EPA Registration Division contact: Susan Lewis; (703)308-8009

Interregional Research project number 4 (IR-4)

PP #5F8384

EPA has received a pesticide petition (PP #5F8384) from Interregional Research 

Project No. 4, Rutgers, The State University of New Jersey, 500 College Road East, Suite 

201W, Princeton, NJ 08540, requesting, 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 fluensulfone equivalents (i.e., the sum of thiazole 

sulfonic acid (TSA) and butene sulfonic acid (BSA) expressed as total fluensulfone 

equivalents) in or on the raw agricultural commodity Vegetable, tuberous and corm, 

subgroup 1C at 0.6 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. Fluensulfone is supported by a complete plant metabolism 

data package based on the uses in fruiting vegetables (crop group 8) and cucurbit 

vegetables (crop group 9). In all plant matrices, whether from a primary or rotational 

crop, a clear pattern was observed with TSA (M-3625) and BSA (M-3627) forming the 

majority of the residues following the cleavage of fluensulfone. Neither compound has 

acute oral toxicity greater than parent fluensulfone or shows any genotoxic potential in a 

range of mutagenicity studies. The residues definition for both monitoring and risk 

assessment should therefore be the sum of TSA and BSA, expressed as fluensulfone 

equivalents. 

2. Analytical method. Adequate analytical methods for determining fluensulfone 

in/on appropriate raw agricultural commodities and processed commodities have been 

developed and validated, including LC-MS/MS methods. The analytical procedures have 

been successfully validated in terms of specificity, linearity, precision, accuracy and 

LOQ. 

The MRM study demonstrates that the FDA multiresidue methods (MRMs) are 

not suitable for detection and enforcement of fluensulfone residues as sulfonic acid 

metabolites in non-fatty matrices.

3. Magnitude of residues. Fluensulfone is proposed for use on Vegetable, tuberous 

and corm, subgroup 1C. To support these uses IR-4 sponsored a total of twenty two field 

trials. The trials were located in Florida (one trial; EPA region 3), Idaho (two trials; EPA 

region 11), California (one trial; EPA region 10), New Mexico (one trial; EPA region 9), 

Ohio (one trial; EPA region 5), Wisconsin (one trial, EPA region 5), New York (one trial, 

EPA region 1), Maryland (one trial, EPA region 2), Washington (three trials; EPA region 
2

11), Nova Scotia (two trials, EPA region 1a), Ontario (1 trial, EPA region 5a), Quebec 

(one trial, EPA region 5a), Alberta (two trials, EPA region 14), New Brunswick (2 trials, 

EPA region 1) and Saskatchewan, (2 trials, EPA region 7a or 14). The number of field 

trials is in accordance with OPPTS Guideline 860.1500. Fluensulfone and BSA (M-3627)

and thiazole sulfonic acid (TSA, M-3625) were sought in all samples. The LOQ is 0.01 

mg/kg. EPA removed the fluensulfone metabolite methyl sulfone (M- 3626) from the 

residue definition therefore this was not included in the residue analysis. 

Adequate data are available to propose this tolerance (MRL) and there is no unacceptable 

risk to consumers from the consumption of processing potatoes treated with formulations 

containing fluensulfone.

B. Toxicological Profile

1. Acute toxicity. The acute oral LD50 is 671 mg/kg bw in rats. The acute dermal 

LD50 of fluensulfone is >2000 mg/kg bw. The acute inhalation LD50 in rats is >5.1 mg/L. 

Fluensulfone displayed no eye irritation in rabbits. Fluensulfone is not irritating to the 

skin and is a skin sensitizer. 

2. Genotoxicty. A complete data package of in vitro and in vivo mutagenicity 

studies is available for fluensulfone. A full summary of the genotoxicity database is 

provided in the OECD Dossier. On the basis of the robust in vitro and in vivo 

mutagenicity data, it is concluded that fluensulfone does not possess any genotoxic 

potential.

