Bensulide Human Health Risk Assessment DP No. D428598 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

Date: 03/03/2016 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: Bensulide. Human Health Risk Assessment to Support Registration Review. 

PC Code: 009801 

Decision No.: 507866 

Petition No.: NA 

Risk Assessment Type: Single chemical/aggregate 

TXRNo.: NA 

MRIDNo.: NA 

FROM: 

DP Barcode: D428598 

Registration No.: 10163-200 

Regulatory Action: Registration Review 

Case No.: 2035 

CAS No.: 741-58-2 

40 CFR: 180.241 

TO: Margaret Hathaway, Chemical Review Manger 

Cathryn Britton, Team Leader 

Kevin Costello, Branch Chief 

Pesticide Re-evaluation Division (PRD; 7508P) 

Page 1 of97 
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1.0 Executive Summary ................................................................................................... 4

2.0 HED Recommendations ............................................................................................ 7

2.1 Data Deficiencies ........................................................................................................ 7

2.2 Tolerance Considerations ......................................................................................... 8

2.2.1 Enforcement Analytical Method .............................................................................. 8

2.2.2 Recommended Tolerances ........................................................................................ 8

2.2.3 International Harmonization .................................................................................... 9

2.3 Label Recommendations ........................................................................................... 9

2.3.1 Recommendations from Residue Reviews ............................................................... 9

2.3.2 Recommendations from Occupational Assessment ................................................ 9

2.3.3 Recommendations from Residential Assessment .................................................. 10

3.0 Introduction .............................................................................................................. 10

3.1 Chemical Identity ..................................................................................................... 10

3.2 Physical/Chemical Characteristics ......................................................................... 10

3.3 Pesticide Use Pattern ............................................................................................... 11

3.4 Anticipated Exposure Pathways ............................................................................. 13

3.5 Consideration of Environmental Justice ............................................................... 13

4.0 Hazard Characterization and Dose-Response Assessment .................................. 14

4.1 Toxicology Studies Available for Analysis ............................................................ 14

4.2 Absorption, Distribution, Metabolism, and Elimination (ADME) ..................... 15

4.2.1 Dermal Absorption .................................................................................................. 15

4.3 Toxicological Effects ................................................................................................ 15

4.3.1 Critical Durations of Exposure ............................................................................... 17

4.4 Literature Review on Neurodevelopment Effects ................................................. 18

4.5 Safety Factor for Infants and Children (FQPA SF) ............................................. 24

4.5.1 Completeness of the Toxicology Database ............................................................. 24

4.5.2 Evidence of Neurotoxicity ....................................................................................... 24

4.5.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal ....... 24

4.5.4 Residual Uncertainty in the Exposure Database .................................................. 25

4.6 Toxicity Endpoint and Point of Departure Selections .......................................... 25

4.6.1 Dose-Response Assessment ..................................................................................... 25

4.6.2 Oxon Toxicity Adjustment Factor ......................................................................... 28

4.6.3 Recommendation for Combining Routes of Exposures for Risk Assessment .... 29

4.6.4 Cancer Classification and Risk Assessment Recommendation ........................... 29

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

Assessment ................................................................................................................ 30

4.7 Endocrine Disruption .............................................................................................. 32

5.0 Dietary Exposure and Risk Assessment ................................................................ 33

5.1 Residues of Concern Summary and Rationale ..................................................... 33

5.2 Food Residue Profile ................................................................................................ 33

5.3 Water Residue Profile ............................................................................................. 34

5.4 Dietary Risk Assessment ......................................................................................... 35

5.4.1 Description of Residue Data Used in Dietary Assessment ................................... 35

5.4.2 Percent Crop Treated Used in Dietary Assessment .............................................. 36

5.4.3 Acute Dietary Risk Assessment .............................................................................. 36
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5.4.4 Steady-state Dietary Risk Assessment ................................................................... 37

5.4.5 Cancer Dietary Risk Assessment ............................................................................ 37

5.4.6 Summary Tables ...................................................................................................... 37

6.0 Residential (Non-Occupational) Exposure/Risk Characterization ..................... 38

6.1 Residential Handler Exposure ................................................................................ 38

6.2 Residential Post-Application Exposure ................................................................. 41

6.4 Residential Risk Estimates for Use in Aggregate Assessment ............................. 44

6.5 Residential Bystander Post-application Inhalation Exposure ............................. 44

6.6 Non-Occupational Spray Drift Exposure and Risk Estimates ............................ 45

7.0 Aggregate Exposure/Risk Characterization .......................................................... 50

7.1 Acute Aggregate Risk .............................................................................................. 50

7.2 Steady-state Aggregate Risk ................................................................................... 50

7.3 Cancer Aggregate Risk ............................................................................................ 50

8.0 Cumulative Exposure/Risk Characterization ....................................................... 50

9.0 Occupational Exposure/Risk Characterization .................................................... 51

9.1 Steady-State Handler Risk ...................................................................................... 51

9.2 Steady-State Post-Application Risk ....................................................................... 57

9.2.1 Dermal Post-Application Risk ................................................................................ 57

9.2.2 Inhalation Post-Application Risk ........................................................................... 59

10.0 Public Health and Pesticide Epidemiology Data................................................... 60

11.0 References ................................................................................................................. 61

Appendix A. Toxicology Profile and Executive Summaries .................................................. 64

A.1 Toxicology Data Requirements .............................................................................. 64

A.2 Summary of OPP’s ChE Policy & Use of BMD Modeling ................................... 65

A.3 Executive Summaries .............................................................................................. 73

Appendix B. Physical/Chemical Properties ............................................................................. 94

Appendix C. Review of Human Research................................................................................ 95

Appendix D. International Residue Limits Table ................................................................... 96

Appendix E. Comparison of Residue Levels of Bensulide and its Oxon .............................. 97
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1.0 Executive Summary 

Bensulide is an organophosphate (OP) herbicide registered for food/feed uses on bulb onion, 

garlic, shallots, leafy vegetable except brassica (crop group (CG) 4), leafy brassica vegetable 

(CG 5), fruiting vegetable (CG 8), cucurbit vegetable (CG 9), and a regional registration for use 

on carrots. Tolerances ranging from 0.10 to 0.15 ppm are established in the 40 CFR §180.241 

for residues of bensulide, including its oxygen analog, in/on these raw agricultural commodities 

(RACs). The emulsifiable concentrate (EC) end-use product Prefar 4E (EPA Reg. No. 10163-

200) is the only bensulide end-use product registered for use on food/feed crops, which is 

typically applied to the soil preplant or preemergence using ground equipment. In addition, 

bensulide is used for weed control in residential and occupational settings, and can be applied to 

golf courses and residential turf. Based on the registered use pattern for bensulide, humans may 

be exposed to bensulide in food and drinking water. Dermal and inhalation exposures are 

anticipated for residential and occupational handlers. In addition, dermal and incidental oral 

exposures are anticipated from post-application activities occurring in treated areas. There is 

also the potential for non-occupational exposure as a result of spray drift. 

Hazard Assessment 

Bensulide is a member of the organophosphate class of pesticides. Like other OPs, the initiating 

event in the adverse outcome pathway (AOP)/ mode of action (MOA) for bensulide involves 

inhibition of the enzyme acetylcholinesterase (AChE) via phosphorylation of the serine residue 

at the active site of the enzyme. This inhibition leads to accumulation of acetylcholine and 

ultimately to neurotoxicity in the central and/or peripheral nervous system. For bensulide, AChE 

inhibition is the most sensitive endpoint in the toxicology database in multiple species, durations, 

lifestages, and routes. Bensulide requires metabolic activation to an oxon to effectively inhibit 

AChE. OPs also exhibit steady-state AChE inhibition. After repeated dosing at the same dose 

level, the degree of inhibition comes into equilibrium with the production of new, uninhibited 

enzyme. As such, the endpoint selection for bensulide focuses on acute, single day effects and 

steady-state effects. 

The toxicology database for bensulide is complete for risk assessment, except for the 

requirement of a repeat dose inhalation toxicity study (Leshin, 2015, TXR # 0057280) and 

bensulide oxon comparative cholinesterase assays (CCA). Appropriate database uncertainty 

factors are applied for the lack of the inhalation study, and the oxon is considered to be 50X as 

potent as the parent in the absence of data (see section 4.6.2 for the rationale for 50X). 

Bensulide has high quality dose-response data across multiple lifestages and durations via the 

oral route for both red blood cell (RBC) and brain AChE inhibition (ChEI). Dermal routespecific endpoints could not be evaluated using benchmark dose (BMD) analysis, since the ChEI 

data from the dermal toxicity study would not model (no apparent dose response). An inhalation 

study is not available. Clinical signs of neurotoxicity, such as tremor, occur at doses much higher 

than those causing inhibition of AChE. 

The RBC AChE was generally more sensitive than the brain AChE to bensulide. The available 

AChE data across multiple lifestages (adults, pregnant adults, fetuses, juveniles) demonstrate that 

the PND 11 pups were generally more sensitive than the adult. In the gestational CCA, the fetus 
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was not more sensitive than the dam. The pregnant female in the gestational CCA was not more 

sensitive than the non-pregnant female in the repeated dose CCA. The adult female was typically 

more sensitive than the adult male, while the pup and fetus did not demonstrate sex-sensitivity. 

Bensulide is classified as “not likely to be carcinogenic in humans”, based on an absence of 

significant tumor increases in two adequate rodent carcinogenicity studies. A quantitative cancer 

risk assessment is not required. In acute oral lethality studies, bensulide is Toxicity Category II. 

The acute lethal toxicity is low for other routes, Toxicity Category III or IV for dermal and 

inhalation toxicity; and dermal and eye irritation. It is not a dermal sensitizer. 

Endpoints and Uncertainty Factors for Risk Assessment: The endpoint for all exposure 

scenarios is RBC ChEI and points of departure (PODs) were selected from high quality, wellconducted CCA rat studies. A POD for the acute dietary (all populations) exposure scenario was 

11 mg/kg/day; the POD for the steady-state dietary exposure, incidental oral, dermal, and 

inhalation scenarios was 6 mg/kg/day. The FQPA safety factor (10X) has been retained for 

infants, children, youths, and women of child-bearing age for all exposure scenarios (both 

occupational and residential) due to uncertainty in the human dose-response relationship for 

neurodevelopmental effects (see section 4.4). Additionally, for inhalation exposures, a database 

uncertainty factor of 30X was applied due to uncertainty in the human dose-response relationship 

for neurodevelopmental effects and lack of an inhalation toxicity study. For all exposure 

scenarios, interspecies (10X) and intraspecies (10X) uncertainty factors were applied in addition 

to the FQPA safety factor. As a result, a total uncertainty factor of 1000X was applied for all 

non-cancer exposure scenarios, except dietary exposures for the adult population subgroup 50-99 

years old (total uncertainty factor = 100X) and inhalation exposures (total uncertainty factor = 

3000X).

Dietary Exposure and Risk 

Acute and steady state dietary exposure assessments incorporated USDA Pesticide Data Program 

(PDP) monitoring data for bensulide and its oxon (when available), anticipated residues, default 

DEEM processing factors, and percent crop treated (CT) data. The Environmental Fate and 

Effects Division (EFED) provided daily time series outputs for the scenarios that provide the 

highest and lowest estimated drinking water concentrations (EDWC); groundwater in North 

Carolina Eastern Coastal Plain (Cotton) and surface water in California (Avocado), respectively. 

These concentrations were reported as the oxon and converted to bensulide using a 50x factor. 

Acute Dietary Exposure Assessment: Acute dietary assessments were conducted for food only, 

water only, and food and drinking water. The acute dietary exposure estimates from food alone 

are below HED’s level of concern (<100 % of the acute population adjusted dose (aPAD)) at the 

99.9th percentile of exposure, e.g. 46% of the aPAD for the most highly exposed population 

subgroup, children 3-5 years old. For food and drinking water, the dietary exposure is >10,000% 

and >1,600% of the aPAD at the 99.9th percentile of exposure using drinking water scenarios that 

provided the highest and lowest EDWC, respectively. Although for Adults 50-99 years old the 

FQPA SF is 1x, exposures were also of concern for food and drinking water. 

Steady-state Dietary Exposure Assessment: Steady-state assessments were conducted for food 

only, water only, and food and drinking water. The steady-state dietary exposure estimates from 
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food alone are below HED’s level of concern (<100 % of the steady-state population adjusted 

dose (ssPAD) at the 99.9th percentile of exposure, e.g. 80% of the ssPAD for the most highly 

exposed population subgroup, children 3-5 years old. For food and drinking water, the dietary 

exposure is >10,000% and >2,900% of the ssPAD at the 99.9th percentile of exposure using 

drinking water scenarios that provided the highest and lowest EDWC, respectively. Although for 

Adults 50-99 years old the FQPA SF is 1x, exposures were also of concern for food and drinking 

water. 

Residential Exposure and Risk 

Residential handler risk estimates for applying liquid and granule products to residential lawns 

are of concern at currently labeled use rates. For residential handlers, a total aggregated risk 

index (ARI) was used since the LOCs for dermal exposure (1000) and inhalation exposure 

(3000) are different. The target ARI is 1; therefore, ARIs of less than 1 are risk estimates of 

concern. Residential post-application risk estimates for turf uses were assessed using chemicalspecific turf transferable residue (TTR) data for a liquid formulation, and accounting for the 

difference in toxicity between the parent, bensulide, and the oxon (i.e., by applying a 50x toxicity 

adjustment factor). Risk estimates are of concern for dermal exposure for adults and children 

conducting activities on treated turf; for dermal exposure for adults and youths golfing; for handto-mouth exposure for children on treated turf; and for episodic granule ingestion exposure. 

Non-Occupational Exposure and Risk (Spray Drift and Bystander Volatilization)

Spray Drift: Risk estimates related to spray drift are of concern at various distances from the 

edge of the field for adults and children (1 to <2 years) depending on the spray drift scenario. 

For adults, the screening level scenario indicates the LOC is exceeded at a distance of less than 

25 feet for applications to vegetables and less than 75 feet for applications to golf courses. For 

children, the screening level scenario indicates the LOC is exceeded at a distance of less than 75 

feet for applications to vegetables and less than 150 feet for applications to golf courses. Drift 

reduction technologies, such as using coarser sprays and lowering boom height for groundboom 

sprayers, reduces risk concerns; however, there are still risk estimates of concern at the field 

edge in some cases. 

Volatilization/Residential Bystander: Volatilization of pesticides may be a source of postapplication inhalation exposure to individuals nearby pesticide applications. The Agency has 

developed a Volatilization Screening Tool and a subsequent Volatilization Screening Analysis, 

and during Registration Review, the Agency will utilize this analysis to determine if data (i.e., 

flux studies) or further analyses are required for bensulide. 

Aggregate Exposure and Risk 

Because there are risks of concern for the residential and drinking water exposure scenarios, a 

steady-state aggregate assessment was not conducted. The acute aggregate assessment consists 

of exposure through food and drinking water and is, therefore, reflected by the acute dietary 

exposure assessment. 

Occupational Exposure and Risk 

Occupational handler risk estimates (combined dermal + inhalation) were calculated for the 

registered uses on golf courses, turf, and vegetable crops. With the label-required personal 
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protective equipment (PPE), all combined handler risk estimates are of concern. Even with 

applying maximum PPE or engineering controls, many occupational handler risk estimates 

remain of concern. Since bensulide is applied to vegetables as a preplant or preemergence 

application only, occupational post-application dermal exposures are not anticipated for these 

uses. A quantitative occupational dermal post-application exposure assessment was, therefore, 

only conducted for the registered golf course use. Occupational post-application dermal risk 

estimates during maintenance activities on golf courses were of concern (i.e., MOEs are < 1,000) 

until 5 days after treatment. 

Human Studies Review

This risk assessment relies in part on data from studies in which adult human subjects were 

intentionally exposed to a pesticide or other chemical. Additional information on how these 

studies are considered can be found in Appendix C. 

2.0 HED Recommendations 

The hazard/toxicity, residue chemistry, occupational and residential databases are considered 

complete with the exception of the data requirements specified in Section 2.1. In addition, label 

recommendations are discussed in section 2.3. 

2.1 Data Deficiencies 

Hazard/Toxicity: A repeat dose inhalation toxicity study (Leshin, 2015, TXR # 0057280) and 

bensulide oxon comparative cholinesterase assays (CCA) are required. 

Residue Chemistry: (1) Three geographically representative field trials on non-bell peppers are 

required. Pending the submission of these data, the instructions for application to non-bell 

peppers should be removed from the label. This data deficiency was identified in the bensulide 

residue chemistry chapter in support of the Registration Eligibility Decision (RED; C. Eiden, 

D238417, 10/06/1997) and the registration review scoping document (T. Goodlow, D347549, 

06/10/2008). (2) Twelve crop field trials for bensulide on tomato grown in Mexico were 

required in the bensulide residue chemistry chapter in support of the Registration Eligibility 

Decision (RED; C. Eiden, D238417, 10/06/1997). The label from Mexico was submitted and 

describes a similar use pattern with the one registered in the US. The registrant expressed their 

intent to submit a proposal to address this data gap (conference call on 11/16/2015, coordinated 

by Margaret Hathaway). Pending the submission of these data, the twelve crop field trials are 

still required. 

Occupational and Residential: There are no data deficiencies. Chemical-specific turf 

transferable residue (TTR) data are available; DFR data are not required based on the registered 

use pattern. 
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2.2 Tolerance Considerations 

2.2.1 Enforcement Analytical Method 

Adequate methods are available for tolerance enforcement for plant commodities. The Pesticide 

Analytical Manual (PAM) Vol. II lists Gas Chromatography (GC) Method I, using either 

phosphorus-sensitive thermionic detection or flame photometric detection, for the determination 

of bensulide and bensulide oxygen analog in plant commodities. Thin layer chromatography 

(TLC) Method A is available for confirmation. Moreover, the PAM (Volume I, Appendix I) 

indicates that bensulide is recovered using Multiresidue Methods Sections 302 (Luke Method; 

Protocol D), 304 (Mills Method; Protocol E, fatty foods) and 303 (Mills, Onley, Gaither Method; 

Protocol E, non-fatty foods). No information regarding the recovery of bensulide oxygen analog 

using Multiresidue Methods is included in the PESTDATA database. 

2.2.2 Recommended Tolerances 

HED recommends modifying the tolerance expression and crop groups included in the CFR for 

bensulide. The tolerance expressions in the 40 CFR § 180.241 (a) and (c) need to be modified to 

include both coverage and compliance statements for enforcement purposes, as recommended in 

the Interim Guidance on Writing Tolerance Expressions (S. Knizner, 05/27/2009). The 

recommended tolerance expressions are: 

 

(a) General. “Tolerances are established for residues of the herbicide bensulide, including its 

metabolites and degradates, in or on the commodities in the following table. Compliance with the 

tolerance levels specified in the table below is to be determined by measuring only bensulide, S-

(O,O-diisopropyl phosphorodithioate) ester of N-(2-mercaptoethyl) benzenesulfonamide, and its 

oxygen analog, S-(O,O-diisopropyl phosphorothioate) of N-(2-mercaptoethyl) 

benzenesulfonamide, in or on the commodity.” 

 

(c) Tolerance with regional registration. “Tolerances with regional registration, as defined in 

§180.1(l), are established for residues of the herbicide bensulide, including its metabolites and 

degradates, in or on the commodities in the following table. Compliance with the tolerance levels 

specified in the table below is to be determined by measuring only bensulide, S-(O,O-diisopropyl 

phosphorodithioate) ester of N-(2-mercaptoethyl) benzenesulfonamide, and its oxygen analog, S-

(O,O-diisopropyl phosphorothioate) of N-(2-mercaptoethyl) benzenesulfonamide, in or on the 

commodity.” 

 

Since non-bell pepper field trial data are not available, HED concludes that the tolerance for 

fruiting vegetable crop group 8 should be deleted and those for bell pepper and tomatillo 

established in support of domestic registrations. Additional data are required to support a 

tolerance for tomato imported from Mexico. The establishment of a tolerance for tomato may be 

recommended if these data (or registrant proposal) are received from the registrant and 

considered adequate to support this use. Tolerances included in the 40 CFR 180.241 need to be 

modified as specified in the table below. 
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Table 2.2.2. Tolerance Summary for Bensulide. 

Commodity Established 

Tolerance (ppm) 

HED-Recommended 

Tolerance (ppm) 

Comments 

(correct commodity definition) 

Vegetable, fruiting, group 8 0.10 Remove 

Pepper, bell None 0.10 

Tomatillo None 0.10 

Tomato, subgroup 8-10A* None 0.10 

*May be established pending review of required data in support of import use. 

2.2.3 International Harmonization 

There are no Codex, Mexican or Canadian maximum residue limits established for bensulide. 

Therefore, harmonization is not germane to this assessment. 

2.3 Label Recommendations 

2.3.1 Recommendations from Residue Reviews 

A summary of the risk estimates has been provided, and shows that there are dietary risk 

estimates of concern for registered uses of bensulide. The following recommendations are based 

on the review of the label of bensulide’s end use product Prefar 4-E (EPA Reg. No. 10163-200, 

12/13/2013): 

 

 The current label of Prefar 4-E includes instructions for use on non-bell peppers such as 

chili peppers, cooking peppers, pimentos and sweet peppers. A magnitude of residue 

study for bensulide in/on non-bell peppers has been required in the RED and scoping 

document. Alternatively, it was indicated that the registrant could restrict use to bell 

peppers. Since these data have not been received, HED recommends that the bensulide 

product label restrict the use to only bell peppers. Moreover, reference to the fruiting 

vegetables crop group needs to be removed. 

 

 The maximum seasonal application rate for cucurbit vegetables, tomatillo and bell 

peppers needs to be specified on the label of Prefar 4-E. A maximum seasonal 

application rate of 6 lbs ai/A is supported by adequate data for crops under these crop 

groups. 

2.3.2 Recommendations from Occupational Assessment 

No label recommendations based on the occupational assessment have been identified. A 

summary of the risk estimates has been provided, and shows that there are risk estimates 

of concern for registered uses of bensulide based on the use information, label-required personal 

protective equipment (PPE), and REIs (golf course uses only). 

 
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2.3.3 Recommendations from Residential Assessment 

No label recommendations based on the residential assessment have been identified. A summary 

of the risk estimates has been provided, and shows that there are risk estimates of concern for 

registered uses of bensulide based on the current use information. 

3.0 Introduction

3.1 Chemical Identity

Table 3.1. Bensulide and Bensulide Oxon Nomenclature. 

Compound Chemical Structure 

Common name Bensulide 

IUPAC name O,O-diisopropyl-S-2-phenylsulfonylaminoethylphosphorodithioate 

CAS name S-(O,O-diisopropyl phosphorodithioate) ester of N-(2-mercaptoethyl) 

benzenesulfonamide 

CAS # 741-58-2 

Compound Chemical Structure 

Common name Bensulide Oxon 

IUPAC name O,O-diisopropyl-S-2-phenylsulfonylaminoethylphosphorothioate 

CAS name S-(O,O-diisopropyl phosphorothioate) of N-(2-mercaptoethyl) 

benzenesulfonamide 

CAS # 20243-81-6 

3.2 Physical/Chemical Characteristics

The physicochemical properties of bensulide and its oxon are summarized in Appendix B. 

Bensulide (5.6 mg/L) is moderately soluble in water; however, it is less soluble than its oxon 

(461 mg/L, EPISuite v. 4.10). Both compounds have low volatility and the oxon has a low 

partition coefficient. Bensulide is slightly mobile in the four soils tested (Koc's ranged from 

1,433 to 4,326 mL/g) based on an acceptable study; however, its major degradate bensulide oxon 

(average Koc = 557) ranged from moderately mobile to highly mobile in the same four test soils. 
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3.3 Pesticide Use Pattern

Bensulide is used for weed control in residential and occupational settings. Bensulide can be 

applied to vegetable crops, golf courses, and residential turf. Prefar 4 E (EPA Reg. No. 10163-

200) is the only bensulide end-use product registered for food uses on bulb onion, garlic, 

shallots, leafy vegetable except brassica (CG 4), leafy brassica vegetables (CG 5), fruiting 

vegetable (CG 8), cucurbit vegetables (CG 9), regional use on carrots grown in Texas, as well as 

non-food uses on golf courses and home lawns. A summary of bensulide uses is listed in Table 

3.3. 

Table 3.3. Summary of Directions for Use of Bensulide. 

Applic. Timing, 

Type, and 

Equip. 

Formulation 

[EPA Reg. 

No.] 

Applic. 

Rate (lb 

ai/A) 

Max. 

Seasonal 

Applic. Rate 

(lb ai/A) 

PHI (days) Use Directions and Limitations 

Turf (Golf Courses and Residential Lawns) 

Groundboom or 

low pressure 

turfgun, 

Handwand for 

spot treatment 

Watered in 

Liquid 

4 lb ai/gal 

(46% ai) 

EPA Reg. No. 

2217-696 

12.5 lb 

ai/acre 25 lb ai/acre NA PPE: baseline, gloves, PF5 respirator

Tractor drawn 

spreader, Push 

type spreader 

Watered in 

Granular 

7% ai 

EPA Reg. No. 

2217-778 

12.6 lb 

ai/acre 

25.2 lb 

ai/acre NA 

PPE: Loaders, spreader applicator: 

Coveralls, gloves, PF5 respirator 

All others: baseline, gloves 

For hire applicators must wear PF5 

respirator 

Cannot be applied aerially 

Only on lawns 

Push type 

spreader only 

Granular 

3.6% ai 

EPA Reg. No. 

2217-838 

12.5 lb 

ai/acre NA NA 

No PPE listed 

Hand-held rotary broadcast spreader 

prohibited 

Tractor drawn 

spreader, push 

type spreader 

Granular 

8.5% ai 

EPA Reg. No 

9198-172 

12.4 lb 

ai/acre NA NA 

PPE: loaders, spreader applicator: 

coveralls, gloves, PF5 respirator 

All others: baseline, gloves 

Golf courses only 

Tractor drawn 

spreader or push 

type spreader 

Watered in 

Granular 

5.25% ai 

EPA Reg. No. 

9198-176 

16 lb ai/acre 32 lb ai/acre NA 

Not for sale or use by homeowners 

PPE: push spreaders and loader: 

coveralls, gloves, PF5 respirator 

Other applicators: baseline, gloves 

For hire applicators must wear PF5 

respirator 

Golf courses only 

Groundboom, low 

pressure turfgun, 

LP Handwand for 

spot treatment 

Liquid 

46.4% ai 

4 lb ai/gal 

EPA Reg. No. 

10163-196 

12.5 lb 

ai/acre 25 lb ai/acre NA 

PPE: Mixer/loader: baseline, gloves, 

PF5 respirator 

Applicator and other: baseline, 

gloves; for hire applicators must 

wear PF5 respirator 

Golf courses only 

Watered in 

Granular 

12.5% ai 

EPA Reg. No. 

10163-198 

12.5 lb 

ai/acre 25 lb ai/acre NA 

PPE: Loaders, spreader applicator: 

coveralls, gloves, respirator 

Other applicators: baseline, gloves, 

respirator 

Golf courses only 

Tractor drawn 

Granular 

3.6% ai 

12.5 lb 

ai/acre NA NA PPE: Loaders and spreader 

applicators: coveralls, gloves, 
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Table 3.3. Summary of Directions for Use of Bensulide. 

Applic. Timing, 

Type, and 

Equip. 

Formulation 

[EPA Reg. 

No.] 

Applic. 

Rate (lb 

ai/A) 

Max. 

Seasonal 

Applic. Rate 

(lb ai/A) 

PHI (days) Use Directions and Limitations 

spreader or pushtype spreader 

 Watered in 

EPA Reg. No. 

10163-199 

eyewear, for-hire applicators must 

wear respirator 

All other applicators: baseline, 

gloves, respirator 

Hand-held rotary spreaders are 

prohibited 

Golf courses only 

Tractor drawn 

spreader or pushtype spreader 

Watered in 

Granular 

7% ai 

EPA Reg. No. 

10163-204 

12.6 lb 

ai/acre 25 lb ai/acre NA 

PPE: loaders and spreader 

applicators: coveralls, gloves, 

respirator; others: baseline, gloves, 

for-hire applicators must wear 

respirator 

Residential lawns 

only 

RTU Garden hose 

sprayer 

46.4% ai 

EPA Reg. No. 

10163-205 

16 fl oz 

product/ 

2500 sq. ft 

8.7 lb ai/A 

NA NA No PPE listed 

Cucurbit vegetables 

Groundboom, 

Chemigation, 

Handgun 

Preplant or 

preemergence 

Emulsifiable 

Liquid 

4 lb ai/gal 

EPA Reg. No. 

10163-200 

6 lb ai/acre NA NA 

PPE: baseline, gloves; Mixers, 

loaders and commercial applicators 

must wear a PF5 respirator 

May not be applied by aircraft 

9 lb ai/acre NA NA SLN label – CA 960003 

Brassica (cole) leafy vegetables; leafy vegetables 

Groundboom, 

Chemigation, 

Handgun 

Preplant or 

preemergence 

Emulsifiable 

Liquid 

4 lb ai/gal 

EPA Reg. No. 

10163-200 

6 lb ai/acre 6 lb ai/acre NA 

PPE: baseline, gloves; Mixers, 

loaders and commercial applicators 

must wear a PF5 respirator 

Do not use on spinach or Swiss 

Chard 

May not be applied by aircraft 

9 lb ai/acre 9 lb ai/acre NA SLN label – NJ 070001 

Fruiting vegetables 

Groundboom, 

Chemigation, 

Handgun 

Preplant or 

preemergence 

Emulsifiable 

Liquid 

4 lb ai/gal 

EPA Reg. No. 

10163-200 

6 lb ai/acre NA NA 

PPE: baseline, gloves; Mixers, 

loaders and commercial applicators 

must wear a PF5 respirator 

May not be applied by aircraft 

Carrots 

Groundboom, 

Chemigation, 

Handgun 

Preplant or 

Preemergence 

Emulsifiable 

Liquid 

4 lb ai/gal 

EPA Reg. No. 

10163-200 

5 lb ai/acre 5 lb ai/acre NA 

PPE: baseline, gloves; Mixers, 

loaders and commercial applicators 

must wear a PF5 respirator 

May not be applied by aircraft 

Dry Bulb Vegetables 

Groundboom, 

Chemigation, 

Handgun 

Emulsifiable 

Liquid 

4 lb ai/gal 

6 lb ai/acre 6 lb ai/acre NA 

PPE: baseline, gloves; Mixers, 

loaders and commercial applicators 

must wear a PF5 respirator 
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Table 3.3. Summary of Directions for Use of Bensulide. 

Applic. Timing, 

Type, and 

Equip. 

Formulation 

[EPA Reg. 

No.] 

Applic. 

Rate (lb 

ai/A) 

Max. 

Seasonal 

Applic. Rate 

(lb ai/A) 

PHI (days) Use Directions and Limitations 

Preplant or 

Preemergence 

EPA Reg. No. 

10163-200 

May not be applied by aircraft 

NA = Not Applicable for preplant application or application preemergence of the crop. 

