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sr-4,.~4'. UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

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MEMORANDUM 

OFFICE OF CHEMICAL 

SAFETY AND 

POLLUTION PREVENTION 

Date: July 18, 2013 

SUBJECT: Isopyrazam: Human Health Risk Assessment for the Establishment of Tolerances 

with No U.S. Registrations for Isopyrazam in/on Imported Apple and Peanut. 

PC Code: 129222 DP Barcode: 409594 

Decision No.: 465123 Registration No.: Not Applicable 

Petition No.: 2E8039 Regulatory Action: Tolerance Petition 

Risk Assessment Type: Single Chemical Aggregate Case No.: Not Applicable 

TXR No.: Not Applicable CAS No.: 881685-58-1 

MRID No.: Not Applicable 40 CFR: 180.654 ~ . 

FROM: Bonnie Cropp-Kohlligian, Environmental Scien;.;:::]:Sm ('l!.<loO -~ 1 t 

Susan V. Hummel, Chemist ~ ~ 

Risk Assessment Branch IV (RABIV) 

Marquea D. King, Ph.D., Toxicologis~~h 

Health Effects Division (HED) (7509P) , 

THROUGH: 

RABIV

DonnaS. 

, HED 

Davis, 

(7509P) 

Acting Branch hief~~~ 

TO: Shaunta Hill/Driss Benmhend (RM20) 

Fungicide Branch 

Registration Division (7505P) 

This document provides the Health Effects Division's (RED's) risk assessment conducted for the 

request for tolerances with no U.S. registrations for isopyrazam in/on apples imported from Chile 

and peanuts imported from Nicaragua. 

Page 1 of67 
Table of Contents 

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

2.0 HED Recommendations .................................................................................................... 5 

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

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

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

2.2.2 Analytical Reference Standard .................................................................................. 6 

2.2.3 Recommended Tolerances .......................................... ............................................... 6 

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

2.2.5 International Harmonization ..................................................................................... 7 

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

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

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

2.3.3 Recommendation from Residential Assessment ...................................................... 8 

3.0 Introduction ........................................................................................................................ 9 

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

3.2 Physical/Chemical Characteristics ............................................................................. 11 

3.3 Pesticide Use Pattern ..................................................................................................... 11 

3.4 Anticipated Exposure Pathways ................... .............................................................. 13 

3.5 Consideration of Environmental Justice .................................................................... 14 

4.0 Hazard Characterization and Dose-Response Assessment.. ........................................ 14 

4.1 Toxicology .Studies Available for Analysis ................................................................. 14 

4.2 Absorption, Distribution, Metabolism, & Elimination (ADME) ............................. 15 

4.3 Toxicological Effects .................................................................................................... 15 

4.4 Safety Factor for Infants and Children (FQPA Safety Factor) ............................... 16 

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

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

4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal.. ...... 18 

4.4.4 Residual Uncertainty in the Exposure Database ................................................... 18 

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

4.5.1 Dose-Response Assessment ...................................................................................... 18 

4.5.2 Recommendation for Combining Routes of Exposures for Risk Assessment ..... 19 

4.5.3 Cancer Classification and Risk Assessment Recommendation ............................ 19 

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

Risk Assessment ...................................................................................................................... 20 

5.0 Dietary Exposure and Risk Assessment .............. ........................................................... 20 

5.1 Metabolite/Degradate Residue Profile ....................................................................... 20 

5.1.1 Summary of Plant and Animal Metabolism Studies ............................................. 20 

5.1.2 Summary of Environmental Degradation .............................................................. 21 

5.1.3 Comparison of Metabolic Pathways ....................................................................... 21 

5.1.4 Residues of Concern Summary and Rationale ...................................................... 21 

5.2 Food Residue Profile .................................................................................................... 24 

5.3 Water Residue Profile .................................................................................................. 26 

Page 2 of67 
Page 3 of 67

5.4 Dietary Risk Assessment.............................................................................................. 26

5.4.1 Description of Residue Data Used in Dietary Assessment.................................... 27

5.4.2 Percent Crop Treated Used in Dietary Assessment .............................................. 27

5.4.3 Acute Dietary Exposure and Risk........................................................................... 27

5.4.4 Chronic Dietary Risk Assessment........................................................................... 27

5.4.5 Cancer Dietary Risk Assessment............................................................................. 27

5.4.6 Summary Table......................................................................................................... 28

6.0 Residential (Non-Occupational) Exposure/Risk Characterization ............................. 28

7.0 Aggregate Exposure/Risk Characterization.................................................................. 28

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

9.0 Occupational Exposure/Risk Characterization ............................................................ 28

10.0 References......................................................................................................................... 29

Appendix A. Toxicology Profile and Executive Summaries .................................................. 31

Appendix B. Metabolism............................................................................................................ 65

Appendix C. Physical/Chemical Properties............................................................................. 67
Page 4 of 67

1.0 Executive Summary

Isopyrazam is a pyrazole carboxamide fungicide comprised of a mixture of two diasterioisomers 

designated syn-(SYN534969; enantiomer, 50:50 mixture) and anti-(SYN534968; enantiomer, 50:50 

mixture) isomers; both of which are biologically active. There are multiple mixtures with varying 

syn:anti isomer compositions ranging from 70:30 to 100:0. 

Isopyrazam is not currently registered for use in the U.S.; however, a tolerance with no U.S. 

registration is currently established for residues of isopyrazam in/on banana at 0.05 ppm. Syngenta 

Crop Protection, Inc. (hereafter referred to as Syngenta or the petitioner) has petitioned to establish 

tolerances with no U.S. registrations for residues of isopyrazam in/on apple imported from Chile at 

0.6 ppm and in/on peanut imported from Nicaragua at 0.01 ppm.

The toxicity database is considered adequate for the estimation of human health risk and assessment 

of children’s susceptibility under FQPA for isopyrazam for existing and proposed uses of 

isopyrazam. The primary target organ for isopyrazam toxicity is the liver based on subchronic and 

chronic oral studies in the rat, mouse, rabbit and dog. The principal effects observed in these studies 

are increased organ weight and centrilobular hepatocyte hypertrophy. Liver toxicity is usually 

accompanied by reductions in bodyweight and food consumption. Isopyrazam does not cause 

reproductive toxicity. Developmental effects (eye abnormalities) were observed in the absence of 

maternal toxicity in two range finding developmental toxicity studies in rabbits providing some 

evidence of sensitivity/susceptibility following pre- and/or post-natal exposure; however, these 

effects are well characterized, there is a clear NOAEL for the eye abnormalities, and the Agency is 

proposing to regulate at a level which is protective of these effects. Developmental studies in rats

produced developmental effects but only at doses that were also maternally toxic. Acute and 

subchronic oral neurotoxicity studies in rats show no evidence of neurotoxicity. Effects 

characteristic of neurotoxicity (side-to-side head wobble, ataxia, reduced stability) were observed on 

day two in one subchronic oral study in dogs and at week four in a second subchronic dog study. 

These effects were not observed in the chronic dog study. There is significant uncertainty regarding 

whether there is a neurotoxicological basis for the effects seen in the subchronic dog studies since 

the studies were not specifically conducted to identify neurotoxic potential and detailed clinical and 

histopathological analyses for neurotoxic effects were not performed. There is no evidence of 

immunotoxicity based on a subchronic immunotoxicity study in rats. Based on the completeness of 

the toxicity database, the selection of risk assessment endpoints that are protective of developmental 

effects which are the only evidence of sensitivity/susceptibility, and the inclusion of exposure values 

that are not likely to underestimate exposure in the risk assessment, there are no residual 

uncertainties with regard to pre- and/or postnatal toxicity. Therefore, the FQPA safety factor was 

reduced to 1X. 

Isopyrazam is of low acute toxicity by the oral, dermal and inhalation routes and is not a skin or eye 

irritant. Subchronic and chronic oral studies conducted with varying isomer compositions of 

isopyrazam indicate that the toxicity of these compositions is qualitatively and quantitatively very 

similar.
Page 5 of 67

The Cancer Assessment Review Committee (CARC) classified isopyrazam as “Likely to be 

Carcinogenic to Humans” based on increased liver and uterine endometrial epithelial tumors in 

female rats and increased thyroid follicular cell tumors in male rats. The CARC recommended 

linear low dose extrapolation for cancer risk assessment. A cancer slope factor (Q1*) of 0.00629 

(mg/kg/day)-1 was used for the quantification of human cancer risk.

Toxicological points of departure (PODs) were selected for dietary exposure scenarios only. The

acute RfD was selected from a subchronic toxicity study in dogs based on clinical signs of toxicity

seen following a single dose. The chronic RfD was selected from a chronic toxicity/carcinogenicity 

feeding study in rats based on liver and body weight effects. Since isopyrazam is not registered for 

use in the U.S., PODs for occupational and residential exposures have not been determined. An 

uncertainty factor of 100X was applied to non-cancer endpoints selected for all dietary exposures

(10X for interspecies extrapolation, 10X for intraspecies variation).

Pending modifications to the directions for use, the residue chemistry database is complete for the 

proposed uses of isopyrazam on apples imported from Chile and peanuts imported from Nicaragua. 

The nature of the residue in plant and livestock is adequately understood for the current petition. An 

adequate enforcement method is available. Apple and peanut magnitude of the residue data (field 

trial and processing studies) are adequate. Tolerances in processed apple and peanut commodities 

are not needed. There is no expectation of finite residues of isopyrazam in livestock commodities.

Since existing and proposed uses of isopyrazam are all non-domestic, there is no domestic potential 

for drinking water, occupational, and/or residential exposures. Therefore, these exposure pathways 

were not assessed. Furthermore, an aggregate assessment is not relevant for the existing and 

proposed uses of isopyrazam since the only anticipated exposure is through the dietary pathway.

Screening level acute, chronic and cancer dietary (food only) assessments were conducted for 

isopyrazam residues of concern from existing and proposed uses. Acute and chronic dietary risk 

estimates are below the level of concern for all population subgroups. At the 95th percentile, the 

acute exposure results in an estimated dietary risk equivalent to ≤4.2% of the acute population 

adjusted dose (aPAD) for all populations. The estimated non-cancer chronic dietary risk is 

equivalent to ≤6.1% of the chronic population adjusted dose (cPAD) for all populations. The most 

highly exposed subpopulation was children 1-2 years old for both acute and non-cancer chronic 

estimated dietary risks. The resulting estimated cancer dietary risk is 2 x 10-6for the general U.S. 

population.

2.0 HED Recommendations

HED recommmends in favor of the establishment of tolerances without U.S. registrations for 

residues of isopyrazam in/on apple and peanut provided the petitioner supplies a reference standard 

to the EPA National Pesticide Standards Repository (see section 2.2.2) and complies with the 

tolerance recommendations (see sections 2.2.3 and 2.2.4) and directions for use modifications (see

section 2.3.1).
Page 6 of 67

2.1 Data Deficiencies

Pending modifications to the directions for use, there are no data deficiencies identified for this 

petition. However, while tolerances for livestock commodities are not needed for the current 

petition, the petitioner should be reminded of the following should future uses necessitate setting 

tolerances in livestock commodities: (1) Missing milk and meat storage stability data which are not 

required for the current petition will be critical to tolerance setting and estimating isopyrazam 

residues of concern in milk and/or meat commodities in dietary assessments; (2) If/when a poultry 

feeding study is needed, samples should be analyzed for both isopyrazam and total isopyrazam 

(isopyrazam plus its metabolites convertible to the CSAA 798670 moiety, expressed as isopyrazam); 

and (3) An enforcement method adequately validated for residues of isopyrazam in livestock 

commodities has not been submitted. A suitable enforcement method should be able to achieve 

limits of quantitation (LOQs) of 0.0025 ppm or less for each isomer. HED notes that method 

GRM006.09A (Version 2) with LOQs of 0.0025 ppm for both isomers was adequately validated as a 

data collection method in milk and meat and might be a suitable enforcement method, but additional 

method validation data are needed and the method must include two ion transitions.

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

A liquid chromatography with tandem mass spectrometry detection (LC-MS/MS) method

(GRM006.01B) is available as an enforcement method for the determination of isopyrazam (sum of 

syn-(SYN534969) and anti-(SYN534968) isomers) in plant commodities. The syn-(SYN534969) 

and anti-(SYN534968) isomers are detected as 2 peaks with different retention times. The final 

determination monitors two MS/MS ion transitions, m/z 360.2 → 320.4 and m/z 360 → 244, for 

both isomers. The limit of quantification of the method is 0.005 ppm for each isomer. Additionally, 

a modified version of the German multiresidue method S19 is available for tolerance enforcement.

2.2.2 Analytical Reference Standard

An analytical reference standard for isopyrazam is currently available in the EPA National Pesticide 

Standards Repository (T. Cole, email of 2/13/13), but will expire 8/31/13. The standard must be 

resubmitted or recertified.

2.2.3 Recommended Tolerances

An error was made in the tolerance expression with the earlier tolerance petition for isopyrazam on 

banana (PP#9E7606). The enforcement method measures the syn-isomer and the anti-isomer 

separately and tolerances are/will be derived by summing these two isomers. Hence, in accordance 

with HED's Interim Guidance on Tolerance Expressions (Memo from S. Knizner dated 5/27/09), the 

correct tolerance expression for isopyrazam should be the following:

“Tolerances are established for residues of the fungicide isopyrazam, including its 
Page 7 of 67

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

tolerance levels specified below is to be determined by measuring only isopyrazam (3-

(difluoromethyl)-1-methyl-N-[1,2,3,4-tetrahydro-9-(1-methylethyl)-1,4-methano-naphthalen5-yl]-1H-pyrazole-4-carboxamide), as the sum of its syn-isomer 

(3-(difluoromethyl)-1-methyl-N-[(1RS, 4SR, 9RS)-1,2,3,4-tetrahydro-9-(1-methylethyl)-1,4-

methanonaphthalen-5-yl]-1H-pyrazole-4-carboxamide) and anti-isomer 

(3-(difluoromethyl)-1-methyl-N-[(1RS, 4SR, 9SR)-1,2,3,4-tetrahydro-9-(1-methylethyl)-1,4-

methano-naphthalen-5-yl]-1H-pyrazole-4-carboxamide) in or on the commodity.”

Table 2.2.3. Tolerance Summary for Isopyrazam

Commodity Proposed 

Tolerance (ppm)

Recommended 

Tolerance (ppm)

Correct Commodity Definition

Comments

Apple 0.6 0.70 Apple. The tolerance listing should note that 

there is no U.S. registration on apple.

Recommended tolerance level is based on data 

reflecting a 21-day PHI and is harmonized with 

the pending EU MRL in/on pome fruit.

Peanuts 0.01 0.01 Peanut. The tolerance listing should note that 

there is no U.S. registration on peanut.

2.2.4 Revisions to Petitioned-For Tolerances

For the purposes of harmonization with a pending EU MRL for residues of isopyrazam in/on pome 

fruit (0.7 mg/kg), HED is recommending a tolerance of 0.70 ppm in/on apple. Hence, Section F of 

the amended petition (submitted with Syngenta Letter to RD dated 6/18/13 in response to EPA 

Deficiency Letter dated 4/11/13) should be further amended to specify the recommended tolerance 

level for apple. In addition, there are several minor changes which are required. Section F should 

indicate that the petitioned-for tolerances are new tolerances and not increases of existing tolerances. 

The tolerance expression must be amended to be consistent with the recommendation specified in 

section 2.2.3. The proposed commodity, Peanuts, must be corrected to Peanut, consistent with the 

correct commodity definition. 

2.2.5 International Harmonization

No Codex, Canadian, or Mexican maximum residue limits (MRLs) have been established for 

residues of isopyrazam in/on apple or peanut commodities. However, recently the European Food 

Safety Authority (EFSA) has proposed a 0.7 mg/kg MRL in the European Union (EU) for residues 

of isopyrazam in/on pome fruits (EFSA Journal 2013;11(4):3165.) based on field trial data from 

Europe reflecting the same use pattern as the apple field trials data submitted in support of the 

subject petition. Hence, for the purposes of harmonization, HED will recommend in favor of a 0.70 

ppm tolerance for residues of isopyrazam in/on apple consistent with the pending EU MRL in/on 

pome fruit.
Page 8 of 67

2.3 Label Recommendations

2.3.1 Recommendations from Residue Reviews

HED recommends that Section B of the amended petition (submitted with Syngenta Letter to RD 

dated 6/18/13 in response to EPA Deficiency Letter dated 4/11/13) concerning the use on peanut in 

Nicaragua and the proposed Reflect 12.5 EC label be further amended to specify a minimum spray 

volume equivalent to 2 gal/A and a restriction on the feeding of isopyrazam-treated peanut hay to 

livestock.

2.3.2 Recommendations from Occupational Assessment

None

2.3.3 Recommendation from Residential Assessment

None
Page 9 of 67

3.0 Introduction

Isopyrazam (SYN520453) is a pyrazole carboxamide fungicide comprised of a mixture of two 

diasterioisomers designated syn-(SYN534969; enantiomer) and anti-(SYN534968; enantiomer) 

isomers; both of which are biologically active. A technical product for isopyrazam is not currently 

registered in the U.S. but there are multiple mixtures of the two isomers ranging from 70% syn:30% 

anti to 100% syn:0% anti. Isopyrazam is not currently registered in the U.S.; however, a tolerance 

with no U.S. registration is currently established for residues of isopyrazam in/on banana at 0.05 

ppm. Syngenta has petitioned to establish tolerances with no U.S. registrations for residues of 

isopyrazam in/on apple imported from Chile at 0.6 ppm and in/on peanut imported from Nicaragua 

at 0.01 ppm.

3.1 Chemical Identity

The chemical structure and nomenclature of isopyrazam and its residues of concern are presented in 

Table 3.1. 

Table 3.1. Test Compound Nomenclature.

Chemical structure

Common name Isopyrazam

Company experimental name SYN520453, a mixture of SYN534969 (syn-isomer; mix of two enantiomers) and 

SYN534968 (anti-isomer; mix of two enantiomers).

IUPAC name 3-(difluoromethyl)-1-methyl-N-[1,2,3,4-tetrahydro-9-isopropyl-1,4-

methanonaphthalen-5-yl)]pyrazole-4-carboxamide

CAS name 1H-Pyrazole-4-carboxamide, 3- (difluoromethyl)-1-methyl-N-[1,2,3,4-tetrahydro9-(1-methylethyl)-1,4-methanonaphthalen-5-yl]-

CAS registry number 881685-58-1 (for mixture)

End-use product (EP) None Registered in the U.S.

For use on peanut in Nicaragua: Reflect 12.5 EC (125 g ai/L)

For use on apple in Chile: Reflect 125 EC (125 g ai/L); Reflect Top SC (100 g 

ai/L)

NH

O

N

N

F

F
Page 10 of 67

Table 3.1. Test Compound Nomenclature.

Chemical structure

Common name syn-isomer and anti-isomers of isopyrazam

Company experimental name SYN534969 and SYN534968

IUPAC name syn-(SYN534969) isomer: 3-(difluoromethyl)-1-methyl-N-[(1RS, 4SR, 9RS)-

1,2,3,4-tetrahydro-9-isopropyl-1,4-methanonaphthalen-5-yl)]pyrazole-4-

carboxamide

anti-(SYN534968) isomer: 3-(difluoromethyl)-1-methyl-N-[(1RS, 4SR, 9SR)-

1,2,3,4-tetrahydro-9-isopropyl-1,4-methanonaphthalen-5-yl)]pyrazole-4-

carboxamide

CAS name syn-(SYN534969) isomer: 1H-Pyrazole-4-carboxamide, 3- (difluoromethyl)-1-

methyl-N-[(1RS, 4SR, 9RS)-1,2,3,4-tetrahydro-9-(1-methylethyl)-1,4-

methanonaphthalen-5-yl] (mix of two enantiomers).

anti-(SYN534968) isomer: 1H-Pyrazole-4-carboxamide, 3- (difluoromethyl)-1-

methyl-N-[(1RS, 4SR, 9SR)-1,2,3,4-tetrahydro-9-(1-methylethyl)-1,4-

methanonaphthalen-5-yl] (mix of two enantiomers).

CAS registry number syn-(SYN534969) isomer: 683777-13-1

anti-(SYN534968) isomer: 683777-14-2

Chemical structure

N

N

F

F

O

N

H

HO

Common name syn-isomer of tertiary alcohol metabolite of isopyrazam (CSCD460260)

Company experimental name CSCD459488

IUPAC name 3-(difluoromethyl)-1-methyl-N-[(1RS, 4SR, 9RS)-1,2,3,4-tetrahydro-9-(2-

hydroxypropan-2-yl)-1,4-methanonaphthalen-5-yl]pyrazole-4-carboxamide(mix of 

two enantiomers)

End-use product (EP) NA, Metabolite

N

H

O

N

N

F

F N

H

O

N

N

F

F

syn-isomer (SYN 534969) anti-isomer (SYN 534968)
Page 11 of 67

Table 3.1. Test Compound Nomenclature.

