UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEM ICAL SAFETY 

AND POL L UTION PREVENTION 

MEMORANDUM 

Date: 10-NOY-2015 

SUBJECT: Pendimethalin - Human Health Risk Assessment to Support the Proposed New 

Uses on the Caneberry Subgroup 13-07 A and the Bushberry Subgroup l 3-07B; 

Amended Use on Grasses and Establishment of Tolerances for Pendimethalin 

in/on Grass Forage, Fodder, and Hay (Crop Group 17) with New Ruminant 

Tolerances; and Crop Group Conversion for Tree Nut Crop Group 14. 

PC Code: 10850 I DP Barcodc: D428265 

Registration No.: 241-418 

Regulatory Action: NA 

CaseNo.: NA 

Decision No.: 490089 

Petition No.: 4F8261 , 4E8282 

Risk Assessment Type: New Use 

TXR No.: NA CAS No.: 40487-42-1 

MRID No.: NA 40 CFR: 40 CFR § 180.361 

FROM: 

.

Sheila Piper, Risk Assessor ~~~/'~ Mohsen 

P. Yvonne 

Sahafeyan

Barnes, 

, 

Chem

Chemi

ist 

st 

?, 

v""~e 

~ 

~ ~ 1 

Bridget Bobowiec, Biologist 

Risk 

Yung 

Assessment 

Yang, Ph.D.

Branch 

, Toxicologist 

Yl 

th 

(] -

6 , ~ 

(/ v 

Health Effects Division (7509P) 

THROUGH: Donna S. Davis, Acting Chie@ tA/" 0 rh\.,, · (" 

Ri

Health 

sk Assessment 

Effects Division 

Branch 

(7509P) 

YI ~ 

TO: Emily Schmidt, Risk Manager Reviewer 

Reuben Baris, Risk Manager 

Dan Kenny, Chief 

Herbicide Branch 

Registration Division (7505P) 

and 

Page 1 of 42 
Pendimethalin Draft Human Health Risk Assessment 

Andy Ertman, Risk Manager 

Barbara Madden, Team Leader 

Marion Johnson, Branch Chief 

Minor Use and Emergency Response Branch 

Registration Division (7505P) 

Page 2of42 

DP No. 0 428265 
Pendimethalin Human Health Risk Assessment DP No. D428265

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Table of Contents

1.0 Executive Summary............................................................................................................. 5

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

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

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

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

2.2.3. Revisions to Petitioned For Tolerances...................................................................... 11

2.3. Label Recommendations................................................................................................ 11

3.0. Introduction........................................................................................................................ 11

3.1. Chemical Identity ........................................................................................................... 12

3.2. Physical/Chemical Characteristics................................................................................. 12

3.3. Pesticide Use Pattern...................................................................................................... 13

3.4.1. Anticipated Exposure Pathways..................................................................................... 15

3.5. Consideration of Environmental Justice ........................................................................ 15

4.0 Hazard Characterization and Dose-Response Assessment................................................ 15

4.2 Absorption, Distribution, Metabolism, & Elimination (ADME)...................................... 16

4.2.1 Dermal Absorption ..................................................................................................... 16

4.4.1 Completeness of the Toxicology Database ................................................................ 17

4.4.2. Evidence of Neurotoxicity.......................................................................................... 17

4.4.3. Evidence of Sensitivity/Susceptibility in the Developing or Young Animal............. 17

4.4.4. Residual Uncertainty in the Exposure Database......................................................... 17

4.5 Toxicity Endpoint and Point of Departure Selections.................................................... 18

4.5.1 Toxicity Endpoint and Point of Departure Selections.................................................... 18

4.5.2. Recommendation for Combining Routes of Exposures for Risk Assessment ........... 20

4.5.3. Cancer Classification and Risk Assessment Recommendation.................................. 20

4.6. Endocrine Disruption........................................................................................................ 20

5.0 Dietary Exposure and Risk Assessment ............................................................................ 21

5.1 Residues of Concern Summary...................................................................................... 21

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

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

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

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

5.4.2. Percent Crop Treated Used in Dietary Assessment.................................................... 23

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

5.4.4. Chronic Dietary Risk Assessment .............................................................................. 24

5.4.5. Cancer Dietary Risk Assessment................................................................................ 24

5.4.6. Summary Table........................................................................................................... 24

6.0 Residential (Non-Occupational) Exposure/Risk Characterization .................................... 25

6.1 Residential Risk Estimates for Use in Aggregate Assessment ...................................... 25

6.2 Spray Drift...................................................................................................................... 26

6.3 Residential Bystander Post-Application Inhalation Exposure ....................................... 27

7.0 Aggregate Exposure/Risk Characterization....................................................................... 27
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7.1 Acute Aggregate Risk .................................................................................................... 27

7.2 Short-Term Aggregate Risk ........................................................................................... 27

7.3 Intermediate-Term Aggregate Risk................................................................................ 28

7.4 Chronic Aggregate Risk................................................................................................. 28

7.5 Cancer Aggregate Risk................................................................................................... 28

8.0 Cumulative Exposure/Risk Characterization..................................................................... 28

9.0 Occupational Handler Exposure/Risk Estimates............................................................ 29

9.2 Occupational Post-application Exposure/Risk Estimates .............................................. 30

9.2.1 Occupational Post-application Inhalation Exposure/Risk Estimates.......................... 30

9.2.2 Occupational Post-Application Dermal Exposure/Risk Estimates............................. 31

10.0 References.......................................................................................................................... 31

Appendix A. Toxicology Profile and Executive Summaries....................................................... 33

A.1 Toxicology Data Requirements...................................................................................... 33

A.2 Toxicity Profiles............................................................................................................. 34

Appendix B. International Residue Limits Table ...................................................................... 39

Appendix C. Occupational Handler Non-Cancer Exposure and Risk Estimates for 

Pendimethalin ............................................................................................................................... 40

Appendix D. Review of Human Research................................................................................... 42
Pendimethalin Human Health Risk Assessment DP No. D428265

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Executive Summary

Pendimethalin is a selective herbicide used for controlling annual grasses and broadleaf weeds. It 

is a meristematic inhibitor that interferes with the plant’s cellular division and it is generally 

applied early in the growing season as a pre-plant, pre-emergent and/or early post-emergent 

herbicide. It is registered for a variety of agricultural uses and non-agricultural ones such as 

lawns, parks, golf courses, and ornamentals. The chemical can be applied by chemigation, 

ground, and aerial equipment.

The registrant, BASF, has requested a reduction of the pre-harvest interval (PHI) for Bermuda

grass and other perennial warm-season grasses grown for forage, grazing, and hay production 

from 45 and 60 days to 0 days for the end-use product Prowl® H2O (EPA Reg. no. 241-418; 

38.7% a.i.). Amended tolerances on grass forage and hay were proposed to support the reduced 

PHI. In addition, IR-4 has petitioned (PP#4E8282) for new uses in/on minor crops to include the 

caneberry subgroup 13-07A, and the bushberry subgroup 13-07B, as well as conversion of the 

tree nut crop group 14 to the tree nut group 14-12. In support of its petition, field trial data for 

raspberry and blueberry were submitted. No new data for the tree nut group 14 crop group 

conversion were submitted or are needed.

The toxicology database for pendimethalin is complete, no additional data are required. The 

target organ for pendimethalin is the thyroid. Thyroid toxicity in chronic and subchronic rat and 

mouse studies was manifested as alterations in thyroid hormones (decreased total T4, and T3, 

increased percent of free T4 and T3), increased thyroid weight, and microscopic thyroid lesions 

(including increased thyroid follicular cell height, follicular cell hyperplasia, as well as follicular 

cell adenomas). Pendimethalin has low acute toxicity by the oral, dermal, or inhalation route of 

exposure. It is not an eye or skin irritant and is not a skin sensitizer.

There is no evidence that pendimethalin is a developmental, reproductive, neurotoxic, or 

immunotoxic chemical. There is no evidence of increased qualitative or quantitative 

susceptibility in the young and exposure estimates are unlikely to underestimate risk; therefore, 

the FQPA Safety Factor is reduced to 1x.

The Cancer Peer Review Committee (CARC) classified pendimethalin as a "Group C", possible 

human carcinogen and recommended a non-quantitative approach (i.e., non-linear, RfD 

approach) to risk assessment. The chronic risk assessment is considered to be protective of any 

cancer effects; therefore, a separate quantitative cancer aggregate risk assessment is not required.

An endpoint/POD (point of departure) was selected from a rat acute neurotoxicity study for acute 

dietary risk assessment based on reduced motor activity with an uncertainty factor (UF) of 100x 

(10x for interspecies extrapolation, 10x for intraspecies variation, and 1x for FQPA Safety 

Factor). For chronic dietary risk assessment and incident oral, dermal, inhalation exposure 

scenarios, three studies (a 92-day thyroid function study, a 56-day thyroid function study and a 

14-day intra-thyroid metabolism study in rats) were considered as co-critical in establishing a 
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POD. All studies reflecting thyroid toxicity, HED has determined that these studies collectively 

support a NOAEL of 10 mg/kg/day and a LOAEL of 31 mg/kg/day for thyroid effects include 

several hormonal and histological thyroid changes and thyroid hormonal effects and should be 

used as the POD for all durations and exposure scenarios. An UF of 30x (3x for interspecies 

extrapolation and 10x for intraspecies variation) is applied. The interspecies UF (used to account 

for animal to human differences in toxicokinetics and toxicodynamics) was reduced to 3X with 

respect to observed thyroid effects in the rat because of several important quantitative dynamic 

differences between rats and humans with respect to thyroid function (Interim Guidance on 

Thyroid Disrupting Pesticides, dated 11/01/2005). The FQPA factor is reduced to1x. 

The residue chemistry database to support new agricultural uses of pendimethalin is complete. 

The nature and magnitude of the residue in plants, livestock, and rotational crops have been 

adequately delineated. The residues of concern (ROCs) in plants for primary and rotational 

crops for tolerance enforcement and risk assessment purposes are pendimethalin and its alcohol 

metabolite (CL 202,347) and ruminants are pendimethalin and its metabolite, 1-(1-ethylpropyl)-

5, 6-dimethyl-7-nitro-1H-benzimidazole (metabolite 6). The available poultry metabolism data 

indicate that there is no reasonable expectation of finite residues of pendimethalin, and 

metabolites of concern in poultry and eggs [40 CFR §180.6(a)(3)] as a result of the registered 

uses. Adequate magnitude of residue data on requested uses and acceptable validated 

enforcement methods for plants, and livestock are available. Adequate field trial data have been 

submitted for the new uses on caneberries and grasses. The studies were generated using 

validated data collection methods and are supported by storage stability data of appropriate 

duration and storage conditions. There are no new poultry feed items associated with this action. 

Currently, there is no reasonable expectation of finite residues in poultry commodities (40CFR 

§180.6(a)(3)). A significant increase in the ruminant dietary burden is expected as a result of the 

0-day PHI and post grazing interval; therefore, a new ruminant feeding study was submitted. 

HED has determined that new tolerances are needed in ruminant commodities as a result of the 

amended use on grasses. 

Unrefined acute and chronic dietary (food and drinking water) risk assessments were conducted 

using tolerance-level residues, assuming 100% crop treated for all commodities, using default 

processing factors, and incorporating modelled drinking water estimated exposure values. The

dietary food and drinking water risk estimate is <2% of the acute and chronic population 

adjusted dose (aPAD/cPAD) for the U.S. population and all population subgroups. 

