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
Some trade names include Dithane M-45, Manzate 200, Mancozeb, Fore,
Green-Daisen M, Karamate, Mancofol, Zimaneb, Manzeb, Policar, Dithane-
Ultra Nemispot, Nemispor, Riozeb, Mancozin, Manzin. Common names
include mancozeb and manzeb.
Mancozeb is registered as a general use pesticide by the U.S.
Environmental Protection Agency (EPA). In July 1987, the Environmental
Protection Agency announced the initiation of a special review of the
ethylene bisdithiocarbamates (EBDCs), a class of chemicals to which
mancozeb belongs. This Special Review was initiated because of concerns
raised by laboratory tests on rats and mice. The EPA was concerned
part of the Special Review, EPA reviewed data from market basket surveys
and concluded that actual levels of EBDC residues on produce purchased
by consumers are too low to affect human health. The EPA concluded its
Special Review in April, 1992 with new label requirements for protective
clothing to be worn by industrial and agricultural workers, and with the
establishment of a 24-hour reentry period for agricultural workers.
Many homegarden uses of EBDCs have been canceled because the EPA has
assumed that home users of these pesticides do not wear protective
clothing during application (18). Toxicity data reviewed by the EPA as
part of their Special Review of EBDCs are included in this document
under "Toxicological Effects."
- potential effects on the general population from dietary exposure to residues left on food crops and
- potential occupational health risks to workers who handle and/or apply EBDC pesticides.
Containers of this fungicide bear the signal word "CAUTION" (2).
The EBDCs are fungicides used to prevent crop damage in the field
and to protect harvested crops from deterioration in storage or
transport (21). Mancozeb is used to protect many fruit, vegetable, nut
and field crops against a wide spectrum of diseases, including potato
blight, leaf spot, scab (on apples and pears) and rust (on roses). It
is also used for seed treatment of cotton, potatoes, corn, safflower,
sorghum, peanuts, tomatoes, flax and cereal grains (2, 16, 17).
Mancozeb is not taken up from the soil by plants (6). It is a
combination of two other chemicals of this class, maneb and zineb (9).
Mancozeb is available as dusts, liquids, water dispersible granules, as
wettable powders, and as ready-to-use (R-T-U) formulations (17).
Mancozeb has a very low acute toxicity to mammals. No
toxicological effects were observed in a long term study with rats fed
doses of 5 mg/kg (16). The major routes of exposure to mancozeb are
through the skin or from inhalation (13). In spray or dust forms, the
EBDCs are moderately irritating to the skin and respiratory mucous
membranes. Symptoms of poisoning from this class of chemicals include
itching, scratchy throat, sneezing, coughing, inflammation of the nose
or throat, and bronchitis (9, 19). There is no evidence of
'neurotoxicity,' nerve tissue destruction or behavior change, from the
EBDCs (9). However, dithiocarbamates are partially chemically broken
down, or metabolized, to carbon disulfide, a neurotoxin capable of
damaging nerve tissue (5).
The amount of a chemical that is lethal to one-half (50%) of
experimental animals fed the material is referred to as its acute oral
lethal dose fifty, or LD50. The oral LD50 for mancozeb ranges from
4,500 to 11,200 mg/kg in rats. When applied to the skin of rabbits, its
dermal LD50 is 5,000 to 15,000 mg/kg (2, 13, 16, 17). It is a mild skin
irritant and sensitizer, and a mild to moderate eye irritant in rabbits
(4). Agricultural workers handling crops treated with mancozeb have
developed sensitization rashes (16).
In a two-year study dogs were fed doses of 0, 0.625, 2.5 or 25
mg/kg of mancozeb. Lower iodine uptake was observed after 24 months in
dogs fed the two highest doses, while no difference was observed between
those dogs fed 0 and 0.625 mg/kg (16).
Mancozeb is comparable to another chemical, maneb, on which the
following long-term studies have been conducted. A two-year feeding
study on rats indicated that 6.25 mg/kg of maneb in the diet is the no
observable effect level (NOEL) for rats. However, the next and highest
level that was fed to rats in this two-year study did produce signs of
poisoning. A one-year feeding study in dogs concluded that 20 mg/kg/day
is a NOEL for dogs. Toxic effects were seen in the dogs at daily doses
of 75 mg/kg and 250 mg/kg (4).