Chemical structure

Common name anti-isomer of tertiary alcohol metabolite of isopyrazam (CSCD460260)

Company experimental name CSCD459489

IUPAC name 3-(difluoromethyl)-1-methyl-N-[(1RS, 4SR, 9SR)-1,2,3,4-tetrahydro-9-(2-

hydroxypropan-2-yl)-1,4-methanonaphthalen-5-yl]pyrazole-4-carboxamide(mix of 

two enantiomers)

End-use product (EP) NA, Metabolite

3.2 Physical/Chemical Characteristics

A detailed description of the physicochemical properties of isopyrazam is provided in Appendix C. 

Isopyrazam is relatively insoluble in water, highly soluble in solvents and has a low vapor pressure.

However, since existing and proposed uses of isopyrazam are all non-domestic and no occupational 

or residential exposures are expected, physical and chemical properties of the compound are of 

minimal significance to the exposure assessment. 

3.3 Pesticide Use Pattern

Isopyrazam is to be used on apples in Chile and peanuts in Nicaragua. There are no 

existing/proposed uses of isopyrazam in the U.S. Table 3.3.1 provides a summary of the products 

proposed for use in this petition. Table 3.3.2 provides a summary of the directions of use from 

Section B of the amended petition (submitted with Syngenta Letter to RD dated 6/18/13 in response 

to EPA Deficiency Letter dated 4/11/13). [Note: Section B of the petition consists of specimen 

labels for Reflect 12.5 EC, Reflect 125 EC, and Reflect Top.]
Page 12 of 67

Table 3.3.1. Summary of Proposed End-Use Products and Crops Under Consideration.

Trade Name EPA Reg. No. ai Content Formulation 

Type

Target New Crops 

Identified in Section 

B of PP# 2E8039

Target Pests Label Date

Reflect Top Not Applicable

Chile label

100 g/L 

isopyrazam

40 g/L 

difenoconazole

Suspension

Concentrate 

(SC)

Apple Apple Scab

Powdery Mildew

Undated 

specimen 

label in 

Section B of 

PP# 2E8039

Reflect 125 EC Not Applicable

Chile label

125 g/L Emulsifiable 

Concentrate

(EC)

Undated 

specimen 

label in 

Section B of 

PP# 2E8039

Reflect 12.5 EC Not Applicable

Nicaragua label

125 g/L Emulsifiable

Concentrate 

(EC)

Peanut Peanut plant rust

Early leaf spot

Late leaf spot

General leaf spot

White mold

Undated 

specimen 

label in 

Section B of 

PP# 2E8039

Table 3.3.2. Summary of Proposed Directions for Use of Isopyrazam.

Applic. Timing, Type, 

Equipment.

Trade name

[ai Content and 

Formulation]

Applic. Rate 

(g ai/ha)

Max. No. Applic. 

per Season

Max. Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days)

Apples

Foliar

(ground and aerial assumed)

Use Directions: 75 cc product/100 L of water with a maximum spray volume of 1,600 L/ha

 100 cc product/100 L of water with a maximum spray volume of 1,200 L/ha

Limitations: The minimum retreatment interval (RTI) is 7-days. Apply a maximum of 2 nonsequential applications per season, alternating with fungicides with a different mode of action. 

The minimum spray volume is not specified. Use of adjuvants is not specified.

Reflect Top

[100 g/L SC] 120 2 240 63

Foliar

(ground and aerial assumed)

Use Directions: 80 cc product/100 L of water with a maximum spray volume of 1,500 L/ha

Limitations: The minimum retreatment interval (RTI) is 7-days. Apply a maximum of 2 nonsequential applications per season, alternating with fungicides with a different mode of action. 

The minimum spray volume is not specified. Use of adjuvants is not specified.

Reflect 125 EC

[125 g/L EC] 150 2 300 63

Peanut

Foliar

(ground and aerial assumed)

Use Directions: 0.8 - 1.0 L product/ha (0.56 - 0.7 L/mz; mz is a unit of area that farmers in some 

Central American Countries use equal to 7000 square meters).

Limitations: The minimum retreatment interval (RTI) is 14-days. The minimum spray volume is 

not specified. Use of adjuvants is not specified.

Reflect 12.5 EC

[125 g/L EC] 125 3 375 7
Page 13 of 67

The proposed use directions for isopyrazam specified in Section B of the amended petition 

(submitted with Syngenta Letter to RD dated 6/18/13 in response to EPA Deficiency Letter dated 

4/11/13) are adequate to allow evaluation of the supporting residue data. 

The use pattern represented in the submitted apple field trials was 3 applications of an SC 

formulation of isopyrazam at 150 g ai/ha/application (total 450 g ai/ha) using dilute spray 

volumes with a 6- to 7-day RTI and 21-day PHI. Use of an EC formulation of isopyrazam, 

concentrated spray volumes (20-100 gal/A), and/or ultra-low volumes (<10 gal/A) were not

represented. However, since the proposed uses on apple include a significantly longer PHI than 

the supporting data used to establish the apple tolerance, data reflecting the use of an EC 

formulation of isopyrazam and/or concentrated spray volumes are not needed. The directions for 

use of isopyrazam on apple in Chile are adequate. [Note: In the future, if a significantly shorter 

PHI is desired, then additional data and/or restrictive spray-volume label language may be 

needed.]

The use pattern represented in the submitted peanut field trials was 3 applications of an EC 

formulation of isopyrazam at 125 g ai/ha/application (total 375 g ai/ha) with a 12- to 14-day RTI 

and a 7-day PHI. No peanut hay data were submitted in support of the petition. HED 

recommends that Section B of the amended petition (submitted with Syngenta Letter to RD dated 

6/18/13 in response to EPA Deficiency Letter dated 4/11/13) concerning the use of Reflect 12.5 

EC be further amended to specify a minimum spray volume equivalent to 2 gal/A and a 

restriction on the feeding of isopyrazam-treated peanut hay to livestock. HED assumes that, as 

in the U.S., it is practically enforceable to restrict the feeding of peanut hay in Nicaragua. With 

regards to the recommended feeding restriction, Syngenta has informed HED (Syngenta Letter to 

RD (6/18/13) in response to EPA Deficiency Letter dated 4/11/13) that: “In Nicaragua, farmers 

either burn, disk, or feed peanut hay to livestock. There is no studies showing that the actual 

percentages of farmers that use these practices; however, farmers that use this product are 

generally more technologically advanced and they do not feed livestock. On the other hand, only 

1% of beef consumed in the U.S. is imported from Nicaragua.” HED continues to believe that a 

restriction on the feeding of isopyrazam-treated hay is advisable. However, such a restriction 

should not prove burdensome, given that the petitioner has indicated that peanut growers in 

Nicaragua that will use isopyrazam are not likely to feed livestock.

3.4 Anticipated Exposure Pathways

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

proposed new tolerances with no U.S. registrations for isopyrazam in/on apple and peanut. Since 

existing and proposed uses of isopyrazam are all non-domestic, there is no domestic potential for 

drinking water, occupational, and/or residential exposures. The only domestic potential exposure 

by humans is to isopyrazam residues of concern in food.
Page 14 of 67

3.5 Consideration of Environmental Justice

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

subgroups.

4.0 Hazard Characterization and Dose-Response Assessment

Isopyrazam is a pyrazole carboxamide. The pesticidal mode of action (MOA) of this group of 

fungicides is thought to be inhibition of succinate dehydrogenase (SDH), which is a functional 

part of the tricarboxylic acid cycle (TCA) and the mitochondrial electron transport chain. The 

toxicological effects reported in the submitted animal studies do not specifically reflect the MOA 

against the targeted pests. There are very little data available on this class of chemicals. 

However available data do not indicate that there are common or signature toxic effects 

associated with pyrazole carboxamides as a chemical class.

4.1 Toxicology Studies Available for Analysis

The studies available for consideration of isopyrazam toxicity provide a comprehensive and 

complete database. All toxicity studies required in accordance with new 40 CFR Part 158 data 

requirements have been submitted. Only dietary exposure is expected for the existing and 

proposed uses which are all non-domestic and adequate studies are available for consideration of 

this potential exposure scenario.

Subchronic and chronic oral studies conducted with isopyrazam with varying isomer 

compositions are available (i.e., 70% syn:30% anti, 89% syn:11% anti, 50% syn:50% anti, pure 

syn material and pure anti composition). These studies indicate that the toxicity of these 
Page 15 of 67

compositions is qualitatively and quantitatively very similar to the 93% syn:7% anti composition 

of isopyrazam. The studies demonstrate that the toxicity of isopyrazam is not influenced by 

epimeric composition. 

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

The oral absorption of the 93% syn:7% anti isopyrazam composition was estimated following a 

single low or high oral gavage dose to rats by measuring the radioactivity present in urine, bile, 

cage wash, feces and carcass up to 48 hours post dosing. Oral absorption is estimated to be 93-

100% of the administered dose. 

Single dose oral studies showed isopyrazam and/or its metabolites to be distributed widely 

throughout the internal organs within 2 – 10 hours. In a 14-day repeat dose study steady-state 

radioactivity concentrations were reached by day 10 all but liver, kidney and fat tissues. Levels 

of radioactivity were generally low (< 0.05 μg equiv/g in most tissues).

Isopyrazam was extensively metabolized with to up to 25 metabolites (including conjugates) 

identified. The biotransformation of isopyrazam was postulated to proceed by hydroxylation in 

the bicyclo-isopropyl region, followed by further oxidation to form the carboxylic acid and/or to 

give rise to multiple hydroxyl moieties with subsequent formation of glucuronic acid or sulphate 

conjugates. No cleavage of the molecule was observed. The major routes of biotransformation 

appeared to be independent of dose level and sex and the metabolite profile did not change 

following repeated administration. More than 90% of the administered dose was accounted for 

by identified metabolites.

Based on available data, isopyrazam has no significant bioaccumulation potential. Excretion was 

fairly rapid in the single dose oral study with the majority of the administered radioactivity being 

excreted by 48 hours post dose (mean of 89-99%). In general, unconjugated metabolites were 

eliminated in urine and conjugated metabolites in bile. Routes of excretion after repeated 

administration for 14 days were the same as those observed after single administration. A 48-

hour blood kinetics study following a single oral administration of isopyrazam showed that 

maximum plasma concentrations of radioactivity at 3-6 hours post dose with a mean elimination

half-life of 4.6-7.5 hours. Radioactivity in blood was not appreciably different from that in 

plasma, indicating that there was no selective binding of isopyrazam and/or its metabolites to 

blood cells.

The available metabolism study on the 70% syn: 30% anti isopyrazam formulation indicates that 

there are no major differences in the absorption, metabolism and excretion of the 93% syn: 7% 

anti and 70% syn: 30% anti composition materials.

4.3 Toxicological Effects

Subchronic and chronic oral toxicity studies have been conducted in the rat, mouse and dog. 

These studies consistently demonstrate that the primary target organ for isopyrazam is the liver
Page 16 of 67

(increased organ weight and centrilobular hepatocyte hypertrophy). Liver toxicity is usually 

accompanied by reductions in bodyweight and food consumption.

Isopyrazam did not cause reproductive toxicity. Effects seen in the offspring (bodyweight gain 

during lactation and increase liver weight at weaning) in the rat reproduction study occur at the

same doses that cause general toxicity in the parents. Developmental effects described as small 

eyes and/or microphthalmia were observed in both the Himalayan and New Zealand rabbit

strains. However, in the Himalayan strain the intraocular abnormalities occur in the absence of 

maternal toxicity while in the New Zealand the ocular abnormalities occurred at doses that were 

maternally toxic. Developmental effects observed in the rat (increased post-implantation loss, 

reduced fetal weight and a slight retardation of ossification) occurred at doses that also produced 

maternal toxicity. No evidence of specific neurotoxicity was seen in acute and subchronic oral 

neurotoxicity studies in rats. Effects consistent with neurotoxicity were observed on day two in 

one of four male dogs in a subchronic oral study (side-to-side head wobble, ataxia, reduced 

stability) and at week four in several males in a second subchronic dog study (sporadic buckling 

of the hind limbs, uncoordinated movements, shaking the head and ptosis). These effects were 

not observed in the chronic dog study. There is significant uncertainty regarding whether there is 

a neurotoxicological basis for the effects seen in the subchronic dog studies since the effects 

were sporadic and transient, the studies were not specifically conducted to identify neurotoxic 

potential and detailed clinical and histopathological analyses for neurotoxic effects were not 

performed. The subchronic immunotoxicity in rats provided no indications of isopyrazammediated immunotoxicity.

The carcinogenicity of isopyrazam has been investigated in rats and mice. Isopyrazam is 

carcinogenic in male and female rats. Increased incidence of uterine endometrial 

adenocarcinomas and liver hepatocellular adenomas were seen in females at an exposure level 

that also causes non-neoplastic systemic toxicity. In male rats, increased incidence of thyroid 

follicular cell adenomas and/or carcinomas was observed. Isopyrazam is not carcinogenic in the 

mouse. There is no evidence of genotoxicity, mutagenicity, or clastogenicity in in vivo and in 

vitro studies. There are no structural relationships with other known carcinogens. The HED 

Cancer Assessment Review Committee (CARC) classified isopyrazam as “Likely to be 

Carcinogenic to Humans”. A linear low-dose approach (Q1*) was used to extrapolate 

experimental animal tumor data for the quantification of human cancer risk.

Isopyrazam is of low acute toxicity by the oral, dermal and inhalation routes and is not irritating 

to the eyes and skin.

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

The FQPA factor for increased susceptibility to infant and children is reduced to 1X based on the 

following considerations:

- The toxicology data base for isopyrazam is complete and adequate for assessing 

increased susceptibility under FQPA;
Page 17 of 67

- There is no indication of increased susceptibility of fetuses to in utero and/or postnatal 

exposure in the developmental and reproductive toxicity studies in rats;

- There is some evidence for increased susceptibility following pre- and or post-natal 

exposures based on effects seen in range finding developmental toxicity studies in 

rabbits. However, there is a clear NOAEL for these effects, and they occurred at doses 

10-fold higher than the chosen POD;

- There are no residual uncertainties in the exposure databases;

- The dietary risk assessment is based on parent plus metabolite residues and will not 

underestimate dietary exposure to isopyrazam.

4.4.1 Completeness of the Toxicology Database

The toxicology database for isopyrazam is considered adequate for evaluating and characterizing 

isopyrazam toxicity, assessing children’s susceptibility under FQPA and selecting endpoints for 

dietary exposure. All toxicity studies required as part of new 40 CFR Part 158 data requirements

have been submitted.

4.4.2 Evidence of Neurotoxicity

Acute oral (gavage) and subchronic oral (dietary) neurotoxicity studies in rats were conducted on 

the isopyrazam technical product. No evidence of specific neurotoxicity was seen in these 

studies. The NOAEL for the acute neurotoxicity study is 2000 mg/kg. The only effects of 

isopyrazam treatment in the subchronic oral dietary study were reductions in bodyweight and 

food consumption at the highest dose level. The NOAEL for the subchronic neurotoxicity study 

is 382 mg/kg/day.

Clinical signs seen in two subchronic dog studies (side-to-side head wobble, ataxia, reduced 

stability) are consistent with neurotoxic effects. However, detailed and specific 

neuropathological analyses were not conducted for the dog studies (i.e., functional observational 

battery, motor activity, detailed histopathology with special stains). Consequently, there is 

significant uncertainty regarding whether the effects seen in the dog studies are in fact signs of 

neurotoxicity. Clear NOAELs/LOAELs were established for both subchronic dog studies. The 

POD selected for the acute dietary assessment is based on clinical signs seen on day two in one

of four males in the subchronic dog study. This study provides the lowest NOAEL in the 

database (most sensitive endpoint) for a single dose effect. The dose used for the chronic dietary 

risk assessment is eight times lower than the dose at which clinical effects were seen at four 

weeks in the second subchronic dog study. 

Isopyrazam showed no evidence of neurotoxicity in the available acute and subchronic 

neurotoxicity studies in the rat. It is not structurally similar to known neurotoxicants or 

neurotoxic classes of chemicals. Its pesticidal mode of action does not demonstrate potential for 

neurotoxicity. A conservative and protective acute dietary endpoint was selected based on 

sporadic and transient clinical effects seen in the subchronic dog study. There is significant 

uncertainty regarding whether there is a neurotoxicological basis for the effect seen in the 
Page 18 of 67

subchronic dog studies. Therefore, it is unlikely isopyrazam will exhibit neurotoxic effects in a 

developmental neurotoxicity (DNT) study, which is conducted in rats. Based on these 

considerations, a DNT study is not required.

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

There is some evidence for increased susceptibility following pre-and or post-natal exposures 

based on effects seen in range finding developmental toxicity studies in rabbits. Developmental 

effects (eye abnormalities) were observed in two preliminary developmental studies in 

Himalayan rabbits in the absence of maternal toxicity. These effects occurred at relatively high 

doses (200-400 mg/kg/day). In range finding and definitive developmental toxicity studies in 

rats, neither quantitative nor qualitative evidence of increased susceptibility of fetuses to in utero

exposure to isopyrazam was observed. There was no evidence of increased susceptibility in a 

two-generation reproduction study following pre- or post-natal exposure to isopyrazam. There is 

no evidence of neuropathology or abnormalities in the development of the fetal nervous system 

from the available toxicity studies conducted with isopyrazam. Clear NOAELs/LOAELs were 

established for the developmental effects seen in rats and rabbits as well as for the offspring 

effects seen in the two-generation reproduction study and a dose-response relationship for the 

effects of concern is well characterized. The dose used for the acute dietary risk assessment (30 

mg/kg/day), based on effects seen in the subchronic dog study, is protective of the developmental 

and offspring effects seen in rabbits at 200-400 mg/kg/day. Based on these considerations, there 

are no residual uncertainties for pre-and/or post-natal susceptibility.

4.4.4 Residual Uncertainty in the Exposure Database

Since there are no currently registered or proposed occupational or residential uses of 

isopyrazam in the U.S. and adequate residue data are available, there are no residual 

uncertainties in the exposure data base.

4.5 Toxicity Endpoint and Point of Departure Selections

4.5.1 Dose-Response Assessment

Toxicity endpoints and points of departure (PODs) for dietary exposure scenarios are 

summarized below. A detailed description of the studies used as a basis for the selected 

endpoints are presented in Appendix A. PODs for incidental oral, dermal and inhalation 

exposure are not required to assess risk for the existing and proposed uses which are all nondomestic, and have therefore not been selected for this risk assessment. 

An acute POD of 30 mg/kg/day (NOAEL) was selected from a subchronic toxicity study in dogs 

based on clinical signs of toxicity (side-to-side head wobble) observed beginning on day 2 and 

continuing throughout the study in 1 of four male dogs at the LOAEL of 100 mg/kg/day. 

Transient clinical signs (side-to-side head wobble, ataxia, reduced stability) were also observed 

at 300 mg/kg/day in 3 of four male dogs on days 2 and 3 only. An uncertainty factor of 100x 
Page 19 of 67

(10x to account for interspecies extrapolation and 10x for intraspecies variation) was applied to 

the NOAEL to obtain an aRfD of 0.30 mg/kg/day. This endpoint is considered to occur 

following a single dose and is applicable to the population of concern (general population, 

including infants and children). It is considered to be a very conservative endpoint since it is 

based on observations in 1/4 dogs and acute clinical signs were not seen in a second 90-day 

study in dogs or in the chronic dog study. This effect is also protective of the effects seen at the 

limit dose (2000 mg/kg/day) in the acute neurotoxicity study in rats (decreased rearing and 

locomotor activity) and the developmental effect (bilateral microphthalmia) in the developmental 

rabbit studies (at doses ≥400 mg/kg/day). Therefore, a separate acute dietary endpoint for 

females of reproductive age is not necessary. Since HED has reduced the FQPA SF to 1X, the 

acute Population Adjusted Dose (aPAD) is equivalent to the aRfD. 

