UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: 02-DEC-20 14 

SUBJECT: Sodium Bentazon - Preliminary Human Health Risk Assessment for Registration 

Review. 

PC Code: 275200, 103901 

Decision No: 486719 

Petition No: N/A 

DP Barcode: 0417312 

Registration Nos.: NA 

Regulatory Action: Registration Review Risk Assessment 

Risk Assessment Tvpe: Single ChemicaVAggregate Case No.: 0182 

TXRNo.: CAS No.: 50723-80-3, 25057-89-0 

MRIDNo.: NA 40 CFR: §180.355 

From: Kelly M. Lowe, Environmental Scientist ~ _ 

George F. Kramer, Ph.D., Senior Chemist • 

Anwar Y. Dunbar, Ph.D., Pharmacologist · ' Jl . --- Risk Assessme~t Branch 1 (RAB 1) j/ 

Health Effects Division (HED; 7509P) 

Through: Charles W. Smith III, Branch Chief 

RABl/HED (7509P) 

___ , 

To: Carolyn Schroeder 

Pesticide Reevaluation Division (7506P) 

As part of Registration Review, the Pesticide Re-evaluation Division (PRD) of OPP has 

requested that HED evaluate the hazard and exposure data and conduct occupational and 

residential exposure assessments, as needed, to estimate the risk to human health that will result 

from the currently registered uses of pesticides. This memorandum serves as HED's Preliminary 

Registration Review risk assessment of the dietary, occupational and residential handler, postapplication exposure, and aggregate risk from the registered uses of sodium bentazon. 

A summary of the findings and an assessment of human risk resulting from the registered uses 

are provided in this document. The risk assessment and the occupational/residential exposure 

and risk assessment were provided by Kelly Lowe (RAB 1 ), the dietary risk assessment and 

residue chemistry review were provided by George Kramer (RAB 1 ), the hazard characterization 

was provided by Anwar Dunbar (RAB 1 ), and the drinking water assessment was provided by 

Stephen Wente of the Environmental Fate and Effects Division (EFED). 

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Bentazon Preliminary Human Health Risk Assessment D471312 

Table of Contents 

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

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

2.1 Data Deficiencies/Data Needs ........................................................................................ 6 

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

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

2.2.2 Recommended Tolerances .................................................................................... 7 

2.2.3 Revisions to Established Tolerances ..................................................................... 9 

2.2.4 International Harmonization ................................................................................. 9 

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

3.0 Ingredient Profile ................................................................................................................ 9 

3.1 Chemical Identity ............................................................................................................ 9 

3.2 Physical/Chemical Properties .......... ............................................................................. 10 

3.3 Use Pattern .................................................................................................................... 10 

3.4 Anticipated Exposure Pathways ................................................................................... 12 

3.5 Consideration ofEnvironmental Justice ........................................................................ 12 

4.0 Hazard Characterization and Dose-Response Assessment.. ............................................. 13 

4.1 Toxicology Studies Available for Analysis .................................................................. 13 

4.2 Absorption, Distribution, Metabolism, & Excretion (ADME) ..................................... 13 

4.2.1 Dermal Absorption .............................................................................................. 14 

4.3 Toxicological Effects .................................................................................................... 14 

4.4 Safety factor for Infants and Children (FQPA Safety Factor) ...................................... 15 

4.4.1 Completeness ofthe Toxicology Database ......................................................... 15 

4.4.2 Evidence ofNeurotoxicity .................................................................................. 15 

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

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

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

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

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

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

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

Risk Assessment ............................................................................................................... 1 7 

4.6 Endocrine Disruptor Screening Program ...................................................................... 18 

5. 0 Dietary Exposure and Risk Assessment ........................................................................... 19 

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

5 .1.1 Summary of Plant and Animal Metabolism Studies ........................................... 19 

5.1.2 Summary of Environmental Degradation ........................................................... 20 

5.1.3 Comparison of Metabolic Pathways ................................................................... 20 

5 .1.4 Residues of Concern Summary ........................................................................... 20 

5.2 Food Residue Profile .................................................................................................... 20 

5.3 Drinking Water Residue Profile ................................................................................... 21 

5.4 Dietary (Food + Drinking Water) Risk Assessment.. ................................................... 21 

6.0 Residential (Non-Occupational) Exposure/Risk Characterization ................................... 22 

6.1 Residential Handler Exposure/Risk Estimates ............................................................. 22 

6.2 Residential Post-application Exposure/Risk Estimates ................................................ 23 

6.3 Residential Risk Estimates for Use in Aggregate Assessment.. ................................... 23 

6.4 Spray Drift .................................................................................................................... 24 

6.5 Residential Bystander Post-Application Inhalation Exposure .................................. .... 24 

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7.0 Aggregate Exposure/Risk Characterization...................................................................... 25

8.0 Cumulative Exposure/Risk Characterization.................................................................... 26

9.0 Occupational Exposure/Risk Characterization ................................................................. 27

10.0 References......................................................................................................................... 30

Appendix A. Toxicology Profile and Executive Summaries....................................................... 32

Appendix B. Physical/Chemical Properties................................................................................. 37

Appendix C. International Residue Limits .................................................................................. 38

7.1 Acute Aggregate Risk................................................................................................... 25

7.2 Short- and Intermediate-Term Aggregate Risk ............................................................ 25

7.3 Chronic Aggregate Risk................................................................................................ 26

7.4 Cancer Aggregate Risk ................................................................................................. 26

9.1 Handler Risk Assessment ............................................................................................. 27

9.2 Post-Application Risk Assessment ............................................................................... 29

9.2.1 Inhalation Post-Application Risk Assessment .................................................... 29

9.2.2 Dermal Post-Application Risk Assessment ........................................................ 30
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1.0 Executive Summary

Sodium bentazon (herein referred to as bentazon) is a selective, contact, early postemergent 

herbicide used to control a variety of broadleaf weeds and sedges. This preliminary risk assessment 

provides information to support the Registration Review of bentazon, and addresses the exposures 

and risk estimates associated with all currently registered uses. Since the last risk assessment, new 

data have been submitted and policies have changed. This document incorporates changes made to 

the selected endpoints, toxicological points of departure (PODs), exposure and risk estimates, 

recommended tolerances, and the potential for spray-drift exposure. All data requirements 

previously identified during the scoping process have been satisfied (G. Kramer, D375437, 17-

MAR-2010). 

Hazard Assessment: In subchronic studies in rats and dogs and in chronic studies in all species, 

the most toxicologically significant effects were changes in hematological/coagulation 

parameters following bentazon administration through the oral route. In rats and rabbits, fetal 

effects occurred at doses that caused maternal toxicity. In the rat developmental toxicity study, 

maternal effects consisted of increased post-implantation loss and fetal resorptions, and 

developmental effects consisted of skeletal variations and reduced fetal weights. In the rabbit 

developmental toxicity study, at the highest dose tested, maternal effects consisted of partial 

abortions with resorptions, and developmental effects consisted of an increased incidence of no 

living fetuses. In the two-generation reproductive toxicity study in rats, there was an increased 

quantitative offspring susceptibility. Offspring toxicity manifested as reduced absolute pup 

weights during lactation at a dose lower than where parental systemic toxicity was observed. 

The sole parental effect was an increased incidence of kidney mineralization and liver 

microgranuloma. There were no effects on reproductive parameters.

In the acute neurotoxicity study, effects observed at the mid- and high-dose groups consisted of 

decreased motor activity in males on day 0. There were no effects in the subchronic neurotoxicity 

study, and bentazon was negative for immunotoxicity. In a 21-day dermal toxicity study, no effects 

were observed up to 1000 mg/kg/day. Bentazon was not found to be mutagenic, and is classified as 

a Group “E” chemical (evidence of non-carcinogenicity for humans) based upon lack of evidence of 

carcinogenicity in rats and mice. 

Food Quality Protection Act (FQPA) Safety Factor (SF) Decision: The RAB1 risk assessment 

team determined that the FQPA SF can be reduced to 1X based on the following considerations: 

1) the toxicology database for bentazon is adequate for risk assessment; 2) bentazon is not 

considered neurotoxic; 3) all fetal and offspring effects are well characterized and protected for; 

and 4) the exposure databases are sufficient and unlikely to underestimate exposure.

Dose Response Assessment: The acute neurotoxicity screening battery in the rat was selected for 

the acute dietary endpoint for all populations [no-observed adverse-effect level (NOAEL) = 50 

mg/kg/day]. The two-generation reproductive study was selected for the chronic dietary 

endpoint for the general population, the incidental oral endpoint, and the inhalation endpoint 

(NOAEL = 15 mg/kg/day). Based upon a lack of effects in the 21-day dermal toxicity study, and 

the low dermal absorption values for bentazon (1-2%) in the guideline dermal penetration study, 

a quantitative dermal assessment is not required. Bentazon has been classified as a Group “E” 

chemical (evidence of non-carcinogenicity for humans) based upon lack of evidence of 

carcinogenicity in rats and mice (TXR 010787, J. Rowe, 1/14/92). Therefore, a cancer exposure 

and risk assessment is not required.
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Dietary Risk Estimates (Food + Drinking Water): Acute and chronic aggregate dietary (food 

and drinking water) exposure and risk assessments were conducted using the Dietary Exposure 

Evaluation Model - Food Consumption Intake Database (DEEM-FCID, ver. 3.16) which 

incorporates consumption data from United States Department of Agriculture (USDA) National 

Health and Nutrition Examination Survey, “What We Eat in America” (NHANES/WWEIA; 

2003-2008). The acute and chronic analyses assumed tolerance-level residues, 100% crop 

treated (CT), DEEM (ver. 7.81) default processing factors, and modeled drinking water 

estimates. The resulting acute and chronic dietary risk estimates are not of concern to HED, and 

the subgroups with the greatest risk estimates utilized ≤73% of the acute population-adjusted 

dose [aPAD; all infants (<1 year old)] and ≤78% of the chronic population-adjusted dose [cPAD; 

all infants (<1 year old)], respectively. 

Residential (Non-Occupational) Exposure and Risk Assessment: There is the potential for 

residential exposure from the registered uses on ornamentals and turf. These uses have been 

assessed using the most up-to-date exposure policies and data available in the 2012 Residential 

Standard Operating Procedures (SOPs). Since a dermal hazard was not identified, a quantitative 

dermal assessment was not conducted for the residential uses of bentazon. The inhalation 

exposure risk estimates for residential handlers are not of concern [i.e., margins of exposure 

(MOEs) ≥ the level of concern (LOC) of 100; 10X uncertainty factor (UF) for interspecies 

extrapolation, a 10X UF for intraspecies variability, and a 1X FQPA SF] at baseline for all 

scenarios. All residential post-application risk estimates are also not of concern (i.e., MOEs ≥ 

the LOC of 100). A quantitative spray drift assessment for bentazon is not required since the turf 

post-application MOEs are protective for any potential exposures related to spray drift for 

bentazon.

Aggregate-Risk Estimates: In accordance with FQPA, HED must consider and aggregate 

pesticide exposures and risks from three major sources: food, drinking water, and residential 

exposures. Acute, chronic, short-, and intermediate-term aggregate assessments were included in 

this risk assessment. An aggregate cancer risk assessment was not performed because bentazon is 

not considered to be a carcinogen. Acute and chronic aggregate risks are made up only of dietary 

sources; therefore, the exposure estimates provided in the dietary exposure analyses represent 

acute and chronic aggregate exposure, respectively. Short- and intermediate-term aggregate risks 

are made up of dietary and non-dietary sources of exposure. Since bentazon is used on turf, 

residential handler and post-application exposures are expected. Short-term exposures exist for 

adults and children from the registered turf application use; intermediate-term exposure is not 

anticipated, but since the short- and intermediate-term PODs are the same for bentazon, the shortterm aggregate is protective of longer-term exposures. All aggregate bentazon risk estimates are 

not of concern to HED. 

