UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF 

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES 

MEMORANDUM

DATE: 16-October-2009

SUBJECT: Difenoconazole FQPA Human Health Risk Assessment for the Section 3 

Registration of Difenoconazole New Uses on Bulb Vegetables, Brassica Leafy

Vegetables, Cucurbit Vegetables, Citrus Fruits, Grapes, Pistachios, and Tree Nuts.

PC Code: 128847 DP Barcode: 367382

Decision No.: 403560 Registration No.: 

100-1262, 100-1312, 

100-1278, 100-1313, 

and 100-1317

Petition No.: PP#8F7482 Regulatory Action: Section 3

Risk Assessment 

Type:

Single 

Chemical/Aggregate Case No.: NA

TXR No.: NA CAS No.: 119446-68-3

MRID No.: NA 40 CFR §180.475

FROM: Yan Donovan, Risk Assessor

Bonnie Cropp-Kohlligian, Environmental Scientist

Thurston G. Morton, Chemist

James S Miller, Environmental Scientist

Registration Action Branch IV 

Health Effects Division (HED); 7509P

THROUGH: Ray Kent, Branch Chief

Susan V. Hummel, Senior Chemist

Registration Action Branch IV 

Health Effects Division (HED); 7509P

TO: Rosemary Kearns/Tony Kish (RM 22)

Fungicide Branch

Registration Division (7505P)
Page 2 of 69

Table of Content

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

2.0 Ingredient Profile .............................................................................................................. 8

2.1 Summary of Proposed Uses.......................................................................................... 8

2.2 Structure and Nomenclature...................................................................................... 13

3.0 Hazard Characterization/Assessment........................................................................... 14

3.1 Hazard and Dose-Response Characterization.......................................................... 15

3.1.1 Toxicological Effects and Dose-response .......................................................... 15

3.2 FQPA Considerations................................................................................................. 18

3.2.1. Determination of Susceptibility .............................................................................. 18

3.2.2. Adequacy of Toxicity Database .............................................................................. 18

3.2.3. Degree of Concern Analysis:................................................................................... 18

3.2.4. FQPA Safety Factor Recommendation................................................................... 19

3.3 Endocrine Disruption ................................................................................................. 19

4.0 Public Health and Pesticide Epidemiology Data.......................................................... 19

5.0 Dietary Exposure/Risk Characterization ..................................................................... 19

5.1 Pesticide Metabolism and Environmental Degradation.......................................... 19

5.1.1 Metabolism in Primary Crops........................................................................... 20

5.1.2 Metabolism in Rotational Crops........................................................................ 20

5.1.3 Metabolism in Livestock..................................................................................... 20

5.1.4 Analytical Methodology...................................................................................... 20

5.1.5 Environmental Degradation .............................................................................. 21

5.1.6 Comparative Metabolic Profile.......................................................................... 21

5.1.7 Toxicity Profile of Major Metabolites and Degradates................................... 22

5.1.8 Pesticide Metabolites and Degradates of Concern........................................... 22

5.1.9 Drinking Water Residue Profile ........................................................................ 22

5.1.10 Food Residue Profile........................................................................................... 23

5.1.11 International Residue Limits............................................................................. 25

5.2 Dietary Exposure and Risk ........................................................................................ 25

6.0 Residential (Non-Occupational) Exposure/Risk Characterization ............................ 29

6.1 Residential Handler Exposure and Risk Characterization..................................... 29

7.0 Aggregate Risk Assessments and Risk Characterization............................................ 30

7.1 Acute & Chronic Aggregate Risk.............................................................................. 30

7.2 Short- and Intermediate-Term Aggregate Risk....................................................... 30

8.0 Cumulative Risk Characterization/Assessment........................................................... 31

9.0 Occupational Exposure/Risk Pathway.......................................................................... 31

9.1 Occupational Handler Exposure and Risk............................................................... 31

9.2 Occupational Postapplication Exposure and Risk................................................... 36

10.0 Data Needs and Label Recommendations .................................................................... 38

11.0 References:....................................................................................................................... 41

12.0 Tolerance Summary........................................................................................................ 42

13.0 Appendices....................................................................................................................... 43

Appendix 1: Acute Toxicity Data on Difenoconazole Technical ........................................ 43

Appendix 2: Subchronic, Chronic and Other Toxicity Profile........................................... 44
Page 3 of 69

Appendix 3. Proposed Metabolic Pathway for difenoconazole in Rats............................ 64

Appendix 4 Environmental Fate Degradates..................................................................... 66
Page 4 of 69

1.0 Executive Summary

Difenoconazole is a broad spectrum fungicide belonging to the triazole group of fungicides 

(Group 3). It is currently registered in the U.S. for use as a seed treatment on cereal grains, 

canola, and cotton and for foliar applications to pome fruits, sugar beets, fruiting vegetables, and 

tuberous and corm vegetables. Tolerances for difenoconazole are currently established under 40 

CFR §180.475. Difenoconazole acts by blocking demethylation during sterol biosysnthesis 

which, in turn, disrupts membrane synthesis. 

Proposed Uses

Under PP#8F7482, Syngenta Crop Protection, Inc. is proposing amended Section 3 registration 

for a 2.08 lb/gal emulsifiable concentrate (EC) formulation (InspireTM Fungicide; 100-1262) to 

add uses on bulb vegetables, Brassica leafy vegetables, cucurbit vegetables, citrus fruits, tree 

nuts, and grapes. In addition to adding these new uses to Inspire Fungicide (difenoconazole sole 

ai), the registrant is requesting that some or all of these new uses to be added to the labels of 

other mixture products containing difenoconazole. These products are Inspire TM XT, Revus 

TopTM, Quadris TopTM, and Inspire SuperTM. The subject review addresses the proposed uses 

for difenoconazole only. 

Toxicity/Hazard

Difenoconazole possesses low acute toxicity by the oral, dermal and inhalation routes of 

exposure. It is not considered to be an eye or skin irritant and is not a sensitizer. Difenoconazole 

exhibits some evidence of neurotoxicity in the database, but the effects are transient or occur at 

doses exceeding the limit dose. It is not mutagenic andit is not a developmental or reproductive 

toxicant. Chronic effects in rats and mice are seen as cumulative decreases in body weight gains. 

 No evidence of carcinogenicity was seen in rats. Evidence for carcinogenicity was seen in 

mice where liver tumors were induced at doses which were considered to be excessively high for 

carcinogenicity testing. Treatment-related non-neoplastic lesions were confined to the liver. 

Tumors were observed in mice at 300 ppm and higher; however, based on excessive toxicity

observed at the two highest doses, the absence of tumors at the lower doses and the absence of 

genotoxic effects, HED’s Cancer Peer Review Committee (CPRC) recommended for a cancer 

classification of C (possible human carcinogen). A margin-of-exposure (MOE) approach to 

risk assessment was advocated by the CPRC in July 2007. HED toxicologists reevaluated the 

endpoints selected by the HIARC in 1998 and revisited the FQPA factor, since new studies were 

submitted. HED concluded that the default 10x FQPA Safety Factor (SF) should be reduced to 

1x when assessing dietary and residential exposures 

The toxicological database for difenoconazole is sufficient to conduct this risk assessment. 

However, in accordance with Part 158 Toxicology Data requirements, an immunotoxicity study

(870.7800) is required for difenoconazole.

Endpoints and doses for risk assessment were selected for the following scenarios: Acute dietary

(general population including infants and children), chronic dietary, short-term dermal and shortterm inhalation.
Page 5 of 69

Dietary Exposure/Risk Assessment

HED has examined the residue chemistry database for difenoconazole and has identified several 

residue chemistry data deficiencies. Adequate field trial data have been submitted to support the 

proposed uses of the EC formulation of difenoconazole on bulb vegetables, brassica leafy

vegetables, cucurbit vegetables, citrus fruits, pistachios, tree nuts, and grapes. However, the

limited numbers of side-by-side data indicate that residues from the use of the EW formulation 

are significantly higher than residue levels from the same use of an EC formulation. Hence, 

HED concludes that these side-by-side field trial data do not support the proposed uses of the 

EW formulations on green onions, citrus fruits, cucurbit vegetables, and grapes. Residue data for 

the triazole metabolites (1,2,4-T, TA, and TAA) are available to assess the risk from triazole 

metabolites. 

Acute and chronic dietary (food + water) risk assessments were conducted using the Dietary

Exposure Evaluation Model - Food Consumption Intake Database (DEEM-FCID, ver. 2.03. 

This model uses food consumption data from the United States Department of Agriculture’s 

(USDA’s) Continuing Surveys of Food Intakes by Individuals (CSFII; 1994-1996 and 1998). 

The unrefined acute analysis assumed tolerance-level residues, 100% crop treated (CT), and 

default processing factors. The resulting acute food exposure estimates were less than HED’s 

level of concern (<100% of the acute population-adjusted dose (aPAD)) at the 95th percentile of 

the exposure distribution for the general U.S. population (7% aPAD) and all population subgroups; the most highly exposed population subgroup was Children1-2 years old with 16% 

aPAD. The somewhat refined chronic analysis assumed tolerance-level residues for some 

commodities, field trial residues for the majority of commodities, experimental processing factor 

for some crops, and 100 % CT. The resulting chronic food exposure estimates were less than 

HED’s level of concern for the general U.S. population (17% cPAD) and all population subgroups; the most highly exposed population subgroup was children 1-2 years old with 44% 

cPAD. 

 

Residential Exposure/Risk Assessment

No new residential uses are being requested at this time. However, adults and adolescents may

be exposed to difenoconazole from its currently registered use on ornamentals. These risks have 

been previously assessed. It was concluded that residential pesticide handlers will be exposed to 

short-term duration (1 - 30 days) only. The dermal and inhalation (short-term) residential 

exposure was assessed for a homeowner mixer/loader/applicator wearing short pants and shortsleeved shirts as well as shoes plus socks using a garden hose-end sprayer, “pump-up” 

compressed air sprayer, or backpack sprayer. MOEs are >100; therefore are not of concern. 

With respect to residential post-application exposures, current HED policy (see ExpoSAC 

minutes from 8/19/99 and 10/11/01) specifies that no significant post-application exposure is 

anticipated from ornamentals, either by residents or professional applicators; therefore, no 

residential post-application assessment was conducted.

Aggregate Risk Assessment

Acute and chronic aggregate exposures include food plus drinking water exposures. As stated 
Page 6 of 69

above, acute and chronic aggregate risks are not of concern. Since a common endpoint has been 

identified for assessment of short-term oral, dermal, and inhalation exposures, short-term 

aggregate risk assessment combines chronic dietary (food and water) exposure estimates with 

residential exposure estimates. The proposed residential scenarios result in exposure to only

adults. Aggregate MOEs are ≥180 and are not of concern. 

Triazole metabolites

The aggregate dietary (food + water) acute and chronic dietary exposure analyses for 

difenoconazole metabolite 1,2,4- triazole (1,2,4-T) from all registered and proposed triazolebased pesticide uses are conducted separately (Memo, T. Morton, D367860, 13-AUG-09) as an 

update to the previously conducted aggregate dietary exposure risk assessment for 1,2,4-T 

(Memo, M. Sahafeyan, DP#341803, 30-OCT-07). The updated 1,2,4-T dietary risk, adding the 

new use sites associated with the subject petition, showed only a very minimal increase from the 

previous risk estimates and therefore still is not of concern. 

The aggregate dietary (food + water) acute and chronic dietary exposure analyses were also 

conducted separately for difenoconazole metabolites triazole alanine (TA) and triazole acetic 

acid (TAA) from all registered and proposed triazole-based pesticide uses (Memo, T. Morton, 

D367860, 13-AUG-09) as an update to the previously conducted aggregate dietary exposure risk 

assessment for TA + TAA (M. Sahafeyan, DP#344298, 30-OCT-07). The updated TA+TAA 

dietary risk, adding the new use sites associated with the subject petition, showed only a very

minimal increase from the previous risk estimates and therefore still is not of concern. 

Occupational Handler and Postapplication Exposure/Risk Assessment

Based on the label information, HED believes occupational pesticide handlers will be exposed to 

difenoconazole for short-term duration (1 - 30 days), but not to intermediate-term (1 - 6 months) 

duration. Mixer/loader’s dermal, inhalation, and combined MOEs were greater than the level of 

concern (MOE > 100) while wearing label-specified PPE and therefore not of concern to HED 

for this registration action. 

It is possible for agricultural workers to have post-application exposure to pesticide residues 

during the course of typical agricultural activities. For all short-term post-application activities 

in this registration action, MOEs were ≥ 100 and therefore not of concern. 

Recommendations for Tolerances and Registration

Pending submission of a revised Section B (see Section 10.0 under Directions for Use) and a 

revised Section F (see Section 10.0 under Proposed Tolerances), there are no residue chemistry

issues that would preclude granting conditional registration for the requested uses of the EC and 

SC formulations of difenoconazole on bulb vegetables, Brassica leafy

vegetables, citrus fruits, cucurbit vegetables, pistachios, tree nuts, and grapes; and, in 

consideration of the specific use proposals, for the requested uses of the EW formulation of 

difenoconazole on almonds, pistachios, Brassica leafy vegetables, and bulb onions or 

establishment of tolerances for residues of difenoconazole only in/on the following commodities:

Almond, hulls.......................................................................7.0 ppm
Page 7 of 69

Brassica, head and stem, subgroup 5A ...............................1.9 ppm

Brassica, leafy greens, subgroup 5B......................... 35 ppm

Citrus, dried pulp .................................................................2.0 ppm

Citrus, oil ...........................................................................25 ppm

Fruit, citrus, group 10...........................................................0.60 ppm

Grape....................................................................................4.0 ppm

Grape, raisin.........................................................................6.0 ppm 

Nut, tree, group 14 ...............................................................0.03 ppm

Onion, bulb, subgroup 3-07A ..............................................0.20 ppm

Onion, green, subgroup 3-07B.............................................6.0 ppm 

Pistachio...............................................................................0.03 ppm

Vegetable, cucurbit, group 9 ................................................0.70 ppm

HED cannot recommend in favor of granting conditional registration for the requested uses of the 

0.73 lb/gal MAI EW formulation (EPA Reg. No. 100-1317) on green onions, subgroup 3-07B; 

citrus fruits, group 10; cucurbit vegetables, group 9; and grape. Green onion, orange, cantaloupe, 

and grape field trial data are required to support these proposed uses of the 0.73 lb/gal MAI EW 

formulation (EPA Reg. No. 100-1317). Data are required reflecting the proposed maximum use 

rates and minimum PHIs in accordance with OPPTS 860.1500 guidelines.

Notes to PM:

(1) If not already addressed, corrections are needed to the existing tolerances listing under 40 

CFR §180.475(a)(1), as specified in the most recent revision of this section (Rev. 7/1/08). 

 The tolerances for wheat forage, grain, and straw, each at 0.1 ppm, were inadvertently

removed [when tolerances were established in conjunction with 6F7115 (73 FR 1508, 

1/9/08)] and should be reinstated. 

 The tolerance level for sugar beet (0.01 ppm) is in error and should be corrected to 0.30 

ppm.

(2) The recommended tolerance for grape (4.0 ppm) should replace the existing import tolerance 

for grape (0.10 ppm).

(3) According to HED’s Interim Guidance on Tolerance Expressions (5/27/09, S. Knizner), the 

tolerance expression for difenoconazole should be revised to state:

“Tolerances are established for residues of difenoconazole, including its metabolites and 

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

specified below is to be determined by measuring only difenoconazole [[1-[2-[2-chloro-4-(4-

chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole].”

(4) Regardless of the active ingredient, in general, HED continues to recommend caution in 

translating data from other formulations to support uses of an EW formulation. 

Environmental Justice Considerations
Page 8 of 69

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 

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.

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 studies, which comprise the 

Pesticide Handlers Exposure Database (PHED) and information from the Agricultural Re-Entry

Task Force (ARTF) and the Outdoor Residential Exposure Task Force (ORETF), have been 

determined to require a review of their ethical conduct, have received that review, and were 

considered appropriate (or ethically conducted) for use in risk assessments.

2.0 Ingredient Profile

2.1 Summary of Proposed Uses

(HED memo of B. Cropp-Kohlligian, 9/17/09, D361054 and 362648)

The subject end-use products are identified in Table 2.1a, and the proposed use directions are 

summarized in Table 2.1b.
Page 9 of 69

Table 2.1a. Summary of Proposed End-Use Products.

Trade Name Reg. No.

(File Symbol)

ai Content Formulation 

Type

Target Crops Relevant to 

PP#8F7482

Label 

Date

InspireTM 

Fungicide

100-1262 Difenoconazole

2.08 lb/gal (23.2%)

Emulsifiable 

concentrate

(EC)

Almonds, filberts, pecans, 

pistachios, and tree nuts; 

Brassica leafy vegetables; 

bulb vegetables; citrus fruits; 

cucurbit vegetables, and 

grapes

11/14/08

InspireTM XT 

Fungicide

100-1312 Difenoconazole

2.08 lb/gal (22.8%)

Propiconazole

2.08 lb/gal (22.8%)

EC Almonds, filberts, pecans, 

pistachios, and tree nuts; and 

bulb vegetables

11/14/08

Revus TopTM 

Fungicide

100-1278 Difenoconazole

2.08 lb/gal (21.9%)

Mandipropamid

2.08 lb/gal (21.9%)

EC Brassica leafy vegetables; 

bulb vegetables; cucurbit 

vegetables; and grapes

11/13/08

Quadris 

TopTM 

Fungicide

100-1313 Difenoconazole

1.05 lb/gal (11.4%)

Azoxystrobin

1.67 lb/gal (18.2%)

Suspension 

concentrate

(SC)

Almonds, filberts, pecans, 

pistachios, and tree nuts; 

Brassica leafy vegetables; 

bulb vegetables; citrus fruits; 

cucurbit vegetables, and 

grapes

11/14/08

Inspire 

SuperTM 

Fungicide

100-1317 Difenoconazole

0.73 lb/gal (8.4%)

Cyprodinil

2.09 lb/gal (24.1%)

Emulsion oil 

in water (EW)

Almonds and pistachios; 

Brassica leafy vegetables; 

bulb vegetables; citrus fruits; 

cucurbit vegetables, and 

grapes

11/14/08
Page 10 of 69

Table 2.1b. Summary of Directions for Use of Difenoconazole.

Applic. Timing, 

Type, and 

Equip.1

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 

Limitations1,2

Almonds; filberts (hazelnuts); pecans; pistachios; and tree nuts including: beech nut; Brazil nut; butternut; cashew, 

chestnut; chinquapin; hickory; macadamia; walnut, black; and walnut, English

Foliar,

Broadcast, 

Ground (≥15 

gal/A) or aerial 

(≥10 gal/A)

2.08 lb/gal 

EC

[100-1262]

0.08-

0.114

Not 

specified

(NS)

0.46 14 Apps. to begin: prior to disease 

onset (all), or at early bloom 

(blossom blight; almonds), or 

when green leaf tissue becomes 

visible (Botryosphaeria; 

pistachios). No more than 2 

consecutive apps. to be made 

before alternation with a 

different MOA fungicide. A 

14- to 21-day or 14-day (pecan) 

RTI is specified. 

2.08 lb/gal 

MAI EC

[100-1312]

NS 60

(all but 

pecan)

NS

(pecan)

As for 100-1262 except: for 

anthracnose in almonds, apps. 

to begin at bud break with a 7-

to 14-day RTI; for filberts, 

apps. to begin when green leaf 

tissue becomes visible; for 

pecans, app. after shuck split is 

prohibited. Grazing livestock 

in treated area or cutting treated 

cover crop for feed is 

prohibited.

1.05 lb/gal 

MAI SC

[100-1313]

0.08-

0.12

4 28

(almond)

14

(pistachio)

45

(all 

others)

As for 100-1262 except no 

treatment timing specified for 

Botyrosphaeria in pistachios.

