UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

DATE: 5/01/13 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: Captan: Human Health Risk Seeping Document in Support of Registration 

Review. 

PC Code: 081301 

Decision No.: 478164 

Petition No.: N/ A 

Risk Assessment Type: Seeping Document 

TXRNo.:N/A 

MRID No.: N/ A 

DP Barcode: 411433 

Registration No.: 7042-1 

Regulatory Action: Registration Review 

Case No.: 0120 

CAS No.: 133-06-2 

40 CFR: §180.103 

Jessica Kidwell, Risk Assessor ~ ~() Ayaad Assaad, D.V.M., Ph.D., TOxicologist . ;:J?~ Bonnie Cropp-KohlligianlC mist/Diejao:_ ~XB,OS)lre .-")(_a.:__ /.(or ed)\":e... ~ _{<-

FROM: 

James Scott Miller, ORE ,...__._~ /~ 

Risk Assessment Branch , Health Effects Division (7509P) 

THROUGH: Elissa 

RAB IV, 

Reaves, 

Health 

Ph.D., 

Effec

Branch 

ts Division 

Chief 

(7509P) 

~ ({}~'- / (ay- 8:::.5, ~ 

TO: Christina Scheltema, Chemical Review Manager 

Tracy Perry, Team Leader 

RMIB3, PRD (7508P) 

EXECUTIVE SUMMARY 

Attached is the Health Effects Division's (HED) human health risk assessment seeping 

document for cap tan conducted as part of the Registration Review process. The HED 

Registration Review Team has evaluated the most recent human health risk assessments and 

databases for cap tan to determine the scope of the work necessary to support Registration 

Review. The most recent human health risk assessments for captan were the 1999 Captan 

Reregistration Eligibility Decision (RED) document (EPA 738-R-99-015) and the 2004 

Amendment to the 1999 Captan RED. 
Captan/08130 1 Scoping Document 

Cap tan (N-trichloromethylthio-4-cyclohexene-1 ,2-dicarboximide) is a fw1gicide that belongs to 

fungicide resistance group M4 according to the Fungicide Resistance Action Committee (FRAC, 

2012). Captan is a broad-spectrum fungicide with protectant and some curative activity. Captan 

is registered for use on food crops including foliar uses on almonds, apples, apricots, blueberries, 

caneberries (including blackberries, dewberries, and raspberries (black, red)), cherries, ginseng 

(considered non-food use), grapes, nectarines, peaches, pears, plums, and strawberries. It is also 

used as a root dip and as a seed treatment for numerous crops, as well as, a postharvest fruit dip 

on apples, cherries and pears. 

Furthermore, captan is used on non food crops including ornan1ental herbaceous plants, turf, 

ornamental woody shrubs and vines, ornamental trees, wood structure protection and greenhouse 

soils. According to EPA's most recent Label Use Information System (LUIS) report (dated 

9/1 0/12), all of the previously registered antimicrobial uses of captan have been canceled; hence, 

these former uses will not be discussed further herein. 

Captan is applied by broadcast, chemigation, dust and drip tTeatment to soil, and as a spot 

application treatment. Furthermore, water dispersible granules (WDG) and liquid tlowable 

concentrates (LFC) are used for foliar application to food plants and applied by aerial and 

ground equipment (air blast and ground boom), while field grown ornamentals and golf course 

turf is treated via ground boom equipment. These formulations may also be applied to 

greenhouse ornamentals, fruit (nut trees in home gardens), directly to the soi£ around plants in 

greenhouses using hand held equipment such as a backpack sprayer, low pressw·e hand wand, 

and a garden hose-end sprayer. Wettable powders (WP), flowable concentrates (FC), and dust 

formulations may be applied to seeds as a sltmy, a dust, or directly into planter boxes. 

Captan is a member ofN-trihalomethylthio group of compounds which characteristically act on 

the gastrointestinal (GI) tract of mammals. While the thiophosgene moiety may be implicated in 

association with the GI tract tumors, its exact mode of action is unclear. Because of rapid 

detoxification of parent compound and high reactivity of thiophosgene metabolite it is unlikely 

to cause a buildup of these chemicals in the body. The thiophosgene moiety, although short 

lived, can cause irritation at various sites depending upon the route of exposure. 

Captan has low acute oral, dermal, and inhalation toxicity (Toxicity Categories III-IV) with the 

exception of eye irritation, which is Toxicity Category I due to the irritant nature of captan to 

mucus membranes such as the eyes, esophagus, lungs and stomach. 

Page 2 of33 
Captan/081301 Scoping Document

Page 3 of 33

The short term exposure studies with captan, including a 21-day dermal toxicity, a 90-day 

inhalation as well as chronic oral toxicity studies, suggest the possibility that thiophosgene 

causes local irritation of the skin, squamous hyperplasia of larynx or lining of the GI tract 

depending upon the site the thiophosgene comes in contact with. Captan was previously

classified as a B2, "probable human carcinogen" and cancer risk was quantified using the linear

(Q1*) methodology. At the request of the Captan Task Force, EPA’s Cancer Assessment Review 

Committee (CARC) re-evaluated captan in 2004 and changed the cancer classification to "Likely 

to be carcinogenic to humans following prolonged, high-level exposures causing cytotoxicity and 

regenerative cell hyperplasia in the proximal region of the small intestine (oral exposure) or the 

respiratory tract (inhalation exposure), but not likely to be a human carcinogen at dose levels that 

do not cause cytotoxicity and regenerative cell hyperplasia." In addition, captan is "Not likely to 

be carcinogenic to humans via dermal exposure route" due to the very low dermal penetration of

captan. Future quantification of cancer risk will be through a non-linear (RfD) approach since 

there are sufficient data to ascertain the mode of action for the tumor response. 

No qualitative or quantitative susceptibility was seen in the developmental hamster or rabbit 

studies or in the 2-generation reproduction study in rats. The HASPOC recommended, based on 

a WOE approach, that acute and subchronic oral neurotoxicity studies are not required for captan 

at this time (TXR No. 0056559). The FQPA Safety Factor (SF) was reduced to 1X based on the 

completeness of the toxicology and the lack of residual uncertainties for pre/post natal toxicity. 

Therefore, the Reference Dose (RfD) equals the population adjusted dose (PAD).

Previously assessed highly refined (Tier 3) acute, chronic, and cancer dietary exposure analyses 

were performed on food only. At the 99.9th percentile, 36% of the acute Population Adjusted 

Dose (PAD) was used for Females 13-50 years (the only population subgroup identified as 

relevant for the acute dietary endpoint), and less than 2% of the chronic PAD was used for the 

General U.S. Population and all other population subgroups. As noted above, due to the cancer 

re-classification, quantification of dietary cancer risk for any future risk assessments will be 

based on a non-linear risk assessment, and not a Q1* approach as used in the last risk assessment. 

Risks from potential exposure to captan residues of concern in drinking water from all sources 

were evaluated by comparing Estimated Drinking Water Concentrations (EDWCs) against 

calculated drinking water levels of comparison (DWLOCs). The EDWCs for captan residues of 

concern in ground and surface water did not exceed the Agency’s calculated DWLOC values. 

Residential handler exposures were previously assessed in the 1999 Captan RED for the garden 

hose-end sprayer, low pressure handwand, shaker can, solutions mixed in jars for root dip, bulb 

and seed treatment for planting, and a backpack sprayer for turf and home gardens and reevaluated in 2004. Residential turf uses were removed from all captan labels, leaving only 

ornamentals and fruit trees as exposure scenarios for residential handlers. The combined dermal 

and inhalation Margins of Exposures (MOEs) ranged from 240 to over 100,000 and were not of 

concern. Cancer was assessed in the 1999 RED, however, due to the cancer reclassification of 
Captan/081301 Scoping Document

Page 4 of 33

captan, quantification of cancer risk will now be through a non-linear (RfD) approach for all 

exposure scenarios.

In the 1999 Captan RED, residential post-application dermal exposures were assessed for 

ornamentals and turf and then re-evaluated in 2004. For ornamentals, MOEs ranged from 72 at 

Days after Treatment (DAT) 1 to 1,000 at DAT 14. In the 2004 assessment, based on the 

currently registered maximum application rates to turf, MOEs were 20 and 25 for adults and 

toddlers, respectively. Furthermore, the Agency was concerned about toddlers exposed to captan 

through residential uses on lawns, whereas the MOE for toddlers' hand-to-mouth contact from 

residues on low-growing plants was approximately 11. The MOE for toddlers' hand-to-mouth 

contact from residues on turf was 2. To mitigate this risk, the technical registrants agreed to 

voluntarily cancel the use of captan on all turf, except for sod farms and golf courses. Lastly, 

MOEs for dermal exposure in treated gardens ranged from 2,000 to 45,500. 

In the 1999 Captan RED, the acute and chronic dietary (food and drinking water) and cancer 

aggregate risks were not of concern. Residential exposure from the use of captan around the 

home did not exceed the level of concern when aggregated with food and drinking water. Shortterm aggregate risk estimates for dietary and residential uses (ornamental/fruit tree and airless 

paint sprayer) ranged from 330-390, which were not of risk concern. 