There are no proposed new residential uses for pendimethalin. Existing pendimethalin 

residential uses include use in/on lawns, parks, golf courses, ornamentals, landscape ground 

covers, fruit bearing trees and nuts. Risk estimates for both residential handler and post 

application exposure from the last updated 2012 residential assessment were not of concern as 

margins of exposure (MOEs) were greater or equal to 30 (S. Shelat, 06/07/2012, D402406). 

The acute aggregate risk assessment, by definition, includes food and water only, and as noted 

above is not of concern (<100% of the aPAD). There are no long-term residential exposure 
Pendimethalin Human Health Risk Assessment DP No. D428265

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scenarios, therefore, the long-term aggregate exposures and risk assessment is equivalent to the 

chronic dietary risk assessment, and is not of concern (<100% of the cPAD). HED has 

conducted short-term aggregate exposure and risk assessments which combined average food 

and water exposure and non-dietary (residential) sources of exposure to pendimethalin. The 

resulting short-term aggregate MOEs do not exceed HED’s level of concern, (MOEs ≥ 30). The 

short-term aggregate MOEs for adults is 130 and children 1-2 years old is 92. Intermediate-term 

residential exposure is not anticipated; therefore a separate intermediate-term assessment was not 

conducted.

HED previously conducted occupational handler exposure and risk assessments for registration 

review in 2012 (D402406) for several representative crops of the caneberry, bushberry, and tree 

nut crop group. The proposed application rates and timing, and use pattern for those subgroups 

(caneberry, bushberry, and tree nut) are identical to those representative crops; therefore, a new 

quantitative occupational handler assessment is not required. In addition this action amends the 

PHI for Bermudagrass and other warm perennial grasses which was originally assessed for 

occupational exposure in 2009 (S. Shelat, 10/27/2009, D371025). In the 2012 and the 2009 

assessments short- and intermediate-term combined occupational handler dermal and inhalation 

margins of exposure (MOEs) were not of concern to HED (i.e., MOE > 30) with baseline attire 

and gloves personal protective equipment (PPE). 

Post-application exposure was not assessed for the proposed crop groups due to the pre-emergent 

and soil directed use pattern and review of chemical specific dislodgeable foliar residue (DFR) 

study on tobacco and sugarcane (MRID 44969901). The study exemplifies an application

directed towards the soil to minimize contact with the actual crop. Pendimethalin application to 

Bermudagrass is expected to be a post emergent foliar spray and not represented by the DFR 

study. In 2009 the estimated occupational dermal post application risks to treated Bermudagrass 

using default 25% dissipation did not exceed HED’s level of concern (MOEs ≥> 30) on the day 

of treatment for early post application activities including scouting and hand laying irrigation.

All post-application activities should comply with minimum 12-hour re-entry interval (REI) 

assigned to pendimethalin as it classified as Toxicity Category III and IV for acute dermal, 

dermal irritation and eye irritation. 

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

intentionally exposed to a pesticide or other chemical. Studies that involve adult human subjects 

are subject to ethics review pursuant to 40 CFR 26, the studies have been reviewed and are in 

compliant with applicable ethics requirements. 

2.0 HED Recommendations

2.1 Deficiencies
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There are no data deficiencies relating to toxicology, occupational, and residential exposure with 

the current petition for uses of pendimethalin. The registrant should submit a revised Section F 

according to the recommended tolerances listed in Tables 2.2.2.A and 2.2.2.B. The registrant 

should also confirm the availability or replenish 1-(1-ethylpropyl)-5, 6-dimethyl-7-nitro-1Hbenzimidazole (metabolite 6) standards to the EPA Repository. 

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

An adequate plant enforcement method is available for pendimethalin. The PAM Volume II lists 

four gas chromatography with electron capture detection (GC/ECD) methods for the 

determination of pendimethalin residues of concern in plant commodities. Methods I and III 

determine residues of the parent, whereas Methods II and IV determine residues of the 3,5-

dinitrobenzyl alcohol metabolite (CL 202347). The limit of quantitation (LOQ) of each method 

is 0.05 ppm. These methods are appropriate for enforcement of the newly proposed cane and 

bushberry tolerances. 

The proposed analytical method, BASF Method D0405, is adequate to enforce the proposed 

tolerance for ruminant matrices. BASF has proposed Method D0405 which is a high 

performance liquid chromatography with dual mass spectroscopic detection (HPLC MS/MS)

method as an enforcement method for ruminant commodities. This method determines residues 

of pendimethalin and its metabolites CL 202,347 and Goat Metabolite 6 in milk and cow tissues. 

Method D0405 has undergone a successful independent laboratory validation (ILV). The 

validated LOQ was 0.01 ppm for each analyte in milk and 0.05 ppm for each analyte in tissues. 

2.2.2 Recommended Tolerances

Tolerances are currently established for residues of the herbicide pendimethalin, including its 

metabolite and degradate, in or on the commodities in the 40 CFR §180.361. The tolerance 

expression listed in the 40 CFR §180.361 for plants does not comply with the HED interim 

tolerance expression policy (S. Knizner, 5/27/09) and should be changed to: 

Tolerances are established for residues of the herbicide pendimethalin, including 

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

tolerance levels specified in the following table below is to be determined by 

measuring only the sum of pendimethalin, [N- (1-ethylpropyl)-3,4-dimethyl-2,6-

dinitrobenzenamine] and its metabolite, 4-[(1-ethylpropyl)amino]-2-methyl-3,5-

dinitrobenzyl alcohol, calculated as the stoichiometric equivalent of 

pendimethalin, in or on the commodity.

Furthermore, since tolerances for livestock are to be established now, the “§180.361 (a)” in 40 
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CFR should be changed to “§180.361 (a) General. (1)”

Table 2.2.2.-A below summarizes the plant tolerances for this action.

Table 2.2.2-A Tolerance Summary for Pendimethalin for Plants. 

Commodity

Established 

Tolerances 

(ppm)

Proposed 

Tolerances 

(ppm)

HEDRecommended 

Tolerance 

(ppm)

Comment

Fruit, caneberry, subgroup13-

07A None 0.1 0.10

Fruit, bushberry, subgroup13-

07B None 0.1 0.10

Nut, tree group 14-12 None 0.1 0.10

Grass forage, fodder, and hay 

crop group 17, forage 20 1000 1000

Grass forage, fodder, and hay 

crop group 17, hay 13 2000 2000

Pistachio 0.1 None None Revoke: covered by 

CG 14-12

Nut, tree group 14 0.10 None None Revoke: converted 

to CG 14-12

Juneberry 0.10 None None Revoke: covered by

CG 13-07B

Grass forage, fodder, and hay 

crop group 17, straw 4.0 None None Revoke: no longer a feed item

There are no ruminant tolerances currently established for pendimethalin. HED recommends 

that tolerances be established in 40 CFR §180.361 (a) (2) for residues of pendimethalin in 

livestock commodities. The residue definition for livestock commodities should be:

Tolerances are established for residues of the herbicide pendimethalin in or on 

livestock commodities, including its metabolites and degradates. Compliance with 

the tolerance levels is to be determined by measuring only the sum of 

pendimethalin (N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine)) and its 

metabolite, 1-(1-ethylpropyl)-5, 6-dimethyl-7-nitro-1H-benzimidazole (metabolite 

6), calculated as the stoichiometric equivalent of pendimethalin, in or on the 

commodity.
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Table 2.2.2-B, below, summarizes the livestock tolerances for this action.

Table 2.2.2-B Tolerance Summary for Pendimethalin in Ruminants. 

Commodity Proposed 

Tolerances 

(ppm)

HEDRecommended 

Tolerance (ppm)

Comments 

Milk 0.04 0.04

Cattle, fat 0.30 0.30

Cattle, meat 0.10 0.10

Cattle, meat byproduct None 3.0 Registrant proposed to exclude 

liver. HED concludes liver 

need not be excluded.

Goats, fat 0.30 0.30

Goats, meat 0.10 0.10

Goats, meat byproduct None 3.0 Registrant proposed to exclude 

liver. HED concludes liver 

need not be excluded.

Horse, fat 0.30 0.30

Horse, meat 0.10 0.10

Horse, meat byproduct None 3.0 Registrant proposed to exclude 

liver. HED concludes liver 

need not be excluded.

Sheep, fat 0.30 0.30

Sheep, meat 0.10 0.10

Sheep, meat byproduct None 3.0 Registrant proposed to exclude 

liver. HED concludes liver 

need not be excluded.

Cattle, meat byproduct except 

liver

3.0 None Liver need not be excluded

Goat, meat byproduct except liver 3.0 None Liver need not be excluded

Horse, meat byproduct except 

liver

3.0 None Liver need not be excluded

Sheep, meat byproduct except 

liver

3.0 None Liver need not be excluded

Cattle, liver 1.5 None Covered by tolerance for cattle 

meat byproduct.

Goat, liver 1.5 None Covered by tolerance for goat 

meat byproduct.

Horse, liver 1.5 None Covered by tolerance for horse 

meat byproduct.

Sheep, liver 1.5 None Covered by tolerance for sheep 

meat byproduct.
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2.2.3. Revisions to Petitioned For Tolerances

HED is recommending tolerance for “meat byproduct” (at 3.0 ppm) based on anticipated 

residues in kidney which contained the highest residue amongst all ruminant tissues and will

therefore cover anticipated residues in liver and fat. BASF proposed setting a tolerance on 

“meat byproduct except liver”, also at 3.0 ppm based on anticipated residues in kidney with a 

separate lower tolerance on liver at 1.5 ppm. HED believes that anticipated residues in liver 

versus kidney (on which the tolerance for meat byproduct is based on) are not significantly 

different given the limited number of data for each tissue and that both are greater than LOQ and 

within about1 ppm of each other. Therefore, a single tolerance on “meat byproduct” without a 

separate tolerance on liver is adequate. 

2.2.4. International Harmonization

The International Residue Limit (IRL) Status Sheet is attached in the Appendix B. There are 

currently no established Codex, Canadian, or Mexican maximum residue limits (MRLs) for the 

proposed new and amended uses, or for the crop group expansions. Therefore, there are no 

issues of international harmonization raised by these petitions.

2.3. Label Recommendations

None. 

3.0. Introduction

Pendimethalin (N-(1-ethylpropyl)-3, 4-dimethyl-2,6-dinitrobenzenenamine) is a selective 

herbicide used to control broadleaf weeds and grassy weed species in a number of crop and noncrop areas as well as on residential lawns and ornamentals. It is a meristematic inhibitor that 

interferes with the plant’s cellular division of mitosis and is generally applied early in the 

growing season as a pre-emergent and early post-emergent herbicide. Formulations include 

liquid, solid, granular, emsulsifiable concentrate, and dry flowables. Pendimethalin is applied by 

aerial, ground, chemigation, and handheld equipment. Pendamethalin is registered by BASF 

Corporation and was first registered in March 1985. The most recent risk assessment was 

performed for hops (01/14/2015, D416285, P.Y, Barnes).
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3.1. Chemical Identity

Table 3.1 Pendimethalin Nomenclature.

