EPA REGISTRATION DIVISION COMPANY NOTICE OF FILING FOR PESTICIDE PETITIONS 

PUBLISHED IN THE FEDERAL REGISTER 

EPA Registration Division contact: Tony Kish, (703) 308-9443

ISK Biosciences Corporation

Petition 5F8352

EPA has received a pesticide petition 5F8352 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 Cyazofamid, 4-chloro-2-cyano-N,N-dimethyl5-(4-methylphenyl)-1H-imidazole-1-sulfonamide (CA) and its metabolite CCIM, 4-chloro-5-(4-

methylphenyl)-1H-imidazole-2-carbonitrile (CA), expressed as cyazofamid in or on the following 

raw agricultural commodities: Bulb Vegetable crop group 3-07, at 2.0 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 plant metabolism of cyazofamid is understood for the purposes 

of this petition. The proposed metabolic pathways in plants (tomato, potato and grape) are 

identical. Nature of the residue studies showed that other than parent cyazofamid, no single 

identifiable residue represents more than about 7% of the total radioactive residue. The nature of 

the residue studies showed that cyazofamid was the major identifiable residue with low levels of 

CCIM. The tolerance expression for the proposed crops, will include parent, cyazofamid, and the 

metabolite CCIM. 

2. Analytical method. Residues of cyazofamid and CCIM were extracted from 5 g samples 

of onions with acetonitrile. After shaking and centrifugation, the extracts were diluted 4 fold with a 

50% acetonitrile/water and filtered through a PTFE filter. The filtrate was diluted 5 fold with 50/50 

acetonitrile/water. The samples were quantitated by LC/MS/MS.

3. Magnitude of residues. Dry Bulb and Green Onions: A total of 15 field trials were 

conducted on dry bulb (10) and green (5) onions during the 2014 growing season. Six (6) foliar 

applications were applied at 7 (+1) day intervals at the target rate of 0.071 lb. a.i./A for a total of 

approximately 0.42 lb. a.i./A/season. Onions were harvested at 0 day PHI. One decline trial was 

included with sampling at 0, 1, 3 and 7 days after the last application. The results show that the 

maximum total residue (cyazofamid + CCIM) after six applications of cyazofamid with a 0 day PHI 

in green onions was 1.16 ppm and in dry bulb onions was 0.89 ppm. 

B. Toxicological Profile

1. Acute toxicity. Results from a battery of acute toxicity studies place technical 
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cyazofamid in Toxicity Category IV for oral LD50, inhalation LC50 and eye irritation, and Category III 

for dermal irritation and dermal LD50. Technical cyazofamid was determined to be a weak dermal 

sensitizer. In an acute neurotoxicity study, no treatment related effects were observed at any dose. 

The NOEL was 2,000 mg/kg bw.

2. Genotoxicty. A battery of five tests has been conducted to assess the genotoxic 

potential of technical cyazofamid. Assays conducted included in vitro reverse gene mutation tests 

in bacteria and in vitro forward gene mutation test in a mammalian cell system, a chromosomal 

damage test in mammalian cells, a DNA repair test in bacteria, and an in vivo micronucleus test in 

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

3. Reproductive and developmental toxicity. In a two-generation reproductive toxicity study, 

the only effects observed were body weight effects which were observed at 20,000 ppm in dams 

during gestation and lactation and in weanling pups. No reproductive effects were observed. The 

NOEL for reproductive effects was 20,000 ppm (1,338 mg/kg bw/day). The NOEL for parental 

toxicity was 2,000 ppm (134 mg/kg bw/day).

In a rat developmental study, pregnant rats were dosed by gavage with cyazofamid from Days 0 to 

19 of gestation. There were no treatment-related effects observed in the study. The NOEL for 

maternal effects was 1,000 mg/kg bw/day. Due to the increased incidence of bent ribs, a 

reversible developmental anomaly, in fetuses treated at the highest dose, the developmental NOEL 

was set conservatively at 100 mg/kg bw/day. 

In a rabbit developmental study, pregnant rabbits were dosed by gavage with cyazofamid on Days 

4 to 28 of gestation. There were no treatment-related effects observed in the study. The NOEL for 

maternal and developmental effects was 1000 mg/kg bw/day.

The developmental studies (prenatal developmental studies in rat and rabbit and the two 

generation reproduction study in rat) provided no indication of increased sensitivity of rats or 

rabbits from in utero or post-natal exposure to cyazofamid. Cyazofamid is not a developmental or 

reproductive toxicant.

4. Subchronic toxicity. The oral toxicity of cyazofamid was investigated in rats and dogs in 

13-week studies. The exposure was by dietary administration for the rats and by capsule for the 

dogs. There were no treatment-related effects observed in dogs up to 1,000 mg/kg bw/day which 

was the highest dose tested. In rats, treated at 5,000 ppm there was a treatment related increase 

in kidney and liver weights and increased observation of basophilic tubules. The latter was 

observed only in males. The NOEL was 500 ppm which was equivalent to a dosage of 29.9 mg/kg 

bw/day to males and 33.3 mg/kg bw/day to females.