A chronic POD of 5.5 mg/kg/day (NOAEL) was selected from a chronic toxicity/carcinogenicity 

feeding study in rats based on decreased body weight and body weight gain in females; increased 

incidences of hepatocellular hypertrophy, pigment in centrilobular hepatocytes, eosinophilic foci 

of altered hepatocytes, vacuolation of centrilobular hepatocytes, bile duct hyperplasia, and bile 

duct fibrosis in both sexes; and brown pigment in the kidney in females at 27.6 mg/kg/day 

(LOAEL). An uncertainty factor of 100x (10x to account for interspecies extrapolation and 10x 

for intraspecies variation) was applied to the dose to obtain the chronic reference dose (cRfD) of 

0.055 mg/kg/day. Since the FQPA factor has been reduced to 1X, the chronic population 

adjusted dose (cPAD) is equivalent to the cRfD.

4.5.2 Recommendation for Combining Routes of Exposures for Risk Assessment

Under FQPA, when there are potential residential exposures to a pesticide, HED must aggregate 

exposures from three major sources: oral, dermal and inhalation exposures. These combined 

residential exposures must then be aggregated with exposure from food and water to determine 

aggregate risk. For isopyrazam, an aggregate risk assessment incorporating drinking water and 

residential exposures is not required since there are no existing or proposed domestic uses. 

4.5.3 Cancer Classification and Risk Assessment Recommendation

The Cancer Assessment Review Committee (CARC) classified isopyrazam as “Likely to be 

Carcinogenic to Humans” based on increased liver and uterine endometrial epithelial tumors in 

female rats and increased thyroid follicular cell tumors in male rats. In the absence of mode of 

action data, the CARC recommended linear low dose extrapolation for cancer risk assessment. A 

cancer slope factor (Q1*) of 0.00629 (mg/kg/day)-1 was used for the quantification of human 

cancer risk. 
Page 20 of 67

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

Risk Assessment

Table 4.5.4.1 Summary of Toxicological Doses and Endpoints for Isopyrazam for Dietary Human Health Risk 

Assessments

Exposure/ 

Scenario

Point of 

Departure

(mg/kg/day)

Uncertainty/

FQPA Safety 

Factors

RfD, PAD, Level of 

Concern for Risk 

Assessment

(mg/kg/day)

Study and Toxicological Effects

Acute Dietary 

(All Populations)

NOAEL= 30 UFA= 10x

UFH=10x

FQPA SF= 1x

Acute RfD = 0.30

aPAD = 0.30

Subchronic Toxicity – Dog

LOAEL = 100 mg/kg/day based on

clinical signs (side-to-side head 

wobble) in male dogs.

Chronic Dietary 

(All Populations) NOAEL= 5.5

UFA= 10x

UFH=10x

FQPA SF= 1x

Chronic RfD = 0.055

cPAD = 0.055

Chronic Toxicity/Carcinogenicity -

Rats

LOAEL = 27.6 mg/kg/day based on 

decreased body weight and body 

weight gain in females; increased 

incidences of hepatocellular 

hypertrophy, pigment in centrilobular 

hepatocytes, eosinophilic foci of 

altered hepatocytes, vacuolation of 

centrilobular hepatocytes, bile duct 

hyperplasia, and bile duct fibrosis in 

both sexes; and brown pigment in the 

kidney in females.

Cancer (all routes)

Classification: CARC classified isopyrazam as “Likely to be Carcinogenic to Humans” based 

on increased liver and uterine endometrial epithelial tumors in female rats and increased thyroid 

follicular cell tumors in male rats. A cancer slope factor (Q1*) of 0.00629(mg/kg/day)-1 was 

calculated based on an increase in increase in liver tumors in female rats.

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

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

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

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

sensitivity among members of the human population (intraspecies). FQPA SF = FQPA Safety Factor. PAD = 

population adjusted dose (a = acute, c = chronic). RfD = reference dose. .

5.0 Dietary Exposure and Risk Assessment

5.1 Metabolite/Degradate Residue Profile

5.1.1 Summary of Plant and Animal Metabolism Studies

The nature of the residue in banana, apple, and peanut is deemed adequately understood based on 

previously submitted wheat, grape, and lettuce metabolism studies. Residues of isopyrazam 

consist mainly of unchanged parent with several minor metabolites resulting from the 

monohydroxylation of either the bicyclic ring or the isopropyl group on the bicyclic ring. There 

was little cleavage of the amide bond or demethylation of the pyrazole ring. Interconversion of 

the diasterioisomers (diastereoisomerization) was not apparent. Metabolites were all <6% of the 
Page 21 of 67

total radioactive residue (TRR) in all three studies with the exception of the lettuce study in 

which the metabolite formed via the hydroxylation at the central carbon of the isopropyl group 

on the bicyclic ring was found at greater than 10% of the TRR. This tertiary alcohol metabolite 

(CSCD460260) is also comprised of a mixture of two diasterioisomers designated syn-

(CSCD459488) and anti-(CSCD459489) isomers. The syn-(CSCD459488) isomer of the tertiary 

alcohol metabolite was the major metabolite accounting for 17% of the TRR in lettuce (1% free 

and 16% conjugated at 14-day PHI), while the anti-(CSCD459489) isomer of the tertiary alcohol 

metabolite was a minor metabolite accounting for <1% of the TRR in lettuce. A proposed 

metabolic pathway for isopyrazam in plants submitted by the registrant is provided in Appendix 

B.

The nature of the residue in ruminant and poultry is deemed adequately understood based on the 

new goat and hen metabolism data conducted with the parent. Isopyrazam is extensively 

metabolized to a number of metabolites by hydroxylation (mono-, di-, or tri-) of the bicyclic ring 

and/or the isopropyl group on the bicyclic ring. There was little cleavage of the amide bond or 

demethylation of the pyrazole ring. Isopyrazam and its dihydroxy metabolite, CSCD656800, were 

the two major components found in livestock commodities. Parent was the major residue found in 

fat, but was present at lower levels in milk, egg, and other tissues. All other metabolites were 

<10% of the TRR with the exception of a monohydroxy metabolite, CSCD563692, which was 

present in goat liver (≤21% of the TRR) and a dihydroxy metabolite, hydroxy CSCD459489, 

which was present in egg (≤17% of the TRR). A proposed metabolic pathway for isopyrazam in 

livestock submitted by the registrant is provided in Appendix B.

5.1.2 Summary of Environmental Degradation

There is no drinking water, occupational or residential exposure associated with the existing and 

proposed uses which are all non-domestic. Therefore, these exposure pathways were not 

assessed. 

5.1.3 Comparison of Metabolic Pathways

The proposed metabolic pathway for isopyrazam in plants and livestock is provided in Appendix 

B. Similar metabolic pathways are seen in plants, livestock and rats based on available studies. 

Metabolism studies in the rat indicate that isopyrazam is converted to a number of metabolites 

resulting from the hydroxylation of the bicyclic ring, similar to the metabolic scheme observed in 

the plant and livestock studies.

5.1.4 Residues of Concern Summary and Rationale

The residues of concern in/on banana were determined by the HED Residues of Concern 

Knowledgebase Subcommittee (ROCKS Revised Report, 6/16/11, DP#390870) to be isopyrazam 

(sum of syn-(SYN534969) and anti-(SYN534968) isomers) for tolerance enforcement and 

isopyrazam (sum of syn-(SYN534969) and anti-(SYN534968) isomers) and its metabolite 

CSCD459488 (free and conjugated), the syn-isomer of the tertiary alcohol metabolite, for risk 
Page 22 of 67

assessment. While both the syn-(CSCD459488) and anti-(CSCD459489) isomers of the tertiary 

alcohol metabolite (CSCD460260) are judged to have similar toxicity when compared to the 

parent, the committee decided to include only the syn-isomer of the tertiary alcohol metabolite 

(CSCD459488; free and conjugated) in the risk assessment for banana based the banana field trial 

data which found detectable residues of CSCD459488 (free and conjugated) in/on whole banana 

but not CSCD459489 (free and conjugated). However, the Committee also recommended that 

residues of CSCD459489 (free and conjugated) should be analyzed for in future residue chemistry 

studies. 

No new plant metabolism data were submitted with the current petition and the HED isopyrazam 

risk assessment team has decided that it is appropriate to expand the HED ROCKS decision for 

banana to apple and peanut. The team has also decided to explicitly include CSCD459489 (free 

and conjugated) as a residue of concern for risk assessment so that there is no ambiguity as to what 

residues should be analyzed for in future residue chemistry studies.

The nature of the residue in ruminant and poultry is deemed adequately understood based on the 

new goat and hen metabolism data conducted with the parent and submitted in support of the 

current petition. Isopyrazam is extensively metabolized to a number of metabolites by 

hydroxylation (mono-, di-, or tri-) of the bicyclic ring and/or the isopropyl group on the bicyclic 

ring. There was little cleavage of the amide bond or demethylation of the pyrazole ring. 

Isopyrazam and its dihydroxy metabolite, CSCD656800, were the two major components found in 

livestock commodities. Parent was the major residue found in fat, but was present at lower levels 

in milk, egg, and other tissues. All other metabolites were <10% of the TRR with the exception of 

a monohydroxy metabolite, CSCD563692, which was present in goat liver (≤21% of the TRR) and 

a dihydroxy metabolite, hydroxy CSCD459489, which was present in egg (≤17% of the TRR).

There are livestock feedstuffs associated with the proposed uses of isopyrazam on peanut and 

apple: peanut meal, peanut hay (considered to be under grower control in the U.S.) and apple, 

wet pomace. There is no potentially significant exposure by livestock to isopyrazam residues in 

peanut meal. Peanut hay is considered to be under grower control in the U.S. and no peanut hay 

data were submitted. Only wet apple pomace, which is considered an alternative dairy cattle 

feedstuff in the U.S., is a potential source of significant exposure to residues of isopyrazam by 

dairy cattle. There is no other potentially significant exposure from treated feedstuffs for dairy 

cattle or other livestock assuming that treated peanut hay is not fed to livestock. The maximum 

reasonably balanced dietary burden for residues of isopyrazam by dairy cattle is 0.11 ppm.

The submitted cattle feeding study is not adequately supported by storage stability data but may 

be considered supplemental to the goat metabolism study findings for determining the needed for 

tolerances in milk and meat. In brief, cows each received twenty eight daily doses of isopyrazam 

(70:30 ratio syn:anti isomers), at rates of 15, 42, and 137 ppm in feed. Respectively, these 

feeding levels equate to 136x, 382x, and 1245x of the reasonably balance dietary burden for 

dairy cattle (0.11 ppm). Residues of parent (isopyrazam) and total isopyrazam 

(isopyrazam/metabolites which are convertible to the common moiety CSAA798670, expressed 

as isopyrazam) were measured in samples of whole milk, skim milk, cream, muscle, fat, liver, 
Page 23 of 67

and kidney. Based on the maximum residues of total isopyrazam (isopyrazam/metabolites which 

are convertible to the common moiety CSAA798670, expressed as isopyrazam) found in meat 

and milk and the maximum reasonably balanced dietary burden for cattle, which assumes that 

treated peanut hay is not fed, finite residues of isopyrazam are not expected in meat and milk 

from the proposed uses. Samples were stored frozen for up to 13 months prior to analysis. 

Although supporting storage stability data were not submitted for either residues of parent or 

total isopyrazam (isopyrazam/metabolites which are convertible to the common moiety 

CSAA798670, expressed as isopyrazam), given that samples were stored frozen for about a year 

and that total isopyrazam is measured using a common moiety method there is less concern for 

loss of sample integrity in this study due to storage conditions/duration for total isopyrazam than 

for parent. Supporting storage stability data are not required at this time for reasons 

discussed below but will be critical in the future if/when additional livestock feedstuffs 

necessitate setting tolerances for residues of isopyrazam in milk and/or meat and 

estimating isopyrazam residues of concern in milk and/or meat commodities in dietary 

assessments. 

When taken together, and assuming that isopyrazam treated peanut hay is not fed to livestock in 

Nicaragua, the following findings, are adequate to demonstrate that there is no reasonable 

expectation of finite residues of isopyrazam in livestock commodities from the proposed uses 

and that tolerances in livestock commodities are not needed: (1) there is no potentially 

significant exposure for isopyrazam residues to beef cattle, poultry, or swine from the proposed 

uses; (2) only wet apple pomace, which is considered an alternative feedstuff in the U.S., is a 

potential source of significant exposure to residues of isopyrazam by dairy cattle; (3) the

calculated maximum reasonably balanced dietary burden for isopyrazam by dairy cattle is low 

(0.11 ppm); (4) based on the maximum TRR (expressed as isopyrazam equivalents) found in 

milk (0.08 ppm) and tissues (0.60 ppm for liver; all others <0.2 ppm) collected from goats dosed 

with isopyrazam for 7 days at highly exaggerated rates of 29-45 ppm in feed and given that 

isopyrazam is expected to metabolize extensively in the ruminant, there is no reasonable 

expectation of finite residues of isopyrazam in milk and meat; and (5) there is evidence 

(considered supplemental due to lack of storage stability data) provided in the cattle feeding 

study that there is no reasonable expectation of finite residues of isopyrazam in milk and meat 

based on the maximum residues of total isopyrazam (isopyrazam/metabolites which are

convertible to the common moiety CSAA798670, expressed as isopyrazam) found in meat (0.24 

ppm) and milk (0.05) collected from cows dosed for 28 days at a highly exaggerated rate of 15 

ppm in feed.

Based on the data submitted, the HED isopyrazam risk assessment team has decided that the 

residue of concern in livestock commodities is isopyrazam (sum of syn-(SYN534969) and anti-

(SYN534968) isomers) for tolerance enforcement and isopyrazam (sum of syn-(SYN534969) 

and anti-(SYN534968) isomers) plus its metabolites convertible the CSAA798670 moiety [3-

(difluromethyl)-1-methyl-pyrazole-4- methanoic acid], expressed as isopyrazam, for risk 

assessment. This determination is predicated on the understanding that if/when additional 

livestock feedstuffs necessitate setting tolerances for residues of isopyrazam in milk and/or 

meat, a suitable enforcement method is available with LOQs of 0.0025 ppm or less for each 
Page 24 of 67

isomer. HED notes that GRM006.09A (Version 2) with LOQs of 0.0025 ppm for both 

isomers was adequately validated as a data collection method in milk and meat.

Assuming that isopyrazam treated peanut hay is not fed to cattle in Nicaragua, HED finds that 

for existing and proposed uses of isopyrazam, tolerances in livestock commodities are not 

needed. 

Table 5.1.4. Compounds to be Included in the Risk Assessment and Tolerance Expression.

Matrix

Residues included in Dietary Risk 

Assessment

Residues included in Tolerance 

Expression for Compliance Monitoring

Plants Apple, Banana, 

Peanut

Isopyrazam + CSCD459488 (free 

and conjugated) + CSCD459489 

(free and conjugated)

Isopyrazam 

Rotational Crop Not applicable since there are no U.S. registrations

Livestock Ruminant Isopyrazam + its metabolites 

convertible to the CSAA798670 

moiety, expressed as isopyrazam

Isopyrazam

Poultry

Drinking Water Not applicable since there are no U.S. registrations

Isopyrazam (SYN520453; sum of syn-(SYN534969) and anti-(SYN534968) isomers) = 3-(difluoromethyl)-1-

methyl-N-[1,2,3,4-tetrahydro-9-(1- methylethyl)-1,4-methanonaphthalen-5-yl]-1H-pyrazole-4-carboxamide. 

(CAS)

CSCD459488 (syn-isomer of the tertiary alcohol metabolite) = 3-(difluoromethyl)-1-methyl-N-[(1RS, 4SR, 9RS)-

1,2,3,4-tetrahydro-9-(2-hydroxypropan-2-yl)-1,4-methanonaphthalen-5-yl]pyrazole-4-carboxamide(mix of two 

enantiomers). (IUPAC)

CSCD459489 (anti-isomer of the tertiary alcohol metabolite) = 3-(difluoromethyl)-1-methyl-N-[(1RS, 4SR, 9SR)-

1,2,3,4-tetrahydro-9-(2-hydroxypropan-2-yl)-1,4-methanonaphthalen-5-yl]pyrazole-4-carboxamide(mix of two 

enantiomers). (IUPAC)

CSAA798670 = 3-(difluromethyl)-1-methyl-pyrazole-4- methanoic acid

5.2 Food Residue Profile

Apple and peanut (nutmeat only) field trials have been submitted that are adequate in number. 

Trials were conducted outside the NAFTA growing regions, in Chile and Nicaragua, 

respectively. An acceptable apple processing study was submitted. A peanut processing study 

was not submitted but is not required; HED is persuaded that the proposed/recommended 

tolerance in/on peanut will cover isopyrazam residues in peanut oil processed from isopyrazam 

treated peanuts. These data were generated with an acceptable data collection method and are 

supported by adequate storage stability data.

For apples, the residue data reflect the use of 3 foliar spray applications of a suspension

concentrate (SC) formulation of isopyrazam (70:30 ratio syn:anti isomers) at a target rate of 150 
Page 25 of 67

g ai/ha/application (1.25x and 1x the maximum proposed single application rates for the SC and 

EC formulations, respectively) for a total application rate of 450 g ai/ha (1.9x and 1.5x the 

maximum proposed seasonal application rates for the SC and EC formulations, respectively), 

using a minimum retreatment interval (RTI) of 7 days; preharvest interval (PHI) of 14 to 21 

days. The data do not reflect the use of an adjuvant in the spray mix. The maximum residue of 

isopyrazam (sum of syn-(SYN534969) and anti-(SYN534968) isomers) was 0.336 ppm (0.277 

ppm HAFT) in/on whole fruit, with a 14 day PHI, and 0.249 ppm (0.234 ppm HAFT) in/on 

whole fruit, with a 21 day PHI. Residues of the isopyrazam metabolites, CSCD459488 (free and 

conjugated; syn-isomer of the tertiary alcohol metabolite), and CSCD459489 (free and 

conjugated; anti-isomer of the tertiary alcohol metabolite) were <LOQ (0.005 ppm for each 

isomer) in all trials. In the residue decline trials, an overall decline of isopyrazam residues (sum 

of syn-(SYN534969) and anti-(SYN534968) isomers) was observed in/on apples between the 0-

day and 21- to 28-day PHIs. However, slight increases in residues were observed between the 0-

day and 14-day PHI in three of the four trials. Residue decline could not be assessed for 

metabolites CSCD459488 and CSCD459489 in apple because residues were below the LOQ at 

each sampling interval.

Table 5.2. Summary of Residue Data from Apple Crop Field Trials with SC Formulation of Isopyrazam

(Syn:Anti Ratio 70:30).

Commodity Analyte Total App. 

Rate

lb ai/A

(g ai/ha)

PHI

(days)

Residue Levels (ppm)1

n Sample 

Min.

Sample 

Max.

LAFT2 HAFT2 Median Mean Std. 

Dev.

Apple, 

Fruit

Isopyrazam30.399-0.411

(448.3-462.0)

13-14 9 0.148 0.336 0.153 0.277 0.221 0.222 0.042

20-21 0.110 0.249 0.124 0.234 0.196 0.187 0.032

CSCD459488 13-14 9 ND <0.005 ND <0.005 0.005 0.005 N/A

20-21 ND <0.005 ND <0.005 0.005 0.005 N/A

CSCD459489 13-14 9 Not Detectable (ND)

20-21

1

 Except for sample min/max, values reflect per trial averages; n = no. of field trials. For calculation of median, 

mean, and standard deviation, the LOQ (0.005 ppm) was used for any results reported as <LOQ. 

N/A = Not applicable.

2

 LAFT = lowest average field trial; HAFT = highest average field trial.

3 Isopyrazam = Sum of syn-(SYN534969) and anti-(SYN534968) isomers.

Using the Organization for Economic Development Maximum Residue Limit (MRL)/Tolerance 

calculation procedure, the available crop field trial data indicate a tolerance of 0.60 ppm for 

residues of isopyrazam in/on apple is appropriate. [Note: This calculation assumes a 21-day 

PHI.] For the purposes of harmonization with a pending EU MRL for residues of isopyrazam 

in/on pome fruit (0.7 mg/kg), HED is recommending a tolerance of 0.70 ppm in/on apple.

The recommended apple tolerance, which is based on apple field trial data conducted with an SC 

formulation of isopyrazam and reflecting a 21-day PHI, will be adequate to cover residues of 

isopyrazam in/on apple resulting from the use of an EC formulation at the same use rate and for 

the proposed 63-day PHI for the EC formulation. 
Page 26 of 67

The submitted apple processing data are adequate and tolerances are not needed for residues of 

isopyrazam in processed commodities of apple. Residues of isopyrazam (sum of syn-

(SYN534969) and anti-(SYN534968) isomers) did not concentrate in apple juice but did 

concentrate in wet apple pomace. Based on the highest average field trial (HAFT) for residues 

of isopyrazam in/on apple (0.234 ppm) and the concentration factor for isopyrazam in wet apple 

pomace (2x), the recommended tolerance for residues of isopyrazam in/on apple will cover 

residues that may result in apple, wet pomace. 