Chemical structure

Common name Pendimethalin

Company 

experimental name

BAS 455H (old CL 92533)

IUPAC name N-(1-ethylpropyl)-2,6-dinitro-3,4-xylidine

CAS name N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine

CAS registry number 40487-42-1

End-use product (EP) 3.8 lbs. a.i. gal capsule suspension formulation (equivalent to 450 g a.i. L; Prowl® H2O 

Herbicide; EPA Reg. No 241-418)

Chemical structure of 

Metabolite CL 

202,347

CAS name 4-[(1-ethylpropyl)amino]-2-methyl-3,5-dinitrobenzyl alcohol

CAS registry number 56750-76-6

3.2. Physical/Chemical Characteristics

Pendimethalin is an orange-yellow crystalline solid with a melting point of 54-58 oC. It is 

soluble in chlorinated hydrocarbons and aromatic solvents such as methylene chloride, acetone, 

and xylene, but relatively insoluble in water (<0.5 ppm) at 20 oC. Pendimethalin is stable under 

most acidic and alkaline conditions. Pendimethalin is highly absorbed to the soil/sediment 

particles and is non-volatile. Pendimethalin is stable to hydrolysis, soil photolysis, and anaerobic 

soil metabolism, but degrades slowly under the aqueous photolysis conditions with a calculated

half-life of 17 days.

HN

CH3

CH3

O2N NO2

CH3

CH3
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Table 3.2 Physicochemical Properties of Pendimethalin.

Parameter Value Reference

Melting point/range 54-58 °C (TGAI) Product Chemistry Chapter of 

Pendimethalin RED, DP# 221531, 

12/8/1995, B. Cropp-Kohlligian

pH 4.7 (TGAI) CB# 789, 06/13/1986, G. Makhijani

Density 1.461 g/cm3 (at room temperature) DP#s 271502 and 317053, 

07/12/2006, W. Drew

Water solubility of PAI 0.275 ppm at 25 °C CB# 789, 06/13/1986, G. Makhijani

Solvent solubility of TGAI Solvent g/100 mL at 25 oC

n-Heptane 11.2 

2-Propanol 6.1 

Acetone 161.0

Toluene 128.4 

Methyl alcohol 5.5

Dimethyl sulfoxide 21.4 

Methylene chloride 232.0

CB# 789, 06/13/1986, G. Makhijani

Vapor pressure 1.24 x 10-8 Pa at 20 °C DP#s 271502 and 317053, 

07/12/2006, W. Drew

Dissociation constant, pKa Too small to measure CB# 789, 06/13/1986, G. Makhijani

Octanol/water partition 

coefficient, Log(KOW)

5.18 DP#s 271502 and 317053, 

07/12/2006, W. Drew

UV/visible absorption 

spectrum

UV molecular extinction = 

3.81 x 104at 234 nm,

1.93 x 104at 280 nm. 

DP#s 271502 and 317053, 

07/12/2006, W. Drew

3.3. Pesticide Use Pattern

The subject petitions are for additions/revisions to the Prowl® H2O (EPA Reg. no. 241-418; 

38.7% a.i.) label only. Prowl® H2O is a 3.8 lbs. a.i./gal pendimethalin aqueous capsulated 

suspension (CS) formulation. The requested uses on caneberry subgroub 13-07A and bushberry 

subgroup 13-07B are for application by ground, chemigation, flood, flooded basin, and gravity 

flow irrigation with the individual application rate between 2-6 lb ai/A/year, not to exceed the 

total maximum application rate of 6 lb ai/A/year; the requested PHI is 30 days. The requested 

amended use on grass forage and hay only involves reduction of PHI 45 days (for forage and 

grazing) and 60 days (for hay) to 0-day PHI for forage, hay and grazing. The application on 

grass may be by ground, aerial, chemigation and with dry bulk fertilizer between 1 to 4 lb 

ai/A/year, 
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not to exceed the total maximum application rate of 4 lb ai/A/year. There are no changes in the use rate for the nut tree crop group 14-

12 and its use rate is the same as caneberry and bushberries but with 60-day PHI. See following Table 3.3.1 below for use summary 

profile.

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

Commodity

Product 

Name 

(EPA Reg. 

No.)

Application 

Equipment

Max. Single 

Application 

Rate

(lb a.i/A)

Max. # 

Applicatio

ns

Per 

Season

Max. 

Seasonal 

Application 

Rate

(lb a.i/A)

Timing PHI1 Use Directions and 

Limitations

Caneberry 

Subgroup2

13-07A

Prowl ®

H2O

(241-418)

38.7 % a.i.

Aqueous 

Capsule 

Suspension

Ground, 

Chemigation, 

Flood, Flooded 

Basin, and 

Gravity Flow 

Irrigation 

6 lbs a.i/A

0.3 lb 

a.i/gallon at 

20 gallons of 

spray per acre

3

6 lbs a.i/A per 

year

Apply after pruning in 

fall or spring but before 

new growth. Apply to 

surface beneath plants 

or between plants as 

surface incorporated or 

before weed 

germination. 

Application and 

incorporation must be 

made before 

transplanting 

nonbearing crops.

30

Do not apply by air. Do not 

apply over the top of trees 

or bushes. Do not feed 

forage or graze livestock in 

treated field or planting. 

Bushberry 

Subgroup3

13-07B

Nut Tree Subgroup4

14-12 60

Bermudagrass and 

other perennial 

warm-season 

grasses grown for 

forage, hay 

production, 

pastureland or 

rangeland. 

Ground, Aerial, 

Chemigation, 

Dry Bulk 

Fertilizer

4 lbs a.i/A

40 lbs a.i/ton 

fertilizer

2

4 lbs a.i/A per

year

Apply only to 

established dormant 

perennial grasses before 

weed germination. 

0

Apply uniformly as a 

broadcast spray. Do not 

apply after green up in 

spring before first cutting. 

1PHI = pre-harvest interval 2. Caneberry Subgroup 13-07A includes; Blackberry, Loganberry, Raspberry black, red, and wild. 3 Bushberry Subgroup 13-07B 

includes; Aronia berry, Blueberry high and lowbush, Buffalo currant, Chilean guava, Cranberry highbush, Currant black and red, Elderberry, European barberry, 

Gooseberry, Honeysuckle edible, Huckleberry, Jostaberry, Juneberry, Lingonberry, Native currant, Salal, Sea buckthorn. 4 Nut Tree Subgroup 14-12; includes, 

African nut-tree, Almond, Beechnut, Brazil nut, Brazilian Pine, Bunya, Bur Oak, Butternut, Cajou nut, Candlenut, Cashew, Chestnut, Chinquapin, Coconut, 

Coquito nut, Dika nut, Ginkgo, Guiana Chestnut, Hazelnut (filbert), Heartnut, Hickory nut, Japanese horse-chestnut, Macadamia nut, Mongongo nut, Monkeypot, Monkey puzzle nut, Okari nut, Pachira nut, Peach palm nut, Pecan, Pine nut, Pistachio, Sap
Pendimethalin Human Health Risk Assessment DP No. D428265

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3.4.1. Anticipated Exposure Pathways

Humans may be exposed to pendimethalin in food and drinking water, since pendimethalin may 

be applied directly to growing crops and application may result in pendimethalin reaching 

surface and ground water sources of drinking water. Exposure to pendimethalin may also occur 

in residential or non-occupational settings. Adults and may be exposed by to pendimethalin 

when applying the pesticide to lawns and ornamental plants. Additionally, adults and older 

youth may be exposed to pendimethalin during activities on turf such as mowing or playing golf. 

Children may be exposed to pendimethalin when playing on lawns which have been treated with 

the pesticide. Occupational workers may be exposed to pendimethalin when mixing, loading or 

applying the pesticide or when reentering a treated area to conduct crop maintenance or harvest 

activities. 

3.5. Consideration of Environmental Justice

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

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

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

(http://www.eh.doe.gov/oepa/guidance/justice/eo12898.pdf. As a part of every pesticide risk 

assessment, OPP considers a large variety of consumer subgroups according to well-established 

procedures. In line with OPP policy, HED estimates risks to population subgroups from 

pesticide exposures that are based on patterns of that subgroup’s food and water consumption, 

and activities in and around the home that involve pesticide use in a residential setting. 

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

Survey of Food Intake by Individuals (CSFII) and are used in pesticide risk assessments for all 

registered food uses of a pesticide. These data are analyzed and categorized by subgroups based 

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

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

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

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

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

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

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

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

subgroups.

4.0 Hazard Characterization and Dose-Response Assessment

4.1 Toxicology Studies Available for Analysis

The toxicology database for pendimethalin is complete and adequate to support the proposed 

new uses. Data requirements for the food uses of pendimethalin are listed in the Appendix A, 
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Table A.1. The studies used to evaluate the hazard potential of pendimethalin are listed in 

Appendix A, Table A.2.

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

In a metabolism study (MRID 00046275), when (14C) pendimethalin was administered to rats, 

about 70% of the radioactivity was excreted in the feces and 20% in the urine within 24 hours. 

The excretion of radioactivity in the urine peaked at 6 to 12 hours wherein 11.2% of the dose 

was excreted. The maximum residual radioactivity in the tissues was found in the 6-hour samples 

(except for fat at 12 hours). The levels of radioactivity detected in liver, kidney, muscle, fat, and 

blood at 6 hours were 29.8, 16.9, 1.3, 12.2, and 5.4 ppm, respectively. Within 96 hours the 

radioactivity found in the tissues was 0.3 ppm or less, except for fat which was 0.9 ppm. The 

major portion of the radioactivity that was excreted in the feces was identified as the parent 

compound. Pendimethalin is metabolized in rats mainly through oxidation of the 4 methyl groups 

attached to the benzene ring as well as oxidation of the alkyl side chain of the N-substituted 

dinitroaniline compound.

4.2.1 Dermal Absorption

There were no appropriate dermal absorption or toxicity studies available to allow an estimation 

of the dermal absorption by a route-to-route comparison of toxicity. Based on structurally related 

chemicals (oryzalin, trifluralin, and ethalfluralin) with dermal absorption studies (in monkeys) 

indicating absorption rates of 2.3%, ~1%, and 2.8%, respectively. The solubility (water) for 

pendimethalin and these related chemicals are also similar at 0.5 ppm, 2.5 ppm, 0.3 ppm and < 1 

ppm, respectively. Therefore, for risk assessment purposes, an estimate of 3% was applied. This 

dermal absorption rate is comparable to those identified for related chemicals.

4.3 Toxicological Effect

A developmental thyroid study was conducted to see if there is a quantitative and/or qualitative 

effect between mothers and pups on thyroid response. The thyroid is the target organ for 

pendimethalin. Thyroid toxicity in chronic and subchronic rat and mouse studies was manifested 

as alterations in thyroid hormones (decreased total T4, and T3, increased percent of free T4 and 

T3), increased thyroid weight, and microscopic thyroid lesions (including increased thyroid 

follicular cell height, follicular cell hyperplasia, as well as follicular cell adenomas). Also, 

decreased body weights and increased absolute and relative liver weights were noted in animals 

exposed to pendimethalin. The results showed no differences between maternal and 

developmental effect on thyroid and dose response. A developmental thyroid study was 

conducted to see if there is a quantitative and/or qualitative effect between mothers and pups on 

thyroid response. The results showed no differences between maternal and developmental effect 

on thyroid and dose response.