Occupational Exposure and Risk Assessment: There is the potential for occupational exposure 

from the registered uses of bentazon. These uses have been assessed using the most up-to-date 

exposure policies and data available. Since no dermal hazard was identified for bentazon, a 

quantitative dermal assessment was not conducted for the occupational uses of bentazon. The 

occupational handler exposure and risk estimates indicate that the short- and intermediate-term 

inhalation MOEs are not of concern to HED (i.e., MOE > the LOC of 100). Occupational postapplication dermal exposure and risk estimates were not quantitatively assessed since a dermal 

hazard was not identified. In this case, the restricted-entry interval (REI) is based on the acute 

toxicity of bentazon technical material, which would require a 24-hour REI under 40 CFR 

156.208 (c) (2). 
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Based on the Agency's current practices, a quantitative non-cancer occupational post-application 

inhalation exposure assessment was not performed for bentazon at this time. If new policies or 

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

occupational post-application inhalation exposure assessment for bentazon.

Environmental Justice Considerations: 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.”

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 (PHED) 1.1 and the Agricultural 

Handler Exposure Task Force (AHETF) database, are (1) subject to ethics review pursuant to 40 

CFR 26, (2) have received that review, and (3) are compliant with applicable ethics requirements. 

For certain studies, the ethics 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 the following 

Agency websites: http://www.epa.gov/pesticides/science/handler-exposure-data.html and 

http://www.epa.gov/pesticides/science/post-app-exposure-data.html. 

2.0 Recommendations

HED has examined the toxicology and residue chemistry databases for bentazon. There are no 

residue chemistry, residential, occupational, or toxicology data deficiencies that would preclude the 

continuation of permanent tolerances for residues of bentazon as outlined in Table 2.2.2.1. 

2.1 Data Deficiencies/Data Needs

None.

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

Plants: Adequate enforcement methods are available for the determination of residues of 

bentazon and its 6- and 8-hydroxy metabolites in/on plant commodities. The Pesticide 

Analytical Method Volume II (PAM II) lists Method II, a gas liquid chromatography (GLC) 

method with flame photometric detection for the determination of bentazon and its hydroxy 

metabolites in/on corn, rice, and soybeans; the limit of detection (LOD) for each compound is 

0.05 ppm. Method III, modified from Method II, is available for the determination of bentazon 

and its hydroxy metabolites in/on peanuts and seed and pod vegetables with a LOD of 0.05 ppm 

for each compound. A validated analytical method for enforcement of the residue definition is 

also available, with a combined limit of quantitation (LOQ) of 0.03 ppm in high water content, 

high oil content, acidic, and dry commodities 

(http://www.efsa.europa.eu/en/efsajournal/doc/2822.pdf).

Livestock: Adequate enforcement methods are available in PAM II for the determination of 

residues of bentazon and its metabolite 2-amino-N-isopropyl benzamide (AIBA) in livestock 

commodities. The methods involve quantification by gas chromatography with flame 
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photometric or nitrogen-specific Coulson conductivity detectors. LOQs range from 0.02 ppm in 

milk to 0.05 ppm for most other commodities. A validated analytical method for enforcement of 

the residue definition is available with an LOQ of 0.02 ppm for meat, milk, liver, and eggs 

(http://www.efsa.europa.eu/en/efsajournal/doc/2822.pdf).

The data requirements for multiresidue methods (MRMs) are fulfilled (MRID# 44227401). The 

FDA MRMs are not suitable as enforcement methods since bentazon residues of concern were 

not successfully recovered by the FDA MRMs.

2.2.2 Recommended Tolerances

Permanent tolerances have been established in 40 CFR §180.355 for the combined residues of 

bentazon, including its metabolites and degradates in/on various raw agricultural commodities 

(RACs) ranging from 0.05 ppm to 10.0 ppm.

The tolerance expression for bentazon residues in plant commodities [40 CFR §180.355(a)(1) and 40 

CFR §180.355(c)] should be updated to reflect current Agency policy as follows: 

“Tolerances are established for residues of bentazon, including its metabolites and degradates, in or 

on the commodities in the table below. Compliance with the tolerance levels specified below is to 

be determined by measuring only the sum of bentazon (3-(1-methylethyl)-1H-2,1,3-benzothiadiazin4(3H)-one 2,2-dioxide) and its metabolites 6-hydroxy bentazon (6-hydroxy-3-(1-methylethyl)-1H2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide) and 8-hydroxy bentazon (8-hydroxy-3-(1-

methylethyl)-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide), calculated as the stoichiometric 

equivalent of bentazon, in or on the following commodities:”

The tolerance expression for bentazon residues in livestock [40 CFR §180.355(a)(2)] commodities 

should be updated to reflect current Agency policy as follows: 

“Tolerances are established for residues of bentazon, including its metabolites and degradates, in or 

on the commodities in the table below. Compliance with the tolerance levels specified below is to 

be determined by measuring only the sum of bentazon (3-(1-methylethyl)-1H-2,1,3-benzothiadiazin4(3H)-one 2,2-dioxide) and its metabolite 2-amino-N-isopropyl benzamide, calculated as the 

stoichiometric equivalent of bentazon, in or on the following commodities:”

Table 2.2.2.1 is a summary of the established and HED-recommended tolerances for residues of 

bentazon. 

Table 2.2.2.1. Tolerance Summary for Bentazon (40 CFR §180.355).

Commodity

Established 

Tolerance 

(ppm)

HEDRecommended 

Tolerance (ppm)

Comments

(a) General. (1) Tolerances are established for the combined residues of the herbicide bentazon (3-isopropyl-1H-2,1,3-

benzothiadiazin-4(3H)-one-2,2-dioxide) and its 6- and 8-hydroxy metabolites in or on the following food commodities:

Bean, dry, seed 0.05 0.05

Bean, succulent 0.5 0.50

Corn, field, forage 3.0 3.0

Corn, field, grain 0.05 0.05

Corn, field, stover 3.0 3.0

Corn, pop, grain 0.05 0.05
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Table 2.2.2.1. Tolerance Summary for Bentazon (40 CFR §180.355).

Commodity

Established 

Tolerance 

(ppm)

HEDRecommended 

Tolerance (ppm)

Comments

Corn, sweet, kernel plus cob with 

husks removed 0.05 0.05

Cowpea, forage 10.0 10

Cowpea, hay 3.0 3.0

Flax, seed 1.0 1.0

Pea, dry, seed 1.0 1.0

Pea, field, hay 8.0 8.0

Pea, field, vines 3.0 3.0

Pea, succulent 3.0 3.0

Peanut 0.05 0.05

Peanut, hay 3.0 3.0

Pepper, nonbell 0.05 0.05

Peppermint, tops 1.0 1.0

Rice, grain 0.05 0.05

Rice, hulls 0.25 0.25

Rice, straw 3.0 3.0

Sorghum, grain, forage 0.20 0.20

Sorghum, grain, grain 0.05 0.05

Sorghum, grain, stover 0.05 0.05

Soybean, forage 8.0 8.0

Soybean, hay 8.0 8.0

Soybean, seed 0.05 0.05

Spearmint, tops 1.0 1.0

(2) Tolerances are established for the combined residues of the herbicide bentazon (3-isopropyl-1H-2,1,3-benzothiadiazin4(3H)-one-2,2-dioxide) and its metabolite 2-amino-N-isopropyl benzamide (AIBA) in or on the following food 

commodities:

Cattle, fat 0.05 0.05

Cattle, meat byproducts 0.05 0.05

Cattle, meat 0.05 0.05

Egg 0.05 0.05

Goat, fat 0.05 0.05

Goat, meat byproducts 0.05 0.05

Goat, meat 0.05 0.05

Hog, fat 0.05 0.05

Hog, meat byproducts 0.05 0.05

Hog, meat 0.05 0.05

Milk 0.02 0.02

Poultry, fat 0.05 0.05

Poultry, meat byproducts 0.05 0.05

Poultry, meat 0.05 0.05

Sheep, fat 0.05 0.05

Sheep, meat byproducts 0.05 0.05

Sheep, meat 0.05 0.05

(c) Tolerances with regional registrations. Tolerances with regional registration as defined in §180.1(m), are established 

for combined residues of the herbicide, bentazon (3-isopropyl-1H-2, 1,3-benzothiadiazin-4(3H)-one-2,2-dioxide) and its 6-

and 8-hydroxy metabolites in or on the following food commodities:

Clover, forage 1.0 1.0
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Table 2.2.2.1. Tolerance Summary for Bentazon (40 CFR §180.355).

Commodity

Established 

Tolerance 

(ppm)

HEDRecommended 

Tolerance (ppm)

Comments

Clover, hay 2.0 2.0

2.2.3 Revisions to Established Tolerances

The tolerance expressions for bentazon need to be updated to reflect current Agency policy (see 

Section 2.2.2). HED is not recommending for any changes in the tolerance levels at this time, 

although the values for cowpea, forage and bean, succulent should be updated to contain the 

appropriate number of significant figures.

2.2.4 International Harmonization

U.S. permanent tolerances (listed in 40 CFR 180.355) and Maximum Residue Limits (MRLs) are 

summarized in Appendix C. The U.S., Mexico, Canada, and Codex residue definitions for crops 

are harmonized. For some raw agricultural commodities, the tolerances and MRLs for the U.S., 

Canada, Mexico, and Codex are harmonized; however, there are several commodities for which 

the tolerance and MRLs are not harmonized. There are discrepancies between the U.S. residue 

definition and the Codex residue definition for livestock commodities. Harmonization of the 

tolerance/MRL levels is not possible as the U.S. use patterns require a higher tolerance or the 

MRL level is below the LOQ of the enforcement method. These discrepancies have been bolded 

in Appendix C. 

2.3 Label Recommendations

None.

3.0 Ingredient Profile

3.1 Chemical Identity

The chemical structure and nomenclature of bentazon are presented in Table 3.1.1. 

Table 3.1.1. Nomenclature for Bentazon.

Common Name Bentazon

Chemical Name (CAS) 3-(1-methylethyl)-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide

PC Codes 103901 bentazon sodium salt

275200 bentazon

Chemical Abstracts Nos. 50723-80-3, 25057-89-0

Registration Review Case 

No. 0182

Chemical Class Benzothiadiazinone herbicide
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Table 3.1.1. Nomenclature for Bentazon.

Chemical Structure

3.2 Physical/Chemical Properties

Bentazon is soluble (570 mg/L) in water. The vapor pressure (<1 x 10-7 mm Hg) and Henry's 

Law Constant (5.55 x 10-11 atm m3/mol) indicate that the compound is relatively non-volatile 

under field conditions. The n-octanol water partition coefficient (Log Kow = -0.46) for bentazon 

indicates a low potential for bioaccumulation. A table of the physical/chemical properties for 

bentazon is provided in Appendix B.

3.3 Use Pattern

There are 11 end-use product labels, and 4 special local need labels (SLNs), registered with 

bentazon as the active ingredient. All products are liquid formulations. The labeled use sites 

include various agricultural crops, non-bearing food crops, non-cropland sites, roadsides, rightsof-way, nursery stock, ornamentals, and turf (including athletic fields, commercial/residential 

settings, golf courses (not greens), recreational areas, and sod farms). Most of the uses are foliar, 

and are applied via aerial, groundboom, or handheld equipment. The maximum application rate 

supported by the registrants is 1.5 lb ai/A for any use site; however, most use sites have a 

maximum single application rate of 1 lb ai/A (0.023 lb ai/gal). A summary of the current use 

pattern is included in Table 3.3.1 below. 

Table 3.3.1. Summary of Proposed Directions for Use of Bentazon.

Crop/Use Site

Application 

Timing and 

Type of 

Application

Registered 

Formulations

Maximum 

Application 

Rate

Limitation and Restrictions Personal 

Protective 

Equipment 

(PPE) 

Max # 

apps/yr

Min RTI 

(days)

REI 

(hrs)

PHI 

(days)

Alfalfa (grown for 

seed production)

Prior to flower 

bud formation

Aerial, 

Groundboom

Soluble and 

Emulsifiable 

Concentrates

1.5 lb ai/A

2

5

48

NA Longsleeved 

shirt, long 

pants, 

gloves, 

shoes and 

socks; 

some 

labels 

require 

protective 

eyewear

Beans (dry and 

succulent)

Early 

postemergence

Aerial, 

Groundboom

1.5 lb ai/A NA 30

Clover (grown for 

seed)

Early 

postemergence

Aerial, 

Groundboom

1.0 lb ai/A 5 36
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Table 3.3.1. Summary of Proposed Directions for Use of Bentazon.

