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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

DATE: 02-18-2015

SUBJECT: Chlorfenapyr. Addendum to Registration Review Preliminary Risk Assessment 

to Update Occupational Post-application Assessment based on Submitted 

Dislodgeable Foliar Residue (DFR) Data

PC Code: 129093 DP Barcode: D425697

Decision No.: 496921 Registration No.: NA

Petition No.: NA Regulatory Action: Reg Review

Risk Assessment Type: Occupational/Residential Exposure Assessment Case No.: 7419

TXR No.: NA CAS No.: 122453-73-0

MRID No.: NA 40 CFR: §180.513

FROM: Kelly M. Lowe, Environmental Scientist

Health Effects Division (HED)/Risk Assessment Branch (RAB) 1 (7509P)

THRU: Charles Smith III, Branch Chief

HED/RAB 1 (7509P)

TO: Margaret Hathaway

Kevin Costello, Branch Chief

Pesticide Re-evaluation Division (PRD; 7508P)

INTRODUCTION

In 2014, HED conducted a preliminary risk assessment (PRA) of registered uses for chlorfenapyr 

as part of Registration Review1. In this assessment, DFR data were required in accordance with 

40 CFR Part 158, since the calculated occupational dermal post-application margins of exposure 

(MOEs) were less than two times the level of concern (LOC; i.e., < 200) based on default values 

for the fraction of application rate available for transfer after a foliar application. 

In response to this data requirement, the Registrant, BASF, submitted a study, “Determination of 

dislodgeable foliar residues in azaleas and chrysanthemums treated with Alert 2SC.” This study 

 

1 Perron, M et al., 2014. Chlorfenapyr – Preliminary Human Health Risk Assessment for Registration Review. 

D416560. 
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was reviewed by HED and found to be acceptable for use in risk assessment2. The occupational 

post-application assessment for chlorfenapyr has been updated in this addendum using the 

submitted chemical-specific data and a summary is provided below. These risk estimates 

supersede those provided in the PRA (Memo, M. Perron et al, 22-May-2014, D416560, Table 

9.2.2.1) and the supporting occupational and residential exposure assessment (Memo, L. 

Venkateshwara, 18-Jun-14, D417598, Table 6.2.2.2). 

Summary of DFR study

Determination of Dislodgeable Foliar Residues in Azaleas and Chrysanthemums Treated with 

ALERT® 2SC (MRID 49503201; HED Review: Memo, K. Lowe, xx-xxx-2015, D423652).

This study was designed to determine the dissipation of DFRs of the active ingredient (ai) 

chlorfenapyr from treated azalea and chrysanthemum foliage. The test product, ALERT® 2SC 

(CL 303630 2SC), was a 21.4% ai chlorfenapyr soluble concentrate formulation. The field phase 

of the study was conducted in greenhouses located at Plant Sciences Inc., in Watsonville, 

California (NAFTA Region 10) during September of 1998. Three foliar broadcast applications 

were made to potted azalea and chrysanthemum plants at a target rate of 0.64 lb ai/A, using a 

retreatment interval (RTI) of 5 days. Actual rates ranged from 0.63 to 0.64 lbs ai/A. The foliar 

broadcast spray applications were made using a backpack sprayer with a handheld boom.

Chlorfenapyr DFRs from azalea foliage averaged 0.516 μg/cm2immediately after the first 

application, 0.833 μg/cm2immediately after the second application, and 0.842 μg/cm2

immediately after the third application. Average residues reached a maximum of 1.00 μg/cm2 at 

12 hours after the 3rd application, and declined only slightly to 0.751 μg/cm2 by 14 days after the 

3

rd application. 

Chlorfenapyr dislodgeable foliar residues from chrysanthemum foliage averaged 0.101 μg/cm2

immediately after the first application, 0.159 μg/cm2immediately after the second application, 

and 0.0908 μg/cm2immediately after the third application. Average residues remained relatively 

steady through the last sampling interval. The maximum average residue of 0.164 μg/cm2

occurred at 7 days after the 3rd application.

Chlorfenapyr residues dislodged from the azalea and chrysanthemum foliage remained relatively 

stable over the 14-day sampling period after the last application. Therefore, a regression analysis 

was not performed. 

No major issues were identified during review of this study and the results are considered 

acceptable for risk assessment purposes. Since residues remained relatively stable throughout 

the sampling period, HED would recommend that the highest residue value identified during the 

study period be used in the occupational post-application assessment for chlorfenapyr. 