The ethylene bisdithiocarbamate pesticides (EBDCs), which include
mancozeb, are generally considered to have low short-term mammalian
toxicity. A major toxicological concern, however, is ethylenethiourea
(ETU), an industrial contaminant and a breakdown product of mancozeb
and other EBDC pesticides. In addition to having the potential to cause
goiter, a condition in which the thyroid gland is enlarged, this
metabolite has produced birth defects and cancer in experimental
animals. ETU has been classified as a probable human carcinogen by the
EPA (18). ETU can be produced when EBDCs are used on stored produce,
and also when fruit or vegetables with residues of these fungicides are
In a three-generation rat study with mancozeb at a dietary level of
50 mg/kg there was reduced fertility but no indication of embryo toxic
or teratogenic effects. In another study in which pregnant rats were
exposed to mancozeb by inhalation, toxic effects on the pups were
observed only at doses (55 mg/m3) that were also toxic to the dams
No teratogenic effects were observed in a three-generation rat
study with mancozeb at a dietary level of 50 mg/kg (16). Specific
developmental abnormalities of the body wall, central nervous system,
eye, ear and musculoskeletal system were observed in experimental rats
which were given 1,320 mg/kg of mancozeb on the 11th day of pregnancy
(10). When it was inhaled at concentrations of 0.017 milligrams per
liter (mg/l), mancozeb was not teratogenic to pregnant rats (4).
Teratogenic activity was found in mice given 1,320 mg/kg of maneb (11).
In pregnant rats fed 5.0 mg/kg/day, the lowest dose tested,
developmental toxicity was observed in the form of delayed hardening if
the bones of the skull in offspring. ETU has also been shown to be
teratogenic in hamsters, but not in mice (18).
A data gap exists in the information available on the mutagenicity
of mancozeb and ETU. Mancozeb was found to be mutagenic in one set of
tests, while in another it did not cause mutations (13). Mancozeb is
thought to be similar to maneb, which was not mutagenic in a test called
the Ames Test (4).
Ethylenethiourea (ETU), a metabolite of the class of chemicals in
which mancozeb is included, has caused cancer in experimental animals
and has been classified as a probable human carcinogen by the EPA
(9, 13, 18, 21).
Several studies of the effects of EBDCs on test animals have shown
rapid reduction in the uptake of iodine and swelling of the thyroid
(i.e. goiter). In one study, a marked reduction of iodine uptake was
measured 24-hours after administration of a large dose of maneb, another
EBDC fungicide. A 90-day study of the effects of ETU, a common
metabolite of the EBDCs on rat thyroids revealed a NOEL of 5 ppm (0.25
mg/kg/day) (9, 16, 18).
Fate in Humans and Animals
The EBDC fungicides break down in mammalian tissues into ethylene
thiourea, ETU, a metabolite which has caused goiter and cancer in
laboratory animals (9, 18).
Research shows that mancozeb is rapidly absorbed into the body from
the gastrointestinal tract, distributed to various target organs and
almost completely excreted in 96 hours. ETU is the major metabolite.
After a single dose, less than one ppm ETU residues were measured in the
thyroid and liver. After 24 hours, these residues were not detectable
(13). Blood detection of ethylene bisdithiocarbamate is rarely
possible, although there are methods for detecting the metabolite
ethylene thiourea in urine (9).
Effects on Birds
Mancozeb is slightly toxic to birds on an acute basis (13). The
lethal concentration fifty (LC50) is the concentration of a material in
air or water that kills half of a population that is experimentally
exposed to the chemical for a given time period. The five-day LC50 for
mancozeb in bobwhite quail and mallard ducklings is greater than 10,000
ppm (4). The EPA is currently reviewing data on the effects of mancozeb
on bird reproduction (18).
Effects on Aquatic Organisms
Mancozeb is generally toxic to fish. It is highly poisonous to
warmwater fish and at least moderately toxic to coldwater fish. Many
end-use product labels warn of its toxicity to fish (13). The EPA is
currently reviewing data on the potential toxic effects of mancozeb on
aquatic organisms (18).
Effects on Other Animals (Nontarget species)
Mancozeb is harmful to wildlife but not hazardous to honey bees
(6). The 72-hour LC50 for mancozeb in crayfish is greater than 40 ppm;
the 48-hour LC50 is 3.5 ppm in tadpoles (4).