Crop/Use Site

Application 

Timing and 

Type of 

Application

Registered 

Formulations

Maximum 

Application 

Rate

Limitation and Restrictions Personal 

Protective 

Equipment 

(PPE) 

Max # 

apps/yr

Min RTI 

(days)

REI 

(hrs)

PHI 

(days)

Corn

Early 

postemergence

Aerial, 

Groundboom

1.5 lb ai/A NA 12

Flax

Early 

postemergence

Groundboom

1.0 lb ai/A NS 45

Non-bearing food 

crops (almonds, 

apples, apricots, 

avocados, 

blackberries, 

blueberries, cherries, 

crabapples, dates, 

figs, grapes, 

grapefruit, lemons, 

limes, macadamias, 

nectarines, olives, 

oranges, peaches, 

pears, pecans, 

pistachios, plums, 

pomegranates, 

prunes, raspberries, 

tangelos, tangerines, 

walnuts)

Postemergence 

directed 

Groundboom

1.0 lb ai/A NA NA

Non-cropland sites, 

Roadsides, Rightsof-way

Postemergence 

Groundboom, 

Handheld

1 lb ai/A; 

0.023 lb 

ai/gal

7 NA

Nursery stock

Postemergence 

Groundboom, 

Handheld

1 lb ai/A; 

0.023 lb 

ai/gal

7 NA

Ornamentals 

Postemergence 

Groundboom, 

Handheld

1 lb ai/A; 

0.023 lb 

ai/gal

7 NA

Peanuts

Range from 

cracking 

through 

pegging

Aerial, 

Groundboom

1.5 lb ai/A NA 50

Peas (dry and 

succulent)

After 3 pairs of 

leaves are 

present, do not 

apply when 

peas are in 

bloom

Aerial, 

Groundboom

1.5 lb ai/A NA

dry peas 

= 30, 

succulen

t peas = 

10

Peppermint/ 

Spearmint

Postemergence

Aerial, 

Groundboom

1.5 lb ai/A NA 20
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Table 3.3.1. Summary of Proposed Directions for Use of Bentazon.

Crop/Use Site

Application 

Timing and 

Type of 

Application

Registered 

Formulations

Maximum 

Application 

Rate

Limitation and Restrictions Personal 

Protective 

Equipment 

(PPE) 

Max # 

apps/yr

Min RTI 

(days)

REI 

(hrs)

PHI 

(days)

Rice

Postemergence

Aerial, 

Groundboom

1.0 lb ai/A NA NA

Sorghum

Postemergence 

(but not during 

crop heading 

or blooming)

Aerial, 

Groundboom

1.0 lb ai/A NA 12

Soybeans

Postemergence

Aerial, 

Groundboom

1.5 lb ai/A NA 30

Turf (athletic fields, 

commercial/residenti

al settings, golf 

courses (not greens), 

recreational areas, 

sod farms)

Postemergence 

Groundboom, 

Handheld

1 lb ai/A; 

0.023 lb 

ai/gal

21 

(perennia

l 

ryegrass)

NA

3.4 Anticipated Exposure Pathways

Based on the registered bentazon application scenarios, dietary exposure is an anticipated 

exposure pathway as residues of bentazon may be found in/on crops, livestock commodities, and 

drinking water. There are residential uses of bentazon and potential for spray drift, so there is 

exposure in residential and non-occupational settings. In an occupational setting, applicators 

may be exposed while handling the pesticide prior to application, as well as during application. 

There is also potential for post-application exposure for workers re-entering treated sites. This 

risk assessment considers all of the aforementioned exposure pathways based on the existing 

uses of bentazon.

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://epa.gov/environmentaljustice/resources/policy/exec_order_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 

NHANES/WWEIA (2003-2008), and are used in pesticide risk assessments for all registered 

food uses of a pesticide. These data are analyzed and categorized by subgroups based on age,

season of the year, ethnic group, and region of the country. Additionally, OPP is able to assess 

dietary exposure to smaller, specialized subgroups and exposure assessments are performed 

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

on home use of pesticide products and associated risks for adult applicators and for toddlers, 
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youths, and adults entering or playing on treated areas post-application are evaluated. Further 

considerations are currently in development as OPP has committed resources and expertise to the 

development of specialized software and models that consider exposure to bystanders and farm 

workers as well as lifestyle and traditional dietary patterns among specific subgroups.

4.0 Hazard Characterization and Dose-Response Assessment

Bentazon is a benzothiadiazinone contact herbicide that is manufactured by the BASF 

Corporation. Its herbicidal mode of action in plants is through inhibition of photosynthesis via 

inhibition of photosystem II (PS II). In mammals, bentazon’s effects are predominantly on the 

hematopoietic system.

4.1 Toxicology Studies Available for Analysis

The toxicological database for bentazon is complete for risk assessment purposes. Since the last 

risk assessment, the regulatory decisions for the developmental rat and chronic dog studies were 

updated for consistency with the agency’s current policies resulting in revised NOAEL and 

lowest-observed adverse-effect level (LOAEL) values (Dunbar et al., 01-OCT-14, D433967). 

The neurotoxicity screening batteries and a 28-day rat immunotoxicity study have been 

submitted to the Agency and reviewed. In addition, HED’s Hazard Science and Policy Council 

(HASPOC) met on September 11, 2014 (TXR# 0057054) to evaluate the need for a repeated 

exposure inhalation toxicity study for bentazon. The HASPOC concluded that based on a 

weight-of-evidence (WOE) approach considering all hazard and exposure data for bentazon, that 

a subchronic rat inhalation study was not required at this time. The results of the three newly 

submitted studies and revised regulatory decisions are included in this hazard assessment. 

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

The ADME for bentazon is well characterized using a series of available studies. In an initial 

study comparing sodium bentazon and the free acid at a single oral dose of 4 mg/kg, the 

absorption and excretion of both forms appeared to be rapid and essentially equivalent based on 

(1) similar peak plasma concentration values (Cmax; 5.08 and 4.87 ug equivalents, respectively), 

(2) similar time to maximum concentrations (Tmax; 0.77 and 1.18 hours, respectively) and (3) 

similar half-life values (T1/2; 3.36 and 3 - 10 hours, respectively). Area under the curve (AUC) 

values (0.0626 and 0.0680 ug x hr/ml/mg/kg) were similar as well. No sex differences in 

patterns of excretion (>90% in urine) or urinary metabolite profiles were observed (>80% as free 

acid). At sacrifice, total radioactive residue in the carcass was less than 0.69% of the dose in all 

groups. 

In a second study, sodium bentazon and the free acid were administered using single and 

repeated oral dosing, intravenous (i.v.) dosing, and bile cannulation protocols at low- and highdoses (~4 and 200 mg/kg). For the most part, there was no difference in the above measured 

parameters for route of administration (oral vs. i.v.) and for magnitude of dose. AUC values 

were increased ~2 - 3-fold when comparing the low- and high- dose groups. Biliary excretion of 

radioactivity amounted to only 0.24 - 1.31% and 0.80 - 1.84% of the administered doses for the 

low- and high-dose groups respectively. The majority of radioactivity was eliminated within the 

first 24 hours (~91%). Parent bentazon was the major residue found in urine, amounting to 

77.37 - 91.02% of the dose among the orally dosed animals of the main experiment. A small 

amount of benzene ring hydroxylation was observed; 6-OH-bentazon was present in amounts up 
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to 6.34% of the dose, and the isomeric 8-OH-bentazon was present in trace amounts, 0 - 0.23% 

of the dose. 

4.2.1 Dermal Absorption

In a dermal-penetration study in rats, a single topical application of radioactive sodium bentazon 

in an aqueous solution was applied to the backs of male Sprague Dawley rats (24/dose level) at 

doses of 0.12, 1.2, 12.0, or 120.0 mg/kg (0.002, 0.02, 0.2, or 2.0 mg free acid/cm2). Sodium 

bentazon did not appear to significantly penetrate the skin after 10 hours of exposure since a 

maximum of only 1 - 2% of the radioactivity was recovered (primarily in the urine) at 72 hours 

post-exposure. The dermal penetration factor was estimated to be 2% (sum of tissues, carcass, 

and excreta) for risk assessment purposes.

4.3 Toxicological Effects

In subchronic studies in rats and dogs and in chronic studies in all species, the most 

toxicologically significant effects were changes in hematological/coagulation parameters 

following bentazon administration through the oral route. In rats, subchronic oral exposure 

caused increased thromboplastin and prothrombin times (PT). In dogs, hemoglobin, hematocrit, 

and erythrocyte counts were significantly reduced in animals at both 6 weeks and at term. PT 

and reticulocytes were also elevated. 

The effects in the chronic studies in rats, mice and dogs were similar to those in subchronic 

studies. In a chronic/oncogenicity study in mice, PT were elevated. In addition, the incidence of 

hemorrhage in liver and heart was increased. In a chronic/oncogenicity study in rats, partial 

thromboplastin times (PTT) were elevated. In a one-year feeding study in dogs, at the highest 

dose tested, there were clinical signs (emaciation, dehydration, bloody stool, pale mucous 

membranes, moderated activity) and a slight to severe anemia (decreased hemoglobin, 

hematocrit, and erythrocyte count, decreased reticulocytes, platelets, leukocytes, PTT), and 

abnormal red cell morphology) during the first 13 weeks.

In rats and rabbits, fetal effects occurred at doses that caused maternal toxicity. In the rat 

developmental toxicity study, maternal effects consisted of increased post-implantation loss and 

fetal resorptions, and developmental effects consisted of skeletal variations and reduced fetal 

weights. In the rabbit developmental toxicity study, at the highest dose tested, maternal effects 

consisted of partial abortions with resorptions, and developmental effects consisted of an 

increased incidence of no living fetuses. 

In the two-generation reproductive toxicity study in rats, there was increased quantitative 

offspring susceptibility. Offspring toxicity manifested as reduced absolute pup weights (≥5%) 

during lactation at a dose lower than where parental systemic toxicity was observed. The sole 

parental effect was an increased incidence of kidney mineralization and liver microgranuloma. 

There were no effects on reproductive parameters.

In the acute neurotoxicity study, effects observed at the mid- and high-dose groups consisted of 

decreased motor activity in males on day 0. There were no effects in the subchronic neurotoxicity 

study, and bentazon was negative for immunotoxicity. In a 21-day dermal toxicity study, no effects 

were observed up to 1000 mg/kg/day.
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Bentazon was not found to be mutagenic, and is classified as a Group “E” chemical (evidence of 

non-carcinogenicity for humans) based upon lack of evidence of carcinogenicity in rats and 

mice. 

Based on acute toxicity data, bentazon is categorized as having low lethality by the oral, 

inhalation, and dermal routes of exposure (Toxicity Categories III and IV). It is moderately 

irritating to the eye (Toxicity Category II) and slightly irritating to the skin (Toxicity Category 

III). Bentazon is also a dermal sensitizer.

4.4 Safety Factor for Infants and Children (FQPA SF)

The RAB1 risk assessment team determined that the FQPA SF can be reduced to 1X based on 

the following considerations described in greater detail in the sections below: 1) the toxicology 

database for bentazon is adequate for risk assessment; 2) bentazon is not considered neurotoxic; 

3) all fetal and offspring effects are well characterized and protected for; and 4) the exposure 

databases are sufficient and unlikely to underestimate exposure.

4.4.1 Completeness of the Toxicology Database

The existing toxicology database for bentazon is adequate for FQPA evaluation. Developmental 

toxicity studies in rats and rabbits, a two-generation reproduction study in rats, and neurotoxicity 

studies in rats are available for FQPA consideration.

4.4.2 Evidence of Neurotoxicity

The nervous system is not the target organ for bentazon, and the effects observed are well 

characterized. In the acute neurotoxicity study, a clear NOAEL was established for the effect 

observed (decreased motor activity), and this study is being used in endpoint selection. There 

was no evidence of neurotoxicity observed in the rest of the toxicology database, including the 

subchronic neurotoxicity study.

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

There are no concerns or residual uncertainties for pre- and post-natal toxicity. There is evidence 

of increased quantitative offspring susceptibility in the two-generation reproduction toxicity 

study (see Section 4.2); however, the concern is low since: 1) a clear NOAEL is established in 

the offspring; 2) the dose-response for these effects are well defined and characterized; and 3) 

endpoints selected for risk assessment are protective of the observed offspring and 

developmental effects.