3. Reproductive and developmental toxicity. The reproductive toxicity of 

fluensulfone was evaluated in a 2-generation reproduction study in rats. Developmental 

toxicity was assessed in rats and rabbits. 

Reproductive toxicity. A 2-generation reproduction study in rats was conducted 

at dose levels of 0, 30, 250 and 1800 ppm (2.0, 16.2, and 122.0 mg/kg/day in males and 

2.8, 23.0 and 169.1 mg/kg/day in females). Treatment with fluensulfone up to and 

including 1800 ppm, the highest tested dose level, showed no effects on reproductive 

function, including gonadal function, mating behavior, fertility, viability of offspring, 

breeding, conception, gestation and parturition. 

Parental systemic toxicity was evident however, with effects on body weight 

development throughout the study observed at 1800 ppm (the LOAEL); hence the 

NOAEL was set at 250 ppm (equivalent to approximately 16.2 mg/kg/day in males and 

23.0 mg/kg /day in females). A NOAEL for general toxicity in F1 and F2 pups was 

established at 250 ppm, based on reduced pup weight noted at 1800 ppm.

Developmental toxicity. Fluensulfone was not teratogenic or fetotoxic either in 

rats or rabbits. 

A pre-natal developmental study in rats included dose groups of 0, 7.7, 48.6, and 

292.0 mg/kg/day. Maternal toxicity, manifested as decreased body weight gain and food 
3

consumption in rats, resulted in a lower body weight of female pups; the maternal and 

developmental NOAEL was set at 48.6 mg/kg/day.

A pre-natal developmental study in rabbits included dose groups of 0, 2.5, 10 and 

40 mg/kg/day. Similarly, as with the study in rats, treatment of rabbits at 40 mg/kg/day 

resulted in slight maternal toxicity consisting of reduction in food consumption at the 

onset of the treatment and between days 18 and 24, and reduced mean body weight gain 

at the beginning of the treatment only. As the lower fetal weights recorded at this dose 

level were within the range of the historical control data, the NOAEL for maternal and 

developmental toxicity was considered to be 40 mg/kg/day, the highest dose tested.

4. Subchronic toxicity. Repeated dose, oral (dietary) toxicity studies with 

fluensulfone are available for rats, mice and dogs. The studies conducted include 28-day 

and 90-day studies in the rat, mouse, and dog. In addition, a 1-year oral toxicity study in 

dogs and a 28-day dermal toxicity study in rats were performed.

The rat 28-day study was conducted at dose levels of 0, 125, 500, and 2000 ppm (0, 10.4, 

42.5, and 152 mg/kg/day in males and 0, 12.2, 37.2, and 165.9 mg/kg/day in females). 

The NOAEL was 125 ppm (10.4 and 12.2 mg/kg day in males and females respectively), 

based on results at the LOAEL of functional effects in the liver and kidney effects, which 

were considered adverse as a precaution but likely of no toxicological relevance.

The mouse 28-day study was conducted at dose levels of 0, 100, 500, and 2000 ppm (0, 

30.33, 101.31, and 374.5 mg/kg/day in males and 0, 41.32, 155.12, and 353.0 mg/kg/day 

in females). The NOAEL was 100 ppm (30.33 and 41.32 mg/kg/day in males and 

females respectively), based on results at the LOAEL of decreased food consumption and 

liver toxicity (increased relative weight, histopathological findings). 

The dog 28-day study was conducted at dose levels of 0, 50, 200, and 900 ppm (1.9, 7.3, 

and 30.9 mg/kg/day in males and 2.0, 7.9, and 29.7 mg/kg/day in females). The NOAEL 

was 200 ppm (7.3 and 7.9 mg/kg/day in males and females respectively), based on results 

at the LOAEL of slight changes in food consumption, body weight and organ weight 

(liver and thyroid) and on hepatic tissue enzyme activities. 