 

2 Lowe, Kelly. 2015. Chlorfenapyr: Review of “Determination of Dislodgeable Foliar Residues in Azaleas and 

Chrysanthemums Treated with ALERT® 2SC.” D423652. 
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Summary of DFR Values for Treated Chrysanthemums and Azaleas in a Greenhouse with 

Chlorfenapyr; MRID# 49503201.

Greenhouse 

Chrysanthemums

Greenhouse 

Azaleas

Study Target Rate (lb ai/A) 0.64

Spray Volume (GPA) 198 - 201

Measured Average Day 0 Residue (μg/cm2)

[measured “as soon as sprays dried”]

1

st application: 0.101

2

nd application: 0.159

3

rd application: 0.0908

1

st application: 0.516

2

nd application: 0.833

3

rd application: 0.842

Highest Measured Value (μg/cm2) 0.164

(7 days after 3rd application)

1.00 

(12 hours after 3rd application)

Proposed use of DFR data:

 Use the azalea DFR data to estimate post-application exposure for greenhouse 

ornamentals/non-bearing plants and greenhouse vegetables using the highest measured 

value.

 Use the chrysanthemum DFR data to estimate post-application exposure for floriculture 

crops (cut flowers) using the highest measured value. 

Crop DFR Data Site Proposed use of 

DFR Data Characterization

Greenhouse 

Ornamental, Nonbearing Plants

Greenhouse vegetables

Azaleas Greenhouse Highest measured 

value

 DFR data collected in greenhouse.

 Study crop matches ornamental 

plant crop group.

 Highest residues dislodged from 

azalea foliage; considered 

protective for greenhouse 

vegetables.

Floriculture Crop (cut 

flowers) Chrysanthemum Greenhouse Highest measured value

 DFR data collected in greenhouse.

 Study crop matches cut flower 

crop group.

Updated Occupational Post-application Assessment:

The updated short- and intermediate-term occupational post-application exposure scenarios 

associated with the registered uses of chlorfenapyr are summarized in the table below. All 

scenarios resulted in MOEs greater than the LOC of 100 (ranging from 880 to 28,000) on day 0 

(12 hours after application); and, therefore, are not of concern to HED.

Occupational Post-application Non-Cancer Exposure and Risk Estimates for Chlorfenapyr.

Crop/Site Activities Transfer Coefficient 

(cm2/hr) DFR1 Dermal Dose(mg/kg/day)2 MOE3

Short and Intermediate-Term

Floriculture Crop

(cut flowers)

Container Moving, Pinching, 

Hand Pruning, Hand Weeding, 

Scouting, Transplanting,

230

0.05

0.00018 28,000

Irrigation (hand set) 1,900 0.0015 3,400
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Occupational Post-application Non-Cancer Exposure and Risk Estimates for Chlorfenapyr.

Crop/Site Activities Transfer Coefficient 

(cm2/hr) DFR1 Dermal Dose(mg/kg/day)2 MOE3

Short and Intermediate-Term

Hand Harvesting 4,800 0.0037 1,300

Greenhouse 

Vegetables

Transplanting, Irrigation (hand 

watering) 230

0.31

0.001 4,600

Hand harvesting, Pinching, 

Pollination, Hand Pruning, 

Scouting, Turing, Tying/training, 

Hand Weeding, Propagating, 

Hand Pruning, Scouting

1200 0.006 880

Greenhouse 

Ornamental, Nonbearing Plant

Hand harvesting, Hand Pruning, 

Scouting, Container Moving, 

Hand Weeding, Transplanting, 

Pinching, Tying/Training, 

Grafting, Propagating

230 0.001 4,600

1. DFR = chemical-specific data from MRID 49503201. 

a. For floriculture crops, DFR data for chrysanthemums was used. Highest measured value = 0.164 ug/cm2 adjusted for difference 

in application rates between the study (0.64 lb ai/A) and the registered labels (0.2 lb ai/A).

b. For greenhouse vegetables and ornamental/non-bearing plants, DFR data for azaleas was used. Highest measured value = 1.00 

ug/cm2 adjusted for difference in application rates between the study (0.64 lb aiA) and the registered labels (0.2 lb ai/A).

2. Daily Dermal Dose = [DFR (μg/cm2) × Transfer Coefficient × 0.001 mg/μg × 8 hrs/day × dermal absorption (13 %)]  BW (69 kg).

3. MOE = POD (5 mg/kg/day) / Daily Dermal Dose.