3.4 Anticipated Exposure Pathways 

Humans may be exposed to bensulide in food and drinking water because this chemical may be 

applied directly to growing crops and application may result in bensulide reaching surface and 

ground water sources of drinking water. Conversion of bensulide into bensulide oxon (13.8%) 

has been observed under aerobic soil conditions while bensulide may be totally converted into 

bensulide oxon during the chlorination processes (Kamel et al.; 2009). Moreover, the oxon has 

been observed in samples of lettuce and carrot. There are residential uses of bensulide for weed 

control; residential handlers may be exposed during application, and adults and children may be 

exposed after application in treated areas. In an occupational setting, applicators may be exposed 

while handling the pesticide prior to application, as well as during application. Since bensulide 

is applied to crops preplant or preemergence, occupational post-application exposure is not 

anticipated from those registered uses. However, there is a potential for post-application 

exposure for workers performing activities in treated golf courses. 

3.5 Consideration of Environmental Justice

Potential areas of environmental justice concerns, to the extent possible, were considered in this 

human health risk assessment, in accordance with U.S. Executive Order 12898, "Federal Actions 

to Address Environmental Justice in Minority Populations and Low-Income Populations," ( 

http://www.archives.gov/federal-register/executive-orders/pdf/12898.pdf). As a part of every 

pesticide risk assessment, OPP considers a large variety of consumer subgroups according to 

well-established procedures. In line with OPP policy, HED estimates risks to population 

subgroups from pesticide exposures that are based on patterns of that subgroup’s food and water 

consumption, and activities in and around the home that involve pesticide use in a residential 

setting. Extensive data on food consumption patterns are compiled by the USDA under the 

National Health and Nutrition Survey/What We Eat in America (NHANES/WWEIA) and are 

used in pesticide risk assessments for all registered food uses of a pesticide. These data are 

analyzed and categorized by subgroups based on age and ethnic group. Additionally, OPP is 

able to assess dietary exposure to smaller, specialized subgroups and exposure assessments are 

performed when conditions or circumstances warrant. Whenever appropriate, non-dietary 

exposures based on home use of pesticide products and associated risks for adult applicators and 

for toddlers, youths, and adults entering or playing on treated areas post-application are 

evaluated. Further considerations are currently in development as OPP has committed resources 

and expertise to the development of specialized software and models that consider exposure to 

bystanders and farm workers as well as lifestyle and traditional dietary patterns among specific 

subgroups. 
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4.0 Hazard Characterization and Dose-Response Assessment 

Bensulide is a member of the organophosphate class of pesticides. Like other OPs, the initiating 

event in the adverse outcome pathway (AOP), also often called the mode of action (MOA), for 

bensulide involves inhibition of the enzyme acetylcholinesterase via phosphorylation of the 

serine residue at the active site of the enzyme. This inhibition leads to accumulation of 

acetylcholine and ultimately to neurotoxicity in the central and/or peripheral nervous system (see 

Figure 1). For bensulide, acetylcholinesterase inhibition (ChEI) is the most sensitive endpoint in 

the toxicology database in multiple species, durations, lifestages, and routes. ChEI is the focus of 

this hazard characterization; the availability of reliable ChEI dose-response data is one of the key 

determinants in evaluating the toxicology database. 

Figure 1. Adverse outcome pathway for OPs 

4.1 Toxicology Studies Available for Analysis 

The database is considered complete for risk assessment, with the exception of a repeat dose 

inhalation toxicity study and a bensulide oxon CCA (data gaps). The Health Effect Divisions 

(HED’s) Hazard Science Policy Council (HASPOC) determined, based on a weight of evidence 

(WOE) approach that a subchronic inhalation toxicity study is required for bensulide due to 

unacceptable inhalation risk estimates using the current POD from an oral study (Leshin, 2015, 

TXR # 0057280). The HASPOC also determined that the immunotoxicity study is not required 

for bensulide (Van Alstine, 2013; TXR # 0056738), as well as the 6-month ocular toxicity study 

in the dog, and developmental and subchronic neurotoxicity studies (Leshin, 2015, TXR # 

0057280). Although oxon CCA data are not available for bensulide, EPA plans to move forward 

with the bensulide human health risk assessment without toxicity data for bensulide’s oxon 

degradate. In lieu of bensulide-specific oxon CCA data, EPA will use an oxon toxicity 

adjustment factor of 50X in its calculations (see section 4.6.2 for the rationale for 50X). This 

value considers the data derived toxicity adjustment factor (TAF) EPA has identified among 

oxon metabolites for other organophosphates, with an additional margin of safety included due to 

the uncertainty in extrapolating oxon potency data across chemicals. Toxicology data 

requirements and confirmation that bensulide meets these requirements are presented in 

Appendix A.1. The toxicology database includes the following toxicity studies: 

 Subchronic oral in rat, mouse, and dog 

 21-day dermal in rat (two studies) 

 Developmental in rat and rabbit 

 2-generation reproduction in rat 

 Chronic oral in dog, mouse (carcinogenicity), and rat (combined chronic toxicity/ 

carcinogenicity) 

Target 

Tissue Dose 

Phosphorylation 

of the active site 

of AChE 

Neurotoxicity Accumulation of 

acetylcholine 
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 Acute neurotoxicity in rat; delayed neurotoxicity study in hen, comparative 

cholinesterase assay (CCA) study (gestational, repeated-dose, and acute) in parent but not 

oxon 

 Other studies, such as mutagenicity battery, acute 6-pack, and metabolism study 

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

Bensulide is a phosphorothioate and needs to be bioactivated in vivo to its oxygen analog to exert 

its toxic action (see chemical structure in Table 3.1.1). Seven days after a single oral dose of 

14C-bensulide to rats, radioactivity was excreted primarily in the urine in males (70.2-78.6% of 

administered dose [AD]) and females (75.2-88.4% AD), with the rest being in the feces (13.6-

22.4% AD in males, 8.3-19.6% AD in females). Females excreted the radioactivity faster than 

males: the females' excretion was almost complete 48 hours after dosing, whereas the males had 

excreted about 65-70% of the radioactivity at that time. Biliary excretion is minimal. Seven days 

after administration, the highest concentration of radioactivity in selected tissues in the ADME 

study was found in whole blood, associated with the cellular component. Whole body 

autoradiography showed a much higher level of radioactivity remaining in males after 24 hours 

than in females. Four metabolites were identified. One was the primary urinary metabolite and 

the other identified metabolites were found in the feces. The proposed formation of two 

metabolites involved the cleavage of the PO2[CH(CH3)2]2 moiety of bensulide, followed by 

methylation and oxidation of the sulphur atom. Conjugation with glycine or carboxylation and 

oxidative desulphuration is proposed to lead to the other two identified metabolites. 

4.2.1 Dermal Absorption 

Although there are no dermal absorption studies submitted for bensulide, a dermal absorption 

factor is needed for risk assessment, since the route-specific dermal toxicity study could not be 

modeled due to a lack of dose response, and an oral endpoint was selected for the dermal 

exposure assessment. A dermal absorption value of 10% was estimated for dermal risk 

assessment. This value was derived from a comparison of the effects observed in the oral 

developmental toxicity (95 mg/kg/day based upon tremors and decreased body weight) and 21-

day dermal toxicity studies (1000 mg/kg/day [NOAEL]) in rats. 

4.3 Toxicological Effects 

Bensulide is an OP with a neurotoxic AOP; neurotoxicity is the most sensitive effect in all 

species, routes, and lifestages and is being used in deriving points of departure (acute = 11 

mg/kg/day; steady-state = 6 mg/kg/day). Bensulide has dose response data across multiple 

lifestages, durations, and routes for both RBC and brain ChEI. Many of these studies have been 

evaluated using benchmark dose modeling techniques. The CCA, in particular, provided 

excellent dose-response data for modeling. 

Bensulide requires bioactivation to the oxon to allow ChEI; however, no data were submitted 

regarding the toxicity of the oxon. 
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The RBC AChE was more sensitive than the brain AChE to bensulide in every analysis (all 

studies, durations, lifestages, and routes), except the adult males in the acute CCA study. The 

adult female was typically more sensitive than the male, while the pup and fetus did not 

demonstrate sex-sensitivity. 

Clinical signs of neurotoxicity can be found throughout the database of experimental toxicity 

studies at doses much higher (≥95 mg/kg/day) than those doses causing ChEI. Some of the 

clinical signs included diarrhea, flaccid abdominal and/or body tone, pinpoint pupils, salivation, 

lacrimation, decreased respiration, hypothermia, tremors, hypoactivity, dehydration, fur staining, 

decreased arousal and locomotor activity. No effects were noted on neuropathology; however, 

bensulide did not induce acute delayed neurotoxicity in the hen. 

Although the nervous system was the principal target, the liver was also affected. Liver toxicity 

(increased organ weight, increased serum ALT, hypertrophy, liver enlargement, liver lipid 

deposits, pigmentation, and/or vacuolation) was often noted in rat, mouse, and dog at doses of 30 

mg/kg/day or greater. 

Increased sensitivity was not evident in the developmental studies. No developmental toxicity 

was observed in the rat at dose levels resulting in maternal toxicity (95 mg/kg/day resulted in 

tremors and ChEI). Likewise, no developmental toxicity was observed in the rabbit at dose levels 

resulting in maternal toxicity (80 mg/kg/day resulted in decreased body weights and body weight 

loss). In the rat 2-generation reproductive toxicity study, systemic toxicity was noted in offspring 

(93 mg/kg/day resulted in decreased F2 pup survival) at a lower dose than in adults (no systemic 

toxicity observed). However, ChEI provides the most sensitive endpoint for bensulide, and 

although ChEI was not measured in pups in the reproduction study, ChEI in adults (occurring at 

mid- and/or high dose) in this study is protective for the decreased F2 pup survival (as the 

decrease in survival was noted only at the high dose). In the comparative cholinesterase assays, 

the ChEI observed in the PND 11 pup was generally greater than the inhibition observed in the 

adult in both the acute and repeated phases of the CCA study. In the gestational CCA, the fetus 

was not more sensitive than the dam. The pregnant female in the gestational CCA was not more 

sensitive than the non-pregnant female in the repeated dose CCA. 

Bensulide is classified as “not likely to be carcinogenic in humans” based on the absence of 

treatment-related tumors in two adequate rodent carcinogenicity studies. There is no 

mutagenicity concern for bensulide. 

The acute (lethal) oral toxicity of bensulide is Toxicity Category II. The acute lethal toxicity is 

low for other routes, Toxicity Category III or IV for dermal and inhalation toxicity; and dermal 

and eye irritation. It is not a dermal sensitizer. 

More detail concerning the characterization and quantification of the toxic effects of bensulide is 

provided in Appendix A.2. OPP’s cholinesterase (ChE) policy and use of BMD modeling is also 

described. A table of the benchmark modeling results is provided in Appendix A.2 (Tables 

A.2.1 and A.2.2). A toxicity profile table can be found following the benchmark modeling table 

in Appendix A.2 (Tables A.2.3 and A.2.4). It is noted that the toxicity profile table has not been 
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updated to include BMD results since these can be found in the previous tables (A.2.1 and 

A.2.2). 

4.3.1 Critical Durations of Exposure 

One of the key elements in risk assessment is the appropriate integration of temporality between 

the exposure and hazard assessments. One advantage of an AOP understanding is that human 

health risk assessments can be refined, focused on the most relevant durations of exposure. Table 

4.3.1.1 provides a summary of the selected results from experimental toxicology studies in which 

ChEI of adult female rat RBC was selected to highlight the effect of duration. Data from the 

adult female rat RBC ChEI was presented because this sex and compartment were the most 

sensitive to the effects of bensulide and provided the most data which modeled successfully. 

Only the BMD10 results are shown, because the central estimate is used for purposes of 

comparison according to the BMD guidance. 

 

Table 4.3.1.1. Comparison of Bensulide BMD10 Results (mg/kg/day) for RBC ChEI over Time in Adult 

Female Rats 

Duration of dosing 

Females 

BMD10 MRID#, Test 

0.67 days 27.2 49433502, Acute CCA 

10 days 18.7 49466201, Repeated Dose CCA 

13 days 12.0 49454001, Gestational CCA 

13 weeks 9.5 43919601. 13-Week Oral Tox 

25 weeks 7.3 44161101, 104-Week Chronic Tox/Carc 

51 weeks 4.2 44161101, 104-Week Chronic Tox/Carc 

77 weeks 6.6 44161101, 104-Week Chronic Tox/Carc 

103 weeks 11.7 44161101, 104-Week Chronic Tox/Carc 

CCA = Comparative cholinesterase assay 

Tox = Toxicity; Carc = Carcinogenicity 

The following text provides an analysis of the temporal pattern of AChE inhibition from acute, 

single dosing and repeated dosing studies in laboratory animals for bensulide. This analysis 

provides the basis for determining which exposure durations are appropriate for assessing human 

health risk. 

OPs exhibit a phenomenon known as steady-state ChEI. After repeated dosing at the same dose 

level, the degree of inhibition comes into equilibrium with the production of new, uninhibited 

enzyme. At this point, the amount of ChEI at a given dose remains relatively consistent across 

duration. In general, OPs reach steady-state within 2-3 weeks. For bensulide, the results in Table 

4.3.1.1 show a pattern of steady-state reached by 13 days of exposure. As demonstrated in the 

table, the BMDs decrease from acute to repeat exposure, as is typically observed with OP 

administration. For instance, the BMD10 in adult female rats was 27 mg/kg in the acute CCA 

study (oral gavage) and 19 mg/kg/day after 10 days. Although there was variation, this can be 

expected from using different studies, due to differences in dose selection leading to differences 

in the quality of modeling. In this case, the BMD10 after 13 days (12.0 mg/kg/day) is the same as 
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after 103 weeks (11.7 mg/kg/day). Furthermore, considering the variation in BMD10 values seen 

in the bensulide data sets, the BMD10 after 10 days (18.7 mg/kg/day) can be considered similar to 

that after 13 days. Thus, in addition to the consistency across durations, the data across multiple 

studies are similar. Given the results in Table 4.3.1.1, for bensulide, single-day and steady-state 

durations are appropriate for human health risk assessment. As such, the endpoint selection for 

bensulide focuses on acute, single-day effects and steady-state effects (10 days and longer). 

 

Although the durations of the toxicity and exposure assessments may differ among the OPs, an 

exact match is not necessary and would suggest a level of precision that the toxicity data do not 

support. As such, the single chemical OP assessments will evaluate steady-state, instead of the 

typical chronic duration dietary assessment. The steady-state point of departure is protective of 

any exposure duration longer than 10 days for bensulide, including chronic exposure, since 

cholinesterase inhibition does not increase after reaching maximum inhibition or steady-state. 

Although there are data at a shorter time period than 21 days (i.e., 10 days), exposure 

assessments of 21 days and longer will be conducted for all routes of exposure (i.e., oral, dermal 

and inhalation) for all single chemical OP assessments. Although the durations of the toxicity 

and exposure assessments may differ, an exact match is not necessary and would suggest a level 

of precision that the toxicity data do not support. Given this, the 21-day and longer exposure 

assessment is scientifically supportable and also provides consistency with the OP cumulative 

risk assessment (OP Cumulative Risk Assessment (CRA); 2002, 2006) and across the single 

chemical risk assessment for the OPs. 

Given the results in Table 4.3.1.1 above, acute (single day) and steady-state durations are 

appropriate for human health risk assessment. As such, the endpoint selection focuses on acute, 

single day effects and steady-state effects. For purposes of consistency with the OP cumulative 

risk assessment (CRA) and other OPs, exposure assessments of 21 days and longer will be 

conducted. 

4.4 Literature Review on Neurodevelopment Effects 

For the OPs, historically the Agency has used inhibition of AChE as the POD for human health 

risk assessment; at present time, this policy continues. This science policy is based on decades 

of work which shows that AChE inhibition is the initial event in the pathway to acute cholinergic 

neurotoxicity. The use of AChE inhibition data for deriving PODs was supported by the FIFRA 

SAP (2008, 2012) for chlorpyrifos as the most robust source of dose-response data for 

extrapolating risk and is the source of data for PODs for bensulide. A detailed review of the 

epidemiological studies used in this review can be found either in the 2014 chlorpyrifos revised 

draft human health risk assessment ((D424485, D. Drew et al., 12/29/2014) or in the 2015 

literature review for other organophosphates (OPP/USEPA; D331251; 9/15/15). 

Newer lines of research on OPs in the areas of potential AOPs, in vivo animal studies, and 

notably epidemiological studies in mothers and children, have raised some uncertainty about the 

Agency’s risk assessment approach with regard to the potential for neurodevelopmental effects 

in fetuses and children. Many of these studies have been the subject of review by the Agency 

over the last several years as part of efforts to develop a risk assessment for chlorpyrifos 
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(D424485, D. Drew et al., 12/29/2014). Initially, the Agency focused on studies from three US 

cohorts: 1) The Mothers and Newborn Study of North Manhattan and South Bronx performed by 

the Columbia Children’s Center for Environmental Health (CCCEH) at Columbia University; 2) 

the Mt. Sinai Inner-City Toxicants, Child Growth and Development Study or the “Mt. Sinai 

Child Growth and Development Study;” and 3) the Center for Health Assessment of Mothers and 

Children of Salinas Valley (CHAMACOS) conducted by researchers at University of California 

Berkeley. The Agency has evaluated these studies and sought external peer review (FIFRA SAP 

reviews in 2008 and 2012; federal panel, 20131

) and concludes they are of high quality. In the 

three US epidemiology cohort studies, mother-infant pairs were recruited for the purpose of 

studying the potential health effects of environmental exposures during pregnancy on subsequent 

child development. Each of these cohorts evaluated the association between prenatal chlorpyrifos 

and/or OP exposure (with adverse neurodevelopmental outcomes in children through age 7 

years. For the 2014 chlorpyrifos revised human health risk assessment (D424485, D. Drew et 

al., 12/29/2014), EPA included epidemiologic research results from these three US prospective 

birth cohort studies but primarily focused on the results of CCCEH since this cohort has 

published studies on the association between cord blood levels of chlorpyrifos and 

neurodevelopmental outcomes. The Agency retained the FQPA 10X Safety Factor (SF) in the 

2014 chlorpyrifos revised risk assessment, in large part, based on the findings of these studies. 

In the 2015 updated literature review (OPP/USEPA; D331251; 9/15/15), the Agency conducted a 

systematic review expanding the scope of the 2012/2014 review focused on US cohort studies 

with particular emphasis on chlorpyrifos. The expanded 2015 review includes consideration of 

the epidemiological data on any OP pesticide, study designs beyond prospective cohort studies, 

and non-U.S. based studies. The updated literature review identified seven studies which were 

relevant (Bouchard et al., 2010; Fortenberry et al., 2014; Furlong et al., 2014; Guodong et al., 

2012; Oulhote and Bouchard, 2013; Zhang et al., 2014; Shelton et al., 2014). These seven 

studies have been evaluated in context with studies from the 2012/2014 review (D424485, D. 

Drew et al., 12/29/2014). Only a brief summary is provided below. 

The OP exposure being assessed in many of these studies used concentrations of urinary dialkyl 

phosphate metabolites (DAPs) as the urinary biomarker. Total DAPs is a non-specific measure 

of OP exposure and is the sum of six separate molecules - three dimethyl alkylphosphate 

(DMAP) molecules of DMP, DMTP, DMDTP, and three diethyl alkylphosphate (DEAP) 

molecules of DEP, DETP, and DEDTP. Each metabolite is a breakdown product from multiple 

OPs (Table 4.4.-1; CDC, 2008)2

. Specifically, DMP, DMTP, and DMDTP are associated with 

18, 13, and 5 OPs, whereas DEP, DETP, and DEDTP are associated with 10, 10, and 4 OPs, 

respectively. Thus, using urinary DAPs alone as an exposure measure, it is not possible to 

separate the exposure and associated effects for single, specific OPs. 

 

1 http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2008-0850-0170 2 http://www.cdc.gov/nchs/data/nhanes/nhanes_03_04/l26opd_c_met_organophosphorus_pesticides.pdf
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Table 4.4.1.CDC Table of organophosphate pesticides and their dialkyl phosphate metabolites (2008). 

Pesticide DMP DMTP DMDTP DEP DETP DEDTP 

Azinphos methyl X X X 

Chlorethoxyphos X X 

Chlorpyrifos X X 

Chlorpyrifos methyl X X 

Coumaphos X X 

Dichlorvos (DDVP) X 

Diazinon X X 

Dicrotophos X 

Dimethoate X X X 

Disulfoton X X X 

Ethion X X X 

Fenitrothion X X 

Fenthion X X 

Isazaphos-methyl X X 

Malathion X X X 

Methidathion X X X 

Methyl parathion X X 

Naled X 

Oxydemeton-methyl X X 

Parathion X X 

Phorate X X X 

Phosmet X X X 

Pirimiphos-methyl X X 

Sulfotepp X X 

Temephos X X 

Terbufos X X X 

Tetrachlorviphos X 

Trichlorfon X 

DMP = dimethylphosphate; DEP = diethylphosphate; DMTP = dimethylthiophosphate; DMDTP = 

dimethyldithiophosphate; DETP = diethylthiophosphate; DEDTP = diethyldithiophosphate. 

For studies which measured urinary 3,5,6-trichloro-2-pyridinol (TCPy) (e.g., Fortenberry et al., 

2014; Eskenazi et al., 2007; Whyatt et al., 2009), this metabolite can be derived from 

chlorpyrifos, chlorpyrifos-methyl, and the herbicide triclopyr. TCPy is also the primary 

environmental degradate of chlorpyrifos, chlorpyrifos-methyl, and triclopyr; thus exposure can 

be found directly on food treated with these pesticides. CCCEH studies have largely used 

chlorpyrifos measured in cord blood as the specific biomarker (e.g., Lovasi et al., 2010; Whyatt 

et al., 2004; Rauh et al., 2011). The CHARGE study (Shelton et al., 2015) did not measure 

biomarkers but instead used geospatial analysis to focus on the residential proximity to OP 

exposure using data from the California Department of Pesticide Regulation, with five OPs 

accounting for a total of 73% of the pesticide applied near residential settings (chlorpyrifos, 

acephate, diazinon, bensulide, and dimethoate). 
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Similarly, DAPs can be found directly on food following OP applications (Zhang et al., 2008; 

Chen et al., 2012). Specifically, studies have shown that DAPs may form as environmental 

degradates from abiotic hydrolysis, photolysis, and plant metabolism (Zhang et al., 2008; Chen 

et al., 2012; Racke et al., 1994). Furthermore, since these DAPs are excreted more rapidly and 

extensively than the parent OPs (Zhang et al., 2008; Forsberg et al., 2008), direct exposure to 

DAPs may lead to an overestimate of OP exposure when using urinary DAPs as a biomarker of 

OP exposure. The Agency recognizes that this is a source of uncertainty when using DAPs for 

assessing OP exposure and will continue to monitor this issue in future assessments. 

With respect to neurological effects near birth, the CHAMACOS and Mt. Sinai cohorts measured 

neurological effects at birth, and observed a putative association with total DEAP, total DMAP, 

and total DAP exposure (Engel et al., 2007; Young et al., 2005). Similarly, a Chinese study 

(Zhang et al., 2014) reported statistically significant associations for total DEAPs, total DMAPs, 

and total DAPs from prenatal OP pesticide exposure and neonatal neurodevelopment assessed 3 

days after birth. However, another cross-sectional Chinese study, Guodong et al. (2012), 

observed no association with urinary DAPs and a developmental quotient score for 23-25 month 

old children. 

The 3 US cohorts (CCCEH, Mt. Sinai, CHAMACOS) each reported evidence of impaired mental 

and psychomotor development, albeit not consistent by age at time of testing (ranging from 6 

month to 36 months across the three cohorts). Attentional problems and ADHD were reported 

by three prospective cohorts [Rauh et al., 2006; Eskenazi et al., 2007; Marks et al., 2010; and 

Fortenberry et al. (2014)] investigators with additional support from a case control study, 

Bouchard et al. (2010). The exposure metric varied among these studies. Specifically, 

Fortenberry et al. (2014) found suggestive evidence of an association with TCPy and ADHD in 

boys, whereas statistically significant associations were observed by Rauh et al. (2006) with 

chlorpyrifos exposure and ADHD. Eskenazi et al. (2007) reported associations with total 

DMAPs and total DAPs and ADHD; Marks et al. (2010) reported associations with total DEAP, 

DMAP, and total DAP exposure and ADHD. In a national cross-sectional study of Canadian 

children, using 2007-2009 data for children age 6-11 years (Oulhote and Bouchard, 2013), there 

were no overall statistically significant associations observed between child urinary DEAP, 

DMAP, or total DAP metabolite levels and parentally reported behavioral problems. In contrast, 

Bouchard et al. (2010), looking at U.S. children age 8-15 years in the 2000-2004 National Health 

and Nutrition Examination Survey (NHANES), observed a positive association between 

attention and behavior problems and total DAPs and DMAPs, but not DEAPs. As part of their 

analysis, Oulhote and Bouchard (2013) noted that their outcome assessment for behavioral 

problems may not have been as sensitive as Bouchard et al. (2010), which may in part account 

for the difference in the observed results from these studies. 

In addition, the three US cohorts and the CHARGE study have reported suggestive or positive 

associations between OP exposure and autism spectrum disorders (Rauh et al., 2006; Shelton et 

al., 2014; Eskenazi et al., 2007; Furlong et al., 2014). Specifically, Furlong et al. (2014) 

documented suggestive evidence of an association between total DEAP exposure and reciprocal 

social responsiveness among blacks and boys. Eskenazi et al. (2007) reported a statistically 

significant association between pervasive developmental disorder (PDD) and total DAP 

exposure, whereas Eskenazi et al. (2010) reported non-significant, but suggestive, increased odds 
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of PDD of 2.0 (0.8 to 5.1; p=0.14). Rauh et al. (2006) documented a significant association 

between PDD and specifically chlorpyrifos exposure. Both PDD and reciprocal social 

responsiveness are related to the autism spectrum disorder. Using a different exposure 

assessment method (geospatial analysis and residential proximity to total OP exposure), Shelton 

et al. (2014) also showed statistically significant associations between total OP exposure and 

ASD. While these studies vary in the magnitude of the overall strength of association, they have 

consistently observed a positive association between OP exposure and ASD. Finally, CCCEH, 

Mt. Sinai, CHAMACOS have reported an inverse relation between the respective prenatal 

measures of chlorpyrifos and intelligence measures at age 7 years (Rauh et al., 2011; Engel et al., 

2011; Bouchard et al., 2011). 

Across the epidemiology database of studies, the maternal urine, cord blood, and other 

(meconium) measures provide evidence that exposure did occur to the fetus during gestation but 

the actual level of such exposure during the critical window(s) of susceptibility is not known. 

While significant uncertainties remain about the actual exposure levels experienced by mothers 

and infant participants in the children’s health cohorts, it is unlikely that these exposures resulted 

in AChE inhibition. As part of the CHAMACOS study, Eskenazi et al. (2004) measured AChE 

activity and showed that no differences in AChE activity were observed. The biomarker data 

(chlorpyrifos) from the Columbia University studies are supported by the Agency’s dose 

reconstruction analysis using the PBPK-PD model (D424485, D. Drew et al., 12/29/2014). 

Following the recommendation of the FIFRA SAP (2012), the Agency conducted a dose 

reconstruction analysis of residential uses available prior to 2000 for pregnant women and young 

children inside the home. The PBPK-PD model results indicate for the highest exposure 

considered (i.e., indoor broadcast use of a 1% chlorpyrifos formulation) <1% RBC AChE 

inhibition was produced in pregnant women. While uncertainty exists as to actual OP exposure 

at (unknown) critical windows of exposure, EPA believes it is unlikely individuals in the 

epidemiology studies experienced RBC AChE inhibition. 

A review of the scientific literature on potential modes of action/adverse outcome pathways 

(MOA/AOP)3

 leading to effects on the developing brain was conducted for the 2012 FIFRA SAP 

meeting (USEPA, 2012) and updated for the December 2014 chlorpyrifos revised risk 

assessment (D424485, D. Drew et al., 12/29/2014). In short, multiple biologically plausible 

hypotheses and pathways are being pursued by researchers that include targets other than AChE 

inhibition, including cholinergic and non-cholinergic systems, signaling pathways, proteins, and 

others. However, no one pathway has sufficient data to be considered more credible than the 

others. The fact that there are, however, sparse AOP data to support the in vitro to in vivo

extrapolation, or the extrapolation from biological perturbation to adverse consequence 

significantly limits their quantitative use in risk assessment. The SAP concurred with the 

Agency in 2008 and 2012 about the lack of definable key events in a MOA/AOP leading to 

developmental neurobehavioral effects. However, since the 2014 literature review, there are no 

substantive changes in the ability to define and quantitate steps in an MOA/AOP leading from 

exposure to effects on the developing brain. Published and submitted guideline DNT laboratory 

animal studies have been reviewed for OPs as part of the 2012/2014 review (D424485, D. Drew 

 

3

 Mode of action (MOA) and adverse outcome pathways (AOPs) describe a set of measureable key events that make 

up the biological processes leading to an adverse outcome and the causal linkages between such events. 
Bensulide Human Health Risk Assessment DP No. D428598 

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et al., 12/29/2014) and the updated 2015 review (OPP/USEPA; D331251; 9/15/15). 

Neurobehavioral alterations in laboratory animals were often reported, albeit at AChE inhibiting 

doses, but there was generally a lack of consistency in terms of pattern, timing, or dose-response 

for these effects, and a number of studies were of lower quality. However, this information does 

provide evidence of long-lasting neurodevelopmental disorders in rats and mice following 

gestational exposure. 

At this time, a MOA(s)/AOP(s) has/have not been established for neurodevelopmental outcomes. 

This growing body of literature does demonstrate, however, that OPs are biologically active on a 

number of processes that affect the developing brain. Moreover, there is a large body of in vivo

laboratory studies which show long-term behavioral effects from early life exposure, albeit at 

doses which cause AChE inhibition. EPA considers the results of the toxicological studies 

relevant to the human population, as qualitatively supported by the results of epidemiology 

studies. The Agency acknowledges the lack of established MOA/AOP pathway and uncertainties 

associated with the lack of ability to make strong causal linkages and unknown window(s) of 

susceptibility. These uncertainties do not undermine or reduce the confidence in the findings of 

the epidemiology studies. The epidemiology studies reviewed in the 2012/2014 and 2015 

literature reviews represent different investigators, locations, points in time, exposure assessment 

procedures, and outcome measurements. Despite all these differences in study design, with the 

exception of two negative studies in the 2015 literature review (Guodong et al., 2012; Oulhote 

and Bouchard, 2013), authors have identified associations with neurodevelopmental outcomes 

associated with OP exposure across four cohorts and twelve study citations. Specifically, there is 

evidence of delays in mental development in infants (24-36 months), attention problems and 

autism spectrum disorder in early childhood, and intelligence decrements in school age children 

who were exposed to OPs during gestation. Investigators reported strong measures of statistical 

association across several of these evaluations (odds ratios 2-4 fold increased in some instances), 

and observed evidence of exposures-response trends in some instances, e.g., intelligence 

measures. 