The rat subchronic 90-day study was conducted at dose levels of 0, 60, 120, 500 and 

2000 ppm (4.31, 8.26, 34.86, and 139.01 mg/kg/day in males and 4.85, 11.68, 53.10 and 

148.73 mg/kg/day in females). The NOAEL was 120 ppm (8.3 and 11.7 mg/kg/day in 

males and females respectively), based on results at the LOAEL of decreased body 

weight/body weight gain in males, increased water consumption in males and increased 

triglycerides in females. 

The mouse subchronic 90-day study was conducted at dose levels of 0, 60, 300, and 1500 

ppm (11.06, 50.85, and 228.53 mg/kg/day in males and 18.33, 68.47 and 252.49 

mg/kg/day in females). The NOAEL was 60 ppm (11.06 and 18.33 mg/kg/day in males 

and females, respectively), based on results at the LOAEL of decreased food 

consumption in females and marginal effects in liver and hematological findings in 

males. 
4

The dog subchronic 90-day study was conducted at dose levels of 0, 5, 50, and 500 ppm 

(0.2, 1.6 and 17.1 mg/kg/day in males and 0.2, 1.8 and 18.0 mg/kg/day in females). The 

NOAEL was 500 ppm (17.1 and 18.0 mg/kg/day in males and females, respectively), 

based on only slight and reversible liver effects at the top dose tested. 

The rat 28-day dermal study was conducted at dose levels of 0, 80, 400, and 2000 

mg/kg/day in males and females. Only a minimal increase in the incidence of 

acanthosis/hyperkeratosis was observed at the limit dose of 2000 mg/kg/day. However, 

because of the moderate degree recorded in comparison to the vehicle control, the finding 

was considered adaptive and likely to be reversible after cessation of treatment and on 

this basis not adverse. The NOAEL was 2000 mg/kg/day, the highest dose tested, based

on no systemic or adverse dermal effects at the highest dose level tested.

In all species the liver appears to be the main target organ, although often the observed 

effects were limited to adaptive changes (e.g. hepatocyte hypertrophy concomitant to 

increased weight, induction of mainly phase II activities). Investigations on liver enzyme 

activities in all species revealed that fluensulfone administration does not result in 

significant induction of (activating) phase I cytochrome P450 subfamilies, but that the 

(conjugating) phase II enzymes were induced. Frank hepatotoxicity was observed only at 

very high doses, and only in mice.

The NOAEL for oral subchronic toxicity is 8.3 mg/kg bw/day based on decreased body 

weights in males (and supported by increased triglycerides in females at the same dietary 

dose) in the 90 day rat study. The NOAEL for dermal subchronic toxicity is 2000 mg/kg 

bw/day, based on absence of adverse effects at the highest test dose in the rat 28-day 

dermal toxicity study.

5. Chronic toxicity. The long-term toxicity and carcinogenicity potential of 

fluensulfone was evaluated in dogs (one year study), rats (combined study for chronic 

toxicity and carcinogenicity), and mice (carcinogenicity). 

In a 1-year oral toxicity study in dogs, fluensulfone was administered in the diet at 0, 5, 

50 100 and 500 ppm (0.1, 1.5, 3.1, and 19 mg/kg/day in males and 0.1, 1.5, 3.3, and 16.2 

mg/kg/day in females) to purebred Beagle dogs for a period of 52 weeks with selected 

animals retained for an 8-week recovery period. The NOAEL was considered to be 100 

ppm (3.1 mg/kg bw/day in males and 3.3 mg/kg bw/day in females), based on decreased 

body weight and body weight gains, decreased hemoglobin, MCH, MCHC and increased 

kidney weights at 500 ppm (16.0 and 16.2 mg/kg/day in males and females respectively) 

in the diet.