0.73 lb/gal 

MAI EW

[100-1317]

0.07-

0.114

5 60 

(almond)

14

(pistachio)

As for 100-1262 except: label 

includes almonds and 

pistachios only; no treatment 

timing specified for blossom 

blight in almonds or for 

Botyrosphaeria in pistachios. 

Aerial app. restricted to CA 

only: 1 app., with additional 

apps. by ground equipment.
Page 11 of 69

Table 2.1b. Summary of Directions for Use of Difenoconazole.

Applic. Timing, 

Type, and 

Equip.1

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 

Limitations1,2

Brassica (Cole) Leafy Vegetables Subgroup: Broccoli; broccoli, Chinese (gai lon); broccoli raab (rapini); Brussels 

sprouts; cabbage; cabbage, Chinese (bok choy); cabbage, Chinese (napa); cabbage, Chinese mustard (gai choy); 

cauliflower; cavalo broccolo; collards; kale; kohlrabi; mizuna; mustard greens; mustard spinach; rape greens

Foliar,

Broadcast, 

Ground (≥15 

gal/A), aerial 

(≥5 gal/A), or 

chemigation

2.08 lb/gal 

EC

[100-1262]

0.08-

0.114

NS 0.46 1 Apps. to begin prior to disease 

onset. No more than 2 

consecutive apps. to be made 

before alternation with a 

different MOA fungicide. A 7-

to 10-day RTI is specified. 

2.08 lb/gal 

MAI EC

[100-1278]

0.09-

0.114

4

1.05 lb/gal 

MAI SC

[100-1313]

0.07-

0.12

4 0 As above except only 1 app. 

may be made before alternating 

to a different MOA (nonQol/Group 11) fungicide, , and 

a 7- to 14-day RTI is specified.

Foliar,

Broadcast, 

Ground (≥15 

gal/A)

0.73 lb/gal 

MAI EW

[100-1317]

0.08-

0.114

5 7 As above except application is 

limited to ground equipment.

Bulb Vegetables: Chive, fresh leaves; chive, Chinese, fresh leaves; daylily, bulb; elegans hosta; fritillaria, bulb; 

fritillaria, leaves; garlic, bulb; garlic, great-headed, bulb; garlic, serpent, bulb; kurrat; lady’s leek; leek; leek, wild; 

lily, bulb; onion, Beltsville bunching; onion, bulb; onion, Chinese, bulb; onion, fresh; onion, green; onion, 

macrostem; onion, pearl; onion, potato, bulb; onion, tree, tops; onion, Welsh, tops; shallot, bulb; shallot, fresh 

leaves; cultivars, varieties, and/or hybrids of these

Foliar,

Broadcast, 

Ground (≥15 

gal/A), aerial 

(≥5 gal/A), or 

chemigation

2.08 lb/gal 

EC

[100-1262]

0.08-

0.114

NS 0.34

(green 

onions)

0.46

(bulb 

onions)

7 Apps. to begin prior to disease 

onset. No more than 2 

consecutive apps. to be made 

before alternation with a

different MOA fungicide. A 7-

to 10-day RTI is specified. 

2.08 lb/gal 

MAI EC

[100-1312]

7

(green 

onion)

14

(bulb 

onion)

2.08 lb/gal 

MAI EC

[100-1278]

0.09-

0.114

4 7

1.05 lb/gal 

MAI SC

[100-1313]

0.07-

0.12

As above except only 1 app. 

may be made before alternating 

to a different MOA (nonQol/Group 11) fungicide, and a 

7- to 14-day RTI is specified.

Foliar,

Broadcast, 

Ground (≥15 

gal/A)

0.73 lb/gal 

MAI EW

[100-1317]

0.08-

0.114

5 As above except application is 

limited to ground equipment.
Page 12 of 69

Table 2.1b. Summary of Directions for Use of Difenoconazole.

Applic. Timing, 

Type, and 

Equip.1

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 

Limitations1,2

Citrus: Calamondin; citrus citron; citrus hybrids (includes chironja, tangelo, tangor); grapefruit; kumquat; lemon; 

lime; mandarin (tangerine); orange, sour; orange, sweet; pummelo; Satsuma mandarin

Foliar,

Broadcast, 

Ground (≥15 

gal/A) or aerial 

(≥10 gal/A)

2.08 lb/gal 

EC

[100-1262]

0.08-

0.125

NS 0.5 0 Apps. to begin prior to disease 

development and continue 

throughout the season following

resistance management 

guidelines. A 7- to 21-day RTI 

is specified. Use of an adjuvant 

is permitted; use of a 

horticultural spray oil is 

recommended for control of 

greasy spot. 

1.05 lb/gal 

MAI SC

[100-1313]

4

0.73 lb/gal 

MAI EW

[100-1317]

0.08-

0.114

5 As above except label specifies 

lemon and lime only. Aerial 

app. is restricted to CA only: 1 

app., with additional apps. by 

ground equipment.

Cucurbit Vegetables: Chayote (fruit); Chinese waxgourd (Chinese preserving melon); citron melon; cucumber; 

gherkin; gourd, edible (includes hyotan, cucuzza, hechima, Chinese okra); Momordica spp. (includes balsam apple, 

balsam pear, bitter melon, Chinese cucumber); muskmelon (includes cantaloupe); pumpkin; squash, summer; 

squash, winter (includes butternut squash, calabaza, hubbard squash, acorn squash, spaghetti squash); watermelon

Foliar,

Broadcast, 

Ground (≥15 

gal/A), aerial 

(≥5 gal/A), or 

chemigation

2.08 lb/gal 

EC

[100-1262]

0.08-

0.114

NS 0.46 0 Apps. to begin prior to disease 

onset. No more than 2 

consecutive apps. to be made 

before alternation with a 

different MOA fungicide. A 7-

to 10-day RTI is specified. 

2.08 lb/gal 

MAI EC

[100-1278]

0.09-

0.114

As above except only 1 app. 

may be made before alternating 

to a different MOA fungicide.

1.05 lb/gal 

MAI SC

[100-1313]

0.10-

0.12

4 1 Apps. to begin prior to disease 

onset or at 1- to 3-leaf stage (for 

belly rot). No more than 1 app. 

to be made before alternation 

with a different MOA fungicide.

A 7- to 14-day RTI is 

specified.

Foliar,

Broadcast, 

Ground (≥15 

gal/A)

0.73 lb/gal 

MAI EW

[100-1317]

0.114 5 1 As for 100-1262 except app. is 

limited to ground equipment.
Page 13 of 69

Table 2.1b. Summary of Directions for Use of Difenoconazole.

Applic. Timing, 

Type, and 

Equip.1

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 

Limitations1,2

Grapes

Foliar,

Broadcast, 

Ground (≥15 

gal/A) or aerial 

(≥10 gal/A)

2.08 lb/gal 

EC

[100-1262]

0.08-

0.114

NS 0.46 7 Apps. to begin: at bud break 

with a 10- to 21-day RTI (for 

powdery mildew); or at 

budbreak before shoots are 0.5” 

long, then when shoots are 5-6” 

long (Phomopsis); or when 

shoots are 1-3” long with a 10-

day RTI (black rot); or prior to 

disease onset with a 10- to 14-

day RTI (all other diseases). 

No more than 2 consecutive 

apps. to be made before 

alternation with a different 

MOA fungicide. 

2.08 lb/gal 

MAI EC

[100-1278]

0.09-

0.114

14

1.05 lb/gal 

MAI SC

[100-1313]

0.08-

0.12

4

0.73 lb/gal 

MAI EW

[100-1317]

0.08-

0.114

5 7 As above except aerial app is 

restricted to CA only: 1 app., 

with additional apps. by ground 

equipment.

1

 MOA = mode of action; RTI = retreatment interval.

For the 2.08 lb/gal MAI EC formulation with mandipropamid, use of a nonionic surfactant, crop oil concentrate, or 

blend is recommended for all proposed uses; use of adjuvants is not addressed on any other labels except for uses on 

citrus fruits.

For the 0.73 lb/gal MAI EW formulation with cyprodinil, the label includes the following statement: “In annual 

crops, where multiple crops can be grown per year (double/triple cropping), do not apply more than 1.3 lb ai per acre 

per year to an individual plot of land.” This appears to apply to cyprodinil.

2

 The labels contain the following general resistance management guidelines: Use of this product should conform to 

strategies established for the crop and use area; consult local or State agricultural authorities for strategies that are 

complementary to those in this label; resistance management strategies may include rotating and/or tank mixing with 

products having a different MOA or limiting the total number of applications per season. Do not apply to plants 

grown for transplanting purposes.

2.2 Structure and Nomenclature

The nomenclature of difenoconazole is summarized in Table 2.2a, and the physicochemical 

properties of difenoconazole are summarized in Table 2.2b. 
Page 14 of 69

Table 2.2a. Difenoconazole Nomenclature.

Chemical structure

O O

O

N N Cl

N

CH3

Cl

Common name Difenoconazole

Company experimental name CGA-169374

IUPAC name 1-({2-[2-chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-yl}methyl)-

1H-1,2,4-triazole

CAS name 1-[[2-[2-chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-yl]methyl]-

1H-1,2,4-triazole

CAS registry number 119446-68-3

End-use product (EP) InspireTM; 2.08 lb/gal EC; EPA Reg. No. 100-1262

Chemical structure of CGA205375 metabolite

O

Cl N N

N

OH Cl

Table 2.2b. Physicochemical Properties of Difenoconazole.

Parameter Value Reference

Melting point 78.6 oC DP#s 172067 and 178394, 10/26/92, R. 

Lascola pH 6-8 at 20 oC (saturated solution)

Density 1.37 g/cm3at 20 oC

Water solubility 3.3 ppm at 20 oC

Solvent solubility g/100 mL at 25 oC:

n-hexane: 0.5

1-octanol: 35

toluene: 77

acetone: 88

ethanol: 89

Vapor pressure 2.5 x 10-10 mm Hg at 25 oC

Dissociation constant, pKa <0

Octanol/water partition 

coefficient, Log(KOW)

4.2 at 25 oC

UV/visible absorption spectrum max at about 200 and 238 nm 

(in methanol at 26 oC)

PMRA Proposed Regulatory Decision 

Document on Difenoconazole, 4/14/99 

(PRDD99-01)

3.0 Hazard Characterization/Assessment
Page 15 of 69

(For detailed discussion, refer to HED memo of M. Sahafeyan, 11/09/07, D346591)

The toxicological database for difenoconazole is complete for the purpose of this risk 

assessment. However, a new data requirement for an Immunotoxicity study is required. 

3.1 Hazard and Dose-Response Characterization

For a complete list of studies considered, see Appendix 1 and 2 under Section 13.0 of this 

document.

3.1.1 Toxicological Effects and Dose-response

Difenoconazole possesses low acute toxicity by the oral, dermal and inhalation routes of 

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

In an acute neurotoxicity study in rats, reduced fore-limb grip strength was observed on day 1 in 

males and clinical signs of neurotoxicity in females at the limit dose of 2000 mg/kg. This effect 

in males is considered as transient since it was not observed at later observation points and 

toxicity in females was observed only at doses exceeding the limit dose. In a subchronic 

neurotoxicity study in rats decreased hind limb strength was observed only in males, which was 

considered as nonspecific in nature. 

It is not a developmental or reproductive toxicant. Chronic effects in the rat study are seen as 

cumulative decreases in body weight gains. Similarly, chronic feeding studies in mice showed 

decreased body-weight gains in male and female mice at termination. In mice, treatment-related 

non-neoplastic lesions were confined to the liver and were supported by clinical chemistry data at 

a level of 300 ppm (46 and 58 mg/kg/day for males and females, respectively). No systemic 

toxicity was observed at the limit dose in a 28-day dermal toxicity study in rats. A dermal 

absorption of 15.3% was observed through rat skin using an in vivo method.

Difenoconazole is not mutagenic, and no evidence of carcinogenicity was seen in rats. Evidence 

for carcinogenicity was seen in mice, where liver tumors were induced at doses which were 

considered to be excessively high for carcinogenicity testing. Liver tumors were observed in 

mice at 300 ppm and higher; however, based on excessive toxicity observed at the two highest 

doses of 2500 and 4500 ppm (females terminated after two weeks due to excessive toxicity

resulting in moribundity and death), the absence of tumors at two lower doses of 10 and 30 ppm 

and the absence of genotoxic effects, HED’s Cancer Peer Review Committee (CPRC) 

recommended for a cancer classification of C (possible human carcinogen). A margin-ofexposure (MOE) approach in risk assessment was advocated by the CPRC utilizing the noobservable-adverse-effects-level (NOAEL) of 30 ppm (4.7 and 5.6 mg/kg/day in males and 

females, respectively) and the lowest-observable-adverse-effects-level (LOAEL) of 300 ppm (46

and 58 mg/kg/day in males and females, respectively) from the mouse study using only those 

biological endpoints which were relevant to tumor development (i.e., hepatocellular hypertrophy, 

liver necrosis, fatty changes in the liver and bile stasis) (Memo, Jess Rowland and Esther Rinde, 

27-JUL-1994; Memo, PV Shah, 1-March-2007, HED Doc. No. 005453).
Page 16 of 69

The doses and toxicological endpoints selected for various exposure scenarios applicable to this 

risk assessment are summarized in Table 3.1.3a and Table 3.1.3b.

Table 3.1.3a. Summary of Toxicological Doses and Endpoints for Difenoconazole for Use in Dietary and NonOccupational Human-Health Risk Assessments. 

Exposure 

Scenario

Point of 

Departure

Uncertainty/FQPA 

Safety Factors

RfD, PAD, LOC for Risk 

Assessment

Study and Relevant 

Toxicological Effects

Acute Dietary 

(All 

populations)

NOAEL = 25

mg/kg

UFA = 10X

UFH = 10X

UFFQPA = 1X 

aRfD = aPAD = 0.25 

mg/kg/day

Acute Neurotoxicity Study 

in Rats

LOAEL= 200 mg/kg in 

males based on reduced 

fore-limb grip strength in 

males on day 1.

Chronic 

Dietary (All 

populations)

NOAEL = 

0.96

mg/kg/day

UFA = 10X

UFH = 10X

UFFQPA = 1X

cRfD = cPAD = 

0.01mg/kg/day

Combined chronic 

toxicity/carcinogenicity 

(rat; dietary) LOAEL = 

24.1/32.8 mg/kg/day (M/F) 

based on cumulative 

decreases in body-weight 

gains.

Incidental 

Oral

Short- and 

IntermediateTerm (1-30 

days and 1-6 

months)

NOAEL = 

1.25

mg/kg/day

UFA = 10X

UFH = 10X

UFFQPA = 1X 

Residential LOC for 

MOE<100

Reproduction and fertility 

effects (rat; dietary)

Offspring LOAEL = 12.5 

mg/kg/day based on 

reduction in body-weight of 

F1 males.

Dermal

Short- and 

IntermediateTerm (1-30 

days and 1-6 

months)

Oral NOAEL 

= 1.25

mg/kg/day

Dermal 

Absorption 

factor=15.3%

UFA = 10X

UFH = 10X

UFFQPA = 1X 

Residential LOC for 

MOE<100

Reproduction and fertility 

effects (rat; dietary)

Offspring LOAEL = 12.5 

mg/kg/day based on 

reduction in body-weight 

gain of F0 females prior to 

mating, gestation and 

lactation.

Dermal

Long-Term

(>6 months)

Oral NOAEL 

= 0.96

mg/kg/day

Dermal 

Absorption 

factor=15.3%

UFA = 10X

UFH = 10X

UFFQPA = 1X

Residential LOC for 

MOE<100

Combined chronic 

toxicity/carcinogenicity 

(rat; dietary) LOAEL = 

24.1/32.8 mg/kg/day (M/F) 

based on cumulative 

decreases in body-weight 

gains.

Inhalation

(Short- and 

Intermediateterm)

Oral NOAEL 

= 1.25

mg/kg/day

100% 

inhalation 

absorption 

assumed

UFA = 10X

UFH = 10X

UFFQPA = 1X 

Residential LOC for 

MOE<100

Reproduction and fertility 

effects (rat; dietary)

Offspring LOAEL = 12.5 

mg/kg/day based on 

reduction in body weight 

gain of F0 females prior to 

mating, gestation and 

lactation.

Inhalation

(Long- term)

Oral NOAEL 

= 0.96

UFA = 10X

UFH = 10X

Residential LOC for 

MOE<100

Combined chronic 

toxicity/carcinogenicity 
Page 17 of 69

Table 3.1.3a. Summary of Toxicological Doses and Endpoints for Difenoconazole for Use in Dietary and NonOccupational Human-Health Risk Assessments. 

Exposure 

Scenario

Point of 

Departure

Uncertainty/FQPA 

Safety Factors

RfD, PAD, LOC for Risk 

Assessment

Study and Relevant 

Toxicological Effects

mg/kg/day

100% 

inhalation 

absorption 

assumed

UFFQPA = 1X (rat; dietary) LOAEL = 

24.1/32.8 mg/kg/day (M/F) 

based on cumulative 

decreases in body weight 

gains.

Cancer (oral, 

dermal, 

inhalation)

Difenoconazole is classified as a Group C, possible human carcinogen with a non-linear (MOE) 

approach for human risk characterization (CPRC Document, 7/27/94, Memo, P. V. Shah dated 

March 3, 2007, HED Doc. No. 0054532).

Abbreviations: UF = uncertainty factor, UFA = extrapolation from animal to human (interspecies), UFH = potential 

variation in sensitivity among members of the human population (intraspecies), UFFQPA = FQPA Safety Factor, 

NOAEL = no-observed-adverse-effect level, LOAEL = lowest-observed-adverse-effect level, RfD = reference dose 

(a = acute, c = chronic), PAD = population-adjusted dose, MOE = margin of exposure, LOC = level of concern.

Table 3.1.3b. Summary of Toxicological Doses and Endpoints for Difenoconazole for Use in 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

Short- and 

IntermediateTerm (1-30 

days and 1-6 

months)

Oral NOAEL 

= 1.25

mg/kg/day

Dermal 

Absorption 

factor=15.3%

UFA = 10X

UFH = 10X

Occupational LOC for 

MOE<100

Reproduction and fertility 

effects (rat; dietary)

Offspring LOAEL = 12.5 

mg/kg/day based on 

reduction in body-weight 

gain of F0 females prior to 

mating, gestation and 

lactation.

Dermal

Long-Term

(>6 months)

Oral NOAEL 

= 0.96

mg/kg/day

Dermal 

Absorption 

factor=15.3%

UFA = 10X

UFH = 10X

Occupational LOC for 

MOE<100

Combined chronic 

toxicity/carcinogenicity 

(rat; dietary) LOAEL = 

24.1/32.8 mg/kg/day (M/F) 

based on cumulative 

decreases in body-weight 

gains.

Inhalation

(Short- and 

Intermediateterm)

Oral NOAEL 

= 1.25

mg/kg/day

100% 

inhalation 

absorption 

assumed

UFA = 10X

UFH = 10X

Occupational LOC for 

MOE<100

Reproduction and fertility 

effects (rat; dietary)

Offspring LOAEL = 12.5 

mg/kg/day based on 

reduction in body-weight 

gain of F0 females prior to 

mating, gestation and 

lactation.

Inhalation

(Long- term)

Oral NOAEL 

= 0.96

mg/kg/day

100% 

inhalation 

absorption 

assumed

UFA = 10X

UFH = 10X

Occupational LOC for 

MOE<100

Combined chronic 

toxicity/carcinogenicity 

(rat; dietary) LOAEL = 

24.1/32.8 mg/kg/day (M/F) 

based on cumulative 

decreases in body-weight 

gains.
Page 18 of 69

Table 3.1.3b. Summary of Toxicological Doses and Endpoints for Difenoconazole for Use in 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

Cancer (oral, 

dermal, 

inhalation)

Difenoconazole is classified as a Group C, possible human carcinogen with a non-linear (MOE) 

approach for human risk characterization (CPRC Document, 7/27/94, Memo, P. V. Shah dated 

March 3, 2007, HED Doc. No. 0054532).