There is no evidence that pendimethalin is a developmental, reproductive, neurotoxic, or 

immunotoxic chemical.
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Pendimethalin is classified as a “Group C”, possible human carcinogen based on a statistically 

significant increased trend and pair-wise comparison between the high dose group and controls 

for thyroid follicular cell adenomas in male and female rats.

Pendimethalin has a low acute toxicity via the oral, dermal, or inhalation route (Toxicity 

Category III or IV). It is not a dermal or eye irritant, and is not a dermal sensitizer.

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

The toxicity database is complete, there is no evidence of increased qualitative or quantitative 

susceptibility in the young and exposure estimates are unlikely to underestimate risk; therefore, 

10-fold FQPA Safety Factor is reduced to 1x. 

4.4.1 Completeness of the Toxicology Database

The toxicology database for pendimethalin is complete and adequate to support risk assessments. 

4.4.2. Evidence of Neurotoxicity

There is no evidence of neurotoxicity resulting from pendimethalin exposure. In an acute 

neurotoxicity study, FOB findings and reduced motor activity were observed on Day 0 only at 

300 and 1000 mg/kg. However, these findings were considered an impairment of the overall 

condition of the animals following treatment, rather than direct neurotoxic effects of the 

pendimethalin exposure based on the absence of any neuro-histopathological changes in the 

treated animals and the transient nature of the observed FOB and neurobehavioral assessments. 

In a subchronic neurotoxicity study, no neurotoxic effects were observed in rats feeding 

pendimethalin up to 5400 ppm for 90 days. In addition, the toxicology database does not reveal 

any evidence of neurotoxic clinical signs, changes in brain weight, or histopathology of the 

nervous system in any study with pendimethalin. 

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

There was no indication of pre- and/or post-natal qualitative or quantitative increased 

susceptibility in the developmental studies in rats and rabbits or the 2-generation reproduction 

studies in rats. In addition, a developmental thyroid toxicity study demonstrated that there is no 

potential thyroid toxicity following pre- and/or post-natal exposure to pendimethalin.

4.4.4. Residual Uncertainty in the Exposure Database

There are no residual uncertainties in the exposure database. Since the dietary and non-dietary 

exposure estimates were based on several conservative assumptions, HED does not believe the 

exposure assessment underestimates risk. These assumptions include tolerance-level residues 

and 100% crop treated estimates for all commodities. Furthermore, conservative, upper-bound 

assumptions were used to determine exposure through drinking water and residential sources, 

such that these exposures have not been underestimated.
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4.5 Toxicity Endpoint and Point of Departure Selections

4.5.1 Toxicity Endpoint and Point of Departure Selections

Acute Dietary Endpoint for the General Population: In an acute neurotoxicity study in rats 

(MRID 48695601), reduced motor activity was observed at 300 mg/kg (LOAEL) with a NOAEL 

of 100 mg/kg. The route and a single exposure of this study are appropriate for acute dietary risk 

assessment. The UF is 100x (10x for interspecies extrapolation, 10x for intraspecies variation, 

and 1x for FQPA Safety Factor). The acute population adjusted dose (aPAD) for the general

population is 1 mg/kg.

Acute Dietary Endpoint for Female 13-49 Years of Age: No appropriate endpoint was identified 

from any of the studies in the database, including developmental toxicity studies in rats and 

rabbits. Consequently, it was determined that there was no basis for selecting a separate dose and 

endpoint for an acute POD for females 13-49 years of age.

Chronic Dietary Endpoint for the General Population: Three studies (a 92-day thyroid function 

study, a 56-day thyroid function study and a 14-day intra-thyroid metabolism study in rats) were

considered co-critical in establishing a POD for chronic dietary risk assessment. All studies 

reflecting thyroid toxicity, HED has determined that these studies collectively support a NOAEL 

of 10 mg/kg/day and a LOAEL of 31 mg/kg/day for thyroid effects include several hormonal and 

histological thyroid changes and thyroid hormonal effects and should be used as the POD for all 

durations and exposure scenarios. An UF of 30x (3x for interspecies extrapolation and 10x for 

intraspecies variation) is applied to the NOAEL of 10 mg/kg/day to obtain a chronic reference 

dose (cRfD) of 0.3 mg/kg/day. The interspecies UF (used to account for animal to human 

differences in toxicokinetics and toxicodynamics) was reduced to 3X with respect to observed 

thyroid effects in the rat because of several important quantitative dynamic differences between 

rats and humans with respect to thyroid function (Interim Guidance on Thyroid Disrupting 

Pesticides, dated 11/01/2005). The FQPA factor is reduced to1x. The chronic population 

adjusted dose (cPAD) is 0.3 mg/kg/day.

Incidental Oral Exposure (Short and Intermediate-Term): HED evaluated the toxicity database 

for pendimethalin and concluded that all available studies reflecting thyroid toxicity should be 

considered co-critical for selection of PODs, regardless of duration of exposure, since thyroid 

effects have a demonstrated early on-set (before 14 days). Therefore, HED has determined that 

these studies collectively support a NOAEL of 10 mg/kg/day and a LOAEL of 31 mg/kg/day for 

thyroid effects include several hormonal and histological thyroid changes and thyroid hormonal 

effects and should be used as the POD for all durations and exposure scenarios with the 

exception of the acute dietary endpoint.

Dermal Exposure (Short and Intermediate-Term): There was a 21-day dermal toxicity study 

available with a NOAEL of 1000 mg/kg (the limit dose); however, thyroid function was not 

measured in this study. Therefore, oral toxicity study was selected for this exposure scenario. 

The same rationale as stated in the incidental oral exposure section is applied to this exposure 

scenario. These co-critical studies collectively support a NOAEL of 10 mg/kg/day and a LOAEL 
Pendimethalin Human Health Risk Assessment DP No. D428265

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of 31 mg/kg/day for thyroid effects include several hormonal and histological thyroid changes 

and thyroid hormonal effects and should be used as the POD for all durations and exposure 

scenarios. Additionally, for risk assessment purposes, a dermal absorption factor of 3% should be 

used to estimate risk since these assessments for the routes of exposure are derived from POD 

selected from oral studies.

Inhalation Exposure (Short and Intermediate-Term): There was no inhalation study available 

except the acute inhalation study (Toxicity Category IV). Therefore, oral toxicity study was 

selected for this exposure scenario. The same rationale as stated in the incidental oral exposure 

section is applied to this exposure scenario. These co-critical studies collectively support a 

NOAEL of 10 mg/kg/day and a LOAEL of 31 mg/kg/day for thyroid effects include several 

hormonal and histological thyroid changes and thyroid hormonal effects and should be used as 

the POD for all durations and exposure scenarios. Additionally, for risk assessment purposes, an 

inhalation absorption factor of 100% should be used to estimate risk since these assessments for 

the routes of exposure are derived from POD selected from oral studies. 

Table 4.5.1. Toxicological Doses and Endpoint for Pendimethalin Human Health Risk Assessment

Exposure/Scenario Point of 

Departure

Uncertainty/FQPA 

Safety Factors

RfD, PAD, Level of 

Concern for Risk 

Assessment

Study and Toxicological 

Effects

Acute Dietary

(Females 13-49)

No appropriate endpoint was identified from any of the studies in the database, including 

developmental toxicity studies in rats and rabbits.

Acute Dietary

(General population 

including infants 

and children)

NOAEL=100 

mg/kg

UFA = 10X

UFH = 10X

FQPA SF = 1X

Total UF = 100X

Acute RfD = 1 

mg/kg/day

aPAD = Acute RfD

 FQPA SF

= 1 mg/kg/day

Acute neurotoxicity study 

(MRID 48695601).

The LOAEL=300 mg/kg, 

based on reduced motor 

activity for males and 

females on Day 0.

Chronic Dietary (all 

populations) 

NOAEL = 10 

mg/kg/day

UFA = 3X 

UFH = 10X 

FQPA SF = 1X

Total UF = 30X

Chronic RfD = 0.3 

mg/kg/day

cPAD = Chronic RfD

 FQPA SF

= 0.3 mg/kg/day

92- Day thyroid function 

study in rats (MRID 

42054601); 56- day 

thyroid study in rats 

(MRID 43135001); 14-

day intra thyroid 

metabolism study in rats 

(MRID 43135003).

LOAEL = 31 mg/kg/day 

based on hormonal and 

histopathological changes 

in the thyroid. 

Incidental Oral 

Exposure Oral

Short- Term (1- 30 

days) 

Intermediate – Term

(1-6 months)

NOAEL = 10 

mg/kg/day

UFA = 3X 

UFH = 10X 

FQPA SF = 1X

Total UF = 30X 

Residential LOC = 30

Occupational LOC = 30

The same as the chronic 

dietary.

Dermal 

Short- Term (1- 30 

days) 

Intermediate – Term

NOAEL = 10 

mg/kg/day

UFA = 3X 

UFH = 10X 

FQPA SF = 1X

Total UF = 30X 

Residential LOC = 30

Occupational LOC = 30

The same as the chronic 

dietary.
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Table 4.5.1. Toxicological Doses and Endpoint for Pendimethalin Human Health Risk Assessment

Exposure/Scenario Point of 

Departure

Uncertainty/FQPA 

Safety Factors

RfD, PAD, Level of 

Concern for Risk 

Assessment

Study and Toxicological 

Effects

(1-6 months)

Dermal Absorption 

= 3%

Inhalation 

Short- Term (1- 30 

days) 

Intermediate – Term

(1-6 months)

NOAEL = 10 

mg/kg/day

UFA = 3X 

UFH = 10X 

FQPA SF = 1X

Total UF = 30X

Inhalation 

Absorption = 100%

Residential LOC = 30

Occupational LOC = 30

The same as the chronic 

dietary.

Cancer (oral, 

dermal, inhalation)

Group C, possible human carcinogen based on a statistically significant increased trend and 

pair-wise comparison between the high dose group and controls for thyroid follicular cell 

adenomas in male and female rats. A non-quantitative approach (i.e., non-linear, RfD 

approach) was recommended by the Cancer Peer Review Committee since mode of action 

studies are available.

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

human population (intra-species), FQPA SF = FQPA safety factor, NOAEL = no observed adverse effect level, LOAEL = lowest observed 

adverse effect level, PAD = population adjusted dose (a = acute, c = chronic), RfD = reference dose, MOE = margin of exposure, LOC = level of 

concern, NA = Not Applicable. 

4.5.2. Recommendation for Combining Routes of Exposures for Risk Assessment

Since the same three studies were used to select endpoints and doses for risk assessment for oral, 

dermal and inhalation routes of exposure (all durations), the exposures and risks from these 

exposure routes should be aggregated. 

4.5.3. Cancer Classification and Risk Assessment Recommendation

The CARC classified pendimethalin (03/18/1992 and re-affirmed 11/01/1999) as a "Group C", 

possible human carcinogen based on a statistically significant increased trend and pair-wise 

comparison between the high dose group and controls for thyroid follicular cell adenomas in 

male and female rats. The Committee also recommended a non-quantitative approach (i.e., nonlinear, RfD approach) since mode of action studies are available that demonstrate that the thyroid 

tumors are due to a thyroid-pituitary imbalance, and also since pendimethalin was shown to be 

non-mutagenic in mammalian somatic cells and germ cells. The chronic risk assessment is 

considered to be protective of any cancer effects; therefore, a separate quantitative cancer 

aggregate risk assessment is not required.