For peanuts (nutmeats only), the residue data reflect the use of 3 foliar spray applications of an 

EC formulation of isopyrazam (70:30 ratio syn:anti isomers) at a target rate of 125 g 

ai/ha/application (1x the maximum proposed single application rate) for a total application rate 

of 375 g ai/ha (1x the maximum proposed seasonal application rate), using a 12-14 day RTI. 

Samples were harvest at a 7-day PHI and allowed to dry in the field 3-6 days prior to collection. 

Residues of isopyrazam (sum of syn-(SYN534969) and anti-(SYN534968) isomers) and 

metabolites CSCD459488 and CSCD459489 in/on peanut nutmeat were all <LOQ (0.005 ppm 

for each isomer). No peanut hay data were submitted.

No peanut processing data were submitted. However, residues in peanuts are expected to be 

very low compared to the validated LOQs of the enforcement method. ChemSAC (meeting 

2/6/13) was persuaded that the recommended tolerance for residues of isopyrazam in/on peanut 

will cover residues that may result in peanut meal and oil.

The submitted cattle feeding study is not adequately supported by storage stability data but may 

be considered supplemental to the goat metabolism study findings. These data were discussed 

above as part of the rationale for the residues of concern in livestock (see section 5.1.4). Based 

primarily on the available goat metabolism data and assuming that isopyrazam treated peanut 

hay is not fed to livestock in Nicaragua, there is no reasonable expectation of finite residues of 

isopyrazam in livestock commodities from the proposed uses and tolerances in livestock 

commodities are not needed. 

5.3 Water Residue Profile

An assessment of residues in drinking water is not required because there is no drinking water 

exposure associated with existing and proposed uses which are all non-domestic.

5.4 Dietary Risk Assessment

HED conducted screening-level acute, chronic and cancer dietary risk assessments using the 

Dietary Exposure Evaluation Model DEEM-FCID, Version 3.16 which uses food consumption 

data from the U.S. Department of Agriculture’s National Health and Nutrition Examination 

Survey, What We Eat in America, (NHANES/WWEIA). All established, pending and proposed 

uses of isopyrazam were included. Dietary risk assessment incorporates both exposure and 

toxicity of a given pesticide. For acute and chronic dietary assessments, the risk is expressed as 
Page 27 of 67

a percentage of a maximum acceptable dose (i.e., the dose which HED has concluded will result 

in no unreasonable adverse health effects). This dose is referred to as the population adjusted 

dose (PAD). The PAD is equivalent to the reference dose (RfD) divided by the combined 

uncertainty factors retained due to missing data or concerns for susceptibility. For acute and 

non-cancer chronic exposures, HED is concerned when estimated dietary risk exceeds 100% of 

the PAD. 

5.4.1 Description of Residue Data Used in Dietary Assessment

For the acute, chronic and cancer dietary analyses, maximum residues from field trials conducted 

at the maximum use rates were used to estimate residues of isopyrazam (sum of syn-

(SYN534969) and anti- (SYN534968) isomers) and the syn-(CSCD459488; free and conjugated) 

and anti-(CSCD459489; free and conjugated) isomers of the tertiary alcohol metabolite 

(CSCD460260). DEEM default processing factors were used for all processed commodities 

including dried apple (8.0), apple juice/cider (1.3), dried banana/plantain (3.9), and peanut butter 

(1.89). In the absence of peanut processing data, the maximum theoretical concentration factor 

was used for peanut oil (2.8).

5.4.2 Percent Crop Treated Used in Dietary Assessment

The dietary assessment assumes 100% of all apple, banana, and peanut commodities consumed 

in the U.S. have been treated with isopyrazam.

5.4.3 Acute Dietary Exposure and Risk

A screening level acute dietary (food only) exposure analysis was performed for the general U.S. 

population and various population subgroups. Acute dietary risk estimates are not of concern for 

the general U.S. population or other population subgroups. At the 95th percentile, the acute 

exposure results in an estimated dietary (food) risk equivalent to ≤4.2% of the acute population 

adjusted dose (aPAD) for all populations. The most highly exposed subpopulation is children 1-

2 years old. (Table 5.4.6).

5.4.4 Chronic Dietary Risk Assessment

A screening level chronic dietary (food only) exposure analysis was performed for the general 

U.S. population and various population subgroups. Chronic dietary risk estimates are not of 

concern for the general U.S. population or other population subgroups. The estimated noncancer chronic dietary (food) risk is equivalent to ≤6.1% of the chronic population adjusted dose 

(cPAD) for all populations. The most highly exposed subpopulation is children 1-2 years old. 

(Table 5.4.6). 

5.4.5 Cancer Dietary Risk Assessment

A screening-level cancer dietary (food only) exposure analysis was performed for the general 
Page 28 of 67

U.S. population. The resulting estimated cancer dietary (food) risk is 2 x 10-6for the general 

U.S. population. (Table 5.4.6). 

5.4.6 Summary Table

Table 5.4.6. Summary of Dietary (Food Only) Exposure and Risk for Isopyrazam

Population Subgroup

Acute Dietary

95th Percentile Chronic Dietary Cancer

Dietary 

Exposure 

(mg/kg/day)

%aPAD

Dietary 

Exposure

(mg/kg/day)

% cPAD

Dietary 

Exposure

(mg/kg/day)

Risk

General U.S. Population 0.001943 < 1 0.000379 < 1 0.000379 2 x10-6

All Infants (< 1 year old) 0.008291 2.8 0.001873 3.4

NA NA

Children 1-2 years old 0.012554 4.2 0.003379 6.1

Children 3-5 years old 0.007506 2.5 0.001802 3.3

Children 6-12 years old 0.003241 1.1 0.000652 1.2

Youth 13-19 years old 0.001262 < 1 0.000222 < 1

Adults 20-49 years old 0.000776 < 1 0.000139 < 1

Adults 50-99 years old 0.000712 < 1 0.000130 < 1

Females 13-49 years old 0.000905 < 1 0.000156 < 1

6.0 Residential (Non-Occupational) Exposure/Risk Characterization

There are no residential uses of isopyrazam registered in the U.S.

7.0 Aggregate Exposure/Risk Characterization

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

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

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

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

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

duration of exposure. Since existing and proposed uses of isopyrazam are all non-domestic, 

there is no domestic potential for drinking water and/or residential exposures. Therefore, an 

aggregate assessment is not relevant for the existing and proposed uses of isopyrazam.

8.0 Cumulative Exposure/Risk Characterization

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

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

to isopyrazam and any other substances and isopyrazam does not appear to produce a toxic 

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

EPA has not assumed that isopyrazam has a common mechanism of toxicity with other 

substances. For information regarding EPA’s efforts to determine which chemicals have a 

common mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the 
Page 29 of 67

policy statements released by EPA’s Office of Pesticide Programs concerning common 

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

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

9.0 Occupational Exposure/Risk Characterization

Since existing and proposed uses of isopyrazam are all non-domestic, there is no domestic 

potential for occupational exposures. An occupational exposure assessment is not relevant.

10.0 References

External References

United Kingdom, 2010. Draft Assessment Report (DAR) on the active substance isopyrazam. 

April 2010. Volume 3, Annex B.7.

Note: RD has verified that the subject DAR, prepared by the United Kingdom (2010) for 

the European Food Safety Authority (EFSA), may be considered publicly available and 

that HED may use it at will (email from C. Giles-Parker (RD) to B. Cropp-Kohlligian 

(HED) dated 4/26/13). In lieu of internal review, HED has relied on the scientific 

acceptability review in the subject DAR for a number of residue chemistry studies 

submitted to the Agency in support the previous and current petitions.

EFSA (European Food Safety Authority), 2013. Reasoned opinion on the modification of the 

existingMRLs for isopyrazam in pome fruits, various stone fruits and oilseeds. EFSA 

Journal 2013;11(4):3165.

Internal References

Author: Marquea King

Date: 4/20/10

TXR No.: 0054875

Title: Isopyrazam. [Toxicology and Metabolism: Evaluation of Submitted Data.]

Author: Marquea King

Date: 5/18/10

TXR No.: 0055861

Title: Isopyrazam. [Immuno Tox Study: Evaluation of Submitted Data.]

Author: Jessica Kidwell

Date: 1/8/11

TXR No.: 0055619

Title: Isopyrazam: Report of the Cancer Assessment Review Committee.
Page 30 of 67

Author: Lori Brunsman

Date: 5/4/11

TXR No.: 0055862

Title: Revised Isopyrazam Quantitative Risk Assessment Based on Wister Rat Dietary 

Study.

Author: Edward Scollon

Date: 6/16/11

DP No.: D390870

Title: Isopyrazam. Report of the Residues of Concern Knowledgebase Subcommittee

(ROCKS) - Revised.

Author: Gary Otakie

Date: 6/16/11

DP No.: D390869

Title: Isopyrazam. Request to Establish a Tolerance for Isopyrazam (SYN520453) 

Fungicide in/on Imported Banana. Updated Summary of Residue Data.

Author: Bonnie Cropp-Kohlligian

Date: 7/17/13

DP Nos.: D403208, D408357, D410599 and D413179

Title: Isopyrazam. Tolerances with No U.S. Registrations in/on Imported Apple and 

Peanut. Summary of Analytical Methods and Residue Data.

Author: Bonnie Cropp-Kohlligian

Date: 7/17/13

DP No.: D409592

Title: Isopyrazam. Acute, Chronic and Cancer Dietary (Food Only) Exposure and Risk 

Assessments for the Proposed Tolerances with No U.S. Registrations for Imported 

Apple and Peanut.
Page 31 of 67

Appendix A. Toxicology Profile and Executive Summaries

A.1 Toxicology Data Requirements

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

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

Guideline 

No. Study Type Technical MRID 

Required Submitted No.

870.3100

870.3150

870.3200

870.3250

870.3465

Subchronic (Oral) Toxicity - Rodent....................................................

Subchronic (Oral) Toxicity - Non-Rodent ...........................................

21/28-Day Dermal Toxicity .................................................................

90-Day Dermal Toxicity ......................................................................

90-Day Inhalation Toxicity ..................................................................

Y

Y

N

N

N

Y

Y

N

N

N

47746832

47746833

47746834

47746835

47746836

---

---

---

870.3700a

870.3700b

870.3800

Prenatal Developmental Toxicity - Rodent ..........................................

Prenatal Developmental Toxicity - Non-Rodent..................................

Reproduction and Fertility Effects.......................................................

Y

Y

Y

Y

Y

Y

47746843

47746845

47746840

47746847

870.4100a

870.4100b

870.4200a

870.4200b

870.4300

Chronic (Oral) Toxicity - Rodent.........................................................

Chronic (Oral) Toxicity - Non-Rodent (Dog) ......................................

Carcinogenicity - Rat

Carcinogenicity - Mouse ......................................................................

Combined Chronic Toxicity /Carcinogenicity .....................................

N

Y

N

Y

Y

N

Y

N

Y

Y

---

47746848

---

47746849

47746851

870.6100a

870.6100b

870.6200a

870.6200b

870.6300

870.7800

Neurotoxicity - Acute Delayed Neurotox.- Hen...................................

Neurotoxicity - Subchronic - Hen .......................................................

Neurotoxicity Screening Battery - Acute - Rat ....................................

Neurotoxicity Screening Battery -Subchronic - Rat .................................

Developmental Neurotoxicity..................

Immunotoxicity............................. ..............................................

N

N

Y

Y

N

Y

N

N

Y

Y

N

Y

---

---

47746866

47746865

---

48347201
Page 32 of 67

A.2 Toxicity Profiles

Table A.2.1 Acute Toxicity Profile – Isopyrazam

Guideline No. Study Type MRID(s) Results

Toxicity 

Category

870.1100 Acute oral, rat

47746821

47746822

47746823

47746824

47746825

LD50 > 2000 mg/kg in female rat

LD50 > 2000 mg/kg in female rat

LD50 > 2000 mg/kg in female rat (syn)

a

LD50 > 2000 mg/kg in female rat

LD50 > 2000 mg/kg in female rat

III

870.1200 Acute dermal, rat No study provided for review.b

870.1300 Acute inhalation, rat No study provided for review.b

870.2400 Acute eye irritation, rabbit No study provided for review.b

870.2500 Acute dermal irritation, 

rabbit No study provided for review.b

870.2600

Skin sensitization, guinea 

pig No study provided for review.b

a LD50 = 310 mg/kg (for both anti-conformation and anti/syn, 1/1, conformation mixture)

b Based on the UK Evaluation Report “Setting of MRLs for Isopyrazam in Banana,” isopyrazam is of low acute oral, dermal and 

inhalation toxicity, is not irritating to the skin and eye. It is a skin sensitizer. Data are cited from literature studies.

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

Guideline 

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

870.3100 

Subchronic 

(Oral) Toxicity 

(Rat)

47746832 (2008)

Acceptable/guideline

0, 500, 2500, or 7000 ppm

M: 0, 76.5, 390.8, or 1382.8 mg/kg/day

F: 0, 87.2, 448.9, or 1759.6 mg/kg/day

NOAEL was not observed

LOAEL = 76.5/87.2 mg/kg/day (M/F), based on 

decreased food utilization in males.

Subchronic 

(Oral) Toxicity -

(Rat)

47746833 (2008)

Acceptable/guideline

0, 100, 250, or 2000 ppm

SYN520453 (89.5% Syn:6.9% Anti)

M: 0, 8.30, 20.29, or 158.67 mg/kg/day

F: 0, 8.24, 20.75, or 163.26 mg/kg/day

SYN520453 (63.3% Syn:27.5% Anti)

M: 0, 9.87, 24.14, or 192.92 mg/kg/day

F: 0, 9.49, 24.15, or 197.02 mg/kg/day

NOAEL = 20.29/20.75 mg/kg/day (M/F; 89.5% 

Syn:6.9% Anti) and 24.14/24.15 mg/kg/day 

(M/F; 63.3% Syn:27.5% Anti)

LOAEL = 158.67/163.26 mg/kg/day (M/F; 

89.5% Syn:6.9% Anti) and 192.92/197.02 

mg/kg/day (M/F; 63.3% Syn:27.5% Anti), 

based on the following findings with each test 

material: decreased body weight, body weight 

gain, and food utilization in females; decreased 

plasma alkaline phosphatase in both sexes; and 

increased incidences of centrilobular hepatocyte 

hypertrophy, midzonal vacuolation in liver, and 

increased liver weight in both sexes.

Subchronic 

(Oral) Toxicity -

(Rat)

47746834 (2007)

Acceptable/guideline

0, 300, 1500, or 6000 ppm

M: 0, 21.3, 106.3, or 463.0 mg/kg/day

NOAEL = Not identified

LOAEL = 21.3/23/8 mg/kg/day (M/F), based on 

decreased body weight in females, and 

increased centrilobular hepatocyte hypertrophy 
Page 33 of 67

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

Guideline 

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

F: 0, 23.8, 117.8, or 484.4 mg/kg/day and increased liver weight of 14%

870.3150

Subchronic 

(Oral) Toxicity -

Non-Rodent 

(Dog)

47746835 (2008)

Acceptable/guideline

0, 10, 30, or 250 mg/kg/day

NOAEL = 30 mg/kg/day

LOAEL = 250 mg/kg/day, based on increased 

incidence of salivation, and transient decreases 

in food consumption and body weight in both 

sexes; and increased abnormal behavior and 

decreased activity in males.

47746836 (2007)

Acceptable/guideline

0, 30, 100, or 300 mg/kg/day

NOAEL = 30 mg/kg/day

LOAEL = 100 mg/kg/day, based decreased 

body weight gains, clinical signs of toxicity 

(side-to-side head wobble in one male), 

increased alkaline phosphatase and decreased 

plasma albumin in both sexes; and increased 

adjusted for bw/liver weights in males

870.3700a

Prenatal 

Developmental 

Toxicity (Han 

Wistar Rat)

47746843 (2008)

Acceptable/guideline

0, 20, 75, or 200 mg/kg/day

Maternal NOAEL = 20 mg/kg/day.

LOAEL = 75 mg/kg/day, based on decreased 

food consumption, body weights and BW gains. 

Fetal NOAEL = 20 mg/kg/day.

LOAEL = 75 mg/kg/day, based on decreased 

body weight and non- or incomplete ossification 

47746845 (2008)

Acceptable/guideline

0, 20, 75, or 250 mg/kg/day

Maternal NOAEL = 75 mg/kg/day.

LOAEL = 250 mg/kg/day, based on decreased 

body weight gain and food consumption; and 

increased mortality in dams and early intrauterine death.

Fetal NOAEL = 75 mg/kg/day.

LOAEL = 250 mg/kg/day, based on decreased 

fetal body weight and delayed ossification.

870.3700b 

Prenatal 

Developmental 

Toxicity – NonRodent ( New 

Zealand White 

Rabbit)

47746840 (2008)

Acceptable/guideline

0, 30, 150, or 500 mg/kg/day

Maternal NOAEL = 150 mg/kg/day.

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

mortality, decreased food consumption, 

decreased defecation, increased liver weights, 

and microscopic findings in the liver. 

Fetal NOAEL = 500 mg/kg/day.

LOAEL = was not observed.

870.3800 

Reproduction 

and Fertility 

Effects (Rat)

47746847 (2008)

Acceptable/guideline

0, 100, 500, or 3000 ppm 

M: 0, 8.9, 44.5, or 269.3 mg/kg/day a

F: 0, 9.8, 48.4, or 289.0 mg/kg/day a

Parental NOAEL = 8.9/9.8 (M/F) mg/kg/day.

LOAEL = 44.5/48.4 (M/F) mg/kg/day, based on 

decreased body weight and food consumption in 

females; and increased hepatocellular 

hypertrophy and liver weights in both sexes. 

Reproductive NOAEL = 269.3/289.0 (M/F) 

mg/kg/day.

LOAEL was not observed.

Offspring NOAEL = 44.5/48.4 (M/F) 

mg/kg/day

LOAEL = 269.3/289.0 (M/F) mg/kg/day, based 
Page 34 of 67

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

Guideline 

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

on increased liver weights in both sexes. 

870.4100b 

Chronic (Oral) 

Toxicity - NonRodent (Dog)

47746848 (2008)

Acceptable/guideline

0, 25, 100, or 250 mg/kg/day

NOAEL = 25 mg/kg/day

LOAEL = 100 mg/kg/day, based on decreased 

body weight gains, increased liver weights, 

decreased albumin and bilirubin in males, and 

increased plasma alkaline phosphatase in both 

sexes.

No increased incidence of neoplasia was noted.

870.4200b Carcinogenicity

(Mouse)

47746849 (2008)

Acceptable/guideline

0, 70, 500, or 3500 ppm 

M: 0, 7.8, 56.2, or 432.6 mg/kg/day

F: 0, 9.9, 74.9, or 553.6 mg/kg/day

NOAEL = 56.2/74.9 (M/F) mg/kg/day

LOAEL = 432.6/553.6 (M/F) mg/kg/day, based 

on decreased body weights and food utilization 

in both sexes; and increased liver weight and 

incidence of hepatocellular hypertrophy in both 

sexes.

No increased incidence of neoplasia was noted.

870.4300

Combined 

Chronic 

Toxicity/ 

Carcinogenicity

(Rat)

47746851 (2008)

Acceptable/guideline

0,100, 500, or 3000 ppm

M: 0, 5.5, 27.6, or 173.5 mg/kg/day

F: 0, 6.9, 34.9, or 232.8 mg/kg/day

NOAEL = 5.5/6.9 (M/F) mg/kg/day

LOAEL = 27.6/34.9 (M/F) mg/kg/day, based on 

decreased body weight and body weight gain in 

females; increased incidences of hepatocellular 

hypertrophy, pigment in centrilobular 

hepatocytes, eosinophilic foci of altered 

hepatocytes, vacuolation of centrilobular 

hepatocytes, bile duct hyperplasia, and bile duct 

fibrosis in both sexes; and brown pigment in the 

kidney in females.

There were increased incidences of uterine 

endometrial adenocarcinoma and liver 

hepatocellular adenoma in females at 3000 ppm.

870.6200a 

Neurotoxicity 

Screening 

Battery - Acute -

(Rat)

47746866 (2009)

Upgradable/guideline

Requires positive control data

0, 30, 250 or 2000 mg/kg/day

NOAEL = 2000 mg/kg/day.

LOAEL was not observed. Only transient 

decreases in activity, slight rearing in both sexes 

and body weight gain in females were noted. 