As section 408(b)(2)(C) of the FFDCA instructs EPA, in making its “reasonable certainty of no 

harm” finding, that in “the case of threshold effects, an additional tenfold margin of safety for the 

pesticide chemical residue and other sources of exposure shall be applied for infants and children 

to take into account potential pre- and postnatal toxicity and completeness of data with respect to 

exposure and toxicity to infants and children.” Section 408 (b)(2)(C) further states that “the 

Administrator may use a different margin of safety for the pesticide chemical residue only if, on 

the basis of reliable data, such margin will be safe for infants and children.” Given the totality of 

the evidence, there is sufficient uncertainty in the human dose-response relationship for 

neurodevelopmental effects which prevents the Agency from reducing or removing the statutory 

10X FQPA Safety Factor. For the bensulide DRA, a value of 10X has been applied. Similarly, a 

database uncertainty factor of 10X will be retained for occupational risk assessments. The 

Agency will continue to evaluate the epidemiology studies and pursue approaches for 

quantitative or semi-quantitative comparisons between doses which elicit AChE inhibition and 

those which are associated with neurodevelopmental outcomes prior to a revised human health 

risk assessment. 
Bensulide Human Health Risk Assessment DP No. D428598 

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4.5 Safety Factor for Infants and Children (FQPA SF) 

As noted above, the lack of an established neurodevelopmental MOA/AOP makes quantitative 

use of the epidemiology studies in risk assessment challenging, particularly with respect to 

determining dose-response, critical duration of exposure, and window(s) of susceptibility. 

However, exposure levels in the range measured in the epidemiology studies are likely low 

enough that they are unlikely to result in AChE inhibition. Epidemiology studies consistently 

identified associations with neurodevelopmental outcomes associated with OP exposure such as 

delays in mental development in infants (24-36 months), attention problems and autism spectrum 

disorder in early childhood, and intelligence decrements in school age children. Therefore, there 

is a need to protect children from exposures that may cause these effects; this need prevents the 

Agency from reducing or removing the statutory FQPA Safety Factor. Thus, the FQPA 10X 

Safety Factor will be retained for bensulide for the population subgroups that include 

infants, children, youths, and women of childbearing age for all exposure scenarios. 

A database uncertainty factor of 30x will be applied to inhalation risk assessment only, to 

incorporate the uncertainty in the human dose-response relationship for neurodevelopmental 

effects and for the absence of inhalation data.

4.5.1 Completeness of the Toxicology Database 

The database of toxicology studies for bensulide is complete, except for the requirement of a 

repeat dose inhalation toxicity study. Available bensulide studies include developmental toxicity 

studies in rats and rabbits, a reproductive toxicity study in rats, an acute neurotoxicity study in 

rats, and a CCA study in rats [acute (young adult and PND 11 pups)), repeated dose (young adult 

and PND 11 pups), and gestational (fetus and dam)]. A CCA study for the oxon is not available, 

and exposure to the oxon is considered to be 50X as toxic as exposure to the parent in the 

absence of this data. 

4.5.2 Evidence of Neurotoxicity 

Bensulide is an OP with a neurotoxic AOP; neurotoxicity is the most sensitive effect in all 

species, routes, and lifestages and is being used to derive PODs for risk assessment. Therefore, 

the risk assessment is protective of potential neurotoxicity for every life stage and route of 

exposure. 

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

Sensitivity was not evident in the developmental studies. No developmental toxicity was 

observed in the rat at dose levels resulting in maternal toxicity (tremors and decreased AChE). 

Likewise, no developmental toxicity was observed in the rabbit at dose levels resulting in 

maternal toxicity (decreased body weights and body weight loss). In the rat 2-generation 

reproductive toxicity study, systemic toxicity was noted in offspring (decreased F2 pup survival 

at the high dose), while no systemic toxicity was noted in adults. However, ChEI provides the 

most sensitive endpoint for bensulide, and although ChEI was not measured in pups, ChEI in 

adults in this study (observed at mid and/or high dose) is protective (6.7-fold more sensitive) for 
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the decreased F2 pup survival. The PND 11 pup was generally more sensitive than the adult in 

the acute and repeated dose CCA. The CCA study did not demonstrate the fetus to be more 

sensitive than the dam. Endpoints were chosen to be protective of all lifestages. 

As discussed in Section 4.4, there is uncertainty in the human dose-response relationship for 

neurodevelopmental effects and this warrants retention of the FQPA Safety Factor for the 

population subgroups that include infants, children, youths, and women of childbearing age for 

all exposure scenarios. 

4.5.4 Residual Uncertainty in the Exposure Database 

There are no residual uncertainties with regard to the exposure databases. The acute and steadystate dietary assessment incorporated PDP monitoring data for bensulide and its oxon (when 

available), anticipated residues, default DEEM processing factors, and percent crop treated (CT). 

A TAF of 50x was applied to residues of the oxygen analog in food commodities and drinking 

water, as well as turf transferable residue data used in the residential assessment. Although data 

were used to refine the acute and steady-state dietary exposure assessments, the assessments are 

not expected to underestimate dietary (food and water) exposures. The residential handler and 

post-application exposure assessments are based upon the residential SOPs. The residential 

SOPs are based upon reasonable worst-case assumptions and are not expected to underestimate 

risk. These assessments of exposure are not likely to underestimate the resulting estimates of 

risk from exposure to bensulide.

4.6 Toxicity Endpoint and Point of Departure Selections 

4.6.1 Dose-Response Assessment 

Table 4.6.4.1 summarizes the bensulide toxicity endpoints and PODs selected from an evaluation 

of the database. This endpoint selection was based on a weight of the evidence evaluation using 

the following considerations: 

 Relative sensitivity of the brain and RBC compartments: The RBC AChE was more 

sensitive than the brain AChE to bensulide in every analysis (all studies, durations, 

lifestages, and routes), except the adult males in the acute CCA study. As such, OPP has 

relied upon the RBC data in POD derivation. 

 Potentially susceptible populations (fetuses, juveniles, pregnancy, or sex): The available 

AChE data across multiple lifestages (adults, pregnant adults, fetuses, juveniles) show 

that the PND 11 pups were generally more sensitive than the adult 1.5-4.5 -fold. In the 

gestational CCA, the fetus was not more sensitive than the dam. The pregnant female in 

the gestational CCA is not more sensitive than the non-pregnant female in the repeated 

dose CCA. The adult female was typically more sensitive than the adult male, while the 

pup and fetus did not demonstrate sex-sensitivity. See Appendix A.5. 

 Route of exposure: It is preferred to match, to the degree possible, the route of exposure 

in the toxicity study with that of the exposure scenario(s) of interest. In the case of 

bensulide, BMD modeling data are only available for the oral route. The data from the 

dermal study were not amenable to modeling (no apparent dose response); however, the 
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dermal absorption is low (DAF = 10%). An inhalation study is not available but is 

required. 

 Duration of exposure: It is preferred to match, to the degree possible, the duration of a 

toxicity study with that of the exposure duration of interest. There are single-day and 

steady-state oral studies available. Steady-state dermal studies are available, but no 

inhalation study is available. 

 Consistency across studies: In cases where multiple datasets are available for a single 

duration, it is important to evaluate the extent to which data are consistent (or not) across 

studies. Considering the presence of sensitive populations, that different labs conducted 

the studies across several years, the bensulide database demonstrated consistent ChEI and 

effects. In particular, the study protocol and performance of the CCA enable great 

confidence in the results of this study. 

Descriptions of the primary toxicity studies used for selecting toxicity endpoints and points of 

departure for various exposure scenarios are presented in Appendix 3 of this document. 

Summary tables of BMD analyses can be found in Appendix 2, and the technical details of the 

analysis can be found in the BMD memo (Bever, 2015, TXR # 0057236). 

Consistent with risk assessments for other AChE-inhibiting compounds, OPP has used a 

benchmark response (BMR) level of 10% and has thus calculated BMD10s and BMDL10s (see 

Appendix A.2. for summary of OPP’s ChE policy). The BMD10 is the estimated dose where 

ChE is inhibited by 10% compared to background. The BMDL10 is the lower confidence bound 

on the BMD10. As a matter of science policy, the Agency uses the BMDL, not the BMD, for use 

as the POD (USEPA, 2012). All BMD/BMDL modeling was completed using USEPA BMD 

Software, version 2.4; an exponential model or Hill model was used to fit the data. 

Acute Dietary Endpoint (All Populations) 

A POD for the acute dietary (all populations) exposure scenario was derived from the results of a 

high-quality, well-conducted acute CCA rat study (MRID 49433502). A BMDL10 of 11 mg/kg 

was selected and was associated with RBC ChE inhibition in female pups (PND 11). The 

corresponding BMD10 was 16 mg/kg. RBC cholinesterase inhibition was selected as the 

endpoint for the POD, since BMD10 values were lower than those for brain cholinesterase 

inhibition. Data from the PND 11 pups are appropriate for acute POD derivation, since effects 

were observed after a single exposure and the endpoint is the most sensitive adverse response in 

all populations (infant and children, females 13+, and adults). 

An uncertainty factor of 1000X (10X to account for interspecies extrapolation, 10X for 

intraspecies variation, and 10X for FQPA safety/ database uncertainty factor due to uncertainty 

in the human dose-response relationship for neurodevelopmental effects (see Section 4.4)) is 

applied to the BMDL10 to obtain an aPAD of 0.011 mg/kg/day for exposure scenarios with 

infants, children, youths, and women of childbearing age. The only population subgroup for 

which the FQPA SF is not retained is adults 50-99; therefore, the aPAD for this population 

subgroup is 0.11 mg/kg/day. 
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Steady-State Dietary Endpoint (All Populations) 

A POD for the steady-state dietary (all populations) exposure scenario was derived from the 

repeated-dose response observed in a CCA rat study (MRID 49466201). A BMDL10 of 6 

mg/kg/day was selected and was associated with RBC ChE inhibition in male pups (PND 11 

initially). The corresponding BMD10 was 8 mg/kg/day. RBC cholinesterase inhibition was 

selected as the endpoint for the POD, since BMD10 values were lower than those for brain 

cholinesterase inhibition. Of the best modeled data sets, data from the PND 11 pups provided the 

most sensitive adverse response of all populations (infant and children, females 13+, and adults). 

Discussion of the steady-state POD is provided in Section 4.3.1. The modeling of the CCA study 

allowed for a much greater confidence in the accuracy of the resulting estimated BMDL10. 

Overall, the CCA study provided the best source of data to establish the steady-state value due to 

more optimal selection of doses, the number of dose groups (6), sampling at the time of peak 

effect from a gavage study, several lifestages (adult, PND 11 pups, pregnant dams, fetuses), 

acute and repeat exposure periods, and the quality of BMD modeling lending confidence to the 

results. Furthermore, the CCA study allowed the evaluation of the most sensitive life stage 

(PND 11 pups). The combination of best fit modeling and most protective value occurred for 

ChE inhibition in the PND 11 male RBC following 10 daily doses (6 mg/kg/day, repeated dose 

CCA study). The BMD10 of 8 mg/kg/day from this study fits within the range of that observed at 

longer durations in the chronic toxicity/ carcinogenicity study. 

The endpoint and POD are protective of all other effects observed in the database. An 

uncertainty factor of 1000X (10X to account for interspecies extrapolation, 10X for intraspecies 

variation, and 10X for FQPA safety/ database uncertainty factor due to uncertainty in the human 

dose-response relationship for neurodevelopmental effects (see Section 4.4)) is applied to the 

BMDL10 to obtain a ssPAD of 0.006 mg/kg/day for all exposure scenarios, except adults 50-99. 

Excluding the FQPA SF for adults 50-99, the ssPAD is 0.06 mg/kg/day. 

Incidental Oral Endpoint/ Steady-State 

A POD of 6 mg/kg/day was selected from the repeat dose CCA study in rats, based on the same 

rationale provided above for the steady-state dietary exposures. A total uncertainty factor of 

1000X is appropriate for incidental oral exposures (10X for interspecies extrapolation, 10X for 

intraspecies variation, and 10X for FQPA SF due to uncertainty in the human dose-response 

relationship for neurodevelopmental effects (see Section 4.4)) allowing a Level of Concern 

(LOC) of 1000X. 

Dermal Endpoints/ Steady-State 

A POD of 6 mg/kg/day was selected from the repeat dose CCA study in rats, based on the same 

rationale provided above for the steady-state dietary exposures. The POD was adjusted based on 

a 10% dermal absorption factor to 60 mg/kg/day. A total uncertainty factor of 1000X is 

appropriate for dermal exposures (10X for interspecies extrapolation, 10X for intraspecies 

variation, and a 10X FQPA SF for residential assessments or a database uncertainty factor in 

occupational assessments due to uncertainty in the human dose-response relationship for 

neurodevelopmental effects (see Section 4.4)), allowing a LOC of 1000X. 

The ChEI data from the dermal toxicity study would not model due to a lack in dose response. 

The dermal toxicity study NOAEL from MRIDs 44801101 and 44809401 is 50 mg/kg/day, 
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which approximates the selected POD of 6 mg/kg/day with the DAF of 10% (i.e. 60 mg/kg/day 

adjusted dose). The LOAEL was 500 mg/kg/day based on brain ChEI. Due to dose spread issues 

related to the NOAEL approach and the quality of the BMD analysis from the CCA study, the 

CCA study is a more appropriate selection than the dermal study. Since plasma and brain ChEI 

was observed at 500 mg/kg/day, it would be expected that RBC inhibition be observed as well. 

Therefore, instead of relying on brain ChEI for only the dermal route of exposure, the RBC 

AChE data from the CCA study can be aggregated with the dermal and inhalation routes. 

Inhalation Endpoints/ Steady-State 

A POD of 6 mg/kg/day was selected from the repeat oral dose CCA study in rats, based on the 

same rationale provided above for the steady-state dietary exposures. A route-specific inhalation 

study is unavailable. Toxicity through the inhalation route is considered to be similar to that of 

the oral route. The total uncertainty factor of 3000X was applied (10X for interspecies 

extrapolation, 10X for intraspecies variation, and 30X database uncertainty factor incorporating 

uncertainty in the human dose-response relationship for neurodevelopmental effects (see Section 

4.4) and because there is an unfulfilled inhalation study requirement for bensulide), resulting in a 

LOC of 3000X. 

4.6.2 Oxon Toxicity Adjustment Factor 

In the 2006 updated OP cumulative risk assessment (CRA), the Agency characterized the 

potential impacts of the conversion of OP pesticides to oxon transformation products during 

standard drinking water treatment processes. For those OP pesticides that could potentially 

transform into more toxic oxons, the Agency assumed a complete transformation as a result of 

drinking water treatment. Based on limited data (documented in the 2002 OP CRA), the Agency 

assumed that the oxons would persist for a sufficient time to travel through the distribution 

system. 

 

The Agency used submitted data to characterize the relative toxicity differences between the 

oxon and the parent for some of the OP pesticides; information from published literaturewas also 

available to inform relative potency for a few OP Pesticides4

. For those OP pesticides without 

sufficient oxon data, the Agency initially used upper bound oxon adjustment factors of 10X and 

100X for estimating potential oxon potency. The 100X was used considering the highest relative 

toxicity difference observed (61X) for malathion/malaoxon, based on the data available at the 

time. However, since then, acute and repeat dose CCA studies have been submitted for both 

malathion and malaoxon. The new data allow a direct comparison of relative toxicity for the two 

chemicals and therefore, reduces uncertainty; an oxon adjustment factor of 22X was determined 

based on these data. As a result, a 50X oxon adjustment factor has been used for the OP draft 

risk assessments for registration review to estimate potential oxon potency. The 50X accounts 

for the highest oxon adjustment factor of 22X with an additional safety margin to protect for 

potential oxon toxicity for chemicals without oxon data. The adjustment factors were applied to 

residues for risk assessment of all exposure durations, routes, and scenarios. 

 

4

 Chambers JE, Carr RL. 1993. “Inhibition patterns of brain acetylcholinesterase and hepatic and plasma aliesterases 

following exposures to three phosphorothionate insecticides and their oxons in rats.” Fundamental and Applied 

Toxicology. Jul;21(1):111_9. 
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OP PESTICIDE OXON ADJUSTMENT FACTOR

Azinphos-Methyl No data 

Bensulide No data 

Chlorethoxyfos No data 

Chlorypyrifos 11.9X (acute); 18X (repeated): RBC 

Coumaphos No data 

Diazinon 12.1X (acute); 9.0X (repeated):RBC 

Dimethoate 8 X (acute); 3X (repeated): Brain 

Disulfoton No data 

Malathion 22X (acute); 22X (repeated): RBC 

Methidathion No data 

Methyl Parathion <10X (Chambers and Carr, 1993)*

Phostebuprim No data 

Propetamphos No data 

Temephos No data 

Oxon toxicity adjustment factors are based on a comparison of the most sensitive compartment (i.e., RBC or brain) determined 

for the chemical. 

4.6.3 Recommendation for Combining Routes of Exposures for Risk Assessment 

When there are potential occupational and residential exposures to a pesticide, the risk 

assessment must address exposures from three major sources (oral, dermal, and inhalation) and 

determine whether the individual exposures can be combined if they have the same toxicological 

effects. PODs for the incidental oral, dermal, and inhalation routes are all derived from RBC 

AChE inhibition. As a result, exposure from all routes can be combined. 

4.6.4 Cancer Classification and Risk Assessment Recommendation 

Bensulide is classified as a “Group E Chemical – evidence of non-carcinogenicity for humans” 

based on lack of evidence for carcinogenicity in rats and mice. There is no mutagenicity concern 

for bensulide. 

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

Assessment 

Table 4.6.5.1 Summary of Toxicological Doses and Endpoints and Points of Departure for Bensulide in 

Dietary and Non-Occupational Human Health Risk Assessments a 

Exposure 

Scenario

Point of 

Departure 

(mg/kg/day) 

Uncertainty/FQPA 

Factors 

RFD, PAD, & LOC 

for Risk Assessment Study and Toxicological 

Effects 

Acute Dietary 

 

(All 

Populations 

Except Adults 

50-99 Years) 

BMDL10 = 11 

mg/kg 

UFA = 10x 

UFH = 10x 

FQPA SF = 10x 

Acute RfD = 0.11 

mg/kg 

aPAD = 

 0.011 mg/kg 

Acute CCA Study (MRID 

49433502) in the rat 

BMD10 = 16 mg/kg 

Inhibition of RBC ChE in 

female pups (PND 11) 

Acute Dietary 

 

(Adults 50-99 

Years) 

BMDL10 = 11 

mg/kg 

UFA = 10x 

UFH = 10x 

FQPA SF = 1x 

Acute RfD = aPAD = 

 0.11 mg/kg 

Acute CCA Study (MRID 

49433502) in the rat 

BMD10 = 16 mg/kg 

Inhibition of RBC ChE in 

female pups (PND 11) 

Steady-State 

Dietary 

(All 

Populations 

Except Adults 

50-99 Years) 

BMDL10 = 6 

mg/kg/day 

UFA = 10x 

UFH = 10x 

FQPA SF = 10x 

ssRfD = 0.06 

mg/kg/day 

ssPAD = 0.006 

mg/kg/day 

Repeated-Dose CCA Study 

(MRID 49466201) in the rat 

BMD10 = 8 mg/kg/day 

Inhibition of RBC ChE in male 

pups (PND 11 initially) 

Steady-State 

Dietary 

(Adults 50-99 

Years) 

BMDL10 = 6 

mg/kg/day 

UFA = 10x 

UFH = 10x 

FQPA SF = 1x 

ssRfD = ssPAD = 

0.06 mg/kg/day 

Repeated-Dose CCA Study 

(MRID 49466201) in the rat 

BMD10 = 8 mg/kg/day 

Inhibition of RBC ChE in male 

pups (PND 11 initially) 

Incidental 

Oral 

Steady-State 

BMDL10 = 6 

mg/kg/day 

UFA = 10x 

UFH = 10x 

FQPA SF = 10x 

Residential LOC for 

MOE = 1000x 

Repeated-Dose CCA Study 

(MRID 49466201) in the rat 

BMD10 = 8 mg/kg/day 

Inhibition of RBC ChE in male 

pups (PND 11 initially) 

Dermal 

Steady-State 

BMDL10 = 6 

mg/kg/day 

UFA = 10x 

UFH = 10x 

FQPA SF = 10x 

DAF = 10% 

Residential LOC for 

MOE = 1000x 

Repeated-Dose CCA Study 

(MRID 49466201) in the rat 

BMD10 = 8 mg/kg/day 

Inhibition of RBC ChE in male 

pups (PND 11 initially) 
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Table 4.6.5.1 Summary of Toxicological Doses and Endpoints and Points of Departure for Bensulide in 

Dietary and Non-Occupational Human Health Risk Assessments a 

Exposure 

Scenario

Point of 

Departure 

(mg/kg/day) 

Uncertainty/FQPA 

Factors 

RFD, PAD, & LOC 

for Risk Assessment Study and Toxicological 

Effects 

Inhalation 

Steady-State 

BMDL10 = 6 

mg/kg/day 

UFA = 10x 

UFH = 10x 

FQPA SF = 30x b 

Residential LOC for 

MOE = 3000x 

Repeated-Dose CCA Study 

(MRID 49466201) in the rat 

BMD10 = 8 mg/kg/day 

Inhibition of RBC ChE in male 

pups (PND 11 initially) 

Cancer (oral, 

dermal, 

inhalation) 

Classification: Group E chemical; Evidence of Non-Carcinogenicity in Humans 

 

a 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. BMDL = lower limit of the bench mark dose. 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). SF = Safety Factor. PAD = population adjusted dose (a = acute, ss = steady-state or maximal acetyl 

cholinesterase inhibition which occurs around 2-3 weeks for most OPs and is a specific exposure assessment 

conducted for OPs, instead of the traditional short, intermediate, or chronic assessments. The SS assessment is 

protective of longer durations of exposure, including chronic). RfD = reference dose. MOE = margin of exposure. 

LOC = level of concern. FQPA = Food Quality Protection Act 

b This uncertainty factor incorporates uncertainty in the human dose-response relationship for neurodevelop-mental 

effects (see Section 4.4) and because there is an unfulfilled inhalation study requirement for bensulide 

Table 4.6.5.2 Summary of Toxicological Doses and Endpoints for Bensulide for Use in Occupational Human 

Health Risk Assessments a 

Exposure/ 

Scenario 

Point of 

Departure 

Uncertainty/

FQPA 

Factors 

LOC for Risk 

Assessment Study and Toxicological Effects 

Dermal 

Steady-State 

BMDL10 = 6 

mg/kg/day 

UFA = 10x 

UFH = 10x 

UFDB = 10x 

DAF = 10% 

Occupational 

LOC for MOE = 

1000x 

Repeated-Dose CCA Study (MRID 

49466201) in the rat 

BMD10 = 8 mg/kg/day 

Inhibition of RBC ChE in male pups (PND 

11 initially) 

Inhalation 

Steady-State 

BMDL10 = 6 

mg/kg/day 

UFA = 10x 

UFH = 10x 

UFDB = 30x 

Occupational 

LOC for MOE = 

3000x 

Repeated-Dose CCA Study (MRID 

49466201) in the rat 

BMD10 = 8 mg/kg/day 

Inhibition of RBC ChE in male pups (PND 

11 initially) 

Cancer (oral, 

dermal, 

inhalation) 

Classification: Group E chemical – Evidence of Non-Carcinogenicity in Humans 
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a 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. BMDL 

= lower limit of the bench mark dose. 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). LOC = level of concern. UFDB = database uncertainty factor b This uncertainty factor incorporates uncertainty in the human dose-response relationship for neurodevelop-mental effects (see 

Section 4.4) and because there is an unfulfilled inhalation study requirement for bensulide 

Steady-State = steady-state or maximal AChE inhibition which occurs around 2-3 weeks for most OPs and is a specific exposure 

assessment conducted for OPs instead of the traditional short, intermediate, or chronic assessments. The steady-state assessment 

is protective of longer durations including chronic. 

4.7 Endocrine Disruption 

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic, and 

chronic durations and assess carcinogenicity, neurotoxicity, developmental, reproductive, and 

general or systemic toxicity. These studies include endpoints which may be susceptible to 

endocrine influence, including effects on endocrine target organ histopathology, organ weights, 

estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, and sex ratios in 

offspring. For ecological hazard assessments, EPA evaluates acute tests and chronic studies that 

assess growth, developmental, and reproductive effects in different taxonomic groups. As part of 

its reregistration decision for bensulide, EPA reviewed these data and selected the most sensitive 

endpoints for relevant risk assessment scenarios from the existing hazard database. However, as 

required by FFDCA section 408(p), bensulide is subject to the endocrine screening part of the 

Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP, where 

EPA will determine which, if any, of the Tier 2 tests are necessary based on the available data. 

Tier 2 testing is designed to identify any adverse endocrine-related effects caused by the 

substance and establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list 

of chemicals identified for EDSP screening was published on June 14, 2013i

and includes some 

pesticides scheduled for registration review and chemicals found in water. Neither of these lists 

should be construed as a list of known or likely endocrine disruptors. 

 

i

 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals. 
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Bensulide is on List 2. List 2 represents the next set of chemicals for which EPA intends to issue 

test orders/data call-ins in the near future. For further information on the status of the 

EDSP, the policies and procedures, the lists of chemicals, future lists, the test guidelines and the 

Tier 1 screening battery, please visit our website.ii 

5.0 Dietary Exposure and Risk Assessment 

5.1 Residues of Concern Summary and Rationale 

The nature of the residues in plants is adequately established based on carrot, lettuce and tomato 

metabolism studies. The residues of concern for risk assessment in plants and drinking water, 

and tolerance enforcement in plants consists of bensulide and its oxon (C. Eiden, D238417, 

10/06/1997). Appendix E summarizes the metabolism data for parent bensulide and its oxygen 

analog. 

Table 5.1. Summary of Metabolites and Degradates to be included in the Risk Assessment and 

Tolerance Expression

Matrix Residues included in Risk 

Assessment 

Residues included in 

Tolerance Expression 

Plants Primary Crop Bensulide and its oxon Bensulide and its oxon 

Rotational Crop NS1 NS1

Livestock Ruminant NR1 NR1

Poultry 

Drinking Water Bensulide and its oxon Not Applicable 

1 NS = Not specified. It was indicated that the nature of the residue seems to be similar to that on primary crops (C. 

Eiden, D218575, 04/02/1997). Following the 120-day plant-back interval (PBI), residues in rotational crops do not 

need to be considered for risk assessment and tolerance enforcement. 2

 NR = Not required to support the established uses of bensulide. Livestock metabolism studies may be required if 

new uses are sought.

5.2 Food Residue Profile 

The nature of the residues in plants is adequately established based on carrot, lettuce and tomato 

metabolism studies. Tolerances are established in the 40 CFR § 180.241 for the use of bensulide 

on bulb onion, leafy vegetable except brassica (CG 4), leafy brassica vegetables (CG 5), fruiting 

vegetable (CG 8), and cucurbit vegetables (CG 9), and a regional registration for use on carrots. 

Uses on garlic and shallots are in the label as well which is covered by the tolerance for bulb 

onion, refer to the 40 CFR § 180.1. The established tolerances are based on measurement of 

bensulide and its oxygen analog and range from 0.10 to 0.15 ppm. The 0.10 ppm tolerances are 

based on combined levels of bensulide and its oxon at the LOQ of 0.05 ppm. However, in order 

to account for potential residue losses during storage prior to analysis, the tolerance for bensulide 

residues on brassica vegetables (CG 5), cucurbit vegetables (CG 9) and leafy vegetables (CG 4) 

 

ii http://www.epa.gov/endo/
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is 0.15 ppm (based on twice the limit of quantitation for bensulide per se (0.10 ppm) plus the 

limit of quantification for bensulide oxon (0.05 ppm)). 

 

Metabolism studies conducted with lettuce, carrot and tomato show that parent bensulide was at 

quantifiable levels only in carrot, while the oxygen analog was quantified in lettuce and carrot, 

refer to Appendix E. Levels of the oxon were higher than those of parent bensulide only in 

lettuce, which suggest that the oxon may predominate. Moreover, PDP data for lettuce (years 

2010 and 2011) show that bensulide was detected in 6 of 1487 samples whereas bensulide oxon 

was detected in 49 of those 1487 samples. Generally, the concentration of the oxon in/on lettuce 

is higher than that of parent bensulide. PDP data for carrots do not show quantifiable residues of 

bensulide or its oxon while data for tomato do not show residues of bensulide’s oxon. 

As part of registration review, the residue chemistry database for bensulide was evaluated. The 

only data deficiency identified in the registration eligibility decision (C. Eiden, D238417, 

10/06/1997) that has not been satisfied is additional crop field trials for bensulide on non-bell 

peppers (domestic use) and tomato (import use). Although these data are not available, the 

dietary risk is not underestimated since the assessment incorporates anticipated residues for nonbell peppers and tomato. 

5.3 Water Residue Profile 

The drinking water residues used in the dietary risk assessment were provided by the 

Environmental Fate and Effects Division (EFED) in the following memorandum: “Bensulide: 

Drinking Water Exposure Assessment for Registration Review” (D428601, He Zhong, 

09/14/2015) and incorporated directly into this dietary assessment. Water residues were 

incorporated in the DEEM-FCID into the food categories “water, direct, all sources” and “water, 

indirect, all sources.” 

Drinking water from surface water sources may be subjected to water treatment through 

chlorination. Kamel et al. (2009) demonstrated that the parent bensulide residues may be totally 

converted into bensulide oxon during chlorination processes. Therefore, a total toxic residue 

(TTR) approach based on the oxon equivalent was used for drinking water from surface water 

sources. The recommended estimated drinking water concentrations (EDWCs) of the TTRs from 

surface water sources were generated with the Surface Water Concentration Calculator (SWCC) 

model from the use scenario of the maximum exposure, California lettuce, with three ground 

spray applications at 6 lb ai/A each and a minimum 4-month interval (Table 5.3.1). 

Drinking water from groundwater sources is seldom subjected to chlorination; thus, conversion 

of bensulide to its oxon was only based on aerobic soil metabolism processes (13.8%). 

Therefore, recommended oxon EDWCs from groundwater sources were modeled with PRZMGW based on the oxon soil conversion rate at 2.12 lbs ai per acre following the use scenario on 

loamy sand soil in NC eastern coastal plain with two single bensulide maximum granular 

applications at 16 lb ai per acre each at 4-month intervals (Table 5.3.1). Note that the EDWCs for 

groundwater were also obtained by modeling bensulide at the maximum application rate; 

however, the EDWCs recommended by EFED are based on the oxon since these were higher 

than those for parent bensulide. Based on modeling, the highest residues were obtained for 
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groundwater. In addition, the scenario that provided the lowest EDWC (California Avocado; 3 

applications at 6 lbs ai/A) was modeled to provide the lowest estimate of the exposure and risk 

for food and drinking water, see Table 5.3.2. 

Table 5.3.1. Recommended Surface water and Groundwater EDWCs (μg/L) for Bensulide Oxon 

Surface Water Model: Tier II SWCC (v 1.106) 

1 in 10 yr 

Peak 

1 in 10 yr 

Annual Average 

30 yr Annual 

Average 

Ground Spray - CA Lettuce scenario (W23273.dvf) 

 (6 lbs ai/acre for 3 applications (2/1, 6/1, 10/1) 

979 494 305 

Groundwater Model: Tier 1 PRZM-GW 

Peak 

Values

Post Breakthrough 

Average

Breakthrough 

Time (Days)

NC Eastern Coastal Plain - (w13722Extended.dvf) 

2.12 lbs ai/acre for 2 applications (3/1 and 7/1) 

1,250 1,200 7,106 

Table 5.3.2. Surface Water EDWCs for Bensulide TTRs

Scenario Concentration (μg/L) 

1 in 10 yr 

Peak 

1 in 10 yr 

Annual Average 

30 year Annual 

Average 

CA Avocado 

(W23188.dvf) 

179 100 73 

For the acute and steady-state assessments, the entire 30-year distribution of estimated daily 

concentrations in groundwater was incorporated into DEEM-FCID and used in the probabilistic 

analyses. For steady-state, the daily time series were recalculated using the 21-day rolling 

averages. In the 21-day rolling average distributions, the first data point is the average of days 1-

21, the second data point is the average of days 2-22, the third data point is the average of days 

3-23, etc. The estimated daily concentrations were adjusted by a 50x toxicity adjustment factor 

to account for the relative toxicity of bensulide oxon with respect to parent bensulide, refer to 

section 5.4.1. 