4.4.4 Residual Uncertainty in the Exposure Database

There are no residual uncertainties in the exposure database. The dietary and residential 

exposure analyses are conservative in nature. The dietary exposure assessment used tolerancelevel residues and assumed 100% CT. The residential exposure assessment uses the 2012 

Residential SOPs and is considered health-protective. 
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4.5 Toxicity Endpoints and Point of Departure Selections

4.5.1 Dose-Response Assessment

Since the last risk assessment for bentazon, the regulatory decisions for the developmental rat and 

chronic dog studies have been updated to be consistent with the agency’s current policies. The 

changes in these decisions and the submission of new data to the hazard database have led to 

revision of the previous endpoints. The PODs, UFs, and toxicity endpoints for dietary exposure 

assessment and occupational/residential exposure assessments are presented in Tables 4.4.1 and 

4.4.2, respectively. 

Acute Dietary Endpoint (All Populations): The acute neurotoxicity screening battery in the rat was 

selected for the acute dietary endpoint for all populations. An UF of 100X, which includes a 10X

for interspecies extrapolation, a 10X for intraspecies variability, and a 1X FQPA SF was applied to 

the NOAEL of 50 mg/kg to generate an aPAD of 0.5 mg/kg for the general population. The 

LOAEL is 150 mg/kg based on decreased motor activity in males on day 0. This study is protective 

of the general population and is appropriate for the expected duration of exposure.

Chronic Dietary Endpoint (All populations): The two-generation reproductive study was selected 

for the chronic dietary endpoint. An UF of 100X, which includes a 10X for interspecies 

extrapolation, a 10X for intraspecies variability, and a 1X FQPA SF was applied to the NOAEL of 

15 mg/kg/day to generate the cPAD of 0.15 mg/kg/day. The LOAEL is 62 mg/kg/day based upon 

decreased absolute offspring body weights during lactation. NOAEL and LOAEL values for all 

chronic oral exposure studies were similar across studies. The NOAEL from the two-generation

reproductive study is considered protective of all effects seen in the longer term studies and it was 

selected based upon dose spacing considerations. This study is protective of all populations.

Dermal Endpoints for all Durations: Based upon a lack of effects in the 21-day dermal toxicity 

study, and the low dermal absorption values for bentazon (1-2%) in the guideline dermal 

penetration study, a dermal risk assessment is not required. Dermal equivalent doses calculated 

using potentially relevant oral doses from the bentazon database result in values that are well 

above the limit dose. 

Short- and Intermediate-Term Incidental Oral Endpoints: Similar to the chronic dietary 

endpoint for the general population, the offspring effects for the two-generation reproductive 

study were chosen for the short- and intermediate-term incidental oral exposure scenarios. The 

LOC is 100 based upon a 10X UF for interspecies extrapolation, a 10X UF for intraspecies 

variability, and a 1X FQPA SF. This study is appropriate for the population of concern (young 

children) and for the expected durations of exposure.

Short- and Intermediate-Term Inhalation Endpoints: Similar to the chronic dietary endpoint for 

the general population, the offspring effects for the two-generation reproductive study were 

chosen for the short- and intermediate-term inhalation exposure scenarios. The LOC for the 

inhalation exposure scenarios is 100 based upon a 10X UF for interspecies extrapolation, a 10X

UF for intraspecies variability, and a 1X FQPA SF (when applicable). The NOAEL from this 

study is protective of offspring effects that may result from exposure to pregnant and nursing 

females as well as adult effects seen throughout the database in subchronic and chronic studies.

Inhalation exposure is assumed to be equivalent to oral exposure. 
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4.5.2 Recommendation for Combining Routes of Exposures for Risk Assessment

Since the same study and effects (reproduction and fertility effects in the rat; decreased absolute 

pup body weights during lactation) were used to select the PODs for the inhalation and incidental 

oral exposure routes, these routes should be combined. A dermal hazard was not identified; 

therefore, this route of exposure is not combined with the inhalation or incidental oral routes. 

4.5.3 Cancer Classification and Risk Assessment Recommendation

Bentazon has been classified as a Group “E” chemical (evidence of non-carcinogenicity for 

humans) based upon lack of evidence of carcinogenicity in rats and mice (TXR 010787, J. Rowe, 

1/14/92). Therefore, a cancer exposure and risk assessment is not required.

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

Risk Assessment

Table 4.5.4.1. Summary of Toxicological Doses and Endpoints for Bentazon for Use in Dietary and NonOccupational Human Health Risk Assessments.

Exposure/ 

Scenario POD Uncertainty/FQPA SFs

RfD, PAD, LOC 

for Risk 

Assessment

Study and Toxicological Effects

Acute Dietary 

(General 

Population, 

including 

Infants and 

Children)

NOAEL =

50 

mg/kg/day

UFA = 10X

UFH =10X

FQPA SF = 1X

Acute RfD = 0.5 

mg/kg/day

aPAD = 0.05 

mg/kg/day

Acute Neurotoxicity- Rat

LOAEL = 150 mg/kg/day based on 

decreased motor activity in males on 

study day 0.

Chronic 

Dietary (All 

Populations)

NOAEL= 15 

mg/kg/day

UFA = 10X

UFH = 10X

FQPA SF = 1X

Chronic RfD = 

0.15

mg/kg/day

cPAD = 0.15 

mg/kg/day

Reproduction and fertility effects -

Rat

Offspring LOAEL = 62 mg/kg/day 

based on decreased absolute pup 

body weights during lactation.

Incidental 

Oral Short-

(1-30 days) 

and 

Intermediate –

Term (1-6 

months)

NOAEL= 15 

mg/kg/day

UFA = 10X

UFH = 10X

FQPA S F= 1X

Residential LOC 

for MOE = 100

Reproduction and fertility effects -

Rat

Offspring LOAEL = 62 mg/kg/day 

based on decreased absolute pup 

body weights during lactation.

Dermal Short-

(1-30 days) 

and 

IntermediateTerm (1-6 

months)

Based upon a lack of dermal toxicity in the 21-day dermal study, and the low absorption values 

for bentazon (1-2%), a dermal risk assessment is not required.

Inhalation 

Short- (1-30 

days) and 

IntermediateTerm (1-6 

months)

NOAEL= 15 

mg/kg/day

UFA = 10X

UFH = 10X

FQPA SF = 1X

Residential LOC 

for MOE = 100

Reproduction and fertility effects -

Rat

Offspring LOAEL = 62 mg/kg/day 

based on decreased absolute pup 

body weights during lactation.

Cancer (oral, 

dermal, 

inhalation)

Classification: Bentazon has been classified as a Group “E” chemical (evidence of noncarcinogenicity for humans) based upon lack of evidence of carcinogenicity in rats and mice 

(TXR 010787, J. Rowe, 1/14/92). Therefore, a cancer exposure and risk assessment is not 

required.
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Point of departure (POD) = A data point or an estimated point that is derived from observed dose-response data and 

used to mark the beginning of extrapolation to determine risk associated with lower environmentally relevant human 

exposures. NOAEL = no-observed adverse-effect level. LOAEL = lowest-observed adverse-effect level. UF = 

uncertainty factor. UFA = extrapolation from animal to human (interspecies). UF = uncertainty factor. UFA = 

extrapolation from animal to human (interspecies). UFH = potential variation in sensitivity among members of the 

human population (intraspecies). FQPA SF = FQPA Safety Factor. PAD = population-adjusted dose (a = acute, c = 

chronic). RfD = reference dose. 

Table 4.5.4.2. Summary of Toxicological Doses and Endpoints for Bentazon for Use in Occupational 

Human Health Risk Assessments.

Exposure/ 

Scenario POD UFs LOC for Risk Assessment Study and Toxicological Effects

Dermal Short-

(1-30 days) 

and 

IntermediateTerm (1-6 

months)

Based upon a lack of dermal toxicity in the 21-day dermal study, and the low absorption values 

for bentazon (1-2%), a dermal risk assessment is not required.

Inhalation 

Short- (1-30 

days) and 

IntermediateTerm (1-6 

months)

NOAEL= 

15 

mg/kg/day

UFA=10X

UFH=10X

Occupational 

LOC for MOE = 

100

Reproduction and fertility effects - Rat

Offspring LOAEL = 62 mg/kg/day based 

on decreased absolute pup body weights 

during lactation.

Cancer (oral, 

dermal, 

inhalation)

Classification: Bentazon has been classified as a Group “E” chemical (evidence of noncarcinogenicity for humans) based upon lack of evidence of carcinogenicity in rats and mice 

(TXR 010787, J. Rowe, 1/14/92). Therefore, a cancer exposure and risk assessment is not 

required.

Point of departure (POD) = A data point or an estimated point that is derived from observed dose-response data and 

used to mark the beginning of extrapolation to determine risk associated with lower environmentally relevant human 

exposures. NOAEL = no-observed adverse-effect level. LOAEL = lowest-observed adverse-effect level. UF = 

uncertainty factor. UFA = extrapolation from animal to human (interspecies). UFH = potential variation in 

sensitivity among members of the human population (intraspecies). MOE = margin of exposure. LOC = level of 

concern. 

4.6 Endocrine Disruptor Screening Program

As required by Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and Federal Food, 

Drug, and Cosmetic Act (FFDCA), EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic, and 

chronic toxicity, including assessments of 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 Registration Review decision for bentazon, 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), bentazon 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 
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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, 20131and 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. 

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.2

5.0 Dietary Exposure and Risk Assessment

D418592, G. Kramer, 02-DEC-2014 (dietary-exposure analysis for the current action)

D422778, S. Wente, 11-SEP-2014 (determination of degradates of concern drinking water)

5.1 Metabolite/Degradate Residue Profile

5.1.1 Summary of Plant and Animal Metabolism Studies

The qualitative nature of the residue in plants is considered to be adequately understood (see 

2/7/94 RED Chapter). Radiolabeled studies conducted at rates of up to 2.5 lb ai/A on beans, 

corn, soybeans, rice, and wheat indicate that bentazon is readily absorbed from foliage, roots 

and seeds, and translocates in some plant types. Bentazon is rapidly metabolized, 

conjugated, and incorporated into natural plant constituents. Metabolism involves the 

hydroxylation of bentazon at the 6- and 8-position. The terminal residues of regulatory 

concern are bentazon, 6-hydroxy bentazon, and 8-hydroxy bentazon. 

The qualitative nature of the residue in livestock is also considered to be adequately 

understood (see 2/7/94 RED Chapter). When dairy cattle were orally dosed with 

radiolabeled bentazon at levels of up to 20 ppm for 28 days, analysis showed that it was 

absorbed and rapidly eliminated in the urine. Bentazon and its metabolite, AIBA, are the 

regulated terminal residues in tissues and milk. Studies involving laying hens dosed with 

radiolabeled bentazon at 100 ppm in the diet for 5 days demonstrated that limited 

accumulation and metabolism occurs. Greater than 80% of the total radioactive residue 

(TRR) in tissue and eggs was identified as unchanged bentazon. The highest radioactive 

residue levels were found in the liver, and 16% of the TRR in liver consisted of the Nglucuronide conjugate of bentazon. Bentazon and AIBA are the regulated terminal residues 

 

1

See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals.

2 See http://www.epa.gov/endo/.
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in poultry commodities. 

5.1.2 Summary of Environmental Degradation

Dissipation of bentazon is dependent on microbe-induced degradation, leaching and surface water 

runoff. Bentazon is moderately resistant to degradation in aerobic mineral soils. Degradation in 

aquatic environments is dependent on photolysis. Degradation in soil is controlled by processes 

involving microbes in the presence of oxygen. Bentazon has a low binding affinity to soil and, 

therefore, may leach into ground water and runoff into surface waters. Leaching did not appear to 

be a major route of dissipation in field studies, however. Bentazon dissipates rapidly under typical 

use conditions. The soil degradates of bentazon include AIBA, which is very mobile but not 

persistent, and N-methylbentazon, which is not mobile. 