4.6. Endocrine Disruption

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

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

chronic 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, 
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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 most recent re-registration decision for pendimethalin, 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), 

pendimethalin is subject to the endocrine screening part of the Endocrine Disruptor Screening 

Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list of 

chemicals identified for EDSP screening was published on June 14, 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 

website2.

5.0 Dietary Exposure and Risk Assessment 

5.1 Residues of Concern Summary 

The current tolerance expression for pendimethalin in 40 CFR §180.361 includes the combined 

residues of pendimethalin and its 3,5-dinitrobenzyl alcohol metabolite (CL 202,347) for plant 

commodities. The HED Pendimethalin team has reviewed the newly submitted ruminant feeding 

study and consulted with the co-chairs of the Residue of Concern Knowledgebase Subcommittee 

(ROCKS; DP428264, P.Y. Barnes, 08/06/2015) to determine that the residues of concern for 

both tolerances setting and risk assessment in ruminants only is the parent compound, 

 

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

2 http://www.epa.gov/endo/
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pendimethalin and its metabolite, 1-(1-ethylpropyl)-5, 6-dimethyl-7-nitro-1H-benzimidazole 

(also known as metabolite 6). Table 5.1 provides a summary of the residues of concern for 

pendimethalin. The dietary burden for poultry remains low, and based on the available 

metabolism data, HED concludes that residues in poultry commodities are not likely (40CFR 

§180.6(a)(3)).

5.2. Food Residue Profile

Pendimethalin is a registered herbicide for agricultural uses and is applied either pre or early post 

emergence. It is a meristematic inhibitor “growth retarder” that interferes with the plant’s 

cellular division of mitosis, controlling/preventing annual grasses and weeds. Once 

pendimethalin is absorbed by the roots or shoots, translocation to foliage is extremely limited. 

Residues of pendimethalin and/or its metabolite at harvest are usually very low or nondetectable, (e.g., below the level of quantification). The study showed that the residues are 

transferable to ruminant tissue and milk. 

5.3. Water Residue Profile

The estimated drinking water concentrations (EDWCs) for pendimethalin were generated using 

the Surface Water Concentration Calculator (SWCC) computer model, the Pesticide Root Zone 

Model for Groundwater (PRZM-GW), and the Screening Concentration in Ground Water (SCIGROW) model. Both point estimates and distributions of water residues were provided. A 

comparison was made between output from current EFED models for pendimethalin for the 

proposed uses on caneberry, bushberry, tree nut group (6.0 lbs ai/ A), and cool- and warm season 

forage grasses (4.0 lbs ai/A) with the output from the currently registered use on grapes (6.0 lbs

ai/A). Grapes has the highest application rate of all currently registered (See Table 5.3).

Table 5.1 Summary of Metabolites and Degradates included in the Pendimethalin Risk Assessment and 

Tolerance Expression

Matrix Residues included in Risk Assessment Residues included in

Tolerance Expression

Plants

Primary Crop Pendimethalin and alcohol metabolite, 4-[(1-

ethylpropyl)amino]-2-methyl-3,5-dinitrobenzyl alcohol 

(CL 202347)

Pendimethalin 

and (CL 202347) Rotational Crop

Livestock Ruminant Pendimethalin and metabolite 6, 1-(1-ethylpropyl)-5, 6-

dimethyl-7-nitro-1H-benzimidazole)

Pendimethalin and 

metabolite 6 

Water Pendimethalin Not applicable
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Table 5.3 EDWCs Scenario for Pendimethalin 

Drinking Water 

Source

(Model) 

1 in 10 year Annual Peak 

Concentration 

1 in 10 year Annual 

Mean Concentration 

Average Stimulation 

Concentration 

(μg/L) (μg/L) (μg/L)

Pendimethalin EDWCs for the New York Grape Scenario

Surface Water a 

(SWCC) 96.4 9.73 8.16

Ground Water b

PRZM-GW b 4.38 E-09 -- 1.88 E-13

Pendimethalin EDWCs for the Cool and Warm Season Forage Grasses Scenario

Surface Water 

(SWCC) 21.9 1.47 1.25

Ground Water 

PRZM-GW 1.78 E-10 -- 3.09 E-13

a For the SWCC model

 The NY grape scenario was used to represent berries.

 The CA rangeland hay, and the OR grass seed scenarios were used to represent forage grasses. The OR 

grass seed scenario resulted in higher EECs than the CA scenario; and it is presented here.

b: For the PRZM-GW model; the following available scenarios were used to represent ornamentals and turf:

 FL potato, GA coastal, NC coastal, and WI sand. The NC scenario gave the highest EDWCs.

--: The chemical did not reach groundwater even after running the model with an extended 100-year weather file.

5.4. Dietary Risk Assessment

5.4.1. Description of Residue Data Used in Dietary Assessment

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

conducted for pendimethalin using the Dietary Exposure Evaluation Model software with the 

Food Commodity Intake Database (DEEM-FCID) Version 3.16. This software uses 2003-2008 

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

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

unrefined acute and chronic analyses include all existing and proposed uses of pendimethalin and 

are based on tolerance-level residues; 100% crop treated assumptions for all of the pendimethalin

use commodities in this assessment and DEEMTM default processing factors or empirical 

processing factors where available. The drinking water point estimates provided by EFED are 

modeled estimates and were generated using the most conservative model available for the 

proposed crops. The acute and chronic approach to dietary risk exposure analysis will not 

underestimate risk to the general U.S. population or any population subgroup.

5.4.2. Percent Crop Treated Used in Dietary Assessment
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Percent crop treated refinements were not used in the acute or chronic dietary assessments.. 

5.4.3. Acute Dietary Risk Assessment

The acute aggregate (food and drinking water) dietary exposure estimates are below HED’s level 

of concern (i.e., <100% of the aPAD) for the U.S. population and all population subgroups. 

Combined dietary exposure from food and drinking water concentrations at the 95th percentile of 

exposure is <1% of the aPAD for the U.S. population and 2% of the aPAD for all infants <1 year 

old, the highest exposed population subgroup (See Table 5.4.6).

5.4.4. Chronic Dietary Risk Assessment

The chronic aggregate dietary exposure estimate for food and drinking water are below HED’s 

level of concern. The estimated food and drinking water is <1% of the chronic population adjusted 

dose (cPAD) for the U.S. population and 2% of the cPAD (See Table 5.4.6). 

5.4.5. Cancer Dietary Risk Assessment

A non-quantitative approach was recommended by the Cancer Peer Review Committee since 

mode of action studies are available to demonstrate that the thyroid tumors are due to a thyroidpituitary imbalance, and also since pendimethalin was shown to be non-mutagenic in mammalian 

somatic cells and germ cells. The chronic dietary risk assessment is considered to be protective 

of any cancer effects; such that, a separate quantitative cancer aggregate risk assessment is not 

required.

5.4.6. Summary Table 

Table 3. Summary of Dietary (Food and Drinking Water) Exposure and Risk for Pendimethalin

Population Subgroup

Acute Dietary1

(95th Percentile) Chronic Dietary1 Cancer

Dietary 

Exposure 

(mg/kg/day)

% 

aPAD*

Dietary 

Exposure

(mg/kg/day)

% cPAD*

Dietary 

Exposure

(mg/kg/day)

Risk

General U.S. Population 0.009126 < 1 0.002074 < 1

Not 

applicable

Not 

applicable

All Infants (< 1 year old) 0.020314 2.0 0.003844 1.3

Children 1-2 years old 0.017759 1.8 0.007019 2.3

Children 3-5 years old 0.013994 1.4 0.005254 1.8

Children 6-12 years old 0.009638 < 1 0.003130 1.0

Youth 13-19 years old 0.006663 < 1 0.001751 < 1
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Table 3. Summary of Dietary (Food and Drinking Water) Exposure and Risk for Pendimethalin

Population Subgroup

Acute Dietary1

(95th Percentile) Chronic Dietary1 Cancer

Dietary 

Exposure 

(mg/kg/day)

% 

aPAD*

Dietary 

Exposure

(mg/kg/day)

% cPAD*

Dietary 

Exposure

(mg/kg/day)

Risk

Adults 20-49 years old 0.007299 < 1 0.001609 < 1

Adults 50-99 years old 0.006631 < 1 0.001516 < 1

Females 13-49 years old 0.007416 < 1 0.001581 < 1

*The subpopulation(s) with the highest risk estimates are bolded. 

6.0 Residential (Non-Occupational) Exposure/Risk Characterization

There are no proposed new residential uses for pendimethalin. Registered residential uses were 

assessed in the 2012 risk assessment and occupational and residential exposure assessment 

(D402406) which reflected updates to HED’s 2012 Residential SOPs2along with policy changes 

for body weight assumptions. The 2012 assessment included short-term dermal and inhalation 

risk estimates for residential handler applications of pendimethalin to gardens, ornamentals, and 

lawns as well as short-term dermal and oral post-application risk estimates from physical 

activities on treated lawns, golfing, mowing, gardening, accidental granular ingestion, and handto-mouth behavior. The residential handler and post-application risk estimates did not exceed 

HED’s level of concern (MOEs ≥ 30). The lowest MOE for adult residential handlers was from 

loading and applying granular pendimethalin with a belly grinder (MOE =670). The lowest 

margin of exposures for post application activities were adult dermal exposure to treated gardens 

(MOE =130) and children ages 1 >2 years old physical activities on treated turf (dermal 

MOE=170 and hand-to-mouth MOE =240).

6.1 Residential Risk Estimates for Use in Aggregate Assessment

HED believes that combining exposures resulting from adult handler and post-application 

activities would result in an overestimate of adult exposure. HED selected the most conservative 

adult dermal post-application exposure (MOE = 130) as the representative source of residential 

exposure to be combined with the dietary exposure for the aggregate assessment. The children’s 

oral exposure is based on post-application incidental oral hand-to-mouth exposures plus dermal 

post-application exposure from physical activities on turf (MOE = 240 and 170, respectively). 

Table 6.1 summarizes the residential exposure scenarios that are to be used for estimating 

aggregate exposure.

