Forchlorfenuron Human Health Risk Assessment DP No. D407226 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

Date: February 6, 2014 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: Forchlorfenuron. Human Health Risk Assessment for Proposed Uses on 

Almond, Sweet Cherry, Fig, Pear, Pistachio and Plum/Prune. 

PC Code: 128819 

Decision No.: 470643 

Petition No.: NA 

Risk Assessment Type: Single Chemical 

TXRNo.: NA 

MRID No.: NA 

FROM: Alexandra LaMay, Biologist 

Donna Davis, Chemist 

DP Barcode: 0407226 

Registration No.: 71049-4 

Regulatory Action: Section 3 

Case No.: NA 

CAS No.: 68157-60-8 

40 CFR: 180.569 

Matt Lloyd, Industrial Hygieni t .., 

Linda Taylor, Toxicologist ~~ lb-~~..,. Risk Assessment Branch l 

Health Effects Division (7509P) 

THROUGH: Danette Drew, ChemiM-'~­

Michael Metzger, Chief 

Risk Assessment Branch VI 

Health Effects Division (7509P) 

TO: Marcel Howard 

Cynthia Giles-Parker, Chief 

Fungicide Branch 

Registration Division (7505P) 

Page 1 of32 
Forchlorfenuron Human Health Risk Assessment DP No. 0 407226 

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

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

2.1 Data Deficiencies ................................. ............................ ............ .... ............ .... ............... 6 

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

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

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

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

2.2.4 International Harmonization ................................................................. .................... 8 

2.3 Label Recommendations ......................................................................................... ....... 8 

2.3.1 Recommendations from Residue Reviews ................................................................ 8 

2.3.2 Recommendations from Occupational Assessment ......... ........ .... .... .... ............. ....... 8 

2.3.3 Recommendations from Residential Assessment. ............................... ............. .... .... 8 

3.0 Introduction ......... ............................ ........ ................... ........ ........ .... ................ ........ .... ........ 8 

3.1 Chemical Identity ............................ .................................................. ......................... .... 8 

3.2 PhysicaVChemical Characteristics ............................................................................... 8 

3.3 Pesticide Use Pattern ...................................................................................................... 9 

3.4 Anticipated Exposure Pathways ................................................................................. 1 0 

3.5 Consideration of Environmental Justice .................................................................... 10 

4.0 Hazard Characterization and Dose-Response Assessment .... ...................................... 11 

4.1 Summary of Toxicological Effects ............................................... ..... .......................... 11 

4.2 Safety Factor for Infants and Children (FQPA Safety Factor) ................ ........ ....... 12 

4.2.1 Completeness of the Toxicology Database ........ .................... ........ ................ .......... 12 

4.2.2 Evidence of Neurotoxicity ....... ....................................................................... .... ...... 12 

4.2.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal.. ... ... 12 

4.2.4 Residual Uncertainty in the Exposure Database ................................................... 13 

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

5.0 Dietary Exposure and Risk Assessment.. ................................................. ........ .... .... ...... 14 

5.1 Residues of Concern Summary and Rationale ........ .................................................. 14 

5.2 Food Residue Profile ..... .............. .... .... ................... ............ .... ....... .................... .... ....... 15 

5.3 Water Residue Profile ............. ................... ............... ........................................ ........ ... 15 

5.4 Dietary Risk Assessment ........................................................................... .... ............. .. 16 

5.4.1 Description of Residue Data Used in Dietary Assessment.. .................................. 16 

5.4.2 Percent Crop Treated Used in Dietary Assessment .............................................. 16 

5.4.3 Acute Dietary Risk Assessment ............................................................................... 16 

5.4.4 Chronic Dietary Risk Assessment ........................................................................... 17 

5.4.5 Cancer Dietary Risk Assessment.. ................................ .... ....................................... 1 7 

5.4.6 Summary Table .. ........... ... .... .... .............................................................. .... .... ..... ...... 17 

6.0 Residential (Non-Occupational) Exposure/Risk Characterization ............. ................ 18 

6.1 Residential Handler Exposure .. .......................................................... .... ................. ... 18 

6.2 Post-Application Exposure ............... .... ............... ........ ........ .... .... .... ............................ 18 

6.3 Residential Bystander Post-application Inhalation Exposure ..... ............................ 18 

6.4 Spray Drift ......... ........................ .... .... ........... .... .... ........................................................ 18 

7.0 Aggregate Exposure/Risk Characterization .................................................................. 19 

7.1 Acute Aggregate Risk ................................................................................................... 19 

7.2 Short-Term Aggregate Risk .......... ...................................................... ........ ................ 19 

7.3 Intermediate-Term Aggregate Risk .... .... ................................................................... 19 

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Forchlorfenuron Human Health Risk Assessment DP No. D407226

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7.4 Chronic Aggregate Risk .............................................................................................. 19

7.5 Cancer Aggregate Risk ................................................................................................ 19

8.0 Cumulative Exposure/Risk Characterization ............................................................... 19

9.0 Occupational Exposure/Risk Characterization ............................................................ 20

9.1 Short-/Intermediate-Term Handler Risk................................................................... 20

9.2 Short-/Intermediate-Term Post-Application Risk .................................................... 23

9.2.1 Dermal Postapplication Risk ................................................................................... 23

9.2.2 Inhalation Postapplication Risk .............................................................................. 24

10.0 References......................................................................................................................... 24

Appendix A. Toxicology Profile and Executive Summaries .................................................. 26

A.1 Toxicology Data Requirements................................................................................... 26

A.2 Toxicity Profiles............................................................................................................ 27

Appendix B. Physical/Chemical Properties............................................................................. 31

Appendix C. Review of Human Research................................................................................ 32
Forchlorfenuron Human Health Risk Assessment DP No. D407226

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1.0 Executive Summary

HED has conducted a human health risk assessment to support requested Section 3 uses for the 

active ingredient, forchlorfenuron, a plant growth regulator used to increase fruit set and size. 

The requested action is for a Section 3 Registration and the establishment of a permanent 

tolerance for residues of forchlorfenuron in/on almonds, sweet cherries, figs, pears, pistachios 

and plums/prunes. The use would permit a single application of forchlorfenuron tied to a 

specific growth stage at a rate of 0.022 lb ai/A.

The toxicological database for forchlorfenuron is considered complete for characterization of 

potential developmental, reproductive, carcinogenetic, mutagenic, neurotoxic, and immunotoxic 

effects. Forchlorfenuron is rapidly absorbed following oral exposure, with the majority of the 

dose being recovered in the urine within 24 hours. Forchlorfenuron is not acutely toxic via the 

oral, dermal, and inhalation routes. It produces mild eye irritation, is not a dermal irritant, and is 

negative for dermal sensitization. Dose-related effects noted in the dog following subchronic 

and chronic exposure were generally limited to decreased body weight and body-weight gain. In 

the rat, the only organ that appeared to be affected was the kidney, which showed suppurative 

inflammation, suppurative pyelonephritis, non-suppurative interstitial nephritis, and cortical 

cysts following chronic exposure. The prenatal developmental studies in rabbits and rats and the 

two-generation reproduction study in rats showed no indication of increased susceptibility to in 

utero and/or postnatal exposure to forchlorfenuron. Developmental toxicity occurred in the rat 

only at a maternally toxic dose level and was not observed in the rabbit. Reproductive toxicity 

was not observed. There is no concern for immunotoxicity or neurotoxicity following exposure 

to forchlorfenuron. Forchlorfenuron has been classified as not likely to be a human carcinogen, 

and there is no concern for mutagenicity. 

Based on the toxicity, duration of exposure, and uses of forchlorfenuron, the following toxicity 

endpoints were selected: 

Acute dietary (all populations): No appropriate toxicity endpoint attributable to a 

single dose (exposure) could be identified from the available toxicology data base.

Chronic dietary: cRfD: 0.07 derived from a NOAEL of 7 mg/kg/day in a chronic oral 

toxicity study in the rat. LOAEL = 93 mg/kg/day based on decreased body weight 

parameters and kidney toxicity.