5.1.3 Comparison of Metabolic Pathways

In plants, bentazon is rapidly metabolized, conjugated, and incorporated into natural plant 

constituents. Metabolism involves the hydroxylation of bentazon at the 6- and 8-position. In 

animals, metabolism of bentazon is much more limited. AIBA is a major metabolite in ruminants; 

and the N-glucuronide conjugate of bentazon, in poultry. Trace amounts of 6-OH-bentazon and 8-

OH-bentazon are formed in rats. AIBA is also the major environmental degradate.

5.1.4 Residues of Concern Summary

The residues of concern in primary crops, rotational crops, livestock, and drinking water, as 

identified by HED, are shown in Table 5.1.4 below.

Table 5.1.4. Summary of Metabolites and Degradates to be Included in the Risk Assessment.

Matrix Residues Included in Risk 

Assessment

Residues Included in 

Tolerance Expression

Plants

Primary Crops Bentazon, 6-hydroxy Bentazon, 

and 8-hydroxy Bentazon

Bentazon, 6-hydroxy 

Bentazon, and 8-hydroxy 

Rotational Crops Bentazon, 6 Bentazon -hydroxy Bentazon, 

and 8-hydroxy Bentazon

Livestock

Ruminants

Bentazon and AIBA Bentazon and AIBA

Poultry

Drinking Water

Bentazon, AIBA, O-nitro-Nisopropyl benzamide, O-nitrosoN-isopropylbenzamide, 

photoproduct 10, and 8-Clbentazon

Not Applicable

5.2 Food Residue Profile

A tolerance is currently established under 40 CFR §180.355(a)(1) for the combined residues of 

bentazon and its 6- and 8-hydroxy metabolites, in/on dry and succulent bean, corn, cowpea, flax, 

dry and succulent pea, peanut, pepper, peppermint, rice, sorghum, soybean, and spearmint from 

0.05 to 10.0 ppm. In addition, permanent tolerances are established under 40 CFR §180.355 (a)(2) 

for the combined residues of bentazon and its metabolite AIBA in/on several livestock 

commodities at 0.05 ppm. Tolerances for the combined residues of bentazon and its 6- and 8-

hydroxy metabolites have been established under 40 CFR §180.355(c) in connection with regional 
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registrations; these include tolerances for residues in/on clover, forage at 1.0 ppm, and clover, hay 

at 2.0 ppm. 

The available crop and livestock magnitude of the residue data for bentazon are adequate to 

support the use on all registered crops. The field trial data reflect the proposed use patterns; an 

adequate number of trials were conducted in the appropriate geographic regions; and samples were 

analyzed for the residue of concern using validated data-collection methods. The storage intervals 

were also validated. Confined rotational crop data indicate that bentazon residues (bentazon, 6-

hydroxy bentazon, and 8-hydroxy bentazon) may be taken up by rotational crops (39- to 102-day 

plantback intervals); however, field rotational crop studies demonstrate that plantback 

restrictions/tolerances for indirect or inadvertent residues for bentazon are not needed (MRIDs 

4114666-01 to -08). 

5.3 Drinking Water Residue Profile

Drinking water residues provided by EFED (Memo, S. Wente, 11-SEP-2014; D422778) were 

incorporated directly into the acute and chronic dietary analyses as “water, direct, all sources” 

and “water, indirect, all sources.” The estimated drinking water concentrations (EDWCs) were 

Tier 1 estimates for ground water using the Tier 1 Rice Model. Based on two applications of 1.1 

lbs ai/acre for a total application of 2.2 lbs ai/acre/year and a Kd of 0.898 (MRID 40470501), the 

Tier 1 Rice Model produces a surface water EDWC of 2112 μg/L for both acute and chronic risk 

concerns. Therefore, EFED believes all of the other uses of bentazon would produce EDWCs 

lower than this conservative value for both surface and groundwater.

5.4 Dietary (Food + Drinking Water) Risk Assessment

Acute and chronic aggregate dietary (food and drinking water) exposure and risk assessments 

were conducted using DEEM-FCID, ver. 3.16 which incorporates consumption data from the 

USDA NHANES/WWEIA; 2003-2008. The acute and chronic analyses assumed tolerance-level 

residues, 100% CT, DEEM (ver. 7.81) default processing factors, and modeled drinking water 

estimates. The resulting acute food plus water risk estimates are below HED’s LOC (<100% 

aPAD) at the 95th percentile of the exposure distribution for the general U.S. population (23% 

aPAD), and all population subgroups. The population subgroup with the greatest acute risk 

estimate was all infants (<1 year old), which utilized 73% of the aPAD. The resulting chronic 

risk estimates are also below HED’s LOC for the U.S. general population (<100% cPAD), and 

all population subgroups. The most highly exposed population was all infants (<1 year old), 

with a chronic risk estimated that utilized 78% of the cPAD. 
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Table 5.4.1. Summary of Dietary (Food and Drinking Water) Exposure Risk for Bentazon.

Population Subgroup

Acute Dietary

(95th Percentile) Chronic Dietary

Dietary Exposure 

(mg/kg/day) % aPAD Dietary Exposure(mg/kg/day) % cPAD

General U.S. Population 0.115806 23 0.044888 30

All Infants (<1 year old) 0.365354 73 0.116618 78

Children 1-2 years old 0.180165 36 0.066256 44

Children 3-5 years old 0.146590 29 0.055447 37

Children 6-12 years old 0.110968 22 0.039685 26

Youth 13-19 years old 0.096321 19 0.032767 22

Adults 20-49 years old 0.113997 23 0.044599 30

Adults 50-99 years old 0.101622 20 0.044111 29

Females 13-49 years old 0.115326 23 0.044424 30

*The values for the highest exposed population for each type of risk assessment are bolded.

6.0 Residential (Non-Occupational) Exposure/Risk Characterization

D418591, K. Lowe, 02-DEC-2014

There is the potential for residential handler and post-application exposure from the registered 

uses on turf and ornamentals.

6.1 Residential Handler Exposure/Risk Estimates

The quantitative exposure/risk assessment developed for residential handlers is based on the 

following scenarios: 

(1) mixing/loading/applying liquids to turf and gardens/trees with manually-pressurized 

handwand, 

(2) mixing/loading/applying liquids to turf and gardens/trees with hose-end sprayer, and

(3) mixing/loading/applying liquids turf and gardens/trees with backpack.

Table 6.1.1 provides a summary of the residential handler exposures and risk estimates for 

bentazon. Since there is no dermal hazard, a quantitative residential handler dermal assessment 

has not been conducted. The inhalation exposure risk estimates for residential handlers are not 

of concern (i.e., MOEs ≥ 100) at baseline for all scenarios; all MOEs are ≥ 75,000. 

Table 6.1.1. Residential Handler Non-cancer Exposure and Risk Estimates for Bentazon.

Scenario Application 

Equipment/Method

Application 

Rate1

Area 

Treated or 

Amount 

Handled 

Daily

Inhalation 

Unit 

Exposure 

(mg/lb ai)2

Inhalation 

Dose 

(mg/kg/day)3

Inhalation 

MOE4

Mixer/Loader/Applicator for Liquid Formulations

Gardens / Trees Manuallypressurized 

handwand

0.023 lb 

ai/gallon 5 gallons 0.018 0.000026 580,000 Lawns / Turf

Gardens / Trees Hose-end Sprayer

0.023 lb 

ai/gallon 11 gallons 0.0014 0.0000044 3,400,000

Lawns / Turf 1 lb ai/acre 0.5 acres 0.022 0.00014 110,000

Gardens / Trees Backpack 0.023 lb 

ai/gallon 5 gallons 0.14 0.0002 75,000 Lawns / Turf

1. Based on registered labels (see Table 3.3.1).

2. Based on HED’s 2012 Residential SOPs (http://www.epa.gov/pesticides/science/residential-exposure-sop.html).
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3. Inhalation Dose = Inhalation Unit Exposure (mg/lb ai) × Application Rate (lb ai/acre or gal) × Area Treated or Amount Handled (A/day or 

gallons/day) ÷ Body Weight (80 kg).

4. Inhalation MOE = Inhalation NOAEL (15 mg/kg/day) ÷ Inhalation Dose (mg/kg/day).

6.2 Residential Post-application Exposure/Risk Estimates

The quantitative exposure/risk assessment for residential post-application exposures is based on 

the following scenarios: 

 Physical activities on turf: children 1 to < 2 years old (incidental oral).

The lifestages selected for each post-application scenario are based on an analysis provided as an 

Appendix in the 2012 Residential SOPs3. 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.

Table 6.2.1 provides a summary of the residential post-application exposures and risk estimates 

for bentazon. All risk estimates for post-application exposure are not of concern (i.e., MOEs ≥ 

100); all MOEs are ≥ 1000 for children. 

Table 6.2.1. Short-Term Residential Post-application Exposure and Risk Estimates for Bentazon.

Lifestage Post-application Exposure Scenario Dose 

(mg/kg/day)1 MOEs2

Child 

1 to< 2 year old

Turf

Liquid formulation

1 lb ai/A

Hand to Mouth 0.0152 1000

Object to Mouth 0.000456 32,000

Short- and Intermediate-term Incidental Soil 

Ingestion 3.4E-05 440,000

1. Dose (mg/kg/day) equations provided in HED’s 2012 Residential SOPs (http://www.epa.gov/pesticides/science/residential-exposure-sop.html).

2. MOE = POD (incidental oral = 15 mg/kg/day) ÷ Dose (mg/kg/day). LOC = 100.

6.3 Residential Risk Estimates for Use in Aggregate Assessment

Table 6.3.1 reflects the residential risk estimates that are recommended for use in the aggregate 

assessment for bentazon.

 The recommended residential exposure for use in the adult short-term aggregate 

assessment reflects inhalation exposure from handler applications using a backpack 

sprayer.

 The recommended residential exposure for use in the children 1 to < 2 years old shortterm aggregate assessment reflects hand-to-mouth exposures from post-application 

exposure to turf applications.

Table 6.3.1. Recommendations for the Residential Exposures for the Bentazon Aggregate Assessment.

Lifestage Exposure 

Scenario

Dose (mg/kg/day)1 MOE2

Dermal Inhalation Oral Total Dermal Inhalation Oral Total

Short-term

Adult

Handler 

application 

via 

backpack 

sprayer

NA 0.0002 NA 0.0002 NA 75,000 NA 75,000

 

3 Available: http://www.epa.gov/pesticides/science/residential-exposure-sop.html
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Table 6.3.1. Recommendations for the Residential Exposures for the Bentazon Aggregate Assessment.

Lifestage Exposure 

Scenario

Dose (mg/kg/day)1 MOE2

Dermal Inhalation Oral Total Dermal Inhalation Oral Total

Child 1 to < 

2 years old

Hand-tomouth NA NA 0.0152 0.0152 NA NA 1000 1000

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

applicable).

2. MOE = the MOEs associated with the highest residential doses. 

6.4 Spray Drift

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 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 coupled with methods employed for 

residential risk assessments for turf products.

The approach to be used for quantitatively incorporating spray drift into risk assessment include 

assessing 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 exposure scenario. 

Aside from the predicted residues available for transfer, the routes of exposure and assessment 

methodology is analogous to how exposures to turf products are considered in risk assessment. 

Several bentazon products have existing labels for use on turf, thus it was considered whether the 

risk assessment for turf may be considered protective of any type of exposure resulting from 

spray drift. If the maximum application rate on crops adjusted by the amount of drift expected is 

less than or equal to existing turf application rates, the existing turf assessment is considered 

protective of spray drift exposure. The maximum single application rate registered for bentazon

is 1.5 lb ai/A. The highest fraction of spray drift noted for any application method immediately 

adjacent to a treated field results in a deposition fraction of 0.264of the application rate. A 

quantitative spray drift assessment for bentazon is not required because the maximum application 

rate for a crop/target site multiplied by the adjustment factor for drift of 0.26 is less than the 

maximum direct spray residential turf application rate (1 lb ai/A)5for any bentazon products. 

The turf post-application MOEs are protective for any potential exposures related to spray drift 

for bentazon and have previously been discussed in Section 6.2. 

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 FIFRA Scientific Advisory Panel (SAP) in 

December 2009, and received the SAP’s final report on March 2, 2010 

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

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

Volatilization Screening Analysis (http://www.regulations.gov/#!docketDetail;D=EPA-HQ-

 

4 Tier 1 output from the aerial application using fine to medium spray quality based on AgDrift® output files.

5 1.5 lb ai/A x 0.26 = 0.39 ≤ 1 lb ai/A.
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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 

bentazon.