Occupational handler exposure was assessed in the 1999 RED using PHED as surrogate 

exposure data, then re-evaluated in 2004. In the 2004 revised assessment, most short- and 

intermediate-term risks to handlers using captan were above 100, with MOEs ranging from 240 

to 43,000. However, mixing/loading wettable powders for aerial applications to typical field 

crops (strawberries) was the most conservative scenario with a MOE of 41. MOEs for 

mixer/loader/applicators and flaggers ranged from 840 to 270,000.

Furthermore, occupational handler exposure during on farm and commercial seed piece 

treatment for multiple activities established MOEs that ranged from 338 to 35,400 for a variety 

of new seed crops including previous assessed crops such alfalfa, cereal grains, cotton, soybeans, 

corn, potatoes, and vegetables. A MOE of 2,400 was calculated for on-farm seed planters. 

Occupational post-application exposure was also addressed in the 1999 Captan RED and in the 

2004 Amendment concerning estimated post-application/reentry exposure for workers entering 

"Terrestrial-Food" crops treated with captan. The Captan Task Force submitted four exposure

Dislodgeable Foliar Residue (DFR) studies represented by MRID numbers 40988601, 40988602 

(strawberries), 40988603, 40985601 (grapes), and 40988604, 40966501 (peach). These crops 

were used as surrogates for all other crops to which captan can be foliar-applied. Occupational 

post-application MOEs ranged from 54 (Grapes: 3 lb ai/acre) to 1,000 (1 lb ai/acre). In the 2004 

revision, post-application exposure to grapes and raspberries was revisited. MOEs ranged from 

90 at DAT 0 for grapes to 400 at DAT 0 for raspberries. 
Captan/081301 Scoping Document

Page 5 of 33

Occupational post-application was also addressed in the 1999 RED concerning estimated postapplication/reentry exposure for workers entering "Terrestrial-Non Food" crops treated with 

captan. For ornamentals and turf, MOEs ranged from 180 to 1,000. In 2004, ornamental post 

application exposure was revisited and MOEs of 400 on DAT 1 were reported. 
Captan/081301 Scoping Document

Page 6 of 33

Introduction

HED has evaluated the most recent human health risk assessments for captan to determine 

whether sufficient data were available and to determine the scope of the work necessary to 

support Registration Review. HED has also considered updates to captan’s toxicity, exposure 

and usage databases, and current Agency science policies and risk assessment methods.

Use Profile

Agricultural Uses: Captan is registered for use on food crops including foliar uses on almonds, 

apples, apricots, blueberries, caneberries (including blackberries, dewberries, and raspberries 

(black, red)), cherries, ginseng (considered non-food use), grapes, nectarines, peaches, pears, 

plums, and strawberries. It is also used as a root dip and as a seed piece and seed treatment for 

numerous crops and as a postharvest fruit dip on apples, cherries and pears. Furthermore, captan 

is used on non food crops including ornamental herbaceous plants; sod farm and golf course

turf; ornamental woody shrubs and vines; ornamental trees; wood structure protection and 

greenhouse soils. 

Captan is applied by via broadcast, chemigation, dust and drip treatment to soil, and as a spot 

application treatment. Furthermore, water dispersible granules (WDG) and liquid flowable 

concentrates (FLC) are used for foliar application to food plants and applied by aerial and ground 

equipment (air blast and ground boom), while field grown ornamentals and golf course turf are 

treated via ground boom equipment. These formulations may also be applied to greenhouse 

ornamentals, fruit (nut trees in home gardens), directly to the soil around plants in greenhouses 

using hand held equipment such as a backpack sprayer; low pressure hand wand, and a garden 

hose-end sprayer. Wettable powders (WP), flowable concentrates (FC), and dust formulations 

may be applied to seeds as a slurry; a dust, or directly into planter boxes. 

The 2004 assessment noted that the Restricted Entry Intervals (REIs) that were to be established 

are: 12- hours for seed treatment uses; 24-hours for strawberries, almonds, apples, apricots, 

cherries, nectarines, plums/fresh prunes, and peaches; 3-days (72-hours) for blueberries, 

raspberries, blackberries, and grapes; 4-days (96-hours) for ornamentals, and 24-hours for soil 

treatments.

Residential Uses: Previous registrations allowed use of captan on ornamentals, and fruit and nut 

trees. Captan was also used on turf (golf courses, athletic fields, and for homeowner use), but in 

the 2004 revised RED, homeowner turf applications were removed from all labels.

Hazard Identification/Toxicology

Captan is a member of N-trihalomethylthio group of compounds (also includes Folpet) which 

characteristically act on the gastrointestinal (GI) tract, lung and other mucous membranes. 

While thiophosgene moiety may be implicated in association with the GI tract tumors, its exact 
Captan/081301 Scoping Document

Page 7 of 33

mode of action is unclear. Because of rapid detoxification of parent compound and high 

reactivity of thiophosgene metabolite, it is unlikely to cause a build-up of these chemicals in the 

body.

In acute toxicity studies, captan is not toxic via the oral route, and has low toxicity via the dermal 

and inhalation routes. Captan is severely irritating to the eyes. 

The thiophosgene moiety, although short lived can cause irritation at various sites depending 

upon the route of exposure to captan. The short term exposure studies with captan, including 21-

day dermal toxicity, 90-day inhalation as well as chronic oral toxicity studies, suggest that 

thiophosgene causes local irritation of the skin, squamous hyperplasia of larynx or lining of the 

gastrointestinal (GI) tract depending upon the site it comes in contact with. Repeated dermal 

application of captan caused dermal irritation but minimal systemic effects such as decrease in 

body weight gain and food consumption. The dermal absorption study in rats indicates that 

captan is minimally absorbed. A dermal absorption rate of 0.4% per hour was determined for 

captan. 

Signs of GI tract disturbance such as emesis were seen in a chronic dietary study with dogs. 

Anorexia and decreased food consumption was reported in pregnant rabbits gavaged with captan. 

In a mouse carcinogenicity study, effects were more severe, consisting of gastric, duodenal and 

jejunal hyperplasia leading to benign and malignant duodenal/jejunum-ileum tumors. The 

incidence of these tumors also increased in a dose-dependent manner. In 1988, EPA classified 

captan as a “B2 - probable human carcinogen” and cancer risk was quantified using the linear 

(Q1*) methodology (TXR Nos. 0050246, 0050247). However, in 2004, the CARC re-classified 

captan as “Likely to be carcinogenic to humans following prolonged, high-level exposures 

causing cytotoxicity and regenerative cell hyperplasia in the proximal region of the small 

intestine (oral exposure) or the respiratory tract (inhalation exposure), but not likely to be a 

human carcinogen at dose levels that do not cause cytotoxicity and regenerative cell 

hyperplasia.” In addition, captan is “Not likely to be carcinogenic to humans via dermal exposure 

route” due to the very low dermal penetration of captan. This decision was based on the 

following weight-of-evidence considerations: (i) The occurrence of adenomas and 

adenocarcinomas in the small intestine of male and female mice; (ii) Captan is not likely to be 

genotoxic in vivo; (iii) The weight-of-evidence suggests that captan induces small intestine 

tumors by a nongenotoxic mode of action involving cytotoxicity and regenerative cell 

hyperplasia that exhibits a clear dose threshold (TXR No. 0052869). Future quantification of 

cancer risk will be through a non-linear (RfD) approach since there are sufficient data to 

ascertain the mode of action for the tumor response. This is different from the linear Q1* 

approach used in the previous risk assessments.

There was no qualitative or quantitative susceptibility seen in the developmental hamster and 

rabbit studies or in the 1- and 3-generation reproduction studies. Studies in hamsters and rabbits 

showed that developmental and reproductive toxicity occurs only at or above doses that cause 
Captan/081301 Scoping Document

Page 8 of 33

toxicity to parental animals. In a prenatal developmental toxicity study in hamster, 

developmental effects including delayed ossification and post-implantation loss occurred at 

doses higher than those that produced decreased body weight gain and mortality in maternal 

animals. In the rabbit developmental toxicity study, increases in skeletal defects (27 pre-sacral 

vertebrae) were noted at the same dose that caused body weight gain and food consumption 

decrements in does. At doses that are toxic to the parent, captan causes decreased pup litter 

weights in a reproduction study. In one- and three-generation reproduction studies in rats, pups 

and parental animals were equally sensitive because body weight decreases were noted in both at 

the same dietary dose levels.

The Agency previously established toxicological endpoints for acute and chronic dietary, as well 

as occupational and residential (dermal and inhalation) exposure risk assessments for captan. 