Abbreviations: UF = uncertainty factor, UFA = extrapolation from animal to human (interspecies), UFH = potential 

variation in sensitivity among members of the human population (intraspecies), UFFQPA = FQPA Safety Factor, 

NOAEL = no-observed-adverse-effect level, LOAEL = lowest-observed-adverse-effect level, RfD = reference dose 

(a = acute, c = chronic), PAD = population-adjusted dose, MOE = margin of exposure, LOC = level of concern.

3.2 FQPA Considerations

3.2.1. Determination of Susceptibility

The Hazard Identification Assessment Review Committee (HIARC) determined that the 

available Agency Guideline studies indicated no increased susceptibility of rats or rabbits to in 

utero and/or postnatal exposure to difenoconazole. In the prenatal developmental toxicity studies 

in rats and rabbits and the two-generation reproduction study in rats, toxicity to the 

fetuses/offspring, when observed, occurred at equivalent or higher doses than in the 

maternal/parental animals. In the prenatal developmental toxicity study in rats, maternal toxicity

was manifested as decreased body weight gain and food consumption at the LOAEL of 85 

mg/kg/day; the NOAEL was 16 mg/kg/day. The developmental toxicity was manifested as 

alterations in fetal ossifications at 171 mg/kg/day; the developmental NOAEL was 85 mg/kg/day. 

In a developmental toxicity study in rabbits, maternal and developmental toxicity were seen at 

the same dose level (75 mg/kg/day). Maternal toxicity in rabbits were manifested as decreased in 

body weight gain and decreased in food consumption, while developmental toxicity was 

manifested as decreased fetal weight. In a 2-generation reproduction study in rats, there were 

decreases in maternal body weight gain and decreases in body weights of F1 males at the LOAEL 

of 12.5 mg/kg/day; the parental systemic and off spring toxicity NOAEL was 1.25 mg/kg/day. 

3.2.2. Adequacy of Toxicity Database

There are no data gaps for the assessment of the effects of difenoconazole following in utero 

and/or postnatal exposure. The acute and subchronic neurotoxicity studies in rats are available. 

In an acute neurotoxicity study in rats, reduced fore-limb grip strength was observed on day 1 in 

males. This effect is considered as transient since it was not observed at later observation points. 

In a subchronic neurotoxicity study in rats decreased hind limb strength was observed only in 

males, which was considered as nonspecific in nature. Difenoconazole exhibits some evidence 

of neurotoxicity in the database, but the effects are transient or occur at doses exceeding the limit 

dose. EPA concluded that difenoconazole is not a neurotoxic compound. Based on the toxicity

profile, and lack of neurotoxicity, a developmental neurotoxicity study in rats is not required.

3.2.3. Degree of Concern Analysis:
Page 19 of 69

Since there is no evidence of susceptibility, there is no concern for increased susceptibility due to 

exposure to difenoconazole.

3.2.4. FQPA Safety Factor Recommendation

The FQPA factor for increased susceptibility to infant and children is reduced to 1x for the 

following considerations:

1) toxicology data base for difenoconazole is complete; 

2) there is no indication of increased susceptibility of rats or rabbit fetuses to in utero and/or 

postnatal exposure in the developmental and reproductive toxicity data; 

3) there are no concerns for neurotoxicity;

4) developmental neurotoxicity study is not required;

5) there are no residual uncertainties in the toxicology database. 

3.3 Endocrine Disruption

EPA is required under the Federal Food Drug and Cosmetic Act (FFDCA), as amended by

FQPA, to develop a screening program to determine whether certain substances (including all 

pesticide active and other ingredients) "may have an effect in humans that is similar to an effect 

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

may designate." Following the recommendations of its Endocrine Disruptor Screening and 

Testing Advisory Committee (EDSTAC), EPA determined that there was scientific basis for 

including, as part of the program, the androgen and thyroid hormone systems, in addition to the 

estrogen hormone system. EPA also adopted EDSTAC’s recommendation that the Program 

include evaluations of potential effects in wildlife. For pesticide chemicals, EPA will use FIFRA 

and, to the extent that effects in wildlife may help determine whether a substance may have an 

effect in humans, FFDCA has authority to require the wildlife evaluations. As the science 

develops and resources allow, screening of additional hormone systems may be added to the 

Endocrine Disruptor Screening Program (EDSP).

When the appropriate screening and/or testing protocols being considered under the Agency’s 

EDSP have been developed, difenoconazole may be subjected to additional screening and/or 

testing to better characterize effects related to endocrine disruption.

4.0 Public Health and Pesticide Epidemiology Data

Not relevant since these are new uses.

5.0 Dietary Exposure/Risk Characterization

5.1 Pesticide Metabolism and Environmental Degradation
Page 20 of 69

5.1.1 Metabolism in Primary Crops

The nature of the residue in plants is understood based on acceptable plant metabolism studies 

reflecting foliar applications in canola, grape, potato, tomato, and wheat and seed treatment in 

wheat. Based on the results of available plant metabolism studies, the petitioner has proposed 

that difenoconazole is metabolized in plants by the hydroxylation of the phenyl ring and/or 

cleavage of the dioxolane ring followed by cleavage of the carbon-carbon bridge between the 

phenyl and triazole rings. The metabolic pathway appears to proceed by hydrolysis of the ketal 

to the ketone followed by reduction of the ketone (CGA-205374) to the alkanol (CGA 205375). 

CGA 205375 can be conjugated with sugars or the bridge linking the phenyl and triazole 

moieties is cleaved. HED concluded that the residue of concern for both tolerance enforcement 

and risk assessment for crops included in this petition is difenoconazole per se. The proposed 

metabolic pathway is illustrated in Appendix 5.

5.1.2 Metabolism in Rotational Crops

The nature of the residue in rotational crops is not adequately understood because previously

conducted studies did not reflect sufficiently high application rates, and/or insufficient 

characterization/identification of residues was achieved. An additional confined rotational crop 

study reflecting phenyl-ring labeling must be conducted at 1x the proposed maximum seasonal 

foliar application rate (0.46 lb ai/A). An acceptable limited field rotational crop study is 

available; these data will be reevaluated when the outstanding confined rotational crop study is 

received. In the meantime, the proposed rotational crop restrictions on the submitted labels are 

deemed appropriate.

5.1.3 Metabolism in Livestock

The nature of the residue in livestock is understood based on acceptable goat and hen metabolism 

studies. The data were originally evaluated in support of seed treatment uses only, and HED 

concluded that the residue of concern in livestock commodities was difenoconazole per se. 

When the first foliar uses of difenoconazole on crop commodities were proposed (DP# 340379), 

HED re-evaluated the livestock metabolism data and concluded that the residues of concern for 

both tolerance setting and risk assessment for livestock commodities are difenoconazole and 

metabolite CGA-205375.

5.1.4 Analytical Methodology

An adequate tolerance enforcement method, method AG-575B, is available for crop 

commodities. The method determines residues of difenoconazole per se in/on crop commodities 

by gas chromatography with nitrogen-phosphorus detection (GC/NPD). The method limits of 

quantitation (LOQs) are 0.01-0.05 ppm. A confirmatory GC method with mass-selective 

detection (MSD) is also available for crop commodities. Samples from the submitted the crop 

field trials and processing studies were analyzed for residues of difenoconazole using a high 
Page 21 of 69

performance liquid chromatography method with tandem mass spectrometry detection 

(LC/MS/MS), Syngenta REM 147.08, and for residue of the triazole metabolites TA, TAA, and 

1,2,4-T using Morse Laboratories LC/MS/MS method Meth-160, Revision #2. The methods 

were adequate for data collection based on acceptable concurrent method recoveries. The LOQ 

was 0.01 ppm for each analyte in each commodity.

An LC/MS/MS method, Syngenta REM 147.07 was previously submitted under PP#6F7115 

(DP# 340379, 8/9/07, W. Wassell and M. Sahafeyan) for the determination of residues of 

difenoconazole and CGA-205375 in livestock commodities. The method LOQs are 0.01 ppm for 

livestock tissues and 0.005 ppm for milk. HED tentatively concluded that the method would be 

suitable for enforcement purposes pending submission of the following: (1) additional 

information from the independent laboratory validation (ILV) of the method; (2) revision of the 

method to correct all references to “crop matrices”; (3) confirmatory analysis procedures for the 

method; and (4) successful Agency method validation. Under the current action, Syngenta has 

submitted the required method revision (REM 147.07b), and an acceptable confirmatory method 

for determination of CGA-205375, method REM 147.06, a high performance liquid 

chromatography method with ultraviolet detection (HPLC/UV). The previously established 

tolerance enforcement method for livestock commodities, GC/NPD method AG-544A, is 

suitable as a confirmatory method for residues of difenoconazole. In addition, the Analytical 

Chemistry Branch (ACB) has found method REM 147.07 to be adequate for tolerance 

enforcement without a laboratory trial. The requirement for additional information from the ILV 

remains outstanding. The revised method (REM 147.07b), along with confirmatory method 

REM 147.06 will be forwarded to FDA for inclusion in the Pesticide Analytical Method (PAM) 

Volume II. 

5.1.5 Environmental Degradation

In soil environment, difenoconazole is persistent and slightly mobile. Difenoconazole has low 

potential to reach ground water, except in soils of high sand and low organic matter content. It is 

likely to reach surface sources of drinking water via spray drift and runoff. In the aquatic 

environment its main route of dissipation is partitioning into the bottom sediment, and potentially

relatively fast to slow aqueous photolysis in clear water conditions. 

Major degradates include CGA 205375 which was found in lab accumulation in fish at 51-64% 

applied dose, and in aerobic soil at 14.8%, in aerobic aquatic at 11.6% and anaerobic aquatic at 

12.6% of the applied dose, and CGA 71019 (triazole) and CGA-142856 (TAA). Since triazole 

and TAA are common metabolites from a group of chemicals, they should be addressed 

separately. (See Appendix 4 for structures)

5.1.6 Comparative Metabolic Profile

Rat metabolism studies (MRID 42090028 through 31, and 42710013 through14) indicated that 

difenoconazole was rapidly adsorbed and mainly eliminated vis bile. Three major urinary
Page 22 of 69

metabolites were isolated and further identified as sulfate conjugates of CGA 205375, isomers of 

CGA 205375, and the hydroxyacetic metabolite of CGA 205375 . Further metabolism formed 

free triazoles. The proposed metabolic pathway in rats is presented in Appendix 4.

Comparisons of the metabolisms indicated that the metabolic pathways in plants, livestock, rats, 

and the environment are very similar or identical, with the formation of CGA 205375 and then 

further metabolism to form free triazole metabolites.

5.1.7 Toxicity Profile of Major Metabolites and Degradates

Other than the triazole metabolites, no toxicity information is available on the CGA 205375 

metabolite. Based on structural similarity, it is assumed that the CGA 205375 shares the same 

toxicity as the parent.

5.1.8 Pesticide Metabolites and Degradates of Concern

The most recent MARC visit for difenoconazole is in 1994. In 2007, HED reviewers reevaluated the plant and livestock metabolism studies based on new data submitted in conjunction 

with the new uses. It was concluded that the residue of concern for both tolerance enforcement 

and risk assessment for currently registered crops is difenoconazole per se. For livestock, the 

residues of concern for both tolerance setting and risk assessment for livestock commodities are 

difenoconazole and its metabolite CGA-205375. With the subject petition, HED determined 

that previous conclusions on plants and livestock stand. As for drinking water assessment, HED 

tentatively concludes that the residues of concern are parent and CGA 205375. For future new 

uses of difenoconazole, HED recommends that a revisit to the HED ROCKS Committee is 

needed.

5.1.9 Drinking Water Residue Profile

Drinking water assessment was conducted for parent compound only. The fate and transport 

database for difenoconazole were sufficient to conduct the drinking water assessment. The Tier 

II drinking water assessment was performed using PRZM (v3.12.2; May 12, 2005)/EXAMS (v. 

2.98.04.06; April 25, 2005) modeling with index reservoir (IR) scenarios and percent cropped 

area (PCA) adjustment factors. The assessment for the proposed uses was based on 

difenoconazole uses on citrus fruits and grapes. These are major crops, with difenoconazole 

maximum application rate to citrus fruits being the highest of all agricultural uses, and grapes 

being the second highest. An initial simulation analysis showed that grapes would produce the 

highest EDWCs of all proposed crop uses with the same maximum application rate of 0.46 lb 

ai/A hence grapes and citrus fruits were modeled. 

Florida and California citrus fruit scenarios were modeled for citrus fruits, and New York and 

California grapes scenarios were modeled for grapes. Default PCA of 0.87 was used for surface 

water models. Among all the registered and proposed new uses, the highest estimated drinking 
Page 23 of 69

water concentrations (EDWCs) from surface water sources were derived for aerial applications of 

difenoconazole to New York grapes at the maximum annual application rate of 0.46 lb ai/acre. 

The recommended peak and mean estimated drinking water concentrations (EDWCs) for the 

human health risk assessment are provided in Table 1. These estimates exceed the previously

EDWCs from 2007 drinking water assessment (D333319).

Table 1. PCA Adjusted Difenoconazole EDWCs from Surface Water Sources.

Scenario

Application 

Type/Annual 

Fungicide 

Application Rate

(lb ai/A) )

Estimated Drinking Water Concentrations (μg/L)a

1 in 10 year annual 

peak

1 in 10 year 

annual mean

36 year annual 

mean

NY Grape

aerially applied

0.114 x 4 = 0.46 15.8 10.4 7.62

a EXAMS EECs multiplied by 0.87, a default PCA factor. 

The highest SCI-GROW estimated drinking water concentration of difenoconazole from shallow 

ground water sources is 1.23 x 10-2μg/L derived for the maximum proposed application rate to 

citrus fruit (0.50 lb ai/A), i.e. agricultural uses. Based on the previous drinking water assessment, 

this estimate is lower than an estimate for non-agricultural uses 1.28 x 10-2μg/L, obtained for the 

maximum application rate for ornamentals (0.52 lb ai/A; D333319). These concentrations can be 

considered as both the acute and chronic values. 

Currently, no data are available indicating whether water treatment process will increase 

dissipation and/or will form degradation products that may be more toxic than the parent.

HED believes that future drinking water assessment should be conducted for parent and 

degradate CGA 205375. 

5.1.10 Food Residue Profile

(HED memo of B. Cropp-Kohlligian, 9/17/09, D361054 and 362648) 

HED has examined the residue chemistry database for difenoconazole and has identified several 

residue chemistry data deficiencies. However, no major residue deficiencies will prevent the 

establishment of permanent tolerances for the proposed uses. For details on data deficiencies, 

please see Section 10.0.

The nature of the residue in plants is understood based on acceptable plant metabolism studies 

reflecting foliar applications in canola, grape, potato, tomato, and wheat, and seed treatment in 

wheat. HED concludes that the residue of concern for both tolerance enforcement and risk 

assessment for crops included in this petition is difenoconazole per se. The nature of the residue 

in livestock is understood based on acceptable goat and hen metabolism studies. The residues of 

concern for both tolerance setting and risk assessment for livestock commodities are 

difenoconazole per se and its metabolite CGA-205375.

An adequate tolerance enforcement method, method AG-575B, is available for crop 
Page 24 of 69

commodities. An LC/MS/MS method, Syngenta REM 147.07 was previously submitted under 

PP#6F7115 (DP# 340379, 8/9/07, W. Wassell and M. Sahafeyan) for the determination of 

residues of difenoconazole and CGA-205375 in livestock commodities. The method LOQs are 

0.01 ppm for livestock tissues and 0.005 ppm for milk. HED tentatively concluded that the 

method would be suitable for enforcement purposes pending submission of the following: (1) 

additional information from the independent laboratory validation (ILV) of the method; (2) 

revision of the method to correct all references to “crop matrices”; (3) confirmatory analysis 

procedures for the method; and (4) successful Agency method validation. 

Supporting storage stability data were not provided in the subject submissions; however, 

available storage stability data for residues of difenoconazole per se in/on various raw 

agricultural crop and processed commodities are deemed adequate to support the storage 

conditions and durations of samples from the crop field trial and processing studies reviewed 

herein. 

Adequate feeding study data have been submitted previously for difenoconazole in cattle and 

poultry commodities; however, the requirement for supporting storage stability data for the 

feeding studies remains outstanding. No changes to the existing livestock tolerances are needed 

to support the proposed uses. 

Adequate field trial data have been submitted to support the proposed uses of the EC formulation 

of difenoconazole on bulb vegetables, Brassica leafy vegetables, cucurbit vegetables, citrus fruits, 

pistachios, tree nuts, and grapes. Based on previously submitted side-by-side field trial data for 

leaf lettuce, mustard greens, and tomatoes comparing residues of difenoconazole per se resulting 

from use of a 2.08 lb/gal EC formulation with that of a 2.08 lb/gal SC formulation (DP# 354013, 

3/20/09, B. Cropp-Kohlligian), and in consideration of the specific use proposals for the SC 

formulations, the submitted field trial data representing an EC formulation of difenoconazole are 

also deemed adequate to support the proposed uses of the SC formulation of difenoconazole on 

these same crops. In consideration of the specific use proposals for the EW formulation, the 

submitted field trial data representing an EC formulation of difenoconazole are also deemed 

adequate to support the proposed uses of the EW formulation of difenoconazole on almonds and 

pistachios, Brassica leafy vegetables, and bulb onions, subgroup 3-07A. The submitted data will 

support the proposed tolerances for almond hulls; Brassica, head and stem, subgroup 5A; citrus 

fruit, group 10; grape; tree nut, group 14, and pistachio; and cucurbit vegetables. The proposed 

tolerance for Brassica, leafy greens, subgroup 5B is too low; a tolerance of 35 ppm is appropriate. 

For bulb onions, subgroup 3-07A and green onions, subgroup 3-07B, the data will support 

respective tolerances of 0.20 and 6.0 ppm.

The field trial data submitted to support the proposed uses of the EC formulation of 

difenoconazole on green onions, citrus fruits, cucurbit vegetables, and grapes are not deemed 

adequate to support the proposed uses of the EW formulation of difenoconazole on these same 

crops. Syngenta has previously submitted side-by-side field trial data for leaf lettuce, mustard 

greens, and tomatoes comparing residues of difenoconazole per se resulting from use of a 2.08 

lb/gal EC formulation with a 0.73 lb/gal EW formulation (DP# 354013, 3/20/09, B. CroppKohlligian). Given the limited scope and nature of these side-by-side data, HED has been 
Page 25 of 69

reluctant to draw too many conclusions from these data out of context. Collectively, these sideby-side field trial data, which represent multiple late-season, foliar applications and 0-7 day

PHIs, indicate the potential for significantly higher residue levels of difenoconazole per se in/on 

field crops from the use of the EW formulation when compared to the same use of an EC 

formulation. The highest average field trial (HAFT) residue levels from the side-by-side field 

trials were 28-54% higher for the EW formulation than for the EC formulation; mean values 

were also higher for the EW formulation than for the EC formulation. Hence, HED concludes 

that these side-by-side field trial data indicate that data for the EC formulation are not adequate 

to support the proposed uses of the EW formulations on green onions, citrus fruits, cucurbit 

vegetables, and grapes. Green onion, orange, cantaloupe, and grape field trial data are required 

to support the proposed uses of the 0.73 lb/gal MAI EW formulation (EPA Reg. No. 100-1317) 

on green onions, subgroup 3-07B; citrus fruits, group 10; cucurbit vegetables, group 9; and grape. 