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

Acute aggregate risk results from exposure to residues in food and drinking water alone. The 

acute dietary exposure analysis included both food and drinking water. Therefore, acute 

aggregate risk is equivalent to the acute dietary risk, as discussed in Section 5.4, above. All risk 

estimates are not of concern. 

7.2 Short- and Intermediate-Term Aggregate Risk

Short- and intermediate-term aggregate exposure takes into account short- and intermediate-term 

residential exposure plus chronic exposure to food and water (considered to be a background 

exposure level). Bentazon is currently registered for uses that could result in short-term 

residential exposure, and it has been determined that it is appropriate to aggregate chronic 

exposure through food and water with short-term residential exposures to bentazon. 

Intermediate-term residential exposures are not anticipated based on the registered uses.

For short-term exposures, incidental oral and inhalation exposure risk assessments are 

appropriate to aggregate since the PODs for these routes are based on the same study/effects. 

The short-term incidental oral and inhalation exposures are combined (where appropriate) with 

chronic dietary (food and water) exposure for determination of aggregate short-term exposures. 

HED uses chronic dietary exposure when conducting short-term aggregate assessments as they 

have determined that these will more accurately reflect exposure from food over the HED 

defined short-term interval than will acute exposure. 

Adults may potentially be exposed to bentazon through dermal, inhalation, and dietary (food and 

drinking water) routes. A dermal hazard was not identified for bentazon; therefore, dermal risk 

estimates were not assessed and not included in the aggregate. Adult handler inhalation 

exposures have been aggregated with dietary (food and water) exposures for the short-term 

duration. The backpack scenario for mixing and loading liquids is the exposure scenario with the 

greatest exposure; therefore, the exposure estimates for this scenario are protective of other 

exposure scenarios. 

For young children, due primarily to their hand-to-mouth activities, short-term oral (non-dietary) 

exposures are expected along with dermal and dietary (food and drinking water) exposures. 
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Only the incidental oral exposures have been aggregated with dietary exposures since a dermal 

hazard was not identified. Note that the non-dietary residential exposures for children 1-2 years 

old are included in the aggregate assessment and are considered health protective for exposures 

and risk estimates for other potentially exposed lifestages. Typically, the dietary and non-dietary 

exposures for the same child population are aggregated together, however, in the case of 

bentazon, infants <1 year old have the highest dietary exposure. Therefore, an aggregate 

assessment for infants <1 year old has also been included, in addition to the children 1-2 year 

olds, using the non-dietary exposures for children 1-2 years old. The LOC is 100; therefore 

MOEs <100 are risk estimates of concern. 

Tables 7.2.1 and 7.2.2 summarize the short-term aggregate exposures and risk estimates for 

infants (<1 year old), 1-2 year olds and adults. The aggregate short-term MOEs are >100 for 

adults and children; therefore, aggregate exposures to bentazon are not of concern to HED.

Table 7.2.1. Short-term Aggregate Risk Calculations for Children 1-2 Years Old.

Population LOC Dietary Exposure (mg/kg/day)1

Incidental Oral 

Exposure (mg/kg/day)2

Aggregate MOE 

(food, water, and 

residential)3

All Infants (<1 year old) 100 0.116618 0.0152 110

Children 1-2 years old 0.066256 180

1 Dietary exposure = chronic dietary exposure from Table 5.4.1. 

2

Incidental Oral Exposure = Hand-to-mouth exposure for children (1 to <2 years old) from Table 6.3.1. 

3 Aggregate MOE = NOAEL (15 mg/kg/day) ÷ (dietary exposure + incidental oral exposure).

Table 7.2.2. Short-Term Aggregate Risk Calculations for Adults.

Population LOC Dietary Exposure (mg/kg/day)1

Inhalation Residential 

Exposure (mg/kg/day)2

Aggregate MOE 

(food, water, and 

residential)3

General U.S. Population 100 0.044888 0.0002 330

1 Dietary exposure = chronic dietary exposure from Table 5.4.1. 

2

Inhalation exposure = high-end inhalation residential exposure from Table 6.3.1.

3 Aggregate MOE = NOAEL (15 mg/kg/day) ÷ (dietary exposure + inhalation exposure).

7.3 Chronic Aggregate Risk

The chronic aggregate risk assessment results from long-term exposure to residues in food and 

drinking water, as there are no residential scenarios that result in long-term exposure. The 

chronic dietary exposure analysis included both food and drinking water and, therefore, the 

chronic aggregate risk assessment is equivalent to the chronic dietary risk assessment discussed 

in Section 5.4, above. All risk estimates are not of concern. 

7.4 Cancer Aggregate Risk

An aggregate cancer risk assessment was not performed because bentazon is not considered to be 

a carcinogen. 

8.0 Cumulative Exposure/Risk Characterization

Unlike other pesticides for which EPA has followed a cumulative risk approach based on a 

common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as 

to bentazon and any other substances and bentazon does not appear to produce a toxic metabolite 
Bentazon Preliminary Human Health Risk Assessment D471312

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Page 27 of 40

produced by other substances. For the purposes of this tolerance action, therefore, EPA has not 

assumed that bentazon has a common mechanism of toxicity with other substances. For 

information regarding EPA’s efforts to determine which chemicals have a common mechanism 

of toxicity and to evaluate the cumulative effects of such chemicals, see the policy statements 

released by EPA’s Office of Pesticide Programs concerning common mechanism determinations 

and procedures for cumulating effects from substances found to have a common mechanism on 

EPA’s website at http://www.epa.gov/pesticides/cumulative/.

9.0 Occupational Exposure/Risk Characterization

D418591, K. Lowe, 02-DEC-2014

9.1 Handler Risk Assessment

The quantitative exposure/risk assessment developed for occupational handlers is based on the 

following scenarios which cover all the registered and proposed uses of bentazon: 

 Mixing/loading liquids to support aerial applications,

 Mixing/loading liquids to support groundboom applications, 

 Applying sprays with aircraft,

 Applying sprays with groundboom equipment,

 Flagging to support aerial spray applications, 

 Mixing/loading/applying liquids via backpack,

 Mixing/loading/applying liquids via mechanically-pressurized handgun,

 Mixing/loading/applying liquids via manually-pressurized handwand.

The occupational handler exposure and risk estimates indicate that the short- and intermediateterm inhalation MOEs are not of concern to HED (i.e., MOE > 100) at baseline (no respirator). 

MOEs are all greater than or equal to 3,000.

HED has no data to assess exposures to pilots using open cockpits. The only data available is for 

exposure to pilots in enclosed cockpits. Therefore, risks to pilots are assessed using the 

engineering control (enclosed cockpits) and baseline attire (long-sleeve shirt, long pants, shoes, 

and socks); per the Agency’s Worker Protection Standard stipulations for engineering controls, 

pilots are not required to wear protective gloves for the duration of the application. With this 

level of protection, there are no risk estimates of concern for applicators.

The Agency matches quantitative occupational exposure assessment with appropriate 

characterization of exposure potential. While HED presents quantitative risk estimates for 

human flaggers where appropriate, agricultural aviation has changed dramatically over the past 

two decades. According the 2012 National Agricultural Aviation Association (NAAA) survey of 

their membership, the use of the Global Positioning System (GPS) for swath guidance in 

agricultural aviation has grown steadily from the mid 1990s. Over the same time period, the use 

of human flaggers for aerial pesticide applications has decreased steadily from ~15% in the late 

1990s to only 1% in the most recent (2012) NAAA survey. The Agency will continue to monitor 

all available information sources to best assess and characterize the exposure potential for human 

flaggers in agricultural aerial applications.
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Table 9.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Bentazon.

Exposure 

Scenarios Crop / Target Category Application Rate1

Amount 

Handled / 

Area 

Treated2

Inhalation 

Unit 

Exposures 

(ug/lb ai)3

Inhalation 

Dose 

(mg/kg/day)4

Inhalation 

MOE5

Baseline 

(unless 

otherwise 

noted)

Baseline 

(unless 

otherwise 

noted)

Baseline 

(unless 

otherwise 

noted)

Mixer/Loader

Aerial 

application of 

liquid 

formulation

Peas, Peppermint, Spearmint 1.5 lb ai/acre

350 acres

0.219

0.00144 10,000

Clover, Non-bearing food crops (almonds, 

apples, apricots, avocados, blackberries, 

blueberries, cherries, crabapples, dates, figs, 

grapes, grapefruit, lemons, limes, 

macadamias, nectarines, olives, oranges, 

peaches, pears, pecans, pistachios, plums, 

pomegranates, prunes, raspberries, tangelos, 

tangerines, walnuts)

1 lb ai/acre 0.000959 16,000

Corn, Peanuts, Beans, Soybeans 1.5 lb ai/acre 0.00493 3,000

Sorghum, Rice, Alfalfa 1 lb ai/acre 0.00329 4,600

Groundboom 

applications 

with liquid 

formulation

Golf course (fairways, tees, greens) 1 lb ai/acre 40 acres 0.00011 140,000

Nursery (ornamentals, vegetables, trees, 

container stock) 1 lb ai/acre 60 acres 0.000164 91,000

Sod 1 lb ai/acre

80 acres

0.000219 68,000

Peas, Peppermint, Spearmint 1.5 lb ai/acre 0.000329 46,000

Clover, Non-bearing food crops (almonds, 

apples, apricots, avocados, blackberries, 

blueberries, cherries, crabapples, dates, figs, 

grapes, grapefruit, lemons, limes, 

macadamias, nectarines, olives, oranges, 

peaches, pears, pecans, pistachios, plums, 

pomegranates, prunes, raspberries, tangelos, 

tangerines, walnuts)

1 lb ai/acre 0.000219 68,000

Corn, Peanuts, Beans, Soybeans 1.5 lb ai/acre 0.000821 18,000

Sorghum, Rice, Alfalfa 1 lb ai/acre 0.000548 27,000

Applicator

Aerial 

application of 

liquid 

formulation

Peas, Peppermint, Spearmint 1.5 lb ai/acre

350 acres 0.0049 

(EC)

0.0000321

(EC)

470,000

(EC)

Clover, Non-bearing food crops (almonds, 

apples, apricots, avocados, blackberries, 

blueberries, cherries, crabapples, dates, figs, 

grapes, grapefruit, lemons, limes, 

macadamias, nectarines, olives, oranges, 

peaches, pears, pecans, pistachios, plums, 

pomegranates, prunes, raspberries, tangelos, 

tangerines, walnuts)

1 lb ai/acre 0.0000215

(EC)

700,000

(EC)

Corn, Peanuts, Beans, Soybeans 1.5 lb ai/acre 0.00011

(EC)

140,000

(EC)

Sorghum, Rice, Alfalfa 1 lb ai/acre 0.0000735

(EC)

200,000

(EC)

Groundboom 

applications 

with liquid 

formulation

Golf course (fairways, tees, greens) 1 lb ai/acre 40 acres

0.34

0.00017 88,000

Nursery (ornamentals, vegetables, trees, 

container stock) 1 lb ai/acre 60 acres 0.000255 59,000

Sod 1 lb ai/acre

80 acres

0.00034 44,000

Peas, Peppermint, Spearmint 1.5 lb ai/acre 0.00051 29,000

Clover, Non-bearing food crops (almonds, 

apples, apricots, avocados, blackberries, 

blueberries, cherries, crabapples, dates, figs, 

1 lb ai/acre 0.00034 44,000
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Table 9.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Bentazon.