Dermal and inhalation exposures (short-term): NOAEL = 100 mg/kg/day from data of 

the main and range-finding developmental toxicity studies in the rabbit. LOAEL = 125 

mg/kg/day based on body weight loss.

Dermal and inhalation exposures (intermediate-term): NOAEL = 87 mg/kg/day from 

a chronic oral toxicity in the dog. LOAEL = 195 mg/kg/day based on decreased body 

weight /body weight gain/food consumption.

For dermal exposure and risk assessments, 100% absorption was assumed; inhalation toxicity 

was assumed to be equivalent to oral toxicity. For the occupational and residential risk 

assessments the level of concern (LOC) is for MOEs less than 100. The FQPA safety factor has 

been reduced to 1X since the database is complete, there is no evidence of pre- or post-natal 

sensitivity/susceptibility, there is no evidence of neurotoxicity, and exposure estimates are not 

likely to underestimate risk.
Forchlorfenuron Human Health Risk Assessment DP No. D407226

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The nature of the residue in plants is adequately understood and the residue of concern in plants 

is forchlorfenuron only for both risk assessment and tolerance setting. The nature of the residue 

in livestock is not adequately understood, but sufficient information is available to evaluate the 

need for tolerances in livestock commodities. Adequate number and geographic distribution of 

field trial data have been provided. Further, adequate information has been provided on the 

potential for residues of forchlorfenuron to concentrate in the processed commodities associated 

with this petition which include dried plum (prune) and dried fig. The only feed item associated 

with this petition is almond hulls. HED has classified the proposed uses as 180.6 (a)(3), no 

reasonable expectation of finite residues with respect to residues in livestock. Tolerances were 

derived using the Organisation for Economic Co-operation and Development (OECD) maximum 

residue level (MRL) calculation procedures. Tolerances established for fresh plum and fig are 

adequate to cover residues likely in dried plum (prune) and dried fig, respectively; therefore 

tolerances are not required for these processed commodities. Specific tolerance 

recommendations are discussed in Section 2.2. There are currently no Codex, Canadian, or 

Mexican MRLs for forchlorfenuron on the crops that are the subject of this petition; therefore, 

there are no issues with respect to international harmonization associated with this petition. An 

enforcement analytical method is available to enforce the proposed tolerances and is discussed in 

detail in Section 2.2. 

The Environmental Fate and Effects Division (EFED) has developed estimated drinking water 

concentration (EDWC) values for use in human health risk assessment using the PRZM/EXAMS 

and PRZM-GW models for surface and ground water, respectively. For the chronic dietary 

analysis, the maximum annual mean EDWC value of 7.3 μg/L, derived from the PRZM-GW

model, was used as a point estimate to represent chronic drinking water concentration. The 

EDWC of 7.3 μg/L is a post-breakthrough mean that occurs after 88 years of annual use. The 

PRZM/EXAMS (surface water) EDWCs were considerably lower than the PRZM-GW EDWC 

(groundwater). 

An acute dietary endpoint was not selected since there were no effects seen in the toxicological 

database that were attributable to a single dose of forchlorfenuron; therefore, quantification of

acute dietary exposure and risk assessment is not required. A highly conservative chronic 

dietary risk assessment was conducted using tolerance level residues, assuming 100% crop 

treated for all commodities, and using default concentration values or actual processing study 

information when available for processed commodities. For the U.S. general population and for 

all subpopulations, risks were <1% of the cPAD, and are, therefore, not of concern. Since 

forchlorfenuron has been classified as not likely to be carcinogenic, quantification of dietary 

cancer risk assessment is not required. 

Quantification of acute aggregate risk assessment is not required since forchlorfenuron does not 

pose an acute hazard. Since there are no uses of forchlorfenuron existing or proposed that would 

result in residential (non-occupational) exposure to the pesticide, short- and intermediate-term 

aggregate risk assessment are not required. The chronic aggregate risk assessment includes only 

food and drinking water exposure, and is equivalent to the chronic dietary (food and water) risk 

assessment. The chronic dietary risk estimates are not of concern for the general population and 

all population subgroups. Quantification of aggregate cancer risk assessment is not required.
Forchlorfenuron Human Health Risk Assessment DP No. D407226

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For the purposes of this tolerance action EPA has not assumed that forchlorfenuron has a 

common mechanism of toxicity with other substances.

HED conducted occupational handler and post-application exposure and risk assessments for the 

proposed new uses. Short- and intermediate-term MOEs for handlers (mixers/loaders and 

applicators) were not of concern to HED as they significantly exceeded the target MOE of 100. 

Total MOEs for the occupational handler assessment range from 3,300 to 94,000. The 

occupational post-application exposure and risk estimates indicate that short- and intermediateterm MOEs are not of concern to HED also significantly exceeding the targe MOE of 100. 

MOEs for the occupational post-application assessment range from 730 to 10,000.

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.1” 

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

intentionally exposed to a pesticide to determine their exposure. Appendix C provides additional 

information on the review of human research used to complete the risk assessment. There is no 

regulatory barrier to continued reliance on these studies, and all applicable requirements of 

EPA’s Rule for the Protection of Human Subjects of Research (40 CFR Part 26) have been 

satisfied.

2.0 HED Recommendations

HED has no objection to the requested Section 3 registration and permanent tolerances for 

almonds, sweet cherries, figs, pears, pistachios, and prune plums. 

2.1 Data Deficiencies

The toxicity, exposure and residue chemistry data bases are considered complete for the purpose 

of this petition. No additional data are required to support the requested registrations and 

tolerances for almonds, sweet cherries, figs, pears, pistachios, and prune plums. 

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

HPLC/UV method CCRL-MTH-029, Analytical Method for the Determination of 

Forchlorfenuron In/On Grapes, Grape Juice and Raisins, (D344334, D. Davis, 2/13/08) is 

available for enforcing the proposed tolerances for forchlorfenuron on the proposed plant 

commodities. For this method, residues are extracted with methanol or acetone, diluted with 

water, and partitioned against hexane. Residues remaining in the aqueous fraction are then 

partitioned into dichloromethane (DCM) and if necessary further purified using a silica SPE 

cartridge. Residues are determined by HPLC/UV using external standards and residues are 

 

1

http://www.hss.energy.gov/nuclearsafety/env/guidance/justice/eo12898.pdf.
Forchlorfenuron Human Health Risk Assessment DP No. D407226

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confirmed by LC/MS/MS analysis. This method has been adequately validated by the registrant 

and the Agency. The validated limit of quantitation (LOQ) is 0.01 ppm for forchlorfenuron in 

fruit and nut crops, and the reported limits of detection (LOD) are 0.002-0.003 ppm. 

Tolerances are not required for livestock commodities; therefore, an enforcement analytical 

method in livestock commodities is not required.

2.2.2 Recommended Tolerances

Permanent tolerances are currently established for residues of forchlorfenuron under 40CFR 

180.569(a)(1) and temporary tolerances with 12/31/15 expiration are established for residues of 

forchlorfenuron on almond (0.01 ppm), almond hulls (0.15 ppm), sweet cherry (0.01 ppm), fig 

(0.01 ppm), pear (0.01 ppm), pistachio (0.01 ppm), and fresh prune plum (0.01 ppm) under 40 

CFR 180.569(a)(2). 

The tolerance expression listed in the 40 CFR 180.569 complies with the HED interim tolerance 

expression policy (S. Knizner, 5/27/09). Permanent tolerances for forchlorfenuron should be 

established under 180.569(a) for the commodities listed below at the HED-recommended 

tolerance levels shown in Table 2.2.2.

Table 2.2.2. Tolerance Summary for Forchlorfenuron.

Commodity Proposed Tolerance 

(ppm)

HED-Recommended 

Tolerance (ppm)

Comments 

(correct commodity definition)

Almond 0.04 0.01 Almond

Almond, hulls 

(processed commodity)

0.15 0.15 Almond, hulls

Cherry, sweet 0.04 0.01 Cherry, sweet

Fig 0.04 0.01 Fig

Pear 0.04 0.01 Pear

Pistachio 0.04 0.01 Pistachio

Plum, prune 0.04 0.01 Plum, prune, fresh

Note to RD: Concurrently with establishing the tolerances above under 180.569(a)(1), the 

temporary tolerances for the same commodities can be removed from 180.569(a)(2).