The developmental toxicity study in rabbits with a developmental NOAEL of 10 mg/kg/day was 

selected for the Acute Dietary endpoint for females 13-50 years old, as well as for the short- and 

intermediate-term dermal endpoints, and for the inhalation endpoints (all durations). This 

endpoint was selected because the observed developmental effects could occur following a single 

exposure, however, since these effects can occur only in utero, they are applicable only to 

females of childbearing age, 13-50 years old. The developmental LOAEL of 30 mg/kg/day was 

based on increased skeletal defects (27 pre-sacral vertebrae) in fetuses. For the Acute dietary 

exposure scenario for females 13-50 years old, the acute PAD was 0.1 mg/kg/day. No separate 

acute dietary endpoint was selected for the general population. The 21-day dermal toxicity study 

in rabbits was not selected for the dermal risk assessments, even though it is the most appropriate 

route of exposure. In this study, repeated dermal application of captan caused dermal irritation, 

but only minimal systemic effects (reductions in body weight, body weight gain, and food 

consumption) at a dermal dose of 1000 mg/kg/day, with a systemic NOAEL of 110 mg/kg/day. 

However, effects on fetuses are not investigated in a guideline 21-day dermal toxicity study. 

Thus, because of the potential for occupational or residential dermal exposure to pregnant 

women, the more conservative NOAEL from the oral developmental toxicity study in rabbits 

was considered appropriate for the short- and intermediate-term dermal risk assessments. Since 

an oral study was selected, a dermal absorption factor of 0.4% was used. A three generation 

reproduction study in rats was selected for the chronic dietary endpoint. The NOAEL in the 

study was 12.5 mg/kg/day based on decreased mean litter weights at the LOAEL of 25 

mg/kg/day. For the chronic dietary exposure scenario, the chronic PAD was 0.13 mg/kg/day.

Toxicity Data Requirements

The toxicology data base is complete, with the exception of immunotoxicity data. In accordance 

with the 2007 revised 40 CFR Part 158 toxicology data requirements, a neurotoxicity battery and 

an immunotoxicity study would be required for captan. However, on January 17, 2012, the 

HASPOC, based on a weight of evidence approach, concluded that the acute and subchronic oral 

neurotoxicity studies are not required for captan at this time (TXR No. 0056559). The HASPOC 

considered all the available hazard and exposure information for captan, including: (1) the lack 
Captan/081301 Scoping Document

Page 9 of 33

of neurotoxicity in the available toxicity studies for captan; (2) the known target organs of captan 

are mucus membranes such as the eyes, esophagus, lungs, and stomach; (3) the points of 

departure (PODs) used for risk assessments are protective of any potential irritation via the oral 

route and it is unlikely that neurotoxicity would be observed at a dose that is lower than the dose 

that causes irritation via the oral route. Therefore, the immunotoxicity study is the only 

outstanding data requirement. OPP has published the findings of an independent retrospective 

analysis1of 170 immunotoxicity studies submitted to the Agency. The retrospective analysis 

suggest that the submitted immunotoxicity studies have not yet resulted in PODs that are lower 

than the PODs selected from other available guideline experimental toxicology studies. As a 

result, the currently available immunotoxicity studies have not impacted the Agency’s risk 

assessments. HED is in the process of developing a guidance document on data waiver 

considerations. In the interim, HED recommends that immunotoxicity studies continue to be 

required for registration and registration review chemicals.

Hazard Conclusions

The toxicology database is adequate for risk assessment. The PODs, endpoints of concern, and 

uncertainty factors for captan may need to be re-evaluated during registration review to ensure 

adherence to current policies and procedures. It is unlikely that an immunotoxicity study will 

yield a POD lower than those used in the existing human health risk assessments.

Residue Chemistry

The residue chemistry database for captan is complete (D258267).

The nature of the residue in plants is adequately understood based on acceptable lettuce and 

tomato metabolism data. Captan is the major residue. Minor residues identified in the plant 

metabolism studies included 1,2,3,6-tetrahydrophthalimide (THPI), captan epoxide, and THPI 

epoxide. Bis(trichloromethyl)disulfide, trans-3-hydroxy-1,2,6-trihydrophthalimide (3-OHTHPI), and trans-5-hydroxy-1,2,6-trihydrophthalimide (5-OH-THPI) may also be present at very 

low levels. The residue of concern in plant commodities for tolerance enforcement is captan 

only. THPI should be included in the acute and non-cancer chronic risk assessments (D258756).

This position may be confirmed by the Residues of Concern Knowledgebase Subcommittee 

(ROCKS) during registration review if needed. 

The nature of the residue in livestock is adequately understood based on acceptable hen and goat 

metabolism data. No captan was detected in tissues, milk, or eggs. The major residues in goat 

muscle, liver, kidney, and milk were 3-OH-THPI and 5-OH-THPI. THPI was the major residue 

in goat fat and hen matrices. The residues of concern in livestock commodities for tolerance 

enforcement and risk assessment are captan and THPI. 

 

1

http://www.epa.gov/pesticides/regulating/immunotoxicity-retro-analysis.pdf
Captan/081301 Scoping Document

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An adequate gas chromatographic (GC)/electron capture detection (ECD) enforcement method is 

available for enforcing tolerances of captan in/on plant commodities and is listed as Method I, in 

PAM, Vol. II. Zeneca Method No. 166 for quantifying THPI in meat and milk has been 

validated for use in tolerance enforcement. Other methods in PAM, Vol. II that use colorimetry 

to determine captan residues are no longer considered suitable for tolerance enforcement. 

Captan is completely recovered using FDA Multiresidue Protocols D (Luke Method; 232.4) and 

E Section 211.1 for oily matrices and partially recovered using FDA Multiresidue Protocol E 

Section 212.1 for non-oily matrices. THPI is completely recovered using FDA Multiresidue 

Protocol D.

Tolerances are established under 40 CFR §180.103(a) for residues of captan (Ntrichloromethylthio-4-cyclohexene-1,2-dicarboximide) in/on almond; almond, hulls; apple; 

apricot; blueberry; caneberry, subgroup 13A; cherry, sweet; cherry, tart; grape; nectarine; peach; 

pear; plum, prune, fresh; and strawberry at 0.25-75.0 ppm to cover residues resulting from foliar 

and/or post-harvest uses and in/on numerous other raw agricultural commodities at 0.05 ppm to 

cover residues resulting from seed treatment uses. All the commodities and their respective 

tolerances are listed in the Appendix. Tolerances are established under 40 CFR §180.103(b) for 

residues of captan (N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide) and its metabolite 

1,2,3,6-tetrahydrophthalimide (THPI) in ruminant tissues at 0.15-0.30 ppm and in milk at 0.10 

ppm. Since there is no reasonable expectation of finite residues of concern in poultry and eggs, 

no tolerances for captan residues of concern have been established in these commodities. The 

tolerance expression will need to be updated in accordance with current policy. 

Residue Chemistry Conclusions 

The residue chemistry database is complete. The qualitative nature of captan residues in the 

registered crops and livestock is adequately understood based on acceptable metabolism studies. 

The residue of concern in plant commodities for tolerance enforcement is captan only. The 

residues of concern in livestock commodities for tolerance enforcement and risk assessment are 

captan and 1,2,3,6-tetrahydrophthalimide (THPI). The captan tolerance expression will need to 

be updated in accordance with current policy. Adequate analytical enforcement methods are 

available. The combined residues of captan and are considered the total residue of concern for 

the purposes of acute and chronic non-cancer dietary risk assessments; this position may be 

confirmed by the Residues of Concern Knowledgebase Subcommittee (ROCKS) during 

registration review if needed. 

Dietary Exposure and Risk

The combined residues of captan and 1,2,3,6-tetrahydrophthalimide (THPI) are considered the

total residue of concern for the purposes of acute and chronic non-cancer dietary risk 

assessments (D258756 and 1999 Captan RED). This position may be confirmed by the Residues 

of Concern Knowledgebase Subcommittee (ROCKS) during registration review if needed. 
Captan/081301 Scoping Document

Page 11 of 33

For the purposes of chronic cancer dietary risk assessment, only captan is considered since the 

carcinogenicity of captan is believed to be associated with the reactive thiophosgene moiety. 

The CARC re-evaluated Captan in 2004 (TXR No. 0052869). Based on the new classification, 

future quantification of cancer risk will be through a non-linear (RfD) approach since there are 

sufficient data to ascertain the mode of action for the tumor response. This is different from the 

linear Q1* approach used in the previous risk assessments.

Dietary Risk 

The most recent dietary exposure assessments (D252405 and D259452) used the Dietary 

Exposure Evaluation Model (DEEMTM) software and consumption data from USDA’s 

Continuing Surveys of Food Intakes by Individuals (CSFII), 1989-92. This dietary exposure 

assessment evaluated captan residues of concern in food but not drinking water. 

Highly refined (Tier 3) acute (D252404) and chronic cancer and non-cancer (D259452) dietary 

exposure analyses were performed on food only. Anticipated residue estimates were based on 

field trial or monitoring data. Processing, washing, and cooking data to estimate 

reduction/concentration factors and percent crop treated data were also used when available. At 

the 99.9th percentile, 36% of the acute Population Adjusted Dose (PAD) was used for Females 

13-50 years (the only population subgroup identified as relevant for the acute dietary endpoint), 

and less than 2% of the chronic PAD was used for the General U.S. Population and all other 

population subgroups. Dietary cancer risk from captan was 1.3x10-7based on the Q1

*

for captan 

of 2.4 x 10-3(mg/kg/day)-1. 