5. Chronic toxicity. A combined chronic and oncogenicity study was conducted in rats. 

Cyazofamid was administered continuously for a period of 104 weeks to male and female Fischer 

rats. Cyazofamid was not carcinogenic in this study. The NOEL for chronic effects was 5000 ppm 

(171 mg/kg bw/day).

In a long-term feeding study, mice were dosed with cyazofamid in the diet for 78 weeks. There 

was no evidence of carcinogenicity. The NOEL was 700 ppm (94.8 mg/kg bw/day for males) 

based on increased incidence of skin lesions in the high dose animals.

In a chronic dog study, four groups of six dogs/sex/group received cyazofamid via capsule for 52 

weeks. The NOEL was determined as 200 mg/kg bw/day based on increased cysts in parathyroids 

in both sexes and increased pituitary cysts in females at the LOAEL of 1,000 mg/kg bw/day.
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6. Animal metabolism. Studies on the metabolism of cyazofamid in animals using 

radioactive test material have been conducted with cyazofamid, labeled with 14C in two positions, 

the benzene [14C-Bz]- or imidazole [14C-Im] position. Absorption is rapid, but the percentage of 

Cyazofamid absorbed after an oral dosage decreases as the dosage is increased. All absorbed 

radiocarbon is rapidly eliminated with urinary and biliary elimination of radiocarbon nearly complete 

within 24 hours. The metabolic pathway of cyazofamid includes the rapid hydrolysis of the 

dimethylsulfonamide group and the oxidation of the benzyl methyl group.

7. Metabolite toxicology. Comparison of the metabolism of cyazofamid by plants and in 

animals indicates that a number of the identified metabolites are common to both plants and 

animals but metabolism in plants is more extensive than in animals. The data indicate that the final 

products of the metabolism of cyazofamid in animals and plants represent differences in the extent 

of metabolism. Several of the metabolites resulting from cyazofamid are similar in plants and 

animals and, therefore, have already been evaluated toxicologically.

8. Endocrine disruption. An evaluation of the potential effects on the endocrine systems of 

mammals has not been determined; however, no evidence of such effects was reported in 

subchronic, chronic or reproductive toxicology. There was no observed pathological finding of the 

endocrine organs in these studies, and there were no reproductive effects at the maximum dose 

tested of 20,000 ppm. There is no evidence at this time that cyazofamid causes endocrine effects.

C. Aggregate Exposure

1. Dietary exposure. Potential dietary exposures from food were estimated for all

proposed and established tolerances for the crops listed below, using the Dietary Exposure 

Evaluation Model-Food Consumption Intake Database (DEEM-FCIDTM) version 2.16, and percent 

crop treated of 100%. The following raw agricultural commodities were included: beans, snap and 

lima; dry bulb and green onions (bulb vegetable crop group 3-07); leafy greens (subgroup 4A); 

brassica (cole) leafy vegetables (crop group 5) including turnip greens; carrots; cucurbits (crop 

group 9); fruiting vegetables (crop groups 8-10); tuberous and corm vegetables (subgroup 1C);

grapes; basil; chives; and hops. 

For chronic dietary exposure, the chronic reference dose (RfD) of 0.95 mg/kg bw/day was

proposed by EPA for humans, based on the NOAEL from the mouse carcinogenicity study (94.5 

mg/kg bw/day) and dividing by an uncertainty factor of 100. The chronic population adjusted dose 

(cPAD) is also 0.95 mg/kg bw/day since the FQPA safety factor is 1 for cyazofamid.

For acute dietary exposure, the acute RfD of 1.0 mg/kg bw/day was based on the NOAEL of 100 

mg/kg bw/day from the rat developmental toxicity study adjusted by the uncertainty factor of 100. 

The acute population adjusted dose (aPAD) is also 1 mg/kg bw/day since the cyazofamid FQPA 

safety factor is 1.

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

cyazofamid in/on the crops noted above to determine the exposure contribution of these 

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

based on current and proposed tolerance level residues for all crops, potato and tomato processing 

studies, conservative market share assumptions of 100% crop treated, and consumption data from 

the USDA’s CSFII (1994 through 1996 and 1998) continuing survey of food intake. Since specific 
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processing studies demonstrated that residues were unlikely to concentrate in processed 

commodities, no adjustment for processing factors was necessary.

Even using all of the worst case exposure scenarios listed above, the Tier 1 chronic dietary (food + 

drinking water) exposure estimates resulted in an estimated exposure for the general U.S. 

population of 0.008632 mg/kg bw/day. This exposure corresponds to 0.9% of the cPAD of 0.95 

mg/kg bw/day. The highest exposure estimate calculated was for the subgroup, non-nursing 

Infants. This exposure was determined to be 0.017515 mg/kg bw/day (1.8% of the cPAD).

A Tier 1 acute dietary exposure assessment was performed for the subpopulation of females aged

13-49 years old only, since the only endpoint of concern was from the rat prenatal developmental 

study. The acute dietary exposure estimate for females aged 13-49 is 0.045281 mg/kg bw/day,

well below HED’s level of concern at the 95th percentile. This is equivalent to 2.60% of the aPAD.

