E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of
Cornell University, Michigan State University, Oregon State University, and
University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact
Publication Date: 9/93
TRADE OR OTHER NAMES
Trade names for captan include Orthocide, Clomitane, Vancide 89,
Agrox and Merpan.
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
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).
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
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.
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).
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).
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.
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).
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
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
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,
|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)
|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
Drexel Chemical Co.
PO Box 9306
2487 Pennsylvania St.
Memphis, Tennessee 38109
Review by Basic Manufacturer:
Comments solicited: November, 1992
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