Data are required reflecting the proposed maximum use rates and minimum PHIs in accordance 

with OPPTS 860.1500 guidelines. 

Adequate processing data for citrus and grape have been submitted to support the proposed uses 

on citrus fruits and grapes. The submitted data indicate that residues of difenoconazole do not 

concentrate in orange or grape juice, but do concentrate in orange dried pulp, orange oil and 

raisins. The processing data indicate that the proposed tolerances for processed commodities are 

too high; tolerances of 2.0 ppm for citrus dried pulp, 25 ppm for citrus oil, and 6.0 ppm for raisin 

would be appropriate.

The nature of the residue in rotational crops is not adequately understood. An additional 

confined rotational crop study reflecting phenyl-ring labeling must be conducted at 1x the 

proposed maximum seasonal foliar application rate (0.46 lb ai/A). An acceptable limited field 

rotational crop study is available; these data will be reevaluated when the outstanding confined 

rotational crop study is received. In the meantime, the proposed rotational crop restrictions on 

the submitted labels are deemed appropriate.

The tolerance spreadsheet in the Agency’s Guidance for Setting Pesticide Tolerances Based on 

Field Trial Data was utilized for determining appropriate tolerance levels for all raw agricultural 

commodities, groups, or subgroups listed in Table 12.0.

5.1.11 International Residue Limits

Codex Maximum Residue Limits (MRLs) for residues of difenoconazole per se have been 

established at 0.3 ppm for leek, 0.5 ppm for broccoli, 0.2 ppm for Brussels sprouts, 0.2 ppm for 

cabbage, 0.2 ppm for cauliflower, and 0.1 ppm for grape. Canadian and Mexican MRLs have 

been established for difenoconazole; however, no MRLs have been established for the requested 

crops. Based on the submitted field trial data, harmonization with established Codex MRLs is 

not possible because the MRLs for Brassica vegetables, leek, and grape are too low.

5.2 Dietary Exposure and Risk

(HED memo of T. Morton, 09/22/09, D367383)
Page 26 of 69

Residue Data used for Acute and Chronic Assessments:

The acute analysis assumed tolerance-level residues and 100% CT for all the registered and 

proposed crops. Tolerance-level residues were also assumed for all livestock tissues in this 

assessment. The chronic analysis assumed tolerance-level residues for some commodities, field 

trial residues for the majority of commodities, and 100 % CT. HED SOP 2000.1 Guidance for 

Translation of Field Trial Data from Representative Commodities in the Crop Group Regulation 

to Other Commodities in Each Crop Group/Subgroup dated 9/12/2000 was used in translating to 

other commodities in the crop group. Experimental processing factors were used for apple juice 

(0.04x), grape juice (0.2x), citrus juices (0.1x), potato chips (0.5x), potato granules/flakes (0.5x), 

raisin (3.5x chronic only), sugar beet molasses (0.6x), sugar beet refined sugar (0.6x), tomato 

paste (1.6x), and tomato puree (0.5x); DEEM (ver. 7.81) default processing factors were 

assumed for other processed commodities.

The estimated drinking water residues for 1-in-10 year annual peak (15.8μg/L) was used for the 

acute run, while 1-in-10 year annual mean (10.4 μg/L) was used for chronic. HED notes that 

degradate CGA 205375 was not included in the drinking water assessment; however, the relative 

amount of CGA 205375 is not significant in comparison to the parent.

DEEM-FCIDTM Program and Consumption Information

Difenoconazole acute and chronic dietary exposure assessments were conducted using the 

DEEM-FCID (ver. 2.03), which incorporates consumption data from USDA’s CSFII (1994-

1996 and 1998). The 1994-96, 98 data are based on the reported consumption of more than 

20,000 individuals over two non-consecutive survey days. Foods “as consumed” (e.g., apple pie) 

are linked to EPA-defined food commodities (e.g., apples, peeled fruit - cooked; fresh or N/S; 

baked; or wheat flour - cooked; fresh or N/S, baked) using publicly available recipe translation 

files developed jointly by USDA/ARS and EPA. For chronic exposure assessment, consumption 

data are averaged for the entire U.S. population and within population subgroups, but for acute 

exposure assessment are retained as individual consumption events. Based on analysis of the 

1994-96, 98 CSFII consumption data, which took into account dietary patterns and survey

respondents, HED concluded that it is most appropriate to report risk for the following 

population subgroups: the general U.S. population, all infants (<1 year old), children 1-2, 

children 3-5, children 6-12, youth 13-19, adults 20-49, females 13-49, and adults 50+ years old.

Results and Discussion

The resulting acute food exposure estimates were less than HED’s level of concern (<100% 

aPAD) at the 95th percentile of the exposure distribution for general US population (7% aPAD) 

and all population sub-groups; the most highly exposed population subgroup was Children 1-2 

years old population sub-group with 16% aPAD. The resulting chronic food exposure estimates 

were less than HED’s level of concern (<100% cPAD) for general U.S. population (17% cPAD) 

and all population sub-groups; the most highly exposed population subgroup was children 1-2 

years old with 44% cPAD. A cancer dietary assessment was not conducted for difenoconazole 

because the cancer NOAEL is higher than the chronic RfD; therefore, the chronic dietary risk 
Page 27 of 69

estimate is more protective.

Table 5.2a. Summary of Acute Dietary Exposure and Risk for Difenoconazole at the 95th Percentile. 

Population Subgroup aPAD (mg/kg/day) Exposure (mg/kg/day) %aPAD

General U.S. 

Population

0.25

0.017715

7

All Infants (< 1 year 

old)

0.025066

10

Children 1-2 years old 0.039605

16

Children 3-5 years old 0.031735

13

Children 6-12 years old 0.017972

7

Youth 13-19 years old

0.008802 4

Adults 20-49 years old 0.013060

5

Adults 50+ years old 0.017260

7

Females 13-49 years 

old 

0.013242

5

The bolded %aPAD is the highest.

Table 5.2b. Summary of Chronic Dietary Exposure and Risk for Difenoconazole. 

Population Subgroup cPAD (mg/kg/day) Exposure (mg/kg/day) %cPAD

General U.S. 

Population

0.01

0.001694

17

All Infants (< 1 year 

old)

0.002403

24

Children 1-2 years old 0.004440

44

Children 3-5 years old 0.003593

36

Children 6-12 years old 0.002041

20

Youth 13-19 years old 0.001360

14
Page 28 of 69

Table 5.2b. Summary of Chronic Dietary Exposure and Risk for Difenoconazole. 

Population Subgroup cPAD (mg/kg/day) Exposure (mg/kg/day) %cPAD

Adults 20-49 years old 0.001362

14

Adults 50+ years old 0.001538

15

Females 13-49 years 

old 

0.001389

14

The bolded %cPAD is the highest.

 
Page 29 of 69

6.0 Residential (Non-Occupational) Exposure/Risk Characterization

(HED memo of M. Sahafeyan, 11/09/07, D346591)

6.1 Residential Handler Exposure and Risk Characterization

No new residential uses are being requested at this time. However, adults and adolescents may

be exposed to difenoconazole from its currently registered use on ornamentals. These risks have 

been previously assessed. Below are the results from HED’s previous assessment:

HED believes residential pesticide handlers will be exposed to short-term duration (1 - 30 days) 

only. The dermal and inhalation (short-term) residential exposure was assessed for 

"homeowners" mixer/loader/applicator wearing short pants and short-sleeved shirts as well as 

shoes plus socks using garden hose-end sprayer, “pump-up” compressed air sprayer, and 

backpack sprayer. A MOE of 100 is adequate to protect residential pesticide handlers from 

exposures to difenoconazole. MOEs are >100; therefore are not of concern. A summary of these 

exposures and risks is presented in Table 6.1.

Table 6.1 Summary of Exposure & Risk for Homeowners Applying Difenoconazole.

Unit Exposure1

mg ai/lb handled

Applic. Rate2

lb ai/unit

Units Treated3 Avg. Daily Exposure4

mg ai/kg bw/day

Short-term

MOE5

Mixer/Loader/Applicator Using Garden Hose-end Sprayer

Dermal:

SS&SP 11 

Inhal. 0.017

0.13 lb ai/A

0.5 A/day

Dermal:

shrtsl&pants 0.00156

Inhal. 0.0000158

790

Mixer/Loader/Applicator Using "Pump-Up" Compressed Air Sprayer

Dermal:

SS&SP 38 

Inhal 0.0027

0.13 lb ai/A

0.5 A/day

Dermal:

shrtsl&pants 0.00539

Inhal. 0.0000025

230

Mixer/Loader/Applicator Using Backpack Sprayer

Dermal:

SS&SP 5.1 

Inhal. 0.03

0.13 lb ai/A

0.5 A/day

Dermal:

shrtslv&pants 0.000725

Inhal. 0.000028

1,700

1. Unit Exposures are taken from “PHED SURROGATE EXPOSURE GUIDE”, Estimates of Worker Exposure from The Pesticide Handler 

Exposure Database Version 1.1, August 1998. Inhal. = Inhalation. Units = mg a.i./pound of active ingredient handled. Unit exposures are also 

taken from ORETF studies OMA 004,OMA006 and from the Draft Residential SOPs, DECEMBER 1997. SS & SP = short sleeved shirt and short 

pants. LS & LP = long sleeved shirt and long pants.

2. Applic. Rate. = Taken from the draft Inspire®label.

3. Units Treated are taken the residential SOPs. 

4. Average Daily Dose (ADD) = Unit Exposure * Applic. Rate * Units Treated * absorption factor (15.3 % for dermal)  Body Weight (70 kg). 

5. NOAEL = No Observable Adverse Effect Level (1.25 mg a.i./kg bw/day for short-term and intermediate-term dermal and inhalation).

6. MOE = Margin of Exposure = No Observable Adverse Effect Level (NOAEL)  ADD. ADD = dermal + inhalation.

With respect to residential post-application exposures, current HED policy (see ExpoSAC 

minutes from 8/19/99 and 10/11/01) specifies that no significant post-application exposure 

is anticipated from ornamentals, either by residents or professional applicators; therefore, 

no residential post-application assessment was conducted.
Page 30 of 69

7.0 Aggregate Risk Assessments and 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 & Chronic Aggregate Risk

Acute and chronic aggregate exposures include food plus drinking water exposures. As 

demonstrated under Section 5.2. Acute and chronic aggregate risks are not of concern.

7.2 Short- and Intermediate-Term Aggregate Risk

Short-Term Aggregate Risk Assessment: Since a common endpoint has been identified for 

assessment of short-term oral, dermal, and inhalation exposures (changes in body weights and 

body-weight gains) the short-term aggregate risk assessment considered exposure from food, 

water, and residential sources. Since the doses corresponding to the identified oral, dermal, and 

inhalation endpoints were different but the level of concern for all three routes of exposure are 

identical, the short-term aggregate exposures were calculated using the 1MOE approach. HED 

combines chronic dietary (food and water) exposure estimates with residential exposure estimates 

when conducting short-term aggregate risk assessments. Short-term exposure has been defined as

from 1- 30 days and HED has concluded that chronic dietary exposure estimates will more 

accurately reflect actual dietary exposure over these time periods than will high-end acute-dietary

exposures. The proposed residential scenarios result in exposure to only adults. Therefore, shortterm aggregate assessments were not conducted for infants and children. Table 7.2 is a summary

of the short-term aggregate exposures and risk estimates. Since the aggregate MOEs are ≥180, 

short-term aggregate exposure to difenoconazole is not of concern. 

Table 7.2. Short-Term Aggregate Risk Calculations for Handlers

Population

Target 

Aggregate

MOE1

dietary 

MOE2

dermal + inhalation 

MOE3

agg. MOE

(dietary and residential)4

Youth 13-19 years old

100

920

230

180

Adults 20-49 years old 920 180

Adults 50+ years old 800 180

Females 13-49 years old 900 180

1

total uncertainty factor for all routes of exposure is 100x; therefore, the target MOE is 100.

2

dietary MOE = short-term incidental oral NOAEL  chronic dietary exposure.

3

dermal MOE = short-term dermal NOAEL (dermal + inhalation residential exposure) (see text).

4

aggregate MOE (dietary and residential) = 1((1MOEdietary) + (1MOEdermal) + (1MOEinhalation)).
Page 31 of 69

8.0 Cumulative Risk Characterization/Assessment

Difenoconazole is a member of the triazole-containing class of pesticides. Although conazoles 

act similarly in plants (fungi) by inhibiting ergosterol biosynthesis, there is not necessarily a 

relationship between their pesticidal activity and their mechanism of toxicity in mammals. 

Structural similarities do not constitute a common mechanism of toxicity. Evidence is needed to 

establish that the chemicals operate by the same, or essentially the same, sequence of major 

biochemical events (EPA, 2002). In conazoles, however, a variable pattern of toxicological 

responses is found. Some are hepatotoxic and hepatocarcinogenic in mice. Some induce thyroid 

tumors in rats. Some induce developmental, reproductive, and neurological effects in rodents. 

Furthermore, the conazoles produce a diverse range of biochemical events including altered 

cholesterol levels, stress responses, and altered DNA methylation. It is not clearly understood 

whether these biochemical events are directly connected to their toxicological outcomes. Thus, 

there is currently no evidence to indicate that conazoles share common mechanisms of toxicity

and EPA is not following a cumulative risk approach based on a common mechanism of toxicity

for the conazoles. For information regarding EPA’s procedures for cumulating effects from 

substances found to have a common mechanism of toxicity, see EPA’s website at 

http://www.epa.gov/pesticides/cumulative.

Difenoconazole is a triazole-derived pesticide. This class of compounds can form the common 

metabolite 1,2,4-triazole and two triazole conjugates (triazolylalanine and triazolylacetic acid). 

To support existing tolerances and to establish new tolerances for triazole-derivative pesticides, 

including difenoconazole, U.S. EPA conducted a human health risk assessment for exposure to 

1,2,4-triazole, triazolylalanine, and triazolylacetic acid resulting from the use of all current and 

pending uses of any triazole-derived fungicide. The risk assessment is a highly conservative, 

screening-level evaluation in terms of hazards associated with common metabolites (e.g., use of a 

maximum combination of uncertainty factors) and potential dietary and non-dietary exposures 

(i.e., high end estimates of both dietary and non-dietary exposures). In addition, the Agency

retained the additional 10X FQPA safety factor for the protection of infants and children. The 

assessment includes evaluations of risks for various subgroups, including those comprised of 

infants and children. The Agency’s complete risk assessment is found in the propiconazole 

reregistration docket at http://www.regulations.gov, Docket Identification (ID) Number EPAHQ-OPP-2005-0497.

9.0 Occupational Exposure/Risk Pathway

(HED memo of J. Miller, 09/14/09, D361054) 

9.1 Occupational Handler Exposure and Risk
Page 32 of 69

Handler Exposure 

The proposed uses associated with this action are for the use of difenoconazole (InspireTM 

Fungicide: EPA Reg. No. 100-1262) on Brassica leafy, bulb, and cucurbit vegetables, Citrus 

fruits, Grapes, Pistachios, and Tree Nuts. For this registration action, applications using aerial, 

ground, chemigation, and airblast equipment are allowed. 

Based on the number of seasonal applications indicated on this product label, and information 

provided by the registrant, handler exposures are expected to be short-term in duration. The 

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

following exposure scenarios:

 Open Mixing/Loading: Groundboom, Aerial, Chemigation, and Airblast; (EmulsifiableConcentrate formulation to Brassica leafy, bulb, and cucurbit vegetables, Citrus fruits, 

Grapes, Pistachios, and Tree Nuts).

 Open Mixing/Loading/Applying: Groundboom (Emulsifiable-Concentrate formulation to 

Brassica leafy, bulb, and cucurbit vegetables, Citrus fruits, Grapes, Pistachios, and Tree 

Nuts).

 Applying: Groundboom, Aerial, Chemigation, Airblast; (Emulsifiable-Concentrate 

formulation to Brassica leafy, bulb, and cucurbit vegetables, Citrus fruits, Grapes, 

Pistachios, and Tree Nuts).

No chemical-specific handler exposure data were submitted in support of this registration. It is 

the policy of the HED to use data from the Pesticide Handlers Exposure Database (PHED) 

Version 1.1 as presented in PHED Surrogate Exposure Guide (8/98) to assess handler exposures 

for regulatory actions when chemical-specific monitoring data are not available (HED Science 

Advisory Council for Exposure Standard Operating Procedure #7, dated 1/28/99). 

The results of the occupational exposure and risk assessment indicate that risks are not of 

concern (MOE ≥100) while wearing label-specified PPE. 

Data and Assumptions for Handler Exposure Scenarios

Unit Exposures:

 Chemical-specific data for assessing exposure during pesticide handling activities were 

not submitted to the Agency in support of this Section 3 application. It is HED policy to 

use data from the Pesticide Handlers Exposure Database (PHED) Version 1.1 to assess 

handler exposures for regulatory actions when chemical-specific data are not available 

(HED Science Advisory Council for Exposure, SOP Number .007, January 1999).

Area Treated:
Page 33 of 69

 The treatable acreage for the crops listed in table 1, varied according to the broadcast 

equipment used. Please see [Appendix A: Occupational-Agricultural Handler], for 

details. Note: acreage taken from: (HED Exposure Science Advisory Committee SOP 

Number 9.1).

Application Rate:

 (InspireTM Fungicide: EPA Reg. No. 100-1262)

The proposed product (InspireTM Fungicide: EPA Reg. No. 100-1262) is an emulsifiable 

concentrate (EC) containing 23.2% active ingredient. This formulation is distributed utilizing 

ground boom, aerial, broadcast and chemigation equipment. The application rates for all 

distribution equipment range from a minimum of 0.07 pounds per acre per application to a 

maximum of 0.114 pounds per acre per application. 

Exposure Duration:

 It is unlikely that pesticide handlers would be exposed continuously for 30 days or more. 

However, because the short-term and intermediate-term toxicological endpoints are the 

same (1.25 mg/kg bw/day), the assessment of short-term exposure and risk is adequate to 

describe risk from an intermediate-term exposure should that occur. MOEs for the shortterm scenarios have been estimated within. 

Body Weight:

 The average adult body weight of 70 kg was used for estimating exposure and risk. 

Handler Exposure Calculations

 

Handler risks were calculated using the Margin of Exposure (MOE) which is a ratio of the 

calculated daily dose to the NOAEL of concern. Daily dose values are calculated using relevant 

application parameters (i.e., rate and area treated) along with unit exposures. Exposures are then 

adjusted for body weight and absorption factors as appropriate to calculate dose levels.

Daily Exposure: The daily exposures were calculated as described below. 

 Daily exposure = (Unit exposure x application rate x Daily Area Treated)

Where:

Daily Exposure = Amount (mg ai/day) deposited on the surface of the 

Skin that is available for dermal absorption or amount 

inhaled that is available for inhalation absorption;

Unit Exposure = Unit exposures (mg ai/lb ai) derived from August 1998 

PHED data, or other appropriate data;

Application Rate = lbs ai per acre;
Page 34 of 69

Daily Area Treated = acres per day

Daily Dose: The daily dose (inhalation or dermal) was calculated by adjusting the daily dermal 

and inhalation exposure values by body weight and accounting for dermal or inhalation 

absorption. For adult handlers using acetochlor, an average body weight of 70 kg was 

used.

 Daily Dose = (Daily exposure x absorption factor)/ Bodyweight

Where:

Daily Dose = Absorbed dose (mg ai./kg body weight/day);

Daily Exposure = Amount (mg ai/day) deposited on the surface of the 

skin or inhaled;

Absorption Factor = 100% for inhalation , 15.3% for dermal

Body Weight = 70 kg 

Margins of Exposure: The daily doses were then compared to the NOAELs to assess the risk as 

an MOE. The MOEs were calculated using the formula below:

 MOE = NOAEL/Dose

Where:

MOE = Margin of Exposure (unit less)

Dose = mg/kg/day

NOAEL = No Observed Adverse Effects Level (mg/kg/day)

Handler Exposure Summary

 

Exposure and risk assumptions and MOEs for occupational handlers (Agricultural use) are 

summarized in Table 9.1.
Page 35 of 69

Note:

1 Handler Exposure Database Version 1.1, Surrogated Exposure guide August 1998 Inhal. = Inhalation. Units = mg 

a.i./pound of active ingredient handled. 