2.2.3 Revisions to Petitioned-For Tolerances

The registrant has proposed tolerances for almond, sweet cherry, fig, pear, pistachio, and prune 

plum at 0.04 ppm, stating that the proposed residue level for each commodity was derived using 

the OECD MRL calculation procedures. HED does not concur that these are the appropriate 

outputs from the OECD MRL calculation procedures. All residue values for all crops (not 

including processed commodities) are less than the analytical method limit of quantitation (LOQ) 

of 0.01 ppm. When all inputs for a commodity are less than the LOQ, also known as “censored” 

values, the OECD calculator recommends a tolerance level at the method LOQ. Therefore, to be 

consistent with the OECD MRL calculation procedures, HED is recommending that a tolerance 

of 0.01 ppm be established for almond, sweet cherry, fig, pear, pistachio, and plum.

No change is recommended to the proposed almond hull tolerance.
Forchlorfenuron Human Health Risk Assessment DP No. D407226

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2.2.4 International Harmonization

There are no Codex, Canadian, or Mexican MRLs established for forchlorfenuron; therefore 

there are no international harmonization issues associated with this petition.

2.3 Label Recommendations

No revisions to the proposed labels are required. 

2.3.1 Recommendations from Residue Reviews

The submitted labels are adequate to allow evaluation of the submitted residue data relative to 

the proposed uses. The proposed uses are considered adequately supported by the submitted 

residue chemistry data. No revisions to the proposed labels are required.

2.3.2 Recommendations from Occupational Assessment

None.

2.3.3 Recommendations from Residential Assessment

Not applicable.

3.0 Introduction

3.1 Chemical Identity

Table 3.1 Test Compound Nomenclature

Chemical Structure

Empirical Formula

Common Name Forchlorfenuron

Company experimental name CPPU

IUPAC name 1-(2-chloro-4-pyridyl)-3-phenylurea

CAS Name N-(2-chloro-4-pyridinyl)-N’-phenylurea

CAS Registry Number 68157-60-8

3.2 Physical/Chemical Characteristics

Forchlorfenuron is a lipophilic compound with a low vapor pressure (not volatile) and has low 

water solubility. The physicochemical properties for forchlorfenuron are summarized in Table 

2.3, below. 

N

N

O

Cl N
Forchlorfenuron Human Health Risk Assessment DP No. D407226

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Table 3.2 Physicochemical Properties of Forchlorfenuron. 

Parameter Value Reference

Melting point/range 165-170°C EPA Fact Sheet, 9/2004

pH Not determined due to low water 

solubility

Density 1.44 g/ml at 21 °C

Water solubility 39 ppm 

Solvent solubility 17g/100 mL in acetone

Vapor pressure (25°C) 3.5 x10-5torr

Dissociation constant, pKa Not provided

Octanol/water partition coefficient, 

Log(KOW)

3.2

UV/visible absorption spectrum Not provided

3.3 Pesticide Use Pattern

CPPUTM Plant Growth Regulator is the end use product for which Section 3 registration has been 

proposed. CPPUTM Plant Growth Regulator is a soluble concentrate formulation which contains 

0.25 grams ai per fluid ounce of product and is packaged such that the entire container contains 8 

grams of forchlorfenuron. The proposed use directions for forchlorfenuron on almonds, sweet 

cherries, figs, pears, pistachios, and plums/prunes are summarized in the table below.

Table 3.3. Summary of Proposed Directions for Use of Forchlorfenuron

Application 

Timing, 

Type, and 

Equip.

Formulation

[EPA Reg. 

No.]

Applic. 

Rate 

(lb ai/A)

Max. No. 

Applic. 

per Season

Max. 

Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days)

Use Directions and 

Limitations

Almond

Ground 

application 

CPPUTM 

Plant Growth 

Regulator 

[71049-4]

0.011 –

0.022 1 0.022 NS

Apply during early nut 

development.

Apply in 100 – 200 

gallons spray/acre.

Sweet Cherry

Ground 

application

CPPUTM 

Plant Growth 

Regulator 

[71049-4]

0.011 –

0.022 1 0.022 7

Apply in 100 – 200 

gallons spray/acre.

Fig

Ground 

application

CPPUTM 

Plant Growth 

Regulator 

[71049-4]

0.011 –

0.022 1 0.022 NS

Apply during early fig 

development. Apply in 

100 – 200 gallons 

spray/acre.

Pear

Ground 

application

CPPUTM 

Plant Growth 

Regulator 

[71049-4]

0.011 –

0.022 1 0.022 NS

Apply 25-days postpetal fall. Apply in 100 

– 200 gallons spray/acre.

Pistachio

Ground CPPUTM 0.011 – 1 0.022 NS Apply at beginning of 
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Table 3.3. Summary of Proposed Directions for Use of Forchlorfenuron

Application 

Timing, 

Type, and 

Equip.

Formulation

[EPA Reg. 

No.]

Applic. 

Rate 

(lb ai/A)

Max. No. 

Applic. 

per Season

Max. 

Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days)

Use Directions and 

Limitations

application Plant Growth 

Regulator 

[71049-4]

0.022 kernel formation. Apply 

in 100 – 200 gallons 

spray/acre.

Plum/Prune

Ground 

application

CPPUTM 

Plant Growth 

Regulator 

[71049-4]

0.011 –

0.022 1 0.022 NS

Apply during bloom. 

Apply in 100 – 200 

gallons spray/acre.

3.4 Anticipated Exposure Pathways

The Registration Division has requested an assessment of human health risk to support the 

proposed new use of forchlorfenuron on almonds, sweet cherries, figs, pears, pistachios and 

plums/prunes. Humans may be exposed to forchlorfenuron in food and drinking water, since 

forchlorfenuron may be applied directly to growing crops and application may result in 

forchlorfenuron reaching surface and ground water sources of drinking water. There are no 

residential uses of forchlorfenuron, so there is not likely to be exposure in residential or nonoccupational settings. In an occupational setting, applicators may be exposed while handling the 

pesticide prior to application, as well as during application. There is a potential for postapplication exposure for workers re-entering treated fields. 

Risk assessments have been previously conducted for forchlorfenuron, but no new toxicity data 

have been received since the previous risk assessment. A detailed description of the toxicity data 

and metabolism information may be found in the risk assessment dated 3/11/08 (D. Davis, 

D341628). This risk assessment considers all of the aforementioned exposure pathways based 

on the proposed new uses of forchlorfenuron, but also considers the existing uses as well. 

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 National 

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

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

analyzed and categorized by subgroups based on age, season of the year, ethnic group, and 

region of the country. Additionally, OPP is able to assess dietary exposure to smaller, 
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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 postapplication are evaluated. Further considerations are 

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

specialized software and models that consider exposure to bystanders and farm workers as well 

as lifestyle and traditional dietary patterns among specific subgroups.

4.0 Hazard Characterization and Dose-Response Assessment

No new toxicity and/or rat metabolism data have been received since the last risk assessment, 

which did not identify any data deficiencies with respect to toxicology. Based on the current 40 

CFR Part 158 data requirements, an immunotoxicity study, subchronic dermal and inhalation 

toxicity studies, and acute and subchronic neurotoxicity studies are required for forchlorfenuron. 

However, the Hazard and Science Policy Council (HASPOC) concluded that these studies 

should be waived for forchlorfenuron (TXR No. 0056596, dated March 12, 2013 and TXR No. 

0056795, dated September 17, 2013) This assessment includes summaries of prior assessments 

(D. Davis, 3/11/08, D341628).

4.1 Summary of Toxicological Effects

Forchlorfenuron is a plant growth regulator that is absorbed by leaves, stem, cotyledon, and 

germinated seeds. It promotes cell division, differentiation, and development; induces budding of 

callus; controls apical dominance; breaks dormancy of lateral buds; promotes germination; 

delays the aging process; maintains chlorophyll in excised leaves; regulates the transport of 

nutrients; and promotes fruit formation. 

