EPA REGISTRATION DIVISION COMPANY NOTICE OF FILING FOR 

PESTICIDE PETITIONS PUBLISHED IN THE FEDERAL REGISTER 

EPA Registration Division contact: Marcel Howard, PM Team 20, 703-305-6784

Syngenta Crop Protection, Inc.

2E8039

EPA has received a pesticide petition from Syngenta Crop Protection, Inc, 410 

Swing Road, P.O. Box 18300, Greensboro, NC 27419-8300 proposing, pursuant to 

section 408(d) of the Federal Food, Drug, and Cosmetic Act (FFDCA), 21 U.S.C. 

346a(d), to amend 40 CFR part 180.

1. by establishing a tolerance for residues of

Isopyrazam (SYN520453) in or on the raw agricultural commodity apple at 0.6

parts per million (ppm) and peanuts at 0.01 ppm. EPA has determined that the petition 

contains data or information regarding the elements set forth in section 408 (d)(2) of 

FDDCA; however, EPA has not fully evaluated the sufficiency of the submitted data at 

this time or whether the data supports granting of the petition. Additional data may be 

needed before EPA rules on the petition.

A. Residue Chemistry

1. Plant metabolism. Metabolism of SYN520453 has been studied on wheat, 

grapes, and lettuce. The metabolic routes of SYN520453 in all three crops were the same 

and the parent molecule was the primary constituent of the Total Radioactive Residue 

(TRR) in all three matrices. The most significant metabolite identified in plant was the 

primary alcohol, the metabolites CSCD459488 and CSCD459489 (syn and anti forms 

respectively). 

Based on the results of the metabolism studies conducted, EPA concluded that the 

definition of the residue for tolerance enforcement purposes is parent isopyrazam only

(SYN534968 plus SYN534969); however the residue-of-concern for risk assessment 

purposes includes parent isopyrazam (SYN534968 plus SYN534969) plus the metabolite 

CSCD459488. The residue trials conducted included measurements of the two isomers 

of the parent, the metabolite CSCD459488, as well as the anti version of the latter, 

CSCD459489.

2. Analytical method. An adequate, validated method (GRM006.01B) is available 

for enforcement purposes for the determination of residues of isopyrazam, analyzed as 
2

the isomers SYN534968 and SYN534969, in crop samples. The limit of quantification 

has been set at 0.005 mg/kg for each isomer (0.01mg/kg for SYN520453 in total). 

Samples are extracted by homogenization with acetonitrile:water (80:20 v/v for most 

crops and 50:50 v/v for straw). Extracts are centrifuged and aliquots (equivalent to 0.2 g) 

are diluted with methanol:water (50:50 v/v). Final determination is by LC-MS/MS. An 

analytical method suitable for the determination of residues of the metabolites 

CSCD459488 and CSCD459489 (syn and anti forms respectively) in crop samples using 

an external standardization procedure is also available. The limit of quantification (LOQ) 

has been set at 0.005 mg/kg for both analytes. Samples are extracted by homogenization 

with acetonitrile:water (80:20 v/v). Extracts are centrifuged and aliquots (equivalent to 

0.09 g) are hydrolyzed with 0.1 M HCl at 60°C for 3 hours. Aliquots are then diluted 

with acetonitrile and ultra pure water. Final determination is by LC-MS/MS.

3. Magnitude of residues.

Apple-Nine field residue trials were conducted in Chile to determine the magnitude of the 

residue of isopyrazam (SYN520453) in or on apples resulting from three late-season 

foliar applications of a suspension concentrate (SC) formulation containing 100 g a.i./L 

isopyrazam (A16524Y), beginning at 28 days prior to harvest and repeated at 7-day

intervals, and ending at 14 or 21 days prior to harvest.

Apple samples were analyzed for residues of parent SYN520453 analyzed as 

SYN534968 (anti) and SYN534969 (syn, and for residues of its metabolite analyzed as 

CSCD459489 (anti) and CSCD459488 (syn). The limit of quantification for each analyte 

was 0.005 ppm. Mean procedural recoveries of all analytes on all matrices were between 

the acceptable range of 70-110%. 