 2. Appl. Rate. = Taken from product labeling. 

3. Units Treated are taken from “Standard Values for Daily Acres Treated in Agriculture”; ExpoSAC SOP No. 9.1. 

Revised 

 4. Average Daily Dose (ADE) = Unit Exposure * Applic. Rate * Units Treated *DA  70 kg Body Weight

 5. MOE = Margin of Exposure = NOAEL  ADE. NOAEL = 1.25 mg/kg bw/day

 6. (EC) = Emulsifiable Concentrate

 

7. BL = Baseline (single layer clothing with no gloves)

Table 9.1: Summary of Exposure & Risk to Occupational Handlers 

Unit Exposure1

Appl. 

Rate2

lb ai/unit

Units 

Treated3

Avg. Daily 

Exposure4

mg ai/kg bw/day

Baseline + Gloves

MOE5

Dermal

mg ai/lb handled

Inhal.

μg ai/lb 

handled

Dermal + Inhalation 

 

BL7 BL/Gloves BL7 BL/Gloves

Open Mixer/Loader “Aerial” –Liquid

2.9 0.023 Inhal. 

 1.2

0.114

lb ai/A 350 A/day Dermal .0020

Inhal. 

.0007 4.9 460

Open Mixer/Loader “Groundboom” Open Cab –Liquid 

2.9 0.023

Inhal.

1.2 

 

0.114

lb ai/A 80 A/day Dermal .0005

Inhal. 

.0002 22 2200

Open Mixer/Loader/Applicator “Groundboom” Open Cab –Liquid

0.37 0.057 1.3 0.114

lb ai/A

80 A/day Dermal 

.0011

Inhal. 

.00016 170 960

Open Mixer/Loader “Airblast” –Liquid

2.9 0.023

Inhal. 

 

1.2

0.114

lb ai/A 40 A/day Dermal .00023

Inhal. 

.000008 43 4100

Open Mixer/Loader “Chemigation” –Liquid

2.9 0.023

Inhal. 

 

1.2

0.114

lb ai/A 350 A/day Dermal .0020

Inhal. 

.0007 4.9 460

Applicator “Aerial” –Closed cockpit (EC)6

0.005 0.0022

Inhal. 

 

0.07

0.114

lb ai/A 350 A/day Dermal .0002

Inhal. 

.00004 2600 5400

Applicator “Groundboom” – Open Cab (EC)

0.014 0.014

Inhal. 

 

0.074

0.114

lb ai/A 80 A/day Dermal .0003

Inhal. 

.00010 3300 3300

Applicator “Airblast” – Open Cab (EC)

0.36 0.24

Inhal. 

 

4.5

0.114

lb ai/A 40 A/day Dermal .0024

Inhal. 

.0003 320 470 

 
Page 36 of 69

Note: Margins of Exposure (MOEs) for “Baseline” Open Mixer/Loader involving 

Aerial, Groundboom, Airblast, and Chemigation are of concern (MOE ≤ 100), however 

label specific directions call for PPE equipment (Gloves). Under these circumstances 

which are noted in table #4, MOEs are not of concern. 

9.2 Occupational Postapplication Exposure and Risk

HED uses the term “post-application” to describe exposures to individuals that occur as a 

result of being in an environment that has been previously treated with a pesticide (also 

referred to as re-entry exposure). HED believes that there are distinct job functions or 

activities that occur in previously treated areas. These job functions (e.g., the kinds of 

jobs to cultivate a crop), the nature of the crop or target that was treated, and the how 

chemical residues degrade in the environment can cause exposure levels to differ over 

time. Each factor has been considered in this assessment.

HED in conjunction with the Agricultural Re-entry Task Force (ARTF) has identified a 

number of post-application agricultural activities that may occur and which may result in 

post-application exposures to pesticide residues. HED estimated the post-application 

exposure for two uses that are considered to have the highest Transfer Coefficients (TC):

Note: In this assessment, there were no chemical-specific residue dissipation data are 

available, in the absence of data, HED typically uses a generic dissipation model to 

complete risk calculations. Model calculation specifics are noted below.

Daily Exposure: The next step in the risk assessment process was to calculate dermal 

exposures on each day after application using the following equation. 

DE(t) (mg/day) = (TR(t) (g/cm2) x TC (cm2/hr) x Hr/Day)/1000 (g/mg)

Where:

DE(t) = Daily exposure or amount deposited on the surface of the skin at 

time (t) attributable for activity in a previously treated area, also 

referred to as potential dose (mg ai/day);

TR(t) = Transferable residues that can either be dislodgeable foliar or turf 

 transferable residue at time (t) where the longest duration is 

dictated by the decay time observed in the studies (g/cm2);

TC = Transfer Coefficient (cm2/hour); 

 hr/day = Exposure duration meant to represent a typical workday (hours).

Daily Dose and Margins of Exposure: Once daily exposures are calculated, the 

calculation of daily absorbed dose and the resulting Margin of Exposures use the same 
Page 37 of 69

algorithms that are described above for the handler exposures (See Section 5.1.3). These 

calculations are completed for each day or appropriate block of time after application.

Post-application Exposure Summary

For all post-application activities concerning this registration action, short-term 

occupational risks are below HED’s level of concern (i.e., MOEs > 100) at day 0. 

Exposure, risk assumptions and MOEs for occupational post-application exposures 

(Agricultural use) are summarized in Table 9.2.

1 Maximum application rate from proposed label 

 2 DAT = Days after treatment needed to reach the LOC of 100; DAT 0 = the day of treatment/ assumed to be approx. 12 

hours. 

 3 DFR (μg/cm2

) = dislodgeable foliar residues corresponding to DAT, based on 20% of application rate.

 4 TC (cm2

/hr) = transfer coefficients and associated activities from ExpoSAC Policy Memo #003.1, 8/17/2000.

 5 MOE = MOE on the corresponding DAT. MOE = NOAEL (1.25 (mg/kg/day) / Daily Dose.

 6 (EC) = Emulsifiable Concentrate formulation

Table 9.2. Summary of Estimated Post-application MOEs for Agricultural Crops

Crop

Application 

Rate

(lb ai/A) 1

DAT2 DFR 3

(μg/cm2)

TC 4

(cm2/hr) Activity 4 Short-Term

MOE5

Brassica Leafy, 

Bulb, Fruiting, 

and Cucurbit 

vegetables

(

6EC)

0.114 0 0.256

100 scouting immature plants 2800

1500 scouting mature plants 190

Non-bearing 

Citrus, Grapes, 

and 

(

6EC)

100 scouting immature plants 2800

1500 harvesting, pruning 190

Tree Nuts

(

6EC)

500 scouting immature plants 560

2500 harvesting, pruning 110
Page 38 of 69

10.0 Data Needs and Label Recommendations

Residue Chemistry

860.1200 Directions for Use – Pertains to Difenoconazole only

 The labels for the 2.08 lb/gal EC formulation (EPA Reg. No. 100-1262), the 2.08 

lb/gal MAI EC formulation (EPA Reg. No. 100-1312), the 1.05 lb/gal MAI SC 

formulation (EPA Reg. No. 100-1313), and the 0.73 lb/gal MAI EW formulation 

(EPA Reg. No. 100-1317) must be revised to specify that no adjuvants may be 

used when the products are applied to almonds, filberts (hazelnuts), pecans, 

pistachios, and tree nuts.

 The 7-day minimum retreatment interval proposed for almond on the label for the 

2.08 lb/gal MAI EC formulation (EPA Reg. No. 100-1312) is not supported by the 

residue data. The label for this product must be revised to specify a minimum 

retreatment interval of 14 days for all tree nuts (including almond).

 If the petitioner intends to support use on turnip greens under Brassica leafy

vegetables, this commodity should be added to the list of Brassica leafy

vegetables, and a separate tolerance must be proposed; otherwise, the restriction 

against feeding treated turnip roots and specifying that only turnip varieties 

harvested for their leaves may be treated should be removed from the label for the 

0.73 lb/gal MAI EW formulation with cyprodinil (EPA Reg. No. 100-1317).

 The label for the 1.05 lb/gal MAI SC formulation (EPA Reg. No. 100-1313) must 

be revised to reflect a 1-day PHI for Brassica leafy vegetables.

 The labels for the 1.05 lb/gal MAI SC formulation (EPA Reg. No. 100-1313) and 

the 0.73 lb/gal MAI EW formulation (EPA Reg. No. 100-1317) should be 

amended to include the following tank mix restrictions: All directions for use, 

crops/sites, use rates, dilution ratios, precautions, and limitations which appear on 

the tank mix product label be observed. The label dosage for the tank mix partner 

is not to be exceeded, and the most restrictive label precautions and limitations are 

to be followed. In addition, the labels for these products should be revised to 

remove contradictory instructions for application equipment types under citrus 

(both labels) and cucurbit vegetables (100-1317 only).

860.1550 Proposed Tolerances

 The proposed tolerances should be revised to reflect the recommended tolerance 

levels and correct commodity definitions as specified in Table 14.

HED recommends that conditional registrations for the requested uses of the EC 
Page 39 of 69

and SC formulations of difenoconazole on bulb vegetables, Brassica leaf vegetables, 

citrus fruits, cucurbit vegetables, pistachios, tree nuts, and grapes; and for the 

requested uses of the EW formulation of difenoconazole on almonds, pistachios, 

Brassica leafy vegetables, and bulb onions, may be converted to unconditional 

registration upon submission of the following residue chemistry data: 

860.1340 Residue Analytical Methods

Livestock Commodities:

 The requirement for additional information concerning the ILV of method REM 

147.07 that was previously identified in DP# 340379 (8/9/07, W. Wassell and M. 

Sahafeyan) is a requirement for unconditional registration for this action. The 

following additional information is needed for the ILV study to fulfill the 

requirements of 860.1340 pertaining to ILVs [see 860.1340(c)(6)(v)]: (1) the 

number of trials required by the ILV laboratory to achieve the reported recovery

values; (2) a discussion of any steps considered by the ILV laboratory to be 

critical (i.e., steps where little variation is allowable or directions should be 

followed precisely); (3) the number of worker-hours required to complete one set 

of samples; (4) the number of calendar days required for one set of samples; and 

(5) a description of any contact between the independent laboratory and the 

method developers or others familiar with the method, including the reasons for 

the contact, any changes in the method that resulted, and the time of this 

communication with respect to the progress of the confirmatory trial (i.e., after the 

first set, during the second set, etc.). 

860.1380 Storage Stability

 Supporting storage stability data for the triazole metabolites are required to 

support the storage conditions (frozen) and intervals (up to 24.8 months) of raw 

agricultural and processed commodity samples collected for the studies reviewed 

herein. No such supporting storage stability data were provided or identified in 

the subject submissions; however, the U.S. Triazole Task Force (USTTF), whose 

members include Syngenta Crop Protection, Inc. among others, has submitted a 

multi-year storage stability study for the triazole metabolites in various crop 

matrices and processed commodities (MRID 47606601) which is currently under 

review in HED (D363016).

 The requirement for storage stability data for cattle commodities that was 

previously identified in DP# 340379 (8/9/07, W. Wassell and M. Sahafeyan) is a 

requirement for unconditional registration for this action. Data should be 

submitted depicting the stability of residues of difenoconazole and CGA 205375 

in milk and cattle tissues during frozen storage for up to 10 months for milk and 9 

months for tissues. The studies cited by the petitioner (report numbers ABR93012 and 202/99), which contain storage stability data for difenoconazole and 

CGA 205375, should be submitted.
Page 40 of 69

Note: Although not required for this action, since there are no poultry feedstuff 

associated with the proposed uses, the requirement for storage stability data for poultry

commodities that was previously identified in DP# 340379 (8/9/07, W. Wassell and M. 

Sahafeyan) remains outstanding. As a reminder, data should be submitted depicting the 

stability of residues of difenoconazole and CGA 205375 in egg and poultry tissue 

samples during frozen storage for up to 7 months for egg and 6 months for tissue 

samples. The studies cited by the petitioner (report numbers ABR-93012 and 202/99), 

which contain storage stability data for difenoconazole and CGA 205375, should be 

submitted.

860.1850 Confined Accumulation in Rotational Crops

 The requirement for an additional confined rotational crop study that was 

previously identified in DP# 344680 (11/5/07, M. Sahafeyan) is a requirement for 

unconditional registration for this action. A confined rotational crop study

reflecting phenyl-ring labeling must be conducted at 1x the proposed maximum 

seasonal foliar application rate (0.46 lb ai/A).

Toxicity

 Immunotoxicity study (870.7800)

In accordance with Part 158 Toxicology Data requirements, an immunotoxicity study

(870.7800) is required for difenoconazole. In the absence of specific immunotoxicity

studies, EPA has evaluated the available difenoconazole toxicity data to determine 

whether an additional database uncertainty factor is needed to account for potential 

immunotoxicity. There are no indications in the available studies that organs associated 

with immune function, such as the thymus and spleen, are affected by difenoconazole, 

and difenoconazole does not belong to a class of chemicals (e.g., the organotins, heavy

metals, or halogenated aromatic hydrocarbons) that would be expected to be 

immunotoxic. Therefore, EPA does not believe that conducting immunotoxicity testing 

will result in a point of departure lower than those already selected for difenoconazole 

risk assessment, and an additional database uncertainty factor is not needed to account for 

the lack of this study.

ORE

 none
Page 41 of 69

11.0 References:

1. HED memo of B. Cropp-Kohlligian, 09/17/09, “Difenoconazole. Application for 

Amended Section 3 Registration to Add Uses on Bulb Vegetables, Brassica Leafy

Vegetables, Cucurbit Vegetables, Citrus Fruits, Grapes, Pistachios, and Tree Nuts. 

Submission of Residue Analytical Methods Data in Response to DP#340379. 

Summary of Analytical Chemistry and Residue Data.” D 361054 and 362648.

2. HED memo of T. Morton, 09/22/09, “Difenoconazole. Acute and Chronic 

Aggregate Dietary Exposure and Risk Assessments for the Section 3 Registration 

Request for Bulb Vegetables, Brassica Leafy Vegetables, Cucurbit Vegetables, 

Citrus Fruit, Grape, Pistachios, and Tree Nut”. D367383. 

3. HED memo of J. Miller, 9/14/09, “Occupational and Residential Risk 

Assessment to Support the Section 3 Request for Registration of Difenoconazole 

on Bulb Vegetables, Brassica Leafy Vegetables, Cucurbit Vegetables, Citrus 

Fruits, Grapes, and Tree Nuts”. DP barcode 361054.

4. EFED memo of I. Maher, 05/28/09, Difenoconazole (Parent Only) Drinking 

Water Assessment in Support of New Use Registration Action for Bulb 

Vegetables, Brassica (Cole) Leafy Vegetables, Cucurbit Vegetables, Citrus Fruit, 

Grapes, and Tree Nuts”.

5. HED memo of M. Sahafeyan, 11/09/09, “PP#: 6F7115. Difenoconazole in/on 

Fruiting Vegetables, Pome Fruit, Sugar Beets, Tuberous and Corm Vegetables, 

and Imported Papaya. Health Effects Division (HED) Revised Risk 

Assessment. DP#: 346591. PC Code: 128847. Decision#: 371264”. D346591.

6. HED memo of T. Morton, 08/13/09, “ Common Triazole Metabolites: Updated 

Aggregate Human Health Risk Assessment to Address Tolerance Petitions for 

Difenoconazole”. D367861.

7. HED memo of. of T. Morton, 08/13/09, “ Common Triazole Metabolites: 

Updated Dietary (Food + Water) Exposure and Risk Assessment to Address The 

Tolerance Petitions for Difenoconazole”. D367860.
Page 42 of 69

12.0 Tolerance Summary

Table 12. Tolerance Summary for Difenoconazole.

Commodity Proposed 

Tolerance (ppm)

Recommende

d Tolerance 

(ppm)

Comments; Correct 

Commodity Definition

Almond, hulls 7 7.0

Brassica, head & stem, 

subgroup 5A

1.9 1.9 Brassica, head and stem, 

subgroup 5A

Brassica, leafy green, 

subgroup 5B

30 35 Brassica, leafy greens, 

subgroup 5B

Citrus, dried pulp 2.5 2.0

Citrus, oil 28 25

Fruit, citrus, group 10 0.6 0.60

Grape 4 4.0

Grape, raisin 14 6.0

Nut, tree, group 14 0.03 0.03

Onion, bulb, subgroup 3-

07A

6

1

0.20

Onion, green, subgroup 3-

07B

0.151

6.0

Pistachios 0.03 0.03 Pistachio

Vegetable, cucurbit, group 

9

0.7 0.70

1

 The proposed tolerances for bulb and green onions appear to have been transposed by

the petitioner.
Page 43 of 69

13.0 Appendices

Appendix 1: Acute Toxicity Data on Difenoconazole Technical

Table 13.0a Acute Toxicity Profile - Difenoconazole

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

870.1100 Acute oral rat 42090006 LD50 = 1450 

mg/kg

III

870.1200 Acute dermal rat 42090007 LD50 > 2010 

mg/kg

III

870.1300 Acute inhalation rat 42090008 LC50 > 3.3 mg/L III

870.2400 Acute eye irritation rabbit 42090009 Mild ocular 

irritation 

reversible in 7 

days

III

870.2500 Acute dermal irritation rabbit 42090010 Slight irritation IV

870.2600 Skin sensitization mouse 42090011, 

42710004

Negative N/A
Page 44 of 69

Appendix 2: Subchronic, Chronic and Other Toxicity Profile

Table 13.0b Subchronic, Chronic and Other Toxicity Profile of Difenoconazole

Guideline

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.3100 90-Day oral 

toxicity (rat)

42090022 (1987)

Acceptable/guideline

0, 20, 200, 750, 1500 or 

3000 ppm

0, 1, 10, 37.5, 75 and 

150 mg/kg/d

NOAEL = 20 ppm (1 mg/kg/day)

LOAEL = 200 ppm (10 mg/kg/day) based on the 10% 

decrease in body weight in the 200 ppm females (as 

well as a negative trend in feed consumption) and 

Increases in absolute liver weights in both sexes

870.3100 90-Day oral 

toxicity (mouse)

42090021 (1987)

Minimum/guideline

0, 20, 200, 2500, 7500 or 

15,000 ppm 

M: 0, 2.9, 30.8, 383.6, 

1125 and 2250 mg/kg/d

F: 0, 4.1, 41.5, 558.9, 

1125 and 2250 mg/kg/d

NOAEL = 20 ppm (2.9 mg/kg/day)

LOAEL = 200 ppm (30.8 mg/kg/day) based on body 

weight changes & liver histopathology.

870.3150 26-Week oral 

toxicity

42090012 (1987)

Minimum/ guideline

0, 100, 1000, 3000 or 

6000 ppm

M: 0, 3.6, 31.3, 96.6 and 

157.8 mg/kg/d

F: 0, 3.4, 34.8, 110.6 and 

203.7 mg/kg/d

NOAEL = 3000 ppm (31.3 mg/kg/day in males/34.8 

mg/kg/day in females)

LOAEL = 6000 ppm (96.6 mg/kg/day in males/110.6 

mg/kg/day in females), based primarily on microscopic 

examination of CGA 169374-related lenticular 

cataracts.

870.3200 21/28-Day dermal 

toxicity (rat)

42090013 (1987)

Minimum/ guideline

0, 10, 100 and 1000 

mg/kg/d

NOAEL = 10 mg/kg/day

LOAEL = 100 mg/kg/day based on statistically 

significant decrements in body weight, body weight 

gain, and food consumption.