Metabolism studies in rats indicate that forchlorfenuron is rapidly absorbed and metabolized, 

with half of the radiolabel excreted via the urine and feces within 16 hours. The majority of the 

recovered radiolabel was identified as the conjugate, forchlorfenuron sulfate, with the parent 

compound accounting for only a small component of that excreted. A dermal absorption study is 

not available for forchlorfenuron, and 100% dermal absorption is used for risk assessment.

Forchlorfenuron is not acutely toxic via the oral, dermal, and inhalation routes. Dose-related 

effects noted in the dog following subchronic and chronic exposure were generally limited to 

decreased body weight and body-weight gain. In the rat, the only organ that appeared to be 

affected was the kidney, which showed suppurative inflammation, suppurative pyelonephritis, 

non-suppurative interstitial nephritis, and cortical cysts following chronic exposure. 

Developmental toxicity was not observed in the rabbit but was observed in the rat (decreased 

fetal body weight) only at a maternally-toxic dose level (decreased body weight and death). 

Forchlorfenuron did not induce any signs of reproductive toxicity or neurotoxic potential. The 

developmental toxicity studies in rats and rabbits, as well as the reproductive toxicity study in 

rats, did not demonstrate any pre- or postnatal sensitivity. There is no evidence of 

immunotoxicity, and the requirement for an immunotoxicity study has been waived.
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A repeated exposure study via either the dermal or inhalation routes of exposure is not available 

for forchlorfenuron; however, these studies have been waived. It is not a dermal sensitizer or 

dermal irritant, but it is a mild eye irritant. No neurotoxicity studies are available on 

forchlorfenuron, but there was no evidence of neurotoxicity in any of the submitted studies and 

these studies have been waived. 

The database for carcinogenicity is complete, and forchlorfenuron is classified as not likely to be 

a human carcinogen. The mutagenicity/genetic toxicity database is considered complete, and 

there is no concern for mutagenicity. 

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

The Food Quality Protection Act (FQPA) safety factor for the protection of infants and children 

has been reduced to 1X. There are no concerns and no residual uncertainties with regard to preand/or postnatal toxicity. An FQPA Safety Factor of 1X is appropriate for the following reasons:

The database for prenatal developmental and reproductive toxicity is considered adequate to 

assess safety for infants and children. There is no evidence of increased qualitative or

quantitative susceptibility in the developmental rat and rabbit studies or in the rat 2-generation 

reproduction study. These studies have clearly defined NOAEL/LOAELs. There is a lack of 

evidence of neurotoxicity in any study on forchlorfenuron. 

Exposure estimates (food and water) are not likely to underestimate risk.

Further details may be found in the following sections.

4.2.1 Completeness of the Toxicology Database

The toxicology database for forchlorfenuron is complete. Acceptable rat and rabbit 

developmental toxicity studies and a rat 2-generation reproduction study are available. The 

HED’s Hazard and Science Policy Council (HASPOC) determined that the acute and subchronic 

neurotoxicity studies and the immunotoxicity study may be waived (HASPOC Memo, TXR No. 

0056596, 3/12/13 and TXR No. 0056795, dated 9/17/13). 

All other required toxicology studies have been submitted and are considered acceptable. 

4.2.2 Evidence of Neurotoxicity

There is no concern for neurotoxicity resulting from exposure to forchlorfenuron, based on a lack 

of evidence of neurotoxicity in any study on forchlorfenuron. There is not a concern for 

developmental neurotoxicity.

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

There is no evidence of increased susceptibility [qualitative and quantitative] following in utero

exposure to forchlorfenuron in either the rat or rabbit developmental toxicity study, and there is 
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no evidence of increased susceptibility [qualitative or quantitative] following in utero and/or pre-

/post-natal exposure in the 2-generation reproduction study in rats. 

Forchlorfenuron has been evaluated for potential developmental effects in the rat and rabbit 

(gavage administration). Maternal toxicity included death of one dam and significantly decreased 

body weight in the maternal rat, and maternal toxicity was not observed in the maternal rabbit. 

Decreased fetal body weight and a slight increase in the incidence of delayed ossification were 

observed in the rat at the same dose level at which the maternal effects described above were 

seen, whereas there were no developmental effects in the rabbit. Retarded growth was observed 

in the offspring in the 2-generation reproduction study at a dose level where clinical signs of 

toxicity and decreased body weight occurred in the parental rats. 

4.2.4 Residual Uncertainty in the Exposure Database

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

unrefined and reflect tolerance-level residue in food, 100% crop treated, and upper-bound 

drinking water estimates based on modeling. These assumptions and refinements are detailed in 

the Section 5.4.1. There are no non-occupational exposures for forchlorfenuron. 

4.3 Toxicity Endpoint and Point of Departure Selections

There have been no changes to the prior dose-response assessment, recommendations for 

combining routes of exposure, and/or cancer classification. 

Refer to Table 4.3.1 for the summary of the toxicological doses and endpoints for 

forchlorfenuron.

Table 4.3.1 Summary of Toxicological Doses and Endpoints for Forchlorfenuron for Use in Dietary and 

Occupational Human Health Risk Assessments

Exposure/ 

Scenario

Point of 

Departure

Uncertainty/FQPA 

Safety Factors

RfD, PAD, 

Level of 

Concern for 

Risk 

Assessment

Study and Toxicological Effects

Acute Dietary 

(All 

Populations)

No appropriate endpoint attributable to a single exposure (dose) was identified from oral toxicity 

studies, including the developmental studies; therefore an acute endpoint was not selected and an 

acute dietary risk assessment is not required. 

Chronic 

Dietary (All 

Populations)

NOAEL = 

7 

mg/kg/day

UFA= 10x

UFH=10x

FQPA SF= 1x

chronic RfD = 

0.07 

mg/kg/day

cPAD = 0.07 

mg/kg/day

Chronic oral toxicity study – rat

LOAEL = 93 mg/kg/day, based on decreased 

body weight/body-weight gain/food 

consumption, and kidney toxicity (suppurative 

inflammation in males; nonsuppurative 

interstitial nephritis in females)

Dermal ShortTerm (1-30 

days)

oral NOAEL 

= 100 

mg/kg/day

(dermal 

absorption 

rate = 100%)

UFA= 10x

UFH=10x

FQPA SF= 1x

Residential 

LOC for 

MOE = 100

Occupational 

LOC for 

MOE = 100

Developmental toxicity study – rabbit

LOAEL = 125 mg/kg/day, based on bodyweight loss during dosing period in the rangefinding study
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Table 4.3.1 Summary of Toxicological Doses and Endpoints for Forchlorfenuron for Use in Dietary and 

Occupational Human Health Risk Assessments

Exposure/ 

Scenario

Point of 

Departure

Uncertainty/FQPA 

Safety Factors

RfD, PAD, 

Level of 

Concern for 

Risk 

Assessment

Study and Toxicological Effects

Dermal 

IntermediateTerm (1-6 

months)

oral NOAEL 

= 87 

mg/kg/day

(dermal 

absorption

rate = 100%)

UFA= 10x

UFH=10x

FQPA SF= 1x

Residential 

LOC for 

MOE = 100

Occupational 

LOC for 

MOE = 100

Chronic oral toxicity study - dog 

LOAEL = 195 mg/kg/day based on decreased 

body weight/body-weight gain/food 

consumption

Inhalation 

Short- Term 

(1-30 days)

oral 

NOAEL= 

100 

mg/kg/day

(inhalation 

toxicity 

assumed to 

be equivalent 

to oral )

UFA= 10x

UFH=10x

FQPA SF= 1x

Residential 

LOC for 

MOE = 100 

Occupational 

LOC for 

MOE = 100

Developmental toxicity study – rabbit

LOAEL = 125 mg/kg/day based on bodyweight loss during dosing period in the rangefinding study

Inhalation 

IntermediateTerm (1-6 

months)

oral NOAEL 

= 87 

mg/kg/day

(inhalation 

toxicity 

assumed to 

be equivalent 

to oral)

UFA= 10x

UFH=10x

FQPA SF= 1x

Residential 

LOC for 

MOE = 100 

Occupational 

LOC for 

MOE = 100

Chronic oral toxicity study - dog 

LOAEL = 195 mg/kg/day based on decreased 

body weight/body-weight gain/food 

consumption

Cancer (oral, 

dermal, 

inhalation)

Classification: not likely to be a human carcinogen, based on two adequate rodent carcinogenicity 

studies.