5.4 Dietary Risk Assessment 

5.4.1 Description of Residue Data Used in Dietary Assessment 

Relative Toxicity of the Oxon 

In order to account for the relative toxicity of bensulide oxon with respect to parent bensulide, a 

CCA study is needed. However, EPA plans to move forward with bensulide human health risk 

assessment without toxicity data for bensulide’s oxon degradate. In lieu of bensulide-specific 

oxon CCA data, EPA will use an oxon toxicity adjustment factor of 50x in its calculations. This 

value considers the data derived toxicity adjustment factor EPA has identified among oxon 

metabolites for other organophosphates, with an additional margin of safety included due to the 

uncertainty in extrapolating oxon potency data across chemicals. 

Anticipated Residues 
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USDA Pesticide Data Program (PDP) monitoring data were incorporated in the dietary 

assessment. In years 2010 to 2013, USDA PDP analyzed several commodities for residues 

bensulide and its oxon separately. PDP monitoring data are available for residues of bensulide 

and its oxon in carrots, carrots baby food, summer squash, cherry tomatoes, and lettuce. PDP 

monitoring data are only available for parent bensulide for celery, winter squash, hot peppers, 

onion, canned spinach and frozen spinach. When the oxon analog was not measured, 

concentration adjustment factors of 1x were used; however, for leafy vegetables a factor of 9x 

was used since data suggest that residues of the oxon are likely to be higher than those of 

bensulide (see Appendix E). These factors were used in addition to the previously mentioned 

50x toxicity adjustment factor. When the commodity was not analyzed by the USDA PDP or 

translations were not possible, tolerance level residues were used. Anticipated residues using 

tolerances are based on the LOQ or 2 times the LOQ (data adjusted due to loss of parent 

bensulide during storage) of the data acquisition method. 

5.4.2 Percent Crop Treated Used in Dietary Assessment 

The following maximum percent crop treated estimates (Updated Screening Level Usage 

Analysis Report for Bensulide, PC Code 009801; 07/10/2015) were used in the acute and steadystate dietary risk assessment for the following crops that are currently registered for bensulide: 

broccoli: 25%; Brussels sprouts: 5%; cabbage: 20%; cantaloupes: 40%; cauliflower: 20%; 

celery: 5%; cucumbers: 5%; honeydews: 30%; lettuce: 40%; onions: 20%; peppers: 10%; 

pumpkins: 10%; spinach: 10%; squash: 15%; and watermelons: 10%. Percent of crop treated 

estimates were not provided for carrot, tomato, eggplant, okra and several non-representative 

crops under the cucurbit, leafy and brassica vegetables; 100% of crop treated were assumed for 

these crops. 

5.4.3 Acute Dietary Risk Assessment 

The acute dietary exposure estimates from food alone are below HED’s level of concern (LOC) 

at the 99.9th percentile of exposure for the general population and all population subgroups. The 

highest exposed population subgroup was children 3-5 years old with an exposure of 0.005016 

mg/kg/day occupying 46% of the aPAD. Exposures are above the LOC for drinking water only. 

For food and drinking water, using the drinking water scenario that provided the highest EDWC 

(NC Cotton), the dietary exposure estimates were >10,000 of the aPAD at the 95th, 99th and 

99.9th percentile of exposure for most population subgroups with All Infants (< 1 year old) 

having the highest exposure (Table 5.4.6). In addition, using the drinking water scenario 

(California Avocado) that provided the lowest EDWC, the dietary exposure estimates were 

>1600% of the aPAD at the 99.9th percentile of exposure for the general population and most 

population subgroups. For Adults 50-99 years old, for which the FQPA SF is 1x, exposures were 

above the LOC for food and drinking water (NC Cotton and CA Avocado) as well. In summary, 

acute aggregate (food and drinking water) dietary exposure estimates are above HED’s level of 

concern. 
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5.4.4 Steady-state Dietary Risk Assessment 

The steady-state dietary exposure estimates from food alone are below HED’s LOC at the 99.9th

percentile of exposure for the general population and all population subgroups. The highest 

exposed population subgroup was children 3-5 years old with an exposure of 0.004779 

mg/kg/day occupying 80% of the ssPAD. Exposures are above the LOC for drinking water only. 

For food and drinking water, using the scenario that provided the highest EDWC, dietary 

exposure estimates were >10,000 of the ssPAD at the 95th, 99th and 99.9th percentile of exposure 

for population subgroups with All Infants (< 1 year old) having the highest exposure (Table 

5.4.6). In addition, using the drinking water scenario (California Avocado) that provided the 

lowest EDWC, the dietary exposure estimates were >2900% of the ssPAD at the 99.9th percentile 

of exposure for the general population and all population subgroups.For Adults 50-99 years old, 

for which the FQPA SF is 1x, exposures were above the LOC for food and drinking water (NC 

Cotton and CA Avocado) as well. In summary, steady-state aggregate (food and drinking water) 

dietary exposure estimates are above HED’s level of concern. 

5.4.5 Cancer Dietary Risk Assessment 

Bensulide has been classified as not likely to be carcinogenic in humans via relevant routes of 

exposure; therefore, a cancer dietary assessment is not needed. 

5.4.6 Summary Tables 

Table 5.4.6.1. Summary of Acute Dietary (Food Only, and Food and Drinking Water) Exposure and Risk for 

Bensulide and for Bensulide Oxon (Expressed as Bensulide Equivalents) at the 99.9th Percentile.* 

Population Subgroup 

Food Only Food and 

Water (NC Cotton) 

Food and 

Water (CA Avocado) 

Dietary 

Exposure 

(mg/kg/day) 

% aPAD 

Dietary 

Exposure 

(mg/kg/day) 

% aPAD 

Dietary 

Exposure 

(mg/kg/day) 

% aPAD 

General U.S. Population 0.003459 31 7.200738 >10000 0.259261 2400 

All Infants (<1 year old) 0.003299 30 15.584203 >10000 0.617566 5600 

Children 1-2 years old 0.004436 40 10.366006 >10000 0.381599 3500 

Children 3-5 years old 0.005016 46 6.774460 >10000 0.274069 2500 

Children 6-12 years old 0.003835 35 6.321278 >10000 0.214996 2300 

Youth 13-19 years old 0.002713 25 4.816789 >10000 0.180075 2000 

Adults 20-49 years old 0.002241 20 5.199845 >10000 0.205208 1600 

Adults 50-99 years old 0.002124 1.9 4.856943 4400 0.187992 170 

Females 13-49 years old 0.002685 24 5.059084 >10000 0.202361 1800 

* The subpopulation with the highest risk estimate is bolded. 
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Table 5.4.6.2. Summary of Steady-state Dietary (Food Only, and Food and Drinking Water) Exposure and Risk 

for Bensulide and for Bensulide Oxon (Expressed as Bensulide Equivalents) at the 99.9th Percentile. *

Population Subgroup 

Food Only Food and 

Water (NC Cotton) 

Food and 

Water (CA Avocado) 

Dietary 

Exposure 

(mg/kg/day) 

% ssPAD 

Dietary 

Exposure 

(mg/kg/day) 

% ssPAD 

Dietary 

Exposure 

(mg/kg/day) 

% ssPAD 

General U.S. Population 0.003454 58 7.197920 >10000 0.256468 4300 

All Infants (<1 year old) 0.003322 55 15.581721 >10000 0.603403 >10000 

Children 1-2 years old 0.004436 74 10.393019 >10000 0.378531 6300 

Children 3-5 years old 0.004779 80 6.795017 >10000 0.267948 4500 

Children 6-12 years old 0.003836 64 6.315285 >10000 0.212895 3500 

Youth 13-19 years old 0.002710 45 4.781498 >10000 0.176266 2900 

Adults 20-49 years old 0.002240 37 5.194808 >10000 0.200449 3300 

Adults 50-99 years old 0.002121 3.6 4.851935 8100 0.182459 300 

Females 13-49 years old 0.002687 45 5.053817 >10000 0.196688 3300 

* The subpopulation with the highest risk estimate is bolded. 

6.0 Residential (Non-Occupational) Exposure/Risk Characterization

6.1 Residential Handler Exposure 

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

application process. HED believes that there are distinct tasks related to applications and that 

exposures can vary depending on the specifics of each task. Residential handlers are addressed 

somewhat differently by HED as homeowners are assumed to complete all elements of an 

application without use of any protective equipment. 

 

The quantitative exposure/risk assessment developed for residential handlers is based on the 

following scenarios: 

 Mixing/loading/applying liquid and granular formulations dispersed by hand to 

residential turf/lawns, and 

 Mixing/loading/applying liquid and granular formulations with handheld equipment to 

residential turf/lawns. 

Residential Handler Exposure Data and Assumptions 

A series of assumptions and exposure factors served as the basis for completing the residential 

handler risk assessments. Each assumption and factor is detailed below. 

Application Rate: 

Application rates are listed in Table 3.3. 

Unit Exposures and Area Treated or Amount Handled:
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Unit exposure values and estimates for area treated or amount handled were taken from HED’s 

2012 Residential SOPs5

. 

Exposure Duration: 

Residential handler exposure is assessed as steady-state in duration.

Body Weight: 

For adults, when an endpoint is not sex-specific (i.e., the endpoints are based on developmental 

or fetal effects) a body weight of 80 kg is typically used in risk assessment; however, in this case, 

a female-specific body weight of 69 kg was used. While the endpoint of concern, RBC AChE 

inhibition, is not sex-specific, the female-specific body weight was used to protect for pregnant 

women due to uncertainty in the human dose-response relationship for neurodevelopmental 

effects (See Section 4.4). 

Residential Handler Non-Cancer Exposure and Risk Estimate Equations 

The algorithms used to estimate exposure and dose for residential handlers can be found in the 

2012 Residential SOPs6. 

Combining Exposures/Risk Estimates: 

A total aggregated risk index (ARI) was used since the LOCs for dermal exposure (1000) and 

inhalation exposure (3000) are different. The target ARI is 1; therefore, ARIs of less than 1 are 

risk estimates of concern. The aggregate risk index (ARI) was calculated as follows. 

Aggregate Risk Index (ARI) = 1÷ [(Dermal LOC ÷ Dermal MOE)+ (Inhalation LOC ÷ Inhalation MOE)] 

Summary of Residential Handler Non-Cancer Exposure and Risk Estimates 

A summary of residential handler risk estimates is provided in Table 6.1.1 below. Most 

residential handler risk estimates are of concern (ARI < 1). 

 

5

 Available: http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/standard-operating-proceduresresidential-pesticide 6

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Table 6.1.1. Residential Handler Non-cancer Exposure and Risk Estimates for Bensulide. 

Exposure Scenario Level of Concern Dermal Unit Exposure (mg/lb ai) Inhalation Unit Exposure (mg/lb ai) Maximum Application Rate1 Area Treated or Amount Handled Daily2 Dermal Inh

Dose (mg/kg/day)3 MOE4 Dose (mg/kg/day)5 

Mixer/Loader/Applicator 

Liquid Concentrate, 

Handwand, Lawns 

1000 for 

dermal 

 3000 for 

inhalation 

63 0.018 0.16 lb ai/gal 5 gallons 0.073 82 0.0002 

Ready-to-use, hose end 

sprayer, Lawns 6.26 0.034 8.7 lb ai/acre 0.5 acres 0.039 150 0.0021 

Liquid, Backpack, 

Lawns 130 0.14 0.16 lb ai/gal 5 gallons 0.15 40 0.0016 

Granule, Push type 

rotary spreader, Lawns 0.81 0.0026 12.5 lb ai/acre 0.5 acres 0.0073 820 0.0002 

Granule, belly grinder, 

lawns 360 0.039 

0.00029 lb ai/ft2

1200 ft2 0.18 33 0.0002 

Granule, Spoon, Lawns 6.2 0.087 

100 ft2

0.00026 23,000 0.000037 

Granule, Cup, Lawns 0.11 0.013 0.0000046 1,300,000 0.0000055 

Granule, Hand 

dispersal, Lawns 160 0.38 0.0067 890 0.00016 

Granule, Shaker can, 

Lawns 0.11 0.013 0.0000046 1,300,000 0.0000055 

1 Based on registered labels (see Table 3.3). 2 Based on HED’s 2012 Residential SOPs (http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/standard-operating-procedures-resid3 Dermal Dose = Dermal Unit Exposure (mg/lb ai) × Application Rate (lb ai/acre, ft2 or gal) × Area Treated or Amount Handled (A or ft2/day or gallo

Absorption Factor (10%) ÷ Body Weight (69 kg). 

4 Dermal MOE = Dermal NOAEL (6 mg/kg/day) ÷ Dermal Dose (mg/kg/day). 

5 Inhalation Dose = Inhalation Unit Exposure (mg/lb ai) × Application Rate (lb ai/acre, ft2 or gal) × Area Treated or Amount Handled (A or ft2/day or 

(69 kg). 

6 Inhalation MOE = Inhalation NOAEL (6 mg/kg/day) ÷ Inhalation Dose (mg/kg/day). 7 ARI = Aggregate Risk Index = 1÷ [(Dermal LOC ÷ Dermal MOE) + (Inhalation LOC ÷ Inhalation MOE)]
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6.2 Residential Post-Application Exposure 

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

an environment that has been previously treated with bensulide. The quantitative exposure/risk 

assessment for residential post-application exposures is based on the following scenarios: 

 Dermal exposure from high contact with treated turf (adults and children 1 to < 2 years 

old), 

 Dermal exposure from golfing (adults and youth 11 to < 16 years old and youth 6 to < 11 

years old), 

 Dermal exposure from mowing treated turf (adults and youth 11 to < 16 years old), 

 Incidental ingestion (i.e., hand-to-mouth, object-to-mouth, soil ingestion exposure) from 

contact with treated turf (children 1 to < 2 years old), and 

 Episodic granular ingestion (children 1 to < 2 years old). 

The lifestages selected for each post-application scenario are based on an analysis provided as an 

Appendix in the 2012 Residential SOPs7

. While not the only lifestage potentially exposed for 

these post-application scenarios, the lifestage that is included in the quantitative assessment is 

health protective for the exposures and risk estimates for any other potentially exposed lifestage. 

Residential Post-application Exposure Data and Assumptions 

A series of assumptions and exposure factors served as the basis for completing the residential 

post-application risk assessment. Each assumption and factor is detailed in the 2012 Residential 

SOPs7. 

Application Rate: 

Application rates are listed in Table 3.3. 

Body Weight

For adults, when an endpoint is not sex-specific (i.e., the endpoints are based on developmental 

or fetal effects) a body weight of 80 kg is typically used in risk assessment; however, in this case, 

a female-specific body weight of 69 kg was used. While the endpoint of concern, RBC AChE 

inhibition, is not sex-specific, the female-specific body weight was used to protect for pregnant 

women due to uncertainty in the human dose-response relationship for neurodevelopmental 

effects (See Section 4.4). For children, body weights of 57, 32 and 11 kg was used to assess 

exposure to children 11 to <16 years, 6 to <11 years, and 1 to <2 years old. 

Turf Transferable Residue (TTR) Data: 

Liquid Formulations: 

 

7

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Chemical-specific TTR data are available for bensulide and are summarized in Table 

6.2.1 (review: D413875, 10/29/13, A. Rivera-Lupiañez). The study includes TTR data on 

bensulide and its metabolite, bensulide oxon, that dislodged from turf treated with a 

liquid formulation containing bensulide at a rate of 12.5 lb ai/A. The product was 

watered in immediately following the application. Residues were sampled using the 

modified California Roller technique. First-order dissipation kinetics was assumed in 

order to generate dissipation curves for bensulide and combined residues of bensulide and 

bensulide oxon. The summary of statistics includes only post-irrigation measurements as 

the product labels require the product to be watered in. Due to the differences in the 

dissipation of bensulide and the oxon, residues of the oxon were adjusted by the toxicity 

adjustment factor (TAF; oxon residue, ug/cm2

 * 50X TAF), and total residues (bensulide 

+ adjusted oxon) were used to determine the risk resulting from exposures following 

bensulide applications. For assessment of residential post-application exposures, the 

predicted day 0 combined residue (0.479 ug/cm2

) was used in the exposure calculations 

(see Table 6.2.1 below). 

Table 6.2.1. Regression Summary for Turf Treated with BENSUMEC 4LF (MRID 44799001) 

Statistic Bensulide Bensulide 

oxon 

Combined 

residues 

Combined Residue with 

50x factor for oxon1

Actual Application Rate (lb ai/A) 12.6 

Actual Average Residues 8-12 

hours after application (μg/cm2

) 

 (post-irrigation ) 

0.2093 0.0057 0.2144 0.4627 

Predicted Day 0 Residues 

(μg/cm2) (post-irrigation ) 0.201 0.002 0.206 0.479 

Slope -0.27 -0.049 -0.271 -0.303 

Half-life (days) 2.6 14.2 2.6 2.3 

R2 0.897 0.0285 0.8934 0.8123 

Bolded value represents residue value used in post-application exposure calculations. 1

 Combined residue, ug/cm2 = [(oxon residue, ug/cm2) * 50X TAF] + [bensulide residue, ug/cm2) 

Solid Formulations: 

Chemical-specific TTR data are not available for solid formulations applied to turf; liquid 

TTR data were used as surrogate. This is considered a health protective approach since, 

in general, granular formulations tend to result in lower percent transfer from turf than do 

liquid formulations (e.g., the 2012 Residential SOP turf default percent transfer factor is 

1% for liquids and 0.2% for granulars).

Exposure Duration: 

The exposure duration for residential post-application exposures is steady-state. Granule 

ingestion is considered episodic and thus is an acute duration. 

Residential Post-application Non-Cancer Exposure and Risk Equations 
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The algorithms used to estimate residential post-application exposure and dose can be found in 

the 2012 Residential SOPs8

. 

Combining Exposure and Risk Estimates 

Since dermal and incidental oral exposure routes share a common toxicological endpoint, risk 

estimates have been combined for those routes. The incidental oral scenarios (i.e., hand-tomouth and object-to-mouth) should be considered inter-related, and it is likely that they occur 

interspersed amongst each other across time. Combining these scenarios with the dermal 

exposure scenario would be overly-conservative because of the conservative nature of each 

individual assessment. Therefore, the post-application exposure scenarios that were combined 

for children 1 < 2 years old are the dermal and hand-to-mouth scenarios. This combination 

should be considered a protective estimate of children’s exposure. 

Summary of Residential Post-application Non-Cancer Exposure and Risk Estimates 

A summary of the residential post-application exposure and risk estimates for bensulide and its 

oxon is in Tables 6.2.2 (for liquid formulations) and 6.2.3 (for solid formulations) below. Risk 

estimates are of concern (MOEs < 1000) for dermal exposure for adults and children conducting 

high exposure activities on treated turf; for dermal exposure for adults and youths golfing; for 

hand-to-mouth exposure for children on treated turf; and for episodic granule ingestion exposure. 

Table 6.2.2. Residential Post-Application Non-Cancer Exposure and Risk Estimates for Bensulide + Oxon 

(Liquid Formulations). 

Lifestage 

Post-application Exposure 

Scenario Application 

Rate1

Dose 

(mg/kg/day)2

MOEs 

(LOC = 

1000)3

Combined Routes 

(X indicates 

included in 

Combined MOE) 

Combined MOEs 

(LOC = 1000)4

Use Site Route of 

Exposure 

Adult 

Lawns/ Turf 

Dermal – Turf 

12.5 lb ai/A

0.187 32 

NA 

Dermal - Mowing 0.0038 1,600 

Dermal – Golfing 0.0147 410 

Youth (11 to 

< 16 years) 

Dermal- Mowing 0.00378 1,600 

Dermal – Golfing 0.0148 410 

Youth (6 to < 

11 years) Dermal- Golfing 0.0174 350 

Child (1 to < 

2 years) 

Dermal - Turf 0.32 19 X 16 Hand-to-Mouth 0.0656 91 X 

Object-to-Mouth 0.00199 3,000 NA Soil Ingestion 0.00042 14,000 

1 Based on registered labels (see Table 3.3). Predicted Day 0 combined (bensulide + adjusted oxon) residue value (0.479 ug/cm2; from MRID 

44799001) used in calculations. 

2 Dose (mg/kg/day) algorithms provided in 2012 Residential SOPs (http://www2.epa.gov/pesticide-science-and-assessing-pesticiderisks/standard-operating-procedures-residential-pesticide). 

3 MOE = Dermal and Incidental Oral POD (6 mg/kg/day) ÷ Dose (mg/kg/day). 

4 Combined MOE = 1 ÷ (1/dermal MOE) + (1/incidental oral MOE), where applicable. 

 

8

 Available: http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/standard-operating-proceduresresidential-pesticide
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Table 6.2.3. Residential Post-Application Non-Cancer Exposure and Risk Estimates for Bensulide + Oxon (Solid 

Formulations). 

Lifestage 

Post-application Exposure 

Scenario Application 

Rate1

Dose 

(mg/kg/day)2

MOEs 

(LOC = 

1000)3

Combined Routes 

(X indicates 

included in 

Combined MOE) 

Combined MOEs

(LOC = 1000)4

Use Site Route of Exposure 

Adult 

Lawns/ Turf 

Dermal – Turf 12.5 lb ai/A 0.2082 29 

NA 

Dermal - Mowing 0.0038 1,600 

Dermal – Golfing 16 lb ai/A 0.0188 320 

Youth (11 to 

< 16 years) 

Dermal- Mowing 12.5 lb ai/A 0.00378 1,600 

Dermal – Golfing 

16 lb ai/A 

0.0189 320 

Youth (6 to < 

11 years) Dermal- Golfing 0.0222 270 

Child (1 to < 

2 years) 

Dermal - Turf 

12.5 lb ai/A

0.3527 17 X 

16 Hand-to-Mouth 0.0325 180 X 

Object-to-Mouth 0.00199 3,000 

NA Soil Ingestion 0.00042 14,000 

Episodic Granule 

Ingestion (12.5% ai) 3.41 3.2 

1 Based on registered labels (See Table 3.3). Predicted Day 0 combined (bensulide + adjusted oxon) residue value (0.479 ug/cm2; from MRID 

44799001) used in calculations. 

2 Dose (mg/kg/day) algorithms provided in 2012 Residential SOPs (http://www2.epa.gov/pesticide-science-and-assessing-pesticiderisks/standard-operating-procedures-residential-pesticide). 

3 MOE = Dermal and Incidental Oral POD (6 mg/kg/day) ÷ Dose (mg/kg/day). 

4 Combined MOE = 1 ÷ (1/dermal MOE) + (1/incidental oral MOE), where applicable. 

6.4 Residential Risk Estimates for Use in Aggregate Assessment 

As the residential turf scenarios are risks of concern, there are no residential risk estimates 

recommended for steady state aggregate assessment. 

6.5 Residential Bystander Post-application Inhalation Exposure 

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

individuals nearby pesticide applications. The Agency sought expert advice and input on issues 

related to volatilization of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act 

Scientific Advisory Panel (SAP) in December 2009, and received the SAP’s final report on 

March 2, 2010 (http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2009-0687-

0037). The Agency has evaluated the SAP report and has developed a Volatilization Screening 

Tool and a subsequent Volatilization Screening Analysis 

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

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

inhalation toxicological studies) or further analysis is required for bensulide. 

The California Department of Pesticide Regulation (DPR) has released a draft report on its air 

monitoring network for public comment. In 2011, DPR established a monitoring network to 

sample ambient air for multiple pesticides in three communities on a regular basis. The draft 

report of results for the monitoring in 2014 is available at 

http://www.cdpr.ca.gov/docs/emon/airinit/air_network_results.htm. In the draft Air Monitoring 

Network Results for 2014 report, there were 0 detections of bensulide of 157 samples. 

Furthermore, in the 2012 and 2013 reports, there were 0 detections of bensulide. In the 2011 
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report, there were 5 detects of bensulide of 142 samples; all detects were below the quantitation 

limit. 

6.6 Non-Occupational Spray Drift Exposure and Risk Estimates 

Off-target movement of pesticides can occur via many types of pathways and it is governed by a 

variety of factors. Sprays that are released and do not deposit in the application area end up offtarget and can lead to exposures to those it may directly contact. They can also deposit on 

surfaces where contact with residues can eventually lead to indirect exposures (e.g., children 

playing on lawns where residues have deposited next to treated fields). The potential risk 

estimates from these residues can be calculated using drift modeling onto 50 feet wide lawns 

coupled with methods employed for residential risk assessments for turf products. 

The approach to be used for quantitatively incorporating spray drift into risk assessment is based 

on a premise of compliant applications which, by definition, should not result in direct exposures 

to individuals because of existing label language and other regulatory requirements intended to 

prevent them.9

 Direct exposures would include inhalation of the spray plume or being sprayed 

directly. Rather, the exposures addressed here are thought to occur indirectly through contact 

with impacted areas, such as residential lawns, when compliant applications are conducted. 

Given this premise, exposures for children (1 to <2 years old) and adults who have contact with 

turf where residues are assumed to have deposited via spray drift thus resulting in an indirect 

exposure are the focus of this analysis analogous to how exposures to turf products are 

considered in risk assessment. 

For adults, when an endpoint is not sex-specific (i.e., the endpoints are based on developmental 

or fetal effects) a body weight of 80 kg is typically used in risk assessment; however, in this case, 

a female-specific body weight of 69 kg was used. While the endpoint of concern, RBC AChE 

inhibition, is not sex-specific, the female-specific body weight was used to protect for pregnant 

women due to uncertainty in the human dose-response relationship for neurodevelopmental 

effects (See Section 4.4). 

In order to evaluate the drift potential and associated risks, an approach based on drift modeling 

coupled with techniques used to evaluate residential uses of pesticides was utilized. Essentially, 

a residential turf assessment based on exposure to deposited residues has been completed to 

address drift from the agricultural applications of bensulide. In the spray drift scenario, the 

deposited residue value was determined based on the amount of spray drift that may occur at 

varying distances from the edge of the treated field using the AgDrift® (v2.1.1) model and the 

Residential Exposure Assessment Standard Operating Procedures Addenda 1: Consideration of 

Spray Drift Policy. Once the deposited residue values were determined, the remainder of the 

spray drift assessment was based on the algorithms and input values specified in the recently 

revised (2012) Standard Operating Procedures For Residential Risk Assessment (SOPs). 

For bensulide, chemical-specific turf transferable residue (TTR) data are available and were used 

for assessment of spray drift risks. See Section 6.2 for a description of the TTR data. The data 

 

9 This approach is consistent with the requirements of the EPA’s Worker Protection Standard. 
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include measurements on bensulide and the oxon. For assessment of exposures resulting from 

spray drift, the predicted day 0 combined (bensulide + adjusted oxon) residue value (0.479 

ug/cm2

) was adjusted for differences in application rate between the study and the registered 

agricultural uses, and the adjusted residue value was used in the exposure calculations. 

A screening approach was developed based on the use of the AgDrift® model in situations where 

specific label guidance that defines application parameters is not available.10 AgDrift® is 

appropriate for use only when applications are made by aircraft, airblast orchard sprayers, and 

groundboom sprayers. When AgDrift® was developed, a series of screening values (i.e., the Tier 

1 option) were incorporated into the model and represent each equipment type and use under 

varied conditions. The screening options specifically recommended in this methodology were 

selected because they are plausible and represent a reasonable upper bound level of drift for 

common application methods in agriculture. These screening options are consistent with how 

spray drift is considered in a number of ecological risk assessments and in the process used to 

develop drinking water concentrations used for risk assessment. In all cases, each scenario is to 

be evaluated unless it is not plausible based on the anticipated use pattern (e.g., herbicides are 

not typically applied to tree canopies) or specific label prohibitions (e.g., aerial applications are 

not allowed). Table 6.6.1 provides the screening level drift related risk estimates. In many 

cases, risk estimates are of concern when the screening level estimates for spray drift are used as 

the basis for the analysis. In order to account for this issue and to provide additional risk 

management options, additional spray drift deposition fractions were also considered. These 

drift estimates represent plausible options for pesticide labels. 

Combined Risk Estimates from Lawn Deposition Adjacent to Applications 

The spray drift risk estimates are based on an estimated deposited residue concentration as a 

result of the screening level agricultural application scenarios. Bensulide is registered in both 

liquid and granular formulation end-use products. Granular formulations, applied as solid 

materials and no liquid spray, have different drift patterns than liquid sprays, and as such, need to 

be considered in a separate analysis. However, from a human health perspective, off-site 

movement of granular products would result in lower risk estimates than those for liquid 

products (e.g., less drift occurs and there is less exposure uptake for granules). In most cases, 

pesticides also have liquid end-use products and an analysis for them would be protective of 

potential risks from granular drift; thus, granular products are not assessed. 

Bensulide is registered on vegetable crops and golf courses, and can be applied via groundboom 

equipment at a maximum single application rate of 6 lb ai/A for vegetable crops (9 lb ai/A on 

SLN labels) and 12.5 lb ai/acre for golf courses. The recommended drift scenario screening 

level options are listed below: 

 Groundboom applications are based on the AgDrift® option for high boom height and 

using very fine to fine spray type using the 90th percentile results. 

 

10 http://www.agdrift.com/ 
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In addition to the screening level spray drift scenarios described above, additional results are 

provided which represent viable drift reduction technologies (DRTs) that represent potential risk 

management options. In particular, different spray qualities have been considered as well as the 

impact of other application conditions (e.g., boom height and crop canopy conditions). 

Dermal risk estimates were calculated for adults. Dermal and incidental oral risk estimates for 

children (1 to <2 years old) were combined because the toxicity endpoint for each route of 

exposure is the same (RBC AChE inhibition). The total applicable LOC is 1000, so MOEs 

<1000 represent risk estimates of concern. 

Risk estimates related to spray drift are of concern at various distances from the edge of the field 

for adults and children (1 to <2 years) depending on the spray drift scenario. Adult and children 

risk estimates are summarized in Table 6.6.1. For adults, the screening level scenario indicates 

the LOC is exceeded at a distance of less than 25 feet for applications to vegetables and less than 

75 feet for applications to golf courses. For children, the screening level scenario indicates the 

LOC is exceeded at a distance of less than 75 feet for applications to vegetables and 150 feet for 

applications to golf courses. Drift reduction technologies, such as using coarser sprays and 

lowering boom height for groundboom sprayers, reduces risk concerns; however, there are still 

risk estimates of concern at the field edge for some scenarios. 

 
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Table 6.6.1. Spray Drift Risk Estimate Summary for Bensulide. 