 

2 Available: http://www.epa.gov/pesticides/science/residential-exposure-sop.html
Pendimethalin Human Health Risk Assessment DP No. D428265

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Table 6.1. Combined Short-Term Residential Exposure and Risk Estimates for Pendimethalin 

Use Site

Handler 

Dermal Handler Inhalation

Postapplication 

Dermal 

Incidental Oral 

Hand-to-Mouth 

Combined 

Exposure for 

Aggregate Risk

Doseb MOEc Dosed MOEe Dosef MOEc Doseg MOEh Dose MOEi

Adults –

Ornamentals 

(Granular) 

via belly 

grinder

4 lb ai/acre a

0.015 670 5.4E-05 180,000 0.078 130 N/A 0.078 130j

Children 1 < 

2 Years Old 

- Turf 

(Liquids)

N/A N/A 0.060 170 0.042 240 0.102 100

a. Belly grinder assumption of 1200 sq ft per day is calculated to be equivalent to 0.023 acres ((1200 sq ft/day ) x (43,560 

sq ft/1 acre) = 0.023 acres/day).

b. Handler Dermal Dose = Dermal Unit Exposure (mg/kg) x Application Rate (4 lb ai/acre) x Amount Treated or Handled 

x DAF (3%)/BW (80 kg).

c. Dermal MOE = Dermal NOAEL (10mg/kg/day)/Dermal Dose (mg/kg/day).

d. Handler Inhalation Dose = Dermal Unit Exposure (mg/kg) x Application Rate (4 lb ai/acre) x Amount Treated or 

Handled /BW (80 kg).

e. Handler Inhalation MOE = Inhalation NOAEL (10 mg/kg/day)/ Inhalation Dose (mg/kg/day)

f. Dermal Dose (mg/kg/day) = TTR (μg/cm2) x 0.001 (mg/μg) x short-term TC (cm2/hr) x ET (hr/day) x DAF (3%) / BW 

(kg).

g. Hand-to-Mouth Dose (mg/kg/day) = E = [HR * (FM * SAH) * (ET * N_Replen) * (1- (1- SE)

(Freq_Replen/N-Replens))].

h. Oral MOE = NOAEL (18.8 mg/kg/day) / Oral Dose (mg/kg/day).

i. Adult Total MOE = Total MOE = 1/ [(1/Dermal MOE) + (1/Inhalation MOE)]. Children 1<2 years old Total MOE = 

1/[(1/Dermal MOE) + (1/Incidental Oral MOE)]

j. HED did not combine exposure resulting from adult handler and post-application exposure resulting from treated lawns 

and/or golfing because of the conservative assumptions and inputs within each estimated exposure scenario.

6.2 Spray Drift

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

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

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

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

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

Call-In issued by EPA), EPA Regional Offices and State Lead Agencies for pesticide regulation 

and other parties to develop the best spray drift management practices (see the Agency’s Spray 

Drift website for more information). 3 The Agency has also developed a policy on how to 

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

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

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

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

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

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

of indirect non-occupational exposure to drift. 

 

3 Available: http://www.epa.gov/opp00001/factsheets/spraydrift.htm 
Pendimethalin Human Health Risk Assessment DP No. D428265

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6.3 Residential Bystander Post-Application Inhalation Exposure

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

individuals nearby pesticide applications. The Agency sought expert advice and input on issues 

related to volatilization of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act 

Scientific Advisory Panel (SAP) in December 2009, and received the SAP’s final report on 

March 2, 2010 (http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html). The 

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

subsequent Volatilization Screening Analysis 

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

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

studies, route-specific inhalation toxicological studies) or further analysis is required for 

pendimethalin.

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. For pendimethalin, potential exposures from food, drinking water, and 

residential scenarios were aggregated. 

7.1 Acute Aggregate Risk

The aggregate acute risk estimate, by definition includes exposure to residues of pendimethalin 

in food and water only. The acute risk estimate for the U.S. population and all other population 

subgroups, resulting from aggregate exposure to pendimethalin in food and drinking water, is 

below HED’s LOC. The food and drinking water exposure estimates are <1% of the aPAD for 

the U.S. general population, and 2% for the most highly exposed life stage, all infants <1 year 

old. Therefore there are no acute aggregate risks of concern. 

7.2 Short-Term Aggregate Risk 

There is potential short-term exposure to pendimethalin via dietary (food and water) (which is 

considered background exposure) and residential exposure pathways. For adults, these pathways 

lead to exposure via oral as well as dermal and inhalation routes. The most conservative 

scenario was chosen for each population (i.e. combined hand-to-mouth and dermal exposure 

from treated turf for children 1< 2 years old). For a description of the residential exposure 

scenarios considered in the aggregate assessment, see Section 6.0.
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The adult aggregate MOE (for males and females) which combines average dietary residues with 

dermal exposure from post-application exposure to treated ornamentals is 130, which indicates 

that exposure and risk do not exceed HED’s level of concern (MOE > 30). The aggregate MOE 

for children 1< 2 years old, which combines average dietary residues with dermal and incidental 

oral exposures from treated turf is 92, which indicates that exposure and risk do not exceed 

HED’s LOC (MOE > 30). 

Table 7.2 Short-Term Aggregate Risk Calculations for Pendimethalin

Life stage

Short-Term Scenario

NOAEL 

mg/kg/day LOC1

Max 

Allowable 

Exposure2

mg/kg/day

Average 

Food and 

Water 

Exposure 

mg/kg/day3

Residential 

Exposure 

mg/kg/day4

Total 

Exposure 

mg/kg/day5

Aggregate 

MOE (food, 

water, and 

residential)6

Adult 10 30 0.33 0.001609 0.078 0.080 130

Child 10 30 0.33 0.007019 0.102 0.109 92

1

Intraspecies factor= 10x; Interspecies factor = 3x 2 Maximum Allowable Exposure (mg/kg/day) = NOAEL (10 

mg/kg/day)/LOC (30). 3Average food and water exposure from chronic dietary exposure for adults 20-49 yrs and 

children 1-2 yrs old (see table 5.4.6). 4 Child Residential Exposure = [Oral exposure (0.042 mg/kg/day) + Dermal 

exposure (0.060 mg/kg/day) = 0.102 mg/kg/day (Table 6.1). 

5 Total Exposure = (Avg (Food & Water) Exposure + 

Residential Exposure). 6 Adult Aggregate MOE = [NOAEL (10 mg/kg/day)/ (Total Exposure (0.08 mg/kg/day)]; 

Child Aggregate MOE= [NOAEL (10 mg/kg/day)/ (Total Exposure (0.109 mg/kg/day)]

7.3 Intermediate-Term Aggregate Risk

Intermediate-term exposures to pendimethalin are not likely because of the intermittent nature of 

applications by homeowners (e.g., garden sprays). Therefore a separate intermediate term 

aggregate assessment was not conducted.

7.4 Chronic Aggregate Risk

Chronic exposure is not expected for the residential (dermal and inhalation) exposure pathways. 

Therefore, the chronic aggregate risk would be equivalent to the chronic dietary exposure 

estimate. Refer to Section 5.4.4 for the chronic dietary (food and drinking water) exposure 

assessment. There are no chronic aggregate risks of concern.

7.5 Cancer Aggregate Risk

Pendimethalin is considered a “possible human carcinogen”. Quantification of risk using a nonlinear approach; i.e., RfD/PAD, will adequately account for all chronic toxicity, including 

carcinogenicity, that could result from exposure to pendimethalin. Since there are no chronic 

aggregate risks of concern (Section 7.4), there are no cancer aggregate risks of concern.

8.0. Cumulative Exposure/Risk Characterization
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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 pendimethalin and any other substances and pendimethalin does not appear to produce a toxic 

metabolite produced by other substances. For the purposes of this tolerance action, therefore, 

EPA has not assumed that pendimethalin 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 Handler Exposure/Risk Estimates

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

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

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

(amount of chemical used in each application), the kinds of equipment used, the target being 

treated, and the level of protection used by a handler can cause exposure levels to differ in a 

manner specific to each application event. 

Based on the anticipated use patterns and current labeling, types of equipment and techniques 

that can potentially be used, occupational handler exposure is expected from the proposed crop 

conversions and expansions. Pendimethalin application to Bermudagrass was originally assessed 

in 2009 (D371025). Occupational handler exposure risk estimates were calculated for total 

(combined dermal and inhalation) short- and intermediate-term exposures for the following 

exposure scenarios. 

 Mixing/loading liquid formulations for ground, chemigation, and aerial applications,

 Applying sprays via ground, and aerial applications, and 

 Flagging for aerial spray applications.

Estimates of dermal and inhalation exposure were calculated for various levels of PPE. The 

Prowl ® H2O product labels direct mixers, loaders, applicators and other handlers to wear longsleeved shirts and long pants, chemical-resistant gloves, and shoes plus socks. The short- and 

intermediate term combined dermal and inhalation did not exceed HED’s level of concern (MOE 

≥ 30) with label mandated PPE of single layer baseline and gloves. Body weight assumptions 

have increased from the 70 kg used in the 2009 assessment to 80 kg.

The proposed crop expansions to bushberries, caneberries, and tree nut subgroups are expected 

have identical handler exposure pattern (i.e., ground directed layby between rows) and maximum 

application rate (i.e., 6 lb ai/acre) as the previous citrus and other tree crops already assessed in the 

2012 registration review (D402406). Occupational handler combined (dermal and inhalation) 

short- and intermediate-term exposure risk estimates were calculated for the following exposure 

scenarios. 
Pendimethalin Human Health Risk Assessment DP No. D428265

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1) Mixing/loading liquid formulations for ground and chemigation applications,

2) Applying sprays via groundboom equipment,

3) Mixing/loading/applying liquids via mechanically-pressurized handgun,

4) Mixing/loading/applying liquids via manually pressurized handwand, and

5) Mixing/loading/applying liquids via handgun sprayer.

Combined dermal and inhalation risk estimates (MOEs) were not of concern (MOEs ≥ 30) with 

baseline dermal protection and gloves. See Table in Appendix D for a summary of the dermal 

and inhalation exposures and risk estimates for Bermudagrass and crop groups occupational 

pesticide handlers.

9.2 Occupational Post-application Exposure/Risk Estimates

HED uses the term post-application to describe exposures that occur when individuals are 

present in an environment that has been previously treated with a pesticide (also referred to as reentry exposure). Such exposures may occur when workers enter previously treated areas to 

perform job functions, including activities related to crop production, such as scouting for pests 

or harvesting. Post-application exposure levels vary over time and depend on such things as the 

type of activity, the nature of the crop or target that was treated, the type of pesticide application, 

and the chemical’s degradation properties. In addition, the timing of pesticide applications, 

relative to harvest activities, can greatly reduce the potential for post-application exposure.

9.2.1 Occupational Post-application Inhalation Exposure/Risk Estimates

There are multiple potential sources of post-application inhalation exposure to individuals 

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

include volatilization of pesticides and resuspension of dusts and/or particulates that contain 

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

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

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

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

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

Volatilization Screening Analysis (http://www.regulations.gov/#!docketDetail;D=EPA-HQOPP-2014-0219). During Registration Review, the Agency will utilize this analysis to determine 

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

required for pendimethalin.

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 
Pendimethalin Human Health Risk Assessment DP No. D428265

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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 Occupational Post-Application Dermal Exposure/Risk Estimates

The proposed crop subgroups; bushberry 13-07B, caneberry 13-07A and tree nut 14-12 were not 

assessed for dermal post-application exposure because of use pattern and review of submitted 

chemical specific study. Pendimethalin is applied as a pre-emergent/early post-emergent 

herbicide and not directly applied to the foliage of the proposed crop groups but rather to the 

layby or between rows. The chemical specific study on post-application foliage supports that 

post application exposure to crops from pendimethalin layby application is negligible (See 

Dislodgeable Foliar Residues section below). 

The application to Bermudagrass is expected to be a post emergent foliar spray and not 

represented by the DFR study. The fraction of pendimethalin retained on foliage is assumed to 

be 25% (0.25) on the day of application (= % DFR, after initial treatment) for agricultural crops. 

This fraction is assumed to further dissipate at the rate of 10% (0.1) per day on following days. 

In 2009 the estimated occupational dermal post application risks to treated Bermudagrass using 

default dissipation assumptions did not exceed HED’s level of concern (MOEs ≥ 30) on the day 

of treatment for early post application activities including scouting and hand laying irrigation.