The maximum residue levels of SYN520453 (summed SYN534968 and SYN534969) in 

apples were 0.34 ppm and 0.25 ppm at 14 day after last application (14DALA) and 21 

day after last application (21DALA), respectively. The highest residue levels of 

CSCD459488 detected was below 0.005 ppm, the limit of quantification (LOQ).

Peanuts- Four residue trials were conducted in Nicaragua to determine the magnitude of 

the residue of isopyrazam (SYN520453) in or on peanuts resulting from three late-season 

foliar applications of a emulsifier concentrate (EC) formulation containing 125 g a.i./L 

isopyrazam (A15149C), at the nominal rate of 125 g ai/ha, beginning at 35 days prior to 

harvest, repeated at 14-day intervals, and ending at 7 days prior to harvest (harvest 

defined as the date the peanuts were inverted to begin the field drying process). 

Peanut samples were analyzed for residues of parent SYN520453 analyzed as 

SYN534968 (anti) and SYN534969 (syn), and for residues of its metabolite analyzed as 

CSCD459489 (anti) and CSCD459488 (syn). The limit of quantification for each analyte 

was 0.005 ppm. Mean procedural recoveries of all analytes on all matrices were between 

the acceptable range of 70-110%. 

No residues of SYN520453 or any of its metabolites (CSCD459489 or CSCD459488) 

were detected at levels above LOQ (0.005 ppm) at any sampling events (0, 3, 7, 10 and 
3

14 DALA) in any of the four field trials.

B. Toxicological Profile

1. Acute toxicity. SYN520453 is of low acute toxicity by the oral, dermal and 

inhalation routes of exposure and is not irritating to the eyes or skin. On the basis of the 

results of a local lymph node assay in the mouse, SYN520453 is considered to have 

potential to cause sensitization following contact with skin. Three acute oral studies 

focused on the isomeric proportions of SYN520453. The LD50 for isomeric mixtures 

containing more than 50% of the syn isomer of isopyrazam was >2000 mg/kg.]

2. Genotoxicty. [In vitro, both specifications of SYN520453 (Tox Reserve and 

70:30) were negative for bacterial reverse mutation, in vitro cytogenetics, and 

mammalian cells gene mutation (L5178Y TK+/- mouse lymphoma). The L5178 TK+/-

assay, which is also able to detect chromosomal damage, was negative for clastogenicity. 

In the in vitro cytogenetic assay using primary human lymphocyte cultures, neither 

specification of SYN520453 induced chromosomal aberrations. In vivo, SYN520453 

(Tox Reserve specification) was found to be non-clastogenic in the rat bone marrow 

micronucleus assay and there was also no evidence for any indication of DNA damage or 

repair in the rat liver UDS (unscheduled DNA synthesis) assay.]

3. Reproductive and developmental toxicity. SYN520453 was assessed for 

reproductive toxicity in a multi-generation reproduction study in the rat at dietary

inclusion levels of 0, 100, 500 or 3000 ppm SYN520453. The parental toxicity NOAEL 

was 100 ppm based on decreased body weight and food consumption in females at 500 

ppm; and increased liver weight and hepatocyte hypertrophy in F0 and F1 animals at 500 

ppm. The offspring NOAEL was 100 ppm based on increased liver weights in F1 and F2 

pups at 500 ppm. No treatment related reproductive parameters were affected due to 

treatment with SYN520453 thus the reproductive NOAEL was the top dose 3000 ppm 

and a LOAEL was not established. There is no indication of increased sensitivity of 

offspring to SYN520453 in a multi-generation reproduction study in rats.

Two developmental toxicity studies were conducted in the rat: one with Tox Reserve 

material and the other with 70:30 material. In the study with Tox Reserve, rats were 

given oral doses of SYN520453 at 0, 20, 75 or 250 mg/kg/day on gestation days 5 to 21. 