Crop / 

Application 

Type 

Spray Type/ 

Nozzle 

Configuration 

Application 

Rate 

(lb ai/A) 

Estimated 

TTR 

(ug/cm2) 

MOE at Different Distances from Edge of Field 

LOC = 1000

At Edge 10 Feet 25 Feet 50 Feet 75 Feet 100 Feet 125 feet 150 fe

Adults (Dermal Exposure Only); Vegetable Crops (6 lb ai/acre) 

Vegetable / 

Groundboom 

Screening Level

High Boom Very 

fine to Fine 

6 0.2299 

360 720 1,200 1,900 2,700 3,300 3,900 4,800 

Low Boom Very 

fine to Fine 780 2,100 3,300 5,100 6,700 8,300 9,500 11,00

High Boom Fine 

to Medium / 

Coarse 1,400 3,500 5,100 7,400 9,500 11,000 13,000 13,00

Low Boom Fine to 

Medium / Coarse 2,000 5,600 8,300 11,000 13,000 17,000 22,000 22,00

Adults (Dermal Exposure Only); Vegetable Crops (SLN rate of 9 lb ai/acre)

Vegetable / 

Groundboom 

Screening Level

High Boom Very 

fine to Fine 

9 0.345 

240 480 790 1,300 1,800 2,200 2,600 3,200 

Low Boom Very 

fine to Fine 520 1,400 2,200 3,400 4,400 5,600 6,400 7,400 

High Boom Fine 

to Medium / 

Coarse 910 2,300 3,400 4,900 6,400 7,400 8,900 8,900 

Low Boom Fine to 

Medium / Coarse 1,300 3,700 5,600 7,400 8,900 11,000 15,000 15,00

Adults (Dermal Exposure Only); Golf Courses

Golf Course/ 

Groundboom 

Screening Level

High Boom Very 

fine to Fine 

12.5 0.479 

170 340 570 910 1,300 1,600 1,900 2,300 

Low Boom Very 

fine to Fine 380 1,000 1,600 2,500 3,200 4,000 4,600 5,300 

High Boom Fine 

to Medium / 

Coarse 650 1,700 2,500 3,600 4,600 5,300 6,400 6,400 

Low Boom Fine to 

Medium / Coarse 970 2,700 4,000 5,300 6,400 8,000 11,000 11,00

Children (1 to < 2 years old) (Dermal and Incidental Oral Exposure); Vegetable Crops (6 lb ai/acre) 
Bensulide Human Health Risk Assessment DP No. D428598 

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Table 6.6.1. Spray Drift Risk Estimate Summary for Bensulide. 

Crop / 

Application 

Type 

Spray Type/ 

Nozzle 

Configuration 

Application 

Rate 

(lb ai/A) 

Estimated 

TTR 

(ug/cm2) 

MOE at Different Distances from Edge of Field 

LOC = 1000

At Edge 10 Feet 25 Feet 50 Feet 75 Feet 100 Feet 125 feet 150 fe

Vegetable / 

Groundboom 

Screening Level

High Boom Very 

fine to Fine 

6 0.2299 

170 350 580 930 1,300 1,600 1,900 2,300 

Low Boom Very 

fine to Fine 380 1,000 1,600 2,500 3,200 4,100 4,600 5,400 

High Boom Fine 

to Medium/Coarse 660 1,700 2,500 3,600 4,600 5,400 6,500 6,500 

Low Boom Fine to 

Medium/Coarse 980 2,700 4,100 5,400 6,500 8,100 11,000 11,00

Children (1 to < 2 years old) (Dermal and Incidental Oral Exposure); Vegetable Crops (SLN rate of 9 lb ai/acre)

Vegetable / 

Groundboom 

Screening Level

High Boom Very 

fine to Fine 

9 

120 230 390 620 860 1,100 1,300 1,500 

Low Boom Very 

fine to Fine 250 680 1,100 1,700 2,200 2,700 3,100 3,600 

High Boom Fine 

to Medium/Coarse 440 1,100 1,700 2,400 3,100 3,600 4,300 4,300 

Low Boom Fine to 

Medium/Coarse 650 1,800 2,700 3,600 4,300 5,400 7,200 7,200 

Children (1 to < 2 years old) (Dermal and Incidental Oral Exposure); Golf Courses

Golf Course/ 

Groundboom 

Screening Level

High Boom Very 

fine to Fine

12.5 0.479 

83 170 280 440 620 780 920 1,100 

Low Boom Very 

fine to Fine 180 490 780 1,200 1,600 1,900 2,200 2,600 

High Boom Fine 

to Medium/Coarse 320 820 1,200 1,700 2,200 2,600 3,100 3,100 

Low Boom Fine to 

Medium/Coarse 470 1,300 1,900 2,600 3,100 3,900 5,200 5,200 

Bolded values are below the LOC of 1000. 
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7.0 Aggregate Exposure/Risk Characterization

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

risks from three major sources: food, drinking water, and residential exposures. In an aggregate 

assessment, exposures from relevant sources are added together and compared to quantitative 

estimates of hazard (e.g., a NOAEL or PAD), or the risks themselves can be aggregated. When 

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

duration of exposure. 

7.1 Acute Aggregate Risk 

The acute aggregate risk assessment combines oral exposure through food and drinking water 

which is represented by the acute dietary assessment, refer to Section 5.4.3. 

7.2 Steady-state Aggregate Risk 

The steady-state aggregate assessment combines steady-state dietary (food and water) and 

residential exposures. Because there are risks of concern associated with dietary and residential 

exposure, an aggregate risk assessment was not conducted. 

7.3 Cancer Aggregate Risk 

Bensulide has been classified as not likely to be carcinogenic in humans via relevant routes of 

exposure; therefore, a cancer aggregate assessment is not needed. 

8.0 Cumulative Exposure/Risk Characterization

OPs, like bensulide, share the ability to inhibit AChE through phosphorylation of the serine 

residue on the enzyme leading to accumulation of acetylcholine and ultimately cholinergic 

neurotoxicity. This shared MOA/AOP is the basis for the OP common mechanism grouping per 

OPP’s Guidance For Identifying Pesticide Chemicals and Other Substances that have a Common 

Mechanism of Toxicity (USEPA, 1999). The 2002 and 2006 CRAs used brain AChE inhibition 

in female rats as the source of dose response data for the relative potency factors and PODs for 

each OP, including bensulide. Prior to the completion of Registration Review, OPP will update 

the OP CRA on AChE inhibition to incorporate new toxicity and exposure information available 

since 2006. 

As described in Section 4.4, OPP has retained the FQPA Safety Factor for OPs, including 

bensulide, due to uncertainties associated with neurodevelopmental effects in children and 

exposure to OPs. There is a lack of an established MOA/AOP for the neurodevelopment 

outcomes which precludes the Agency from formally establishing a common mechanism group 

per the Guidance For Identifying Pesticide Chemicals and Other Substances that have a 

Common Mechanism of Toxicity (USEPA, 1999) based on that outcome. Moreover, the lack of a 

recognized MOA/AOP and other uncertainties with exposure assessment in the epidemiology 

studies prevent the Agency from establishing a causal relationship between OP exposure and 
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neurodevelopmental outcomes. The Agency will continue to evaluate the epidemiology studies 

associated with neurodevelopmental outcomes and OP exposure prior to the release of the 

revised DRA. During this period, the Agency will determine whether or not it is appropriate to 

apply the draft guidance document entitled, Pesticide Cumulative Risk Assessment: Framework 

for Screening Analysis for the neurodevelopment outcomes. 

9.0 Occupational Exposure/Risk Characterization

Exposure to bensulide is assessed for handler scenarios; exposure to bensulide and bensulide 

oxon was assessed for post-application scenarios.

9.1 Steady-State Handler Risk 

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

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

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

(amount of chemical used in each application), the kinds of equipment used, the target being 

treated, and the level of protection used by a handler can cause exposure levels to differ in a 

manner specific to each application event. 

Based on the anticipated use patterns and current labeling, types of equipment and techniques 

that can potentially be used, occupational handler exposure is expected from the proposed uses. 

The quantitative exposure/risk assessment developed for occupational handlers is based on the 

following scenarios: 

 Mixing/loading granules for tractor application, 

 Mixing/loading liquids for chemigation and groundboom application, 

 Applying granules via tractor, 

 Applying sprays via groundboom equipment, 

 Mixing/loading/applying liquids via handgun equipment, and 

 Mixing/loading/applying granules via rotary spreader. 

Occupational Handler Exposure Data and Assumptions 

A series of assumptions and exposure factors served as the basis for completing the occupational 

handler risk assessments. Each assumption and factor is detailed below on an individual basis.

Application Rate: 

A summary of application rates is provided in Table 3.3. 

Unit Exposures: It is the policy of HED to use the best available data to assess handler exposure. 

Sources of generic handler data, used as surrogate data in the absence of chemical-specific data, 

include PHED 1.1, the AHETF database, the Outdoor Residential Exposure Task Force 

(ORETF) database, or other registrant-submitted occupational exposure studies. Some of these 

data are proprietary (e.g., AHETF data) and subject to the data protection provisions of FIFRA. 

The standard values recommended for use in predicting handler exposure that are used in this 
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assessment, known as “unit exposures”, are outlined in the “Occupational Pesticide Handler Unit 

Exposure Surrogate Reference Table11”, which, along with additional information on HED 

policy on use of surrogate data, including descriptions of the various sources, can be found at the 

Agency website12. 

Area Treated or Amount Handled: 

Based on ExpoSAC Policy 9.1, the area treated or amount handled is assumed to be: 

 40 acres for tractor or groundboom applications to golf courses, 

 350 acres for chemigation applications, 

 80 acres for groundboom applications to typical field crops (vegetables), 

 1000 gallons for handgun applications to field crops (vegetables), and 

 5 acres for handgun/rotary spreader applications to golf courses. 

Exposure Duration: 

For bensulide, based on the proposed use, steady-state exposure is expected. 

Mitigation/Personal Protective Equipment: Estimates of dermal and inhalation exposure were 

calculated for various levels of personal protective equipment (PPE). Results are presented for 

the label-required PPE, and also with various levels of additional PPE, as necessary. A summary 

of PPE requirements in listed in Table 3.3. 

Body Weight: For adults, when an endpoint is not sex-specific (i.e., the endpoints are based on 

developmental or fetal effects) a body weight of 80 kg is typically used in risk assessment; 

however, in this case, a female-specific body weight of 69 kg was used. While the endpoint of 

concern, RBC AChE inhibition, is not sex-specific, the female-specific body weight was used to 

protect for pregnant women due to uncertainty in the human dose-response relationship for 

neurodevelopmental effects (See Section 4.4).

Occupational Handler Non-Cancer Exposure and Risk Estimate Equations 

The algorithms used to estimate non-cancer exposure and dose for occupational handlers can be 

found in the occupational and residential exposure (ORE) memo for bensulide (D428877, A. 

Gavalek and K. Lowe, 03/03/2016). 

Combining Exposures/Risk Estimates: 

A total aggregated risk index (ARI) was used since the LOC values for dermal exposure (1000) 

and inhalation exposure (3000) are different. The target ARI is 1; therefore, ARIs of less than 1 

are risk estimates of concern. The aggregate risk index (ARI) was calculated as follows. 

Aggregate Risk Index (ARI) = 1÷ [(Dermal LOC ÷ Dermal MOE)+ (Inhalation LOC ÷ Inhalation MOE)] 

 

11 Available: http://www2.epa.gov/sites/production/files/2015-09/documents/handler-exposure-table-2015.pdf 12 Available: http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-handlerexposure-data
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Summary of Occupational Handler Non-Cancer Exposure and Risk Estimates 

A summary of occupational handler risk estimates for bensulide with the label-required PPE is 

provided in Table 9.1.1 below. With the label-required PPE, all handler risk estimates 

(combined dermal and inhalation) are of concern (ARI < 1). A summary of handler risk 

estimates with additional PPE/ engineering controls to mitigate risks is provided in Table 9.1.2; 

most handler risk estimates are still of concern with the maximum PPE/ engineering controls. 
Bensulide Human Health Risk Assessment 

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Table 9.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Bensulide (with label-required PPE). 

Exposure Scenario Crop or Target 

Dermal Unit 

Exposure 

(μg/lb ai)1

Inhalation Unit 

Exposure 

(μg/lb ai)1

Maximum 

Application 

Rate2

Area 

Treated or 

Amount 

Handled 

Daily3

Dermal In

Dose 

(mg/kg/day)4

MOE5 

(LOC = 

1000) 

Dose 

(mg/kg/da

Mixer/Loader 

M/L, Granule, Tractor 

Application Golf Course DL/G: 3.4 PF 5: 0.34 16 lb ai/A 40 A 0.00316 1,900 0.00316 

M/L, Liquid, Chemigation

Cucurbit/ Brassica/ 

Fruiting/ Dry bulb 

Vegetables 

SL/ G: 37.6 PF 5: 0.0438 

6 lb ai/ A 350 A 0.114 53 0.00133 

SLN Vegetables 9 lb ai/A 0.171 35 0.002 

M/L, Liquid, Groundboom 

Application

Golf Course 12.5 lb ai/A 40 A 0.0272 220 0.000317 

Cucurbit/ Brassica/ 

Fruiting/ Dry bulb 

Vegetables 

6 lb ai/A 80 A 0.0261 230 0.000304 

SLN Vegetables 9 lb ai/A 0.0393 150 0.000457 

Applicator 

Applying Sprays via 

Groundboom Equipment

Golf Course 

SL/G: 16.1 PF 5: 0.068 

12.5 lb ai/A 40 A 0.0117 510 0.000493 

Cucurbit/ Brassica/ 

Fruiting/ Dry bulb 

Vegetables 

6 lb ai/A 80 A 0.0112 540 0.000472 

SLN Vegetables 9 lb ai/A 0.0168 360 0.00071 

Applying Granule via 

Tractor Golf Course SL/G: 7.2 PF 5: 0.24 16 lb ai/A 40 A 0.00668 900 0.00223 

Mixer/Loader/Applicator 

M/L/A, Liquid, Handgun 

Golf Course/ Lawn SL/ G: 880 PF 5: 0.38 12.5 lb ai/A 5 A 0.0797 75 0.000345 

Field Crop SL/G: 390 PF 5: 0.78 0.16 lb ai/gal 1000 gal 0.0904 66 0.00181 

L/A, Granule, Rotary 

Spreader 

Lawn DL/G: 130 PF 5: 2 12.5 lb ai/A 5 A 0.0118 510 0.00181 

Golf Course 16 lb ai/A 0.0151 400 0.00232 

1 Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (March 2013); Level of mitigation: SL/G =Single layer clothing and gloves

and gloves; PF 5 = respirator with protection factor of 5; PF 10 = respirator with protection factor of 10; EC = engineering controls. 

2 Based on registered labels (see Table 3.3). 

3 Exposure Science Advisory Council Policy #9.1. 4 Dermal Dose = Dermal Unit Exposure (μg/lb ai) × Conversion Factor (0.001 mg/μg) × Application Rate (lb ai/acre or gal) × Area Treated or Amount Handled (A or g

kg). 

5 Dermal MOE = Dermal NOAEL (6 mg/kg/day) ÷ Dermal Dose (mg/kg/day). 

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

7 Inhalation MOE = Inhalation NOAEL (6 mg/kg/day) ÷ Inhalation Dose (mg/kg/day). 

8 ARI = Aggregate Risk Index = 1÷ [(Dermal LOC ÷ Dermal MOE) + (Inhalation LOC ÷ Inhalation MOE)]. 
Bensulide Human Health Risk Assessment 

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Table 8.1.2. Occupational Handler Non-Cancer Exposure and Risk Estimates for Bensulide (with additional level of PPE). 

Exposure Scenario Crop or Target 

Dermal Unit 

Exposure 

(μg/lb ai)1

Inhalation Unit 

Exposure 

(μg/lb ai)1

Maximum 

Application 

Rate2

Area Treated or 

Amount 

Handled Daily3

SL/G + PF 5 DL/G + PF 5 SL/G 

AR

Mixer/Loader 

M/L, Granule, Tractor 

Application Golf Course 

SL/G: 6.9 

DL/G: 3.4 

EC: 8.6 

PF 5: 0.34 

PF 10: 0.17 

EC: 0.083 

16 lb ai/A 40 A 0.38 0.48 (current PPE) 

M/L, Liquid, 

Chemigation

Cucurbit/ Brassica/ 

Fruiting/ Dry bulb 

Vegetables 

SL/ G: 37.6 

DL/ G: 29.1 

EC: 8.6 

PF 5: 0.0438 

PF 10: 0.0219 

EC: 0.083 

6 lb ai/ A 

350 A 

0.051 

(current PPE) 0.065 

SLN Vegetable 9 lb ai/A 0.034 (current PPE) 0.043 

M/L, Liquid, 

Groundboom 

Application

Golf Course 12.5 lb ai/A 40 A 0.21 (current PPE) 0.27 

Cucurbit/ Brassica/ 

Fruiting/ Dry bulb 

Vegetables 

6 lb ai/A 

80 A 

0.22 

(current PPE) 0.29 

SLN Vegetables 9 lb ai/A 0.14 (current PPE) 0.19 

Applicator 

Applying Sprays via 

Groundboom 

Equipment

Golf Course 

SL/G: 16.1 

DL/ G: 12.6 

EC: 5.1 

PF 5: 0.068 

PF 10: 0.034 

EC: 0.043 

12.5 lb ai/A 40 A 0.45 (current PPE) 0.57 

Cucurbit/ Brassica/ 

Fruiting/ Dry bulb 

Vegetables 

6 lb ai/A 

200 A 

0.48 

(current PPE) 0.59 

SLN Vegetables 9 lb ai/A 0.32 (current PPE) 0.4 

Applying Granule via 

Tractor Golf Course 

SL/G: 7.2 

DL/ G: 4.2 

EC: 2 

PF 5: 0.24 

PF 10: 0.12 

EC: 0.22 

16 lb ai/A 40 A 0.45 (current PPE) 0.56 

Mixer/Loader/Applicator 

M/L/A, Liquid, Handgun 

Golf Course/ Lawn SL/ G: 880 DL/G: 450 PF 5: 0.38 PF 10: 0.19 12.5 lb ai/A 5 A 0.074 (current PPE) 0.15 

Field Crop SL/G: 390 DL/G: 290 PF 5: 0.78 PF 10: 0.39 0.16 lb ai/gal 1000 gal 0.062 (current PPE) 0.082 

L/A, Granule, Rotary 

Spreader 

Lawn SL/G: 240 

DL/G: 130 

PF 5: 2 

PF 10: 1 

12.5 lb ai/A 

5 A 

0.22 0.35 (current PPE) 

Golf Course 16 lb ai/A 0.18 0.27 (current PPE) 

1 Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (March 2013); Level of mitigation: SL/G =Single layer clothing and gloves

and gloves; PF 5 = respirator with protection factor of 5; PF 10 = respirator with protection factor of 10; EC = engineering controls. 
Bensulide Human Health Risk Assessment 

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2 Based on registered labels (see Table 3.3). 

3 Exposure Science Advisory Council Policy #9.1. 4 ARI = Aggregate Risk Index = 1÷ [(Dermal LOC ÷ Dermal MOE) + (Inhalation LOC ÷ Inhalation MOE)]. 
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9.2 Steady-State Post-Application Risk 

HED uses the term post-application to describe exposures that occur when individuals are 

present in an environment that has been previously treated with a pesticide (also referred to as reentry exposure). Such exposures may occur when workers enter previously treated areas to 

perform job functions, including activities related to crop production, such as scouting for pests 

or harvesting. Post-application exposure levels vary over time and depend on such things as the 

type of activity, the nature of the crop or target that was treated, the type of pesticide application, 

and the chemical’s degradation properties. In addition, the timing of pesticide applications, 

relative to harvest activities, can greatly reduce the potential for post-application exposure. 

9.2.1 Dermal Post-Application Risk 

Bensulide is registered for use on golf course turf and on vegetable crops. A dermal postapplication assessment has been conducted for the golf course turf use. However, since 

bensulide is applied to vegetables as a preplant or preemergence application only, occupational 

post-application dermal exposures are not anticipated for these uses. There is a low potential for 

occupational post-application exposure when pre-emergent herbicides are used. Bensulide is 

applied to the soil directly and is soil incorporated well before the crops are mature. The timing 

of the application of bensulide can greatly reduce the potential for post-application exposure. 

Minimal exposure during harvesting or any other late season activities is expected since 

bensulide is applied pre-emergent. Therefore, HED does not require a post-application 

occupational exposure assessment (HED Exposure Science Advisory Council Policy No. 008). 

Occupational Post-application Dermal Exposure Data and Assumptions 

A series of assumptions and exposure factors served as the basis for completing the occupational 

post-application risk assessments for the golf course use. Each assumption and factor is detailed 

below on an individual basis.

Exposure Duration: 

For bensulide, an exposure profile consistent with steady-state exposure is expected. 

Transfer Coefficients: It is the policy of HED to use the best available data to assess postapplication exposure. Sources of generic post-application data, used as surrogate data in the 

absence of chemical-specific data, are derived from ARTF exposure monitoring studies, and, as 

proprietary data, are subject to the data protection provisions of FIFRA. The standard values 

recommended for use in predicting post-application exposure that are used in this assessment, 

known as “transfer coefficients”, are presented in the ExpoSAC Policy 313” which, along with 

additional information about the ARTF data, can be found at the Agency website14. Table 

9.2.1.1 provides a summary of the anticipated post-application activities and associated transfer 

coefficients for the proposed crops/use sites. 

 

13 Available: http://www2.epa.gov/sites/production/files/2015-08/documents/exposac-policy-3-march2013.pdf 14 Available: http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-postapplication-exposure
Bensulide Human Health Risk Assessment DP No. D428598 

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Table 9.2.1.1. Anticipated Post-Application Activities and Dermal Transfer Coefficients. 

Proposed Crops 

Policy Crop 

Group 

Category 

Crop 

Height 

Foliage 

Density 

Transfer 

Coefficients 

(cm2/hr)

Activities 

Golf Course Turf Low Full 3700 Maintenance 

Application Rate: 

Application rates are listed in Table 3.3. 

Exposure Time: The average occupational workday is assumed to be 8 hours. 

Turf Transferable Residues: Chemical-specific TTR data are available for the liquid formulation 

of bensulide. See Section 6.2 for a description of the TTR data. The data include measurements 

on bensulide and the oxon. Due to the differences in the dissipation of bensulide and the oxon, 

residues of the oxon were adjusted by the toxicity adjustment factor (TAF; oxon residue, ug/cm2

* 50X TAF), and total residues (bensulide + adjusted oxon) were used to determine the risk 

resulting from exposures following bensulide applications. Since no data are available for the 

granular formulation, the liquid formulation residue data were used as a surrogate. As noted 

above, this is considered a health protective approach since, in general, granular formulations 

tend to result in lower percent transfer from turf than do liquid formulations (e.g., the 2012 

Residential SOP turf default percent transfer factor is 1% for liquids and 0.2% for granulars).

Body Weight: For adults, when an endpoint is not sex-specific (i.e., the endpoints are based on 

developmental or fetal effects) a body weight of 80 kg is typically used in risk assessment; 

however, in this case, a female-specific body weight of 69 kg was used. While the endpoint of 

concern, RBC AChE inhibition, is not sex-specific, the female-specific body weight was used to 

protect for pregnant women due to uncertainty in the human dose-response relationship for 

neurodevelopmental effects (See Section 4.4). 

Occupational Post-application Non-Cancer Dermal Exposure and Risk Estimate Equations 

The algorithms used to estimate non-cancer exposure and dose for occupational post-application 

workers can be found in the occupational and residential exposure (ORE) memo for bensulide 

(D428877, A. Gavalek and K. Lowe, 03/03/2016). 

Occupational Post-application Non-Cancer Dermal Risk Estimates 

Occupational post-application risks were estimated for workers; risk estimates were of concern 

until 5 days after treatment (DAT 5). See tables 9.2.1.2 (for liquid formulations) and 9.2.1.3 (for 

granular formulations) below for a summary of the occupational post-application risk estimates.
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Table 9.2.1.2. Occupational Post-application Non-Cancer Exposure and Risk Estimates for Bensulide + Oxon (with 50X 

TAF) (Liquid Formulations).

Crop/Site Activities Transfer Coefficient 

(cm2/hr) 

DAT 

TTR1 Dermal Dose 

(mg/kg/day)2

MOE 

(LOC = 1000)3

Golf Course Maintenance 3700 

0 0.475 0.0204 290 

1 0.351 0.0151 400 

2 0.259 0.0111 540 

3 0.192 0.0082 730 

4 0.141 0.0061 990 

5 0.105 0.00448 1,300 

1 TTR = Data from MRID 44799001. Total TTR, ug/cm2 = [ (oxon residue, ug/cm2) * 50 X TAF] + [bensulide residue, ug/cm2). 

2 Daily Dermal Dose = [DFR (μg/cm2

) × Transfer Coefficient × 0.001 mg/μg × 8 hrs/day × dermal absorption (10%)]  BW (69 kg).

3 MOE = POD (6 mg/kg/day) / Daily Dermal Dose. 

Table 9.2.1.3. Occupational Post-application Non-Cancer Exposure and Risk Estimates for Bensulide + 

Oxon (with 50X TAF) (Solid Formulations).

Crop/Site Activities Transfer Coefficient 

(cm2/hr) 

DAT 

TTR1 Dermal Dose 

(mg/kg/day)2

MOE 

(LOC = 1000)3

Golf Course Maintenance 3700 

0 0.6083 0.026097 230 

1 0.4493 0.019276 310 

2 0.3319 0.014238 420 

3 0.2452 0.010517 570 

4 0.181 0.00777 770 

5 0.134 0.00574 1,000 

1 TTR = Default assumption that 0.2% of application rate available as TTR on day 0. Dissipation rate and oxon conversion data from MRID 

44799001. Total TTR, ug/cm2

 = [ (oxon residue, ug/cm2) * 50 X TAF] + [bensulide residue, ug/cm2). 

2 Daily Dermal Dose = [DFR (μg/cm2

) × Transfer Coefficient × 0.001 mg/μg × 8 hrs/day × dermal absorption (10%)]  BW (69 kg).

3 MOE = POD (6 mg/kg/day) / Daily Dermal Dose. 

Restricted Entry Interval 

Bensulide is classified as Toxicity Category III via the dermal route, Toxicity Category IV for 

dermal irritation, and Toxicity Category III for eye irritation. It is not a skin sensitizer. Under 

40 CFR 156.208 (c) (2), ai’s classified as Acute III or IV for acute dermal, eye irritation and 

primary skin irritation are assigned a 12-hour REI. However, steady-state post-application risk 

estimates were a concern up to Day 5 for golf course maintenance activities. Therefore, HED is 

recommending that the REI for golf courses be revised on the label to address those concerns. 

9.2.2 Inhalation Post-Application Risk 

There are multiple potential sources of post-application inhalation exposure to individuals 

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

include volatilization of pesticides and resuspension of dusts and/or particulates that contain 

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

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

(SAP) in December 2009, and received the SAP’s final report on March 2, 2010 
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(http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2009-0687-0037). The 

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

subsequent Volatilization Screening Analysis 

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

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

inhalation toxicological studies) or further analysis is required for bensulide. 

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

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

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

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

10.0 Public Health and Pesticide Epidemiology Data 

Adapted from: S. Recore, D428879, 08/10/2015 

IDS records incidents resulting in higher severity outcomes in more detail, in a module called the 

Main IDS module. This system stores incident data for death, major and moderate incidents, and 

it includes more details about the location, date and nature of the incident. Main IDS incidents 

involving only one pesticide are considered to provide more certain information about the 

potential effects of exposure from the pesticide. The less severe human incidents (minor, 

unknown, or no effects outcomes) are reported by registrants as counts called aggregate 

summaries and are recorded in a separate module called Aggregate IDS. The SENSORPesticides database covers 11 states from 1998-2010, although reporting varies from state to 

state. Cases of pesticide-related illnesses are ascertained from a variety of sources. Although 

both occupational and non-occupational incidents are included in the database, SENSORPesticides focuses on occupational pesticide incidents, and is of particular value in providing that 

information. For this evaluation, both the IDS and SENSOR database were consulted for 

pesticide incident data on the active ingredient bensulide (PC Code: 009801). In addition, we 

sought information from the Agricultural Health Study (AHS); however, bensulide is not 

included in the AHS. 

Bensulide was previously reviewed in 1998 (J. Blondell and M. Spann, 2/9/1998, D239353). At 

the time, there were two incidents reported for bensulide in IDS from 1992 – February 1998. 

Upon review of these incidents, no recommendations were made and it was concluded that, 

“Very few illness cases have been reported due to bensulide and none have been confirmed.” 

The current IDS analysis from January 1, 2010 through August 25, 2015, shows 2 moderate 

severity incident reported involving bensulide in Main IDS and 5 minor severity incidents 

reported to Aggregate IDS. The query of SENSOR-Pesticides 1998-2011 identified a total of 38 

cases involving (pc code 009801). Of these 38 cases, 17 cases, stemming from seven events, 

involve a single ai and were reviewed further. Fourteen cases were low in severity and three 

cases were moderate in severity. Sixteen cases were occupational exposure. A total of 14 of the 

single ai cases reports were caused by two spray drift events.i

 

 

i

 SENSOR-Pesticides defines drift as “off-target movement of pesticide” which includes cases of volatilization. 
Bensulide Human Health Risk Assessment DP No. D428598 

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Conclusion: Based on the low frequency of incidents involving bensulide reported to both IDS 

and SENSOR-Pesticides, there does not appear to be a concern at this time. The Agency will 

continue to monitor the incident information and if a concern is triggered, additional analysis 

will be conducted. 

11.0 References

Bensulide. Acute and Steady State Probabilistic Aggregate Dietary (Food Only, and Food and 

Drinking Water) Exposure and Risk Assessments for Registration Review Risk Assessment; I. 

Negrón-Encarnación; D428878; 03/02/2016. 

Bensulide. Summary of Analytical Chemistry and Residue Data in Support of Registration 

Review; I. Negrón-Encarnación; D429307; 03/02/2016. 

Bensulide. Occupational and Residential Exposure Assessment in Support of Registration 

Review; A. Gavalek and K. Lowe; D428877; 03/03/2016. 

HASPOC Memo; Van Alstine, 2013; TXR # 0056738. 

HASPOC Memo; Leshin, 2015, TXR # 0057280. 

Bouchard MF, Chevrier J, Harley KG, Kogut K, Vedar M, Calderon N, et al. Prenatal Exposure 

to Organophosphate Pesticides and IQ in 7-Year-Old Children. Environ Health Perspectives. 

2011;119:1189-1195. 

Engel SM, Berkowitz GS, Barr DB, Teitelbaum SL, Siskind J, Meisel SJ, Wetmur JG, Wolff 

MS. Prenatal Organophosphate Metabolite and Organochlorine Levels and Performance on the 

Brazelton Neonatal Behavioral Assessment Scale in a Multiethnic Pregnancy Cohort. American 

Journal of Epidemiology. 2007;165:1397-1404. 

Engel SM, Wetmur J, Chen J, Zhu C, Barr DB, Canfield RL, Wolff MS. Prenatal Exposure to 

Organophosphates, Paraoxonase 1, and Cognitive Development in Childhood. Environmental 

Health Perspectives. 2011;119:1182-1188. 

Eskenazi B, Harley K, Bradman A, Weltzien E, Jewell NP, Barr DB, Furlong CE, Holland NT. 

Association of in Utero Organophosphate Pesticide Exposure and Fetal Growth and Length of 

Gestation in an Agricultural Population. Environmental Health Perspectives. 2004;115:792–798. 

Eskenazi B, Marks AR, Bradman A, Harley K, Barr DB, Johnson C, Morga N, Jewell NP. 

Organophosphate Pesticide Exposure and Neurodevelopment in Young Mexican-American 

Children. Environmental Health Perspectives. 2007;115:792–798. 

