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Captan

Publication Date: 9/93

TRADE OR OTHER NAMES

Trade names for captan include Orthocide, Clomitane, Vancide 89, Agrox and Merpan.

INTRODUCTION

Captan is a non-systemic fungicide used to control diseases of many fruit, ornamental, and vegetable crops. It is used in agricultural production as well as by the home gardener. A major use of captan is in apple production. Fifty percent of all of the apple acreage in the U.S. is treated with captan as is sixty percent of the almonds and one hundred percent of the Florida strawberries. One million tons of apples receive captan after harvest. It is applied to packing and shipping boxes for fruits and vegetables.

Captan is used as a preservative for awnings, draperies and leather, as a root dip and seed treatment and is incorporated into paints, wallpaper pastes, plastic and leather goods. There are over 320 federally registered pesticide products that contain captan. Most uses of captan on food crops have been cancelled in the United States since 1989.

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Captan has a low acute toxicity and generally carries the signal word CAUTION. However it may carry the DANGER label if it is packaged in a concentrated form, often as a dust or powder. The rat oral LD50 ranges from 8,400 to 15,000 mg/kg (4). The mouse LD50 is 7,000 mg/kg. The lowest dose for humans that can cause death is 1,071 mg/kg (2). Sheep showed no effect at doses of 200 mg/kg, but experienced deaths at 250 mg/kg. The inhalation LC50 in mice was 5,000 mg/m3 for a two hour exposure (2). Rabbits showed little or no skin sensitization from dermal doses while guinea pigs were moderately sensitive (3).

CHRONIC TOXICITY

Rats fed up to 15,000 ppm of Orthocide for four weeks had decreased food intake and body weights (3). Pigs tolerated (no deaths) 420 to 4,000 mg/kg in the diet for three months to 25 weeks, but cattle given six doses of 250 mg/kg experienced varied toxic effects including death (3).

Reproductive Effects

Pregnant mice exposed by inhalation to high doses of captan for four hours a day during days 6 to 15 of gestation showed significant mortality or weight loss. Fetal mortality accompanied these effects. Mice fed 50 mg/kg over three generations reproduced normally. Fertility and litter size was normal as was the growth of the young. It is not likely that captan would cause reproductive effects in humans at usual levels of exposure.

Teratogenic Effects

Teratogenicity studies with rats, rabbits, hamsters, and dogs have given both negative and positive results in each of these species. The EPA evaluated this data in 1989 and concluded that captan does not produce birth defects (10).

Mutagenic Effects

Although captan was mutagenic in some laboratory tests on isolated tissue cultures, the EPA has determined that captan is either non- mutagenic or has very low mutagenicity in animals (10).

Carcinogenic Effects

There is strong evidence that captan causes cancer in female mice and in male rats. In addition, captan is chemically similar to two other pesticides that have been shown to produce cancer in test animals Tumors were associated with the gastrointestinal tract and, to a lesser degree, with the kidneys. Tumors appeared in the test animals at the low doses (as compared to the LD50) of around 300 mg/kg. The EPA classifies captan as a probable human carcinogen.

Organ Toxicity

Workers exposed to high concentrations of captan in air (5 mg/m3) experienced eye irritation including burning, itching and tearing. Skin irritation also occurred in some cases (3).

Fate in Humans and Animals

Studies in several animal species have shown that captan is rapidly absorbed from the GI tract and is rapidly metabolized. Residues are excreted primarily in the urine. Rats given captan orally excreted a third in the feces and half in the urine in 24 hours. In another study rats exhaled fifteen to thirty percent in the expired air in 45 hours. At the end of 96 hours between ten and thirty percent had been excreted in the feces and about fifty percent in the urine. There was one percent remaining in the tissues.

A cow fed small amounts in its diet for four days had no captan in the milk at a 0.01 ppm detection limit nor could any be detected in the urine at a 0.1 ppm detection limit (3).

Rabbits injected with 500 mg/kg showed no captan in the blood over a 56-hour period. The metabolite, THPI was detected with a peak concentration of 25 g/ml at 25 hours after dosing (3).

ECOLOGICAL EFFECTS

The 96-hour LC50 for technical captan ranges from 56 ppb for cutthroat trout and chinook salmon to 141 ppb for bluegill. The pesticide is very highly toxic to fish. Fish exposed for three days to concentrations which would be expected in a pond following treatment of an adjacent watershed at a rate of 1 lb/acre, had no detectable residues of parent captan. Fish tissues contained less than 0.1 ppm of an unidentified metabolite. In another experiment, fish exposed to a rate equivalent to 1 lb/acre had 0.378 ppm after 20 days. 5.6% of this was parent captan (3). The EPA has expressed concern over the toxicity of captan to aquatic organisms, but there are no aquatic uses of this fungicide and thus EPA has concluded that the potential risks from captan would be localized and minor (10).