Dislodgeable Foliar Residues (DFR): 

Based on a review of the available data (C. Jarvis, 08/01/2001, D262264), it was decided that the 

DFR data for sugarcane and tobacco (MRID 44969902) treated with PROWL 3.3 EC Herbicide 

in Washington and Louisiana would be used to assess non-foliar pendimethalin layby 

applications (ground-directed sprays). However the DFR study residues were determined to be 

less than the limit of quantitation (LOQ) in most samples. 

Restricted Entry Interval

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

Pendimethalin is classified as Toxicity Category IV via the dermal route and skin irritation 

potential. It is not a skin sensitizer. Under 40 CFR 156.208 (c) (2) (iii), ai’s classified as Acute 

III or IV for acute dermal, eye irritation and primary skin irritation are assigned a 12-hour REI. 

Therefore, the [156 subpart K] Worker Protection Statement interim REI of 12 hours is adequate 

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

10 References
Pendimethalin Human Health Risk Assessment DP No. D428265

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Residue Chemistry References

Pendimethalin. Human Health Risk Assessment for New Use on Hops, and Crop Subgroup 

Conversions/Expansions for Low Growing Berry Subgroup 13-07G, Onion, Bulb Subgroup 3-

07A, Onion, Green Subgroup 3-07B, and Sunflower Subgroup 20B; Crop Group Expansions 

for Citrus Fruit, Group 10, Pome Fruit, Group 11, Stone Fruit, Group 12, and Fruiting 

Vegetable, Group 8; DP Barcode 416285; P. Yvonne Barnes; 01/14/2015.

Pendamethalin: Petition Section 3 Registration and Establishment of Permanent Tolerance of 

Pendimethalin for Uses on Caneberry Subgroup 13-07A, Bushberry Subgroup 13-07B, and 

Livestock Commodities. Crop Group Conversion for Tree Nut Crop Group 14. Amend the 

Pre-Harvest Interval and Establishment of Tolerances for Pendimethalin in/on Grass Forage, 

Fodder, and Hay (Crop Group 17). Summary of Analytical Chemistry and Residue Data; DP 

Barcodes D420013, M. Sahafeyan and P. Yvonne Barnes; 11/10/2015

Pendimethalin: Pendimethalin Residues of Concern in Ruminant Commodities; DP# 

Barcode: D428264; P. Yvonne Barnes; 08/06/2015

Drinking Water Assessment

Drinking Water Assessment for Proposed New Uses of Pendimethalin on Caneberry

Subgroup 13-07 A, Bush berry Subgroup 13-07B, Crop Group Conversion for Tree Nut

Group 14-12; and Cool- and Warm Season Forage Grasses; DP# Barcode: D421275, 420012,

I. Abdel-Saheb; 01/08/2015

Dietary Exposure Assessment

Pendimethalin: Acute and Chronic Aggregate Dietary (Food and Drinking Water) Exposure 

and Risk Assessments in support of the Human Health Risk Assessment for New uses on 

Caneberry subgroup 13-07A, Bushberry subgroup 13-07B and Livestock commodities. Crop 

group conversion for Tree Nut group 14. Amend the pre-harvest interval and tolerances for 

Pendimethalin in/on Grass Forage, Fodder, and Hay (Crop Group 17); DP Barcode D428267; 

P. Yvonne Barnes; 11/3/2015.

Occupational/Residential Assessment 

Pendimethalin: Occupational and Residential Exposure Assessment for a Proposed Section 3

Crop Expansions and Conversions of the Following: Bushberry Subgroup 13-07B, Caneberry 

Subgroup 13-07A, and Nut Tree Subgroup 14-12; DP# Barcode: D420014, B. Bobowiec; 

03/03/2015

Pendimethalin: Occupational and Residential Exposure/Risk Assessment for Registration 

Review and for new Proposed Use on Leaf lettuce; Leafy brassica greens; Melons; Edamame; 

Kiwi and other small fruit vines; S. Shelat; 06/07/12; D402406

Secondary Review of Occupational and Residential Exposure/Risk Assessment for 

Registration Review and for new Proposed Use on Leaf lettuce; Leafy PROWL® 3.3 EC 

Herbicide.” MRID 44969901-02; DP Barcode D262264; C. Jarvis; 08/01/2001

Pendimethalin: Occupational and Residential Exposure Assessment for Proposed Section 3 

Registration for Use on Grasses Grown for Seed and Dormant Bermudagrass Pasture and Hay 

Fields; DP Barcode 371025; S. Shelat; 10/27/2009
Pendimethalin Human Health Risk Assessment DP No. D428265

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Appendix A. Toxicology Profile and Executive Summaries

A.1 Toxicology Data Requirements

The requirements (40 CFR 158.340) for pendimethalin are in Table A.1. Use of the new 

guideline numbers does not imply that the new (1998) guideline protocols were used.

TABLE A.1 Toxicology Data Requirements for Pendimethalin.

Test Technical

Required Conducted

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 (non-rodent)

870.3200 21/28-Day Dermal

870.3250 90-Day Dermal

870.3465 90-Day Inhalation

yes

yes

yes

no

no

yes

yes

yes

no

no

870.3700a Developmental Toxicity (rodent)

870.3700b Developmental Toxicity (non-rodent)

870.3800 Reproduction

yes

yes

yes

yes

yes

yes

870.4100a Chronic Toxicity (rodent)

870.4100b Chronic Toxicity (non-rodent)

870.4200a Oncogenicity (rat)

870.4200b Oncogenicity (mouse)

870.4300 Chronic/Oncogenicity

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

870.5100 Mutagenicity—Gene Mutation (bacterial)

870.5300 Mutagenicity—Gene Mutation (mammalian)

870.5375 Mutagenicity—Structural Chromosomal Aberrations

870.5395 Mutagenicity—Other Genotoxic Effects 

870.5500 Mutagenicity—Other Genotoxic Effects

yes

yes

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 Developmental Neurotoxicity

no

no

yes

yes

no

no

no

yes

yes

no

870.7485 General Metabolism

870.7600 Dermal Penetration 

870.7800 Immunotoxicity

yes

no

yes

yes

yes

yes
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A.2 Toxicity Profiles

Table A.2.1 Acute Toxicity Profile- Pendimethalin

Guideline No. Study Type MRID(s) Results Toxicity 

Category

870.1100 Acute oral [Rat] 00026657 LD50=1250 mg/kg (m)

=1050 mg/kg (f)

III

870.1200 Acute dermal [Rabbit] 00026657 LD50= >1250 mg/kg IV

870.1300 Acute inhalation [Rat] 00073342 LC50= 32 mg/L IV

870.2400 Acute eye irritation [Rabbit] 00026657 Slight conjunctival 

irritation

III

870.2500 Acute dermal irritation [Rabbit] 00026657 No dermal irritation IV

870.2600 Skin sensitization [Guinea pig] 00153767 Non- sensitizer -

TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Pendimethalin.

Guideline 

Number Study Type MRID Number & Classification Dose Levels Results

870.3100 Subchronic oral 

[Rat] (30-day)

000106754 

Supplementary

0, 800, 1600, 3200 ppm 

0, 80, 160, 320 mg/kg/day

NOAEL = 160 mg/kg/day.

LOAEL = 320 mg/kg/day, based on 

increased liver weight.

870.3100 Subchronic oral 

[Rat] (13-week) 00156081

0, 100, 500, 5000 ppm

0, 10, 50, 500 mg/kg/day

NOAEL = 50 mg/kg/day.

LOAEL = 500 mg/kg/day, based on 

decreased body weight gain and 

food consumption, decreased 

hematocrit and hemoglobin with 

increases in platelets in males, 

increased liver weight, red thyroids, 

and hypertrophy of the liver.

870.3100 Subchronic oral 

[Rat] (13-week)

00059468

Supplementary

0, 25, 50, 100, 500, 2500 

ppm

0, 2.5, 5, 10, 50, 250 

mg/kg/day

NOAEL = 250 mg/kg/day.

LOAEL was not determined.

870.3100 Subchronic oral 

[Rat] (13 week)

00059469

Supplementary

0, 2500 ppm

0, 250 mg/kg/day

NOAEL = 250 mg/kg/day.

LOAEL was not determined.

870.3100 Subchronic oral 

[Rat] (92-day) 42054601

0, 100, 5000 ppm

0, 4.98, 245.4 mg/kg/day

NOAEL = 4.98 mg/kg/day.

LOAEL = 245.4 mg/kg/day, based 

on thyroid effects.

870.3100 Subchronic oral 

[Rat] (56-day) 43135001

0, 500, 5000 ppm

0, 31, 292 mg/kg/day

NOAEL was not determined.

LOAEL = 31 mg/kg/day, based on 

thyroid effects.

870.3100 Subchronic oral 

[Rat] (14-day) 43135003 0, 100, 500 ppm NOAEL = 10 mg/kg/day.
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TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Pendimethalin.

Guideline 

Number Study Type MRID Number & Classification Dose Levels Results

0, 10, 500 mg/kg/day LOAEL = 500 mg/kg/day, based on 

thyroid effects.

870.3100 Subchronic oral 

[Dog] (90-day)

00026672

Supplementary

0, 62.5, 250, 1000 

mg/kg/day

NOAEL = 62.5 mg/kg/day.

LOAEL = 250 mg/kg/day, based on 

body weight loss.

870.3150

Subchronic oral 

[Mouse] (30-

day)

000106754

Supplementary

0, 500, 1000, 2000 ppm

0, 75, 150, 300 mg/kg/day

NOAEL = 300 mg/kg/day.

LOAEL was not determined.

870.3200 21-Day dermal 

toxicity [Rat] 00026663

0, 250, 500, 1000 

mg/kg/day

NOAEL = 1000 mg/kg/day.

LOAEL was not determined.

870.3700a

Prenatal 

developmental 

toxicity [Rat]

00025752

Supplementary, 

but satisfactory 

when considered 

with the rabbit 

developmental.

0, 125, 250, 500 

mg/kg/day

Maternal NOAEL = 500 

mg/kg/day (highest dose tested).

Developmental NOAEL = 500 

mg/kg/day (highest dose tested).

870.3700b

Prenatal 

developmental 

toxicity 

[Rabbit)]

00117444

Supplementary, 

upgradeable.

0, 15, 30, 60 mg/kg/day

Maternal NOAEL = 60 mg/kg/day 

(highest dose tested).

Developmental NOAEL = 60 

mg/kg/day (highest dose tested).

Note: a range finding study 

indicated doses ≥125 mg/kg/day 

associated with increased mortality.

870.3800

Reproduction 

and fertility 

effects [Rat]

(2-generation 

reproduction)

41725203

Acceptable

0, 500, 2500, 5000 ppm

0, 34/43, 172/216, 

346/436 mg/kg/day (M/F)

HED RED

0, 25, 125, 250 mg/kg/day

HIARC Document

Note: Doses were 

obtained from an HED 

pendimethalin RED, and 

a HIARC document 

(4/18/2000) which 

resulted in different dose 

calculations for 

mg/kg/day. 

Consequently, doses are 

given as a range, based on 

calculations from actual 

chemical intake, and a 

Parental/Systemic 

NOAEL = 25-34/43 (M/F) 

mg/kg/day (500 ppm).