Drinking Water

Captan is expected to degrade relatively rapidly in the environment. However, there is a potential 

for the degradate THPI to reach ground and surface water due to application rates and multiple 

applications of captan. Risks from potential exposure to captan residues of concern in drinking 

water from all sources was comprehensively discussed in the 1999 Captan RED and risks were 

evaluated by comparing Estimated Drinking Water Concentrations (EDWCs) against calculated 

drinking water levels of comparison (DWLOCs). 

The potential groundwater and surface water exposures to captan and THPI were assessed based 

on Tier 1 and Tier 2 models, respectively, which provide computer-generated EDWCs. The 

assessment in the 1999 Captan RED indicated that the EDWCs for captan residues of concern in 

ground and surface water did not exceed the Agency’s calculated DWLOC values. [Note: 

Surface drinking water estimates used in the acute and chronic non-cancer dietary risk 

assessments in the 1999 Captan RED only included residue values for THPI but should have 

included residue values for captan as well. However, the combined EDWCs for captan plus 

THPI in surface water do not exceed the DWLOC values in the 1999 Captan RED.] The Agency 

no longer relies on DWLOCs and drinking water estimates may need to be updated for the 

dietary assessment. 
Captan/081301 Scoping Document

Page 12 of 33

Dietary Exposure and Risk Conclusions 

HED has previously assessed dietary exposures and risks from these exposures were below the 

Agency’s level of concern. New acute and chronic dietary risk assessments may need to be 

conducted using the newest version of the Dietary Exposure Evaluation Model DEEM-FCIDTM, 

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) and incorporate potential changes to the captan toxicological points of departure 

(PODs) and uncertainty factors. If new dietary risk assessments are conducted under registration 

review, updated percent crop treated data may be needed for dietary risk refinements. Since 

CARC re-evaluated Captan in 2004 (TXR No. 0052869) and captan has a new classification, 

future quantification of cancer risk will be through a non-linear (RfD) approach since there are 

sufficient data to ascertain the mode of action for the tumor response. This is different from the 

linear Q1* approach used in the previous risk assessments. The Agency no longer relies on 

DWLOCs and drinking water estimates may need to be incorporated directly into the dietary 

assessments. 

The most recent drinking water estimates are adequate based on current methodologies but may 

need to be revised. EFED may wish to generate a single comprehensive drinking water 

assessment under registration review for the purposes of documentation. Surface drinking water 

estimates used in the most recent acute and chronic dietary risk assessments only included 

residue values for THPI (1999 Captan RED) but should have included residue values for captan 

as well. This should be corrected in the registration review risk assessment. [Note: The 

combined EDWCs for captan plus THPI in surface water do not exceed the Agency’s calculated 

DWLOC values.] 

Occupational and Residential Exposure

Occupational handler exposure was assessed in the 1999 RED using PHED as surrogate 

exposure data, and then re-evaluated in 2004 (D305649). The exposure scenarios that were 

assessed are as follows: aerial; groundboom; airblast; high pressure sprayer; low pressure 

handwand; commercial hose-end and backpack sprayers; and seed and seed piece treatment. 

Furthermore, a post-harvest dip assessment was conducted for apples, cherries, and pears as 

well. Although exposure to commercial painters applying paints containing captan was 

estimated for the RED, these products have since been removed from the market.

The most recent human health risk assessment for captan was a 2004 amendment to the 1999 

Captan RED document (EPA 738-R-99-015) in support of a petition for the domestic use of 

captan on various agricultural crops and non agricultural crops; including seed treatment and 

residential gardens. Residential turf applications were removed from all labels.
Captan/081301 Scoping Document

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Occupational Handler Results

In the 2004 revised assessment, most short- and intermediate-term risks to handlers using captan 

were above 100, the level of concern, with MOEs ranging from 240 to 43,000. However,

mixing/loading wettable powders for aerial applications to typical field crops (strawberries) was 

the most conservative scenario with a MOE of 41. MOEs for mixer/loader/applicators and 

flaggers ranged from 840 to 270,000. A cancer assessment was conducted in the 1999 RED, 

however in 2004, as stated above, due the cancer reclassification of captan, quantification of 

cancer risk will now be through a non-linear (RfD) approach.

According to the Guidance for Requiring/Waiving Turf Transferable Residue (TTR) and 

Dislodgeable Foliar Residue (DFR) Studies (Housenger, 2012), a calculated MOE of 

approximately 10 time higher than the level of concern (e.g., an MOE > 1,000 if the LOC = 100) 

using the default residue transfer values should provide an adequate margin of safety for any 

potentially higher residues seen in a chemical specific TTR study. In the case of captan, mixing 

and loading for sod farm use registers a combined MOE of 90, for single layer clothing, gloves 

and a PF5 dust-mist respirator, which is the label specific Personal Protective Equipment (PPE).

Therefore, a TTR study will be needed for turf exposure uses.

PPE for captan applications was established on existing labels as; coveralls, chemical resistant 

glove, shoes plus socks, and protective eyewear, and a dust mist respirator for wettable powder 

and dust formulations.

Occupational Handler: Seed and Seed Piece treatment

According to the 2004 Amendment to the 1999 Captan RED, occupational handler exposure 

during on farm and commercial seed piece treatment for multiple activities established MOEs 

that ranged from 338 to 35,400 for a variety of seed crops, including alfalfa, cereal grains, 

cotton, soybeans, corn, potatoes, and vegetables. A MOE of 2,400 was calculated for on-farm 

seed planters. 

A cancer assessment was conducted in the 1999 Captan RED and the 2004 Amendment using 

the Q1* approach. However, the CARC re-evaluated captan and changed the cancer classification 

as discussed in the toxicity section. Quantification of cancer risk will now be through a nonlinear RfD approach since there are sufficient data to ascertain the mode of action for the tumor 

response.

Occupational Post-Application for Food Crops:

In the 1999 RED and the 2004 Amendment to the RED, to address estimated postapplication/reentry exposure for workers entering crops treated with captan, the Captan Task 

Force submitted four DFR exposure studies represented by MRID numbers 40988601,
Captan/081301 Scoping Document

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40988602 (strawberries), 40988603, 40985601 (grapes), and 40988604, 40966501 (peach). The 

Captan Task Force used application rates that ranged from (1 lb ai/acre) to (3 lbs ai/acre). These 

three crops were used as surrogates for all other crops to which captan can be foliar-applied. 

Post-application MOEs ranged from 57 at DAT 0 (Grapes: 3 lb ai/acre) to 1,000 at DAT 14

(Strawberries: 1 lb ai/acre). 

The post-application MOEs were revisited for ornamentals, berries and grapes (D305649). The 

MOEs ranged from 90 at “DAT 0” for grapes to 400 at "DAT 0 for berries." 

Occupational Post-Application for Non-Food Crops:

Occupational post-application exposure was also addressed in the 1999 RED and supporting 

documents (D222418, D226527) concerning estimated post-application/reentry exposure for 

workers entering "Terrestrial-Non Food" crops treated with captan. EPA assessed spray 

applications to azaleas; begonias; camellias; carnations; chrysanthemums; conifers; dichondra; 

gladiolus; grasses (lawns and lawn seedbeds); ornamental flowering plants, and roses. To 

calculate risk for workers harvesting and bundling flowers, EPA used DFR data from the Task 

Force's Strawberry DFR study (MRID 409886-01) and transfer coefficients developed in the 

Netherlands (Brouwer et al. 1983). Margin of Exposures (MOEs) for occupational postapplication exposure to ornamentals and turf ranged from 180 at DAT 1 to 1,000 at DAT 14.

In the 1999 RED, a 48-hour restricted-entry interval was established for captan, since the active 

ingredient is classified as toxicity category I for eye irritation potential. 

The 2004 assessment noted the REIs that were established: 12- hours for seed treatment uses; 24-

hours for strawberries, almonds, apples, apricots, cherries, nectarines, plums/fresh prunes, and 

peaches; 3-days (72-hours) for blueberries, raspberries, blackberries, and grapes; 4-days (96-

hours) for ornamentals, and 24-hours for soil treatments.

A quantitative post-application inhalation exposure assessment was not performed for captan. 

However, there are multiple potential sources of post-application inhalation exposure to 

individuals performing various activities in previously treated fields. These potential sources 

include volatilization of pesticides and resuspension of dusts and/or particulates that contain 

pesticides. The Agency sought expert advice and input on issues related to volatilization of 

pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel 

(SAP) in December 2009, and received the SAP’s final report on March 2, 2010 

(http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html). The Agency is 

currently evaluating the SAP report. EPA is also evaluating the available post-application 

inhalation exposure data generated by the Agricultural Reentry Task Force and may, as 

appropriate, develop policies and procedures to identify the need for and, subsequently, the way 

to incorporate occupational post-application inhalation exposure into the Agency's risk 
Captan/081301 Scoping Document

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assessments. If new policies or procedures are put into place, the Agency may revisit the need 

for a quantitative occupational post-application inhalation exposure assessment for captan.