The maternal NOAEL was 75 mg/kg/day based on mortality, decreased body weight gain 

and food consumption and clinical signs of toxicity at 250 mg/kg/day. The fetal NOAEL 

was 75 mg/kg/day based on increased post-implantation loss, a reduced number of live 

fetuses, decreased fetal weight and reduced ossification at 250 mg/kg/day. The fetal 

effects were considered to be secondary to maternal toxicity.

In the rat developmental toxicity study with 70:30 material, rats were given oral doses of 

SYN520453 at 0, 20, 75 or 200 mg/kg/day. The fetal and maternal NOAEL was 20 

mg/kg/day based on decreased fetal body weight and delayed ossification; and decreases 

in maternal body weight gain at 75 and 200 mg/kg/day. The fetal effects were considered 

to be secondary to maternal toxicity.
4

In rabbits, two preliminary developmental toxicity studies were conducted in the 

Himalayan rabbit and a preliminary and regulatory study were conducted in the New 

Zealand White (NZW) rabbit. All studies were conducted using the Tox Reserve 

material. 

In the first preliminary study, Himalayan rabbits were given oral doses of 0, 100, 200 or 

400 mg/kg/day. Mean maternal food consumption was decreased throughout treatment at 

400 mg/kg/day. The only fetal effect possibly related to treatment was the observation of 

2 fetuses at 400 mg/kg/day with the variation of “eyes small, slight” 

In the second preliminary study, Himalayan rabbits were given oral doses of 0, 600, 800 

or 1000 mg/kg/day. Maternal food consumption was slightly decreased at 1000 

mg/kg/day. There was a small effect on male fetal body weights and a higher incidence 

of flexed or malrotated limbs at 1000 mg/kg/day. The main treatment related fetal 

finding was the observation, eyes of smaller than expected size, which occurred either as 

an abnormality or variation. The combined incidence of small eyes (abnormality and 

variation) was increased in all dose groups, but not in a dose-related manner. It was 

concluded that administration of SYN520453 at 600-1000 mg/kg/day was associated with 

effects in the eye consistent with microphthalmia. 

A preliminary rabbit developmental toxicity study was conducted in NZW rabbits at 

doses of 0, 400, 700 or 1000 mg/kg/day. Maternal toxicity was noted at all dose levels 

tested, evident as decreased food consumption and decreased maternal weight gain 

throughout the treatment period. The effects were sufficient to produce moribundity

and/or abortion in animals from each dose group. Maternal liver weight was increased at 

all doses and hypertrophy and vacuolation were observed histopathologically. At 1000 

mg/kg/day, there was an increase in the incidence of microphthalmia which was 

associated with the variations hemorrhagic ring around the iris and/or reddened or red 

areas around the eyes. 

In the regulatory developmental toxicity study, NZW rabbits were dosed at 0, 30, 150 or 

500 mg/kg/day. The maternal NOAEL was 30 mg/kg/day based on clinical signs of 

toxicity (days 13-19), decreased food consumption, increased liver weights and 

hepatocellular hypertrophy and vacuolation at 150 and 500 mg/kg/day. The fetal 

NOAEL was 150 mg/kg/day based only on the single incidence of microphthalmia 

observed at 500 mg/kg/day. The single incidence of microphthalmia at 500 mg/kg/day

was within the historical control range for the laboratory. However, based on the data 

from the NZW range-finding study, which was conducted in the same laboratory, an 

association between treatment and the single incidence of microphthalmia at 500 

mg/kg/day cannot be excluded.

4. Subchronic toxicity. Subchronic testing was conducted in the mouse, rat, and 

dog via the oral route of exposure, including evaluation of the effect of isomer content of 

SYN520453. Three 28-day studies conducted in rats showed similar findings and 

confirmed the liver was the systemic target organ for SYN520453. Liver effects were 
5

evident at doses of 500 ppm and above with no liver effects observed at 300 ppm 

(approximately 28.1 mg/kg/day). The only other evidence of systemic toxicity was the 

observed decrease in body weight gain compared to controls which tended to occur at 

dose levels of 2000 ppm and above; observed in conjunction with decreased food 

utilization. The study conducted with pure syn and anti-isomers demonstrated equivalent

toxicological properties from both a qualitative and quantitative perspective.

