EPA REGISTRATION DIVISION COMPANY NOTICE OF FILING FOR 

PESTICIDE PETITIONS PUBLISHED IN THE FEDERAL REGISTER 

EPA Registration Division contact: Shaja Joyner, (703) 308-3194

INSTRUCTIONS: Please utilize this outline in preparing the pesticide petition. In 

cases where the outline element does not apply, please insert “NA-Remove” and 

maintain the outline. Please do not change the margins, font, or format in your 

pesticide petition. Simply replace the instructions that appear in green, i.e., “[insert 

company name],” with the information specific to your action.

TEMPLATE:

ISK Biosciences Corporation

[Insert petition number]

EPA has received a pesticide petition ([insert petition number]) from ISK 

Biosciences Corporation, 7470 Auburn Road, Suite A, Concord, Ohio, 44077,

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 by establishing a tolerance for 

residues of the fungicide pyriofenone, (5-chloro-2-methoxy-4-methyl-3-

pyridinyl)(2,3,4-trimethoxy-6-methylphenyl)methanone, in or on the raw agricultural 

commodity grape at 0.2 parts per million (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. The metabolism of pyriofenone as well as the nature of 

the residues in plants is adequately understood for the purposes of this

tolerance. Metabolism studies were conducted with three diverse crops, 

grapes, wheat and tomatoes. All three crops showed a similar pattern of 

metabolism with unchanged pyriofenone remaining on the plant surfaces. 

The metabolism of pyriofenone in plants results in a large number of 

fragments in only trace amounts. Hence, parent pyriofenone is the only 

residue of concern.

2. Analytical method. A practical analytical method for Pyriofenone using 

Liquid Chromatography-MS/MS is available for analysis of grapes. This 
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method has been confirmed through independent laboratory validation 

and is available for enforcement purposes.

3. Magnitude of residues. Seventeen grape trials were conducted in 

Germany (4 trials), Northern France (4 trials), southern France (4 trials), 

Spain (3 trials) and Italy (2 trials). These studies cover a wide range of 

geographies with diverse climates and growing conditions, as well as 

various cultural practices. The residue values reported gave results 

which lead to a proposed tolerance of 0.20 ppm. 

In four trials, samples were processed into juice, wine and raisins. There 

was no concentration of pyriofenone in grape juice, wine, or raisins.

Residues in raisins seen during processing trials were considered to 

reflect water loss during the drying process used to produce them and are 

as expected.

B. Toxicological Profile

The proposed tolerance for pyriofenone is for an imported commodity only. The 

acute oral toxicity and acute neurotoxicity studies are the only studies required to 

evaluate acute toxicity. Subchronic dermal and inhalation studies are not required 

because residential and occupational risk assessments are not necessary to set a 

tolerance on an imported commodity.

1. Acute toxicity. Pyriofenone exhibits low oral acute toxicity. The oral LD50

is greater than 2000 mg/kg. Since this petition is for an import tolerance, 

oral toxicity data sufficiently assesses the risk of acute exposure for this 

use.

In an acute neurotoxicity study, pyriofenone was administered by oral 

gavage to groups of CD rats at doses up to 2000 mg/kg. The animals were 

observed for 14 days. A single oral administration of pyriofenone at 

doses up to 2000 mg/kg, the maximum dose required by the guidelines to 

which the study was designed, resulted in minimal, transient change and 

there was no evidence of any neurological effect. Consequently, 2000 

mg/kg was considered to be the NOEL.

2. Genotoxicity. The genotoxic potential of pyriofenone has been assessed as 

negative by several in vitro and in vivo mutagenicity studies. Pyriofenone

did not elicit a genotoxic response in any of the studies conducted.

3. Reproductive and developmental toxicity. Results from a two-generation 

study indicate that pyriofenone is not a reproductive toxicant. The 

dietary concentrations for the study were 0, 150, 1000 and 5000 ppm. The 
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NOEL for systemic toxicity was 1000 ppm (equivalent to 64.1 and 79.2 

mg/kg/day, respectively for P males and females and 76.8 and 84.4 

mg/kg/day for F1 males and females). The NOEL for reproductive 

toxicity was 5000 ppm (equivalent to 334 and 395 mg/kg/day for P males 

and females, respectively and 393 and 434 mg/kg/day for F1 males and 

females).

Results from developmental studies in rats and rabbits provided no 

indication of teratogenic effects for fetuses of either species and no 

evidence of developmental effects in the absence of maternal toxicity. For 

the rat teratology study, doses of 0, 30, 300 or 1000 mg/kg bwt/day were 

administered between Days 6 and 19 of gestation. The NOEL for 

maternal toxicity was 30 mg/kg bwt/day. The NOEL for developmental 

toxicity was 1000 mg/kg bwt/day, the highest dose tested. Pyriofenone

technical was not teratogenic to rats. For the rabbit teratology study, 

doses of 0, 30, 100, or 300 mg/kg bwt/day were administered between 

Days 6 and 27 of gestation. The NOEL for maternal toxicity was 100 

mg/kg bwt/day. The NOEL for developmental toxicity was 300 mg/kg 

bwt/day, the highest dose tested. Pyriofenone technical was not 

teratogenic to rabbits.