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

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

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

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

sensitivity among members of the human population (intraspecies). UFL = use of a LOAEL to extrapolate a 

NOAEL. UFS = use of a short-term study for long-term risk assessment. UFDB = to account for the absence of key 

data (i.e., lack of a critical study). FQPA SF = FQPA Safety Factor. PAD = population adjusted dose (a = acute, c 

= chronic). RfD = reference dose. MOE = margin of exposure. LOC = level of concern. N/A = not applicable.

5.0 Dietary Exposure and Risk Assessment 

5.1 Residues of Concern Summary and Rationale
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The qualitative nature of the residue in plants is understood, based on acceptable apple and 

kiwifruit metabolism studies and supportive grape metabolism data. The residue of concern for 

both tolerance expression and risk assessment is parent forchlorfenuron.

The nature of the residue in livestock cannot be delineated at this time. There are significant 

deficiencies in the submitted goat metabolism study that preclude a clear understanding of the 

nature of the residue in ruminants, and a poultry metabolism study is not available.

The nature of the residue in rotational crops has not been delineated as a confined rotational crop 

study has not been submitted to the Agency.

HED has determined that the residue of concern in drinking water is parent forchlorfenuron only. 

Table 5.1. Summary of Metabolites and Degradates to be included in the Risk 

Assessment and Tolerance Expression

Matrix Residues included in Risk 

Assessment

Residues included in 

Tolerance Expression

Plants

Primary Crop Forchlorfenuron Forchlorfenuron

Rotational Crop Not Determined Not Determined

Livestock

Ruminant Not Determined Not Determined

Poultry Not Determined Not Determined

Drinking Water Forchlorfenuron Not Applicable

5.2 Food Residue Profile

Available metabolism data shows that forchlorfenuron does not significantly translocate, 

therefore residues from foliar application are likely to be surface residues. However, 

forchlorfenuron is used at relatively low application rates, and the submitted field trial studies 

demonstrate that when applied at early nut/fruit formation stages, quantifiable residues are not 

likely in human food items and quantifiable residues are not seen in sweet cherries treated up to 

7-days before harvest. Further, quantifiable residues were not seen in processed commodities 

resulting from the drying of fresh plums and figs. Quantifiable residues were only seen in 

almond hulls and occurred at low levels in the only animal feedstuff associated with this action. 

5.3 Water Residue Profile

For the chronic dietary analysis, the maximum annual mean chronic estimated drinking water 

concentration (EDWC) value (7.3 μg/L) derived from the PRZM-GW model was used as a point 

estimate to represent chronic drinking water concentration. The EDWC of 7.3 μg/L is a postbreakthrough mean that occurs after 88 years of annual use. This maximum post-breakthrough 

average value was from the WI corn modeled scenario. The PRZM/EXAMS (surface water) 

EDWCs were considerably lower than the PRZM-GW EDWC (groundwater). 
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Table 5.3 Summary of Estimated Surface Water and Groundwater Concentrations 

for Forchlorfenuron.

Scenario Surface Water Conc., ppb a Groundwater Conc., ppb b

Acute 0.6 8.8

Chronic (non-cancer) 0.21 7.3

a

From the Tier II PRZM-EXAMS - Index Reservoir model; 34% PCA

b

From the Tier I PRZM-GW model.

Source: G. Orrick, D407227, 3/11/13.

5.4 Dietary Risk Assessment

5.4.1 Description of Residue Data Used in Dietary Assessment

Tolerances are established for residues of forchlorfenuron in/on grapes at 0.03 ppm, raisins at 

0.06 ppm, kiwifruit at 0.04 ppm, and the bushberry subgroup 13-07B at 0.01 ppm [40 CFR 

§180.569(a)]. There are no forchlorfenuron tolerances established for animal commodities.

HED has determined that the residues of concern in plants include only the parent compound for 

purposes of both the tolerance expression and risk assessment. No animal commodity tolerances 

are required to support the existing or newly proposed uses for forchlorfenuron.

Tolerance level residues and 100% crop treated was assumed for all existing and new uses. The 

recommended tolerances of 0.01 ppm were used for the new uses on almonds, sweet cherries, 

figs, pears, plums and pistachios under the proposed use (D414083, D. Davis, 9/12/13). HED 

notes that the temporary tolerances in/on olive and apple have expired; thus, these commodities 

were not included in the assessment. DEEM (Version 7.81) default processing factors were used 

for dried pears, prune juice, cranberry juice and grape juice. A processing factor was not used 

for raisins because a separate tolerance has been established for that commodity. In addition, a 

processing factor was not used for prunes (dried plums) because data show that residues of

forchlorfenuron in prunes are not likely to exceed 0.01 ppm, the tolerance established for fresh 

plums. A processing factor was also not used for dried figs because data show that residues of 

forchlorfenuron in dried figs are not likely to exceed the tolerance for fresh figs (D414083, D. 

Davis, 9/12/13). Lastly, the maximum annual mean groundwater concentration from the PRZMGW model was incorporated into the assessment.

5.4.2 Percent Crop Treated Used in Dietary Assessment

Percent crop treated (%CT) data were not applied to the chronic assessment; 100% CT was 

assumed for all commodities. 

5.4.3 Acute Dietary Risk Assessment

An acute dietary endpoint was not selected since there were no effects seen in the toxicological 

database that were attributable to a single dose of forchlorfenuron; therefore, quantification of 

acute dietary exposure and risk assessment is not required.
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5.4.4 Chronic Dietary Risk Assessment

HED conducted a Tier 1, screening level chronic dietary (food and drinking water) risk 

assessment. The assessment assumed that all commodities will contain residues of 

forchlorfenuron at the tolerance level. When available, data from processing studies were used 

to estimate residue in processed commodities; however, in the absence of data, DEEM default 

processing factors were incorporated into the assessment. Lastly, the highest modeled estimate 

of the exposure to drinking water concentrations was used in this assessment. Based on the 

conservative inputs into the analysis, it is unlikely that the assessment will underestimate chronic 

dietary risks from the proposed and existing uses of forchlorfenuron. 

HED is concerned when dietary risk exceeds 100% of the PAD. The dietary analysis estimates 

the dietary exposure of the U.S. population and various population subgroups. The results are 

reported for the general U.S. Population, all infants (<1 year old), children 1-2, children 3-5, 

children 6-12, youth 13-19, females 13-49, adults 20-49, and adults 50-99 years. 

For forchlorfenuron, the U.S. population and all population subgroups had dietary risk (food and 

drinking water) estimates that were below 1% of the cPAD. The general population had an 

exposure of 0.000175 mg/kg/day. The most highly exposed subpopulation, all infants, had an 

exposure of 0.000447 mg/kg/day. The results of the chronic dietary exposure analysis for all 

subpopulations are summarized in Table 5.4.6. 

5.4.5 Cancer Dietary Risk Assessment

Forchlorfenuron has been classified as not likely to be carcinogenic; therefore quantification of

cancer dietary exposure and risk assessment is not required.

5.4.6 Summary Table

Table 5.4.6. Summary of Dietary (Food and Drinking Water) Exposure and Risk 

for Forchlorfenuron.