Exposure 

Scenarios Crop / Target Category Application Rate1

Amount 

Handled / 

Area 

Treated2

Inhalation 

Unit 

Exposures 

(ug/lb ai)3

Inhalation 

Dose 

(mg/kg/day)4

Inhalation 

MOE5

Baseline 

(unless 

otherwise 

noted)

Baseline 

(unless 

otherwise 

noted)

Baseline 

(unless 

otherwise 

noted)

grapes, grapefruit, lemons, limes, 

macadamias, nectarines, olives, oranges, 

peaches, pears, pecans, pistachios, plums, 

pomegranates, prunes, raspberries, tangelos, 

tangerines, walnuts)

Corn, Peanuts, Beans, Soybeans 1.5 lb ai/acre 0.00128 12,000

Sorghum, Rice, Alfalfa 1 lb ai/acre 0.00085 18,000

Mechanically

-pressurized 

Handgun

Rights-of-way (e.g., utilities, railroad, 

roadways)

0.023 lb 

ai/gallon

1000 

gallons 3.9 0.00112 13,000

Flagger

Aerial 

application of 

liquid 

formulation

Peas, Peppermint, Spearmint 1.5 lb ai/acre

350 acres 0.35

0.0023 6,500

Clover, Non-bearing food crops (almonds, 

apples, apricots, avocados, blackberries, 

blueberries, cherries, crabapples, dates, figs, 

grapes, grapefruit, lemons, limes, 

macadamias, nectarines, olives, oranges, 

peaches, pears, pecans, pistachios, plums, 

pomegranates, prunes, raspberries, tangelos, 

tangerines, walnuts)

1 lb ai/acre 0.00154 9,700

Corn, Peanuts, Beans, Soybeans 1.5 lb ai/acre 0.0023 6,500

Sorghum, Rice, Alfalfa 1 lb ai/acre 0.00154 9,700

Mixer/Loader/Applicator

Backpack

Rights-of-way (e.g., utilities, railroad, 

roadways)

0.023 lb 

ai/gallon 40 gallons

2.58 0.0000296 510,000 Landscaping, turf (lawns, athletic fields, 

parks, etc.)

Manuallypressurized 

Handwand

Landscaping, turf (lawns, athletic fields, 

parks, etc.) 30 0.000345 43,000

Mechanically

-pressurized 

Handgun

Golf course (fairways, tees, greens)

Landscaping, turf (lawns, athletic fields, 1 lb ai/acre 5 acres 1.9 0.000119 130,000

parks, etc.)

1 Based on registered and proposed labels.

2 Exposure Science Advisory Council Policy #9.1.

3 Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (March 2014); Level of mitigation: Baseline, EC = 

Eng. Controls.

4 Inhalation Dose = Inhalation Unit Exposure (μg/lb ai) × Conversion Factor (0.001 mg/μg) × Application Rate (lb ai/acre) × Area Treated 

(A/day) ÷ BW (80 kg).

5 Inhalation MOE = Inhalation NOAEL (15 mg/kg/day) ÷ Inhalation Dose (mg/kg/day).

9.2 Post-Application Risk Assessment

9.2.1 Inhalation Post-Application Risk Assessment

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 FIFRA SAP in December 2009, and received the SAP’s final report on March 

2, 2010 (http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html). The Agency 
Bentazon Preliminary Human Health Risk Assessment D471312

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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 bentazon.

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

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

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

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

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

performed, an inhalation exposure assessment was performed for occupational/commercial 

handlers. Handler exposure resulting from application of pesticides outdoors is likely to result in 

higher exposure than post-application exposure. Therefore, it is expected that these handler 

inhalation exposure estimates would be protective of most occupational post-application 

inhalation exposure scenarios.

9.2.2 Dermal Post-Application Risk Assessment

A quantitative dermal post-application assessment was not conducted because a dermal hazard 

for bentazon has not been identified. 

Restricted-Entry Interval

The REI specified on the proposed label is based on the acute toxicity of bentazon. Bentazon is 

classified as acute toxicity category III and IV for acute oral, acute dermal, and acute inhalation 

toxicity. It is classified as toxicity category II for eye irritation potential and category III for skin 

irritation potential. It is a dermal sensitizer. Under 40 CFR 156.208 (c) (2), ai’s classified as 

Acute II for acute dermal, eye irritation or primary skin irrigation are assigned a 24-hour REI. 

Therefore, the [156 subpart K] Worker Protection Statement interim REI of 24 hours is adequate 

to protect agricultural workers from post-application exposures to bentazon. 

10.0 References

Previous Risk Assessments

RED Chapter, 2/7/94

D. Rate, et al., 08-MAR-2006; D322258

Scoping Document

G. Kramer, et al., 17-MAR-2010; D375437

HASPOC Memo

J. Leshin, 15-OCT-2014; TXR0057054

ORE Memo

K. Lowe, 02-DEC-2014; D418591

Dietary Memo

G. Kramer, 02-DEC-2014; D418592
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Drinking Water Memo

S. Wente, 11-SEP-2014; D422778

cc: K. Lowe (RAB1)

RDI: RAB1 (10/29/14)

K. Lowe:S10948:PY-S:(703)347-8989:7509P:RAB1
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Appendix A. Toxicology Profile and Executive Summaries

A.1 Toxicology Data Requirements

The requirements (40 CFR 158.340) for food and nonfood uses for bentazon 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 Primary Eye Irritation....................................................

870.2500 Primary Dermal Irritation..............................................

870.2600 Dermal Sensitization .....................................................

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

870.3100 Oral Subchronic (rodent)...............................................

870.3150 Oral Subchronic (nonrodent).........................................

870.3200 21-Day Dermal..............................................................

870.3250 90-Day Dermal..............................................................

870.3465 90-Day Inhalation..........................................................

Yes

Yes

Yes

No

No1

Yes

Yes

Yes

No

-

870.3700a Developmental Toxicity (rodent) ..................................

870.3700b Developmental Toxicity (nonrodent) ............................

870.3800 Reproduction .................................................................

Yes

Yes

Yes

Yes

Yes

Yes

870.4100a Chronic Toxicity (rodent)..............................................

870.4100b Chronic Toxicity (nonrodent)........................................

870.4200a Oncogenicity (rat)..........................................................

870.4200b Oncogenicity (mouse) ...................................................

870.4300 Chronic/Oncogenicity ...................................................

No

Yes

No

Yes

Yes

No

Yes

No

Yes

Yes

870.5100 Mutagenicity—Gene Mutation - bacterial.....................

870.5300 Mutagenicity—Gene Mutation - mammalian................

870.5xxx Mutagenicity—Structural Chromosomal Aberrations...

870.5xxx Mutagenicity—Other Genotoxic Effects.......................

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

870.6100a Acute Delayed Neurotoxicity (hen)...............................

870.6100b 90-Day Neurotoxicity (hen) ..........................................

870.6200a Acute Neurotoxicity Screening Battery (rat).................

870.6200b 90-Day Neurotoxicity Screening Battery (rat) ..............

870.6300 Develop. Neurotoxicity .................................................

No

No

Yes

Yes

No

-

-

Yes

Yes

No

870.7485 General Metabolism ......................................................

870.7600 Dermal Penetration........................................................

870.7800 Immunotoxicity .............................................................

Yes

Yes

Yes

Yes

Yes

Yes

1. Study is not required at this time based upon weight of evidence decisions by the HASPOC. Decisions are 

discussed in detail in TXR# 0057054.
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A.2 Toxicity Profiles

Table A.2.1. Acute Toxicity Profile - Test Substance.

Guideline No. Study Type MRID(s) Results Toxicity Category

870.1100 Acute oral (rat) 00135394 LD50 = 1,100 mg/kg III

870.1200 Acute dermal (rat) 00135399 LD50 > 2,500 mg/kg III

870.1300 Acute inhalation (rat) 47030108 LC50 > 5.1 mg/L IV

870.2400 Acute eye irritation (rabbit) 00072791

“Moderately irritating”-

irritation clearing within 

8-16 days

II

870.2500 Acute dermal irritation (rabbit) 00072790 Slight irritation at 72 

hours IV

870.2600 Skin sensitization 00164714 

2654091 Sensitizer NA

Table A.2.2. Subchronic, Chronic, and Other Toxicity Profile.

Guideline 

No. Study Type MRID No. (year)/ Classification /Doses Results

870.3100 90-Day oral 

toxicity (Rat)

40222201 (1987)

acceptable/guideline

(0, 400, 1200, 3600 ppm)

M: 0, 25.3, 77.8, 243.3

F: 0, 28.9, 86.1, 258.3 

mg/kg/day

NOAEL = 77.8/86.1 mg/kg/day.

LOAEL = 243.3/258.3 mg/kg/day, M/F, based 

on a diversity of effects, many reversible, 

including depressed mean body weights in 

females, a slight increase in food consumption 

in males, increased thromboplastin and 

prothrombin times (males only), and increased 

kidney and liver weights. In addition, females 

in the 3,600-ppm group showed suggestive 

evidence for the presence of lung thrombi and 

dilated uterine horns.

870.3150 90-Day oral 

toxicity (Dog)

0091058 (1972)

unacceptable 

0, 100, 300, 1000, 3000 

ppm

0, 2.5, 7.5, 25, and 75 

mg/kg/day

NOAEL = 2.5 mg/kg/day.

LOAEL = 7.5 mg/kg/day based on prostatitis.

Note: According to the HIARC briefing 

package (page 190) this study was classified as 

unacceptable due to too few animals (3 per sex 

per dose). The study did not state the test 

material was technical bentazon. Finally, blood 

chemistry and hematological parameters were 

only measured during the pretreatment period, 

6 and 13 weeks.

870.3200 21-Day dermal 

toxicity (Rabbit)

42885302 (1993)

acceptable/guideline

0, 250, 500, 1000 

mg/kg/day

NOAEL = 1000 mg/kg/day (HDT).

LOAEL >1000 mg/kg/day.
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Table A.2.2. Subchronic, Chronic, and Other Toxicity Profile.

Guideline 

No. Study Type MRID No. (year)/ Classification /Doses Results

870.3700a Prenatal 

developmental in 

(Rat)

40114201 (1986) 

acceptable/guideline

0, 40, 100, 250 mg/kg/day

Maternal NOAEL = 100 mg/kg/day.

Maternal LOAEL = 250 mg/kg/day based on 

increased postimplantation loss. 

Developmental NOAEL = 100 mg/kg/day.

Developmental LOAEL = 250 mg/kg/day 

based on skeletal variations (incomplete or 

absent ossification in the phalangeal nuclei of 

the extremities, the sternebrae and cervical 

vertebrae), and reduced body weights of fetuses 

surviving to day 21. 

870.3700b Prenatal 

developmental in 

(Rabbit)

40114202 (1987)

acceptable/guideline

0, 75, 150, 375 mg/kg/day

Maternal/developmental NOAEL = 150 

mg/kg/day.

Maternal/developmental LOAEL = 375 

mg/kg/day (HDT) based on 1 doe with partial 

abortions, and embryonic resorptions.

Developmental NOAEL =150 mg/kg/day.

Developmental LOAEL = 375 mg/kg/day 

based upon no living fetuses.

870.3800 Reproduction and 

fertility effects

(Rat)

41054902 (1989)

0, 200, 800, 3200 ppm

acceptable/guideline

0, 15, 62, 249 mg/kg/day

Parental NOAEL = 62 mg/kg/day.

Parental LOAEL = 249 mg/kg/day based on 

increased incidences of kidney mineralization 

and liver microgranuloma. 

Offspring NOAEL = 15 mg/kg/day.

Offspring LOAEL = 62 mg/kg/day based on 

decreased absolute pup body weights during 

lactation.

Reproductive NOAEL = 249 mg/kg/day.

Reproductive LOAEL was not observed.

870.4100b Chronic toxicity 

(Dog)

41054901, 42133201 

(1989, 1991) 

acceptable/guideline

0, 100, 400, 1600 ppm

0, 3.2, 13.1, 52.3 

mg/kg/day

NOAEL = 13.1 mg/kg/day.

LOAEL = 52.3 mg/kg/day upon clinical signs 

(emaciation, dehydration, bloody stool, pale 

mucous membranes, moderated activity) and 

slight to severe anemia (decreased hemoglobin, 

hematocrit, and erythrocyte count, decreased 

reticulocytes, platelets, leukocytes, PTT, and 

abnormal red cell morphology) during the first 

13 weeks.
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Table A.2.2. Subchronic, Chronic, and Other Toxicity Profile.

Guideline 

No. Study Type MRID No. (year)/ Classification /Doses Results

870.4200 Chronic/

Carcinogenicity

(Rat)

00142832, 40871702 

(1984, 1988)

acceptable/guideline

0, 200, 800, 4000 ppm

M: 0, 9, 35, 180 

mg/kg/day 

F: 0,11, 45, 244 

mg/kg/day 

NOAEL = 9 mg/kg/day.

