activation at 5000 g/plate and less

870.5300

In vitro mammalian gene 

mutation assay 

44014246 (1993)

Acceptable/guideline

3.70 to 100 g/ml (-S-9), 

37.04 to 1000 g/ml (+S-9)

Negative with S-9 activation up to 1000g/ml. Negative without 

S-9 activation up to 100g/ml.

Compound tested to cytotoxic concentrations.

870.5375

In vitro mammalian 

chromosome aberration (CHO 

cells)

44014245 (1993)

Acceptable/guideline

7.5 to 60 g/ml (-S-9 and +S9)

Suggestive of clastogenicity in the absence of S-9 activation at 30 

and 60 g/mL at the 18-hour cell harvest time; effect observed only 

in the presence of cytotoxicity. Increase in polyploid cells at 30 

and 60 g/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 g/ml

Negative at 500 g/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.

870.7600

Dermal penetration

NA NA

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.
Page 33 of 47

Table 3 Subchronic, Chronic and Other Toxicity Profile for Acibenzolar-S-methyl 

Guideline No.

Study Type

MRID No. (year)

Classification

Dose Levels

Results

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.

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.
Page 34 of 47

A.3 Toxicological Endpoints

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

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: In the previous risk assessment (D361893, 3/3/09) only the subpopulation females 

13-50 years old was assessed for acute dietary exposure based on in utero effects. However, 

based on a reevaluation of the DNT study regarding the potential for post-natal toxicity, the acute 

dietary analysis has been expanded to include children 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)
Page 35 of 47

[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 

especially in females at 2000 and 6000 ppm. Macroscopic and microscopic findings consistent 

 Chronic RfD = (NOAEL) 8.2 mg/kg = 0.082

 (Females 13-49/Young Children) (UF) 100
Page 36 of 47

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 

come from different studies conducted in different species. Typically, a combination of 

NOAELs/LOAELs from studies conducted in different species is not recommended. However, 
Page 37 of 47

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 45% 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. 

Uncertainty Factor (UF): 100 – 10x for interspecies extrapolation and 10x for intraspecies 

variation.

 Chronic RfD = 25 mg/kg/day (NOAEL) = 0.25 mg/kg/day

 (Adult Male) 100 (UF)
Page 38 of 47

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 45% 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
Page 39 of 47

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% 

carboxymethylceliulose (vehicle) on GD 6-15. On GD 21, dams were sacrificed, subjected to 
Page 40 of 47

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, 

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/
Page 41 of 47

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 

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 
Page 42 of 47

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 

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%). 
Page 43 of 47

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.

3. Reverse gene mutation, S. typhimuriumfE. Coli; Test Material: CGA-323060 (MRlD

44537026). This study was negative

CGA-362020, an isomer of acibenzolar-S-methyl, is a low level impurity arising from a new 

production process for acibenzolar-S-methyl, which has not yet been submitted to the Agency. 
Page 44 of 47

Trace levels of this isomer (<0.1%) were found in some batches of technical grade acibenzolarS-niethyl produced via the new production process. See the 6(a)(2) letter from Novartis, dated 

3/16/98, reporting the findings in this mutagenicity study and the above information regarding 

the formation of this isomer in the new production process. Presumably, the same isomer does 

not occur in the old production process which produced the test material (lot/batch # P.303011) 

that was used for virtually all the toxicity testing on acibenzolar-S-methyl up to this point in 

time.
Page 45 of 47

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
Page 46 of 47
Page 47 of 47

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 103l mol-1cm-1

288 nm ε : 5.4 103

324 nm ε : 7.2 103

European Commission, 

6506/VI/99-final, 5/21/02

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)