Two 90-day dietary studies in rats demonstrated similar toxicological findings to the 28-

day studies. The NOAELs from the two 90-day studies were similar; a NOAEL of 

300 ppm (21.3 mg/kg/day) in the Tox Reserve study, and a NOAEL of 250 ppm for both 

Tox Reserve and 70:30 specification materials in the comparative study; based on 

decreased body weight/weight gain, clinical chemistry changes, increased liver weight,

and hepatocellular hypertrophy and vacuolation at 1500 and 2000 ppm respectively.

The 90-day dietary study in mice was conducted with Tox Reserve material at 0, 500, 

2500 or 7000 ppm. The systemic toxicity findings in this study were decreased body

weight/weight gain observed at 2500 & 7000 ppm. Increased liver weight was seen at all 

dose levels and hepatocyte hypertrophy was seen in both sexes at 2500 and 7000 ppm. 

Minimal hypertrophy was seen in males at 500 ppm.

Two 90-day oral toxicity studies were conducted in dogs; one was conducted using Tox 

Reserve and the other with 70:30 material. In the first 90-day study with Tox Reserve 

material, dogs were dosed orally at 0, 30, 100 or 300 mg/kg/day. In the second 90-day

study with 70:30 material, dogs were dosed orally at 0, 10, 30 or 250 mg/kg/day. The 

findings were similar, an overall NOAEL of 30 mg/kg/day was based initial body weight 

loss and/or decreased weight gain and decreased food consumption; and increased liver 

weights (males only) at 100 and 250 mg/kg/day. One male dog at the mid-dose of 100 

mg/kg/day also displayed abnormal clinical signs/behavior, some of which were evident 

throughout the study.

5. Chronic toxicity. SYN520453 was evaluated for chronic toxicity in the dog and 

rat, and for carcinogenic potential in the rat and the mouse. 

In the 1 year dog study with Tox Reserve, dogs were dosed orally by capsule at 0, 25, 

100 or 250 mg/kg/day. The NOAEL was 25 mg/kg/day based on decreased body weight 

gain and minor changes in clinical chemistry, and increased liver weight (males only) at 

100 and 250 mg/kg/day. No clinical signs of toxicity were observed in the 1 year dog 

study up to a dose level of 250 mg/kg/day.

In a 2 year rat combined chronic toxicity/carcinogenicity study conducted at dietary

inclusion levels of 0, 100, 500 or 3000 ppm, there were no treatment related effects on 

survival. The NOAEL for the chronic toxicity phase of the study was 100 ppm and the

NOAEL for neoplastic findings was 500 ppm (27.6 and 34.9 mg/kg/day in males and 

females respectively) based on increased incidence of hepatocellular adenoma and uterine 

carcinoma observed as a consequence of excessive dosing in females at 3000 ppm. The 

overall NOAEL was 100 ppm (5.5 and 6.9 mg/kg/day in males and females respectively) 
6

based on decreased body weight/weight gain in females at 500 ppm; and minor changes 

in clinical chemistry and non-neoplastic findings in the liver at 500.

In a carcinogenicity study in the mouse, mice were fed diets containing 0, 70, 500 or 

3500 ppm SYN520453 for a period of up to 80 weeks. There were no treatment related 

effects on survival. Apart from an increased incidence of ‘discharge from the eye’ in

males at 3500 ppm, there were no effects on the clinical condition of the animals. There 

were no treatment-related neoplastic micropathology findings. The NOAEL for this 

study was 70 ppm (7.8 mg/kg/day in males and 9.9 mg/kg/day in females) based on 

reduced food utilization in females at 500 ppm; and hepatocellular hypertrophy and 

increased liver weight at 500 ppm.