A combined chronic dietary toxicity and carcinogenicity study in rats was conducted with 

0, 30, 200, and 1200 ppm dose groups (1.6, 11 and 66.3 mg/kg/day after 52 weeks and 

1.4, 9.6 and 57.7 mg/kg/day after 104 weeks in males; 1.9, 13.1 and 75.2 mg/kg/day after 

52 weeks and 1.7, 11.6 and 69.3 mg/kg/day after 104 weeks in females). Fluensulfone 

showed no carcinogenic potential in this study, and the NOAEL for lifespan treatment (2-

years) was set at 30 ppm (1.4 mg/kg/day in males and 1.7 mg/kg/day in females) on the 
5

basis of chronic interstitial inflammation in the lungs of females, decreased body weight 

and body weight gain in males, and decreased hemoglobin concentration and hemoglobin 

concentration distribution width in females receiving 200 ppm.

A 78-week dietary carcinogenicity study in mice was conducted with 0, 30, 200, and 

1200 ppm dose groups (4.2, 27.6 and 152.3 mg/kg/day in males and 6.4, 39.0, and 188.4 

in females). The overall NOEL in mice following lifespan treatment was set at 30 ppm 

(4.2 and 6.4 mg/kg/day in males and females, respectively). In mice, treatment with 

fluensulfone for 78 weeks resulted in an increased incidence of alveolar/bronchiolar 

adenomas in females receiving 200 and 1200 ppm. Mechanistic studies were carried out 

to determine the relevance for humans of this finding. Tumors were found to be a 

species-specific effect in mice due to activation of fluensulfone by mouse lung Clara 

cells, leading to local cytotoxicity, cell proliferation and finally formation of benign 

tumors. Rats have lower metabolic activity in the lungs compared to mice (below the 

threshold needed to cause lung tumors upon lifetime exposure) and activity in humans is 

orders of magnitude lower than rats. Fluensulfone was found to be extensively 

metabolized by mouse lung microsomes, whereas no metabolic activity was seen in 

human lung microsomes. In accordance with the International Programme on Chemical 

Safety (IPCS) mode of action and human relevance framework, it is concluded that 

fluensulfone leads to species-specific tumors via a non-genotoxic threshold mode of 

action in the mouse lung, and that these tumors are not relevant to human hazard or risk.

The NOAEL for lifespan treatment was set at 1.4 mg/kg/day on the basis of decreased 

body weight and body weight gain in males (supported by chronic interstitial 

inflammation in the lungs and decreased hemoglobin concentration and hemoglobin 

concentration distribution width in females).

6. Neurotoxicity. Acute and subchronic specific neurotoxicity studies (i.e. 

inclusive of neuropathology) were carried out, and functional observation batteries 

(FOBs) and motor activity assessments were included in the repeated dose/chronic 

studies with fluensulfone. The FOBs and motor activity assessments conducted within 

the repeated dose/chronic toxicity studies revealed no effects.

In an acute oral neurotoxicity study in rats, groups of 10 male and 10 female Wistar rats 

were administered single oral doses of 0 (control), 100, 400 and 1200 mg/kg bw of 

fluensulfone by oral gavage and observed for 14 days. No test item-related effects on 

absolute and relative brain weights were evident, and there were no findings in the 

nervous system during macroscopic and microscopic pathology examinations. The 

LOAEL for general toxicity is 100 mg/kg bw in males and females, based on the general 

systemic toxicity due to the bolus dose. The NOAEL for neurotoxicity is 100 mg/kg bw 

in males and females, based on reduced activity in the functional observation battery and 

decreased motor activity at 400 mg/kg in absence of any neuropathological finding at any 

dose level.