FIFRA Scientific Advisory Panel. (2012). Transmittal of the Meeting Minutes from the FIFRA 

Scientific Advisory Panel Meeting of April 10-12, 2012. FIFRA Scientific Advisory Panel, 

Office of Science Coordination and Policy, Office of Prevention, Pesticides and Toxic 
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Substances, U.S. Environmental Protection Agency. Washington, DC. Available: 

http://www.epa.gov/scipoly/sap/meetings/2012/041012meeting.htmll

Fortenberry, GZ, Meeker, JD, Sánchez, BN, Barr, DB, Panuwet, P, Bellinger, D, Schnaas, L, 

Solano-González, M, Ettingera, AS, Hernandez-Avila, M, Hu, H, Tellez-Rojoj, MM. Urinary 

3,5,6-trichloro-2-pyridinol (TCPY) in pregnant women from Mexico City: Distribution, temporal 

variability, and relationship with child attention and hyperactivity. International Journal of 

Hygiene and Environmental Health 217 (2014): 405–412. 

Fortenberry, GZ, Meeker, JD, Sánchez, BN, Barr, DB, Peterson, K, Bellinger, D, Schnaas, L, 

Solano-González, M, Ettinger, AS, Hernandez-Avila, M, Hu, H, Tellez-Rojoj, MM. Paraoxonase 

I polymorphisms and attention/hyperactivity in school-age children from Mexico City, Mexico. 

(2014a.) Environmental Research 132:342–349. 

Furlong, Melissa A., Engel, Stephanie M., Boyd Barr, Dana, Wolff, Mary S. Prenatal exposure to 

organophosphate pesticides and reciprocal social behavior in childhood. 2014. Environment 

International 70:125-131. 

Guodong, Ding, Pei, Wang, Ying, Tian, Jun, Zhang, Yu, Gao, Xiaojin, Wang, Rong, Shi, 

Guoquan, Wang, and Xiaoming, Shen. Organophosphate Pesticide Exposure and 

Neurodevelopment in Young Shanghai Children. Environmental Science and Technology 

46:2911-2917, 2012. 

Oulhote, Youssef and Bouchard, Maryse F. Urinary Metabolites of Organophosphate and 

Pyrethroid Pesticides and Behavioral Problems in Canadian Children. Environmental Health 

Perspectives. 121:1378-1384 (2013). 

Rauh VA, Garfinkel R, Perera FP, Andrews HF, Hoepner L, Barr DB, Whitehead R, Tang D, 

Whyatt RW. Impact of Prenatal Chlorpyrifos Exposure on Neurodevelopment in the First 3 

Years of Life Among Inner-City Children. Pediatrics. 2006;18(6): 1835-1859. 

Rauh V, Arunajadai S, Horton M, Perera F, Hoepner L, Barr DB, et al. 2011. Seven-Year 

Neurodevelopmental Scores and Prenatal Exposure to Chlorpyrifos, a Common Agricultural 

Pesticide. Environmental Health Perspectives. 2011;119:1196-1201. 

Shelton, Janie F., Geraghty, Estella M., Tancredi, Daniel J., Delwiche, Lora D., Schmidt, 

Rebecca J., Ritz, Beate, Hansen, Robin L., and Hertz-Picciotto, Irva. Neurodevelopmental 

disorders and prenatal residential proximity to agricultural pesticides: The CHARGE Study. 

Environmental Health Perspectives 122:1103–1109, 2014. 

U.S. Environmental Protection Agency. (2008). Science Issue Paper: Chlorpyrifos Hazard and 

Dose Response Characterization. 

http://www.epa.gov/scipoly/sap/meetings/2008/091608_mtg.htm 
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U.S. Environmental Protection Agency. (2012). Draft Issue Paper: Scientific Issues Concerning 

Health Effects of Chlorpyrifos. http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP2012-0040-0002 

Young JG, Eskenazi B, Gladstone EA, Bradman A, Pedersen L, Johnson C, Barr DB, Furlong 

CE, Holland NT. Association Between In Utero Organophosphate Pesticide Exposure and 

Abnormal Reflexes in Neonates. NeuroToxicology. 2005;26:199–209. 

Zhang, Ying, Han, Song, Liang, Duohong, Shi, Xinzhu, Wang, Fengzhi, Wei Liu, Zhang, Li, 

Chen, Lixin, Gu, Yingzi, Tian, Ying. Prenatal exposure to organophosphate pesticides and 

neurobehavioral development of neonates: A birth cohort study in Shenyang, China. PlosOne 

47:80–85, 2014. 
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Appendix A. Toxicology Profile and Executive Summaries 

A.1 Toxicology Data Requirements

The requirements (40 CFR 158.340) for food use for bensulide are in Table 1. Use of the new guideline numbers 

does not imply that the new (1998) guideline protocols were used. 

Study Technical

Required Satisfied

870.1100 Acute Oral Toxicity ....................................................... 

870.1200 Acute Dermal Toxicity .................................................. 

870.1300 Acute Inhalation Toxicity .............................................. 

870.2400 Acute Eye Irritation ....................................................... 

870.2500 Acute Dermal Irritation ................................................. 

870.2600 Skin Sensitization .......................................................... 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

870.3100 90-Day Oral Toxicity in Rodents .................................. 

870.3150 90-Day Oral Toxicity in Non-rodents ............................ 

870.3200 21/28-Day Dermal Toxicity ........................................... 

870.3250 90-Day Dermal Toxicity ................................................ 

870.3465 90-Day Inhalation Toxicity ........................................... 

yes 

yes 

yes 

no 

yes 

yes 

yes 

yes 

- 

no 

870.3700a Prenatal Developmental Toxicity in Rodents ................ 

870.3700b Prenatal Developmental Toxicity in Non-rodents ......... 

870.3800 Reproduction and Fertility Effects ................................. 

yes 

yes 

yes 

yes 

yes 

yes 

870.4100a Chronic Toxicity in Rodents .......................................... 

870.4100b Chronic Toxicity in Non-rodents ................................... 

870.4200a Carcinogenicity in Rats .................................................. 

870.4200b Carcinogenicity in Mice ................................................ 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

870.5100 Mutagenicity—Bacterial Reverse Mutation Test .......... 

870.5300 Mutagenicity—Mammalian Cell Gene Mutation Test .. 

870.5375 Mutagenicity—Structural Chromosomal Aberrations ... 

870.5385 Mutagenicity—Mammalian Bone Marrow Chromosomal Aberration Test 

870.5395 Mutagenicity—Mammalian Erythrocyte Micronucleus Test 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

yes a 

yes 

870.6100 28-Day Delayed Neurotoxicity in Hens......................... 

870.6200a Acute Neurotoxicity Screening Battery in Rats ............. 

870.6200b 90-Day Neurotoxicity Screening Battery in Rats .......... 

870.6300 Developmental Neurotoxicity ........................................ 

yes 

yes 

yes 

yes 

yes 

yes 

yes b 

yes b

870.7800 Immunotoxicity 

Special Studies 

Comparative Cholinesterase in Rats ........................... 

yes 

yes 

yes c

yes 

a Although there were no guideline 870.5385 studies submitted, there are mutagenicity studies which evaluate 

both somatic and germinal cells, which is considered sufficient to satisfy CFR requirements. 

b Study not required by HASPOC (Leshin, 2015, TXR # 0057280). 

c (van Alstine, 2013, TXR # 0056738) 
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A.2 Summary of OPP’s ChE Policy & Use of BMD Modeling 

OPP’s ChE policy (USEPA, 200015) describes the manner in which ChE data are used in human 

health risk assessment. The following text provides a brief summary of that document to provide 

context to points of departure selected. 

ChEI can be inhibited in the central or peripheral nervous tissue. Measurements of AChE or 

ChE inhibition in peripheral tissues (e.g., liver, diaphragm, heart, lung, etc.) are rare. 

Experimental laboratory studies generally measure brain (central) and blood (plasma and RBC) 

ChE. Blood measures do not represent the target tissue, but are instead used as surrogate 

measures for peripheral toxicity in studies with laboratory animals or for peripheral and/or 

central toxicity in humans. In addition, RBC measures represent AChE, whereas plasma 

measures are predominately butyryl-ChE (BuChE). RBC AChE data are expected to provide a 

better representation of the inhibition of AChE in target tissues. As part of the dose response 

assessment, evaluations of neurobehavior and clinical signs are performed to consider the dose 

response linkage between ChEI and apical outcomes. 

Refinements to OPP’s use of ChE data have come in the implementation of BMD approaches in 

dose response assessment. Beginning with the OP CRA, OPP has increased its use of BMD 

modeling to derive PODs for AChE inhibiting compounds. Most often, the decreasing 

exponential empirical model has been used. 

OPP does have not a defined benchmark response (BMR) for OPs. However, the 10% level has 

been used in the majority of dose response analyses conducted to date. This 10% level 

represents a 10% reduction in AChE activity (i.e., inhibition) compared to background (i.e., 

controls). Specifically, the BMD10 is the estimated dose where ChE is inhibited by 10% 

compared to background. The BMDL10 is the lower confidence bound on the BMD10. 

The use of the 10% BMR is derived from a combination of statistical and biological 

considerations. A power analysis was conducted by the Office of Research and Development 

(ORD) on over 100 brain AChE datasets across more than 25 OPs as part of the OP CRA 

(USEPA, 2002). This analysis demonstrated that 10% is a level that can be reliably measured in 

the majority of rat toxicity studies. In addition, the 10% level is generally at or near the limit of 

sensitivity for discerning a statistically significant decrease in ChE activity in the brain 

compartment and is a response level close to the background brain ChE level. With respect to 

biological considerations, a change in 10% brain ChEI is protective for downstream clinical 

signs and apical neurotoxic outcomes. With respect to RBC ChEI, these data tend to be more 

variable than brain AChE data. OPP begins its BMD analyses using the 10% BMR for RBC 

ChEI, but BMRs up to 20% could be considered on a case by case basis as long as such PODs 

are protective for brain ChEI, potential peripheral inhibition, and clinical signs of neurotoxicity. 

 

15 USEPA (2000) Office of Pesticide Programs, US Environmental Protection Agency, Washington DC 20460. 

August 18, 2000 Office of Pesticide Programs Science Policy of The Use of Data on Cholinesterase Inhibition for 

Risk Assessments of Organophosphorous and Carbamate Pesticides.
Bensulide Human Health Risk Assessment DP No. D428598 

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The results of the BMD modeling for the bensulide are as follows: 

Table A.2.1. Results of BMD Modeling (mg/kg) for Brain and RBC ChE Data on Bensulide, Acute 

Oral Dosing Studies in Rats. 

Test

Age 

Sex 

Brain 

BMD10

Brain 

BMDL10

RBC 

BMD10

RBC 

BMDL10

MRID 49433502 

Acute CCA 

Adult 

Male 79.94 63.10 79.11 55.92 

MRID 49433502 

Acute CCA 

Adult 

Female 46.39 36.88 27.21 21.53 

MRID 49433502 

Acute CCA 

PND 11 

Male 26.04 16.67 17.74 11.61 

MRID 49433502 

Acute CCA 

PND 11 

Female 28.90 21.30 16.23 11.24 

MRID 43195901 

Acute Neurotoxicity 

Adult 

Male 149.72 95.46 QF 

MRID 43195901 

Acute Neurotoxicity 

Adult 

Female QF 37.29 30.30 

CCA = Comparative Cholinesterase Assay 

QF = Questionable fit, all statistical tests of fit were not passed and/or high variance was observed in the dose 

groups 

 
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Table A.2.2. Results of BMD Modeling (mg/kg/day) for Brain and RBC ChE Data on Bensulide, 

Repeated Oral Dosing Studies in Rats. 

Test (Dosing Days)

Age 

Sex 

Brain 

BMD10

Brain 

BMDL10

RBC 

BMD10

RBC 

BMDL10

MRID 44161101 

Chronic/Carc, 103W 

Adult 

Male NE NE 

MRID 44161101 

Chronic/Carc, 103W 

Adult 

Female NE 11.68 7.83 

MRID 44161101 

Chronic/Carc, 77W 

Adult 

Male NE NE 

MRID 44161101 

Chronic/Carc, 77W 

Adult 

Female NE 6.63 4.53 

MRID 44161101 

Chronic/Carc, 51W 

Adult 

Male 29.58 16.20 NF 

MRID 44161101 

Chronic/Carc, 51W 

Adult 

Female 26.26 14.97 4.19 3.77 

MRID 44161101 

Chronic/Carc, 25W 

Adult 

Male 25.68 18.15 4.51 2.77 

MRID 44161101 

Chronic/Carc, 25W 

Adult 

Female NF 7.26 5.16 

MRID 43919601 

Subchronic rat, 13W 

Adult 

Male NE NE 

MRID 43919601 

Subchronic rat, 13W 

Adult 

Female NE 9.53 7.19 

MRID 49454001 

Gestational CCA, 13D Dam 23.52 21.54 12.01 10.03 

MRID 49454001 

Gestational CCA, 13D 

Fetus 

Male 27.08 21.92 22.34 17.19 

MRID 49454001 

Gestational CCA, 13D 

Fetus 

Female 31.37 24.38 21.82 17.40 

MRID 49466201 

Repeated-Dose CCA, 10D 

Adult 

Male NT NT 

MRID 49466201 

Repeated-Dose CCA, 10D 

Adult 

Female 31.04 25.87 18.66 15.92 

MRID 49466201 

Repeated-Dose CCA, 10D 

PND 11 

Male 19.60 15.67 7.91 5.92 

MRID 49466201 

Repeated-Dose CCA, 10D 

PND 11 

Female 17.30 12.87 12.30 9.05 

MRID 43948701 

2 gen repro 

F0 

Male QF 197.77 132.68 

MRID 43948701 

2 gen repro 

F0 

Female 312.99 83.08 114.32 91.53 

MRID 43948701 

2 gen repro 

F1 

Male QF QF 

MRID 43948701 

2 gen repro 

F1 

Female 466.83 214.75 QF 

CCA = comparative cholinesterase assay 

NF = No model fit the data well 
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NE = Not evaluated 

NT = Not tested 

NDR = No dose response found upon analysis 

NA = Result considered not accurate 

QF = Questionable fit, all statistical tests of fit were not passed and/or high variance was observed in the dose groups

Tox = Toxicity

Carc = Carcinogenicity 

Chronic dog: no apparent dose response for male and female brain ChEI, and no fit due to too 

much variance for male and female RBC ChEI.

Dermal toxicity: no apparent dose response (did not model) for both sexes and both brain and 

RBC ChEI. The LOAEL was not established in MRID 42162002 (NOAEL = 1000 mg/kg/day). 

The LOAEL was 500 mg/kg/day in MRIDs 44801101 and 44809401 based on decreased plasma 

and brain ChE (no RBC ChEI), and the NOAEL = 50 mg/kg/day. 

Bensulide Toxicity Profiles follow: 

Table A.2.3. Acute Toxicity Profile – Bensulide

Guideline 

No. Study Type MRID # Results Toxicity 

Category

870.1100 Acute oral [rat] 00097921 

92005011 

LD50 = 360 mg/kg (M) 

LD50 = 270 mg/kg (F) II 

870.1200 Acute dermal [rat] 41597501 LD50 ≥ 2000 mg/kg III 

870.1200 Acute dermal [rabbit] 00097921 LD50 > 5000 mg/kg IV 

870.1300 Acute inhalation [rat] 41646201 LC50 > 1.75 mg/L III 

870.2400 Acute eye irritation [rabbit] 41597502 mild irritant III 

870.2500 Acute dermal irritation [rabbit] 00097921 

92005012 mild irritant IV 

870.2600 Dermal sensitization [guinea pig] 00160075 not a sensitizer NA 

Table A.2.4. Subchronic, Chronic, and Other Toxicity Profile – Bensulide

Guideline No./Study 

Type

MRID No. (year)/ 

TXR #/ Classification 

/Doses 

Results

870.3100a 

90-Day oral toxicity 

rodents - rat 

43919601 (1992) 

TXR 0012289 

Acceptable, guideline 

0, 5, 15, 45, or 100 

mg/kg/day 

NOAEL = 5 mg/kg/day 

LOAEL = 15 mg/kg/day based on decreased plasma ChE in 

both sexes and brain ChE in males 

At 45 and 100 mg/kg/day, decreased RBC and brain ChE in 

both sexes and liver vacuolation in males. 

At 100 mg/kg/day, increased ALT in both sexes, fatty 

microvesicles in males, and liver weight in males 

870.3100b 

90-Day oral toxicity 

rodents - mouse 

44161104 (1993) 

TXR 0012289 

Acceptable, guideline 

0, 30, 100, 300, or 

1000 mg/kg/day 

NOAEL = 300 mg/kg/day 

LOAEL = 1000 mg/kg/day based on decreased body weight 

in males, increased liver weight, liver lobulation hepatocyte 

hypertrophy in both sexes, liver enlargement in males, 

decreased ovarian and spleen weights in females 
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Table A.2.4. Subchronic, Chronic, and Other Toxicity Profile – Bensulide

Guideline No./Study 

Type

MRID No. (year)/ 

TXR #/ Classification 

/Doses 

Results

870.3150b 

90-Day oral toxicity 

non-rodents - dogs 

44052703 (2016) 

TXR 0057338 

Acceptable, guideline 

0, 1, 3, 10, or 30 

mg/kg/day 

NOAEL = 10 mg/kg/day 

LOAEL = 30 mg/kg/day based conservatively on increased 

liver weight, increased incidence of liver lipid deposits, and 

increased activated partial thromboplastin times 

870.3200 

21-Day dermal toxicity 

with parent - rat 

42162002 (1991) 

TXR 0009325 

Acceptable, guideline 

0, 10, 100, or 1000 

mg/kg/day 

NOAEL ≥ 1000 mg/kg/day 

LOAEL was not established 

870.3200 

21-Day dermal toxicity 

with parent - rat 

44801101 and 

44809401 (1999) 

TXR 0013532 

Acceptable, nonguideline 

0, 30, 50, or 500 

mg/kg/day (6 h/d, 21 d) 

NOAEL = 50 mg/kg/day 

LOAEL = 500 mg/kg/day based on decreased plasma and 

brain ChE 

Note: No effect was noted on RBC ChE in either sex at any 

time point. 

870.3700a 

Prenatal developmental 

- rat 

00146585 (1985) 

92005018 (1990) 

TXR 0012289 

Acceptable, guideline 

0, 5.5, 23.0, or 95.0 

mg/kg/day 

Maternal NOAEL = 5.5 mg/kg/day 

Maternal LOAEL = 23.0 mg/kg/day based on decreased 

plasma ChE 

In the 95.0 mg/kg/day dams, tremor and decreased BWG, FC, 

whole and corrected (uterine wt) BW were noted. 

Developmental NOAEL ≥ 95.0 mg/kg/day 

Developmental LOAEL was not established 

870.3700b 

Prenatal developmental 

- rabbit 

00152845 (1985) 

92005019 (1990) 

TXR 0012289 

Acceptable, guideline 

0, 5, 20, or 80 

mg/kg/day 

Maternal NOAEL = 20 mg/kg/day 

Maternal LOAEL = 80 mg/kg/day based on decreased body 

weights and weight loss during the treatment interval 

Developmental NOAEL ≥ 80 mg/kg/day 

Developmental LOAEL was not established 
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Table A.2.4. Subchronic, Chronic, and Other Toxicity Profile – Bensulide

Guideline No./Study 

Type

MRID No. (year)/ 

TXR #/ Classification 

/Doses 

Results

870.3800 

Reproduction and 

fertility effects with 

parent - rat 

43948701 (1996) 

TXR 0012289 

Acceptable, guideline 

Pre-mating doses: 

P male: 0, 2.0, 12.3, or 

68.2 mg/kg/day 

P female: 0, 2.3, 13.2, 

or 80.8 mg/kg/day 

F1 male: 2.3, 14.0, or 

86.5 mg/kg/day 

F1 female: 2.6, 15.4, or 

93.2 mg/kg/day

Parental/Systemic NOAEL ≥ 68.2 mg/kg/day 

Parental/Systemic LOAEL was not established 

ChE inhibition NOAEL was not established 

ChE inhibition LOAEL = 2.3 mg/kg/day based on plasma 

ChE inhibition in the F1 males 

In the mid and high dose P males and females, plasma ChE 

was decreased. In the high dose P males and females, RBC 

ChE was decreased, and brain ChE was also decreased in 

females. At the mid and high dose, decreased RBC ChE was 

noted in F1 males, and plasma ChE was decreased in F1 

females. In the high dose F1 females, RBC and brain ChE 

were decreased. In the high dose P males and females, low 

fertility rates were noted. 

Reproductive NOAEL ≥ 68.2 mg/kg/day 

Reproductive LOAEL was not established 

Offspring NOAEL = 15.4 mg/kg/day 

Offspring LOAEL = 93.2 mg/kg/day based on reduced F2 pup 

survival 

ChE not measured in pups. 

870.4100b 

Chronic toxicity (1 

year) - dogs 

44066401 (2016) 

TXR 0057338 

Acceptable, guideline 

M & F: 0, 0.5, 4, or 30 

mg/kg/day 

NOAEL = 4 mg/kg/day 

LOAEL = 30 mg/kg/day based on the RBC cholinesterase 

inhibition and mild indications of hepatotoxicity (Kupffer-cell 

accumulation, inflammation, and fatty 

870.4100b 

Chronic toxicity (1 

year) - dogs 

41112301 (1989) 

92005016 (1990) 

TXR 0008369 

Acceptable, guideline 

M & F: 0, 2, 10, or 50 

mg/kg/day 

NOAEL = 10 mg/kg/day 

LOAEL = 50 mg/kg/day based on increased mortality, clinical 

signs of toxicity, decreased body weight and food 

consumption, discolored liver, and several microscopic 

lesions (fibrosis and chronic inflammation of the thymus, 

erythroid/myeloid bone marrow depletion, inflammation 

and/or degeneration of the skeletal muscle, and liver changes) 

870.4200b 

Carcinogenicity with 

parent - mice 

44161105 (1996) 

TXR 0012289 

Acceptable, guideline 

M & F: 0, 1, 50, or 200 

mg/kg/day 

NOAEL = 1 mg/kg/day 

LOAEL = 50 mg/kg/day based on decreased plasma and 

erythrocyte ChE in both sexes, brain ChE in females, and 

body weight gain in males 

At 200 mg/kg/day, increased liver weight and liver pathology 

(clear cell foci, hepatocyte pigmentation, Kupffer sell 

pigmentation, and atypia) 

Carcinogenic potential is considered negative. 
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Table A.2.4. Subchronic, Chronic, and Other Toxicity Profile – Bensulide

Guideline No./Study 

Type

MRID No. (year)/ 

TXR #/ Classification 

/Doses 

Results

870.4300 

Combined chronic 

toxicity/Carcinogenicity 

- rats 

43919602 (1995) 

44161101 (1996) 

TXR 0012289 

Acceptable, guideline 

M & F: 0, 1, 15, or 60 

mg/kg/day 

NOAEL = 1 mg/kg/day 

LOAEL = 15 mg/kg/day based on decreased plasma and 

erythrocytes ChE in both sexes 

Carcinogenic potential is considered negative. 

870.5100 

Bacterial reverse 

mutation test with 

parent 

00153493 (1984) 

00153495 (1984) 

92005021 (1990) 

TXR 0012289 

Acceptable, guideline 

0, 0.005, 0.014, 0.041, 

0.123, 0.370, 1.111, 

3.333, 10, 25, or 50 

μL/plate (TA100); 0, 

0.037, 0.111, 0.333, 1, 

or 3 μL/plate (TA98, 

TA1535, and TA1537) 

There was no evidence of induced mutant colonies over 

background in Salmonella typhimurium strains TA98, TA100, 

TA1535, and TA1537. 

870.5300 

Mouse lymphoma 

cell/mammalian 

activation gene forward 

mutation assay (TK 

locus) with parent. 

43273901 (1994) 

TXR 0011409 

Acceptable, guideline 

0, 8,14, 16, 21, 24, 28, 

32, 35, 40, or 42 

μg/mL (-S9); 0, 16, 24, 

28, 32, 35, 40, 42, 48, 

49, or 56 μg/plate 

(+S9) 

There was no evidence of induced forward mutation at the TK 

locus. 

870.5375

In vitro mammalian 

cytogenetics 

(Chromosomal 

aberration assay in 

human peripheral 

blood) 

41902601 (1990) 

TXR 0009077 

Unacceptable, 

guideline (upgradable) 

0, 5, 40, 60 or 80 

Bensulide was not clastogenic under conditions of the assay. 

Study deficiencies included: lack of information concerning: 

stability of test compound; criteria for assessing chromosomal 

aberrations; level of p value used in determining statistical 

significance; and potential for bensulide-induced delay of cell 

cycle. 

870.5395 

In vivo mouse 

micronucleus 

41902602 (1990) 

TXR 0010229; 

0009077 

Acceptable, guideline 

M & F: 0, 250, or 400 

mg/kg/day 

There was no significant increase in the frequency of 

micronucleated polychromatic erythrocytes in bone marrow. 

870.6100 

Delayed neurotoxicity 

(Acute) - hen 

43334302 (1994) 

43306301 (1994) 

TXR 0012289 

Acceptable, guideline 

M: 0 or 2262 mg/kg 

Bensulide did not induce acute delayed neurotoxicity in the 

hen at the limit dose. 
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Table A.2.4. Subchronic, Chronic, and Other Toxicity Profile – Bensulide

Guideline No./Study 

Type

MRID No. (year)/ 

TXR #/ Classification 

/Doses 

Results

870.6200a 

Acute neurotoxicity - rat 

43195901 (1994) 

TXR 0012289 

Acceptable, guideline 

M: 0, 30, 100, or 300 

mg/kg 

F: 0, 15, 50, or 150 

NOAEL = 100 mg/kg/day 

LOAEL = 150 mg/kg/day based on decreased plasma, RBC, 

and brain ChE in females and minimal, clinical signs 

consistent with ChE inhibition in females 

870.6200b 

Subchronic 

neurotoxicity screening 

battery - rat 

NA NA 

870.6300 

Developmental 

neurotoxicity study with 

parent 

NA NA 

870.7485 

Metabolism and 

pharmacokinetics with 

parent - rat 

42007901 (1991) 

42007902 (1991) 

42007903 (1991) 

42007904 (1991) 

42225401 (1992) 

TXR 0009491; 

0012289; 0012948 

Acceptable, guideline 

single 1 mg/kg dose, 

1 mg/kg/day for 15 

consecutive days, 

single 100 mg/kg dose, 

50 mg/kg for 4 

consecutive days 

In a rat metabolism study with 14C-labeled bensulide, 

Sprague-Dawley rats received doses of 1 mg/kg (single, low 

dose), 1 mg/kg × 15 days (repeated low dose), 50 mg/kg/day 

× 4 consecutive days (group used for metabolite isolation), 

and 100 mg/kg (single, high dose). Bensulide was excreted 

primarily in the urine, with the majority of the dose eliminated 

within 24 hours. Fecal excretion also occurred; biliary 

excretion was minimal. The highest concentration of 

radioactivity was found in whole blood, associated with the 

cellular component. Whole body auto radiography showed a 

much higher level of radioactivity remaining in males after 24 

hours than in females. Four metabolites were identified. One 

was the primary urinary metabolite and the other identified 

metabolites were found in the urine. The proposed formation 

of two metabolites involved the cleavage of the 

PO2[CH(CH3)2]2 moiety of bensulide, followed by 

methylation and oxidation of the sulphur atom. Conjugation 

with glycine or carboxylation and oxidative desulphuration is 

proposed to lead to the other two identified metabolites. 

870.7600 

Dermal penetration-rat 

NA NA 

870.7800 

Immunotoxicity - mice 

48377701 (2011) 

48623701 (2011) 

TXR 0055808; 

0056257 

Unacceptable, 

guideline 

0, 50, 200, or 800 

mg/kg/day 

Increased mortality was observed at 800 mg/kg/day. 

Problems with the conduct of the TDAR made confident 

interpretation of the results impossible. 

HASPOC waived this study (van Alstine, 2013, TXR # 

0056738) 
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Table A.2.4. Subchronic, Chronic, and Other Toxicity Profile – Bensulide

Guideline No./Study 

Type

MRID No. (year)/ 

TXR #/ Classification 

/Doses 

Results

Non-Guideline 

Comparative 

cholinesterase assay – 

rat 

49433502 (2014) 

49466201 (2014) 

49454001 (2014) 

Acceptable, nonguideline 

Animals were treated 

with a single gavage 

dose in corn oil at 0, 

50, 100, 150, and 200 

mg/kg/day in the adult 

males, 0, 25, 50, 100, 

and 150 mg/kg/day in 

adult females, and 0, 

20, 40, 60, and 100 

mg/kg/day in the pups 

Animals were treated 

once daily for 10 

consecutive days at 0, 

15, 25, 50, and 75 

mg/kg/day in the adults 

and 0, 5, 10, 20, 40, 

and 60 mg/kg/day in 

the pups. 

Dams were treated 

once daily during GD 

6-20 (inclusive) at 0, 

15, 30, 60, and 90 

mg/kg/day 

In the acute study, the LOAEL in adults was 50 mg/kg/day 

based on ChE inhibition in the RBC and brain of females. 

The NOAEL was 25 mg/kg/day. The LOAEL in the PND 11 

pups was 40 mg/kg/day based on ChE inhibition in the RBC 

and brain of males and females. The NOAEL was 20 

mg/kg/day. 

In the repeated dose study, the LOAEL in adults was 25 

mg/kg/day based on ChE inhibition in the RBC of females 

(only sex tested). The NOAEL was 15 mg/kg/day. The 

LOAEL in the PND 11 pups was 10 mg/kg/day based on ChE 

inhibition in the RBC of males. The NOAEL was 5 

mg/kg/day. 

In the gestational study, the LOAEL in dams and fetuses was 

30 mg/kg/day based on ChE inhibition in RBC and brain. The 

NOAEL was 15 mg/kg/day. 

A.3 Executive Summaries 

A.3.1 Subchronic Toxicity

 870.3100 90-Day Oral Toxicity - Rat

In a subchronic toxicity study (MRID 43919601), male and female Sprague-Dawley 

rats (10/sex/dose) were given bensulide (92.4% a.i.) in the diet for 13 weeks at doses of 

0, 5, 15, 45, or 100 mg/kg/day. 

Significantly decreased body weight gains (p<0.01, 19%) were observed for male rats 

at 100 mg/kg/day. Although not significant, body weight gains for female rats were 12, 
Bensulide Human Health Risk Assessment DP No. D428598 

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11, and 14% lower than controls at 15, 45, and 100 mg/kg/day, respectively. Food 

consumption appeared not affected by treatment. Overall food efficiency was 

decreased in males at 100 mg/kg/day. 

Significantly increased alanine amino-transferase levels were observed at 45 mg/kg/day 

(87% increase in males; 48%, females) and 100 mg/kg/day (145%, males and 90%, 

females). Dose-related inhibition of ChE activity occurred in both sexes. Relative to 

controls, plasma ChE decreases were 28, 54, and 62% (males) at 15, 45, and 100 

mg/kg/day, respectively, and 19, 47, 84, and 90% (females) at 5, 15, 45, and 100 

mg/kg/day, respectively. Red blood cell ChE decreases were 47 and 59% (males) and 

38 and 66% (females) at 45 and 100 mg/kg, respectively. Brain ChE decreases were 18 

and 43% (males) at 15 and 100 mg/kg/day, respectively, and 28 and 58% (females) at 45 

and 100 mg/kg, respectively. Increased relative liver weights were observed in males 

(17%, p<0.01) and females (19%, p<0.001) at 100 mg/kg/day. The hepatic toxicity was 

corroborated by mild histological changes in the liver in males (fatty microvesicles at 

100 mg/kg/day; vacuolation at 45 and 100 mg/kg/day). 