Residential Handler:

In the 2004 revision to the 1999 RED, residential turf applications were removed leaving only 

ornamentals and fruit trees as exposure scenarios. The combined dermal and inhalation MOEs 

ranged from 240 to over 100,000 and were not of concern.

Residential Post-application:

Ornamentals: Residential post-application exposures were previously assessed in the 1999 RED 

for ornamentals and turf. For ornamentals, MOEs ranged from 72 at DAT 0 to 1,000 at DAT 14 

and were not of concern. 

Turf: In the 2004 assessment; based on the currently registered maximum application rates to 

turf, MOEs were 20 and 25 for adults and toddlers, respectively. Furthermore, the Agency was 

concerned about toddlers exposed to captan through residential uses on lawns. The MOE for 

toddlers' hand-to-mouth contact from residues on low-growing plants was approximately 11. 

The MOE for toddlers' hand-to-mouth contact from residues on turf is 2. To mitigate this use, 

the technical registrants agreed to voluntarily cancel the use of captan on all turf, except for sod 

farms and golf courses.

Spray Drift: Residential exposures resulting from off-site transport (e.g., spray drift or 

volatilization) may occur as a result of applications for captan. The Agency is in the process of 

evaluating these types of exposures and will examine the need for spray drift and volatilization 

assessments for captan during registration review

Conclusions for Residential and Occupational Exposure

Due to recent residential and occupational exposure science policy updates, existing residential 

and occupational scenarios may have to be reassessed. These updates include changes to data 

sources and default assessment inputs for both handler and post-application assessments. In 

addition, the assessment may need to be updated to reflect the carcinogenicity reclassification 

and any potential changes to the PODs and uncertainty factors for captan. 

Aggregate Exposure and Risk

In the 1999 Captan RED, the acute and chronic dietary (food and drinking water) and cancer 

aggregate risks were not of concern. Residential exposure from the use of captan around the 

home did not exceed the level of concern when aggregated with food and drinking water. Shortterm non-cancer aggregate risk estimates for dietary and residential uses (ornamental/fruit tree 

and airless paint sprayer) ranged from MOEs of 330-390, which were not of risk concern. 
Captan/081301 Scoping Document

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Based on a shared common metabolite, thiophosgene, and a cancer concern through the oral 

route, an aggregate cancer assessment was also conducted for combined dietary exposures to 

captan and folpet through the oral route. The aggregate exposure from folpet and captan residues 

in food and water did not exceed the EPA’s level of concern for cancer risk for the U.S. 

population.

Public Health and Pesticide Epidemiology Data

Based on the low frequency and severity of incident cases reported for captan in both the OPP 

Incident Data Systems (IDS) and Centers for Disease Control and Prevention/National Institute 

for Occupational Safety and Health (CDC/NIOSH) Sentinel Event Notification System for 

Occupational Risk-Pesticides (SENSOR) databases, there does not appear to be a concern at this 

time that would warrant further investigation (D409190). The Agency will continue to monitor 

the incident information and if a concern is triggered, additional analysis will be included in the 

risk assessment. In addition, EPA will continue to review the literature regarding evidence of the 

carcinogenic potential of captan in the Agricultural Health Study (AHS) cohort.

Tolerances and International Harmonization

The U.S., CODEX, and Canadian residue definitions for captan in/on plant commodities are 

harmonized. The U.S. has established tolerances in livestock commodities but there are no 

CODEX or Canadian MRLs established in any livestock commodity. Mexico adopts U.S. 

tolerances and/or Codex MRLs for export purposes.

U.S. tolerance levels are not fully harmonized with CODEX and may need to be reassessed. (See 

International Residue Limits table in the Appendix). Only the captan tolerances and CODEX 

MRLs for blueberry, grape, plum, and potato (U.S. tolerance in/on Vegetable, root and tuber, 

group 1) are currently harmonized. None of the U.S. tolerances and Canadian MRLs are 

currently harmonized.

Endocrine Disruption

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. As part of its reregistration decision, EPA reviewed these data and selected 

the most sensitive endpoints for relevant risk assessment scenarios from the existing hazard 
Captan/081301 Scoping Document

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database. However, as required by FFDCA section 408(p), captan is subject to the endocrine 

screening part of the Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between October 

2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 chemicals, 

which contains 58 pesticide active ingredients and 9 inert ingredients. Captan was included on 

that list and has been issued an order to conduct the Tier 1 testing. Once all required Tier 1 and 

Tier 2 data have been received and reviewed, the endpoints and safety factors used for risk 

assessment purposes will be examined and a new risk assessment performed if necessary. For 

further information on the status of the EDSP, the policies and procedures, the list of 67 

chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our 

website: http://www.epa.gov/endo/. 

Cumulative

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

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

as to captan or any other substances. Although folpet and captan share the common metabolite 

thiophosgene, its role in folpet’s and captan’s toxicity has not been determined because 

thiophosgene is transient and not easily measurable. Therefore, the EPA has not assumed that 

captan has a common mechanism of toxicity with captan or any 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 policy statements 

released by EPA’s OPP 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/.
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Human Studies 

This risk assessment relies in part on data from studies in which adult human subjects were 

intentionally exposed to a pesticide or other chemical. These data, which include studies from 

Standard Operating Procedures (SOPs) for Seed Treatment, Policy 14, 15, and 15.1 are (1) 

subject to ethics review pursuant to 40 CFR 26, (2) have received that review, and (3) are 

compliant with applicable ethics requirements. For certain studies, the ethics review may have 

included review by the Human Studies Review Board. Descriptions of data sources, as well as 

guidance on their use, can be found at http://www.epa.gov/pesticides/science/handler-exposuredata.html and http://www.epa.gov/pesticides/science/post-app-exposure-data.html.

Environmental Justice

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

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.hss.energy.gov/nuclearsafety/env/guidance/justice/eo12898.pdf). OPP typically 

considers the highest potential exposures from the legal use of a pesticide when conducting 

human-health risk assessments, including, but not limited to, people who obtain drinking water 

from sources near agricultural areas, the variability of diets within the U.S., and people who 

might be exposed when harvesting crops. Should these highest exposures indicate potential risks 

of concern, OPP further refines the risk assessments to ensure that the risk estimates are based on 

the best available information.

Data Requirements

Toxicology:

Guideline 870.7800 Immunotoxicity

Residue Chemistry:

No data requirements.

Occupational Exposure (ORE):

Turf Transferable Residue (TTR) data (Guideline 875.2100). 

Residential Exposure (ORE):

No data requirements.
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Risk Assessment Updates Required Under Registration Review

Hazard Conclusions:

The toxicology database is adequate for risk assessment. The PODs, endpoints of concern 

and uncertainty factors may need to be re-evaluated during registration review to ensure 

adherence to current policies and procedures. It is unlikely that an immunotoxicity study 

will yield a POD lower than those used in the existing human health risk assessments.

Dietary and Drinking Water Exposure and Risk: 

New acute and chronic dietary risk assessments may be needed if there are changes to 

the captan toxicological PODs, uncertainty factors, or drinking water assessment. The 

assessment may need to be updated to reflect the carcinogenicity reclassification. If new 

dietary risk assessments are conducted under registration review, updated percent crop 

treated data may be needed for dietary risk refinements.

Surface drinking water estimates used in the most recent acute and chronic non-cancer 

dietary risk assessments only included residue values for THPI (1999 Captan RED) but 

should have included the estimated residue values for captan as well. This should be 

corrected in the registration review risk assessment. [Note: The combined EDWCs for 

captan plus THPI in surface water did not exceed the Agency’s calculated DWLOC 

values.] 

Residue Chemistry:

 The tolerance expression will need to be updated in accordance with current policy. 

 The combined residues of captan and THPI are considered the total residue of concern for 

the purposes of acute and chronic non-cancer dietary risk assessments; this position may 

be confirmed by the Residues of Concern Knowledgebase Subcommittee (ROCKS) 

during registration review if needed. 

Tolerances and International Harmonization:

 U.S. tolerance levels are not fully harmonized and may need to be reassessed for CODEX 

harmonization.

Occupational and Residential Exposure (ORE) and Risk:

The residential and occupational exposure assessments may need to be updated to reflect

current SOPs and to incorporate any new endpoints or uncertainty factors selected based 

on the required toxicity and ORE studies. 
Captan/081301 Scoping Document

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References

1986. Engler, R. Peer Review of Captan, Caswell No. 159. 12/29/1986. TXR No. 0050246.

1987. Garbus, J. Product Chemistry Registration Standard. 2/2/87.

1988. Rinde, E. Peer Review (2nd) of Captan, Addendum. July 20, 1988. TXR No. 0050247.

1996. Mostaghimi, S. Recalculation of Captan EEC’s for Almonds, Apple, Peaches, Prunes, 

Cherries and Blueberries. 6/28/96. D210410.