6. Animal metabolism. SYN520453 was extensively metabolized by rats via

oxidation to give a range of hydroxy, dihydroxy, acid and hydroxy acid metabolites. 

Oxidation of the N-desmethyl metabolite of SYN520453 produced an equivalent range of 

N-desmethyl metabolites. Incubation of SYN534969 (pure syn) with rat liver 

microsomes resulted in oxidative biotransformation to the tertiary alcohol CSCD459488; 

quantities decreasing with increased incubation time, demonstrating that the metabolite 

CSCD459488 is a short-liver metabolite. The major routes of biotransformation 

appeared to be independent of dose level and sex and also appeared to be the same for 

both syn and anti isomers of the parent molecule. All metabolites accounting for >5% of 

the dose and the majority of minor metabolites were identified. Therefore in total, greater 

than 90% of the administered dose was accounted for by identified metabolites.

7. Metabolite toxicology. Acute oral toxicity testing was performed with two 

metabolites; resulting in LD50 >2000 mg/kg for both CSCD465008 and CSCD459488. 

Genotoxicity testing (bacterial reverse mutation, in vitro cytogenetics, and mammalian 

cell gene mutation (mouse lymphoma) with metabolites CSCD465008 and CSCD459488 

indicated no genotoxicity. Subchronic toxicity studies (28 day dietary in the rat) were 

conducted with metabolites CSCD465008 and CSCD459488. CSCD465008 is 

toxicologically benign and is of lower toxicity than parent SYN520453. The metabolite 

CSCD459488 is considered to have equivalent toxicity to parent SYN520453 with both 

compounds having a NOAEL of 300 ppm (equivalent to approximately 27-28 

mg/kg/day) and both compounds having a primary effect upon xenobiotic metabolizing 

enzymes in the liver with accompanying liver enlargement and centrilobular hypertrophy.

8. Endocrine disruption. 

The endocrine system includes the reproductive hormones estrogen and androgens as 

well as the thyroid hormone system. There is no evidence of any consistent treatment 

related effects with SYN520453 that could be considered as perturbation of endocrine 

homeostasis. There were no adverse affects related to female reproductive function or on 

reproduction in the multi-generation reproductive toxicity study, and there were no

micropathology changes in the organs that had altered weight effects. Overall, the 

database does not suggest that SYN5204534 is an endocrine disruptor.

C. Aggregate Exposure
7

1. Dietary exposure. Tier I acute and Tier II chronic and chronic cancer dietary exposure 

assessments were performed for isopyrazam (a mixture of 3-(difluoromethyl)-1-methylN-[(1RS,4SR,9RS)-1,2,3,4-tetrahydro-9-isopropyl-1,4-methanonaphthalen-5-yl]pyrazole4-carboxamide (syn-isomer, also called SYN534968) and 3-(difluoromethyl)-1-methylN-[(1RS,4SR,9SR)-1,2,3,4-tetrahydro-9-isopropyl-1,4-methanonaphthalen-5-yl]pyrazole4-carboxamide (anti-isomer, also called SYN534969)) using the Dietary Exposure 

Evaluation Model (DEEM-FCIDTM), version 2.16 from Exponent for a proposed use on 

imported apples and peanuts. The current use for isopyrazam is on imported bananas. 

The definition of the residue for tolerance enforcement purposes is parent isopyrazam 

only (SYN534968 plus SYN534969), however the residue-of-concern for risk assessment 

purposes includes parent isopyrazam (SYN534968 plus SYN534969) plus the metabolite 

CSCD459488. Import tolerances for apples (0.6 ppm) and peanuts (0.01 ppm) were 

proposed using the EPA/PMRA tolerance tool (PRO2008-02, “Guidance for Setting 

Pesticide Maximum Residue Limits Based on Field Trial Data - Revised,” PMRA, April 

4, 2008), based upon residue field trial data on apples and peanuts treated at the 

maximum labeled application rate and harvested at the minimum pre-harvest interval 