LOAEL = 35/45 mg/kg/day, males/females, 

based on increased water consumption, changes 

in urinalysis and hematology/coagulation 

parameters, and decreased absolute and relative 

thyroid weight. 

(no) evidence of carcinogenicity.

870.4300 Carcinogenicity

(mouse)

00142831, 00142833, 

40871701, 40934101 

(1982, 1985, 1988) 

acceptable/guideline

0, 100, 400, 2000 ppm

M: 0, 12, 47, 242 

mg/kg/day 

F: 0, 12, 48, 275 

mg/kg/day

NOAEL = 12 mg/kg/day.

LOAEL = 47/48 mg/kg/day based on increased 

prothrombin time, increased liver and kidney 

weights, calcification of the tunica albuginea, 

and islet cell hyperplasia of the pancreas. 

(no) evidence of carcinogenicity.

870.5100

Gene Mutation -

Salmonella 

typhimurium

00158382 (1983)

acceptable/guideline

Strains TA 1535, 1537, 1538, 98, and 100 

tested from 20-5000 μg/plate ± metabolic 

activation. Negative up to limit dose.

870.5100

Gene Mutation -

Salmonella 

typhimurium and 

Escherichia coli

00158383 (1985)

acceptable/guideline

Strains TA 1535, 1537, 1538, 98, 100, WP2 

uvrA tested from 20-5000 μg/plate ± metabolic 

activation. Negative up to limit dose.

870.5300

In vitro

mammalian cell 

gene mutation 

assay with 

Chinese hamster 

ovary cells

42129610 (1991)

acceptable/guideline

Cells tested ±metabolic activation from 100-

5000 μg/mL. Negative up to limit of solubility.

870.5300

In vitro

mammalian cell 

gene mutation 

assay with 

Chinese hamster 

ovary cells (CHOK1-BH4) 

00158385 (1985)

acceptable/guideline

1.25-15 mg/ml 

Cells tested ±metabolic activation from 1250-

15,000 μg/mL. Negative up to highest dose 

tested.

870.5395 In vivo mouse 

bone marrow 

micronucleus 

assay

00158388 (1985)

acceptable/guideline

Mice were exposed to 200-800 mg/kg of 

bentazon. Negative up to maximum tolerated 

dose.

870.5550 Unscheduled 

DNA synthesis in 

primary mouse 

hepatocytes

00158386 (1985)

acceptable/guideline

Hepatocytes were exposed to test substance at 

concentrations ranging from 2.51-1004 μg/mL. 

Negative up to cytotoxic dose.

870.6200a Acute 

neurotoxicity 

screening battery

48970707 (2012)

acceptable/guideline

0, 50, 150, 400 mg/kg

Systemic NOAEL = 400 mg/kg. 

Systemic LOAEL was not established.

Neurotoxicity NOAEL = 50 mg/kg.

Neurotoxicity LOAEL = 150 mg/kg based on 

decreased motor activity in males on study day 

0.
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Table A.2.2. Subchronic, Chronic, and Other Toxicity Profile.

Guideline 

No. Study Type MRID No. (year)/ Classification /Doses Results

870.6200b Subchronic 

neurotoxicity 

screening battery

48970708 (2004)

acceptable/guideline

0, 300, 1000 or 3500 ppm 

(0, 21.9/27.0, 73.6/86.4 or 

258.1/306.3 mg/kg 

bw/day [M/F])

Systemic NOAEL = 3500 ppm (258.1 and 

306.3 mg/kg bw/day [M/F]).

Systemic LOAEL was not established.

Neurotoxicity NOAEL = 3500 ppm (258.1 and 

306.3 mg/kg bw/day [M/F]). 

Neurotoxicity LOAEL was not established.

870.7485 Metabolism and 

pharmacokinetics

(rat)

40481801 (1987)

acceptable/guideline

Recoveries of radioactivity in urine after oral 

dosing (88.1-95.9% of the dose) indicate 

extensive absorption of the compound from the 

GI tract. No differences between the sexes or 

among dose groups were found. At sacrifice, 

total radioactive residue in the carcass was less 

than 0.69% of the dose in all groups. 

Experiments with bile duct-cannulated rats 

indicated that biliary excretion of radioactivity 

amounted only to 0.24-1.31% of the dose at 3.6 

mg/kg and to 0.80-1.84% of the dose at 195 

mg/kg. Parent bentazon was the major 

metabolite found in urine, amounting to 77.37-

91.02% of the dose among the orally dosed 

animals of the main experiment. A small 

amount of benzene ring hydroxylation was 

observed: 6-OH-bentazon was present in 

amounts up to 6.34% of the dose. The isomeric 

8-OH-bentazon was present in trace amounts, 

0.0-0.23% of the dose.

870.7485 Metabolism and 

pharmacokinetics

(rat)

00158379 (1979)

acceptable/guideline

The absorption and excretion of the free acid 

form of bentazon or its sodium salt in male rats 

after oral administration appear to be rapid and 

essentially equivalent. No sex differences in 

the absorption, metabolism or excretion of 

sodium bentazon are apparent based on

equivalent excretion half-lives (4 hours), 

pattern of excretion (>90% in urine), or urinary 

metabolite identification (>80% as free acid). 

No radioactivity was recovered in the expired 

air or carcass.

870.7600 Dermal 

penetration 

(rabbit)

00158380 (1985)

acceptable/guideline

0.12, 1.2, 12, 120 mg/kg

Single topical application of radioactive sodium 

bentazon did not appear to significantly 

penetrate the skin since a maximum of only 1-

2% of the radioactivity was recovered 

(primarily in the urine) at 72 hours. Negligible 

amounts of dermally applied radioactivity were 

retained in the liver, kidneys, GI tract, and 

carcass. For risk assessment purposes, dermal 

penetration is estimated to be 1-2%.

870.7800 Immunotoxicity 48970709 (2012)

acceptable/guideline

0, 300, 1000, or 3000 ppm 

(0, 105, 331, 1094 mg/kg 

bw/day [F])

Systemic NOAEL = 1094 mg/kg bw/day. 

Systemic LOAEL was not established. 

Immunotoxicity NOAEL = 1094 mg/kg 

bw/day. 

Immunotoxicity LOAEL was not established. 
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Appendix B. Physical/Chemical Properties

Physicochemical Properties of Bentazon

Molecular mass 240.3

Melting point/range 137-139°C 

Water solubility (22C) 570 mg/L 

Vapor pressure (25C) <1 x 10-7 mm Hg

Density/ Sp. gravity g/cm-3

1.47 at 20C

Henry’s Law Constant 5.55 x 10-11 atm m3/mol

Octanol/water partition coefficient (Log Kow) -0.46 at pH 7.0

Solvent solubility 

(g/100 g solvent, 20oC)

Acetone.: 150.7 

Benzene: 3.3

Chloroform: 18.0

Ethanol: 86.1

Ethyl acetate: 61.6

Cyclohexane: 0.02
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Appendix C. International Residue Limits

International Residue Limits (275200, 103901; 09/22/14)

Summary of U.S. Tolerances and International MRLs1. 

Residue Definition

U.S. Canada Mexico1 Codex2

40CFR180.355

(a) General. (1) Tolerances are 

established for the combined residues 

of the herbicide bentazon (3-isopropyl1H-2,1,3-benzothiadiazin-4(3H)-one2,2-dioxide) and its 6- and 8-hydroxy 

metabolites 

3-(1-methylethyl)-1H2,1,3-benzothiadiazin4(3H)-one 2,2-dioxide, 

including the 

metabolites 6-hydroxy3-(1-methylethyl)-1 H2,1,3-benzothiadiazin4(3H)-one 2,2-

dioxide and 8-hydroxy3-(1-methylethyl)-1H2,1,3-benzothiadiazin4(3H)-one 2,2-dioxide

Sum of bentazone, 6-

hydroxybentazone and 

8-hydroxybentazone 

expressed as bentazone.

The residue is not fatsoluble.

Commodity Tolerance (ppm)/Maximum Residue Limit (mg/kg)

Commodity U.S. Canada Mexico1 Codex2

Bean, dry, seed 0.05 0.5 beans (type not 

defined

0.04 (*) beans, dry 

Bean, succulent 0.5 0.5 beans (type not 

defined)

0.01 (*) beans, except 

broad bean and soya 

bean

(green pods and 

immature seeds)

0.01 (*) beans, shelled 

(succulent= immature 

seeds)

Corn, field, forage 3.0

Corn, field, grain 0.05 0.05 0.01 (*) cereal grains

Corn, field, stover 3.0 0.4 (fodder dry) 

Corn, pop, grain 0.05 0.01 (*) cereal grains

Corn, sweet, kernel plus cob 

with husks removed 0.05 0.01 (*) 

Cowpea, forage 10.0

Cowpea, hay 3.0

Flax, seed 1.0 0.05

Pea, dry, seed 1.0 3 peas (type not 

defined) 1 (field pea dry)

Pea, field, hay 8.0

Pea, field, vines 3.0

Pea, succulent 3.0 3 peas (type not 

defined)

1.5 peas (pods and 

succulent=immature 

seeds)

Peanut 0.05 0.05 0.05 (*)

Peanut, hay 3.0
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Summary of U.S. Tolerances and International MRLs1. 

Pepper, nonbell 0.05

Peppermint, tops 1.0

Rice, grain 0.05 0.05 0.01 (*) cereal grains

Rice, hulls 0.25

Rice, straw 3.0

Sorghum, grain, forage 0.20

Sorghum, grain, grain 0.05 0.15 0.01 (*) cereal grains

Sorghum, grain, stover 0.05

Soybean, forage 8.0

Soybean, hay 8.0

Soybean, seed 0.05 0.05 0.01 (*) soya bean (dry)

Spearmint, tops 1.0

MRLs with NO U.S. Equivalent

Alfalfa fodder 0.5

Barley straw and fodder, dry 0.3

Cereal grains 0.01 (*)

Hay or fodder (dry) of 

grasses

2

Herbs 0.1

Linseed 0.02 (*)

Millet fodder, dry 0.3

Oat straw and fodder, dry 0.3

Potato 0.1

Onion, bulb 0.1 0.04 

Rye straw and fodder, dry 0.3

Spring onion 0.08

Triticale straw and fodder, 

dry 0.3

Wheat straw and fodder, dry 0.3

Barley 0.1

Blueberries 0.05

Leeks 0.1

Pearl millet 0.15

Proso millet 0.15

Wheat 0.1

Residue Definition

U.S. Canada Mexico1 Codex2 U.S.

40CFR180.355

2) Tolerances are 

established for the combined 

residues of the herbicide 

bentazon (3-isopropyl-1H2,1,3-benzothiadiazin4(3H)-one-2,2-dioxide) and 

its metabolite 2-amino-Nisopropyl benzamide 

(AIBA)

Bentazon

Commodity Tolerance (ppm)/Maximum Residue Limit (mg/kg)
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Summary of U.S. Tolerances and International MRLs1. 

Commodity U.S. Canada Mexico Codex

Cattle, fat 0.05

Cattle, meat byproducts 0.05

Cattle, meat 0.05

Egg 0.05 0.01 (*)

Goat, fat 0.05

Goat, meat byproducts 0.05

Goat, meat 0.05

Hog, fat 0.05

Hog, meat byproducts 0.05

Hog, meat 0.05

Milk 0.02 0.01 (*)

Poultry, fat 0.05

Poultry, meat byproducts 0.05 0.07

Poultry, meat 0.05 0.03 (fat)

Sheep, fat 0.05

Sheep, meat byproducts 0.05

Sheep, meat 0.05

Completed by: M. Negussie, 09/25/14

1 Bolded values indicate that the tolerance and MRLs are not harmonized. 

2 Mexico defers to US tolerances and/or Codex MRLs for its export purposes. 

3

(*) = absent at the limit of quantitation.

(c) Tolerances with regional registrations. Tolerances with regional registration as defined in §180.1(m), are 

established for combined residues of the herbicide, bentazon (3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one-2,2-

dioxide) and its 6- and 8-hydroxy metabolites in or on the following food commodities:

Commodity Parts per million

Clover, forage 1.0

Clover, hay 2.0