1997. Burnam, W. Captan Q1* Revisited. 10/6/1997. TXR No. 0051523.

1997. Evans, J. Revised Occupational and Residential Exposure Assessment for the Captan 

Reregistration Eligibility Decision (RED). D222418, D226527.

1999. Maher. EFED’s revisions to the EFED Captan RED chapter. 4/23/99. D253634.

1999. Piper, S. Reregistration Case No 0120. Tier 3 (Monte Carlo) Acute Dietary Exposure 

Estimates for Captan. 5/3/99. D252405.

1999. Morton, T. Reregistration Case No 0120. Product and Residue Chemistry Chapters for 

the Captan Reregistration Eligibility Decision (RED). 8/3/99. D258267.

1999. Hrdy, D. Captan (N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide): HED Risk 

Assessment for the Registration Eligibility Decision (RED) Document. 8/11/99. D258756.

1999. Hrdy, D. Reregistration Case No 0120. Tier 3 Chronic Cancer and Non-Cancer Dietary 

Exposure Estimates for Captan. 9/23/99. D259452.

1999. Captan Reregistration Eligibility Decision (RED). November, 1999.

2004. Captan: Fourth Report of the Cancer Assessment Review Committee. 9/22/04. TXR No. 

0052869.

2004. Amendment to the 1999 Captan RED. 11/1/04.

2004. Hrdy, D. Captan (N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide): HED 

Revisions to the Occupational Risk Assessment for the Reregistration Eligibility Decision (RED) 

Document. Chemical No. 081301. Case No. 0120. D305649.
Captan/081301 Scoping Document

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2012. Housenger, J. Guidance for Requiring/Waiving Turf Transferable Residue (TTR) and 

Dislodgeable Foliar Residue (DFR) Studies. 12/12/12.

2013. Van Alstine, J. Captan: Summary of Hazard and Science Policy Council (HASPOC)

Meeting of January 17, 2013: Recommendations on the Need for Acute and Subchronic 

Neurotoxicity Studies and an Immunotoxicity Study. March 20, 2013.

TXR No.0056559.

2013. Recore, S. Captan: Review of Human Incidents. 2/20/13. D409190.
Captan/081301 Scoping Document

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APPENDIX

Table 1. Summary of Doses and Endpoints Selected for Captan Risk Assessments

*This is not a dermal absorption factor but a dermal absorption rate and should be re-evaluated in 

registration review.

Exposure

Scenario

Dose

(mg/kg/day) Endpoint Study

Acute Dietary

Female 13+

NOAEL=10

UF = 100

FQPA = 1

30 mg/kg/day based on increased 

skeletal defects (27 pre-sacral 

vertebrae) in fetuses. Applies to 

females 13+ only; no appropriate 

endpoint for general population.

Developmental 

Toxicity Study in 

Rabbits

Acute RfD=aPAD = 0.1 mg/kg/day

Chronic Dietary NOAEL=12.5

UF = 100

FQPA = 1

25 mg/kg/day based on decreased pup 

body weight

One- and threegeneration repro 

Studies-Rat

Chronic RfD = cPAD = 0.13 mg/kg/day

Correction for oral to dermal exposure necessary (0.4% per hour; dermal absorption factor)*

Short- and 

Intermediate-Term 

(Dermal)

Oral

NOAEL=10

UF = 100

30 mg/kg/day based on increased 

skeletal defects (27 pre-sacral 

vertebrae)

Developmental 

Toxicity Study in 

Rabbits

Long-Term (Dermal) None Use pattern and exposure indicate no 

need for long-term risk assessment

Use 100% lung absorption relative to oral absorption

All Durations

(Inhalation)

Oral

NOAEL=10

UF = 100

30 mg/kg/day based on increased 

skeletal defects (27 pre-sacral 

vertebrae)

Developmental 

Toxicity Study in 

Rabbits

* -3 Based on findings of intestinal tumors 

in mice

Mouse

Oncogenicity
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a. Acute Toxicity

Acute toxicity values and categories for captan are summarized in the following table.

Table 2. Overview of Acute Toxicity

Guideline Test MRID Results Category

870.1100 Acute Oral Toxicity -

Rat

00054789** LD50 = 9 g/kg (M) IV

870.1200

Acute Dermal Toxicity -

rat

40021401** LD50 > 2 g/kg III

870.1300

Acute Inhalation 

Toxicity- rat

00148070** LC50 = 0.72 mg/L (M) 

LC50 = 0.87 mg/L (F) III

870.2400* Primary Eye Irritation -

rabbit

00128621 Irreversible corneal opacity

at 21 days in unwashed eyes

I

870.2500*

Primary Dermal

Irritation - rabbit 40021401 Not an irritant at 3 days IV

870.2600*

Dermal Sensitization

- guinea pig 00054791 Moderate skin sensitizer N/A

*Data pertaining to acute eye irritation, dermal irritation, and dermal sensitization are not

required to support reregistration of the active ingredient. Data are presented for information purposes.

 ** The acute toxicity endpoints, listed above, are for informational purposes only. The data supporting these 

endpoints do not meet current acceptability criteria. The acceptability status of these data may be reassessed

during product reregistration.

b. Subchronic and Chronic Toxicity 

The available subchronic and chronic toxicity data for captan are summarized below. 

21-Day Dermal Toxicity: In a 21-day dermal toxicity study, New Zealand White rabbits were 

exposed to Captan at doses of 0, 12.5, 110 or 1000 mg/kg/day. The NOAEL for systemic 

toxicity was 110 mg/kg/day and the LOAEL for systemic toxicity was 1000 mg/kg/day, based on 

reduced body weight, body weight gain and food consumption. The NOAEL for dermal 

irritation was less than 12.5 mg/kg/day, the lowest dose tested (LDT). The LOAEL for dermal 

irritation was equal to or less than 12.5 mg/kg/day, based on acanthosis and hyperkeratosis. This 
Captan/081301 Scoping Document

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study satisfies the guideline toxicological data requirement for a 21-day dermal toxicity study in 

rabbits (MRID 40273201).

90-Day Inhalation Rat: In a 90-day inhalation toxicity study, Wistar rats were exposed (nose 

only) to Captan (88.7%) at 0, 0.13, 0.60, 5.06, or 12.98 μg/L for 13 weeks (6 hrs/day, 5 

days/week). No systemic toxicity was seen at the highest dose tested. Therefore, the 

NOAEL/LOAEL were greater than 12.98 μg/L, the highest dose tested (HDT). Local irritation 

was observed at all doses tested. The local irritation LOAEL was equal to or less than 0.13 μg/L 

(LDT), based on squamous hyperplasia in the larynx of females. This study satisfies the 

toxicological guideline data requirement for a 90-day inhalation toxicity study in rats (MRID 

41234402).

Oncogenicity Rat (MRIDs 00120316, 00129157, 00129163, 00129164, 00153207):

Two carcinogenicity studies were performed on rats. In the first study, a chronic/carcinogenicity 

feeding study, Charles River CD strain rats (70/sex/group) were fed diets containing 0, 500, 2000 

or 5000 ppm Captan (0, 25, 100 or 250 mg/kg/day) for 2 years. The NOAEL for systemic 

effects was 25 mg/kg/day. The LOAEL of 100 mg/kg/day was based on hepatocellular 

hypertrophy (males); increased relative organ weight for kidneys (males and females), increased 

relative organ weight for heart, brain, liver and thyroid/parathyroid (males) and decreased body 

weight for males (12%) and females (19%) when compared to controls. The Cancer Peer 

Review document dated 12/29/86 indicated that the maximum tolerated dose (MTD) was 

apparently exceeded at 100 mg/kg/day based on decreased body weight. There was a significant 

increasing trend in males for the combined adenomas and carcinomas of the kidney in male rats. 

The percent incidence of combined adenomas and carcinomas of the kidney was 1, 1, 4, and 6% 

for 0, 25, 100 and 250 mg/kg/day groups, respectively. There was no increased incidence of 

renal cortical/tubular cell neoplasia in females.

In the second study, a carcinogenicity feeding study, Wistar rats (50/sex/group) were fed diets 

containing 0, 125, 500 or 2000 ppm Captan (0, 6.25, 24 or 98 mg/kg/day) for 30 months. The 

NOAEL/LOAEL for systemic toxicity were equal to or greater than 2000 ppm (HDT). There 

was no increase in the incidence of renal cortical/tubular cell neoplasms. There was a slight but 

statistically significant increase in uterine sarcomas (4/50 vs 0/48 in controls) in the high dose 

group [The MTD was apparently approached at the high dose (10% body weight decrease).] 

The above studies, when combined, satisfy the toxicological data requirement for a 

chronic/carcinogenicity feeding study in rats.