Population Subgroup

Chronic Dietary

Dietary Exposure

(mg/kg/day) % cPAD*

General U.S. Population 0.000175 <1

All Infants (<1 year old)* 0.000447 <1

Children 1-2 years old 0.000346 <1

Children 3-5 years old 0.000261 <1

Children 6-12 years old 0.000165 <1

Youth 13-19 years old 0.000122 <1

Adults 20-49 years old 0.000167 <1

Adults 50-99 years old 0.000168 <1

Females 13-49 years old 0.000167 <1

*The subpopulation(s) with the highest risk estimates. 
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6.0 Residential (Non-Occupational) Exposure/Risk Characterization

6.1 Residential Handler Exposure

There are no registered or proposed non-occupational uses for forchlorfenuron; therefore a 

residential handler exposure and risk assessment is not required.

6.2 Post-Application Exposure

There are no registered or proposed uses for forchlorfenuron which would result in residential 

(non-occupational) post application exposures; therefore a post application exposure and risk 

assessment is not required.

6.3 Residential Bystander Post-application Inhalation Exposure

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

assessment was not performed for forchlorfenuron at this time primarily because of the low acute 

inhalation toxicity (Toxicity Category IV), low vapor pressure (3.5 x 10-5 torr (25°C)), and low 

proposed use rate (0.025 lb ai/acre). However, 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 is in the 

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

identify the need for and, subsequently, the way to incorporate post-application inhalation 

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

Agency may revisit the need for a quantitative post-application inhalation exposure assessment 

for forchlorfenuron.

6.4 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 forchlorfenuron. 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). 2 The Agency is also taking means to qualitatively and 

qualitatively address spray drift as a potential source of exposure in risk assessments for 

pesticides through existing programs such as Ag Drift and chemical specific properties of 

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. 

 

2 Available: http://www.epa.gov/opp00001/factsheets/spraydrift.htm 
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7.0 Aggregate Exposure/Risk Characterization

In accordance with the FQPA, HED must consider and aggregate (add) pesticide exposures and 

risks from three major sources: food, drinking water, and residential exposures. In an aggregate 

assessment, exposures from relevant sources are added together and compared to quantitative 

estimates of hazard (e.g., a NOAEL or PAD), or the risks themselves can be aggregated. When 

aggregating exposures and risks from various sources, HED considers both the route and 

duration of exposure.

7.1 Acute Aggregate Risk

An acute endpoint was not selected; therefore quantification of acute aggregate risk is not 

required.

7.2 Short-Term Aggregate Risk

Since there are no uses for forchlorfenuron that would result in residential (non-occupational) 

exposure, a short-term aggregate risk assessment is not required. 

7.3 Intermediate-Term Aggregate Risk

Since there are no uses for forchlorfenuron that would result in residential (non-occupational) 

exposure, an intermediate-term aggregate risk assessment is not required. 

7.4 Chronic Aggregate Risk

The chronic aggregate risk assessment includes only food and water exposure only. The chronic 

food plus drinking water risk estimates are not of concern to HED for the general population and 

all population subgroups. Refer to section 5.4.4 for a detailed discussion of the chronic dietary

risk assessment.

7.5 Cancer Aggregate Risk

Since forchlorfenuron has been classified as not likely to be carcinogenic, quantification of

aggregate cancer risk is not required.

8.0 Cumulative Exposure/Risk Characterization

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

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

to forchlorfenuron and any other substances and forchlorfenuron 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 forchlorfenuron 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 
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policy statements released by EPA’s Office of Pesticide Programs concerning common 

mechanism determinations and procedures for cumulating effects from substances found to have 

a common mechanism on EPA’s website at http://www.epa.gov/pesticides/cumulative/.

9.0 Occupational Exposure/Risk Characterization

9.1 Short-/Intermediate-Term Handler Risk

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

application process. HED has determined that there are potential exposures to handlers during 

application of forchlorfenuron. Scenarios assessed include mixing/loading dry flowable

formulations for groundboom and airblast applications and applying sprays with groundboom 

and airblast equipment. Although the product associated with the new use is a liquid product, the 

assessment completed for mixing/loading dry flowable is protective of the use as a liquid; 

exposure for mixing/loading dry flowable is greater than exposure for mixing/loading liquids3. 

No chemical-specific data for assessing human exposures during pesticide handling activities 

were submitted to the Agency in support of this Section 3 application; therefore, handler 

exposure was assessed using the Pesticide Handlers Exposure Database version 1.1 (PHED 

V.1.1). The forchlorfenuron product labels direct mixers, loaders, applicators and other handlers 

to wear baseline PPE plus chemical-resistant gloves. The occupational handler exposure and risk 

estimates indicate that short- and intermediate-term MOEs are not of concern to HED (i.e., 

MOEs > 100) with label-specified PPE. Total MOEs for the occupational handler assessment 

range from 3,300 to 94,000. While the assessment has been completed for both the short- and 

intermediate-term exposure durations, the 1 application per season make the short-term exposure 

duration risk estimates more probable from a risk management perspective.

 

3 Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” ([March 2012]);
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Table 9.1.1. Occupational Handler Short-Term Non-Cancer Exposure and Risk Estimates for Forchlorfenuron. 

Exposure Scenario Crop or 

Target

Dermal Unit 

Exposure (μg/lb 

ai)1

Inhalation Unit 

Exposure (μg/lb 

ai)1

Maximum 

Application 

Rate2

Area 

Treated or 

Amount 

Handled 

Daily3

Dermal Inhalation Total

Mitigation Level Mitigation Level Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day)6 MOE7 MOE8

Mixer/Loader

DF - Airblast applications Orchard 51.6 – SL/G 8.96 0.03 40 0.000897 110000 0.000157 640000 94000

DF - Groundboom 

applications

Field Crops 51.6 – SL/G 8.96 0.03 80 0.0018 56000 0.000312 320000 48000

Applicator

Liquid - Airblast 

applications

Orchard 1770 – SL/no G 4.71 – no-R

0.03 40 0.0307 3300 0.0000819 1200000 3300

Liquid - Groundboom 

applications

Field Crops 78.6 – SL/no-G 0.34 – no-R

0.03 80 0.00274 36000 0.0000118 8500000 36000

1 Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” ([March 2012]); Level of mitigation: Baseline, PPE, Eng. Controls.

2 Based on registered or proposed label (Reg. No. 71049-2).

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 (%) ÷ BW (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) ÷ BW (kg).

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

8 Total MOE = NOAEL (mg/kg/day) ÷ Dermal Dose + Inhalation Dose OR Total MOE = 1 ÷ (1/Dermal MOE + 1/Inhalation MOE).
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Table 9.1.2. Occupational Handler Intermediate-Term Non-Cancer Exposure and Risk Estimates for Forchlorfenuron. 

Exposure Scenario Crop or 

Target

Dermal Unit 

Exposure (μg/lb 

ai)1

Inhalation Unit 

Exposure (μg/lb 

ai)1

Maximum 

Application 

Rate2

Area 

Treated or 

Amount 

Handled 

Daily3

Dermal Inhalation Total

Mitigation Level Mitigation Level Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day)6 MOE7 MOE8

Mixer/Loader

DF - Airblast applications Orchard 51.6 – SL/G 8.96 0.3 40 0.000774 110000 0.000135 640000 94000

DF - Groundboom 

applications

Field Crops 51.6 – SL/G 8.96 0.3 80 0.00155 56000 0.000269 320000 48000

Applicator

Liquid - Airblast 

applications

Orchard 1770 – SL/no G 4.71 – no-R

0.3 40 0.0265 3300 0.0000706 1200000 3300

Liquid - Groundboom 

applications

Field Crops 78.6 – SL/no-G 0.34 – no-R

0.3 80 0.00236 37000 0.0000102 8500000 37000

1 Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” ([March 2012]); Level of mitigation: Baseline, PPE, Eng. Controls.

2 Based on registered or proposed label (Reg. No. 71049-2).

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 (%) ÷ BW (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) ÷ BW (kg).