(PHI) of 21-days (apples) and 7-days (peanuts). In these risk assessments, the 

EPA/PMRA tolerance tool was used to develop an upper-bound residue-of-concern 

estimate of 0.6 ppm for apples and 0.01(2 x LOQ) ppm for peanuts to account for 

residues of both parent isopyrazam plus the metabolite CSCD459488. Default DEEM 

processing factors were assumed for all processed commodities. A percent of crop 

treated (%CT) value of 6% was used for imported apples and 100% CT was 

conservatively assumed for peanuts. Since the current and proposed uses will not result 

in transfer of residues to livestock via consumption of treated feedstuffs, anticipated 

residues of isopyrazam in meat, milk, or egg commodities were not included in the 

assessments. Additionally, since there are no registered uses for isopyrazam in the 

United States, dietary exposures via drinking water (surface water and/or ground water) 

were also not considered. All consumption data for these assessments were taken from 

the USDA’s Continuing Survey of Food Intake by individuals (CSFII) with the 1994-96 

consumption database and the Supplemental CSFII children’s survey (1998) consumption 

database. 

i. Food Acute Exposure. Acute dietary (food only) risk assessments for parent 

isopyrazam plus metabolite CSCD459488 were performed for all population sub-groups 

using an acute reference dose (aRfD) of 0.30 mg/kg-bw/day, based upon a 90-day study

in dogs with a no observed adverse effect level (NOAEL) of 30 mg/kg-bw/day and an 

uncertainty factor of 100X. The 100X safety factor includes intra- and inter-species 

variations; no additional FQPA safety factor was applied. For the purpose of aggregate 

risk assessment, the exposure values were expressed in terms of margin of exposure 

(MOE), which was calculated by dividing the NOAEL by the exposure for each 

population subgroup. In addition, exposure was expressed as a percent of the acute 

reference dose (%aRfD). At the 95th percentile, acute (food only) exposure to the U.S. 

population resulted in a MOE of 7,202 or 1.4% of the aRfD (Benchmark MOE = 100, 

aRfD = 0.3 mg/kg-bw/day). The most exposed sub-population was all children 1-2 years 

old, with a MOE of 1,044 or 9.6% of the RfD (Benchmark MOE = 100, aRfD = 0.3 
8

mg/kg-bw/day). Since the benchmark MOE for this assessment was 100 and since the 

EPA generally has no concern for exposures above the Benchmark or below 100% of the 

reference dose, Syngenta believes that there is a reasonable certainty that no harm will 

result from dietary (food only) exposure to residues arising from all current and proposed 

uses of isopyrazam.

Chronic Exposure. Chronic dietary (food only) risk assessments for parent isopyrazam 

plus metabolite CSCD459488 were performed for all population sub-groups using a 

chronic reference dose of 0.0.055 mg/kg-bw/day, based upon a 2-year study in rats with a 

no observed adverse effect level (NOAEL) of 5.5 mg/kg-bw/day and an uncertainty 

factor of 100X. The 100X safety factor includes intra- and inter-species variations; no 

additional FQPA safety factor was applied. For the purpose of aggregate risk assessment, 

the exposure values were expressed in terms of margin of exposure (MOE), which was 

calculated by dividing the NOAEL by the exposure for each population subgroup. In 

addition, exposure was expressed as a percent of the chronic reference dose (%cRfD). 

Chronic (food only) exposure to the U.S. population resulted in a MOE of 81,148 or 

0.1% of the cRfD (Benchmark MOE = 100, cRfD = 0.055 mg/kg-bw/day). The most 

exposed sub-population was children 1-2 years old with a MOE of 11,412 or 0.9% of the 

cRfD (Benchmark MOE = 100, cRfD = 0.055 mg/kg-bw/day). Since the benchmark 

MOE for this assessment was 100 and since the EPA generally has no concern for 

exposures above the benchmark or below 100% of the reference dose, Syngenta believes 

that there is a reasonable certainty that no harm will result from dietary (food only) 

exposure to residues arising from all current and proposed uses of isopyrazam.