870.6200b

Neurotoxicity 

Screening 

Battery - 

Subchronic (Rat)

47746865 (2009)

Upgradable/guideline

Requires positive control data

0, 300, 1500, or 6000 ppm 

M: 0, 20, 98, or 382 mg/kg/day

F: 0, 25, 114, or 468 mg/kg/day

NOAEL = 98/114 (M/F) mg/kg/day.

LOAEL = 382/468 (M/F) mg/kg/day, based on 

decreased body weight gain and food 

consumption in both sexes. 

No indications of neurotoxicity were observed.
Page 35 of 67

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

Guideline 

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

870.3050

28-Day Oral 

(Dietary) 

Toxicity Study 

(Rat)

47746827 (2008)

Unacceptable/upgradable/guideline

Requires dietary formulation analyses data

0, 2000, 6000, or 12,000 ppm 

M: 0, 175, 497, or 1018 mg/kg/day

F: 0, 176, 525, or 1107 mg/kg/day

NOAEL = 1018/1107 (M/F) mg/kg/day.

LOAEL was not observed.

This study examined a metabolite of the test 

compound.

47746828 (2009)

Acceptable/guideline

0, 300, 4000, or 10,000 ppm 

M: 0, 27, 370, or 927 mg/kg/day

F: 0, 29, 388, or 906 mg/kg/day

NOAEL = 927/906 (M/F) mg/kg/day.

LOAEL was not observed. At 4000 ppm, 

increased incidences of hepatocellular 

hypertrophy, thyroid follicular cell hypertrophy; 

increased liver weight and cytochrome P450 

levels considered adaptive and/or secondary 

effects.

Metabolite of test compound was examined

870.5100 

Bacterial 

Reverse 

Mutation Test

*SYN520453 

(parent)

47746852 (2008)

Acceptable/guideline

33, 100, 333, 1000, 2500, or 5000 μg/plate

(with and without activation)

There was no evidence of induced reverse 

mutations with or without activation.

[Negative]

*47746853 (2008)

Acceptable/guideline

33, 100, 333, 1000, 2500, or 5000 μg/plate

(with and without activation)

There was no evidence of induced reverse 

mutations with or without activation.

[Negative]

*47746854 (2008)

Acceptable/guideline

10, 33, 100, 333, 1000, 2500, or 5000 

μg/mL (with and without activation)

There was no evidence of induced reverse 

mutations with or without activation.

[Negative]

47746855 (2008)

Acceptable/guideline

100, 200, 500, 1000, 2500, or 5000 

μg/plate (with and without activation)

There was no evidence of induced reverse

mutations with or without activation.

[Negative]

870.5300 

In vitro 

mammalian cell 

gene mutation 

test

47746857 (2008)

Acceptable/guideline

25, 50,100, 200, 300, 400, 800 μg/mL 

(with and without activation)

There was no evidence of induced forward 

mutations with or without activation.

[Negative]

870.5375 

In vitro 

mammalian 

chromosome 

aberration test

(human 

lymphocyte)

47746858 (2006)

Acceptable/guideline

0.63, 1.25, 2.5, 5, 10, 20, or 30 μg/mL 

(without activation)

2.5, 5, 10, 20, 30, 40, or 50 μg/mL (with 

activation)

There was no evidence of induced forward gene 

mutations with or without activation.

[Negative]

47746859 (2008) There was no evidence of induced forward gene 
Page 36 of 67

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

Guideline 

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

Acceptable/guideline

0.7, 1.4, 2.8, 5.5, 11.0, 22.0, 33.0, or 44.0 

μg/mL (without activation)

5.5, 11.0, 22.0, 44.0, 66.0, or 88.0 μg/mL 

(with activation)

mutations with or without activation.

[Negative]

47746860 (2008)

Acceptable/guideline

574.7, 1005.7, or 1760.0 μg/mL (without 

activation)

328.4, 574.7, 1005.7, or 1760.0 μg/mL 

(with activation)

There was no evidence of chromosomal 

aberrations with or without activation.

[Negative]

870.5395 

Mammalian 

erythrocyte 

micronucleus test

47746861 (2008)

Acceptable/guideline

31.8, 55.7, 298.5, or 522.4 μg/mL (without 

activation)

170.6, 298.5, or 522.4 μg/mL (with 

activation)

There was no evidence of chromosomal 

aberrations with or without activation.

[Negative]

*47746862 (2006)

Acceptable/guideline

10, 15, 20, 30, or 40 μg/mL (without 

activation)

20, 30, or 50 μg/mL (with activation)

There was no evidence of chromosomal 

aberrations with or without activation.

[Negative]

Micronucleus rat 

bone marrow

47746863 (2008)

Acceptable/guideline

3.0, 5.2, 9.1, 16.0, 16.9, 29.6, or 51.7 

μg/mL (without activation)

25.0, 29.6, 50.0, 51.7, 75.0, or 90.5 μg/mL 

(with activation)

There was no evidence of chromosomal 

aberrations with or without activation.

[Negative]

*47746864 (2008)

Acceptable/guideline

0 or 2000 μg/mL

There was no significant increase in the 

frequency of micronucleated polychromatic 

erythrocytes in bone marrow of rat.

[Negative]

870.7485 Metabolism and 

pharmacokinetics

47746867 (2008)

Pharmacokinetics

Acceptable/guideline

Following oral administration of [14C]-

SYN520453 at 1 and 75 mg/kg, the time at 

which maximum plasma concentrations (Cmax) 

were attained (Tmax) was 3-6 hours post dose. 

Pharmacokinetic parameters of radioactivity in 

blood were not appreciably different to those in 

plasma. Systemic exposure in female rats tended 

to be greater than that in male rats. Systemic 

exposure to radioactivity was approximately 

dose proportional in the range 1-75 mg/kg.

47746868 (2009) [

14C]-SYN520453 was extensively metabolized 
Page 37 of 67

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

Guideline 

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

Nonguideline 4-Week Oral 

(Capsule) 

Toxicity Study 

(Dog)

Metabolite Identification

Acceptable/guideline

by rats via oxidation to give a range of hydroxy, 

dihydroxy, acid and hydroxy acid metabolites. 

Oxidation of the demethylated metabolite of 

SYN520453 produced an equivalent range of 

demethylated metabolites. No cleavage of 

SYN520453 was observed. The major routes of 

biotransformation appeared to be independent of 

dose level and sex. Metabolite profiles 

appeared similar for both Syn and Anti isomers 

of the parent molecule. Greater than 90% of the 

administered dose was accounted for by 

identified metabolites.

47746869 (2008)

Tissue Distribution

Acceptable/guideline

There was wide distribution of [14C]-

SYN520453 and/or its metabolites after oral 

administration at 1 and 75 mg/kg with peak 

tissue concentrations at the first sampling time 

(6 and 10 hours post dose for high and lose 

dose, respectively). Thereafter, concentrations 

in all tissues declined rapidly. At 96 hours post 

dose at 1 mg/kg, low concentrations of 

radioactivity were detectable in most tissues 

investigated.

 At 96 hours post-dose at 75 mg/kg, 

radioactivity was measurable in the liver, 

kidneys, renal fat, pancreas and lungs of male 

rats and in only liver and renal fat of female rats

and in the gastrointestinal tract of male rats.

47746870 (2008)

Multiple Dose Treatment

Acceptable/guideline

Following repeated oral administration of [14C]-

SYN520453 at target dose of 1 mg/kg/day, 

steady-state tissue concentrations of total 

radioactivity appeared to be reached by day 10 

of dosing. There was no evidence of 

accumulation of radioactivity in any of the 

tissues examined. Radioactivity in tissues 

declined rapidly following cessation of dosing. 

The majority of the radioactive dose was 

eliminated in feces on both day 1 and day 14 

with urinary radioactivity accounting for 

approximately 20% of the administered dose.

47746871 (2007)

Preliminary Study

Acceptable/guideline

Following oral administration of [14C]-labeled

SYN520453 at the low dose level of 2.5 mg/kg 

or the high dose level of 250 mg/kg, residues in 

expired air were below the limit of detection at 

all time points. Whole body autoradiography 

showed that the administered radioactivity was 

distributed widely throughout the internal 

organs after 2 hours. By 48 hours after dosing 

very little radioactivity remained in the bodies 

of the rats. 
Page 38 of 67

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

Guideline 

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

47746872 (2008)

Biliary Elimination

Acceptable/guideline

Following single oral administration of 1 mg 

[

14C]-SYN520453/kg to bile duct cannulated

rats, elimination was rapid. The major route of 

elimination was via the bile. Following single 

oral administration of 75 mg [14C]-

SYN520453/kg to bile duct cannulated rats, 

elimination was rapid with the majority of the 

administered radioactivity excreted in the first 

48 hours. The major route of elimination was 

via the bile. 

47746873 (2008)

Comparison of the Elimination of 

Diastereoisomers

Acceptable/guideline

Following a single oral dose of 2 mg [Anti14C]-

SYN520453/kg, the dose was well absorbed, 

representing 61-69% of the dose. A single dose 

of 75 mg absorption was lower in males (53%) 

and higher in females (77%). Elimination was 

rapid and almost complete by 24 hours. 

Following a single oral dose of 2 mg [Syn14C]-

SYN520453/kg, 72-75% of the dose was 

absorbed. A single dose of 75 mg [Syn14C]-

SYN520453/kg absorption was lower in both 

sexes, with mean values of 66% and 49% in 

males and females (n=2), respectively. 

Elimination was rapid and almost complete by 

24 hours. There were no notable differences in 

the absorption or routes and rates of excretion 

between the Syn and Anti diastereoisomers. By 

three days after dosing carcass residues 

represented ≤0.3% of the dose.

47746874 (2008)

Mass Balance

Acceptable/guideline

Following single oral administration of 1 mg 

[

14C]-SYN520453/kg or 75 mg [14C]-

SYN520453/kg to rats, elimination was rapid 

with the majority of the administered 

radioactivity excreted by 48 hours post dose. 

The major route of elimination was via the

feces, with urinary elimination also an important 

route of excretion. The routes and rates of 

excretion were similar for males and females 

and for both the low and high dose level 

animals, although urinary excretion appeared to 

be slightly greater in females.

Seven days after dosing the low dose level, the 

liver and kidney were the only two tissues

with detectable radioactive residues. Seven days 

after dosing the high dose level, radioactive 

residues were only detectable in the liver (males 

and females) and kidney (males only). 

47746801 (2008)

Acceptable/non-guideline

NOAEL = 30 mg/kg/day.

LOAEL = 100 mg/kg/day, based on slight 

toxicity in females (decreased body weight and 
Page 39 of 67

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

Guideline 

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

0, 30, 100, or 300 mg/kg/day food consumption). 

Nonguideline 

Waiver Request 

for 

Developmental 

Neurotoxicity 

Study

47746802

Nonguideline 

In Vivo Rat 

Liver 

Unscheduled 

DNA Synthesis 

Assay

47746804 Study not provided for review.

Nonguideline

Preliminary Oral 

Toxicity Study –

(Dog)

47746805 (2007)

Acceptable/non-guideline

0, 50, 150, or 400 mg/kg/day

NOAEL = 150 mg/kg/day.

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

body weights and food consumption in both 

sexes; increased liver weights in males; 

eosinophilia and hypertrophy of periportal 

hepatocytes in males; increased serum 

triglycerides, alanine aminotransferase, 

cholesterol and creatine kinase in males;

increased alkaline phosphatase and gammaglutamyl transferase in both sexes

Nonguideline 

A 14-Day Oral 

(Dietary) RangeFinding Study –

(Rat)

47746806 (2008)

Acceptable/non-guideline

0, 4000, 8000, or 16,000 ppm 

M: 0, 353, 700, or 1535 mg/kg/day

F: 0, 331, 697, or 1532 mg/kg/day

NOAEL = 1535/1532 (M/F) mg/kg/day.

LOAEL was not observed.

Nonguideline 

Supplemental 

28-Day Oral 

(Dietary) 

Toxicity Study 

(Rat)

47746826 (2008)

Acceptable/guideline

Requires stability and homogeneity 

analyses data for formulations

0, 100, 500, or 2000 ppm 

M: 0, 9.1, 46.1, or 174.9 mg/kg/day

F: 0, 9.6, 48.1, or 191.2 mg/kg/day

NOAEL = 46.1/48.1 (M/F) mg/kg/day.

LOAEL = 174.9/191.2 (M/F) mg/kg/day, based 

on decreased body weights in females.
Page 40 of 67

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

Guideline 

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

Nonguideline 

Supplemental 

28-Day Oral 

(Dietary) 

Toxicity Study 

(Rat)

47746829 (2009)

Acceptable/non-guideline

0, 500, 2000, or 5000 ppm in syn/antiepimers (1:1), syn-epimer, and anti-epimer

45.2, 182.0, or 419.2 mg/kg/day as an 

average for combined sexes and epimers 

(calculated by reviewers)

NOAEL = 45.2 mg/kg/day.

LOAEL = 182.0 mg/kg/day based on decreased 

body weights in both sexes (1:1 mix and antiepimers); decreased food consumption in 

females (anti-epimer); increased plasma 

cholesterol in females (1:1 mix and antiepimers); decreased plasma albumin and total 

protein in females (anti-epimer); decreased 

triglycerides in males (anti-epimer); increased 

liver weights, cytochrome P450 activity, and 

incidence of hepatocellular hypertrophy in both 

sexes treated with the 1:1 mix, anti- and synepimers.

Nonguideline 

Supplemental 

28-Day Oral 

(Dietary) 

Toxicity Study 

(Mouse)

47746830 (2007)

Acceptable/non-guideline

0, 300, 3500, or 7000 ppm 

M: 0, 287.8, 593.5, or 1125.8 mg/kg/day

F: 0, 323.3, 658.0, or 1519.1 mg/kg/day

NOAEL = 593.5/658 (M/F) mg/kg/day.

LOAEL = 1125.8/1519.1 (M/F) mg/kg/day, 

based on increased liver weight, cytochrome 

P450 activities, and incidence of hepatocellular 

hypertrophy, increased total protein, decreased 

albumin/globulin, and in females, increased 

total bilirubin. 

Nonguideline 

Supplemental 

28-Day Oral 

(Dietary) 

Toxicity Study in 

(Rat)

47746831 (2007)

Acceptable/non-guideline

0, 300, 4000, or 8000 ppm 

M: 0, 29.4, 392.5, or 792.6 mg/kg/day

F: 0, 28.1, 390.1, or 720.6 mg/kg/day

NOAEL = 29.4/28.1 (M/F) mg/kg/day.

LOAEL = 392.5/390.1 (M/F) mg/kg/day, based 

on increased liver weight and incidence of 

centrilobular hepatocellular hypertrophy, 

decreased body weight, and differences in 

clinical chemistry in both sexes (increased 

triglycerides in males; increased urea, 

cholesterol, and phosphorous in females). 

Nonguideline 

Range-Finder for 

Prenatal 

Developmental 

Toxicity (New 

Zealand White

Rabbit)

47746838 (2008)

Acceptable/non-guideline

0, 400, 700, or 1000 mg/kg/day

Maternal NOAEL was not observed.

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

body weight, body weight gain, and food 

consumption; increased abortions and postimplantation loss; increased incidences of 

centrilobular hepatocyte hypertrophy and 

hepatocyte hypertrophy; decreased incidence of 

glycogen vacuolation in hepatocytes; increased 

serum gamma-glutamyl transpeptidase; and 

increased liver weight. 

Fetal NOAEL = 700 mg/kg/day.

LOAEL = 1000 mg/kg/day, based on decreased 

fetal growth, decreased survival, and increased

incidences of microphthalmia and absent/small 

gallbladder.

Nonguideline 

Preliminary 

Prenatal 

Developmental 

Toxicity (Rat)

47746839 (2007)

Acceptable/non-guideline

Requires dose formulation analyses and 

historical control data; n=10 instead of 

n=20

Maternal NOAEL = 200 mg/kg/day.

LOAEL = 350 mg/kg/day, based on decreased 

body weight and food consumption; increased 

intra-uterine death; increased incidences of 

centrilobular hepatocyte hypertrophy; and 
Page 41 of 67

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

Guideline 

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

0, 200, 350, or 500 mg/kg/day increased liver weight. 

Fetal NOAEL = 200 mg/kg/day.

LOAEL = 350 mg/kg/day, based on decreased 

fetal weights.

Nonguideline 

Range-Finder for 

Prenatal 

Developmental 

Toxicity 

(Himalayan 

Rabbit)

47746841 (2008)

Acceptable/non-guideline

0, 600, 800, or 1000 mg/kg/day

Maternal NOAEL = 1000 mg/kg/day.

LOAEL was not observed in maternal animals.

Fetal NOAEL was not observed.

LOAEL = 600 mg/kg/day for fetal toxicity, 

based on an increased incidence of 

microphthalmia.

Nonguideline 

Range-Finder for 

Prenatal 

Developmental 

Toxicity in 

(Himalayan 

Rabbit)

47746842 (2008)

Acceptable/non-guideline

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

Maternal NOAEL = 400 mg/kg/day.

LOAEL was not observed in maternal animals.

Fetal NOAEL = 200 mg/kg/day.

LOAEL = 400 mg/kg/day for fetal toxicity, 

based on slightly increased incidence of 

microphthalmia.

Nonguideline 

Range-Finder for 

Prenatal 

Developmental 

Toxicity – (Rat)

47746844 (2008)

Acceptable/non-guideline

n=10 instead of n=20

0, 60, 125, or 250 mg/kg/day

Maternal NOAEL was not observed.

LOAEL = 60 mg/kg/day, based on decreased 

body weight gain. 

Fetal NOAEL = 60 mg/kg/day.

LOAEL = 125 mg/kg/day, based on decreased 

body weight and delayed ossification that may 

be secondary to the maternal toxicity.

Nonguideline 

Supplementary 

Reproduction 

and Fertility 

Effects (Rat)

47746846 (2006)

Acceptable/non-guideline

0, 1000, 2000, or 3000 ppm 

M: 0, 76.1, 151.6, or 223.2 mg/kg/day

F: 0, 87.3, 175.1, or 274.9 mg/kg/day

Parental NOAEL was not observed.

LOAEL = 76.1/87.3 (M/F) mg/kg/day, based on 

increased liver weights in both sexes. 

Reproductive NOAEL = 151.6/175.1 (M/F) 

mg/kg/day.

LOAEL was not observed.

Offspring NOAEL was not observed.

LOAEL = 76.1/87.3 (M/F) mg/kg/day, based on 

increased liver weight in both sexes.

Nonguideline 

Rat Control 

Study for 

Combined 

Chronic 

Toxicity/ 

Carcinogenicity

47746850 (2008)

Acceptable/non-guideline

0 mg/kg/day 

All animals were control animals (untreated), 

providing a source of historical control data for 

OPPTS 870.4300.
Page 42 of 67

A.3 Hazard Identification and Endpoint Selection

A.3.1 Acute Reference Dose (aRfD) – All Populations

Study Selected: Subchronic Toxicity (Oral)/Dog

MRID No.: 47746836

Executive Summary: See Appendix A, Guideline [§ 870.3150]

Dose and Endpoint for Establishing aRfD: NOAEL = 30 mg/kg. The LOAEL is 100 

mg/kg/day based on side-to-side head wobble/shake displayed in one of four male dogs 

beginning on Day 2 and continuing throughout the study. At 300 mg/kg/day, three of four male 

dogs displayed side-to-side head wobble/shake on Days 2 and/or 3 only. These signs were 

generally transient and the dogs recovered within hours of dosing. This effect was considered to 

be acute.

UF(s): 100X [10 interspecies; 10X intraspecies]; FQPA SF = 1X

Comments on Study/Endpoint/UFs: This study provides the lowest NOAEL in the database 

(most sensitive endpoint) for a single dose effect is the most protective limit for human effects. 

This endpoint is considered to occur following a single dose and is applicable to the population 

of concern (general population, including infants and children). It is considered to be a very 

conservative endpoint since it is based on observations in 1/4 dogs. This effect is also protective 

of the effects seen at the limit dose (2000 mg/kg/day) in the Acute Neurotoxicity study 

(decreased rearing and locomotor activity) and the developmental effect (bilateral 

microphthalmia) in the developmental rabbit studies (at doses ≥400 mg/kg/day). Therefore, a 

separate acute dietary endpoint for females of reproductive age is not necessary. 

aRfD = 30 mg/kg/day (NOAEL) = 0.30 mg/kg/day

 100 (UF)

A.3.2 Chronic Reference Dose (cRfD) – All Populations

Study Selected: Chronic Toxicity/Carcinogenicity (Feeding)/Rat

MRID No.: 47746851

Executive Summary: See Appendix A, Guideline [§ 870.4300]

Dose and Endpoint for Establishing cRfD: The NOAEL is 5.5 mg/kg/day. The LOAEL is 

27.6 mg/kg/day based on based on decreased body weight and body weight gain in females; 

increased incidences of hepatocellular hypertrophy, pigment in centrilobular hepatocytes, 

eosinophilic foci of altered hepatocytes, vacuolation of centrilobular hepatocytes, bile duct 

hyperplasia, and bile duct fibrosis in both sexes; and brown pigment in the kidney in females.