LOAEL = 125-172/216 (M/F) 

mg/kg/day (2500 ppm), based on 

decreased body weight gain and 

food consumption.

Reproductive/Offspring 

NOAEL = 25-34/43 (M/F) 

mg/kg/day (500 ppm).

Reproductive/Offspring 

LOAEL = 125-172/216 (M/F) 

mg/kg/day (2500 ppm), based on 

decreases in the number of pups 

born, and pup weights.
Pendimethalin Human Health Risk Assessment DP No. D428265

Page 36 of 42

TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Pendimethalin.

Guideline 

Number Study Type MRID Number & Classification Dose Levels Results

generic ratio (1:20) of 

dietary intake.

870.3800

Reproduction 

and fertility 

effects [Rat]

(3-generation 

reproduction)

00026671, 

0040304, 

00059470

Acceptable

0, 500, 5000 ppm

0, 25, 250 mg/kg/day

Parental/Systemic 

NOAEL = 25 mg/kg/day.

LOAEL = 250 mg/kg/day, based on 

decreased body weight.

Reproductive/Offspring 

NOAEL = 25 mg/kg/day.

Reproductive/Offspring 

LOAEL = 250 mg/kg/day, based on 

decreased pup body weight gain, 

and possible decreased pups born 

alive and pup survival.

870.4100b

Chronic 

toxicity [Dog] 

(2-year oral)

00058657

0, 12.5, 50, 200 

mg/kg/day

NOAEL = 200 mg/kg/day.

LOAEL was not established. 

870.4200

Chronic 

toxicity/ 

carcinogenicity 

[Rat]

(2-year oral)

40174401

Acceptable

0, 100, 500, 5000 ppm

0, 5, 25, 250 mg/kg/day

NOAEL = 25 mg/kg/day.

LOAEL = 250 mg/kg/day, based on 

decreased survival and body weight 

gain, decreased food consumption, 

increased gamma glutamyl 

transferase, cholesterol and liver 

weights, and thyroid effects.

870.4200

Chronic 

toxicity [Rat] 

(2-year oral)

42027802

Acceptable

0, 1250, 2500, 3750, 5000 

ppm

0, 51, 103, 154, 213 

mg/kg/day

NOAEL was not determined.

LOAEL = 51 mg/kg/day, based on 

non-neoplastic thyroid follicular 

cell changes.

870.4300 Carcinogenicity 

[Mouse] (18-

month oral)

40909901

Acceptable

0, 100, 500, 5000 ppm

0, 12.3/15.6, 62.3/78.3, 

622.1/806.9 mg/kg/day 

(M/F)

NOAEL = 62.3/78.3 mg/kg/day. 

LOAEL = 622./806.9 mg/kg/day, 

based on mortality, body weight 

decrease, organ weight changes, 

and amyloidosis.

870.5100

Reverse gene 

mutation assay 

[Bacterial 

strains of S. 

typhimurium]

00153768

50, 158, 500, 1581, 5000 

μg/plate

Positive 

Evidence of a 2-fold increase in the 

number of induced mutant colonies 

over background (at all doses from 

50 to 5000 μg/plate).

870.5100

Reverse gene 

mutation assay 

[Escherichia 

coli WP2]

43177801

25, 50, 100, 250, 500, 750 

μg/plate Negative
Pendimethalin Human Health Risk Assessment DP No. D428265

Page 37 of 42

TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Pendimethalin.

Guideline 

Number Study Type MRID Number & Classification Dose Levels Results

870.5100

Reverse gene 

mutation assay 

[Escherichia 

coli WP2]

43135005

50, 158, 500, 1581, 5000 

μg/plate or 1000 μg/paper 

disk/plate 

Negative

870.5100

Reverse gene 

mutation assay 

[Escherichia 

coli WP2]

43135006

50, 100, 250, 500, 750 

μg/plate Negative

870.5300

Mammalian 

cell gene 

mutation 

[Chinese 

hamster ovary]

43177802

1, 5, 7.5, 10, 20, 30, 40, 

50 μg/plate (-S9)

10, 25, 50, 75, 100, 125, 

150, 175 μg/plate (+S9)

Negative

870.5375

Chromosomal 

aberration 

[Chinese 

hamster ovary]

00153770

Doses ranging from 5-50 

μg/ml Negative

870.5395

Micronucleus 

study [Mouse] 42027801 313, 625, 1250 mg/kg Negative

870.5550

Alkaline elution 

assay [Rat] 43135007 1250, 2500, 5000 mg/kg Negative

870.6200

Acute 

neurotoxicity

48695601

Acceptable

0, 100, 300, or 1000 

mg/kg

NOAEL=100 mg/kg,

LOAEL= 300 mg/kg, based on 

reduced motor activity for males 

and females (↓19 and ↓51%, 

respectively, on Day 0.

870.6200

Subchronic 

neurotoxicity 

42054601

Acceptable

0, 42.0/50.1, 126.5 / 

151.9, 386.8/423.1 mg/kg 

bw/day [M/F]

NOAEL= 386.8/423.1 mg/kg/day 

(HDT).

LOAEL not established.

870.7800 Immunotoxicity

48608901

Acceptable

0, 38, 72, 276 mg/kg/day NOAEL=276 mg/kg/day (HDT)

LOAEL not established.

870.7485

Metabolism and 

pharmacokineti

cs [Rat]

00046275

Acceptable

NA*

Pendimethalin is eliminated from 

the body within 24 hours, with 70% 

being excreted in feces (primarily 

the parent compound), and 20% in 

urine.

Nonguideline

Developmental 

Thyroid Study

48695603

Acceptable

0, 31, 62 or 186 

mg/kg/day (GD 6 - PND 

21)

Developmental thyroid function,

The thyroid function in fetuses or 

post-partum day (PND 4) was not 

affected by the treatment of 

pendimethalin. 
Pendimethalin Human Health Risk Assessment DP No. D428265

Page 38 of 42

TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Pendimethalin.

Guideline 

Number Study Type MRID Number & Classification Dose Levels Results

Parental thyroid function,

Decreased thyroxine (T4) levels 

were observed in pregnant dams 

and PND 21 male and female pups 

at 31 mg/kg/day (LOAEL).

* NA = Not Applicable. 

Note: Some of the LOAELs/NOAELS were previously denoted as LOELs/NOELS in Data Evaluation Records (DERs). The language was 

updated to comply with current standards without re-examining effects. 
Pendimethalin Human Health Risk Assessment DP No. D428265

Page 39 of 42

Appendix B. International Residue Limits Table 

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex

40 CFR 180.361: Pendimethalin

Plant: N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine 

and its metabolite, 4-[(1-ethylpropyl)amino]-2-methyl-3,5-

dinitrobenzyl alcohol

Livestock: N-(1-ethylpropyl)-3,4-dimethyl-2,6-

dinitrobenzenamine and its metabolite, metabolite 6 “goat 

metabolite 6” (1-(1-ethylpropyl)-5, 6-dimethyl-7-nitro-1Hbenzimidazole)

benzenamine, N-

(1-ethylpropyl)-

3,4-dimethyl-2,6-

dinitro-, including 

the metabolite 

benzenemethanol, 

4-[(1-

ethylpropyl)amino]

-2-methyl-3,5-

dinitroNone

Commodity1 Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico2 Codex

Fruit, caneberry, subgroup13-07A 0.10

Fruit, bushberry, subgroup13-07B 0.10

Nut, Tree group 14-12 0.10

Grass forage, fodder, and hay crop group 17, forage 1000.0

Grass forage, fodder, and hay crop group 17, hay 2000.0

Milk 0.10

Meat 0.10

Fat 0.3

Kidney 3.0

Liver 1.5

Meat byproducts except liver 3.0

Completed by: M. Negussie; 07/28/2015 
Pendimethalin Human Health Risk Assessment DP No. D428265

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Appendix C. Occupational Handler Non-Cancer Exposure and Risk Estimates for Pendimethalin

Appendix D. Occupational Handler Dermal and Inhalation Non-Cancer Exposure and Risk Estimates for Prowl ® H2O Pendimethalin on Proposed Crop Group 

Bushberries, Caneberries and Tree Nuts. 

Application 

Equipment

Crop / 

Target 

Category

App.

Rate2

Amount 

Handled / 

Area 

Treated3

Dermal Unit 

Exposures 

(ug/lb ai)1

Inhalation 

Unit 

Exposures 

(ug/lb ai)1

Dermal Dose 

(mg/kg/day)4

Dermal MOE5

(LOC = 30)

Inhalation 

Dose 

(mg/kgday)6

Inhalation 

MOE7

(LOC = 

30)

Total MOE8

Value

Units

Value

Units

SL/No 

G

SL/G No-R

SL/No 

G

SL/G SL/No 

G

SL/G No-R No-R

SL/No 

G and 

No-R

SL/G 

and 

No-R

Mixer/Loader

Chemigation Bushberries, 

Caneberries 

and Tree 

Nuts

6 

lb 

ai/acre

350 acres

220 220 0.219

0.17 0.03 58 340 0.006 1,700 56 280

Groundboom

80 acres 0.04 0.007 250 1,500 0.0013 7,600 240 1,300

40 acres 0.0198 0.00338 510 3,000 0.000658 15,000 490 2,500

Applicator

Groundboom

Bushberries, 

Caneberries 

and Tree 

Nuts

6 

lb 

ai/acre

80 acres

78.6 16.1 0.34

0.014 0.003 710 3,400 0.002 4,900 620 2,000

40 acres 0.00709 0.00145 1,400 6900 0.00102 9,800 1,200 4,000

Mixer/Loader/Applicator

MechanicallyPressurized 

Handgun 

Ground soildirected Bushberries, 

Caneberries 

and Tree 

Nuts

0.3 lb 

ai/gallo

n

1,000 

gallon 1,300 390 3.9 0.146 0.0439 68 230 0.0146 680 62 170

ManuallyPressurized 

Handwand 40 

gallons

100,000 430 30 0.45 0.00194 22 5200 0.0045 2,200 22 1,500

Backpack

Ground soildirected8,260 2.58 0.0372 270 0.000388 26,000 270

1 Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (March 2014); Level of mitigation: SL/No G (single layer dermal), SL/G (single dermal layer with gloves), No-R (baseline inhalation no 

respirator). 

2 Based on proposed label (Prowl ® H2O Reg. No.241-418).

3 Exposure Science Advisory Council Policy #9.1.

4 Dermal Dose = Dermal Unit Exposure (μg/lb ai) × Conversion Factor (0.001 mg/μg) × Application Rate (lb ai/acre or gal) × Area Treated or Amount Handled (A or gal/day) × DAF (3%) ÷ 80 (kg).

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

6 Inhalation Dose = Inhalation Unit Exposure (μg/lb ai) × Conversion Factor (0.001 mg/μg) × Application Rate (lb ai/acre or gal) × Area Treated or Amount Handled (A or gal/day) ÷ 80 (kg).
Pendimethalin Human Health Risk Assessment DP No. D428265

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

8 Total MOE = NOAEL (10 mg/kg/day) ÷ Dermal Dose + Inhalation Dose.
Pendimethalin Human Health Risk Assessment DP No. 416285

Page 42 of 42

Appendix D. 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 

PHED 1.1; the AHETF database; the Outdoor Residential Exposure Task Force (ORETF) 

database; the ARTF 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 

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

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