4. Subchronic toxicity. Short-term (28-day) toxicity studies were conducted in 

rats and dogs. Doses evaluated in the rat study were 0, 300, 3000, 10,000, 

and 20,000 ppm. The NOEL was 300 ppm (equivalent to 24.2 and 26.1

mg/kg bwt/day, respectively for males and females). Effects observed at 

3000 ppm included hyaline droplets in the kidney proximal tubular cells, 

changes in the blood plasma and increased liver weights for males and 

increased liver weights, increased kidney weights and hepatocyte 

hypertrophy in one animal for females. Doses evaluated in the dog study 

were 0, 500, 1500, 5000, and 15,000 ppm. The NOEL was 5000 ppm for 

males (equivalent to 144 mg/kg bwt/day) and 1500 ppm (equivalent to 

47.5 mg/kg bwt/day) for females. In addition, subchronic (90-day) feeding

studies were conducted in rats, mice, and dogs. Doses evaluated in the rat 

study were 0, 300, 1000, 2500, and 5000 ppm. The NOEL was 1000 ppm 

(equivalent to 60.5 and 69.0 mg/kg bwt/day, respectively for males and 

females). Effects observed at 2500 ppm included high plasma protein, 

albumin, calcium, low chloride, and increased liver, kidney and cecum 

weights. In females at 2500 ppm, increased activated partial 

thromboplastin time and globulin, and increased liver, kidney and cecum 

weights were observed. Doses evaluated in the mouse study were 0, 300, 

1000, 300, and 7000 ppm. The NOEL was 1000 ppm (equivalent to 176 

mg/kg bwt/day) for males and 300 ppm (equivalent to 61.0 mg/kg

bwt/day) for females. Effects included increased liver weights and the 

presence of periportal hypertrophy in males at 3000 ppm and and 

increased liver weight observed in females at 1000 ppm. Doses evaluated 

in the dog study were 0, 500, 3000 and 25,000 ppm in males and 0, 500, 

3000 and 15,000 ppm in females. The NOEL was 3000 ppm (equivalent 

to 90.3 and 89.8 mg/kg bwt/day, respectively for males and females). At 
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the high doses, effects included decreased weight gain and food intake as 

well as increased kidney weights in males, and progressive increase of 

alkaline phosphatase in both sexes.

5. Chronic toxicity. An 18-month oncogenicity study was conducted in mice 

with dietary concentrations of 0, 600, 1800 and 5400 ppm for males and 0, 

300, 1000, and 3000 ppm for females. The systemic NOEL was 600 ppm 

(77.6 mg/kg bwt/day) for males based on non-neoplastic changes in the 

kidney and liver. The systemic NOEL was 1000 ppm (167 mg/kg bwt/day)

for females based on reduced body weights and food consumption. There 

was no evidence of carcinogenicity.

A 2-year chronic toxicity/carcinogenicity study was conducted in rats 

with dietary concentrations of 0, 200, 1000 and 5000 ppm technical 

pyriofenone. The systemic NOEL was 1000 ppm (36.4 mg/kg bwt/day) 

for males based on reduced body weight gains and non-neoplastic 

changes in the kidney, liver, and mesenteric lymph nodes. The systemic 

NOEL was 200 ppm (9.13 mg/kg bwt/day) for females based on reduced 

body weight and non-neoplastic changes in the kidney. There was no 

evidence of carcinogenicity.

A 52-week chronic toxicity study was conducted in dogs with dietary 

concentrations of 0, 500, 3000 and 25,000 ppm for males and 0, 500, 3000, 

and 15,000 ppm for females. The NOEL was 3000 ppm (83.5 and 86.2

mg/kg bwt/day for males and females, respectively). The LOEL was 

25,000 ppm (701 mg/kg bwt/day) for males and 15,000 ppm (448 mg/kg 

bwt/day) for females based decreased weight gain, decreased food intake, 

and increased kidney weights observed for the males and progressive 

increase of alkaline phosphatase observed in both sexes.

6. Animal metabolism. The metabolism of pyriofenone in rats and goats is 

adequately understood. Pyriofenone is rapidly excreted in the urine and 

feces and was extensively metabolized to a number of components 

through a number of metabolic pathways including glucuronidation.

There are no significant qualitative differences between rat and ruminant 

metabolic pathways.

7. Metabolite toxicology. No toxicologically significant metabolites were 

detected in plant or animal metabolism studies. The residue of concern 

for tolerance setting purposes is the parent compound. Consequently, 

there is no additional concern for toxicity of metabolites.