Under the conditions of this study, the NOAEL is 5 mg/kg/day; the LOAEL is 15 

mg/kg/day, based on decreased plasma ChE activity in both sexes, decreased brain ChE 

activity in males, and an equivocal reduction in body weight gain in females. 

This subchronic dietary toxicity study in rats is classified as Acceptable/Guideline and 

satisfies the guideline requirements (§82-1a) for a subchronic toxicity study in the rat. 

 870.3100 90-Day Oral Toxicity - Mouse

Reviewed as the dose-selection rational for the chronic toxicity study (MRID 44161105). 

The rational for dose selection was based on results from 0 previously conducted 13-

week subchronic study in which 10 CD-1 mice/sex/dose were dosed with bensulide (92.4 

±0-5%; Lot # CBI 0801) at 0, 30, 100, 300, or 1000 mg/kg/day (MRID 44161104). All 

animals, including premature decedents were necropsied. After necropsy, the kidneys and 

lungs of the controls and high-dose animals and the livers of all the animals were 

examined histologically. The brain, heart, kidneys, liver, lungs, ovaries, spleen, and testes 

were weighed. Mortality, clinical signs, and water consumption were not affected by 

treatment with bensulide. There were no treatment related findings in the 30 mg/kg/day 

animals. The following treatment related findings were observed in the 1000 mg/kg/day 

animals compared to concurrent controls: decreased mean body weight gain in females 

(↓50%; p<0.01) and decreased body weight in males (↓1 g; p<0.001); decreased overall 

(weeks 1-13) feed consumption in both sexes (↓9-10%); increased liver weight (↑72-

90%; p<0.001) and increase in liver lobulation in both sexes; liver enlargement in males; 

increase in the incidence and severity of hepatocyte hypertrophy in both sexes; and a 

decrease in ovarian (↓43%; p<0.001) and spleen (↓26%; p<0.05) weights in females. 

Findings in the 100 and 300 mg/kg/day dose groups consisted of a reduction in body 

weight gain in the males (↓27 and 55%; p<0.001, respectively), an increase in liver 
Bensulide Human Health Risk Assessment DP No. D428598 

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weights in both sexes (↑19-42%; p<0.01 and <0.001), and an increase in the incidence 

and/or the severity of hepatocyte hypertrophy in the animals of both groups. 

 870.3150 90-Day Oral Toxicity – Dog 

In a 13-week subchronic toxicity study (MRID 44052703), bensulide (92.4% a.i., Lot 

#CBI 0801) was administered via the diet to four dogs/sex/group at dose levels of 0, 1, 

3, 10, or 30 mg/kg/day for 13 weeks. 

No treatment-related effects were noted on survival, clinical signs, body weights, food 

consumption, ophthalmology findings, clinical chemistry (including RBC and brain 

cholinesterase but excluding plasma cholinesterase), urinalysis, and necropsy. 

At 30 mg/kg/day, there was slight evidence for liver toxicity. Adjusted (for terminal body 

weight covariate) liver weight means were decreased by 19-22% in both sexes. There was 

no statistical difference in liver weights at this dose in the chronic toxicity study in dogs. 

Additionally, periportal lipid deposits were noted in the liver of 7/8 rats, and the eighth 

rat (a female) had centrilobular lipid deposits. The severity was reported as only very 

mild or mild. The increase in weight was considered slight, and the biological 

significance of the lipid deposits was unclear, but likely negligible considering the 

severity. However, liver findings following bensulide treatment have been reported in 

rats and mice, as well as in the chronic toxicity study in dogs. Activated partial 

thromboplastin times were prolonged in both sexes in the 30 mg/kg/day treatment group 

at 6 (21-35%) and 13 (33-50%) weeks; this parameter was not evaluated in the chronic 

toxicity study in dogs. The liver effects and hematological effect were together 

considered very conservatively to be adverse. 

The LOAEL was 30 mg/kg/day, based conservatively on increased liver weight, 

increased incidence of liver lipid deposits, and increased activated partial 

thromboplastin times. The NOAEL is 10 mg/kg/day.

This study is classified acceptable, guideline and satisfies the guideline requirements 

(OCSPP 870.3150; OECD 409) for a 90-day oral toxicity study in dogs. 

 870.3200 21/28-Day Dermal Toxicity – Rat

In a 21-day dermal toxicity study (MRID 42162002), male and female specific 

pathogen-free Wistar-derived albino rats (Alpk:APfSD strain; 5/sex/dose; 6-8 weeks old) 

were dermally treated over a 5 cm x 10 cm area of clipped dorso-lumbar skin with 

bensulide technical (92.7% a.i.) at dose levels of 0 (sham control), 10, 100, and 1000 

mg/kg/day (limit test dose). Dosing occurred 21 times over a period of 30 days (five 

days/week). Following each dosing, the application site was covered with an occlusive 

dressing (gauze patch, a patch of plastic film secured by adhesive bandages, and two 

pieces of 2.5 cm-wide PVC tape wrapped around the animals) for approximately 6 

hours. 
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After each 6-hour exposure period, the dressings were removed and the application sites 

washed with warm water. On dosing days, animals were fitted with Elizabethan collars 

to prevent test substance ingestion. Rats were observed for clinical signs and dermal 

irritation prior to dosing, after each removal of dressings, and at least once daily during 

non- dosing days. They were weighed daily, and food consumption was recorded twice 

weekly. At study termination, cardiac blood samples were collected shortly after animal 

sacrifice for hematological and clinical chemistry determinations. Gross necropsies 

were conducted, the standard set of organs were fixed for potential histopathology, and 

the following organs were also weighed: adrenals, brain, kidneys, liver, and testes 

(males). Only the kidneys of all animals, and the treated and untreated skins and livers 

of the control (0 mg/kg/day) and high-dose (1000 mg/kg/day) were examined 

histologically. 

There were no deaths, compound-related clinical signs, or significant changes in body 

weight or food consumption in any group. A small incidence of dermal trauma was 

apparently caused by the bandages. No abnormal hematology was seen, and the only 

clinical chemistry anomaly was a 43% decrease in plasma triglycerides in the high-dose 

(1000 mg/kg/day) males compared to controls; females were not affected. In the 

absence of other findings, this decrease is of unknown biological significance. There 

were no dose-related gross lesions or organ weight changes. Some scabbing of treated 

and untreated skin, due to bandage trauma, was observed in all groups. This observation 

correlates with several histopathologic findings of slight to minimal acanthosis, 

parakeratosis, and inflammatory infiltration in treated and untreated skin. A number of 

minimal to slight renal lesions were observed, but they are not clinically significant and 

may have represented artifacts. Therefore, the NOAEL is > 1000 mg/kg/day (limit 

dose), based on the lack of any observed toxicity, and the LOAEL was not determined. 

Although cholinesterase activity was not determined, this study was classified as 

Acceptable/Guideline and satisfies the Guideline requirement for a 21-day dermal 

toxicity study (82-2) in the rat. 

In a special 21-day dermal toxicity study (MRIDs 44801101 and 44809401), groups of 

Charles River CD rats (10/sex/dose) were dermally applied Bensulide technical (92.1%) 

at dose levels of 0, 30, 50, and 500 mg/kg for 6 hrs/day for 21 days. The test chemical 

did not produce treatment-related clinical signs, mortality, or changes in body weight 

and food consumption. Clinical chemistry and hematology parameters were not 

measured. Urinalysis, and organ weights were not determined. However, these 

parameters were not significantly affected in a previous 21-day dermal toxicity study in 

rats which were dermally treated up to 1000 mg/kg (MRID 42162002; Tox. Doc. No. 

009325). 

Bensulide at 500 mg/kg produced statistically significant decreases (p<0.01) in plasma 

cholinesterase (PChE) activity in both males and females on days 7, 14, and 22; the 

decrease (-31% in males & -55% in females) was particularly marked at the end of the 

study (day 22). In addition, the inhibition of PChE appeared to increase with the 
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increased time of treatment. Plasma cholinesterase inhibition was also seen in 50 mg/kg 

females, but it was not statistically significant. Bensulide at 500 mg/kg also 

significantly (p<0.05) inhibited brain stem ChE activity in both males and females, but it 

had no effect on the ChE activity in cerebellum and cerebral cortex. In this study, RBC 

ChE activity was not affected by bensulide. 

Therefore, under the conditions of this dermal toxicity study, the LOAEL for ChE 

inhibition was 500 mg/kg based on significant inhibition of both brain and PChE 

activity, and the NOAEL was 50 mg/kg. 

The study was classified as Acceptable/non-guideline because this was a special study 

conducted to obtain information on the potential of bensulide to inhibit ChE activity in 

plasma, RBC, and brain. 

 870.3465 90-Day Inhalation – Rat (Not Submitted but Required) 

A.3.2 Prenatal Developmental Toxicity

 870.3700a Prenatal Developmental Toxicity Study – Rat 

In a developmental toxicity study (MRID 00146585), bensulide technical (92.8 % a.i.) 

was administered to 25 or 26 female Sprague-Dawley rats/dose in corn oil by gavage at 

analytically determined dose levels of 0, 5.5, 23.0 or 95.0 mg/kg/day from days 6 

through 20 of gestation. 

Bensulide technical exerted no effects on maternal gross pathology, fertility, or cesarian 

parameters. The maternal systemic LOAEL is 95.0 mg/kg/day (HDT), based on 

tremors, decreased body weight (range: 93-94% of control value) on days 12, 16, and 

21 of gestation, decreased body weight gain during days 9-12 (25% control value) and 

6-21 (76% of control value) of gestation, decreased (79% of control value) feed intake 

during days 13-16 of gestation, and decreased whole and corrected (reproductive tract 

subtracted) body weights (93% and 91% of control values, respectively) and increased 

liver/body weight ratio (112% of control value) at study termination. The maternal 

systemic NOAEL is 23.0 mg/kg/day (MDT). 

The Maternal NOAEL for cholinesterase inhibition is 5.5 mg/kg/day (LDT), based on a 

48% decrease in plasma ChE activity at 23.0 mg/kg/day (LOAEL; MDT) in the absence 

of any other effects. 

The Developmental NOAEL > 95.0 mg/kg/day (HDT), based on the lack of any 

developmental effects. The developmental LOAEL > 95.0 mg/kg/day. 

This developmental toxicity study in the rat is classified Acceptable/Guideline and 

does satisfy the guideline requirement for a developmental toxicity study (§83-3a) 

in the rat. 
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 870.3700b Prenatal Developmental Toxicity Study - Rabbit

In a developmental toxicity study (MRID 00152845), inseminated New Zealand White 

rabbits, randomly assigned to one control and three treatment groups of 18 animals 

each, were administered Betasan® (bensulide technical; 92.8% a.i.) by oral gavage at 

doses of 0, 5, 20, or 80 mg/kg/day on gestation days (GD) 7-19, inclusive. 

Cesarean section examinations were performed on all surviving does on GD 29, 

followed by teratological examination of all fetuses. 

No treatment-related effects were observed in the 5 or 20 mg/kg/day groups as compared 

with controls. Three high-dose animals aborted, one each on GD 18, 27, and 28, and 

were sacrificed and necropsied. All other animals survived until scheduled sacrifice. 

Decreased defecation was observed in 3, 2, 1, and 11 animals and decreased urination 

was observed in 3, 2, 0, and 11 animals in the control, 5, 20, and 80 mg/kg/day groups, 

respectively. No other dose- or treatment-related clinical signs of toxicity were 

observed during the study. Maternal body weight gains were significantly (p ≤ 0.05 or 

0.01) less in the high-dose group as compared to the controls throughout the dosing 

interval with an overall weight loss recorded during the treatment interval. Absolute 

body weights of the high-dose animals were less than the controls beginning on GD 13 

but statistical significance (p ≤ 0.01) was reached only on GD 19. After cessation of 

treatment, does in the high-dose group showed recovery with body weight gains 

significantly (p ≤ 0.01) greater than the controls. During the dosing interval, food 

consumption by the high-dose animals was significantly (p ≤ 0.01) less than the control 

beginning on GD 10. Overall food consumption was significantly less in the high-dose 

group for the entire dosing interval (62%; p ≤ 0.01) and the entire gestation period (83%; 

p ≤ 0.05) as compared to controls. 

Therefore, the maternal toxicity NOAEL is 20 mg/kg/day and the maternal toxicity 

LOAEL is 80 mg/kg/day based on reduced body weights and weight loss during the 

treatment interval. 

There were no differences between treated and control groups for live fetuses/litter, fetal 

body weights, or fetal sex ratios. No treatment-related malformations/variations were 

observed for any external, visceral, or skeletal parameter examined of kits in the treated 

litters as compared to the control litters. There was no difference in the total number of 

litters containing fetuses with major malformations as compared to controls: 3/15, 1/15, 

0/10, and 2/10 affected in the control, 5, 20, and 80 mg/kg/day groups, respectively. 

Therefore, the developmental toxicity NOAEL is > 80 mg/kg/day and the 

developmental toxicity LOAEL was not identified. 

This developmental toxicity study in rabbits is classified as Acceptable/Guideline and 

satisfies the guideline requirement (§83-3b) for a developmental toxicity study in 

rabbits. 
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A.3.3 Reproductive Toxicity

870.3800 Reproduction and Fertility Effects – Rat 

In a two-generation reproduction study (MRID 43948701), Bensulide (92.4% a.i.; Lot 

No. CDI 0801) was administered to male and female Sprague-Dawley CD rats in the 

diet at concentrations of 0, 25, 150, or 900 ppm for two generations. Premating doses 

for the F0 males were 2.0, 12.3, and 68.2 mg/kg, respectively, and for the F0 females 

were 2.3, 13.2, and 80.8 mg/kg, respectively. Premating doses for the F1 males were 

2.3, 14.0, and 86.5 mg/kg, respectively, and for the F1 females were 2.6, 15.4, and 93.2 

mg/kg, respectively. The F0 generation contained 28 animals/sex/dose and the F1 

generation contained 24 animals/sex/dose. Animals were given test or control diet for

at least 10 weeks then mated within the same dose group. 

F1 animals were weaned on the same diet as their parents. At least 21 litters were 

produced in each generation. All animals were exposed to test material either in the 

diet or during lactation until sacrifice. 

Although several deaths occurred among treated and control groups of both generations, 

these were considered incidental to treatment. No overt treatment-related clinical signs 

of toxicity were observed in the adult animals of either sex or generation. There were 

no statistically significant differences between treated and control groups of either sex 

or generation for absolute body weights, body weight gains, food consumption, or gross 

or histopathological findings. 

Therefore, the NOAEL for systemic effects > 900 ppm (82.8 mg/kg/day; HDT) and the 

LOAEL was not determined. 

Terminal cholinesterase activity was measured in plasma, red blood cell, and brains of 

the adult animals of both generations. Baseline or pretreatment activities were not 

measured. In F0 males, plasma cholinesterase activity was significantly (p ≤ 0.01) 

reduced in the mid- and high- dose groups as compared to controls with percent 

inhibition (%I) 21 and 54%, respectively. High-dose F0 males also had significantly (p ≤

0.01) reduced RBC activity (%I = 32). Mid- and high-dose F0 females had significantly 

(p ≤ 0.01) reduced plasma activity (%I = 43 and 76, respectively) while high-dose F0 

females also had significantly (p ≤ 0.01) reduced RBC (%I = 57) and brain (%I = 68) 

activities. Plasma activity was significantly (p ≤ 0.01) reduced in all treated F1 male 

groups as compared to controls (%I = 28, 30, and 62, respectively). Mid- (p ≤ 0.05) and 

high-dose (p ≤ 0.01) F1 males also had significantly reduced RBC activity (%I = 11 and 

42, respectively). Mid- and high-dose F1 females had significantly (p ≤ 0.01) reduced 

plasma activity (%I = 47 and 80, respectively) while high-dose F1 females also had 

significantly (p ≤ 0.01) reduced RBC and brain activities (%I = 63 and 51). The 51-68% 

inhibition of brain ChE activity in females in the high-dose (900 ppm) group indicates 

that dosing was conducted at an adequately high level; higher doses would likely yield 

an unacceptable level of mortality. 
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Therefore, the LOAEL for cholinesterase inhibition is 25 ppm (2.3 mg/kg/day; LDT) 

based on inhibition of plasma enzyme activity in F1 males. The cholinesterase 

inhibition NOAEL was not identified. 

No statistically significant differences occurred for absolute body weights, body weight 

gains, or food consumption of the F0 or F1 females during gestation or lactation for any 

treated group as compared to controls. High-dose F0 males and females had low fertility 

indices with only 21 of 28 males siring litters and only 24 of 28 females becoming 

pregnant. However, this effect was not repeated in the F1 generation. There were no 

statistically significant differences between treated and control groups for number of 

litters or pups/litter during lactation of either generation. 

Survival and viability of the F1 pups was similar between treated and control groups. 

However, survival was greatly reduced in the high-dose F2 pups with overall (day 0-21) 

survival only 61%. This was due mainly to a low viability index of 74% for lactation 

days 0-4. 

Therefore, the LOAEL for reproductive toxicity is 900 ppm (93.2 mg/kg/day; HDT) 

based on reduced F2 pup survival. The corresponding NOAEL for reproductive toxicity 

is 150 ppm (15.4 mg/kg/day; MDT). 

This study is classified as Acceptable/Guideline and does satisfy the guideline 

requirement for a reproduction study (§83-4) in rats. 

A.3.4 Chronic Toxicity

 870.4100a (870.4300) Chronic Toxicity – Rat

 870.4100b Chronic Toxicity – Dog 

In a chronic toxicity study (MRID 44066401), bensulide (92.4% a.i.) was administered 

to four dogs/sex/dose by feeding at dose levels of 0, 0.5, 4, or 30 mg/kg/day for 52 

weeks. 

No treatment-related effects were noted on survival, clinical signs, body weights, food 

consumption, ophthalmology findings, urinalysis, and necropsy. 

In the 30 mg/kg/day treatment group, there was inhibition (p≤0.05) of RBC cholinesterase 

in females at Weeks 26 and 39 (↓32-39%) and in males at Week 52 (↓45%); however, 

decreases (not statistically significant) were noted in both sexes at all time points at this 

dose. No effect was clearly present on brain (pons and cerebellum) cholinesterase. 

At 30 mg/kg/day, mild effects were also noted in the liver (primarily the female). An 

increased incidence of moderate focal pigmented Kupffer-cell accumulation (positive, for 

the presence of hemosiderin [Prussian Blue stain], neutral fat and diastase resistance 

[Periodic Acid Schiff stain]) was noted in 2/4 females compared to 0/4 controls (not 
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observed in any male). Focal liver inflammation occurred at a similar incidence in the 

treated dogs compared to controls (n=4, 3 treated males vs 3 controls; 4 treated females 

vs 3 controls); however, severity was increased (2 mild treated males vs 0 controls; 3 

mild to moderate treated females vs 0 controls). The stain for fat was positive with a 

slightly increased incidence and severity in females (2/4 very mild to mild treated vs 1 

very mild control). Liver weights were increased, but were not statistically different than 

the controls. Additionally, adjusted (terminal body weight covariate) adrenal gland 

weights were increased by 30% in males; however, there was no corroborating evidence 

of an adverse effect on the adrenals. 

The LOAEL for this study is 30 mg/kg/day based on the RBC cholinesterase 

inhibition and mild indications of hepatotoxicity (Kupffer-cell accumulation, 

inflammation, and fatty). The NOAEL is 4 mg/kg/day. 

This study is classified acceptable, guideline and satisfies the guideline requirement 

(OCSPP 870.4100b; OECD 452) for a chronic toxicity study in dogs. 

 870.4100b Chronic Toxicity – Dog 

In a chronic toxicity study (MRID 41112301), bensulide (93.8% a.i.) was administered 

in the diet to five dogs/sex/dose at dose levels of 0, 2, 10, or 50 mg/kg/day for 52 

weeks. 

No treatment-related effects were noted on ophthalmology findings, urinalysis, and 

organ weights. No adverse effects were noted at 2 or 10 mg/kg/day. 

At 50 mg/kg/day, excessive mortality was noted. In this group 9/10 dogs died or were 

terminated moribund. Mortality or morbidity typically was preceded by a drastic decrease 

in food consumption for 1-4 weeks prior to death. Clinical signs included those indicative 

of cholinesterase inhibition, as well as general malaise: loss of appetite, drastic weight 

loss, excessive salivation, tarry stools, red (bloody) stools, diarrhea, hypothermia, pale 

gum and mucous membranes, lethargy, and emaciation. Several dogs exhibited diarrhea, 

emesis, and/or excessive salivation beginning during the first week of the study. The 

single surviving female in this group exhibited occasional diarrhea, tarry stools, emesis, 

and excessive salivation. Body weight decreases in the males was progressive beginning 

after 3-11 weeks of treatment with mortality occurring after 8-21 weeks. Body weight 

decreases in the females that died or were terminated early was progressive beginning 

after 7-17 weeks of treatment with mortality occurring after 13-20 weeks. Anemia (as 

evidenced by decreased erythrocytes, hematocrit, and hemoglobin) was noted in the 

males and one female. Serum glutamic-pyruvic transaminase and alkaline phosphatase 

may be increased, but results were highly variable. Livers were pale and/or discolored. 

The following findings were noted during microscopic pathology: fibrosis and chronic 

inflammation of the thymus, erythroid/myeloid bone marrow depletion, inflammation 

and/or degeneration of the skeletal muscle, and liver changes (hepatocyte hypertrophy, 

biliary proliferation/hyperplasia, inflammation, and the presence of small vacuoles in the 

hepatocytes). 
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Acetylcholinesterase was decreased in the pons but not in the cerebellum nor in the 

erythrocytes. Inhibition (p≤0.05) in the pons was 20% and 24% in males and 18% and 

19% in females at 2 and 10 mg/kg/day, respectfully. As a decrease was only noted in the 

pons (and not in the RBCs which is most sensitive in other studies) and the dosedependency was questionable, the effect on the pons was considered an equivocal finding 

The LOAEL for this study is 50 mg/kg/day based on increased mortality, clinical 

signs of toxicity, decreased body weight and food consumption, discolored liver, and 

several microscopic lesions (fibrosis and chronic inflammation of the thymus, 

erythroid/myeloid bone marrow depletion, inflammation and/or degeneration of 

the skeletal muscle, and liver changes). The NOAEL is 10 mg/kg/day. 

This study is classified acceptable, non-guideline. Excessive mortality was noted at the 

high dose, which means it does not satisfy the guideline requirement (OCSPP 

870.4100b; OECD 452) for a chronic toxicity study in dogs. However, the study was 

otherwise conducted in a valid manner and provides meaningful results. 

A.3.5 Carcinogenicity

 870.4200a Carcinogenicity Study – Rat (see 870.4300)

 870.4200b Carcinogenicity (feeding) - Mouse

In a mouse oncogenicity study (MRID 44161105), bensulide (92.4 ±0.5% a.i., Lot # 

CBI 0801) was administered for 78 weeks in the diet to 50 CD-1 mice/sex/dose at levels 

to achieve constant weekly doses of 0, 1, 50, or 200 mg/kg/day. An additional 10 

mice/sex/dose were used to provide samples for plasma and red blood cell 

cholinesterase assessments at 13 weeks, and further cholinesterase assessments, 

including brain cholinesterase at 52 weeks; these animals were terminated and discarded 

at 52 weeks. All remaining animals were sacrificed at 78 weeks of the study. 

Survival rates, clinical observations, and hematological parameters were unaffected by 

treatment with bensulide. Chronic toxicity was characterized by reduced (p<0.01 or 

<0.001) cholinesterase levels (plasma, ↓92-96%; erythrocyte, ↓40-51%) in the high-dose 

males and females and reduced brain cholinesterase in the high-dose females (↓14%). 

Additionally in the high-dose males, decreased overall body weight gains (↓32%; 

p<0.001), increased absolute and relative liver weights (↑38-43%; p<0.001), and 

histopathological changes of the liver (pale foci, cell atypia, and cell foci) were observed. 

In the 50 mg/kg/day animals, reduced (p<0.01, or 0.001) plasma (↓88-92%) and RBC 

(↓31-37%) cholinesterase activities were observed and brain cholinesterase activity was 

reduced (↓12%; p<0.05) in the females. Additionally, overall body weight gain in the 

mid-dose males was reduced by 16% (p<0.05) compared to controls. 

The chronic LOAEL is 50 mg/kg/day based on inhibition of plasma and erythrocyte 

cholinesterase activity in the 50 and 200 mg/kg/day group animals, inhibition of brain 

cholinesterase activity in the mid- and high-dose females, decreased body weight gain in 

the mid- and high-dose males, and increased liver weights, and histopathological 
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changes in the high-dose males. The chronic NOAEL is 1 mg/kg/day. 

Under the conditions of this study, there was no evidence of carcinogenic potential. 

Dosing was considered adequate based on decreased plasma, RBC, and brain 

cholinesterase activities, decreased body weight gains, and by increased liver weights 

and histopathological changes of the liver. 

This study is classified as Acceptable/Guideline and satisfies the guideline requirements 

for a carcinogenicity study (§83-2b) in mice. 

870.4300 Combined toxicity/carcinogenicity – rat 

In a combined chronic/oncogenicity study (MRIDs 43919602 and 44161101), bensulide 

(92.4 ±0.5% a.i., Lot # CBI 0801) was administered in the diet for 104 weeks to 80 

Sprague-Dawley rats/sex/group at levels to achieve constant weekly doses of 0, 1, 15, or 

60 mg/kg/day. At approximately the 26, 52, and 78 week intervals, 10 rats/sex/group 

were terminated, and all remaining animals were sacrificed at 104 weeks of the study. 

Survival rates, ophthalmoscopic findings, clinical observations, hematological 

parameters, urinalysis findings, and gross findings were unaffected by treatment with 

bensulide. Chronic toxicity in rats receiving 60 mg/kg/day was characterized in both 

sexes by reduced (p<0.05, <0.01 or <0.001) cholinesterase levels (plasma, ↓59-93%; 

erythrocyte, ↓44-80%; and brain, ↓20-39%) and, in the males, by increased absolute 

liver weights (↑4-22%) and mild histopathological changes of the liver (hepatocyte 

vacuolation and eosinophilic foci). In the 15 mg/kg/day animals, reduced (p<0.05, 

<0.01, or 0.001) plasma (↓36-73%) and erythrocyte (↓20-40%) cholinesterase activities 

were also observed. 

The chronic LOAEL is 15 mg/kg/day based on inhibition of plasma and erythrocyte 

cholinesterase activity in the mid- and high-dose group animals, inhibition of brain 

cholinesterase activity in the high-dose animals, and increased liver weights and mild 

histopathological changes in the high-dose males. The chronic NOAEL is 1 mg/kg/day. 

Under the conditions of this study, there was no evidence of carcinogenic potential. 

Dosing was considered adequate by decreased cholinesterase activity (plasma, red 

blood cell, and brain) in high-dose animals and by increased absolute liver weights and 

liver histopathological changes in the high-dose males. 

This study is classified as Acceptable/Guideline and satisfies the guideline requirements 

for a chronic toxicity study (§83-1) and a carcinogenicity study (§83-2) in the rat. 

A.3.6 Mutagenicity

The available studies clearly indicate that bensulide is not genotoxic. Additionally, the 
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negative mutagenicity studies support the lack of an oncogenic effect in the rat and 

mouse long-term feeding studies and also the absence of significant reproductive or 

developmental toxicity attributable to a mutagenic mode of action (i.e., decreased total 

implants, increased resorptions). Based on the overall results, there is no concern for 

mutagenicity. 

The submitted test battery satisfies the new mutagenicity initial testing battery 

guidelines; therefore, no Category III study or additional further testing is required at 

this time. 

In a reverse gene mutation assay in bacteria (MRID 00153493), strains TA98, TA100, 

TA1535, and TA1537 of S. typhimurium were exposed to bensulide technical (92.9% 

a.i.) at concentrations of 0 (dimethyl sulfoxide solvent control; DMSO), 0.005, 0.014, 

0.041, 0.123, 0.370, 1.111, 3.333, 10.000, 25.000, or 50.000 μL/plate (TA100) or 0 

(DMSO), 0.037, 0.111, 0.333, 1.000, or 3.000 μL/plate (TA98, TA1535, and TA1537) 

in the presence and absence of mammalian metabolic activation (metabolic activation 

mixture containing the S9 fraction from livers of Aroclor 1254-induced Sprague-Dawley 

rats). 

Bensulide technical was tested up to and above levels at which it precipitated onto the 

culture medium (≥ 0.041 μL/plate for TA100; ≥ 1.000 μL/plate for TA98, TA1535, and 

TA1537). The positive controls did induce the appropriate responses in the 

corresponding strains. There was no evidence of induced mutant colonies over 

background. 

This study is classified as Acceptable/Guideline. It does satisfy the requirement for 

Guideline 84-2 for in vitro mutagenicity (bacterial reverse gene mutation) data. 

In a mammalian cell gene mutation assay (TK locus; MRID 43273901), mouse 

lymphoma L5178Y cultured cells cultured in vitro were exposed to bensulide technical 

(92.4 ± 0.5% a.i.; given in MRID 43919602) in dimethyl sulfoxide (DMSO) at 

concentrations of 8, 14, 16, 21, 24, 28, 32, 35, 40, or 42 μg/mL in the absence and at 16, 

24, 28, 32, 35, 40, 42, 48, 49, or 56 μg/mL in the presence of mammalian metabolic 

activation (S9 fraction containing homogenate from Aroclor 1254-induced rat liver). 

Bensulide technical was tested up to cytotoxic concentrations, based on preliminary 

cytotoxicity assays demonstrating significant cytotoxicity at doses near 30 

μg/mL and total cell death at doses as low as 25-30 μg/mL. There was no evidence of 

induced forward mutation at the TK locus over solvent control values at any dose tested. 

This study is classified as Acceptable/Guideline. It does satisfy the requirement for 

Guideline 84-2 for in vitro mutagenicity (gene mutation in mammalian cells) data. 

In a C57BL/6JfCD-1/Alpk mouse bone marrow micronucleus assay (MRID 41902602), 

5 animals/sex/dose were treated with a single oral (gavage) dose of bensulide technical 

(92.7% a.i.) in corn oil (vehicle) at doses of 250 or 400 mg/kg (constant dose volume of 
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10 mL/kg). Bone marrow cells were harvested at 24, 48 and 78 hours post- treatment. 

There were no signs of toxicity during the study. Bensulide technical was tested at an 

adequate dose, since the 400 mg/kg dose level (HDT) was selected based on the results of 

a preliminary acute toxicity study (2 animals/sex/dose) in which mortalities were 

observed at doses of 500 mg/kg or greater, but not at 400 mg/kg or less. The positive 

control (cyclophosphamide) induced the appropriate response. There was no significant 

increase in the frequency of micronucleated polychromatic erythrocytes in bone marrow 

after any treatment time. 

This study is classified as Acceptable/Guideline. It does satisfy the requirement for 

Guideline 84-2 for in vivo mutagenicity (mouse bone marrow micronucleus) data. 