Cancer. A cancer dietary risk assessment was performed for the U.S. population, with a 

carcinogenic potency factor (Q*) of 0.0063 (mg/kg-bw/day)

-1

, based on the presence of 

thyroid follicular cell tumors in male rats and liver and uterine tumors in female rats at 

doses that were adequate to evaluate the carcinogenic potential of isopyrazam. Cancer 

exposure to isopyrazam results in a risk of 4.28 x 10-7, or approximately 0.4 in one 

million, which is within the safe level of concern set by the EPA of 1.00 x 10-6. 

ii. Drinking water. Since the proposed use on imported apples and peanuts will 

not result in contributions of SYN520453 or its metabolite(s) to surface or ground water 

in the United States, a drinking water exposure assessment was not conducted.

2. Non-dietary exposure. There are no currently registered residential uses for 

SYN520453, so a non-dietary residential exposure assessment was not conducted.

D. Cumulative Effects

Cumulative Exposure to Substances with a Common Mechanism of Toxicity. 

Section 408(b)(2)(D)(v) requires that, when considering whether to establish, modify, or 

revoke a tolerance, the Agency consider “available information” concerning the 

cumulative effects of a particular pesticide’s residues and “other substances that have a 
9

common mechanism of toxicity”. Syngenta did not perform a cumulative risk assessment 

as part of this tolerance action for isopyrazam because HED has not yet determined that 

there are any other chemical substances that have a mechanism of toxicity common with 

that of isopyrazam. 

E. Safety Determination

1. U.S. population. Using the conservative assumptions described above, and 

based on the completeness and reliability of the toxicity data, the acute aggregate (food 

only) exposure calculation for all current and proposed uses of isopyrazam resulted in a 

MOE of 7,202 or 1.4% of the aRfD (Benchmark MOE = 100, aRfD = 0.3 mg/kg-bw/day) 

for the U.S. population. The chronic aggregate (food only) exposure analysis showed 

that exposure from all current and proposed uses of isopyrazam resulted in a MOE of 

81,148 or 0.1% of the cRfD (Benchmark MOE = 100, cRfD = 0.055 mg/kg-bw/day). 

Since the worst case aggregate MOE of 7,202 (acute aggregate exposure) exceeds the 

benchmark MOE of 100, Syngenta believes that there is a reasonable certainty that no 

harm will occur to the U.S. Population from acute and chronic aggregate exposures 

arising from all current and proposed uses of isopyrazam. 

2. Infants and children. Using the conservative assumptions described above, and 

based on the completeness and reliability of the toxicity data, the acute aggregate (food 

only) exposure calculation for all current and proposed uses of isopyrazam resulted in a 

MOE of 1,044 or 9.6% of the aRfD (Benchmark MOE = 100, aRfD = 0.3 mg/kg-bw/day) 

for children 1-2 years old. The chronic aggregate (food only) exposure analysis showed 

that exposure from all current and proposed uses of isopyrazam resulted in a MOE of 

11,412 or 0.9% of the cRfD (Benchmark MOE = 100, cRfD = 0.055 mg/kg-bw/day) for 

children 1-2 years old. Since the worst case aggregate MOE of 1,044 (acute aggregate 

exposure) exceeds the benchmark MOE of 100, Syngenta believes that there is a 

reasonable certainty that no harm will occur to infants and children from acute and 

chronic aggregate exposures arising from all current and proposed uses of isopyrazam. 

3. Aggregate Cancer Risk. The aggregate cancer risk assessment for the U.S. 

population using a carcinogenic potency factor (Q*) of 0.0063 (mg/kg-bw/day)

-1

resulted 

in a cancer risk of 4.28 x 10-7, which is within the 1.0 x 10-6level of concern set by the 

EPA. 

F. International Tolerances

There are no Codex Alimentarius maximum residue levels (MRLs) is established 

for isopyrazam.