Birds are much less susceptible to captan than are rats and mice. High doses administered for 90 days to chickens caused an 80% reduction in the number of eggs produced but had no effect on the fertility or hatchability of the eggs produced (3). At lower, but still relatively high doses, quail, pheasants and mallards experienced no mortality when fed captan in their food for 74 days (3).

Honeybees are quite suseptible to low concentrations of Captan.

Captan has a low to moderate tendency to accumulate in living tissue. Estimates of the bioconcentration factor range from 10 to 1,000 (11).

ENVIRONMENTAL FATE

Captan has a relatively short persistence in soil with a half-life of one to ten days in most soil environments (3). It is not mobile in soil and was not detected in the EPA's national survey for pesticides in groundwater. The survey tested more than eight hundred wells throughout the country. Captan has been found in drinking water by other sources but the concentrations were not given (11).

Captan is rapidly degraded in near neutral water. Half-lives of 23 to 54 hours and one to seven hours have been reported under various acidities and temperatures (3). The effective residual life in water is two weeks (4). Evaporation from the soil surface can be significant (11).

Residues on plant leaf surfaces were 800 ppm after two days, 450 ppm after 13 days, 150 ppm in 27 days and below the detection limit 40 days after application. Residual fungitoxicity remains for 23 days after application on potato leaves. The main metabolite is THPI, tetrahydrophthalimide (3).

Exposure Guidelines:

NOEL: (rats) 12.5 mg/kg/day
ADI: 0.100 mg/kg/day (WHO)
TLV TWA: 5 mg/m3
Q*: 2.3 x 10 to the minus 3 power
LEL: 25 mg/kg/day (rat)
LEL: 0.13 mg/kg/day (EPA)

Physical Properties:

CAS #: 133-06-2
Chemical Name: 3a,4,7,7a-tetrahydro-2-[(trichloromethyl)thio]-1H-isoindole-1,3(2H)-dione
Chemical class/use: phthalimide fungicide
Solubility in water: 5.1 mg/l
Solubility in other solvents: xylene 20 g/kg; acetone 21 g/kg; propan-02-ol 1.7 g/kg
Melting Point: 178 degrees C
Vapor Pressure: 8 x 10 to the minus 8 power mm Hg

BASIC MANUFACTURER

Drexel Chemical Co.
PO Box 9306
2487 Pennsylvania St.
Memphis, Tennessee 38109
Emergency: 901-774-4666
Telephone: 901-774-4370

Review by Basic Manufacturer:

Comments solicited: November, 1992
Comments received:

REFERENCES

  1. National Cancer Institute (1977). Bioassay of Captan for Possible Carcinogenicity, U.S. Department of Health, Education and Welfare, Public Health Service, National Institutes of Health, Technical Report Series No. 15.
  2. National Library of Medicine (1987). Hazardous Substances Databank. TOXNET, Medlars Management Section, Bethesda, MD.
  3. Forest Service (1986). Pesticide Background Statements, Vol II Fungicides and Fumigants. U.S. Dept of Agriculture, Agriculture Handbook No. 661.
  4. Chemical Information Systems, Inc. (1988). Oil and Hazardous Materials/Technical Assistance Data System, Baltimore, MD.
  5. Worthing, Charles R., Editor (1983). The Pesticide Manual, A World Compendium. The British Crop Protection Council, The Ravenham Press Limited, Ravenham, Suffolk, England.
  6. National Research Council (1987). Regulating Pesticides in Food, The Delaney Paradox, National Academy Press, Washington, DC.
  7. U.S. Environmental Protection Agency (1983-85). Chemical Information Fact Sheet. Office of Pesticides and Toxic Substances, Office of Pesticide Programs (TS-766C)
  8. Food and Drug Administration (1986). The FDA Surveillance Index. Bureau of Foods, Dept of Commerce, National Technical Information Service, Springfield, VA.
  9. Ecobichon, Donald J. (1991). Toxic Effects of Pesticides in Casarett and Doull's Toxicology: The Basic Science of Poisons, Fourth Edition. Mayo O. Amdur, John Doull, and Curtis D. Klaassen editors. Pergamon Press, NY.
  10. Federal Register. Volume 54, No. 36. Friday, February 24, 1989. Notices pp. 8116-8150.
  11. Howard, Philip, H. 1991. Handbook of Environmental Fate and Exposure Data for Organic Chemicals. Volume III, Pesticides. Lewis Publishing, Chelsea, MI.