In a subchronic dietary neurotoxicity study, groups of 12 male and 12 female 

RccHan:WIST (SPF) rats received fluensulfone in their diet at concentrations of 0 
6

(control), 100, 500 and 2500 ppm (0, 6, 31, and 153 mg/kg/day in males and 0, 7, 34, and 

162 mg/kg/day in females) for at least 90 days. Treatment-related effects were confined 

to lower food consumption, body weight and body weight gain in males and females at 

2500 ppm. These treatment-related effects were attributed to systemic toxicity, and not to 

neurotoxicity. No effects on functional parameters or neurohistopathology were 

observed. Therefore, the high dose level of 2500 ppm was the ‘no-observed-effect level’ 

(NOEL) for neurotoxicity associated with dietary exposure, equivalent to 153 mg/kg 

bw/day in males and 162 mg/kg bw/ day in females. The no-observed-adverse-effect 

level (NOAEL) for systemic toxicity was 500 ppm equivalent to 31 mg/kg bw/day for 

males and 34 mg/kg bw/day for females. 

As developmental studies did not indicate that the offspring are more sensitive than the 

adult, and neuropathological effects were not observed in any of the performed 

neurotoxicity studies, a developmental neurotoxicity study was considered not necessary.

7. Immunotoxicity. Although immunotoxicity endpoints were already included in 

the 28-day dietary study in rats and mice, fluensulfone was tested also in mice in the 28-

day sheep red blood cell assay, to evaluate its immunotoxicity potential. In addition, the 

entire available data set was examined to check immunotoxicity-related endpoints. It is 

concluded that fluensulfone is not an immunotoxic substance.

8. Animal metabolism. Fluensulfone (labeled at the thiazole and the butenemoieties of the molecule) administered orally to rats at nominal single doses of either 5 

mg/kg or 500 mg/kg is rapidly metabolized. The recovery of radioactivity was essentially 

complete for all groups of rats. The disposition and excretion of radiolabel for males and 

females were generally similar. There was no indication that the metabolic elimination 

processes were saturated by the 100-fold increase in dose level, as levels of radiolabel in 

urine, cage wash, feces, carcass, and gastro-intestinal (GI tract) were similar. 

Urine was the major route of excretion and the only source of metabolites at ≥5% of the 

applied radiolabel. The cage wash contained relatively high levels of radiolabeled 

metabolites and analysis showed that those metabolites in cage wash and urine were 

similar. Low amounts of thiazole sulfonic acid were found in feces, but no other fecal 

metabolites were ≥5% of the applied dose. Fluensulfone is not a significant residue in 

either urine or feces. 

In addition to investigating metabolism after a single dose, the tissue distribution was 

studied when the dosing of radioactivity was preceded by 14 days administration of 

unlabelled material. The results indicate that distribution is comparable in both cases.

7. Metabolite toxicology. The acute oral LD50 of fluensulfone metabolite M-3625

was greater than 2000 mg/kg(less than that of the parent fluensulfone). 

Metabolite M-3625 was tested for its genotoxic potential in a bacterial reverse gene 

mutation assay, an in vitro chromosome aberration assay in mammalian cells, and an in 

vivo micronucleus assay in the bone marrow of rat. No genotoxic properties were 

identified.
7

The acute oral LD50 of fluensulfone metabolite M-3627 (BSA) was greater than 

2000 mg/kg bw (less than that of the parent fluensulfone). 

Metabolite M-3627 was tested for its genotoxic potential in a bacterial reverse gene 

mutation assay, an in vitro chromosome aberration assay in mammalian cells, and an in 

vivo micronucleus assay in the bone marrow of rat. No genotoxic properties were 

identified.

8. Endocrine disruption. Evidence from the large available toxicological data set 

demonstrates that fluensulfone does not exert any adverse effects on thyroid gland, 

reproductive system and related endocrine organs and adrenal glands. Therefore, it is 

concluded that fluensulfone does not possess any endocrine disrupting potential.