870.3200 21/28-Day dermal 

toxicity (rat)

46950310 (2000)

Acceptable/ guideline

0, 10, 100 and 1000 

mg/kg/d

NOAEL (systemic) = 1000 mg/kg/day

LOAEL (systemic) was not determined.

NOAEL (dermal) = 100 mg/kg/day

LOAEL (dermal) = 1000 mg/kg/day based on 

hyperkeratosis at the skin application site.
Page 45 of 69

Table 13.0b Subchronic, Chronic and Other Toxicity Profile of Difenoconazole

Guideline

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.3700a Prenatal 

developmental in 

(rat)

42090016, 42710007 

(1987)

Minimum/ guideline

0, 2, 20, 100 or 200 

mg/kg/d from GD 6-15 

(nominal doses differed 

widely from theoretical, 

this required altering 

NOAEL/LOAEL values)

Maternal NOAEL = 16 mg/kg/day

LOAEL = 85 mg/kg/day based on decreased body 

weight gain and food consumption.

Developmental NOAEL = 85 mg/kg/day

LOAEL = 171 mg/kg/day based on alterations in fetal 

ossification.

870.3700b Prenatal 

developmental in 

(rabbit)

42090017, 42710008 

(1987)

Minimum/ guideline

0, 1, 25 or 75 mg/kg/d 

from GD 7-19

Maternal NOAEL = 25 mg/kg/day

LOAEL = 75 mg/kg/day based on decreased body 

weight gain and food consumption. 

Developmental NOAEL = 25 mg/kg/day

LOAEL = 75 mg/kg/day based on nonsignificant 

increases in postimplantation loss and resorptions/doe 

and a significant decrease in fetal weight.

870.3800 Reproduction and 

fertility effects

(rat)

42090018 (1988)

Minimum/ guideline

0, 25, 250 or 2500 ppm

0, 1.25, 12.5 and 125 

mg/kg/d

Parental/Systemic NOAEL = 25 ppm (1.25 

mg/kg/day) 

LOAEL = 250 ppm (12.5 mg/kg/day) based on 

reductions (statistically nonsignificant) in body weight 

gain which appear to be part of a dose-related trend 

days 70-77 prior to mating, days 0-7 of gestation, and 

days 7-14 of lactation

Reproductive NOAEL = 25 ppm (1.25 mg/kg/day)

LOAEL = 250 ppm (12.5 mg/kg/day) based on a 

significant reduction in the body weight of F1 male 

pups at day 21 in the 250 ppm group.

870.4100b Chronic toxicity

(dog)

42090012, 42710005 

(1988)

Minimum/ guideline

0, 20, 100, 500 or 1500 

ppm

M: 0, 0.71, 3.4, 16.4 and 

51.2 mg/kg/d

F: 0, 0.63, 3.7, 19.4 and 

44.3 mg/kg/d

NOAEL = 100 ppm (3.4 mg/kg/day in males/3.7 

mg/kg/day in females)

LOAEL = 500 ppm (16.4 mg/kg/day in males/19.4 

mg/kg/day in females), based on significant inhibition 

of body weight gain in females.
Page 46 of 69

Table 13.0b Subchronic, Chronic and Other Toxicity Profile of Difenoconazole

Guideline

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.4200 Carcinogenicity

(rat)

42090019, 42710010 

(1989)

Minimum/ guideline

0, 10, 20, 500 or 2500 

ppm

M: o, 0.48, 0.96, 24.12 

and 123.7 mg/kg/d

F: 0, 0.64, 1.27, 32.79 

and 169.6 mg/kg/d

NOAEL = 20 ppm (0.96 mg/kg/day in males/1.27 

mg/kg/day in females)

LOAEL = 500 ppm (24.1 mg/kg/day in males/ 32.8 

mg/kg/day in females) based on reductions in 

cumulative body weight gains in the 500 and 2500 ppm 

groups.

No evidence of carcinogenicity

870.4300 Carcinogenicity

(mouse)

42090015, 42710006 

(1989)

Minimum/ guideline

0, 10, 30, 300, 2500 or

3000 ppm

M: 0, 1.51, 4.65, 46.29, 

423.1 and 818.9 mg/kg/d

F: 0, 1.9, 5.63, 57.79 and 

512.6 mg/kg/d

NOAEL = 30 ppm (4.7 mg/kg/day in males/5.6 

mg/kg/day in females)

LOAEL = 300 ppm (46.3 mg/kg/day in males/57.8 

mg/kg/day in females) based on reductions in the 

cumulative body weight gains in the 300, 2500 & 4500 

ppm groups. 

Evidence of carcinogenicity (liver 

adenoma/carcinoma in both sexes)

870.5100 In vitro bacterial 

gene mutation

(Salmonella 

typhimurium/ E. 

coli)/ mammalian 

activation gene 

mutation assay

42090019, 42710010 

(1989)

Minimum/ guideline

340 - 5447 μg/plate;

85 - 1362 μg/plate 

(repeat assay with 

TA1537 and TA98)

There were sufficient and valid data to conclude that 

CGA 169374 technical was negative in the microbial 

gene mutation assay.

870.5300 in vitro mammalian 

cell gene mutation 

assay in mouse 

lymphoma cells

42090024 (1986)

Unacceptable/ guideline

No conclusion can be reached from the three 

nonactivated and two S9 activated mouse lymphoma 

forward mutation assays conducted with difenoconazole 

technical. The study was seriously compromised.

870.5375 In vitro

Mammalian 

Cytogenetics

(chromosomal 

aberrations) assay

in Chinese hamster 

CHO cells

46950319 (2001)

Acceptable/ guideline

0, 21.99, 27.49, or 34.36 

μg/mL (-S9)

0, 34.36, 53.69 or 67.11 

μg/mL (+S9)

There was evidence of a weak induction of structural 

chromosomal aberrations over background in the 

presence of S9-mix.
Page 47 of 69

Table 13.0b Subchronic, Chronic and Other Toxicity Profile of Difenoconazole

Guideline

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.5375 In vitro

Mammalian 

Cytogenetics

(chromosomal 

aberrations) assay

in Chinese hamster 

CHO cells

46950321 (2001)

Acceptable/ guideline

0, 26.3, 39.5 or 59.3 

μg/mL (-S9)

0, 11.7 or 17.6 μg/mL 

(+S9)

There was evidence of a weak induction of structural 

chromosomal aberrations over background.

870.5375 In vitro

Mammalian 

Cytogenetics

(chromosomal 

aberrations) assay

in human 

lymphocytes

46950323 (2001)

Acceptable/ guideline

0, 5, 30 or 75 μg/mL (-

S9)

0, 5, 30 or 62 μg/mL

(+S9)

There was no evidence of structural chromosomal 

aberrations induced over background.

870.5385 In vivo mammalian 

chromosomal 

aberration test 

Assay in Mice

42090023 (1986)

Unacceptable/guideline

250, 500 or 1000 mg/kg

There was no evidence of a cytotoxic effect on the 

target organ or significant increase in the frequency of 

nuclear anomalies (micronuclei). However, the study 

was compromised.

870.5395 In vivo mammalian 

cytogenetics -

erythrocyte 

micronucleus assay 

in mice

41710011 (1992)

Acceptable/guideline

Doses up to 1600 mg/kg

Mice bone marrow - No increase in micronucleated 

polychromatic erythrocytes occurred with CGA-1 

69374 (91.2% a.i).

870.5550 Unscheduled DNA 

Synthesis in 

Mammalian Cells 

in Culture

4210012 (1992)

Acceptable/ guideline

Doses up to 50 μg/mL

CGA-i69374 tech. (92.2% a.i.) was considered to be 

negative in the unscheduled DNA synthesis assay in rat 

primary hepatocytes as measured by an 

autoradiographic method at concentrations up to 50.0 

μg/mL.

870.5550 Unscheduled DNA 

Synthesis in 

Mammalian Cells 

in Culture

42090027 (1985)

Unacceptable/ guideline

0.25-31.25 μg/mL

No conclusion can be reached from the unscheduled 

DNA synthesis (UDS) primary rat hepatocyte assay 

conducted with difenoconazole technical at 

concentrations ranging from 0.25 to 31.25 μg /mL. The 

sensitivity of the study was severely compromised.

870.5550 Unscheduled DNA 

Synthesis in 

Mammalian Cells 

in Culture

42090026 (1985)

Unacceptable/ guideline

0.08-10 μg/mL

No conclusion can be reached from the unscheduled 

DNA synthesis (UDS) human fibroblast assay 

conducted with difenoconazole tech. at conc. ranging 

from 0.08 to 10 μg /mL. 
Page 48 of 69

Table 13.0b Subchronic, Chronic and Other Toxicity Profile of Difenoconazole

Guideline

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.6200a Acute neurotoxicity 

screening battery

46950327 (2006)

Acceptable/ guideline

0, 25, 200 or 2000 

mg/kg/d

NOAEL (M) = 25 mg/kg/day

LOAEL (M) = 200 mg/kg/day based on reduced forelimb grip strength in males on day 1 and increased 

motor activity on Day 1. 

NOAEL (F) = 200 mg/kg/day

LOAEL (F) = 2000 mg/kg/day based on decreased 

body weight, the following clinical signs: upward 

curvature of the spine, tip-toe gait, decreased activity, 

piloerection and sides pinched in and decreased motor 

activity.

870.6200b Subchronic 

neurotoxicity 

screening battery

46950329 (2006)

Acceptable/ guideline 

0, 40, 250, or 1500 ppm 

M; 0, 2.8, 17.3 or 107.0 

mg/kg/d 

F: 0, 3.2, 19.5, or 120.2 

mg/kg/d

NOAEL (M) = 40 ppm (2.8 mg/kg/day)

LOAEL (M) = 250 ppm (17.3 mg/kg/day) based on

decreased hind limb strength. 

NOAEL (F) = 250 ppm (19.5 mg/kg/day)

LOAEL (F) = 1500 (120.2 mg/kg/day) based on

decreased body weight, body weight gain and food 

efficiency. 

870.7485 Metabolism and 

pharmacokinetics

(rat)

42090028 (1990)

Acceptable/ guideline

14 daily doses of 0.5 or 

300 mg/kg

The absorption, distribution, metabolism, and excretion 

of CGA 169374 were studied in groups of male and 

female Sprague-Dawley rats. Animals were 

administered a single oral gavage dose of 0.5 or 300 

mg/kg [14C]CGA- 169374, or 0.5 mg/kg unlabeled 

GGA-169374 by gavage for 14 days followed by a 

single gavage dose of 0.5 mg/kg [14C)CGA-169374 on 

day 15. The test compound was labeled with C14 at 

either the phenyl or triazole ring.

870.7485 Metabolism and 

pharmacokinetics

(rat)

42090031 (1988)

Acceptable/ guideline

0.5 or 300 mg/kg

These studies indicate that distribution, metabolism, 

and elimination of CGA-169374 were not sex related. 

There was a slight dose difference in the metabolism 

and elimination of CGA-169374. In phenyl and triazole 

labeling studies, fecal excretion of radioactivity was 

higher in the high dose animals compared to the low 

dose animals, and an additional metabolite was found in 

the feces of the high dose animals compared to the low 

dose animals. There was no major difference in the 

distribution and excretion of radioactivity with labeling 

at the phenyl and triazole ring positions, however, there 

were some different metabolites identified. The studies 

also showed that administration of 0.5 and 300 mg/kg 

CGA- 169314 did not induce any treatment related 

clinical effects.
Page 49 of 69

Table 13.0b Subchronic, Chronic and Other Toxicity Profile of Difenoconazole

Guideline

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.7485 Metabolism and 

pharmacokinetics

(rat)

420710013, 42710014 

(1990)

Acceptable/ guideline

0.5 or 300 mg/kg

These two studies described the absorption, 

distribution, and excretion as the pharmacokinetics and 

isolated and identified urinary metabolites. Issues raised 

in the previous supplementary studies were answered. 

In conjunction with these studies, the previous studies 

are upgraded.

870.7485 Metabolism and 

pharmacokinetics

(rat)

42090029 (1987)

Acceptable/ guideline

[14C]CGA-169374 was rapidly and extensively 

distributed. metabolized, and excreted in rats for all 

dosing regimens. The extent of absorption is 

undetermined pending determination of the extent of 

biliary excretion. The 4-day recoveries were 97.4-

107.75% of the administered dose for all dosing 

groups. The elimination of radioactivity in the feces 

(78.06- 94.61% of administered dose) and urine (8.48-

21.86%) were almost comparable for all oral dose 

groups, with slightly higher radioactivity found in the 

feces of the high dose group than the low dose groups. 

This was probably due to biliary excretion, poor 

absorption or saturation of the metabolic pathway. The 

radioactivity In the blood peaked at about 24-48 hours 

for all dosing groups. Half-lives of elimination appear 

to be approximately 20 hours for the low dose groups 

and 33 - 48 hours for the high dose group. The study 

results also indicate that CGA-1 69374 and/or its 

metabolites do not bioaccumulate to an appreciable 

extent following oral exposure since all the tissues 

contained negligible levels (<1%) of radioactivity 7 

days postexposure.

870.7485 Metabolism and 

pharmacokinetics

(rat)

42090030 (1987)

Acceptable/ guideline

The metabolism of CGA-169374 appears to be 

extensive because the metabolites accounted for most 

of the recovered radioactivity in the excreta. Three 

major metabolites were identified in the feces (i.e., A, 

B, and C). Two of the metabolites were separated into 

isomers (i.e., A1, A2, B1, and B2). Metabolite C was 

detected only In the high dose groups, indicating that 

metabolism of CGA-169374 is dose related and 

involves saturation of the metabolic pathway. Free 

triazole metabolite was dete6ted in the urine of triazole 

labeled groups and its byproduct was detected In the 

liver of phenyl labeled groups only. Other urinary 

metabolites were not characterized.
Page 50 of 69

Table A.1.3. Subchronic, Chronic and Other Toxicity Profile of Difenoconazole Metabolites 

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.5100 In vitro Bacterial 

Gene Mutation

(Salmonella 

typhimurium/ E. 

coli)/ mammalian 

activation gene 

mutation assay

46950314 (1991)

Unacceptable/ guideline

0, 31.3, 62.5, 125, 250, 

500 or 1000 μg/plate in 

strains TA100 and 

TA1537 (-S9)

0, 31.3, 62.5, 125, 250, 

500 or 1000 μg/plate in 

all strains (+S9)

0, 62.5, 125, 250, 500, 

1000 or 2000 μg/plate in 

strains TA1535, WP2 

uvrA and TA98 (-S9)

0, 62.5, 125, 250, 500, 

1000 or 2000 μg/plate in 

strains WP2 uvrA (+S9)

The number of revertants per plate was not increased 

over the concurrent solvent control value at any test 

material concentration, with or without S9-mix, in any

tester strain. The solvent and positive controls induced 

the appropriate responses in the corresponding strains. 

There was no evidence of induced mutant colonies over 

background.

Tested: CGA-189138 (metabolite of difenoconazole)

870.5100 In vitro Bacterial 

Gene Mutation

(Salmonella 

typhimurium/ E. 

coli)/ mammalian 

activation gene 

mutation assay

46950315 (1991)

Unacceptable/ guideline

0, 156, 313, 625, 1250, 

2500 or 5000 μg/plate 

(S9)

The number of revertants per plate was not increased 

over the concurrent solvent control value at any test 

material concentration, with or without S9-mix, in any 

tester strain. The solvent and positive controls induced 

the appropriate responses in the corresponding strains. 

There was no evidence of induced mutant colonies over 

background.

Tested: CGA205374 (metabolite of difenoconazole)

870.5100 In vitro Bacterial 

Gene Mutation

(Salmonella 

typhimurium/ E. 

coli)/ mammalian 

activation gene 

mutation assay

46950317 (1991)

Unacceptable/ guideline

0, 2.50, 5.00, 10.0, 20.0, 

40.0 or 80.0 μg/plate in 

all strains (-S9)

0, 5.00, 10.0, 20.0, 40.0, 

80.0 or 160 μg/plate in 

strains TA100 and 

TA1535 (+S9)

0, 10.0, 20.0, 40.0, 80.0, 

160 or 320 μg/plate in 

strains WP2 uvrA and 

TA1537 (-S9)

0, 2.50, 5.00, 10.0, 20.0, 

40.0, or 80.0 μg/plate in

strain TA98 (+S9)

The number of revertants per plate was not increased 

over the concurrent solvent control value at any test 

material concentration, with or without S9-mix, in any 

tester strain. The solvent and positive controls induced 

the appropriate responses in the corresponding strains. 

There was no evidence of induced mutant colonies 

over background.

Tested: CGA205375 (metabolite of difenoconazole)
Page 51 of 69

EXECUTIVE SUMMARIES OF SOME STUDIES:

STUDY TYPE: 28-Day Dermal Toxicity – Rat 

(OPPTS 870.3200 [§82-2] (rodent); OECD 410).

CITATION: Gerspach, R. Difenoconazole: 28-Day Repeated Dose Dermal Toxicity

Study in Rats. Novartis Crop protection AG Toxicology (Switzerland). Novartis Report 

Number: 993072; Syngenta Report Number: T002728-06. July 11, 2000, MRID 

46950310 and MRID 46950311. Unpublished.

EXECUTIVE SUMMARY: In a 28-day dermal toxicity study (MRID 46950310) CGA 

169374 Technical (91.8% a.i., Batch No. P807002) was applied to the shaved skin of ten 

male and ten female rats at dose levels of 0, 10, 100 and 1000 mg/kg bw/day. There were 

no treatment-related effects on body weight or food consumption. Non clinical signs of 

toxicity were noted including specific indicators of neurotoxicity. The dose level of 1000 

mg/kg bw/day caused hyperkeratosis at the skin application site. A high incidence of 

follicular cell hypertrophy of the thyroid was observed in males and females of control 

and all treatment groups and variations with dose are not considered treatment-related. 

Minimal inconsequential changes were noted on clinical chemistry parameters in high 

dose males that were not relevant toxicologically. The incidence and severity was 

increased in animals in the highest dose group. There was an increase in the absolute 

(12%) and relative (16%) weight of the liver in males in the high dose group 

accompanied by an increased incidence of slight hepatocellular hypertrophy (7/10) 

compared to controls (2/10). Females in the high dose group also had an increase in the 

relative weight of the liver (10%) with an increased incidence of slight hepatocellular 

hypertrophy (7/10) compared to controls (1/10). These effects are consistent with 

adaptive responses of the liver.

A systemic LOAEL for male and female rats was not established. The NOAEL for 

male and female rats is 1000 mg/kg bw/day.

A dermal irritation LOAEL for male and female rats is 1000 mg/kg bw/day based 

on hyperkeratosis at the skin application site. The dermal NOAEL for male and 

female rats is 100 mg/kg bw/day.

This 28-day dermal toxicity study in the Fischer 344 rat is Acceptable/Guideline and 

satisfies the guideline requirement for a 28-day dermal toxicity study (OPPTS 870.3200; 

OECD 410) in the rat.

STUDY TYPE: Acute Neurotoxicity - Rats OPPTS 870.6200a [§81-8]; OECD 424.