UF(s): 100X [10 interspecies; 10X intraspecies]; FQPA SF = 1X 
Page 43 of 67

Comments about Study/Endpoint/UF: This study provides the lowest NOAEL in the database 

(most sensitive endpoint) and is considered to be protective. Similar effects on the same target 

organ (liver) are seen across multiple species in this database.

cRfD = 5.5 mg/kg/day (NOAEL) = 0.055 mg/kg/day

 100 (UF)

A.4 Executive Summaries

A.4.1 Subchronic Toxicity

870.3100 90-Day Oral Toxicity – Rat

In a subchronic oral toxicity study (MRID 47746833), 10 Wistar rats/sex/dose were administered 

either SYN520453 (89.5% Syn: 6.9% Anti; 96.4% a.i., Batch No. SMU6AP001) or SYN520453 

(63.3% Syn: 27.5% Anti; 90.8% a.i., Batch No. SMU7DP017) via the diet at concentrations of 0, 

100, 250, or 2000 ppm (equivalent to approximately 8.3/8.2, 20.3/20.8, and 158.7/163.3 

mg/kg/day [M/F] of SYN520453 [89.5% Syn: 6.9% Anti] and 9.9/9.5, 24.1/24.1, and 

192.9/197.0 mg/kg/day [M/F] of SYN520453 [63.3% Syn: 27.5% Anti]) for at least 90 days. 

The purpose of this study was to compare the oral toxicity effects of two test materials 

containing different concentrations of the Syn- and Anti epimers of SYN520453.

No treatment-related effects were noted on mortality, clinical signs of toxicity, ophthalmoscopic 

examinations, FOB, motor activity, hematology, urinalysis, or gross pathology at any dose in 

either sex.

At 2000 ppm, absolute liver weights were increased by 15-18% in both sexes in both test 

material groups. Additionally at this dose, relative (to body) liver weights were increased by 15-

19% in both sexes in both test material groups. The incidence (# affected/10 vs. 0/10 controls) 

of minimal to moderate centrilobular hypertrophy was increased in the males (8 in each test 

material group) and females (10 in each test material group). Additionally at this dose, the 

incidence of hepatocyte midzonal vacuolation was increased in the males (3-4 per test material 

group; minimal to mild severity) and females (4 in each test material group; minimal severity). 

At 2000 ppm, cumulative body weight gains were decreased by 11-19% and 11-16% 

(SYN520453 [89.5% Syn: 6.9% Anti] and SYN520453 [63.3% Syn: 27.5% Anti], respectively) 

in the females beginning the second week of treatment and continuing throughout the study. 

Additionally at this dose, body weights were decreased (p<0.05) by 6-10% on Days 14-91 in the 

SYN520453 (89.5% Syn: 6.9% Anti) treated females. Body weights were also decreased 

throughout the study in the females treated with SYN520453 (63.3% Syn: 27.5% Anti) at this 

dose, but only achieved statistical significance (p<0.05) on Days 77 and 91 (decr 6-7%). In the 

males treated with SYN520453 (63.3% Syn: 27.5% Anti) at 2000 ppm, body weights were 

decreased by 6-7% on Days 7, 35, and 56-77, and cumulative body weight gains were decreased 
Page 44 of 67

by 10-14% during Days 0-7 and 0-70. In the females, overall (Weeks 1-13) food utilization was

also decreased by 11-15% in both test material groups.

No treatment-related findings were observed at 100 or 250 ppm in either sex in either test 

material group. There were no differences in the toxicological profile of the two test materials in 

this comparative study.

The LOAEL is 2000 ppm (equivalent to 158.7/163.3 mg/kg bw/day in males/females) for 

SYN520453 [89.5% Syn: 6.9% Anti], based on decreased body weight in females on Day 91, a 

reduction in bodyweight gain and food consumption and liver changes in the form of 

centrilobular hepatocyte hypertrophy and midzonal vacuolation and increased liver weight. No 

adverse effects were seen at the lower exposure levels of 100 and 250 ppm. The NOAEL is 250 

ppm (equivalent to 20.3/20.8 mg/kg bw/day in males/females. Overall, this study 

demonstrates that the short-term toxicity of the SYN520453 (89.5% Syn: 6.9% Anti) and 

SYN520453 (63.3% Syn: 27.5% Anti) epimeric mixtures of Isopyrazam are qualitatively and 

quantitatively similar.

This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 

870.3100a; OECD 408) for a subchronic oral toxicity study in the rat.

870.3100 90-Day Oral Toxicity – Mouse

- NA -

870.3150 90-Day Oral Toxicity – Dog

In this subchronic oral toxicity study (MRID 47746836), 4 beagle dogs/sex/group were 

administered SYN520453 (Isopyrazam; 96.4% a.i., Batch # SMU6AP001) daily via gelatin 

capsule at doses of 0, 30, 100, or 300 mg/kg/day for 13 weeks.

All dogs survived until scheduled termination. No treatment-related effects were observed on 

ophthalmoscopic examination parameters, urinalysis, or histopathology. 

At 100 mg/kg/day, one male displayed side-to-side head wobble/shake beginning on Day 2 and 

continuing throughout the study. Also at this dose, overall body weight gains (calculated by 

reviewers) were decreased by 30-57% in both sexes. Effects on clinical chemistry parameters 

included increased (p<0.05 or not statistically significant) alkaline phosphatase activity in the 

males (incr 33-55%) at Weeks 8 and 13 and in the females (incr 42-52%) at Weeks 4, 8, and 13, 

and decreased albumin (decr 5%, p<0.05) in the females at Week 13. Additionally, adjusted for 

body weight liver weight was increased (p<0.05) by 13% in the males.

At 300 mg/kg/day, three males displayed abnormal clinical signs (including side-to-side head 

wobble/shake, ataxia, and reduced stability) on Days 2 or 3. These signs were generally
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transient and the dogs recovered within hours of dosing. No abnormal signs were observed 

from Day 4 onward despite continued dosing in all 300 mg/kg bw/day animals. There was one 

100 mg/kg/day male that displayed side to side head wobble/shake beginning on Day 2 and 

continuing throughout the study and decreased activity. These effects were considered to be 

transient signs of toxicity that resolved within hours on each day of dosing, therefore could be 

considered acute signs of toxicity.

Body weights were decreased in the males throughout treatment and attained statistical 

significance (p<0.05) during Weeks 2-4, 7, 9, 10, and 12-14. Body weights were also decreased 

in the females at this dose during Weeks 5-14 (decr 3-12%, p<0.05). Overall (Weeks 1-14) body 

weight gains were decreased by 82% in the males and the females lost weight during the study (-

0.05 kg treated vs. 1.15 kg controls). Food consumption was decreased throughout the study in 

both sexes and attained statistical significance (p<0.05) in the males during Weeks 1-6 and 11 

(decr 11-25%), and in the females during Weeks 5, 9, and 11-13 (decr 14-22%). The following 

clinical chemistry parameters differed significantly (p<0.05, unless otherwise noted) from the 

controls: (i) increased alkaline phosphatase in the males (incr 40-114%) and females (incr 105-

142%) at Weeks 4, 8, and 13; (ii) decreased cholesterol in the males (decr 21%, not significant at 

Week 13) and females (decr 23-25%) at Weeks 4, 8, and 13; (iii) decreased albumin in the males 

(decr 9%) at Week 13 and in the females (decr 7-10%) at Weeks 4, 8, and 13; (iv) decreased total 

protein in the males (decr 8%) at Week 13 and females (decr 6-12%) at Weeks 4, 8, and 13; and 

(v) decreased sodium (decr 4%) in the females at Week 13. Also at this dose, enlarged liver was 

observed in 2/4 males and females each (vs. 0/4 controls each), and liver weights (absolute and 

adjusted for body weight) were increased in the males (incr 24% each). There were no 

microscopic findings that were considered to be treatment related. 

Additionally, the number of platelets was increased (p<0.01) by 33% over controls in the 300 

mg/kg/day males at Week 13; however, this finding is of equivocal toxicological importance.

The LOAEL is 100 mg/kg/day based on decreased body weight gains, clinical signs of toxicity 

(side-to-side head wobble/shake in one male), increase alkaline phosphatase activity in both 

sexes, and increased adjusted for body weight liver weight in males. The NOAEL is 30 

mg/kg/day.

This study is classified acceptable/guideline and satisfies the guideline requirements (OPPTS 

870.3150; OECD 409) for a subchronic oral toxicity study in dogs.

870.3200 21/28-Day Dermal Toxicity – Rat

- NA -

870.3465 90-Day Inhalation – Rat

- NA -
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A.4.2 Prenatal Developmental Toxicity

870.3700a Prenatal Developmental Toxicity Study – Rat

In a developmental toxicity study (MRID 47746843/44), SYN520453 (Isopyrazam; 90.8%; 

Batch No. SMU7DP017) in 0.5% (w/v) aqueous carboxymethylcellulose was administered via 

daily oral gavage in a dose volume of 10 mL/kg to 24 time-mated Han Wistar (HanRcc:WIST) 

rats/dose group at doses of 0, 20, 75, or 200 mg/kg/day from gestation days (GD) 4-20. On GD 

21, all dams were euthanized; each dam’s uterus was removed via cesarean section and its 

contents examined. Fetuses were examined for external, visceral, and skeletal malformations 

and variations.

No treatment-related effects were observed on mortality, gross pathology, or cesarean section 

data.

At 75 mg/kg/day, maternal food consumption was decreased throughout treatment (GD 4-21) by 

9-15%, resulting in decreased body weights (decr. 3-5%) during GD 6-21, and decreased 

cumulative body weight gains relative to GD 4 (decr. 13% on GD 21). These dams had a body 

weight loss (-0.7 g treated vs. +5.3 g controls) on GD 6. Cumulative body weight gains (relative 

to GD 4) corrected for gravid uterus weight were decreased by 41%.

At 200 mg/kg/day, maternal food consumption was decreased throughout treatment (GD 4-21) 

by 28-41%, resulting in decreased body weights (decr. 5-17%) during GD 5-21. Dams displayed 

body weight losses during GD 5-10 (-2.0 to -11.0 g treated vs. +3.1 to +22.6 g controls). 

Cumulative body weight gains on GD 21 (relative to GD 4) were decreased by 48%. When 

corrected for uterus weights, a cumulative body weight loss (relative to GD 4) of -5.7 g was 

noted at 200 mg/kg/day, compared to a 34.2 g gain in controls. Additionally, ventral 

recumbency and sedation were noted in 18-24 dams during GD 4-9. Ventral recumbency was 

also noted sporadically in 1-3 dams during GD 13-18. Sedation was also noted in 1-5 dams 

during GD 13-20. Ruffled fur was observed in 1-6 dams during GD 13-21.

The maternal LOAEL is 75 mg/kg/day, based on decreased body weights, body weight 

gains, and food consumption. The maternal NOAEL is 20 mg/kg/day.

There were no abortions, premature deliveries, complete litter resorptions, or dead fetuses and no 

effects of treatment on the numbers of litters, live fetuses, or resorptions. Similarly, sex ratio and 

post-implantation losses of the treated groups were comparable to controls.

Fetal weights were decreased by 6% at 75 mg/kg/day and by 17-18% at 200 mg/kg/day. At 75 

mg/kg/day, the incidence of non-ossified cervical vertebral body 3 was increased on a litter basis, 

and the incidence of non-ossified left and right talus of the left and right hindlimbs were 

increased on a fetal basis. At 200 mg/kg/day, higher incidences of non-ossified and/or 

incompletely ossified vertebral bodies, proximal phalanges, talus, and metartarsalia were 

observed. Due to the reduced fetal body weights at 75 mg/kg/day and above, these increased 
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incidences were considered to be a result of delayed development secondary to maternal toxicity.

There were no treatment-related external, visceral, or skeletal variations or malformations.

The developmental LOAEL is 75 mg/kg/day, based on decreased fetal body weights and 

increased incidences of non-ossification or incomplete ossification secondary to maternal 

toxicity. The developmental NOAEL is 20 mg/kg/day.

This study is classified acceptable/guideline and satisfies the guideline requirement for a 

developmental toxicity study (OPPTS 870.3700; OECD 414) in rats.

870.3700b Prenatal Developmental Toxicity Study – Rabbit

Definitive Study

In a developmental toxicity study (MRID 47746840), SYN520453 (Isopyrazam; 96.4%; Batch 

No. SMU6AP001) in 0.5% (w/v) aqueous carboxymethylcellulose was administered via daily 

oral gavage in a dose volume of 10 mL/kg to 25 time-mated New Zealand White 

(Hra:[NZW]SPF) rabbits/dose group at doses of 0, 30, 150, or 500 mg/kg/day from gestation 

days (GD) 7-28. On GD 29, all does were euthanized; each doe’s uterus was removed via 

cesarean section and its contents examined. Fetuses were examined for external, visceral, and 

skeletal malformations and variations.

No treatment-related effects were observed on body weights, body weight gains, or cesarean 

section data.

Maternal toxicity was observed at 500 mg/kg/day. One female was found dead on GD 24. This 

animal had red material in the cage pan on the day prior to death. This animal also displayed 

decreased food consumption with corresponding body weight losses and/or decreased defecation 

during GD 10-15; body weight losses were noted again on GD 20-23. At necropsy, dark red 

discoloration of the lungs and 9 late resorptions in utero were observed, although the cause of 

death could not be determined. Additionally at this dose, food consumption was decreased by 

13-39% during GD 7-17, resulting in an 8% decrease during treatment (GD 7-29). An increased 

incidence of decreased defecation was noted in 12 females compared to 4 controls. This finding, 

primarily noted during GD 13-17, generally correlated with reduced food consumption. 

Absolute and relative (to net body weight) liver weights were increased by 36-37%. Minimal to 

mild hepatocellular hypertrophy was observed in 14/23 does compared to 0 controls. Glycogen 

vacuolation was observed to decrease (3/23 does with minimal severity) compared to controls 

(18/23 does with minimal to moderate severity). Minimal to moderate centrilobular 

hepatocellular vacuolation was noted in 13/23 does compared to 0 controls.

At 150 mg/kg/day, absolute and relative (to net body weight) liver weights were increased by 13-

15%, and minimal hepatocellular hypertrophy was observed in 4/23 does compared to 0 controls. 

These findings were considered to represent a non-adverse, adaptive response of the liver to 
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administration of the test compound.

The maternal LOAEL is 500 mg/kg/day, based on mortality, decreased food consumption, 

decreased defecation, increased liver weights, and microscopic findings in the liver. The 

maternal NOAEL is 150 mg/kg/day.

There were no abortions, premature deliveries, complete litter resorptions, or dead fetuses and no 

effects of treatment on the numbers of implantations, litters, live fetuses, early resorptions, or late 

resorptions. Sex ratio and post-implantation losses of the treated groups were comparable to 

controls. At 500 mg/kg/day, fetal weights were decreased by 8%. This small decrease was 

considered secondary to the slightly larger litter size in this group compared to the controls 

(mean litter size 8.8 treated vs. 7.9 controls).

Bilateral microphthalmia was observed in one 500 mg/kg/day fetus compared to 0 concurrent 

controls. Although this was within the range of the historical controls, a treatment-related 

increase in this finding was observed at a higher dose level (1000 mg/kg/day) in a concurrently 

reviewed range-finding developmental toxicity study in rabbits (MRID 47746838). There were 

no treatment-related visceral, or skeletal malformations, and no treatment-related external, 

visceral, or skeletal variations.

The developmental LOAEL is 500 mg/kg/day, based on bilateral microphthalmia. The 

developmental NOAEL is 150 mg/kg/day.

This study is classified acceptable/guideline and satisfies the guideline requirement for a 

developmental toxicity study (OPPTS 870.3700b; OECD 414) in rabbits.

Range Finding Study 1 - Himalayan Rabbit

MRID 47746842 SYN520453 – Dose Range-Finding Prenatal Developmental Toxicity

Study in the Himalayan Rabbit (Including First Amendment to Final Report)

In this preliminary developmental toxicity study, doses of 100, 200 and 400 mg/kg/day were

administered to pregnant Himalayan rabbits. Slightly decreased maternal food consumption was 

observed at 400 mg/kg/day. There were no effects on maternal body weight or body weight gain.

The finding of small eyes at 400 mg/kg/day was possibly related to treatment. 

Acceptable/Non- Guideline

Range Finding Study 2 - Himalayan Rabbit

MRID 47746841 SYN520453 – Second Dose Range-Finding Prenatal Developmental Toxicity 

Study in the Himalayan Rabbit. In this second preliminary developmental toxicity study, doses 

of 0, 600, 800, and 1000 mg/kg/day were administered to pregnant Himalayan rabbits.

No overt maternal toxicity was noted in any of the treatment groups. Food consumption was

slightly decreased throughout treatment in females given 1000 mg/kg/day. Reproductive

parameters were unaffected in any treatment group. Administration of SYN520453 at 600, 800, 
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and 1000 mg/kg/day to pregnant Himalayan rabbits was associated with intraocular 

abnormalities, consistent with microphthalmia, and other eye variations in all dose groups.

Acceptable/Non- Guideline
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Range Finding Study 3 – New Zealand White Rabbit

MRID 47746838 SYN520453 – A Dose Range-Finding Prenatal Developmental Toxicity Study

in New Zealand White Rabbits Maternal toxicity in the form of moribundity, abortion, 

decreased food consumption, reduced mean body weight gain and/or increased liver weights 

accompanied by microscopic alterations was observed at all dose levels tested. Treatment-related 

effects on fetal developmental parameters were observed at 1000 mg/kg/day. Therefore, dose 

levels of 30, 150 and 500 mg/kg/day were selected for the definitive developmental toxicity 

study with SYN520453 in the New Zealand White rabbit.

Acceptable/Non- Guideline

A.4.3 Reproductive Toxicity

870.3800 Reproduction and Fertility Effects – Rat

In a two-generation reproduction toxicity study (MRID 47746847), isopyrazam (SYN520453; 

96.4% a.i.; Lot No. SMU6AP001) was administered to Wistar rats in the diet at concentrations of 

0, 100, 500, or 3000 ppm (equivalent to 0/0, 8.9/9.8, 44.5/48.4, and 269.3/289.0 mg/kg/day in 

males/females) for two consecutive generations. The P generation animals (26/sex/dose group) 

were administered the test compound for 10 weeks prior to mating to produce the F1 litters. F1 

offspring selected to be parents of the next generation (26/sex/dose group, except 25/sex/dose in 

the control group) were administered the same concentrations as their parents. After weaning, 

F1 parents were administered the compound for at least 10 weeks prior to mating to produce the 

F2 litters. The F2 offspring were terminated after weaning.

No treatment-related effect was observed on mortality, clinical signs or gross or histological 

pathology.

In the 500 ppm F1 females, body weights were decreased by 2-9% throughout pre-mating, and 

body weight gain during the pre-mating period (Weeks 1-11) was decreased by 12%. Food 

consumption was decreased by 7-13% throughout pre-mating (except Week 3). Body weight 

was decreased on gestation day (GD) 1 by 8%, and body weight gain during the gestation period 

(GD 1-22) was deceased by 7%. Food consumption was decreased in the first week of gestation 

by 13%. Body weight was decreased on lactation day (LD) 1 by 9%, but body weight gain for 

the lactation period (LD 1-29) was similar to controls.

At 3000 ppm, decreases in body weights were noted during the pre-mating period as follows: (i) 

in the P males and females throughout pre-mating; (ii) in the F1 males during Weeks 1, 4-8, and 

10-11; and (iii) in the F1 females during Weeks 1 and 7-11. Decreased body weight gain during 

the pre-mating period (Weeks 1-11) was observed in both sexes and generations. Decreases in 

food consumption were noted as follows: (i) in the P and F1 males throughout pre-mating; (ii) in 

the P females during Weeks 3 and 6-10; and (iii) in the F1 females throughout pre-mating. 

Decreased food utilization during pre-mating (Weeks 1-10) was noted in the P generation in both 

sexes. 
Page 51 of 67

At 3000 ppm in the P and F1 dams, decreases in body weights were noted throughout gestation, 

and body weight gain during the gestation period (GD 1-22) was decreased. Food consumption 

was decreased during Weeks 1 and 2 of gestation.