Oncogenicity Mouse (NCI Technical Report No. 15 & MRIDs 00068076 & 00126845):

Three carcinogenicity studies were performed on mice. In the first one B6C3F1 mice 

(50/sex/treated group; 10/sex/matched controls; 65/sex for pooled controls), mice were fed diets 

containing 0, 6,000 and 16,000 ppm Captan (0, 900, and 2,400 mg/kg/day) for 80 weeks 

followed by no treatment for 33 weeks. The NOAEL for systemic toxicity was 6000 ppm and 

the LOAEL for systemic toxicity was 16,000 ppm based on decreased mean body weight from 
Captan/081301 Scoping Document

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the matched controls (about 10% less in both sexes). There was no treatment related increase in 

mortality and the MTD was apparently approached at 16,000 ppm. Male and female mice had an 

increased incidence in combined duodenal adenoma/polyps or adenocarcinomas at the 16,000 

ppm level, with the first reported tumor at 91 weeks. A positive linear trend in males (p=0.08) 

and the Fisher exact test in high-dosed males gave a probability level of 0.009. There was a 

minimal increase in hyperplasia of the duodenal mucosa noted in the high dose males (National 

Cancer Institute, 1977. Bioassay of Captan for Possible Carcinogenicity. Technical Report 

Series No. 15).

In a second study, ICR derived CD-1 Charles River mice (80/sex/group) were initially fed diets 

containing 0, 2,000, 6,000 or 10,000 ppm of Captan for 4 weeks. Subsequently Captan 

concentrations were increased to 0, 6000, 10,000 or 16,000 ppm (900, 1,500 or 2,400 mg/kg/day 

for females and at 900, 1,000 or 2,400 mg/kg/day for males) for the remainder of the study. The 

NOAEL for systemic toxicity was not established. The LOAEL for systemic toxicity was 6000 

ppm, the lowest dose tested, based on decreased body weight gain and food consumption (no 

quantitative information was available). Both high dose males and females weighed 25% less 

than controls. In high dose males and females, the mortality was higher, suggesting that the 

MTD was exceeded. At week 75, the survival in males was 68% (high-dose), 75% (mid-dose), 

79% (low-dose) and 83% (controls). There was an increased (p<0.001) incidence of small 

intestinal (primarily duodenal) adenomas/polyps and carcinomas at all dose levels. The 

incidences of duodenal tumors for males and females, respectively, were 2.7% and 2.8% 

(control), 27% and 31% (low-dose), 29% and 25% (mid-dose), and 52% and 38% (high-dose). 

A positive dose-related trend for an increased incidence of duodenal tumors in both sexes 

(p<0.005) was also observed. Proliferative duodenal changes appeared to occur earlier in the 

high dose males. There was also a statistically significant increase in gastric and duodenal 

hyperplasia in both sexes and in jejunal hyperplasia in females. Stomach neoplasia were not 

reported. This study satisfies the toxicological data requirement for a carcinogenicity study [83-

2 (b)] in mice (MRID 00068076).

In a third study, Charles River CD-1 mice (100/sex/group) were fed diets containing 0, 100, 400, 

800 or 6,000 ppm Captan (0, 15, 60, 120, or 900 mg/kg/day) and the study was terminated at 22 

months due to increased mortality in the high dose males. The survival in males was 15% (highdose) and 36% (controls) at week 75 and 7% (high-dose) and 25% (controls) at 22 months. The 

NOAEL for systemic toxicity was 800 ppm and the LOAEL for systemic toxicity was 6000 ppm 

based on increased mortality in males and reduced weight gain throughout the study (males and 

females). There was a small increase in small intestinal tumors (benign and malignant) in the 

male (6%) and female (8%) high dose groups (controls = 0%). The results of an Agency audit of 

this study suggested that there was a problem with achieving and maintaining the appropriate 

dose levels throughout the study. (MRID 00126845).

Chronic Toxicity Non-Rodent: In a chronic toxicity feeding study in non-rodents, Beagle dogs 

were dosed with Captan at doses of 0, 12.5, 60 or 300 mg/kg/day in capsules daily for one year. 
Captan/081301 Scoping Document

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The NOAEL for systemic toxicity was 60 mg/kg/day and the LOAEL was 300 mg/kg/day, based 

on emesis and soft/mucoid stools. This guideline study satisfies the toxicological data 

requirement for a chronic feeding study in non-rodents (MRID 40893604). 

c. Developmental and Reproductive Toxicity 

Developmental Toxicity in Rabbits (MRID 41826901): A developmental toxicity study was 

conducted with New Zealand White rabbits (20 rabbits/group). Captan was administered by oral 

gavage at doses of 0, 3, 10, 30 or 100 mg/kg/day from gestation days 7 through 19. The 

maternal NOAEL was 10 mg/kg/day and the maternal LOAEL was 30 mg/kg/day, based on 

reduced body weight gain, decreased food consumption, and anorexia in the does. The 

developmental NOAEL was 10 mg/kg/day and the developmental LOAEL was 30 mg/kg/day, 

based on increased incidence of skeletal defects (27 pre-sacral vertebrae) (p < 0.01) in both 

fetuses and litters at 30 and 100 mg/kg/day. In addition, there was increased post-implantation 

loss (p <0.01), reduced mean fetal weight (p < 0.05) and increased manus score (altered growth) 

(p < 0.01) at 100 mg/kg/day. This study satisfies the guideline data requirement for a 

developmental toxicity study (83-3) in rabbits.

One- and Three-generation Reproductive Studies in Rats (MRIDs 00120315 and 00125293):

One-Generation Reproduction Rat: Captan was administered in the diet at dose levels of 0, 6, 

12.5 or 25 mg/kg/day to male and female COBS CD rats. For this study, 15 males were mated 

with 30 females. No compound related effects were seen. This study by itself does not satisfy 

Subdivision F guidelines because it is only a one-generation reproduction study (MRID 

00120315). 

Three-Generation Reproduction Rat: In the three-generation study, the dose levels tested were 0, 

25, 100, 250 or 500 mg/kg/day. For this study, 15 male COBS CD rats were mated with 30 

females. Maternal toxicity NOAEL/LOAEL were considered to be 12.5 and 25 mg/kg/day based 

on decreased body weight gain and food consumption. Reproductive toxicity NOAEL/LOAEL 

were considered to be 12.5 and 25 mg/kg/day based on decreased pup litter weights. Pup 

survival was reduced at 250 mg/kg/day or higher (MRID 00125293).

These two studies, when considered together, satisfy the toxicological guideline data requirement 

for a reproductive toxicity study in rats. The endpoints selected are based on the NOAEL of 12.5 

mg/kg/day with decreased mean litter weights observed at the next higher dose level of 25 

mg/kg/day. The one- and three generation studies are acceptable together and the two studies 

also show that pups and parents are equally sensitive.
Captan/081301 Scoping Document

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Teratogenicity Rodent: Another developmental toxicity study was conducted with Golden Syrian 

hamsters (30/group). Hamsters were treated by oral intubation on days 5 through 10 of gestation 

with 0, 50, 200 or 400 mg/kg/day of Captan. The maternal NOAEL/LOAEL were considered to be 

50 and 200 mg/kg/day based upon reduced body weight gain and increased mortality. The 

developmental NOAEL/LOAEL were considered to be 200 and 400 mg/kg/day based upon 

increased incidences of delayed ossification, decreased weight and increased resorptions. This study 

satisfies the guideline data requirement for a developmental toxicity study (83-3) in a second species 

(MRID 00086803).

d. Mutagenicity

Acceptable studies for mutagenicity fulfill all three categories for mutagenicity testing (under pre1991 guidelines). Captan is not mutagenic in bacteria, eukaryotic microorganisms, and mammalian 

cells in culture. However, it was mutagenic in human fetal fibroblasts and Chinese hamster cells. 

Furthermore, based on the results of an in vitro calf thymus DNA binding study, a possible 

genotoxic component cannot be ruled out (Ad Hoc Meeting, 9/14/98).

The following is a summary of the mutagenic potential of Captan:

Gene mutation: Captan (50% technical) was not mutagenic in vivo in host-mediated assays in 

mice or rats with the target bacterial cultures of S. typhimurium hisG46 or TA1950, respectively. 

In these assays, mice were treated with Captan orally at 1 g/kg or subcutaneously at 0.5 g/kg and 

rats were treated with Captan orally at 2 g/kg following intraperitoneal injection of bacterial 

cultures (MRID 00131715).

Captan at 0, 1, 5, 10, 15 or 25 μg/plate induced point mutations in E. coli and S. typhimurium 

strains TA100, TA1535, TA1537 and TA1538 in the absence and presence of metabolic 

activation (MRID 00114210).

DNA Damage/Repair: Captan was negative in an assay for unscheduled DNA synthesis (UDS) 

in human fibroblast cells at concentrations up to severely cytotoxic levels, 50-6 M (or molar 

solution) in the absence of metabolic activation; 1000 x 10-6 M in the presence of metabolic 

activation)(MRIDs 00058608 and 00098897). 

Structural Chromosome Aberrations: - Captan was not mutagenic for inducing structural 

chromosome aberrations in human fetal fibroblasts exposed to Captan at 3 or 4 μg/mL dosage 

levels. Also, Captan was not positive for inducing chromosomal aberrations in bone-marrow 

cells of the male rats treated orally up to 2 g/kg Captan in a single dose, or five doses of up to 0.8 

g/kg (MRID 00131725).