CITATION: Pinto, P.J. (2006) Difenoconazole Technical (CGA169374): Acute 

Neurotoxicity Study in Rats. Central Toxicology Laboratory (Cheshire, 
Page 52 of 69

UK). Laboratory report number AR7517-REG-R1, July 28, 2006. MRID 

46950327. Unpublished.

Pinto, P.J. (2006) Difenoconazole Technical (CGA169374): Preliminary Acute 

Neurotoxicity Study in Rats. Central Toxicology Laboratory (Cheshire, 

UK). Laboratory report number AR7518-REG, June 16, 2006. MRID 

46950325. Unpublished.

EXECUTIVE SUMMARY: In an acute neurotoxicity study (MRID 46950327), groups 

of fasted Alpk:APfSD Wistar-derived rats (10/sex/dose), at least 42 days old, were given 

a single oral dose of difenoconazole technical (CGA169374) (94.3% w/w, batch/lot # 

WM806228) in 1% w/v aqueous carboxymethylcellulose (CMC) at doses of 0, 25, 200, 

or 2000 mg/kg bw and observed for 14 days. Dose levels selected for this study were 

based on the results of a preliminary acute neurotoxicity study (MRID 46950325). 

Neurobehavioral assessment (functional observational battery and motor activity testing) 

was performed on 10 animals/sex/group on days -7, 1, 8, and 15. Body weight and food 

consumption were measured weekly throughout the study. At study termination, 5 

animals/sex/group were euthanized and perfused in situ for neuropathological 

examination; brain weight was recorded from these animals. Of the perfused animals, 5 

animals/sex from the control and high dose groups were subjected to histopathological 

evaluation of brain and peripheral nervous system tissues. 

There were no unscheduled deaths at any dose level. Weight change on the day of dosing 

by the control, low-, mid-, and high-dose groups was -2.1, -1.0, -7.8, and -18.3 g, 

respectively, for males and 0.0, 2.1, -3.8, and -13.0 g, respectively, for females. Body

weight for females had recovered to control levels by day 8. Food consumption for males 

given 2000 mg/kg was approximately 20% less than control during week 1 only (p<0.01). 

Food consumption for these animals recovered to control levels during week 2. There 

were no differences from control for females at any dose level or for males at the lower 

dose levels. These effects on body weight and food consumption were not toxicologically

significant.

At 2000 mg/kg, a number of adverse clinical signs were observed on day 1 (at the time of 

peak effect), including: upward curvature of the spine (8 males, 9 females); tip-toe gait (3, 

8); decreased activity (6, 7); piloerection (3, 5); sides pinched in (3, 7); and subdued (1, 

0). Females were affected more than males. All treatment-related clinical signs observed 

on day 1 showed complete recovery by day 5 (males) or day 7 (females). 

Significant decreases in fore-limb grip strength were seen in mid- (↓23%) and high-dose 

(↓26%) males on day 1. Females dosed with 2000 mg/kg had lower motor activities on 

day 1 (37%), at the time of peak effect, and on day 8 (31%). Males dosed with 200 or 

2000 mg/kg had higher motor activities than the controls on day 1, 50% and 55%, 

respectively, at the time of peak effect.

There were no effects on brain weight at any dose level. Neuropathological 
Page 53 of 69

examination of the central and peripheral nervous system showed no effects of 

treatment at doses of 2000 mg/kg in both sexes.

The LOAEL for acute neurotoxicity of difenoconazole technical (CGA169374) in 

male rats is 200 mg/kg bw based on reduced fore-limb grip strength in males on day 

1 and increased motor activity on Day 1. The NOAEL is 25 mg/kg bw. 

The LOAEL for acute neurotoxicity of difenoconazole technical (CGA169374) in 

female rats is 2000 mg/kg bw based on decreased body weight, the following clinical 

signs: upward curvature of the spine, tip-toe gait, decreased activity, piloerection 

and sides pinched in and decreased motor activity. The NOAEL is 200 mg/kg bw. 

This acute neurotoxicity study is classified as Acceptable/Guideline and satisfies the 

guideline requirement for an acute neurotoxicity study in rats (870.6200; OECD 424). 

Positive control data have been submitted for review and were considered acceptable.

STUDY TYPE: Subchronic Neurotoxicity, OPPTS 870.6200b [§82-7] feeding - rat; 

(OECD 424).

CITATION: Pinto, P J. (2006). Difenoconazole technical (CGA 169374) subchronic 

neurotoxicity study in rats, final report. Central Toxicology Laboratory, 

Alderley Park, Macclesfield, Cheshire, UK SK 10 4TJ. Report number 

PR1330-REG-R1. July 28, 2006. MRID 46950329. Unpublished. 

Pinto, P.J. (2006). Difenoconazole technical (CGA 169374) 28-day dietary

rangefinding study in rats, final report. Central Toxicology Laboratory, 

Alderley Park, Macclesfield, Cheshire, UK SK 10 4TJ. Report number 

KR1606-REG. June 13, 2006. MRID 46950326. Unpublished. 

Alexander, O. (2006) Difenoconazole technical (CGA 169374) subchronic 

neurotoxicity study in rats – study profile. Syngenta Crop Protection, Inc., 

410 Swing Road, P.O. Box 18300, Greensboro, NC 27419-8300. Report 

number PR1330-REG-R1. September 19, 2006. MRID 46950330. 

Unpublished. 

EXECUTIVE SUMMARY: In a subchronic neurotoxicity study (MRID 46950329) 

difenoconazole technical (94.5% w/w, batch no. WM806228) was administered to groups 

of 12 male and 12 female Alpk:APfSD (Wistar-derived) rats at concentrations of 0, 40, 

250, or 1500 ppm in the diet for 90 days. Respective dose levels corresponded to 0, 2.8, 

17.3 or 107.0 mg/kg bw/day for males and 0, 3.2, 19.5, or 120.2 mg/kg bw/day for 

females. Neurobehavioral assessment (functional observational battery and motor 

activity testing) was performed in 12 animals/sex/group pretest and during weeks 2, 5, 9, 

and 14. Cholinesterase activity was not determined. At study termination, 5 

animals/sex/group were euthanized and perfused in situ for neuropathological 

examination. Of the perfused animals, 5/sex from the control group and 5/sex from the 
Page 54 of 69

1500 ppm group were subjected to histopathological evaluation of brain and peripheral 

nervous system tissues. 

Treatment with difenoconazole at concentrations up to 1500 ppm in the diet had no effect 

on mortality or clinical signs. Relative to respective control weight, final body weight of 

males and females in the 1500 ppm group was reduced by 9% and 7%. Body weight gain 

was reduced by 22% in males and 23% in females. Food consumption was reduced in 

this group (statistically significant only in females [7%]), and food efficiency was 

significantly reduced in males by 21% (p≤0.05) and in females by 21% (ns). Lower dose 

groups were unaffected. Absolute liver weight in males and females in the 1500 ppm 

group was increased over respective control weight by 38% and 45%. Liver was not 

weighed in lower dose groups. The increase in liver weight was considered a normal 

response to chemical treatment.

During weeks 2, 9 and 14, hind-limb grip strength in males in the 1500 ppm group was 

reduced by 18 to 27% relative to the control values. At week 14, hind-limb grip strength 

in males in the 250 ppm group was significantly (p≤0.05) reduced by 20% relative to the 

control values. FOB observations in females were unaffected by treatment. Motor 

activity was unaffected in both sexes at all observation times. Brain weight was 

unaffected by treatment and there were no treatment-related neuropathological lesions. 

The LOAEL in male rats is 250 ppm in the diet (17.3 mg/kg bw/day), based on 

decreased hind limb strength. The NOAEL is 40 ppm (2.8 mg/kg bw/day).

The LOAEL in female rats is 1500 ppm in the diet (120.2 mg/kg bw/day), based on 

decreased body weight, body weight gain and food efficiency. The NOAEL is 250 

ppm (19.5 mg/kg bw/day).

The study is classified as Acceptable/Guideline and does satisfies the guideline 

requirement for a subchronic neurotoxicity study in rats (870.6200b). Positive control 

data have been submitted for review and were considered acceptable.

STUDY TYPE: Rodent In Vivo Dermal Penetration Study – Rat 

OPPTS 870.7600 [§85-2]; OECD none.

CITATION: Hassler, S. (2003) Difenoconazole 250 EC (A7402G): Dermal absorption 

of [Triazole-U14C] CGA 169374 formulated as Score® 250 EC (A7402G) in the rat (in vivo). Syngenta Crop Protection AG, Health 

Assessment/Animal Metabolism CH-4002 Basel, Switzerland. Syngenta 

Number T002729-06, May 6, 2003. MRID 46950333. Unpublished.

EXECUTIVE SUMMARY: In a dermal penetration study (MRID 46950333), 

[Triazole–U14C] CGA 169374 (radiolabled: batch # 50.2-1 and 50.2-2 contained 98 and 

99.3% a.i., respectively; nonradiolabeled: batch # AMS 255/3 contained 99.3% a.i.)

formulated as Score® 250 EC (A-7402G) was administered to 16 male HanBrl: WIST 
Page 55 of 69

(SPF) rats/dose to a skin area of 10 cm2at nominal dose levels of 0, 0.005, 0.0125, and 

2.5 mg/cm2skin. The 2.5 mg/cm2dose was repeated because of a high variability in the 

results of the washing procedure. Measured dose levels were 0.005, 0.0130, 2.4, and 2.6 

mg/cm2for the low, mid, and high dose and high dose repeat groups, respectively. 

Exposure duration was 6 hours and animals were monitored for 6, 24, 48, or 72 hours. 

The remaining discussion of dermal penetration at the high dose will include only the 

“high-dose repeat” data (i.e., the results of the first high-dose exposure will not be 

discussed). Recovery of the applied dose was acceptable with group means ranging from

95.44 to 103.67%. Results were not adjusted for incomplete recovery of the applied dose. 

The majority of the applied dose was recovered in the skin wash, accounting for 49-69%, 

73-78%, and 76-86% of the low, mid, and high dose, respectively. The amount of the 

applied dose retained at the application site was 8-12%, 3-5%, and 2-5% of the low, mid, 

and high dose, respectively. At the low and mid dose, the major part of the radioactivity

remaining in the skin was associated with the stratum corneum (7-11% and 2-5%, 

respectively), while only 1-2% of the high dose was recovered in the upper skin layer. 

Dermal absorption (sum of blood, carcass, urine, feces, skin test site, gastrointestinal 

tract, untreated skin, and cagewash) accounted for 15-38%, 7-15%, and 3-11% of the low, 

mid, and high doses, respectively. Of the test substance systemically absorbed, excretion 

into the feces was generally the primary route of elimination, accounting for up to 18%, 

8%, and 2% of the low, mid, and high doses, respectively. Of the radioactivity remaining 

in the animal 72 hours after application, the gastrointestinal tract contained 3.0%, 1.4%, 

and 0.3% of the low, mid, and high doses, respectively, and the carcass contained 1.5%, 

0.7%, and 1.1%, respectively. Blood concentrations during and after the exposure period 

were at or below the limits of determination. Based on the limited blood concentration 

data available, maximum blood concentrations were measured between 6-8 hours after 

dose application. 

Based on the amount of radioactivity entering the systemic circulation within 6 hours of 

exposure, the calculated penetration rates at the low, mid, and high doses were 0.013, 

0.162, and 30.4 μg cm-2h

-1

, respectively. The penetration rates increased somewhat 

proportionally with the increase of the test substance concentration at the three dose 

levels (1:26:5100 for the concentration ratio of the dose levels versus 1:12:2300 for the 

ratio of the penetration values).

This study in the rat is unacceptable/guideline and does not satisfy the guideline 

requirement for a dermal penetration study (870.7600) in rats. Major deficiencies include 

uncertainty in the ability of the laboratory to perform the experiment, and only one 

exposure duration was tested (6 hours), despite minimum Guideline recommendations for 

durations of 1, 10, and 24 hours. See “Study Deficiencies” for listing of numerous minor 

deficiencies. 

STUDY TYPE: In Vitro Dermal Penetration Study – Rat and Human 

OPPTS 870.7600 [§85-2]; OECD none.

CITATION: Hassler, S. (2003) Difenoconazole 250 EC (A7402G): The percutaneous 
Page 56 of 69

penetration of [Triazole-U14C] CGA 169374 formulated as Score® 250

EC (A-7402G) through rat and human split-thickness skin membranes (in 

vitro). Syngenta Crop Protection AG, Health Assessment/Animal 

Metabolism CH-402 Basel, Switzerland. Syngenta Number T002730-06, 

April 9, 2003. MRID 46950332. Unpublished.

EXECUTIVE SUMMARY: In an in vitro percutaneous penetration study (MRID 

46950332), [Triazole–U14C] CGA 169374 (98% a.i., batch number 50.2-1) mixed with 

nonradiolabeled CGA 169374 (batch number AMS 255/3 containing 99.3% a.i.)

formulated as SCORE 250® (A-7402) was applied to skin membranes prepared from rat 

[male HanBrl: WIST (SPF)] and human (cadaver) abdominal skin. Percutaneous 

absorption at low, mid, and high doses of 0.5, 12.5, or 2500 μg/cm2(actual applied doses 

of 0.5, 12, or 2345 μg/cm2) was assessed over 24 hours. 

Results clearly indicate that transfer of [Triazole–U14C] CGA 169374 across skin 

membrane was notably greater for the rat skin membrane than for human skin membrane 

as shown by flux values that were 10-, 12-, and 32-fold greater for the low, mid, and high 

concentrations, respectively. A concentration-dependent absorption was also indicated by

greater flux values with increasing concentration: flux values at the low, mid, and high 

doses for the rat skin membranes were 0.020, 0.455, and 26.2 ug/cm2, respectively, and 

for human skin membranes were 0.002, 0.037, and 0.822 ug/cm2, respectively. The 

increasing flux values resulted in greater absolute amounts of test article being transferred 

across the skin membranes with increasing concentration: values at the low, mid, and 

high doses for the rat skin membranes were 0.35, 7.7, and 539.2 ug/cm2, respectively, and 

for human skin membranes were 0.04, 0.84, and 15.6 ug/cm2, respectively. However, the 

percutaneous absorption was decreased, indicating saturated kinetics (absorption values at 

the low, mid, and high doses expressed as percent of applied dose for the rat skin 

membranes were 71%, 64%, and 23%, respectively, and for human skin membranes were 

8%, 7%, and 0.7%, respectively). 

This in vitro percutaneous absorption study in the rat is acceptable/nonguideline, but 

does not satisfy the guideline requirement for a dermal penetration study (870.7600) in 

rats. The study is a specialty study and was designed to provide only supplemental 

information to the OPPTS 870.7600 requirement. Results of this study provide 

information on the differences in dermal absorption between rat and human skin 

membranes. 

STUDY TYPE: In vitro Mammalian Cytogenetics (chromosomal aberrations) assay

in Chinese hamster CHO cells; OPPTS 870.5375 [§84-2]; OECD 

473

CITATION: Lloyd, M. (2001) Difenoconazole Technical: Induction of chromosome 

aberrations in cultured Chinese hamster ovary (CHO)cells. Covance 

Laboratories Ltd., Otley Road, Harrogate, North Yorkshire HG3 1PY, 
Page 57 of 69

England. Laboratory Project ID: Covance Number 252/293, Syngenta 

Number T002874-06, December 11, 2001. MRID 46950319. Unpublished

EXECUTIVE SUMMARY: In a mammalian cell cytogenetics assay (Chromosomal 

aberrations) (MRID 46950319), Chinese hamster CHO cells in culture were exposed to 

CGA 169374 Technical (94.3% w/w, Lot No. WM806228) in DMSO for three hours at 

concentrations of 0, 21.99, 27.49, or 34.36 μg/mL without metabolic activation (S9-mix) 

and at concentrations of 0, 34.36, 53.69 or 67.11 μg/mL with S9-mix. Cells were 

harvested 17 hours following the end of exposure. Cells were exposed in a second 

confirmatory study for three hours at concentrations of 0, 21.99, 27.49 or 34.36 μg/mL

without S9-mix and for three hours at concentrations of 0, 34.36, 53.69, 67.11 or 83.89 

μg/mL with S9-mix. Cells were harvested 17 hours following exposure. Cells were 

evaluated for the presence of structural chromosomal aberrations and for numerical 

aberrations (polyploidy, endoreduplication and hyperploidy). The S9-fraction was 

obtained from Aroclor 1254 induced male Sprague-Dawley rat liver. 

CGA 169374 Technical was tested up to cytotoxic concentrations as evidenced by a doserelated reduction in mitotic activity seen with and without S9-mix. There was a 

statistically significant increase in the percentage of cells with structural chromosomal 

aberrations at a CGA 169374 Technical concentration of 34.36 μg/mL without S9-mix in 

the first study. The slides were rescored to determine if aberrations at the fragile X site 

were present. Aberrations at the fragile X site are not likely relevant to clastogenicity. 

Aberrations at the fragile X site were not found but the values obtained on rescoring were 

within the historical solvent control range. There was no clear reason given why the 

percent of aberrant cells was lower when the slides were rescored. Possibly the 

distribution of cells on the slides was uneven. The increase at this dose without S9-mix 

was not seen in the confirmatory assay and thus the increase was not considered 

biologically significant. A statistically significant increase in the percent of aberrant cells 

was seen in the first study at 67.11 μg/mL with S9-mix. The statistical significance 

remained upon rescoring and all values exceeded the historical solvent control range. No 

statistically significant increase was seen at this or a higher concentration in the 

confirmatory study with S9-mix. The failure to see a significant increase in the percent of 

aberrant cells in the confirmatory study makes the results equivocal. The solvent and 

positive controls (4-Nitroquinoline 1-oxide without S9-mix and cyclophosphamide with 

S9-mix) induced the appropriate responses. There was evidence of a weak induction of 

structural chromosomal aberrations over background in the presence of S9-mix.

This study is classified as Acceptable/Guideline and satisfies the guideline requirement 

for OPPTS 870.5375; OECD 473 for in vitro cytogenetic mutagenicity data.

STUDY TYPE: In vitro Mammalian Cytogenetics (chromosomal aberrations) assay

in Chinese hamster CHO cells; OPPTS 870.5375 [§84-2]; OECD 

473

CITATION: Ogorek, B. (2001) Difenoconazole Technical: Cytogenetic test on Chinese 
Page 58 of 69

hamster cells in vitro. Syngenta Crop Protection AG, Health Assessment 2 

Stein/Genetic Toxicology, CH-4332 Stein, Switzerland. Laboratory

Project ID: Syngenta AG Test Number 20013013, Syngenta Number 

T002875-06, December 3, 2001. MRID 46950321. Unpublished

EXECUTIVE SUMMARY: In a mammalian cell cytogenetics assay (Chromosomal 

aberrations) (MRID 46950321), Chinese hamster CHO cells in culture were exposed to 

CGA 169374 Technical (94.3% w/w, Lot No. WM806228) in DMSO for three hours at 

concentrations of 0, 26.3, 39.5 or 59.3 μg/mL without metabolic activation (S9-mix) and 

at concentrations of 0, 11.7 or 17.6 μg/mL with S9-mix. Cells were harvested 18 hours 

following the end of exposure. Cells were exposed in a second confirmatory study for 21 

hours at concentrations of 0, 2.3, 5.2 or 11.7 μg/mL without S9-mix and for three hours at 

concentrations of 0, 7.8, 11.7 or 17.6 μg/mL with S9-mix. Cells were harvested 

immediately following the 21-hour exposure and 18 hours after the three-hour exposure. 

Cells were evaluated for the presence of structural chromosomal aberrations and for 

polyploidy. The S9-fraction was obtained from Aroclor 1254 induced male 

HanIbm:WIST(SPF) rat liver. 

CGA 169374 Technical was tested up to cytotoxic concentrations as evidenced by a doserelated reduction in mitotic activity seen with and without S9-mix. There was a 

statistically significant increase in the percentage of CHO cells with structural 

chromosomal aberrations at a CGA 169374 Technical concentration of 59.3 μg/mL

without S9-mix in the original study when aberrations at the fragile X site were included 

but not when they were excluded. Aberrations at the fragile X site are not likely relevant 

to clastogenicity. No statistically significant increase in the percent of aberrant cells was 

seen in the original study with S9-mix. An increase in the percent of aberrant cells was

seen in the confirmatory study at 17.6 μg/mL with S9-mix and the increase was 

statistically significant (p≤0.001) when aberrations at the fragile X site were excluded. 