At 3000 ppm, decreases in body weights were noted in the P and F1 dams throughout lactation, 

except on LD 5 in the P generation. Body weight gain during the lactation period (LD 1-29) was 

decreased in the P dams. Food consumption was decreased during Weeks 2-4 of lactation in the 

P dams and during Weeks 2-3 in the F1 dams.

Increased adjusted (for terminal body weight) thyroid gland weights were noted in the 500 (incr 

14%) and 3000 (incr 43%) ppm P males, but were not observed in the females or the F1 

generation. No gross lesions were noted on the thyroid, but microscopic examination was not 

performed on the thyroid. Consequently, the effect on the thyroid at 3000 ppm was considered 

equivocal.

The LOAEL for parental toxicity was 500 ppm (equivalent to 44.5/48.4 mg/kg/day in 

males/females), based on decreased body weights, body weight gains, and food 

consumption in the F1 females during the pre-mating and gestation periods. The NOAEL 

is 100 ppm (8.9/9.8 mg/kg/day in males/females).

There were no treatment-related effects on clinical signs or the live birth, viability, or lactation 

indices. No treatment-related effect was observed on mean litter size (including whole litter 

losses), post-implantation loss, whole litter loss, pup sex ratio, anogenital distance, or on gross 

pathology. 

At 3000 ppm, body weights were decreased by 7-19% in both sexes and both generations on 

PND 15-29 and by 9% in the F2 females on PND 8. 

At 3000 ppm, F1 males had a delay in preputial separation (2.3 days), and F1 females had a 

delay in the time of vaginal opening (2 days). The delayed sexual maturation was likely due to 

the slower growth in these animals. 

Liver weights, adjusted for terminal body weight, were increased in F1 and F2 pups in the 500 

(incr 6-14%) and 3000 (incr 23-32%) ppm groups. No gross hepatic lesions were observed, but 

histological examination was not performed. This effect may have been adaptive as in the 

parents. 

The LOAEL for offspring toxicity was 3000 ppm (equivalent to 269.3/289.0 mg/kg/day in 

males/females), based on decreased body weight in both sexes and both generations from 

PND 15 thru PND 29. The NOAEL was 500 ppm (equivalent to 44.5/48.4 mg/kg/day in 

males/females).
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No treatment-related effect was observed on the mean estrous cycle length of P and F1 females 

or on the number of cycles in the 21 day period. There were no effects on epididymal sperm 

number, velocity, straightness, or motility. Sperm morphology in the 3000 ppm males of each 

generation was similar to the concurrent controls. No effect on reproductive performance was 

observed. The fertility and gestation indices in the treated groups were comparable to controls in 

both generations. The pre-coital interval, number of pairs achieving pregnancy, and the gestation 

duration in the treated groups were also comparable to controls. There was no effect on small 

follicle counts in the ovaries of the 3000 ppm F1 females.

The LOAEL for reproductive toxicity was not observed. The NOAEL was 3000 ppm 

(equivalent to 269.3/289.0 mg/kg/day in males/females).

This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 

870.3800; OECD 416) for a two-generation reproduction study in the rat. 

A.4.4 Chronic Toxicity

870.4100a (870.4300) Chronic Toxicity – Rat – See A.4.5

870.4100b Chronic Toxicity – Dog

In a chronic oral toxicity study (MRID 47746848), 4 beagle dogs/sex/group were administered 

SYN520453 (Isopyrazam; 96.4% a.i., Batch No. SMU6AP001) daily via gelatin capsule at doses 

of 0, 25, 100, or 250 mg/kg/day for 52 weeks.

No adverse, treatment-related effects were observed on mortality, clinical signs of toxicity, 

ophthalmoscopic examinations, hematology, urinalysis, gross pathology, or histopathology.

At 250 mg/kg/day, males lost weight during Weeks 1-5 and females lost weight during Weeks 1, 

2, 4, and 5. Cumulative body weight gains remained decreased at this dose by 45-92% in the 

males throughout the remainder of the study. In the females, cumulative body weight gains were 

decreased by 68-97% during Weeks 3 and 6-10. Body weight gains remained generally 

decreased in these females throughout the study, but did not attain statistical significance. Food 

consumption was decreased by 6-28% in the males during Weeks 1-23, and attained statistical 

significance (p<0.05) at Weeks 1-5, 9, 13, and 22. Similar decreases (decr 8-28%) were 

observed in the females at this dose during Weeks 1-13, but only attained statistical significance 

at Weeks 1 and 3. Treatment-related effects on clinical chemistry parameters at this dose 

included the following: (i) alkaline phosphatase activity was increased (p<0.05) in the males 

(incr 187-315%) at all time points and in the females (incr 93-172%) at Weeks 26 and 52; (ii) 

albumin was decreased (p<0.05) at all time points in the males (decr 17-19%) and females (decr 

10-15%); (iii) total protein was decreased (p<0.05) in the males (decr 10-13%) at Weeks 26 and 

52 and in the females (decr 8%) at Week 52; (iv) bilirubin levels were decreased (p<0.01) by 

33-48% in the males at Weeks 13 and 52; (v) alanine aminotransferase was increased (p<0.05) 

by 194% in the males at Week 52; and (vi) glutamate dehydrogenase was increased by 433-
Page 53 of 67

730% in the males at Weeks 26 and 52. Additionally at this dose, absolute and adjusted for body 

weight liver (with gall bladder) weights were increased (p<0.05) by 40-53% in the males. 

At 100 mg/kg/day, cumulative body weight gains were decreased by 27-70% throughout the 

study in the males. Treatment-related differences (p<0.05) in clinical chemistry parameters at 

this dose included: (i) increased alkaline phosphatase (incr 143-174%) in the males and females 

at Week 52; (ii) decreased albumin (decr 12-13%) at all time points in the males; and (iii) 

decreased bilirubin (decr 48%) in the males at Week 52. Additionally at this dose, adjusted for 

body weight liver weight was increased (p<0.05) by 42% in the males.

At 25 mg/kg/day, the only possible treatment-related effect was an increase in alkaline 

phosphatase activity (incr 123%) in the males at Week 52. However, in the absence of any 

microscopic changes or changes in other parameters at this dose, this finding was considered to 

be of no toxicological significance.

The LOAEL was 100 mg/kg/day based on decreased body weight gains in males, clinical 

chemistry effects (increased alkaline phosphatase in both sexes, and decreased albumin and 

bilirubin in males), and increased liver weight in males. The NOAEL is 25 mg/kg/day.

This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 

870.4100b; OECD 452) for a chronic oral toxicity study in dogs. 

A.4.5 Carcinogenicity

870.4200a Carcinogenicity/Chronic Study – rat

In a combined chronic toxicity/carcinogenicity study (MRID 47746851), 52 Wistar rats/sex/dose 

were exposed to Isopyrazam (96.4% a.i.; Lot No.: SMU6AP001) for up to 2 years in the diet at 

concentrations of 0, 100, 500, or 3000 ppm (equivalent to 0/0, 5.5/6.9, 27.6/34.9, and 

173.5/232.8 mg/kg bw/day in males/females). Additionally, 12 rats/sex/dose were treated 

similarly for up to 1 year and then sacrificed. 

No adverse, treatment-related effects were observed on survival, hematology, or urinalysis.

The incidence of the clinical observation “thinness” was increased in the 500 and 3000 ppm 

females (22-27 observations in 10-13 animals) compared to controls (10 observations in 5 

animals). Body weights were decreased generally from Week 5 through 105 in the 500 ppm 

females and throughout treatment in the 3000 ppm males and females. Body weight gains during 

the first 13 weeks were decreased by 6-20% in the 500 and 3000 ppm females and by 11% in the 

3000 ppm males. Overall (Weeks 1-105) body weight gains were decreased by 15-37% in the 

500 and 3000 ppm females and by 16% in the 3000 ppm males.

At 3000 ppm, food consumption was sporadically decreased by 3-11% in the males, generally 

during the first 11 weeks and by 4-8% in the females, generally during the first 14 weeks. Food 
Page 54 of 67

utilization was decreased by 4-13% in males and 11-16% in females during Weeks 1-4, 5-8, and 

9-12. Food utilization for Weeks 1-12 was decreased by 7% in males and 15% in females.

In the 3000 ppm females, hind-limb grip strength was decreased by 29%. Motor activity was 

increased by 95% during Minutes 36-40, contributing to an increase of 24% in the overall 

(Minutes 1-50) activity.

In females, increased (statistical analysis not performed) incidences of small linear opacity in the 

cornea was noted at 3000 ppm (14% treated vs 2% controls), and prominent suture lines in the 

eye were noted at 500 and 3000 ppm (11-16% treated vs 2% controls).

The following findings may be indicative of hepatotoxicity. Increased γ-glutamyl transferase 

was noted in the 500 ppm males during Weeks 53, 79, and 105, in the 3000 ppm males during 

the interim kill and during Weeks 53, 79, and 105, and in the 3000 ppm females during Week 

105. Increased alanine aminotransferase was noted in the 3000 ppm males during Weeks 53 and 

105. Adjusted liver weights were increased in the 3000 ppm group at the interim and terminal 

kills. In the 3000 ppm females, increased incidences of liver mass (9/64 treated vs 0/64 controls)

and pale spot/s or area/s on liver (10/64 treated vs 1/64 controls) were observed. At the interim 

sacrifice, increased incidences were noted in the following findings in the liver (# affected/12 in 

treated vs controls): (i) hepatocyte vacuolation in the 500 and 3000 ppm males (10-11 vs 1; 

minimal to slight) and females (8 each vs 0; minimal); (ii) minimal to slight hepatocyte 

hypertrophy in the 500 and 3000 ppm males (4-12 vs 0) and females (9-12 vs 0); and (iii) 

increased hepatocyte/Kupffer cell pigmentation in the 3000 ppm males (6 vs 0; minimal to 

slight) and females (10 vs 3; minimal). At the terminal sacrifice including decedents, increased 

incidences were noted in the following findings in the liver (# affected/52 in treated vs controls): 

(i) minimal to moderate centrilobular hepatocellular hypertrophy in the 500 and 3000 ppm males 

(45-49 vs 0) and females (49-50 vs 0); (ii) minimal to moderate centrilobular hepatocellular 

vacuolation in the 500 and 3000 ppm males (32-39 vs 3); (iii) bile duct hyperplasia in 500 and 

3000 ppm males (12-19 vs 3; minimal to slight) and the 3000 ppm females (23 vs 15; NS; 

minimal to moderate); (iv) minimal to slight bile duct fibrosis in the 500 and 3000 ppm males 

(10-12 vs 1) and females (11-12 vs 6); and (v) focal eosinophilic altered hepatocytes in the 500 

and 3000 ppm males (23-32 vs 7; minimal to moderate) and females (26-29 vs 9; minimal to 

slight).

Increased plasma urea was noted in the 3000 ppm females during Weeks 53 and 105. At the 

terminal sacrifice including decedents (n=52), the incidence of minimal to slight brown pigment 

in renal tubules was increased in the 500 and 3000 ppm females (30-42/52 treated vs 18/52 

controls).

Decreased plasma triglyceride levels were noted in 3000 ppm males throughout the study and in 

3000 ppm females during Weeks 53, 79, and 105. In the 3000 ppm females, increased 

incidences of pale spot/s or area/s on lung (21/64 treated vs 11/64 controls) were observed. At 

the terminal sacrifice including decedents, the incidence of minimal to severe focal follicular 

hyperplasia was increased in the thyroid gland of the 3000 ppm males (18/52 treated vs 11/52 
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controls). These findings were without corroborating evidence of an adverse effect.

The LOAEL for toxicity is 500 ppm (equivalent to 27.6/34.9 mg/kg/day), based on 

decreased body weight and body weight gain in females; increased incidences of 

hepatocellular hypertrophy, pigment in centrilobular hepatocytes, eosinophilic foci of 

altered hepatocytes, vacuolation of centrilobular hepatocytes, bile duct hyperplasia, and 

bile duct fibrosis in both sexes; and brown pigment in the kidney in females.

The NOAEL is 100 ppm (equivalent to 5.5/6.9 mg/kg/day in males/females).

At the doses tested, there was a treatment related increase in tumor incidence when compared to 

controls. In the 3000 ppm females, increased (p≤0.01) incidences of hepatocellular adenoma 

(11/64 treated vs 0/64 controls) and endometrial epithelial adenocarcinoma (15/64 treated vs 

1/64 controls) were observed. In the 3000 ppm males, increased incidences of thyroid follicular 

cell adenoma (7/64 treated vs 1/64 controls) and testis interstitial cell adenoma (7/64 treated vs 

3/64 controls) were noted; however, these effects are considered equivocal. Dosing was 

considered adequate based on decreased body weights and body weight gains and hepatotoxicity 

in both sexes.

This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 

870.4300; OECD 453) for a combined chronic toxicity/carcinogenicity study in rats.

870.4200b Carcinogenicity (feeding) – Mouse

In a carcinogenicity study (MRID 47746849), isopyrazam (96.4% a.i.; Batch No. SMU6AP001) 

was administered in the diet to C57BL/10JfCD-1 mice (50/sex/dose) for up to 80 weeks at doses 

of 0, 70, 500, or 3500 ppm (equivalent to 0/0, 7.8/9.9, 56.2/74.9, and 432.6/553.6 mg/kg bw/day

in males/females).

No adverse, treatment-related effect was noted on mortality, food consumption, or leukocyte or 

leukocyte differential counts.

In the 3500 ppm males, the incidence of discharge from eye was increased (326 observations in 

36 animals) compared to controls (36 observations in 5 animals). This finding was first noted in 

the control group during Week 24 and in the treated groups during Week 48. At necropsy, the 

incidence of eye discharge was increased (26/50 treated vs 2/50 controls). At the terminal 

sacrifice including decedents, increased (p<=0.05) incidences were noted in minimal to moderate 

inflammation/exudates from the nasolacrimal duct (38/50 treated vs 6/50 controls).

At 3500 ppm, decreased (p<=0.05) body weights were observed throughout treatment in males 

(decr 2-23%) and from Week 4 until termination in females (decr 1-11%). Body weight gains 

during the first 13 weeks were decreased in males by 18% and in females by 11%. Overall 

(Weeks 1-81) body weight gains were decreased by 42% in the males and by 22% in the females. 

At 3500 ppm, food utilization was decreased (p<=0.05) by 16-26% in males during Weeks 1-4 
Page 56 of 67

and 5-8, and was decreased (p<=0.05) by 14-22% in the 500 and 3500 ppm females during 

Weeks 1-4. Food utilization for Weeks 1-12 was decreased (p<=0.01) by 17-21% in both sexes. 

At the terminal sacrifice including decedents, increased (p<=0.05) incidences were noted in the 

following findings (# affected/# examined in treated vs controls) in the 3500 ppm females: 

minimal to slight eosinophilic droplets in the epithelium of the nasal cavity/pharynx (36/50 vs 

21/50); and minimal to moderate eosinophilic droplets in the epithelium in the gall bladder 

(25/50 vs 14/48). 

After 80 weeks of treatment, terminal body weights were statistically similar to controls. 

Increased (p<=0.05) adjusted (for body weight) liver weights were noted in the 3500 ppm males 

(incr 24%) and 500 and 3500 ppm females (13-38%). Increased (p<=0.05) absolute liver 

weights were noted in the 500 and 3500 ppm females (incr 11-30%). At the terminal sacrifice 

including decedents, increased (p<=0.05) incidences were noted in the following findings in the 

liver (# affected/50 in treated vs controls): minimal to slight mid-zonal hepatocellular 

hypertrophy in the 3500 ppm males (40 vs 0); and minimal to moderate periportal hepatocellular 

hypertrophy in the 500 and 3500 ppm females (13-47 vs 0). Increased liver weight and 

hypertrophy in the absence of any other effect on the liver is not considered adverse.

The LOAEL is 3500 ppm (equivalent to 433/554 mg/kg/day in males/females) based on eye 

discharge in males; decreased body weights, body weight gains, and food utilization in both 

sexes; and eosinophilic droplets in the nasal cavity and gall bladder in females. The 

NOAEL is 500 ppm (equivalent to 56/75 mg/kg/day in males/females).

At the doses tested, there was not a treatment-related increase in tumor incidence when 

compared to controls. Dosing was considered adequate based on eye discharge in males; 

decreased body weights, body weight gains, and food utilization in both sexes; and eosinophilic 

droplets in the nasal cavity and gall bladder in females.

This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 

870.4200b; OECD 451) for a carcinogenicity study in mice.

A.4.6 Mutagenicity

Gene Mutation

Guideline #870.5300, In vitro 

mammalian cell gene mutation test

MRID 477468-52,-53, -54, -55, -

Acceptable Guideline

Dose range 0.25 -5000 μg/plate There was no evidence of induced reverse 

mutations with or without activation.

[Negative]
Page 57 of 67

Cytogenetics

Guideline # 870.5375, 

In vitro mammalian chromosome 

aberration test

MRID 477468-57,-,58, -59, -

Acceptable Guideline

Guideline #870.5395

Mammalian erythrocyte micronucleus 

test

MRID 477468-60, -61, -62, -63, -64

Acceptable Guideline

Dose range 0.63 -1760 μg/mL There was no evidence of induced forward 

gene mutations with or without activation.

Dose range 0.63 -1760 μg/mL There was no evidence of chromosomal 

aberrations with or without activation.

[Negative]

A.4.7 Neurotoxicity

870.6100 Delayed Neurotoxicity Study – Hen - NA

870.6200 Acute Neurotoxicity Screening Battery

Study IIA 5.7.1/01 Acute Oral (Gavage) Neurotoxicity Study in Rats (MRID 47746866)

Study Acceptable

Methods

HanRcc:WIST strain rats, 7 weeks old, were randomly assigned to the test groups as shown in 

the following table:

Study design

Group Dose level of Isopyrazam (mg/kg)

Number of animals

Males Females

1 0 10 10

2 30 10 10

3 250 10 10

4 2000 10 10

The animals received a single gavage dose of Isopyrazam in aqueous 0.5% CMC and were 

observed for 16 days. Analysis of the dosing formulations showed that the achieved 

concentrations, homogeneity and stability were satisfactory

General cageside observations were made in all animals prior to study start and at approximately 

1 hour after dose administration on day 1, and once daily thereafter throughout the study. In 

addition, detailed clinical observations comprising open field evaluation of clinical signs were 

performed in a randomized order once prior to study start and on days 8 and 15. On day 1 these 

detailed observations were included in the FOB evaluation. A FOB, including quantitative 

assessment of landing foot splay, sensory perception and muscle weakness, was performed in all 
Page 58 of 67

animals in a randomized order once prior to study start, and on days 1 (approximately 2 hours 

after dose administration), 8 and 15. Locomotor activity was assessed over a time period of 30 

minutes after each FOB evaluation. Bodyweights and food consumption were monitored 

throughout the study. At the end of the 16 day observation period, 5 rats/sex/group were 

perfusion-fixed in situ. Fixed brain weight was recorded. Selected nervous system tissues were 

dissected, processed and examined microscopically.

Results

All animals survived the 16 day observation period. 

At 1-hour post-dose cageside observations, decreased activity were noted in a few males and 

females treated at 250 and 2000 mg/kg. Other treatment-related cageside observations noted at 1-

hour post-dose included weak appearance (250 and 2000 mg/kg females) and swaying gait (250 

mg/kg females). 

In the FOB, the only findings that were considered to be possibly treatment related were slightly 

reduced activity and decreased rearing activity observed in a small number of males and females 

at 250 and 2000 mg/kg on day 1 only. The incidence of these findings was low and was not dose 

related. The locomotor activity assessment detected similar differences, reported as reduced total 

distance, total centre time, number of rears among females at 250 and 2000 mg/kg only on day 1. 

There were no other differences detected in the locomotor assessment that were likely to be 

treatment related. There were no effects on body temperature, grip strength or landing foot 

splay. 

There were no effects on the bodyweight or food consumption of males. Female bodyweight 

gain at 250 and 2000 mg/kg was reduced in comparison with controls during the first week of the 

observation period, by 30 and 33% respectively. For females at 2000 mg/kg food consumption 

during the first week of the observation period was reduced. 

Table IIA 6.7-2: Intergroup comparison of female bodyweight gain (g)

Day

Dose Group (mg/kg)

0 (control) 30 250 2000

1-8 21.9 19.7 15.4** 14.6**

8-15 40.4 35.1 35.0 31.7

* Statistically significant difference from control group mean, p<0.05 (Dunnett’s t-test)

** Statistically significant difference from control group mean, p<0.01 (Dunnett’s t-test)

Brain weight was not affected and there were no treatment related macroscopic or microscopic 

findings in the tissues examined.