8. Endocrine disruption. The submitted studies include evaluation of the 

potential effects on reproduction and development and an evaluation of 

the pathology of the endocrine organs following short or long-term 

exposure. The data demonstrate no treatment-related effects on the 

endocrine system.
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9. Immunotoxicity. Four-week immunotoxicity studies were conducted in 

female rats and mice. Dietary doses up to 20,000 ppm were evaluated in 

the rat study. There was no effect on the immune system at any dose 

tested. The NOEL was greater than 20,000 ppm (≥1690mg/kg bwt/day). 

Dietary doses up to 7000 ppm were evaluated in the mouse study. There 

was no effect on the immune system at any dose tested. The NOEL was 

greater than 7000 ppm (≥1270mg/kg bwt/day). 

C. Aggregate Exposure

1. Dietary exposure. Exposure assessments were conducted to evaluate the 

potential risk due to dietary exposure of the U.S. population to residues of 

pyriofenone.

For acute dietary exposure, an Acute Reference Dose (aRfD) is not identified for 

Pyriofenone since there was no evidence of initial acute effects in the acute oral or 

short-term toxicity studies, or the developmental toxicity studies in rats and rabbits. 

Furthermore, effects in the acute neurotoxicity study were seen only at the limit 

dose level of 2000 mg/kg/day. No initial acute effects were seen in the 90-day 

neurotoxicity study.

For chronic dietary exposure, the chronic reference dose (cRfD) is 0.106 mg/kg 

bwt/day, based on the NOAEL from the rat combined chronic 

toxicity/carcinogenicity study (10.6 mg/kg bwt/day) and dividing by an uncertainty 

factor of 100. The chronic population adjusted dose (cPAD) is also 0.106 mg/kg 

bwt/day since the FQPA safety factor is anticipated to be 1 for pyriofenone.

i. Food. Tier 1 chronic dietary exposure analyses were conducted for 

pyriofenone in/on grapes to determine the exposure contribution of this commodity

to the diet and to ascertain the chronic risk potential. The exposure estimates were 

based on the proposed tolerance level residues, average processing factors and a

market share of 100% crop treated as a conservative assumption. The consumption 

data were from the USDA’s CSFII (1994 through 1996 and 1998) continuing survey 

of food intake using Exponent's Dietary Exposure Evaluation Module (DEEMFCID) software, version 2.16.

Using all of the worst case exposure scenarios listed above, the Tier 1 chronic 

dietary exposure estimates resulted in an estimated exposure for the general U.S. 

population of 0.000130 mg/kg bwt/day. This exposure corresponds to 0.1% of the 

cPAD of 0.106 mg/kg bwt/day. The highest exposure estimate calculated was for the 

subgroup children, 1-2 years. This exposure was determined to be 0.000753 mg/kg 

bwt/day (0.7% of the cPAD). The chronic dietary exposure analysis is summarized 

in the table below.
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Population Exposure Estimate % of cPAD

Subgroup (mg/kg body wt/day)

U.S. Population 0.000130 0.1

All Infants (< 1 year old) 0.000209 0.2

Children (1-2 years old) 0.000753 0.7

Children (3-5 years old) 0.000456 0.4

Children (6-12 years old) 0.000171 0.2

Youth (13-19 years old) 0.000062 0.1

Females (13-49 years old) 0.000078 0.1

Adults (20-49 years old) 0.000092 0.1

Adults (50+ years old) 0.000083 0.1

It can be concluded that long-term dietary exposure to pyriofenone through 

residues on treated grapes should not be of cause for concern.

ii. Drinking water. Pyriofenone is proposed for use only on an imported 

commodity (grape), therefore the only anticipated exposure route for the US 

population is by dietary (food) exposure. With no proposed US registration, there 

will be no pyriofenone residues in surface or ground water that would be used for 

drinking water.

2. Non-dietary exposure. The proposed use for pyriofenone is for an imported 

commodity (grape). The only anticipated exposure route for the US population is 

via the diet (food only). Therefore, residential and occupational exposure risk 

assessments for the incidental oral, dermal, and inhalation exposure routes are not 

required.

D. Cumulative Effects 

EPA has not made a common mechanism of toxicity finding as to pyriofenone and 

any other substances, and pyriofenone 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 pyriofenone has a common mechanism of 

toxicity with other substances.

E. Safety Determination

1. U.S. population. Based on the completeness and reliability of the toxicity data and 

the conservative exposure assessments, there is a reasonable certainty that no harm 

will result from the aggregate exposure of residues of pyriofenone.
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2. Infants and children. Based on the completeness and reliability of the toxicity data 

and the conservative exposure assessments, there is a reasonable certainty that no 

harm will result to infants and children from the aggregate exposure of residues of 

pyriofenone.

F. International Tolerances

Presently, there are no Codex maximum residue levels (MRLs) established for 

residues of pyriofenone on any crop.