The value of 6.5% aberrant cells exceeded the value of >6% set as a criterion for a 

positive effect in the testing laboratory. The failure to see a significant increase in the 

percent of aberrant cells in the original study makes the results equivocal. No statistically

significant increase in the percentage of aberrant cells was seen at any of the three test 

material concentrations without S9-mix in the confirmatory study. The solvent and 

positive controls (Mitomycin C without S9-mix and Cyclophosphamide with S9-mix) 

induced the appropriate responses. There was evidence of a weak induction of 

structural chromosomal aberrations over background.

This study is classified as Acceptable/Guideline and satisfies the guideline requirement 

for OPPTS 870.5375; OECD 473 for in vitro cytogenetic mutagenicity data. 

STUDY TYPE:In vitro Mammalian Cytogenetics (chromosomal aberrations) assay

in human lymphocytes; OPPTS 870.5375 [§84-2]; OECD 473

CITATION: Fox, V. (2001) Difenoconazole Technical: In vitro cytogenetic assay in 

human lymphocytes. Central Toxicology Laboratory, Alderley
Page 59 of 69

Park/Macclesfield, Cheshire, UK SK10 4TJ. Laboratory Project ID: CTL

Number SV1090, Syngenta Number T002876-06, August 29, 2001. MRID 

46950323. Unpublished

EXECUTIVE SUMMARY: In a mammalian cell cytogenetics assay (Chromosomal 

aberrations) (MRID 46950323), human lymphocytes in culture were exposed to CGA 

169374 Technical (94.3% w/w, Lot No. WM806228) in DMSO for three hours at 

concentrations of 0, 5, 30 or 75 μg/mL without metabolic activation (S9-mix) and at 

concentrations of 0, 5, 30 or 62 μg/mL with S9-mix. Cells were harvested 17 hours 

following the end of exposure. Cells were exposed in a second experiment for 20 hours 

at concentrations of 0, 1, 5 or 10 μg/mL without S9-mix and for three hours at 

concentrations of 0, 5, 30 or 50 μg/mL with S9-mix. Cells were harvested immediately

following the 20-hour exposure and 17 hours after the three-hour exposure. Cells were 

evaluated for the presence of structural chromosomal aberrations. The S9-fraction was 

obtained from Phenobarbital + β-naphthoflavone induced male Sprague-Dawley rat liver. 

CGA 169374 Technical was tested up to cytotoxic concentrations as evidenced by a doserelated reduction in mitotic activity seen with and without S9-mix. No statistically

significant increases in the percentage of cells with structural aberrations, excluding gaps, 

over the solvent control values were seen at any test material concentration with or 

without S9-mix in the first experiment or without S9-mix in the second experiment. A 

statistically significant increase over the solvent control value was seen at 5μg/mL with 

S9-mix in the second experiment; however, the increase was not considered biologically

significant because the value (4.00%) was within the historical solvent control range, the 

values at the two higher concentrations were not significantly increased and no increase 

was seen in the first experiment. The solvent and positive controls (Mitomycin C without 

S9-mix and Cyclophosphamide with S9-mix) induced the appropriate responses. There 

was no evidence of structural chromosomal aberrations induced over background.

This study is classified as Acceptable/Guideline and satisfies the guideline requirement 

for OPPTS 870.5375; OECD 473 for in vitro cytogenetic mutagenicity data.

DIFENOCONAZOLE METABOLITES:

STUDY TYPE: In vitro Bacterial Gene Mutation (Bacterial system, Salmonella 

typhimurium and Escherichia coli)/ mammalian activation gene 

mutation assay; OPPTS 870.5100 [§84-2]; OECD 471 (formerly

OECD 471 & 472).

CITATION: Nakajima, M. (1991) CGA189138 (metabolite of difenoconazole): reverse 

mutation assay of CGA189138. Biosafety Research Center; Foods, Drugs 

and Pesticides (An-Pyo Center); 582-2, Arahama Shioshinden; FukudeCho Iwata-Gun.; Shizuoka 437-12; Japan. Laboratory Project ID: BRC 

Number 1809, October 21, 1991. MRID 46950314. Unpublished.
Page 60 of 69

EXECUTIVE SUMMARY: In a reverse gene mutation assay in bacteria (MRID 

46950314), strains TA98, TA100, TA1535 and TA1537 of S. typhimurium and strain 

WP2 uvrA of E. coli were exposed to CGA-189138, a metabolite of difenoconazole,

(97.8% a.i., lot number 910806) dissolved in DMSO in two independent assays using a 

20-minute preincubation procedure and duplicate plating. In the first mutagenicity assay, 

which was alternatively called the pilot assay and the dose-finding assay, concentrations 

of 0, 51.2, 128, 320, 800, 2000 or 5000 μg/plate were tested with and without S9-mix. In

the second assay, which was called the main assay, concentrations of 0, 31.3, 62.5, 125, 

250, 500 or 1000 μg/plate were tested in the absence of S9-mix in strains TA100 and 

TA1537 and in the presence of S9-mix in all Salmonella strains; concentrations of 0, 

62.5, 125, 250, 500, 1000 or 2000 μg/plate were tested in the absence of S9-mix in strains 

TA1535, WP2 uvrA and TA98 and in the presence of S9-mix in strain WP2 uvrA. The S9 

fraction was obtained from phenobarbital and 5,6-benzoflavone-induced male SpragueDawley rat liver.

CGA-189138 was tested at concentrations up to the limit concentration for the assay in 

the pilot assay, and many of the higher concentrations tested in both assays showed 

cytotoxicity and sometimes also insolubility. In the absence of S9-mix in the pilot assay, 

the test material was cytotoxic, as judged by stereomicroscopic examination of the 

bacterial lawns, at concentrations of 800 μg/plate and higher in strains TA100 and 

TA1537 and at concentrations of 2,000 μg/plate and higher in strains TA1535, WP2 uvrA

and TA98. In the presence of S9-mix in the pilot assay, the test material was cytotoxic at 

concentrations of 800 μg/plate and higher in all four Salmonella strains and at 

concentrations of 2,000 μg/plate and higher in strain WP2 uvrA. In the absence of S9-mix 

in the main assay, the test material was cytotoxic at concentrations of 500 μg/plate and 

higher in strain TA100, at concentrations of 1,000 μg/plate and higher in strains TA1535 

and TA98, and at the maximum concentrations tested in strains WP2 uvrA and TA1537. 

In the presence of S9-mix in the main assay, the test material was cytotoxic at 

concentrations of 500 μg/plate and higher in strains TA100, TA1535 and TA1537 and at 

the maximum concentrations tested in strains WP2 uvrA and TA98. At cytotoxic 

concentrations there was often also a marked decrease in the number of revertant colonies 

found. In the pilot assay, precipitation of the white powdery test material was observed on 

the surface of the agar plates at the time of colony counting at concentrations of 5,000 

μg/plate in the absence of S9-mix and at concentrations of 2,000 μg/plate and above in 

the presence of S9-mix. In the main assay, such precipitation was observed only in the 

presence of S9-mix and at the highest concentration tested in strain WP2 uvrA. The 

number of revertants per plate was not increased over the concurrent solvent control value 

at any test material concentration, with or without S9-mix, in any tester strain. The 

solvent and positive controls induced the appropriate responses in the corresponding 

strains. There was no evidence of induced mutant colonies over background.

This study is classified as Unacceptable/Guideline and does not satisfies the 

requirements for Test Guideline OPPTS 870.5100; OECD 471 for in vitro mutagenicity

(bacterial reverse gene mutation) data. Five strains of S. typhimurium were not used in 

the assay. The study can not be upgraded.
Page 61 of 69

STUDY TYPE: In vitro Bacterial Gene Mutation (Bacterial system, Salmonella 

typhimurium and Escherichia coli)/ mammalian activation gene 

mutation assay; OPPTS 870.5100 [§84-2]; OECD 471 (formerly

OECD 471 & 472).

CITATION: Nakajima, M. (1991) CGA205374 (metabolite of difenoconazole): reverse 

mutation assay of CGA205374. Biosafety Research Center; Foods, Drugs 

and Pesticides (An-Pyo Center); 582-2, Arahama Shioshinden; FukudeCho Iwata-Gun.; Shizuoka 437-12; Japan. Laboratory Project ID: BRC 

Number 1746, August 14, 1991. MRID 46950315. Unpublished.

EXECUTIVE SUMMARY: In a reverse gene mutation assay in bacteria (MRID 

46950315), strains TA98, TA100, TA1535 and TA1537 of S. typhimurium and strain 

WP2 uvrA of E. coli were exposed to CGA-205374, a metabolite of difenoconazole, 

(99.3% a.i., lot number 9106054) dissolved in DMSO in two independent assays using a 

20-minute preincubation procedure and duplicate plating. In the first mutagenicity assay, 

which was alternatively called the pilot assay and the dose-finding assay, concentrations 

of 0, 51.2, 128, 320, 800, 2000 or 5000 μg/plate were tested with and without S9-mix. In

the second assay, which was called the main assay, concentrations of 0, 156, 313, 625, 

1250, 2500 or 5000 μg/plate were tested with and without S9-mix. The S9 fraction was 

obtained from phenobarbital and 5,6-benzoflavone-induced male Sprague-Dawley rat 

liver.

CGA-205374 was tested at concentrations up to the limit concentration for the assay, but 

the effective concentrations tested were limited by insolubility. Evidence of cytotoxicity, 

which was collected by stereomicroscopic examination of the bacterial lawns, was seen 

only in strain TA1537 at the maximum concentration tested, and then only in the main 

assay in the presence of S9-mix. The test material was quite insoluble, with cloudiness of 

the preincubation mixture being observed even at 128 μg/plate. The white powdery

precipitate of the test material was observed on the surface of the agar plates at the time 

of colony counting at concentrations of 320 μg/plate and higher in the pilot assay in the 

absence of S9-mix and at concentrations of 800 μg/plate and higher in the presence of S9-

mix. In the main assay, this precipitate was noted at concentrations of 313 μg/plate and 

higher both in the presence and absence of S9-mix. This precipitate became heavy enough 

to make it difficult to observe the bacterial lawn at concentrations of 1250 μg/plate or 

higher in the absence of S9-mix and at the concentration of 5000 μg/plate in the presence 

of S9-mix. The number of revertants per plate was not increased over the concurrent 

solvent control value at any test material concentration, with or without S9-mix, in any

tester strain. The solvent and positive controls induced the appropriate responses in the 

corresponding strains. There was no evidence of induced mutant colonies over 

background.

This study is classified as Unacceptable/Guideline and does not satisfies the 

requirements for Test Guideline OPPTS 870.5100; OECD 471 for in vitro mutagenicity
Page 62 of 69

(bacterial reverse gene mutation) data. Five strains of S. typhimurium were not used in 

the assay. The study can not be upgraded.

STUDY TYPE: In vitro Bacterial Gene Mutation (Bacterial system, Salmonella 

typhimurium and Escherichia coli)/ mammalian activation gene 

mutation assay; OPPTS 870.5100 [§84-2]; OECD 471 (formerly

OECD 471 & 472).

CITATION: Nakajima, M. (1991) CGA205375 (metabolite of difenoconazole): reverse 

mutation assay of CGA205375. Biosafety Research Center; Foods, Drugs 

and Pesticides (An-Pyo Center); 582-2, Arahama Shioshinden; FukudeCho Iwata-Gun.; Shizuoka 437-12; Japan. Laboratory Project ID: BRC 

Number 1747, August 14, 1991. MRID 46950317. Unpublished.

EXECUTIVE SUMMARY: In a reverse gene mutation assay in bacteria (MRID 

46950317), strains TA98, TA100, TA1535 and TA1537 of S. typhimurium and strain 

WP2 uvrA of E. coli were exposed to CGA-205375, a metabolite of difenoconazole, 

(99.8% a.i., lot number 9106055) dissolved in DMSO in two independent assays using a 

20-minute preincubation procedure and duplicate plating. In the first mutagenicity assay, 

which was alternatively called the pilot assay and the dose-finding assay, concentrations 

of 0, 51.2, 128, 320, 800, 2000 or 5000 μg/plate were tested with and without S9-mix. In

the second assay, which was called the main assay, concentrations of 0, 2.50, 5.00, 10.0, 

20.0, 40.0 or 80.0 μg/plate were tested in the absence of S9-mix in all strains; 

concentrations of 0, 5.00, 10.0, 20.0, 40.0, 80.0 or 160 μg/plate were tested in the 

presence of S9-mix in strains TA100 and TA1535; concentrations of 0, 10.0, 20.0, 40.0, 

80.0, 160 or 320 μg/plate were tested in the presence of S9-mix in strains WP2 uvrA and 

TA1537; and concentrations of 0, 2.50, 5.00, 10.0, 20.0, 40.0, or 80.0 μg/plate were 

tested in the presence of S9-mix in strain TA98. The S9 fraction was obtained from 

phenobarbital and 5,6-benzoflavone-induced male Sprague-Dawley rat liver.

CGA-205375 was tested at concentrations up to the limit concentration for the assay in 

the pilot assay. Most of the concentrations in that assay showed cytotoxicity and some of 

the higher ones also showed insolubility. Some of the higher concentrations in the main 

assay, which used much lower concentrations, also showed cytotoxicity. In the absence of 

S9-mix in the pilot assay, the test material was cytotoxic, as judged by stereomicroscopic 

examination of the bacterial lawns, at all concentrations in strains TA100 and TA1537 

and at concentrations of 128 μg/plate and higher in strains TA1535, WP2 uvrA and 

TA98. In the presence of S9-mix in the pilot assay, the test material was cytotoxic at all 

tested concentrations in strain TA98, at concentrations of 128 μg/plate and higher in 

strains TA100 and TA1535, and at concentrations of 320 μg/plate and higher in strains 

WP2 uvrA and TA1537. In the absence of S9-mix in the main assay, the test material was 

cytotoxic at concentrations of 40.0 μg/plate and higher in strain TA100 and at the highest 

tested concentration in the other strains. In the presence of S9-mix in the main assay, the 

test material was cytotoxic at concentrations of 40.0 μg/plate and higher in strain TA98, 

at concentrations of 80.0 μg/plate and higher in strain TA100, at concentrations of 160 
Page 63 of 69

μg/plate and higher in strain TA1537 and at the maximum concentrations tested in strains 

TA1535 and WP2 uvrA. At cytotoxic concentrations there was often also a marked 

decrease in the number of revertant colonies found. Because cytotoxicity was excessive at 

most concentrations, the pilot assay provided only slight useful information on 

mutagenesis in most strains. In the pilot assay, the needle crystalline precipitate of the test 

material was observed on the surface of the agar plates at the time of colony counting at 

concentrations of 800 μg/plate and above in the absence of S9-mix and at concentrations 

of 2,000 μg/plate and above in the presence of S9-mix. No precipitation was observed at 

any of the much lower concentrations tested in the main assay. The number of revertants 

per plate was not increased over the concurrent solvent control value at any test material 

concentration, with or without S9-mix, in any tester strain. The solvent and positive 

controls induced the appropriate responses in the corresponding strains. There was no 

evidence of induced mutant colonies over background.

This study is classified as Unacceptable/Guideline and does not satisfies the 

requirements for Test Guideline OPPTS 870.5100; OECD 471 for in vitro mutagenicity

(bacterial reverse gene mutation) data. Five strains of S. typhimurium were not used in 

the assay. The study can not be upgraded.
Page 64 of 69

Appendix 3. Proposed Metabolic Pathway for difenoconazole in Rats
Page 65 of 69
Page 66 of 69

Appendix 4 Environmental Fate Degradates

Table 13.0c. Summary of Difenoconazole Major Degradates and Maximum Percent Formation Observed in the Laboratory and Field Studies.

Degradate 1

Max Degradate Concentration (% of applied) and Time (days) to Max Concentration Analyzed Degradates

Lab 

Accumulation

in Fish

Aqueous 

Photolysis 2,3,4 Aerobic Soil

Anaerobic 

Aquatic

Aerobic 

Aquatic TFD 5

Ground 

Water 

CGA 205375 51-64% 3.8% (4) 14.8% (360)* 12.6% (175) 11.6% (90) 4.5% (121)A

5.3% (364)B

3.5% (123)C

6.9% (182) D

No study

CGA 205374 1.1% (14) 2.1 % (272) 0.8% (247)

CGA 71019 20.6% (190) 35.9% (350)*

CGA-142856 41.8% (30)4

*

CGA-107069/

CGA-71019

12.27% (30) 4*

12.9% (9) 4

1 Refer to Table I-2 for name and structure; 2 Difenoconazole was stable under hydrolysis; 3 No meaningful amount of degradates were formed in soil 

photolysis study (≤ 0.2% and only single replicates); 4 In sterile natural water (MRID 46950105 and MRID 42245128); 5 % of the total applied difenoconazole, based on 

four applications; Aunder bare soil conditions in GA (MRID 46950126); Bunder potato production condition in ND (MRID 46950129); Cunder a bare plot of loam soil 

in CA (MRID 46950129); Din CA bare loamy sand soil (MRID 42245140); and * The max concentration was observed in the last sampling interval. 
Page 67 of 69

Table 13.0d. Chemical Structures of Difenoconazole and Degradation Products Detected in Submitted Environmental Fate Studies.

Name(s) Structure

Known Chemical 

and Fate 

Parameters

CGA-169374

Difenoconazole

1-[2-[2-Chloro-4-(4-

chlorophenoxy)phenyl]-4-methyl-1,3-

dioxolan-2-ylmethyl]-1H-1,2,4-triazole.

1-[[2-[2-Chloro-4-(4-

chlorophenoxy)phenyl]-4-methyl-1,3-

dioxolan-2-yl]methyl]-1H-1,2,4-triazole.

1-(2-[4-(4-Chlorophenyoxy)-2-

chlorophenyl-(4-methyl-1,3-dioxolan-2-yl)-

methyl])-1H-1,2,4-triazole.

CAS #: 119446-68-3

Cl

O

Cl

O

O

CH3

H2C

N

N N
Page 68 of 69

Name(s) Structure

Known Chemical 

and Fate 

Parameters

CGA-205374 [CGA-176459]

1-[2-Chloro-4-(4-chlorophenoxy)-phenyl]-

2-[1,2,4]triazol-1-yl-ethanone

1-[2-Chloro-4-(4-chlorophenoxy)phenyl]-2-

(1H-1,2,4-triazol-1-yl)-ethanone

CAS #: 136815-80-0

O

N

N

N

O Cl

Cl

CGA-205375 [CGA-211391]

1-[2-Chloro-4-(4-chlorophenoxy)-phenyl]-

2-[1,2,4]triazol-1-yl-ethanol 

alpha-[2-Chloro-4-(4-

chlorophenoxy)phenyl]-1H-1,2,4-triazole1-ethanol.

CAS #: 117018-19-6

N

N

N

O Cl

Cl

OH

Mobility data 

available

CGA-142856

[1,2,4]Triazol-1-yl-acetic acid

1H-1,2,4-Triazole-1-acetic acid.

CAS #: 28711-29-7

HO

O

N

N

N DW assessment 

completed in 2006

CGA-71019

1-H-(1,2,4)-Triazole 

1H-1,2,4-Triazole

4H-[1,2,4]Triazole

CAS #: 288-88-0

N

HN N DW assessment 

completed in 2006

CGA-107069

1-H-(1,2,4)-Triazole-1-methanol 

CAS #: 74205-82-6

C

H2

N

N

N HO
Page 69 of 69

Name(s) Structure

Known Chemical 

and Fate 

Parameters

CGA-131013

2-Amino-3-[1,2,4]triazol-1-yl-propionic 

acid

alpha-Amino-1H-1,2,4-triazole-1-propanoic

acid

CAS #: 86362-20-1

OH

O

NH2

N

N

N