Conclusion

The only adverse effects of Isopyrazam treatment were transient reductions in activity, 

bodyweight and food consumption, which are likely to be manifestations of general toxicity. 
Page 59 of 67

There was no evidence of specific or irreversible neurotoxicity. Study NOAEL of 30 mg/kg for 

general toxicity is identified (2000 mg/kg for neurotoxicity).

870.6200 Subchronic Neurotoxicity Screening Battery

In a subchronic neurotoxicity study (MRID 47746865), SYN520453 (Isopyrazam; 96.4% a.i., 

Batch # SMU6AP001) was administered in the diet to 12 Wistar rats/sex/group at dose levels of 

0, 300, 1500, or 6000 ppm (equivalent to 0/0, 20/25, 98/114, and 382/468 mg/kg/day [M/F], 

respectively) for at least 90 days. Neurobehavioral assessment (functional observational battery 

[FOB] and motor activity testing) was performed using all rats at pre-dosing and Weeks 2, 5, 9, 

and 13. At study termination, 5 rats/sex/dose were anesthetized and perfused in situ for 

collection of tissues for neuropathological examination. The tissues from the control and 6000 

ppm groups were subjected to histo-pathological evaluation of brain and peripheral nervous 

system tissues. Positive control data were not provided.

No compound-related effects were observed in mortality, clinical signs of toxicity, FOB, 

ophthalmoscopic parameters, gross pathology, brain weights, or neuropathology.

At 6000 ppm, body weights were decreased (p<0.05) by 6-11% throughout the study in the 

females. Cumulative body weight gains were also decreased (p<0.01 or not statistically

significant) by 24-53% in these females throughout the study. Body weight gains were also 

decreased in the males at this dose compared to controls throughout the study; however, they 

only attained statistical significance during Week 1 (decr 14%, p<0.05). These decreases in 

body weight gain corresponded with decreases in food consumption at this dose. In the females, 

food consumption was decreased compared to controls throughout the study and attained 

statistical significance during Weeks 1, 5, and 7 (decr 15-17%). In the males, food consumption 

was decreased (p<0.01) by 25% during Week 1. Additionally, sporadic decreases in food 

consumption compared to controls were noted in this group after Week 1, but did not attain 

statistical significance. 

In the 6000 ppm females, decreases (p<0.05) were noted in total distance traveled (decr 24%) 

and number of rears (decr 34%) during the Week 13 motor activity assessments. Additionally in 

this group, the time spent in center quadrant was decreased by 34% (not statistically significant) 

compared to controls during Week 13. These findings in the 6000 ppm females were not

considered indicative of neurotoxicity because consistent decreases in motor activity were not 

observed between individual intervals, similar findings were not observed in the males, no 

evidence of neurotoxic deficits were noted in clinical signs or during FOB evaluations in either 

sex, and no neuropathological lesions were observed in either sex at this dose.

No compound-related effects were observed at 300 or 1500 ppm in either sex.

The LOAEL is 6000 ppm (equivalent to 382/468 mg/kg/day, M/F) based on decreased body 

weights in (females), food consumption, and body weight gains. The NOAEL is 1500 ppm 

(equivalent to 98/114 mg/kg/day, M/F).
Page 60 of 67

This study is classified as upgradable/guideline and does not satisfy the guideline requirement 

(OPPTS 870.6200b) for a subchronic neurotoxicity study in rats. The study may be upgraded 

pending submission (locating) of acceptable positive control data.

870.6300 Developmental Neurotoxicity Study

- NA -

A.4.8 Metabolism

870.7485 Metabolism - Rat

In a series of related metabolism studies (MRIDs 47746867-47746874), Han Wistar rats were 

dosed orally by gavage using [Pyrazolyl-5-

14C]-SYN520453 in corn oil, radiolabeled in either 

the Syn isomer (≥98.6% radiochemical purity, Batch # BPM-XXXIII-31 or RDR-II-74) or the 

Anti isomer (≥98.4% radiochemical purity, Batch # RDR-II-7). In the main mass 

balance/excretion/ metabolism study, two groups of rats (4 sex/dose) were given a single oral 

dose of [

14C]-SYN520453 (Syn-isomer) at 1 and 75 mg/kg, and radioactivity in the excreta was 

monitored for up to 7 days post-dose. In a biliary excretion study, two groups of bile ductcannulated rats (4/sex/dose) were given a single oral dose of [

14C]-SYN520453 (Syn-isomer) at 1 

and 75 mg/kg. In a second biliary excretion study, four groups of bile duct-cannulated rats 

(4/sex/dose) were given a single oral dose of [

14C]-SYN520453 (Syn- or Anti- isomer) at 2 and 

75 mg/kg. In a tissue distribution study, two groups of rats (15/sex/dose group) were given a 

single oral dose of [

14C]-SYN520453 (Syn-isomer) at 1 and 75 mg/kg, and 3 rats/sex/interval 

were sacrificed from 6 to 96 hours post-dose to examine the elimination of radioactivity from 

tissues. In another tissue distribution study, 30 male rats (3/sampling interval) were dosed orally 

with [

14C]-SYN520453 (Syn-isomer) at 1 mg/kg for 14 consecutive days, and radioactivity in 

tissues was determined at intervals from 3 to 57 days (43 days post-dose). In a blood kinetics 

study, two groups of rats (9/sex/dose) were given a single oral dose of [

14C]-SYN520453 (Synisomer) at 1 and 75 mg/kg, and radioactivity in whole blood and plasma were monitored from 

0.25 to 48 hours post-dose.

Following a single oral dose of [14C]-SYN520453 at 1 or 75 mg/kg, radioactivity was rapidly 

absorbed and excreted by male and female rats. The majority of the administered radioactivity

(92.3-104.6% of the administered dose, AD) was excreted within 48 hours of dosing, and 95.6-

106.3% of the AD was recovered in the excreta by 7 days post-dose. Radioactive residues in the 

majority of tissues were below the limit of detection (<LOD) by 7 days post-dose, with the 

exceptions of the G.I. tract, liver and kidney. The routes and rates of excretion were generally 

similar for males and females, with feces (77.3-83.0% AD) being the major route of elimination 

at both dose levels. Urinary excretion was slightly higher for females (17.5-27.1% AD) than for 

males (13.3-19.6%) and was also slightly higher in the low-dose group (19.6-27.1% AD) 

compared to the high dose group (13.3-17.5% AD). Data from a preliminary study also 

indicated that radioactivity was not recovered in exhaled air as either CO2 or volatile organics.
Page 61 of 67

At both dose levels, the maximum concentration of radioactivity in the plasma (Cmax) and 

whole blood of male and female rats was attained within 3-6 hours post-dose. Based on the area 

under the concentration curve (AUC(0-t)) for plasma, the systemic exposure of females to 

radioactivity was 1.26-2.54x higher than for males at both dose levels, and the systemic exposure 

of both sexes increased proportionally from 1 to 75 mg/kg. Radioactivity in plasma and whole 

blood declined with a mean terminal elimination half-life (T1⁄2el) of 4.6-8.7 hours.

Treatment of bile duct cannulated rats with a single oral dose of [14C]-SYN520453 at 1 or 75 

mg/kg showed a similar pattern of excretion to non-cannulated rats and indicated that 

enterohepatic circulation played a major role in the excretion of [14C]-SYN520453. Within 48 

hours of dosing, 91.0-102.5% of the AD was recovered in the excreta of bile duct cannulated 

rats, with the majority of the dose being recovered in the bile (47.8-57.9% AD). Feces accounted 

for 21.2-35.7% of the AD, and the levels of radioactivity in urine (7.3-15.9% AD) were similar 

for cannulated and non-cannulated rats. Based on the amount of radioactivity recovered in the 

urine, bile and carcass, rats absorbed 63.1-72.9% of the AD within 48 hours of dosing, with most 

of the dose being absorbed within the first 24 hours (58.8-71.6% AD). The absorption and 

elimination of radioactivity were similar between sexes and the two dose levels.

Similar results were obtained from the bile duct cannulated rats dosed once orally with either the 

14C-Syn or 14C-Anti isomers of SYN520453 at 2 and 75 mg/kg. For each isomer at both dose 

levels, 49-77% of the AD was absorbed, and elimination of the dosed radioactivity was rapid and 

almost complete within 24 hours of dosing. For both isomers, the residual carcasses and G.I. 

tract (with contents) accounted for ≤0.3 and ≤0.1% of the AD, respectively, by 72 hours postdose. Irrespective of dose level or sex, the absorbed dose was eliminated primarily via the bile. 

For rats dosed with the 14C-Anti isomer, 36.5-61.1% of the AD was recovered in the bile, 20.4-

38.3% of the AD was recovered in the feces, and 12.2-22.1% of the AD was recovered in the 

urine. For rats dosed with the 14C-Syn isomer, 41.6-58.0% of the AD was recovered in the bile, 

19.8-48.3% of the AD was recovered in the feces, and 7.0-26.0% of the AD was recovered in the 

urine.

The pattern of excretion was also similar following repeated dosing. For male rats dosed orally 

once a day for 14 consecutive days, the pattern of excretion following the 1st dose was similar to 

the pattern of excretion following the 14th dose. In the 24 hours following dosing on Day 1, the 

urine and feces accounted for 19.7 and 47.9% of the daily AD, respectively. In the 24 hours 

following dosing on Day 14, the urine and feces accounted for 21.6 and 88.6% of the daily AD, 

respectively.

In the tissue distribution time-course study, radioactivity was widely distributed in the tissues 

following a single oral dose at 1 mg/kg. Peak concentrations of radioactivity in tissues were 

observed at the first sampling time (6 hours post-dose), with concentrations being the highest in 

liver, kidney and adrenals of males and in liver, kidneys, fat and adrenals of females. Higher 

levels of radioactivity were detected in the tissues of female rats at 6 hours post-dose than in 

tissues of male rats at the same time point, indicating faster absorption and distribution in female 

rats. After 6 hours post-dose, concentrations in all tissues declined, with similar or lower levels 
Page 62 of 67

of radioactivity observed in the tissues of females compared with the males at the respective time

points. The T1⁄2el in the majority of tissues ranged from 3 to 87 hours, and low levels of 

radioactivity were detectable in most tissues tested by 96 hours post-dose. Residual radioactivity 

in tissues and carcass of male and female rats at 96 hours post-dose accounted for a mean of 

0.76% and 0.62% of the AD, respectively.

Following a single oral dose at 75 mg/kg, the distribution of radioactivity in tissues and organs 

was generally similar to the relative distribution observed for the low-dose rats. Peak tissue 

concentrations were attained at the first sampling time (10 hours post-dose), and concentrations 

in all tissues declined thereafter. At the 10-hour sampling interval, concentrations were highest 

in the liver, kidney and adrenals of males and in the liver, kidneys, fat, adrenals, pancreas, 

ovaries and uterus of females. The higher concentrations of radioactivity in the tissues and 

organs of the high dose group were generally proportional to the increase in the dose rate. The 

elimination half lives in the majority of tissues were in the range of 3 to 49 hours. By 96 hours 

post-dose, residual radioactivity present in tissues and carcass of males and females averaged 

0.61 and 0.24% of the AD, respectively. As at the low dose, residues in tissues of the females 

were initially higher than in the males, but the levels for females were generally similar or lower 

than for the males by 48 hours post-dose. 

Following repeated oral dosing of male rats with [

14C]-SYN520453 at 1 mg/kg/day for 14 days, 

the highest concentrations of radioactivity were observed in the liver, kidneys and blood (0.361, 

0.121 and 0.033 μg equiv./g, respectively) on Days 10-14. Steady state concentrations of 

radioactivity in most tissues were reached by Day 10, with the exceptions of liver and renal fat

(Day 14). Mean concentrations of radioactivity in tissues declined rapidly following cessation of 

dosing on Day 14. Concentrations of radioactivity were quantifiable in only liver (0.049 μg 

equiv./g) and kidney (0.020 μg equiv./g) by 14 days post-dose (Day 28); and radioactivity was 

detectable only in kidneys (0.011 μg equiv./g) and spleen (0.007 μg equiv./g) by 43 days postdose (Day 57). 

Radioactive residues in excreta were adequately identified/characterized. Following a single oral 

dose of [14C]SYN520453 at 1 or 75 mg/kg, 79.1-95.4% of the AD was identified in excreta from 

normal rats and bile duct cannulated rats; and following repeated dosing of male rats at 1 mg/kg, 

74.8-79.4% of the radioactivity was identified in excreta collected from 0-24 hours after the 1st

and 14th doses. In all dose groups, [

14C]SYN520453 was extensively metabolized by rats via 

oxidation of the isopropyl and bicycle moieties giving rise to a range of hydroxy, dihydroxy, acid 

and hydroxy acid metabolites, along with their glucuronide and sulfate conjugates. Oxidation of 

the demethylated metabolite of SYN520453 produced an equivalent range of oxidized 

demethylated metabolites. No cleavage of the parent molecule was observed. The major routes 

of biotransformation were generally independent of dose level and sex, and were similar for the 

Syn and Anti isomers. Metabolism of the Syn isomer also appeared to be similar following 

either a single dose or repeated dosing. The proposed biotransformation pathways of 

SYN520453 are presented in Appendix I.
Page 63 of 67

This metabolism study in the rat is classified acceptable/guideline and satisfies the guideline 

requirement for a metabolism study [OPPTS 870.7485, OPP §85-1] in rats. 

870.7600 Dermal Absorption – Rat - NA
Page 64 of 67

A.4.9 Immunotoxicity

870.7800 Immunotoxicity - Mouse

In an immunotoxicity study (MRID 48347201) Isopyrazam (96.4% a.i., lot # SMU6AP001) was 

fed ad libitum to 10 CD-1 female mice/dose group at levels of 0, 500, 2500, or 5000 ppm (0, 

127, 608, and, 1356 mg/kg bw/day) for 28 days. A group of 10 female CD-1 mice were 

administered the positive control substance, cyclophosphamide (CPS), via intraperitoneal 

injection (50 mg/kg/day) for 4 consecutive days (study days 24 through 27). All animals were 

observed twice daily for mortality and moribundity. Clinical examinations were performed once 

daily. Detailed physical examinations were performed once weekly and on the day of the 

scheduled necropsy. Body weights were recorded twice weekly and food consumption was 

recorded approximately weekly. The liver, spleen, and thymus were collected from all animals 

and weighed at the scheduled necropsy. Spleen cell counts were performed, and the number of 

specific IgM antibody-forming cells directed toward the sRBC was determined.

There were no treatment-related deaths. There were no isopyrazam-related effects on clinical 

observations or macroscopic findings. There were no Isopyrazam-related effects on absolute, 

adjusted, or relative spleen or thymus weights. There were no effects attributed to Isopyrazam on 

the specific activity or total activity of splenic IgM antibody-forming cells to the T celldependent antigen sRBC. A transient body weight loss was noted at 5000 ppm. Higher mean 

absolute and adjusted liver weights noted at 2500 and 5000 ppm Isopyrazam when compared to 

the vehicle control group were consistent with previous studies assessing Isopyrazam at similar 

exposure levels. There were no compound related effects in mortality, clinical signs, body 

weight, food consumption, hematology, clinical chemistry, organ weights, gross pathology, 

histopathology, or immunotoxicity. The NOAEL for immunotoxicity is 5000 ppm (1356 

mg/kg) the highest dose tested. The LOAEL for immunotoxicity was not identified. The 

study NOAEL is 500 ppm (127 mg/kg/day) based on transient body weight loss and high 

liver weights at 2500 and 5000 ppm (608 and 1356 mg/kg/day).

The toxicology database for Isopyrazam does not show any evidence of treatment-related effects 

on the immune system. The overall weight of evidence suggests that this chemical does not 

directly target the immune system. 

This immunotoxicity study on Isopyrazam is classified as acceptable/guideline and satisfies the 

guideline requirement for an immunotoxicity study (OPPTS 870.7800) in mice. 
Page 65 of 67

Appendix B. Metabolism

Figure 1: Proposed metabolic pathway of isopyrazam in plants

N

N

F

F

O

N

H

N

N

F

F

O

N

H

N

N

H

F

F

O

N

H

N

N

H

F

F

O

N

H

N

N

F

F

O

N

H

HO

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

N

N

F

F

O

N

H

OH

OH

N

N

F

F

O

N

H

HO

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

HO

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

OH

OH

N

N

F

F

O

N

H

N

N

F

F

O

OH

N

N

H

F

F

O

OH

CSCD120604*

 (w, l)

CSCD120605*

 (w)

CSCD539372

 (w, g, l)

CSCD539391

 (w, g)

CSCC230729

 (w, l**)

SYN534969 SYN534968

CSCD459488*

 (w, g, l)

CSCD459489*

 (g)

CSCD656800*

 (g)

CSCD465008*

 (g, l)

CSAA798670*

 (w, g, l)

CSCD563692*

 (w, g, l)

CSCD610195*

 (g, l)

CSCD573363*

 (l)

SYN520453

CSCD563691*

 (w)

(w, l)

w - Wheat

g - Grape

l - Lettuce

* - indicates metabolites mainly 

 present in conjugated forms

** - CSCC230729 is considered 

 to be an artifact produced 

 under acid hydrolysis conditions

 in the lettuce

comprised of

(w, g, l)
Page 66 of 67

Figure 2. Proposed metabolic pathway of isopyrazam in livestock animals.

N

N

F

F

O

N

H

N

N

F

F

O

N

H

N

N

F

F

O

N

H

OH O

N

N

F

F

O

N

H

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

HO O

N

N

F

F

O

N

H

HO O

N

N

F

F

O

N

H

HO

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

OH

OH

N

N

H

F

F

O

N

H

OH O

N

N

F

F

O

N

H

OH O

OH

N

N

H

F

F

O

N

H

OH O

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

OH

OH

OH

N

N

F

F

O

N

H

HO

OH

OH

N

N

F

F

O

N

H

OH

N

N

F

F

O

N

H

OH

OH

N

N

H

F

F

O

N

H

OH

OH

N

N

F

F

O

N

H

O OH

CSCD662024 g(u), r

 

SYN534969 SYN534968

CSCD656800 g, h, r

 

CSCD563692 g, r

SYN520453

comprised

of

CSCD676318 g(u), r

 

Hydroxy carboxylic acid g(u), r

 

CSCD658108 g CSCD658109 g

CSCD591489 g, r CSCD626401 g, r

N-Demethylated hydroxy carboxylic acid g(u), r

 

 

CSCD610195 g, r CSCD610196 g, r

- H2 

i.e. unsaturation in

isopropyl or bicyclo

moiety at position 

a, b or c

Trihydroxy g(u), h(e), r

 

CSCD459488 CSCD459489

 (proposed intermediates)

Unsaturated carboxylic acid h

- H2O

Hydroxy CSCD459489 h

N-Demethylated dihydroxy h(e), r

Note:- Unspecified hydroxylation positions, as indicated by brackets, are restricted to the isopropyl and bicyclo ring moieties

There is evidence for conjugation of hydroxyl groups with sulphate and glucuronic acid 

g - goat, h - hen, r - rat g(u) - found only in goat urine, not tissues or milk h(e) - found only in hen excreta, not tissues or eggs

b a

c

g, h(e), r
Page 67 of 67

Appendix C. Physical/Chemical Properties

Table C.1 Physicochemical Properties of Isopyrazam. 

Parameter Value Reference

Melting point/range 144.5oC for SYN534968;130.2oC 

for SYN534969

MRID 47746809

pH 6.1 @22oC (1% aqueous solution)

Density 1.332 g/cm3 (1.332 x 103 kg/m3) 

(typical) at 19.5 oC

Water solubility (pure water) SYN534968: 0.55 mg/L @25oC

SYN534969: 1.05 mg/L @25oC

Solvent solubility (g/L) Acetone: 314; 

dichloromethane:330; ethyl acetate 

179; n-hexane 1.17; methanol 119

n-octanol 44.1; toluene 77.1

Vapor pressure SYN534968 and SYN534969: 

5.7x10-8 Pa @25oC 

Dissociation constant, pKa No pKa observed in the pH range 

of 1.0 – 12.0 by spectrophotometric 

titrations of both SYN534968 and 

SYN534969

Octanol/water partition 

coefficient

Log Pow = 4.4 for SYN534968 and 

4.1 for SYN534969 @25oC

UV/visible absorption spectrum SYN534969: 17,576 l/mol*cm 

(neutral solution); 17,439 l/mol*cm 

(acidic solution); 17,328 l/mol*cm 

( basic solution)

Appendix D. Review of Human Research

No studies were used for this assessment.