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

8 Total MOE = NOAEL (mg/kg/day) ÷ Dermal Dose + Inhalation Dose OR Total MOE = 1 ÷ (1/Dermal MOE + 1/Inhalation MOE).
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9.2 Short-/Intermediate-Term Post-Application Risk

9.2.1 Dermal Postapplication Risk

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

present in an environment that has been previously treated with a pesticide (also referred to as reentry exposure). HED has determined that there are potential exposures to persons entering 

treated sites (e.g., harvesters) after application of forchlorfenuron is complete. Since no 

postapplication data were submitted in support of this registration action, dermal exposures 

during postapplication activities were estimated using dermal transfer coefficients from the 

Science Advisory Council for Exposure Standard Operating Procedure (SOP) Number 3.1: 

Agricultural Transfer Coefficients, August 2000 and using dislodgeable foliar residue values 

estimated using the standard assumption that 25 percent of the application rate is initially 

available to dislodge from foliar surfaces and the residues dissipate at a rate of 10 percent per 

day. The results of the postapplication occupational exposure and risk assessment indicate that 

risk estimates are not a concern on the day of application (12 hours following the end of the 

application). HED concurs with a 12-hour REI for all proposed crops.

The table below summarizes the occupational post-application risk estimates for the proposed 

applications of forchlorfenuron. The occupational post-application exposure and risk estimates 

indicate that short- and intermediate-term MOEs are not of concern to HED (i.e., MOEs > 100). 

MOEs for the occupational post-application assessment range from 730 to 10,000.

Table 9.2.1. Occupational Post-application Non-Cancer Exposure and Risk Estimates for forchlorfenuron.

Crop/Site Activities Transfer Coefficient 

(cm2/hr) DFR/TTR1 Dermal Dose (mg/kg/day)2 MOE3

Short-term

Sweet 

cherry/plum/pear/fig Hand harvesting 1400 0.841 0.137 730

Sweet 

cherry/plum/pear/fig Hand pruning 580 0.841 0.057 1800

fig transplanting 230 0.841 0.02 4500

Almond/pistachio harvesting 190 0.841 0.02 5400

Almond/pistachio Orchard maintenance 100 0.841 0.009 10000

Intermediate-term

Sweet 

cherry/plum/pear/fig Hand harvesting 1400 0.841 0.12 730

Sweet 

cherry/plum/pear/fig Hand pruning 580 0.841 0.057 1800

fig transplanting 230 0.841 0.02 4500

Almond/pistachio harvesting 190 0.841 0.02 5400

Almond/pistachio Orchard maintenance 100 0.841 0.008 10000

1 DFR = Application Rate × F × (1-D)t × 4.54E8 μg/lb × 2.47E-8 acre/cm2; where F = 0.25 

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

3 MOE = POD (mg/kg/day) / Daily Dermal Dose. Daily Dermal Dose = [DFR/TTR (μg/cm2) × TC × 0.001 mg/μg × 8 hrs/day × dermal 

absorption factor (%)] BW (kg).
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Restricted Entry Interval

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

Forchlorfenuron is classified as Toxicity Category III via the dermal route and Toxicity Category 

IV for skin irritation potential. It is not a skin sensitizer. Short- and intermediate-term postapplication risk estimates were not a concern on day 0 (12 hours following application) for all 

post-application activities. Under 40 CFR 156.208 (c) (2) (iii), active ingredient’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 forchlorfenuron. 

9.2.2 Inhalation Postapplication Risk

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

assessment was not performed for forchlorfenuron at this time primarily because of the low acute 

inhalation toxicity (Toxicity Category IV), low vapor pressure (3.5 x 10-5 torr (25°C)), and the 

low proposed use rate (0.025 lb ai/A). However, there are multiple potential sources of postapplication 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 is in the 

process of evaluating the SAP report as well as available post-application inhalation exposure 

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

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

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

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

post-application inhalation exposure assessment for forchlorfenuron.

Although a quantitative occupational postapplication inhalation exposure assessment was not 

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

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

higher exposure than postapplication exposure. Therefore, it is expected that these handler 

inhalation exposure estimates would be protective of most occupational postapplication 

inhalation exposure scenarios.

10.0 References

Davis, D. 3/11/08. D341628. Forchlorfenuron: Human Health Risk Assessment for Proposed 

Uses on the Bushberry Subgroup 13 B and to Support a Requested Experimental Use Permit on 

Almonds, Sweet Cherries, Figs, Pears, Pistachios and Plums/Prunes. PC Code: 128819, Petition 

No: 7E7228, DP Barcode: D341628.
Forchlorfenuron Human Health Risk Assessment DP No. D407226

Page 25 of 32

Davis, D. 9/12/13. D414083. Forchlorfenuron (CPPU). Petition for the Establishment of 

Permanent Tolerances and Registration for Use on Almond, Cherry (Sweet), Fig, Pear, Pistachio, 

Plum/Prune. Summary of Analytical Chemistry and Residue Data.

Orrick, G. 3/11/13. D407227. Forchlorfenuron: Drinking Water Exposure Assessment for 

Proposed New Uses on Almonds, Sweet Cherries, Figs, Pears, Pistachios, and Plums Including 

Prunes

Lloyd, M. 1/23/13. D407548. Forchlorfenuron (CCPU) - Occupational/Residential 

Exposure/Risk Assessment for the Use of Forchlorfenuron on Figs, Plums, Pears, Sweet 

Cherries, Almonds and Pistachios.

LaMay, A. 2/6/14. D414331. Forchlorfenuron- Chronic Aggregate Dietary (Food and Drinking 

Water) Exposure and Risk Assessment for the Section 3 Registration Action on Almonds, Sweet 

Cherries, Figs, Pears, Pistachios and Plums/Prunes
Forchlorfenuron Human Health Risk Assessment DP No. D407226

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Appendix A. Toxicology Profile and Executive Summaries

A.1 Toxicology Data Requirements

The requirements (40 CFR 158.340) for food use for forchlorfenuron are in Table 1. Use of the 

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

Study Technical

Required Satisfied

870.1100 Acute Oral Toxicity................................................................

870.1200 Acute Dermal Toxicity...........................................................

870.1300 Acute Inhalation Toxicity.......................................................

870.2400 Primary Eye Irritation.............................................................

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

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

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

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

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

870.3200 21/28-Day Dermal..................................................................

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

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

yes

yes

yes

no

CR

yes

yes

---

A

---

---

A

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

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

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

yes

yes

yes

yes

yes

yes

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

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

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

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

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

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................................

yes

yes

yes

yes

yes

yes

yes

yes

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

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

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

870.6200b 90 Day Neurotox. Screening Battery (rat)...............................

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

no

no

yes

yes

CR

---

---

---

A

---

A

---

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

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

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

yes

CR

yes

yes

---

---

B

Non guideline Thyroid MOA Investigation Study no ---

AWaived by HASPOC (TXR# 0056596)

B Waived by HASPOC (TXR#0056795)
Forchlorfenuron Human Health Risk Assessment DP No. D407226

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A.2 Toxicity Profiles

Table A.2.1 Acute Toxicity Profile - Forchlorfenuron

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

870.1100 Acute oral [rat] 44394609 LD50 (mg/kg) = 

M = 4904

F = 4899

III

870.1200 Acute dermal [rabbit] 44394611 LD50 (mg/kg) = 

>2000

III

870.1300 Acute inhalation [rat] 44394608 LC50 (mg/L) = 

>3.0

IV

870.2400 Acute eye irritation [rabbit] 44394607 Mild eye irritant III

870.2500 Acute dermal irritation [rabbit] 44394610 Non-irritant IV

870.2600 Skin sensitization [guinea pig] 44394606 Non-sensitizer -

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

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.3100 90-Day oral 

toxicity (Fischer

344 rats)

44394614 (1987)

Acceptable/Guideline

0, 200, 1000, 5000 ppm

M: 0, 16, 79, 400mg/kg/day

F: 0, 17, 84, 428 mg/kg/day

NOAEL = 400 (male)

LOAEL = no adverse effects observed (male)

NOAEL = 84 mg/kg/day (female)

LOAEL = 428 mg/kg/day (female), based on 

decrease BW, BW gain & food efficiency

870.3150 Subchronic oral

toxicity 

(Beagle dog)

44394615 (1987/1993)