The EBDCs are generally unstable in the presence of moisture,
oxygen, and in biological systems (22). They rapidly degrade to ETU.
This rapid degradation lowers the need for concern about the
environmental fate of EBDCs and focuses such concern on ETU. The EPA
has either called for or is currently reviewing data on the behavior of
ETU in the environment (9, 14, 18).
Breakdown of Chemical in Soil and Groundwater
Because mancozeb is practically insoluble in water it is unlikely
to infiltrate groundwater (17, 20). Studies do indicate that ETU, a
metabolite of mancozeb, has the potential to move through the soil as a
result of groundwater movement, in a process called leaching (13). ETU
has been detected at 16 ppb in only one out of 1,295 drinking water
wells tested (18).
The breakdown of mancozeb in soil is assumed to be comparable to
that of maneb, which has a half-life of four to eight weeks under normal
field conditions (4).
Breakdown of Chemical in Water
Mancozeb degrades in water with a half-life of one to two days at
pH 5, 7 and 9 (13). It should be kept out of lakes, streams and ponds
and should not be applied where runoff is likely to occur (4). This
fungicide should not be stored or thrown away near or in water, since
storage or disposal of mancozeb in or near bodies of water can cause
Breakdown of Chemical in Vegetation
When used as directed, mancozeb is not poisonous to plants (6). A
24-hour reentry interval is required in mancozeb-treated crops because:
(1) the fungicide is registered on crops which may present a great deal
of residue exposure and (2) the mancozeb metabolite, ETU, has been shown
to produce tumors, birth defects, cell mutations and thyroid effects
(13). The EBDCs can be broken down during the cooking process as well
as by natural environmental processes (14).
PHYSICAL PROPERTIES AND GUIDELINES
Keep mancozeb out of reach of children, unprotected persons,
livestock, and pets (4, 13). Breathing of dust or spray mist from
mancozeb should be avoided. Contact with skin, eyes and clothing should
also be avoided. Protective clothing including long pants, long sleeve
shirt, gloves, hat and boots should be worn during mixing, loading,
application and early reentry into treated fields (13, 18). Do not feed
treated crop foliage to livestock (12). Water, food or feed can be
contaminated by storage or disposal of mancozeb near these commodities.
Empty containers should not be reused. They should be buried away from
water supplies (2).
Mancozeb is a grayish-yellow powder with a musty odor (19) which is
practically insoluble in water as well as most organic solvents. It is
a polymer of maneb combined with zinc. While it is relatively stable
and noncorrosive under normal, dry storage conditions, it is decomposed
at high temperatures by moisture and by acid. Mancozeb may produce
flammable products upon decomposition (4, 16). It is also unstable in
acidic conditions (7). It should be stored in its original sealed
containers in well-aired, dry storehouses or in shaded, aired places.
The temperature of the material should not go above 25 to 30 degrees C.
Mancozeb containers must be stacked so that air can move freely at the
bottom and sides of piles. As long as the product is stored in its
unopened and undamaged original containers in well-ventilated places,
its biological activity will remain stable for 2 years (2).
Mancozeb is stable under most conditions. It may burn, but does not
readily ignite, and containers may explode in the heat of a fire.
Thermal decomposition products may include toxic oxides of carbon,
nitrogen and sulfur. Suspensions of mancozeb dust in the air can ignite
or explode (19).
Occupational Exposure Limits:
|OSHA: ||5 mg/m3 ceiling (19)
|ACGIH: ||5 mg/m3 TWA (19)
|NIOSH: ||1 mg/m3 recommended TWA (19); 3 mg/m3 recommended STEL (19)
|TLV: ||5 mg (Mn)/m3 (1)
|CAS #: ||8018-01-7
|H20 solubility: ||dispersible, but practically insoluble in water (7, 8, 19)
|Solubility in other solvents: ||practically insoluble in most organic solvents (8)
|Melting point: ||Decomposes without melting (7)
|Vapor pressure: ||Less than 10 to the minus 5 power mbar at 20 degrees C
|Chemical Class/Use: ||Carbamate fungicide; Ethylene bisdithiocarbamate (EBDC)
Du Pont Agricultural Products
Walker's Mill, Barley Mill Plaza
PO Box 80038
Wilmington, DE, 19880-0038
Review by Basic Manufacturer:
Comments solicited: October, 1992
Comments received: November, 1992
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