It can be concluded that acute or long-term dietary exposure to cyazofamid through residues on 

treated beans, snap and lima, dry bulb and green onions (bulb vegetable crop group 3-07), leafy 

greens (subgroup 4A), brassica (cole) leafy vegetables (Crop Group 5), including turnip greens,

carrots, cucurbit vegetables (Crop Group 9), fruiting vegetables (Crop Group 8-10), tuberous and 

corm vegetables (subgroup 1C), grapes, herbs (Crop Subgroup 19A), and hops, should not be of 

cause for concern.

ii. Drinking water. Since cyazofamid is intended for application outdoors to turf, 

ornamentals, and field grown crops, the potential exists for parent and or metabolites to reach 

ground or surface water that may be used for drinking water. EPA assumed drinking water 

concentrations of 133 ppb and 136 ppb for the chronic and acute assessments, respectively, based 

on modeling of potential surface water residues of CTCA (the terminal degradate of cyazofamid) 

for the turf/ornamental use. Because the application rates for the proposed uses are lower than 

the rate for turf/ornamentals, the turf use represents the worst-case for potential drinking water 

residues. Therefore, these estimates of drinking water were directly entered into the dietary 

exposure model.

2. Non-dietary exposure. Cyazofamid can be applied to commercially treated residential 

turf and ornamentals only. Therefore, non-occupational exposure of cyazofamid to the general 

population is not expected, however, postapplication exposure is possible. For Dermal Short-Term 

exposure, no toxicity was found at 1000 mg/kg in a 28-day dermal toxicity study, therefore, in the 

absence of any hazard identified for children, a risk assessment was not necessary. The 

residential dermal MOE for adults of 1,100, based on 2 hours of extensive contact with the turf,

was used to calculate the adult short-term aggregate risk assessment in the EPA assessment. 

EPA calculated non-occupational/residential MOEs for the day of application. 

The post application children’s MOE (including incidental oral exposures) from residential lawns is 

1,600. All MOEs, including children’s aggregate, are greater than 100, and therefore, are not of 

concern. 

D. Cumulative Effects

Cyazofamid is a cyanoimidazole fungicide. Since there are no other members of this class of 

fungicides, it is considered unlikely that cyazofamid would have a common mechanism of toxicity 

with any other pesticide in use at this time.
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E. Safety Determination

1. U.S. population. Dietary and occupational exposure will be the major routes of exposure 

to the U.S. population. Ample margins of safety have been demonstrated for both situations. For 

the general U.S. population, the chronic dietary exposure to cyazofamid is 0.008632 mg/kg bw/day, 

which utilizes less than 1% of the RfD for the overall U.S. population, assuming 100% of the crops 

are treated. A cancer dietary assessment was not conducted because this product has been 

classified as “not likely to be carcinogenic to humans.”

An acute aggregate risk assessment was conducted for the population subgroup of concern, 

females 13-49 years old. Since an appropriate endpoint for the general population was not 

identified, a corresponding assessment is not required for any other population subgroup. For this 

subgroup, the acute dietary (food and drinking water) risk assessment reported above as 0.045281

mg/kg bw/day (95th percentile), 2.60% of the aPAD, represents the acute aggregate risk since the 

dietary route alone is relevant for acute exposure and risk assessment.

The short-term aggregate risk is made up of average dietary exposures from food and drinking 

water sources as well as from dermal and oral residential exposure. Potential inhalation exposure 

was not considered since it is negligible when assessing re-entry risks. The aggregate short-term 

MOE for the US general population is 1018.

Using only pesticide handlers exposure data base (PHED) data levels A and B (those with a high 

level of confidence), the margins of exposure (MOE) for occupational exposure are 341 to 98,000 

for use on turf and ornamentals and of 23,000 to 220,000 for use on crops. 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 

cyazofamid including all anticipated dietary exposure and all other non-occupational exposures.

2. Infants and children. As noted above, chronic dietary exposure of the most highly 

exposed subgroup in the population, non-nursing infants, is 0.017515 mg/kg bw/day or 1.8% of the 

RfD. The short-term aggregate risk MOE for children (food and residential) is 1325. Thus, it can be 

concluded that there is reasonable certainty that no harm will result to infants and children from 

acute or chronic exposure to Cyazofamid.

Based on the completeness and reliability of the toxicity data, the lack of toxicological endpoints of 

special concern, the lack of any indication of greater sensitivity of children, and the conservative 

exposure assessment, there is a reasonable certainty that no harm will result to infants and 

children from the aggregate exposure to residues of cyazofamid from all anticipated sources of 

dietary and non-occupational exposure. 

F. International Tolerances

Presently, there is no Codex maximum residue levels (MRLs) established for residues of 

cyazofamid on any crop. The following Canadian tolerances have been established: Carrots, 0.09 

ppm; Potatoes, 0.02 ppm; and Tomatoes (Import), 0.2 ppm; Cucurbits, 0.1 ppm; Grape (Import), 

1.2 ppm; and Spinach, 9.0 ppm.