Acceptable/Guideline

0, 50, 500, 5000 ppm

M: 0, 1.8, 16.8, 162.4 

mg/kg/day

F: 0, 1.8, 19.1, 188.7 

mg/kg/day

NOAEL = 16.8/19.1 mg/kg/day (male/female)

LOAEL = 162.4/188.7 mg/kg/day 

(male/female), based on decreases ( 10%) in 

BW gain, FC & food efficiency

870.3700a Developmental 

toxicity

(Sprague Dawley 

Crl:CD®BR rat)

(GD 6-15)

44394612 (1986)

45840123 (2002)

Acceptable/Guideline

0, 100, 200, 400 mg/kg/day

45840113 (2002)

analytical information

Maternal NOAEL = 200 mg/kg/day

Maternal LOAEL = 400 mg/kg/day, based on 

death of one dam, increased incidence of 

alopecia; significantly decreased in BW & BW 

gains

Developmental NOAEL = 200 mg/kg/day

Developmental LOAEL = 400 mg/kg/day, 

based on decreased mean fetal BW, a slight 

increase in the incidence of delayed ossification 

of the sternebrae
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Table A.2.2 Subchronic, Chronic and Other Toxicity Profile – Forchlorfenuron

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.3700b Prenatal 

developmental in 

(New Zealand 

White rabbit)

GD 6-18

44394613 (1986)

45840122 (2002)

Acceptable/Guideline

0, 25, 50, 100 mg/kg/day

44359526 (1985) - range 

finding

0, 125, 250, 500, 1000 

mg/kg/day

45840113 (2002)

analytical information

Maternal NOAEL = ≥100 mg/kg/day

Maternal LOAEL = not determined.

Developmental NOAEL = ≥100 mg/kg/day

Developmental LOAEL = not determined.

870.3800 Reproduction and 

fertility effects

(Sprague Dawley 

Crl:CD®BR rat)

44394616 (1997)

Acceptable/Guideline

0, 150, 2000, 7500 ppm

F0M: 0, 11, 144, 544 

mg/kg/day

F0F: 0, 13, 169, 701 

mg/kg/day

F1M: 0, 13, 168, 829 

mg/kg/day 

F1F: 0, 15, 202, 926 

mg/kg/day

Parental NOAEL = 11 mg/kg/day.

Parental LOAEL = 144 mg/kg/day, based on 

decreased food consumption (F0 & F1 males), 

clinical signs of toxicity, and lower BW in F1

males and females

At HDT, decreased BW and kidney lesions 

(suppurative inflammation in F0 rats; 

suppurative pyelonephritis in F1 rats)

Reproductive NOAEL = 7500 ppm (544/701

mg/kg/day (HDT).

Reproductive LOAEL not determined.

Offspring NOAEL = 11 mg/kg/day

Offspring LOAEL = 144 mg/kg/day based 

growth retardation in F1 & F2 pups.

At the highest dose tested, increased pup 

mortality (F1a, F1b & F2a), growth retardation in 

F1b, and decrease in F2 pups/litter

870.4100b Chronic toxicity 

(dog)

45840105 (1998)

Acceptable/Guideline

0, 150, 3000, 7500 ppm

M: 0, 5, 87, 195 mg/kg/day

F: 0, 5, 91, 246 mg/kg/day

NOAEL = 87/91 mg/kg/day (male/female)

LOAEL = 195/246 mg/kg/day (male/female), 

based on decreases in BW, BW gains & FC

870.4200 Carcinogenicity 

(Crl:CD-1®(ICR) 

BR mouse)

45840106 (2002)

Acceptable/Guideline

M: 0, 10, 991.4 mg/kg/day 

F: 0, 9.9, 1001.8 mg/kg/day 

NOAEL = 10.0/9.9 mg/kg/day (male/female)

LOAEL = 991.4/1001.8 mg/kg/day 

(male/female), based on decreases in BW & 

BW gains (both sexes)

no evidence of carcinogenicity
Forchlorfenuron Human Health Risk Assessment DP No. D407226

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

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.4300 Combined 

Chronic Toxicity/

Carcinogenicity

(Crl:CD®BR rats)

44394617 (1996)

Acceptable/Guideline

0, 150, 2000, 7500 ppm

M: 0, 7, 93, 352 mg/kg/day

F: 0, 9, 122, 518 mg/kg/day

NOAEL= 7/9 mg/kg/day (male/female)

LOAEL= 93/122 mg/kg/day (male/female), 

based on reduced BW & BW gain & FC; 

kidney toxicity (suppurative inflammation in 

males; non-suppurative interstitial nephritis in 

females)

no evidence of carcinogenicity

870.5265 Salmonella/

mammalian 

activation gene 

mutation assay

44394621 (1985)

Acceptable/Guideline

10-1000 g/plate +S9

2-200 g/plate -S9

Evidence of induced mutant colonies over 

background in tester strain TA1535 in absence 

of S9 (repeat of MRID 44394620).

There is no evidence of reproductive effects (no 

decrease in fertility; no increase in dead 

implants/fetuses) to suggest a genetic 

component

870.5265 Salmonella/

mammalian 

activation gene 

mutation assay

44394620 (1985)

Acceptable/Guideline

10-1000 g/plate +S9

2-200 g/plate -S9

Evidence of a positive response in tester strain 

TA1535 in absence of S9 at 50, 100, and 200 

g/plate; negative ± S9 at all other doses and 

strains (see above)

870.5375 in vitro 

mammalian 

cytogenetics assay 

in Chinese 

Hamster CHO-KI 

cells

44394618 (1985)

Acceptable/Guideline

10, 20, 40, and 80 g/mL ± 

S9 activation

No increase in chromosomal aberrations over 

background ± S9

870.5550 Unscheduled DNA 

synthesis in 

primary rat 

hepatocytes/mam

malian cell 

cultures

44394619 (1985)

Acceptable/Guideline

0.1 to 60 g/mL

Negative for induction of unscheduled DNA 

synthesis
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Table A.2.2 Subchronic, Chronic and Other Toxicity Profile – Forchlorfenuron

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.7485 Metabolism and 

pharmacokinetics

(Sprague Dawley 

rat)

MRID 45840107 (2002)

Acceptable/Guideline

100 mg/kg (acute)

Recovery of 97% (M & F) by 168 hours. 

Absorbed dose 72-84%. Urine 62-74%. Feces 

16-28%. Biliary excretion, 20-23% in bile. 

Urine & feces, elimination half-life 13.1-16.2 

hours. Analyses identified parent and 6 

metabolites in excreta. Parent not in urine and 

1-2% in feces. Major metabolite 

forchlorfenuron sulfate in urine of males (84%) 

and females (57%). Hydroxy forchlorfenuron 

(2 isomers) <4% in urine; predominant 

metabolite in feces (11% males and 18% 

females). Other metabolites include hydroxy 

forchlorfenuron-sulfate, methoxy forchlorfenuron-sulfate, forchlorfenuron glucuronide 

and dihydroxy forchlorfenuron (each<%5). 

Metabolism of forchlorfenuron in rats: 

conjugation with sulfate at phenyl ring before 

(major pathway), conjugation with glucuronide 

at phenyl ring, methylation of hydroxy group of 

hydroxy forchlorfenuron- sulfate and 

hydroxylation of both chloropyridinyl and 

phenyl rings. 
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Appendix B. Physical/Chemical Properties

Table C1. Physico-Chemical Properties

Parameter Value Reference

Melting point/range 165-170°C

EPA Fact Sheet, 9/2004

pH Not determined due to 

low water solubility

Density 1.44 g/ml at 21 °C

Water solubility 39 ppm 

Solvent solubility 17g/100 mL in acetone

Vapor pressure (25°C) 3.5 x10-5torr

Dissociation constant, pKa Not provided

Octanol/water partition coefficient, Log(KOW) 3.2

UV/visible absorption spectrum Not provided
Forchlorfenuron Human Health Risk Assessment DP No. D407226

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Appendix C. Review of Human Research

Human Studies Review

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

intentionally exposed to a pesticide or other chemical. These data, which include studies from 

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

database; and 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 

website4. 

 

4

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

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