Captan was positive for inducing structural chromosome aberrations in Chinese hamster cells at 

4.5 x 10

-5 M and above (MRID 00131727).
Captan/081301 Scoping Document

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e. Metabolism and Dermal Absorption

General Metabolism: The absorption, distribution, metabolism, and excretion of Captan were 

studied in groups of rats administered a single oral gavage of 10 or 500 mg/kg 14C-Captan 

(labeled at 2-C and 7-C positions) or repeated oral dosing of 10 mg/kg unlabeled Captan 

followed by a single dose of 10 mg/kg 14C-Captan on day 15. Captan was rapidly absorbed, 

metabolized and eliminated in rats for all dosing regimens. There were no remarkable sex-, doseor treatment-related differences in the absorption, distribution and elimination of Captan in rats. 

The urine was the main route of elimination regardless of dosing regimen. Total recovery of 

radioactivity in the urine and feces was 69.3-90.8% and 7.3-25.0% of the administered dose, 

respectively in the various groups. The tissues, expired air and cage washes contained less than 

0.8% for all dose groups. The identities of urinary and fecal metabolites of Captan are described 

in detail below. This study satisfies the toxicological guideline data requirement for a 

metabolism study in rats (MRID 41505401 through 41505404).

The initial step in the metabolism of Captan appears to be hydrolysis of Captan into two different 

parts, via cleavage of the N-S bond, to form THPI (tetrahydrophthalimide) and a derivative of 

the trichloromethylthio side chain. A major site of the hydrolytic cleavage of Captan is the 

gastrointestinal tract, although the process also occurs in blood. For each of the two different 

metabolites formed by the hydrolysis of Captan, analysis of 0-48 hour rat urine has indicated the 

presence of a separate metabolic pathway.

For the pathway involving the trichloromethylthio side chain group, a total of 4 urinary 

metabolites were found. The metabolites identified were thiophosgene, thiazolidine-2-thione-4-

carboxylic acid, and dithiobis (methanesulfonic acid) and its disulfide monoxide derivative.

For the THPI pathway, a total of 7 urinary metabolites were found (MRID Nos. 415054-01 to 

415054-04). The primary metabolite was THPI which was formed from the cleavage of the 

trichloro-methylthio moiety. THPI represented 5.7 to 15.4% of the urinary radioactivity. Six 

other metabolites identified were 3-OH THPI, 5-OH THPI, THPI-epoxide, THPI-diol, 

cyclohexene acid amide, and 3-OH-cyclohexene acid amide. 

Five metabolites and one unidentified compound were found in the feces. The unidentified 

compound is suggested to be the parent compound; however data were inadequate to show that it 

was unmetabolized Captan. The primary metabolite was THPI which represented 30 to 39% of 

the fecal radioactivity. 

Although much of the toxicity of captan is attributed to thiophosgene, this moiety is not likely to 

be found in tissues due to its short half-life, and therefore, captan is regulated as the parent 

compound itself.

Dermal Absorption: In a dermal absorption study, male Sprague-Dawley rats were exposed to 2 

doses (0.5 or 5 mg/animal) of ring 14C-labeled Captan. At 1, 2, 4 and 8 hours after dosing, 4 

animals from each dose were sacrificed. The skin at the application site, blood sample, total 

urine and feces and residual carcass were collected and analyzed for radioactivity. A maximum 

daily dermal absorption rate of Captan was approximately 10% based upon 1.3%/hour for 8 
Captan/081301 Scoping Document

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hours at 5 mg/animal. At 0.5 mg/animal, Captan was absorbed at 0.9%/hour. This study 

satisfies the guideline requirement 85-2 for a dermal penetration study (MRID 00117083).
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Chemical Structure

The chemical structures of captan and its major metabolite, THPI, are presented in Table 5 

below. 

Table 5. Test Compound Chemical Identity and Structure

Compound

N

O

O

S

Cl

Cl

Cl

Common name captan

IUPAC name

N-(trichloromethylthio)cyclohex-4-ene-1,2-dicarboximide

CAS name

3a,4,7,7a-tetrahydro-2-[(trichloromethyl)thio]-1H-isoindole-1,3(2H)-

dione

CAS registry 

number

133-06-2

Metabolite

NH

O

O

1,2,3,6-Tetrahydrophthalimide (THPI)

Metabolite

N

O

O

S C

Cl

Cl

O Cl

captan epoxide

Metabolite

NH

O

O

O

THPI epoxide
Captan/081301 Scoping Document

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Metabolite

NH

O

O

OH 3-hydroxy-1,2,6-trihydrophthalimide (3-OH-THPI)

Metabolite

NH

O

O

HO

5-hydroxy-1,2,6-trihydrophthalimide (5-OH-THPI)

Metabolite

Cl3C S S CCl3

 bis(trichloromethyl) disulfide

Captan’s physicochemical properties are summarized in Table 6 below.

Table 6. Physicochemical Properties of the Technical Grade Test Compound.

Parameter Value Reference

Melting range 161-172 °C

Product Chemistry Registration Standard, 

J. Garbus, 2-Apr-1987

RED; D258267, T. Morton. 3-Aug-1999

pH 4.85

Density 0.55 g/cm3

Water solubility (25 °C) <0.5 ppm

Solvent solubility (25 °C)

acetone - <5 g/l

xylene - <5 g/l

ethanol - <5 g/l

kerosene - <5g/l

Vapor pressure (25 °C) <10-6 mm Hg

Dissociation constant, pKa not available

Octanol/water partition coefficient (KOW) 610 ± 90

UV/visible absorption spectrum not available
Captan/081301 Scoping Document

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International Residue Limits 

Captan (081301; 11/29/12)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico1 Codex2

40 CFR 180.103:

Plant: Captan (N-trichloromethylthio4-cyclohexene-1,2-dicarboximide)

3a,4,7,7a-tetrahydro-N-

(trichloromethanesulphenyl)-

phthalimide

Captan

Commodity Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico1 Codex2

Almond 0.25 0.3

Almond, hulls 75.0

Animal feed, nongrass, group 

18

0.05

Apple 25.0 5.0 15 pome fruits Po

Apricot 10.0 5.0 

Blueberry 20.0 5.0 20

Caneberry, subgroup 13A 25.0 5.0 raspberries 20 raspberries, Red, 

Black

Cherry, sweet 50.0 5.0 cherries 25 cherries

Cherry, tart 50.0

Cotton, undelinted seed 0.05

Dill, seed 0.05

Flax, seed 0.05

Grape 25.0 5.0 25 

50 dried grapes 

(=currants, raisins 

and sultanas)

Grain, cereal, forage, fodder 

and straw, group 16

0.05

Grain, cereal, group 15 0.05

Grass, forage 0.05

Grass, hay 0.05

Nectarine 25.0 5.0 3 

Okra 0.05

Peach 15.0 5.0 20 

Peanut 0.05

Peanut, hay 0.05

Pear 25.0 5.0 15 pome fruits Po

Plum, prune, fresh 10.0 5.0 plums 10 plums (including 

prunes)

Rapeseed, forage 0.05

Rapeseed, seed 0.05

Safflower, seed 0.05

Sesame, seed 0.05

Strawberry 20.0 5 15

Sunflower, seed 0.05

Vegetable, brassica leafy, 

group 5

0.05

Vegetable, bulb, group 3 0.05
Captan/081301 Scoping Document

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Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico1 Codex2

Vegetable, cucurbit, group 9 0.05 3 cucumber

10 melons, except 

watermelon

Vegetable, foliage of legume, 

group 7

0.05

Vegetable, fruiting, group 8 0.05 5.0 tomatoes 5 tomato

Vegetable, leafy, except 

brassica, group 4

0.05

Vegetable, leaves of root and 

tuber, group 2

0.05

Vegetable, legume, group 6 0.05

Vegetable, root and tuber, 

group 1

0.05 0.05 potato

MRLS with No US Equivalent

Cranberries 5.0

US [40 CFR §180.103(a)(2)] Canada Mexico1 Codex2

Livestock: Captan (Ntrichloromethylthio-4-cyclohexene-1,2-

dicarboximide) and its metabolite 

1,2,3,6-tetrahydrophthalimide (THPI), 

measured as THPI

N/A N/A

Commodity Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico1 Codex2

Cattle, fat 0.15

Cattle, meat 0.20

Cattle, meat byproducts 0.30

Goat, fat 0.15

Goat, meat 0.20

Goat, meat byproducts 0.30

Hog, fat 0.15

Hog, meat 0.20

Hog, meat byproducts 0.30

Horse, fat 0.15

Horse, meat 0.20

Horse, meat byproducts 0.30

Milk 0.10

Sheep, fat 0.15

Sheep, meat 0.20

Sheep, meat byproducts 0.30

Completed: : M. Negussie; 12/03/2012

1 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.

2 * = absent at the limit of quantitation; Po = postharvest treatment, such as treatment of stored grains. PoP = processed 

postharvest treated commodity, such as processing of treated stored wheat. (fat) = to be measured on the fat portion of 

the sample. MRLs indicated as proposed have not been finalized by the CCPR and the CAC.