C. Aggregate Exposure

1. Dietary exposure. Acute and chronic dietary (food + water) exposures to 

fluensulfone have been recently conducted and this proposed use is not likely to 

significantly impact the previous conclusions. The recent drinking water modeling 

conducted by EPA (2014) is still relevant and results were incorporated into the 

assessment. Based on livestock metabolism studies, no residues of concern (parent 

fluensulfone) are expected in milk or any animal tissue. A Tier 1 acute dietary exposure 

assessment was conducted assuming tolerance-level residues, 100% crop treated and 

default processing factors. Exposure was assessed using the acute and chronic 

toxicological endpoints determined by EPA (2014), which are an aPAD of 0.16 mg/kg 

bw/day derived from a NOAEL of 16.2 mg/kg bw/day from a 2-generation reproduction 

rat study and a cPAD of 0.03 mg/kg bw/day derived from a NOAEL of 3.1 mg/kg bw/day 

from co-critical 90-day dog and chronic dog studies. EPA has determined that the level of 

concern for fluensulfone for acute and chronic exposures is 100 (EPA, 2014).

Acute Dietary Exposure. Acute dietary (food + water) exposures to fluensulfone, 

which were calculated using DEEM- FCID version 4.02, for a recent 2014 submission. 

The reported exposures correspond to the 95th percentile of the exposure distributions, as 

is appropriate for a Tier 1 acute dietary exposure assessment. The 95th percentile acute 

dietary (food + water) exposures are well below the aPAD (0.16 mg/kg/d). For all infants, 

the most highly exposed subpopulation, 95th percentile acute dietary exposures 

correspond to 9.13% of the aPAD. For the general U.S. Population, 95th percentile acute 

dietary exposures correspond to 2.79% of the aPAD. Acute dietary exposures below 

100% of the aPAD are reasonably anticipated to result in no harm to exposed 

populations.

Chronic Dietary Exposure. Chronic dietary exposures to fluensulfone, which 

were calculated using DEEM-FCID version 4.02, was also recently conducted. Chronic 

dietary exposures are less than the cPAD (0.03 mg/kg/d). For infants, the most highly 

exposed subpopulation, chronic dietary exposures correspond to 15.1% of the cPAD. For 

the general U.S. Population, chronic dietary exposures correspond to 4.0% of the cPAD. 
8

Chronic dietary exposures below 100% of the cPAD are reasonably anticipated to result 

in no harm to exposed populations.

i. Food. Exposure to fluensulfone through food is included in the dietary 

assessment section above. 

ii. Drinking water. Exposure to fluensulfone through water is included in the 

dietary assessment section above. 

2. Non-dietary exposure. Fluensulfone is currently not registered for use on any 

residential non-food site. Therefore, residential exposure to fluensulfone residues will be 

through dietary exposure only.

D. Cumulative Effects

Fluensulfone is a member of a new chemical class of nematicides with a specific 

toxicological profile. It does not share a known toxicological mode of action with other 

pesticides. Thus, no cumulative effects are foreseen.

E. Safety Determination

1. U.S. population. Using the conservative exposure assumptions described above 

and based on the completeness of the toxicity data, it can be concluded that total food 

and drinking water exposure to fluensulfone from all proposed crop uses will be 

2.79% of the aPAD and 4.0% of the cPAD for the overall US population.

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

and based on the completeness of the toxicity data, it can be concluded that the total acute 

food and drinking water exposure to fluensulfone from all proposed crop uses will be 

9.13% (all infants), 4.21% (children 1-2 yrs), 3.53% (children 3-5 yrs), and 2.46% (6-12 

yrs) of the aPAD. It can be concluded that the total chronic food and drinking water 

exposure to fluensulfone from all proposed crop uses will be 15.1% (all infants), 6.2% 

(children 1-2 yrs), 4.9% (children 3-5 yrs), and 3.5% (children 6-12 yrs) of the cPAD.

F. International Tolerances

No Codex Maximum Residue Levels (MRLs) have been established for residues 

of fluensulfone on any crops. MRL’s have been set by Canada for Import Tolerance 

purposes. There are no established tolerances for fluensulfone in Mexico.