A.3.7 Neurotoxicity

870.6100 Delayed Neurotoxicity Study – Hen 

In an acute delayed neurotoxicity study (MRID 43334302), Bensulide (tech., 92.4% a.i.) 

was assessed using groups of 15 single comb white leghorn laying hens (Gallus 

gallus domesticus) given a single neat gavage dose of Bensulide (2000 mg a.i./kg 

nominal dose; actual dose was 2262 mg/kg in a dosing volume of 2 mL/kg). An acute 

oral toxicity study (43306301) determined an LD50 of 3221 mg/kg for Bensulide in the 

domestic laying hen. Positive controls (12 birds) were given 800 mg TOCP/kg and 12 

birds given corn oil served as vehicle controls. Three birds of each group were 

sacrificed at -48 hrs for activity analysis of neurotoxic esterase (NTE) in brain and spinal 

cord and acetylcholinesterase (AChE) in brain. Behavior assessments (locomotor 

ability) were conducted on nine birds from both control groups and 12 birds from the 

Bensulide group over a period of 21 days. Pathology (brain, spinal column and 

peripheral nerves) was evaluated in all remaining animals at Day 21. 

Based on the study results, Bensulide did not induce acute delayed neurotoxicity in the 

domestic laying hen at the dose tested. NTE activity was not affected by treatment. A

non-significant decrease of -24% was observed for brain cholinesterase in treated hens. 

This study meets the requirements of § 81-7 and is classified as Acceptable/Guideline 

because, although animals were not tested at the LD50 and no signs of neurotoxicity were 

observed, animals were tested at the limit dose of 2 g/kg. 

 870.6200 Acute Neurotoxicity Screening Battery

In an acute neurotoxicity screening study (MRID 43195901), 22 CD rats/sex/group were 

administered single gavage doses of 0, 30, 100 or 300 mg bensulide (tech., 

92.4% a.i.)/kg (males) or 0, 15, 50 or 150 mg/kg (females) in 5 mL/kg corn oil. 

Functional observational battery (FOB) and motor activity tests were conducted on 12 

rats/sex/dose pretreatment, on the day of dosing (day 0) and days 7 and 14 post-dosing. 

Plasma, erythrocyte and brain cholinesterase (ChE) activities were measured from 5 
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rats/sex at pretreatment, day 0 (6.25 and 6.75 hrs post- dosing) and day 15. Six perfused 

control and high dose rats/sex were evaluated for neuropathology. 

At 150 mg/kg (females only), an increased incidence of diarrhea, flaccid abdominal 

and/or body tone (all 6/12 vs. 1, 2 and 2, controls) and pinpoint pupils (3/12 vs 0, 

controls) were observed on Day 0 in the FOB. At 300 mg/kg (males only), one death 

occurred on Day 1, preceded by clinical signs (salivation, lacrimation/ocular discharge, 

decreased respiration, hypothermia, and fur staining on muzzle and ventral surface). A 

second male exhibited abnormal respiration, tremors, hypoactivity, dehydration and fur

staining between Days 1-3. In the FOB, increased incidence of decreased arousal and 

locomotor activity (for both, 7/12 vs. 3, controls) were observed. A slight but 

statistically significant depression of body weight (-6.6%) was also observed on Day 7. 

No treatment-related effects on motor activity or macroscopic/microscopic 

neuropathology were reported. The LOAEL is 150 mg/kg, based on minimal, transient 

clinical signs consistent with cholinesterase inhibition in females. The NOAEL is 100 

mg/kg. 

At 50 mg/kg (females only), plasma ChE was decreased on day 0 by 80% less than 

controls (not significant). At 100 mg/kg (males only), plasma ChE was decreased on 

day 0 by 53% (not significant). At 150 mg/kg (females only) on day 0, reductions were 

observed in plasma ChE (89% less than controls, p<0.01) and erythrocyte ChE (37% 

less than control, p<0.01) both of which showed partial recovery by day 15. However, a 

significant decrease (73% of control, p<0.01) in brain ChE for high-dose females was 

noted on day 15 which was not present at day 0 (18% less than controls, not significant). 

At 300 mg/kg (males only), statistically significant ChE inhibition was observed only in 

the high-dose groups. On day 0, there were significant decreases in brain ChE (62% of 

control, p<0.01), plasma ChE (19% of control, p<0.01), and erythrocyte ChE (60% of 

control, p<0.01) for males of the high dose (300 mg/kg) group. At day 15, brain ChE 

was still significantly reduced (73% of control, p<0.01) but values for plasma and 

erythrocyte ChE had returned to normal. 

The plasma ChE inhibition LOAEL is 50 mg/kg, based on 80% inhibition (no p) of 

plasma cholinesterase activity in females on Day 0. The plasma ChE NOAEL is 15 

mg/kg. 

The RBC ChE inhibition LOAEL is 150 mg/kg, based on 37% inhibition (p ≤ 0.01) of 

RBC ChE activity in females on Day 0. The RBC ChE NOAEL is 50 mg/kg. 

The brain ChE inhibition LOAEL is 150 mg/kg, based on 18% inhibition (no p) of brain 

ChE activity in females on Day 0 and 27% inhibition (p ≤ 0.01) on Day 15. The brain 

ChE NOAEL is 50 mg/kg. 

This study is classified as Acceptable/Guideline and satisfies the guideline requirement 

for an acute neurotoxicity study in rats (§81-8ss). 
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 870.6200 Subchronic Neurotoxicity Screening Battery (Not Submitted; Not 

Required – Waived; Leshin, 2015, TXR # 0057280)

 870.6300 Developmental Neurotoxicity Study (Not Submitted; Not Required – 

Waived; Leshin, 2015, TXR # 0057280)

A.3.8 Metabolism

870.7485 Metabolism – Rat 

In a metabolism study (MRIDs 42007901-42007904), bensulide technical, labelled with 

14C in the phenyl ring (> 96.4% radiopurity; 925 MBq/mMole) was dissolved in corn oil 

(vehicle) and administered to Sprague-Dawley rats (5/sex/group; 7-8 weeks of age; 185-

235 g body weight) following three treatment regimes. Animals in Group I received a 

single oral dose of radioactive bensulide at 1 mg/kg of body weight. Animals in Group 

II received 14 consecutive doses (1 mg/kg/day) of non-radioactive bensulide technical 

(99% a.i.) in corn oil, followed by a 1 mg/kg dose of radiolabelled bensulide technical in 

corn oil on day 15. Group III animals received a single oral dose of radiolabelled 

bensulide technical at 100 mg/kg of body weight. An additional group of animals 

(Group IV; 3/sex/group) were given a single oral dose of radiolabelled bensulide 

technical at 1 mg/kg of body weight and were subsequently used for autoradiological 

radiolabelled carbon dioxide release determinations. Administration by gavage was 

used for all treatment groups, and the volume of the corn oil and bensulide technical 

solution was kept at a constant of 4mL/kg of body weight. 

For animals in Groups I-III, urine and feces were collected at 12, 24, 36, and 48 hours 

post-dosing and at 24- hour intervals thereafter until 7 days after dosing with 

radioactive bensulide. All animals in Groups I-III were sacrificed 7 days after 

treatment with radioactive bensulide technical, and the following organs were removed 

and assayed for radioactivity: blood, liver, kidneys, muscle, fat lungs, uterus, heart, 

bone, spleen, thyroid, salivary glands, brain, adrenals, ovaries, testes, pancreas, 

gastrointestinal tract (stomach, small and large intestines, and caecum) and its contents, 

and the residual carcass. Radioactivity was determined by tissue combustion and/or 

liquid scintillation counting. For Groups IV animals, two rats of each sex were used 

for the autoradiography study and 1 rat of each sex was used or the carbon dioxide 

study. 

In the autoradiography study, animals were sacrificed with Halothane at 24 hours after 

dosing with radioactive bensulide technical. The animals were then immediately frozen 

in a mixture of hexane and solid carbon dioxide. Each frozen carcass was embedded in a 

block of 2% carboxymethyl cellulose, and longitudinal sagittal section of about 20 μM 

thickness were cut and representative sections freeze-dried and subjected to 

autoradiography. In the carbon dioxide study, 14C-radiolabelled derived from the 

metabolism of radioactive bensulide technical and present in expired air was collected by 

passing the air through a 2N NaOH solution at 6, 12, 24, 36, and 48 hours after dosing. 
Bensulide Human Health Risk Assessment DP No. D428598 

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The major route of excretion was via the urine, with peak urinary excretion of 14Cbensulide equivalents occurring between 0 to 24 hours for males and females in the lowdose group (Group I; 1 mg/kg) and in the high-dose group (Group III; 100 mg/kg). In 

Group I, total urinary excretion of 7 days after administration of radioactive bensulide 

technical accounted for 70 and 75 percent of the administered dose in males and 

females, respectively. Of these totals, 57 and 72 percent were excreted during the first 

24 hours after dosing for males and females, respectively. In Group III, total urinary 

excretion accounted for 75 and 87 percent of the administered dose in males and 

females, respectively. Of these totals, 64 and 76 percent were excreted during the first

24 hours after dosing for males and females, respectively. 

For Group II (prior 14-day administration of non-radioactive bensulide technical before 

radioactive bensulide administration, both at 1 mg/kg), total urinary excretion of

radioactivity over 7 days past dosing with radioactive bensulide accounted for 79 and 88 

percent of the administered dose in males and females, respectively. Of these totals, 63 

and 83 percent were excreted during the first 24 hours after dosing for males and 

females, respectively. For Group IV, urinary excretion of 14-C radioactivity derived from 

bensulide technical over a 48-hour period accounted for 67% for one male and 86% in 

one male. 

For Group I, total fecal excretion of radioactivity derived from 14C-bensulide technical 

over 7 days post-dosing accounted for 22 and 20 percent of the administered dose in 

males and females, respectively. Of these totals, 18 percent was excreted during the first 

24 hours for both males and females. For Group III, total fecal elimination over 7 days 

post-dosing of bensulide-derived radioactivity accounted for 22 and 11 percent of the 

administered dose for males and females, respectively. Of these totals, 20 and 8 percent 

were excreted during the first 24 hours after dosing for males and females, respectively. 

In Group II animals, total fecal excretion of radioactivity over 7 days post-dosing 

accounted for 14 and 8 percent of the administered dose for males and females, 

respectively. Of these totals, 9 and 6 percent were excreted during the first 24 hours 

post-dosing for males and females, respectively. In Group IV, fecal excretion of

radioactivity over 48 hours post-dosing accounted for 12% of the administered dose in 

one male and 7% in one female. 

The amount of residual radioactivity in all organs/tissues except for the liver (0.02 to 

0.21% of the dose) from all rats was low at 7 days after single oral administration of 

radioactive bensulide technical. The radioactivity found in the carcasses and in other 

tissues accounted for 0.3% to 2.5% and less than 0.1% of the administered dose, 

respectively. The highest concentration of radioactivity was found in whole blood. The 

majority of the radioactivity in the blood was associated with the cellular component. In 

general, less well perfused tissues showed lower concentrations of radioactivity. Whole 

body autoradiography of rats killed 24 hours after dosing showed that, in male rats, the 

majority of the radioactivity was present in the blood, lung, spleen, bone marrow, and 

the glandular part of the stomach, the contents of the intestines, and in the intestinal 

walls. Moderate amounts of radioactivity was found in the liver, kidney, salivary glands, 
Bensulide Human Health Risk Assessment DP No. D428598 

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the capsule of the seminal vesicles, nasal passages and the white matter of the brain. 

The intensity of radioactivity in the female rats was much lower than in the male rats. 

In a biotransformation study (MRID 42225401), bensulide metabolites were quantitated 

and identified in rat urine and fecal extracts from previous studies (MRID 42007901-

42007903). To obtain sufficient material to confirm metabolite identities, four 

successive daily doses of 50 mg [14C]-bensulide/kg were administered to 5 SpragueDawley female rats (bulk collection experiment; 99% a.i., unlabeled, Batch No. 

Y06379/006; >98.0% a.i., [14C]-labeled, Batch No. Y06379/005). Biliary excretion was 

assessed in one male and one female rat with cannulated bile ducts given an oral dose of 

100 mg [14C]-bensulide/kg. 

No animals died before scheduled sacrifice in either experiment. In the bulk collection 

experiment, 52.5% of the administered dose was recovered in the urine and 16.3% in the 

feces. In cannulated rats, a substantially higher fraction of the given dose was in the 

feces (40.9% in the male, 68.6% in the female), possibly due to poor intestinal wall 

absorption. Biliary excretion was minimal (5-6% of dose) and biliary metabolites were 

not analyzed; the mass balance accounting was acceptable (109.2%-114.4%). 

Bensulide metabolites found by TLC in excreta from previous studies accounted for 

about 59-78% of the administered dose in the urine and about 2.5-8.3% in the feces, 

distribution varying with sex and dose. Four metabolites were identified. Metabolite I 

was the most abundant in the urine for all doses in both sexes (26-58% of given dose) 

whereas in fecal extracts, Metabolites I, II, or IV predominated (each 0.25-3.4% of 

dose). Unidentified metabolites individually represented < 3% of the dose except 

urinary metabolite “H” (≤ 16.1% of dose) and one fecal metabolite (TLC spot 6; ≤ 6.23% 

of dose). Metabolite I and II formation is proposed to involve cleavage of the 

PO2[CH(CH3)2]2 moiety of bensulide, followed by methylation and oxidation of the 

sulphur atom. Conjugation with glycine or carboxylation and oxidative desulphuration 

is proposed to lead to Metabolite III and IV formation, respectively. 

This study is classified acceptable/guideline. It was intended to satisfy the guideline 

requirement for a metabolism study (§85-1) in rats together with four previous studies 

(MRIDs 42007901-42007904). Together these metabolism studies satisfy the 

Guideline (§85-1) requirements for metabolism data for bensulide technical in rats. 

 870.7600 Dermal Absorption – Rat (Not Submitted; Not Required)
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A.3.9 Immunotoxicity 

 870.7800 Immunotoxicity

In an immunotoxicity study (MRID 48377701), bensulide (94.12% a.i., Lot No. TQBTS1001-019) in 1% methyl cellulose in water was administered via gavage to female 

B6C3F1 mice (8/group) at dose levels of 0, 50, 200, or 800 mg/kg/day for 28 days. The 

female mouse was selected as the default species/sex for immunotoxicity study. 

Cyclophosphamide (positive control) was injected intraperitoneally at a dose of 80 mg/kg 

approximately 24 hours prior to sacrifice. On study day 25, each mouse was immunized 

with sheep red blood cell (SRBC) via an intraperitoneal injection (2x108

 SRBC/animal). 

On Day 29, T-cell dependent antibody response (TDAR) was determined with an antiSRBC plaque forming cell (PFC) assay. 

Two animals in the 800 mg/kg/day group died. These animals demonstrated labored 

breathing, hypoactivity and were cold to the touch. The gross necropsy indicated that 

these deaths were due to toxic response to bensulide. There was an overall weight gain in 

all dose groups and the vehicle control group. The body weight changes did not indicate 

any remarkable departures from normal animal growth or feeding behavior. The mean 

absolute and relative spleen and thymus weights of animals in the test groups did not 

show significant differences from controls. 

The results of the TDAR were considered unacceptable. The performing laboratory did 

not follow the original study protocol. The amended procedure stated that additional 

rabbit anti-mouse IgG was added to one of the duplicate tubes containing the splenocytes, 

sheep red blood cells and guinea pig complement to allow the detection of IgG secreting 

PFCs in addition to the IgM secreting PFCs. The total PFCs per 106

 cells was then 

calculated by combining PFC of two tubes together. The principle of the anti-SRBC PFC 

assay is to measure the effect of test substance on the anti-SRBC IgM secreting cells. The 

addition of IgM PFCs and IgG PFCs from both tubes as the total plaques formation was 

misleading and flawed. Nonetheless, the procedures for measuring IgG secreting cells 

and interpretation of data in this study were incorrect. Detailed comments are described 

in the reviewer’s comment section of this DER. 

In addition, the responsiveness of the immunization in this study was questionable. The 

study report claimed the response of the vehicle control animals exceeded the minimum 

expectations (800 total plaques/1x106 spleen cells) by combining both tubes including the 

IgM PFCs and the IgG PFCs. This statement was incorrect because the stated IgG PFC 

tube would already have included IgM and IgG PFCs; it would be double counting if 

combining both tubes. The purpose of the duplicate tubes was to obtain an average of the 

PFCs formation for each spleen. The individual animal data in this study on the IgM 

plaques formation indicated that the animals had not been properly stimulated after 

SRBC injection (e.g., only one animal in the vehicle control group responded with greater 

than 800 PFCs per 106

 cells). The results suggested that antigen (SRBC) might have been 

accidentally injected into the intestinal tract. 
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The report of the study suggests that the performing laboratory lacks understanding of the 

immunotoxicity study. The performing laboratory needs to establish a standard operation 

procedure (i.e., test procedures, SRBC antigen injection technique by i.v. or i.p., and 

establish optimum amount of complement to be added to the assay tube) and validate its 

proficiency. 

This immunotoxicity study in mice is Unacceptable/guideline and does not satisfy the 

guideline requirement for an immunotoxicity study (OPPTS 870.7800). This data 

requirement was waived by HASPOC (van Alstine, 2013, TXR # 0056738). 

A.3.10 Special/Other Studies 

Non-guideline Comparative Cholinesterase Assay – Rat 

The purpose of this non-guideline study was to identify any sensitive populations that 

may exist (pregnant females, immature (PND 11) rats, or fetuses) to the cholinesterase 

(ChE) inhibitory effects of bensulide, an organophosphate. Toxicity was evaluated in 

each of these lifestages/sub-populations and compared to adults. Both acute and repeated 

dose regimens were evaluated, as well as treatment during the organogenesis and fetal 

phases of pregnancy (gestation day [GD] 6-20). 

In the acute study (MRID 49433502), young adult Sprague-Dawley rats and PND 11 

pups (10/sex/dose) were treated by a single gavage (5 mL/kg) dose with bensulide in corn 

oil. The dose groups were 0, 50, 100, 150, and 200 mg/kg/day in the adult males, 0, 25, 

50, 100, and 150 mg/kg/day in adult females, and 0, 20, 40, 60, and 100 mg/kg/day in the 

pups. 

In the repeated dose study (MRID 49466201), young adult Sprague-Dawley rats and 

PND 11 pups (10 adult females/dose [no male adults] and 10 pups/sex/dose) were treated 

by gavage (5 mL/kg) with bensulide in corn oil. The dose groups were 0, 15, 25, 50, and 

75 mg/kg/day in the adults and 0, 5, 10, 20, 40, and 60 mg/kg/day in the pups. Animals 

were treated once daily for 10 consecutive days. 

In the gestational study (MRID 49454001), adult Sprague Dawley rats were bred and 

pregnant females (10/dose) were treated by gavage (5 mL/kg) with bensulide in corn oil 

once daily during GD 6-20 (inclusive). The dose groups were 0, 15, 30, 60, and 90 

mg/kg/day. 

In all studies, blood and brain samples were collected at the time of peak effect, 

previously determined to be 16 hours after treatment of adults and pups. Samples were 

processed and assayed for cholinesterase levels by the modified Ellman’s method. 

Additionally, mortality and clinical signs were evaluated in the acute study. Body 

weights were also evaluated in the repeated and gestational studies. A necropsy was also 

performed on all animals in the gestational study only. 
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In all studies, no adverse treatment-related effects were noted on mortality, clinical signs, 

body weight, body weight gains, or gross pathology (gestational study). 

Dose-dependent decreases in cholinesterase activity were observed in the brain and RBC 

in all three studies. 

In the acute study, decreases (p≤0.01) in cholinesterase activity were noted as follows: (i) 

adult male RBC at 100 mg/kg/day and above (↓22-69%); (ii) adult female RBC at 50 

mg/kg/day and above (↓26-89%); (iii) adult male brain at 100 mg/kg/day and above (↓14-

46%); (iv) adult female brain at 50 mg/kg/day and above (↓12-62%); (v) PND 11 male 

pup RBC at 40 mg/kg/day and above (↓32-78%); (vi) PND 11 female pup RBC at 40 

mg/kg/day and above (↓31-77%); (vii) PND 11 male pup brain at 40 mg/kg/day and 

above (↓20-57%); and (viii) PND 11 female pup brain at 40 mg/kg/day and above (↓19-

58%). 

In the repeated dose study in the adult female RBC, dose-related increases (p≤0.01) in 

ChE inhibition were observed at 25 mg/kg/day and above (↓22-91%). Decreases 

(p≤0.01) in adult female brain cholinesterase activities were noted at 50 mg/kg/day and 

above (↓51-69%). In the pups, decreased (p≤0.01) RBC cholinesterase activity were 

noted in males at 10 mg/kg/day and above (↓13-71%) and in females at 20 mg/kg/day 

and above (↓35-72%). Decreased (p≤0.01) pup brain cholinesterase activity were noted 

in males at 20 mg/kg/day and above (↓11-46%) and females at 40 mg/kg/day and above 

(↓33-42%). 

In the gestational study in the dam RBC, dose-related increases (p≤0.01) in ChE 

inhibition were noted at 30 mg/kg/day and above (↓52-99%). Dam brain ChE inhibition 

(p≤0.01) was also observed at 30 mg/kg/day and above (↓19-84%). In the fetal RBC, 

dose-related increases (p≤0.01) in ChE inhibition were noted at 30 mg/kg/day in both 

sexes (↓20-92%). In the fetal brain, dose-related increases (p≤0.05) in ChE inhibition 

were also noted in both sexes at 30 mg/kg/day and above (↓9-49%), with the males being 

slightly more sensitive than females. 

In the acute study, the LOAEL in adults was 50 mg/kg/day based on ChE inhibition 

in the RBC and brain of females. The NOAEL was 25 mg/kg/day. The LOAEL in 

the PND 11 pups was 40 mg/kg/day based on ChE inhibition in the RBC and brain 

of males and females. The NOAEL was 20 mg/kg/day. 

In the repeated dose study, the LOAEL in adults was 25 mg/kg/day based on ChE 

inhibition in the RBC of females (only sex tested). The NOAEL was 15 mg/kg/day. 

The LOAEL in the PND 11 pups was 10 mg/kg/day based on ChE inhibition in the 

RBC of males. The NOAEL was 5 mg/kg/day. 

In the gestational study, the LOAEL in dams and fetuses was 30 mg/kg/day based 

on ChE inhibition in RBC and brain. The NOAEL was 15 mg/kg/day. 
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This study is acceptable and fulfills the purpose of this non-guideline study. The study 

identified sensitivity (or lack thereof) in sub-populations (pregnant females, immature 

(PND 11) rats, or fetuses. 

Appendix A.4. Lifestage Sensitivity to Bensulide-Induced Acetyl Cholinesterase (AChE) 

Inhibition in the RBC of Rats Following Oral Treatment 

MRID # 

Test 

Lifestage 

Sex 

BMD10

(mg/kg/day) 

Nearest Dose to 

90% of Control 

(% of Control)

FoldDifference b Conclusion 

Acute a

Pup vs Adult 

49433502 

Acute CCA 

Adult 

Male 79.11 50 (99%) 

100 (78%) 4.5 The pup is more sensitive 

49433502 than the adult. 

Acute CCA 

Pup (PND 

11) Male 17.74 20 (91%) 

49433502 

Acute CCA 

Adult 

Female 27.21 25 (95%) 

50 (73%) 1.7 The pup is more sensitive 

49433502 than the adult. 

Acute CCA 

Pup (PND 

11) Female 16.23 20 (88%) 

Steady State 

Pup vs Adult 

49466201 

Repeated Dose 

CCA 

Adult 

Female 18.66 15 (94%) 

25 (78%) 

1.5 The pup is more sensitive 

49466201 than the adult. 

Repeated Dose 

CCA 

Pup 

Female 12.30 5 (93%) 

Fetus vs Dam 

49454001 

Gestational 

CCA 

Dam 12.01 15 (94%) 

30 (48%) Dam vs male 

fetus: 0.5 

Dam vs 

female fetus: 

0.6 

The fetus is not more 

sensitive than the mother. 

49454001 

Gestational 

CCA 

Male 

Fetus 22.34 15 (101%) 

30 (80%) 

49454001 

Gestational 

CCA 

Female 

Fetus 21.82 15 (100%) 

30 (80%) 

Pregnant vs 

Non-Pregnant 

49454001 

Gestational 

CCA 

Dam 12.01 15 (94%) 

30 (48%) 

0.6 

The pregnant female is not 

more sensitive than the nonpregnant female at doses 

relevant to risk assessment. 

The level of 

acetylcholinesterase 

inhibition was exactly the 

same at 15 mg/kg/day and 

the steady-state POD is 6 

mg/kg/day. 

49466201 

Repeated Dose 

CCA 

Adult 

Female 

(Not 

Pregnant) 18.66 15 (94%) 

25 (78%) 

a

 No data available to compare fetus vs dam or pregnant vs non-pregnant lifestages following a single dose. b Upper Row ÷ Lower Row of Merged Cell. When BMD did not agree with empirical evidence, the dose tested which provided 

inhibition nearest 10% was used instead of BMD10. 
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Appendix B. Physical/Chemical Properties 

Table B1. Physicochemical Properties of Bensulide and Bensulide Oxon 

Parameter Value Reference 

Bensulide 

Molecular weight (g/mole) 397.54 MRID 45761801 

Melting point (°C) 36 MRID 41532001 

Water solubility ( mg/L at 25°C) 5.6 MRID 41532001 

Vapor pressure at 25°C (mmHg) 8.2 x 10-7 MRID 41532001 

Dissociation constant (pKa) Not Applicable 

Octanol/water partition coefficient Log(KOW) 4.20 H. Zhong, D428601, 

09/14/2015 (values 

modeled with EPI Suite, v 

4.10) 

Bensulide oxon 

Molecular weight (g/mole) 381.44 H. Zhong, D428601, 

09/14/2015 (values 

modeled with EPI Suite, v 

4.10) 

Melting point (°C) 89.97 

Water solubility ( mg/L at 25°C) 461.24 

Vapor pressure at 25°C (mmHg) 2.48 10-8

Dissociation constant (pKa) Not Applicable 

Octanol/water partition coefficient Log(KOW) 2.35 
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Appendix C. Review of Human Research 

This risk assessment relies in part on data from studies in which adult human subjects were 

intentionally exposed to a pesticide or other chemical. These data, which include studies from 

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

Exposure Task Force (AHETF) database and, the Aquatic use Standard Operation Procedure 

(20-Sep-2013) and are subject to ethics review pursuant to 40 CFR 26, have received that 

review, and are compliant with applicable ethics requirements. For certain studies that review 

may have included review by the Human Studies Review Board. Descriptions of data sources as 

well as guidance on their use can be found at http://www2.epa.gov/pesticide-science-andassessing-pesticide-risks/occupational-pesticide-handler-exposure-data and 

http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticidepost-application-exposure. 
Bensulide Human Health Risk Assessment DP No. D428598 

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Appendix D. International Residue Limits Table 

Bensulide (PC Code 009801) 

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex

40 CFR 180.241:

(a) General. (1) -(O,O-diisopropyl 

phosphorodithioate) of N-(2-mercaptoethyl) 

benzenesulfonamide including its oxygen analog 

S-(O,O-diisopropyl phosphorothioate) of N-(2-

mercaptoethyl) benzenesulfonamide

None None 

Commodity1 Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico2 Codex

Onion, bulb 0.10 

Vegetable, brassica, leafy group 5 0.15

Vegetable, cucurbits group 9 0.15

Vegetable, fruiting group 8 0.10

Vegetable, leafy except brassica 

group 4

0.15

 

Completed: M. Negussie; 09/21/15

1

 Includes only commodities of interest for this action. Tolerance values should be the HED recommendations and 

not those proposed by the applicant. 

2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes. 

(c) Tolerances with regional registrations. Tolerances with regional registration, as defined in §180.1(l), 

are established for the residues of S-(O,O-diisopropyl phosphorodithioate) of N-(2-mercaptoethyl) 

benzenesulfonamide including its oxygen analog S-(O,O-diisopropyl phosphorothioate) of N-(2-

mercaptoethyl) benzenesulfonamide in or on the following food commodities: 

Commodity Parts per million 

Carrot, roots 0.10 
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Appendix E. Comparison of Residue Levels of Bensulide and its Oxon 

Table E summarizes residue data for commodities that do not have PDP data available for both 

parent bensulide and its oxon. The purpose is to provide information to address the dietary 

exposure and risk assessment. In addition, PDP data for lettuce (in which bensulide and its oxon 

were measured) were included. 

Table E. Summary of Residue Levels for Bensulide and its Oxon 

Matrix (Reference) Use Pattern / 

PDP Sample ID 

Bensulide Bensulide 

Oxon 

Factor 

(Oxon/Parent) 

Tomato Metabolism 

(D179576, 04/21/1993) 

8.6 lbs ai/A pre-plant 

112-153 day PHI 

ND 

(86% TRR 

iden/char) 

ND 

(86% TRR 

iden/char) 

NA 

Lettuce Metabolism 

(D1855889, 03/29/1993) 

8.6 lbs ai/A soil pre-plant 

67 day PHI 

ND 

(86% TRR 

extracted) 

2% TRR 

(86% TRR 

extracted) 

NA 

Carrot Metabolism 

(D177460, 06/02/1992) 

8.6 lbs ai/A soil pre-plant 

126 day PHI 

30% TRR 

(94% TRR 

extracted) 

2.8% TRR 

(94% TRR 

extracted) 

0.09x 

Squash Field Data 

(D218256, 01/24/1996) 

9 lbs ai/A pre-plant ND1 ND1 NA 

Cucumber Field Data 

(D218256, 01/24/1996) 

9 lbs ai/A pre-plant ND1 ND1 NA 

Bulb Onion 

(D206633, 11/29/1994) 

9 lbs a.i./A pre-plant or preemergence 

Harvest at Maturity 

ND1 ND1 NA 

Bell Peppers 

(D238521, 10/07/1997) 

5-9 lbs ai/A pre-plant or 

pre-emergence 

109-129 day PHIs 

ND1 ND1 NA 

Lettuce PDP Results (years 

2010-2011) 

2010-6721 0.005 0.01 2.0 

2010-6845 0.004 0.005 1.3 

2010-7044 0.014 0.12 8.6 

2010-7052 0.005 0.008 1.6 

2010-7265 0.014 0.023 1.6 

2011-6295 0.012 0.003 0.3 1

 The LOQ is reported to be 0.05 ppm. 

Lettuce: The metabolism study with lettuce showed detection of the oxon but not of the parent 

bensulide which suggest that the oxon may predominate. PDP data for lettuce (years 2010 and 

2011) shows that bensulide (LOD ≤ 0.014 ppm) was detected in 6 of 1487 samples whereas 

bensulide oxon (LOD ≤ 0.002 ppm) was detected in 49 of those 1487 samples. The samples in 

which both were detected were included in the table above in order to estimate the ratio of the 

concentration of the oxon with respect to parent bensulide. These factors range from 0.3 to 8.6. 

This data suggest a factor of 9x for oxon residues with respect to bensulide. 

Other Crops (Non-Leafy): The metabolism study with tomato and carrot and the crop field trial 

data do not suggest that parent bensulide or the oxon may be present at significant 

concentrations. PDP data with summer squash, carrot and tomato was generated for bensulide 

and its oxon. Only two sample of tomato showed bensulide being detected; however, there were 

not detects of the oxon. This suggest that both residues of concern would be at low 

concentrations and that the oxon do not seem to predominate in these crops.