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 Antimilace, Antimitace, Ariotox, Cekumeta,
Halizan, Limatox, Meta, Metason, Namekil, Ortho Metaldehyde 4% Bait,
Slug Death, Slug Pellets, Slug-Tox, Slugit Pellets.
Because of its potential short-term and long-term health effects on
wildlife, is classified by the U.S. Environmental Protection
Agency (EPA) as a Restricted Use Pesticide (RUP). Restricted Use
materials may be purchased and used only by certified applicators. All
product labels must include the following statement on the front panel,
"This pesticide may be fatal to dogs or other pets if eaten. Keep pets
out of treated areas" (18). Products containing metaldehyde must bear
the signal word "Caution" or "Warning" (14). Check with specific state
regulations for local restrictions which may apply.
Metaldehyde is a molluscicide used to attract and kill slugs and
snails (1, 4). It is used in a variety of vegetable and ornamental
crops in the field or greenhouse, on fruit trees, small-fruit plants, or
in avocado or citrus orchards, berry plants and banana plants. It is
applied to the soil around plants (7). Care should be taken not to
contaminate edible parts of the plant (1). It is used in the form of
granules, sprays and dusts, or mixed with bran as a bait (8). It works
primarily in the stomach by producing toxic effects after it is ingested
by the pest (7). Metaldehyde is available in pelleted baits (14).
Tablets containing metaldehyde, or meta-fuel, are used in Europe as
fuel for lamps and small stoves. Meta-fuel is not available in the
United States (13).
Metaldehyde is highly toxic by inhalation, moderately toxic by
ingestion and slightly toxic by dermal absorption (16). Skin and eye
irritation may result from exposure to this material (11). Inhalation
of vapors of metaldehyde may cause severe irritation of the mucous
membranes lining the mouth, throat, sinuses and lungs (16). Ingestion
of this molluscicide causes irritation of the stomach and intestines
(7). Metaldehyde can also cause kidney and liver damage (11). One to
three hours after ingestion, the following symptoms may appear: severe
abdominal pain, nausea, vomiting, diarrhea, fever, convulsions, and
coma. Other symptoms of acute exposure include increased heart rate,
panting, asthma attack, depression, drowsiness, high blood pressure,
inability to control the release of urine and feces, incoordination,
muscle tremors, sweating, excessive salivation, tearing, cyanosis,
acidosis, stupor, and unconsciousness (6, 13). Kidney injury and liver
cell death ('necrosis') may also occur (4). Mental deficiencies and
memory loss from ingestion poisoning may persist for one year or more
(10, 13). Death may occur due to kidney or lung failure (6).
Convulsions and eventual death within two hours of administration were
seen in mice that were given an oral dose of 1,000 mg/kg of metaldehyde
The amount of metaldehyde that is lethal to one-half (50%) of test
animals when it is given orally is referred to as its oral lethal dose
fifty, or LD50. The oral LD50 for metaldehyde in rats is 227 to 690
mg/kg, in cats is 207 mg/kg, in dogs is 100 to 1,000 mg/kg, in mice is
200 mg/kg, in guinea pigs is 175 to 700 mg/kg, and in rabbits is 290 to
1,250 mg/kg (1, 13). A child died after ingesting 3,000 mg of
metaldehyde (4). The dermal LD50 for this molluscicide in rats is 2,275
mg/kg to greater than 5,000 mg/kg (1, 7, 16).
The lethal concentration fifty, or LC50, is that concentration of a
chemical in air or water that kills half of the experimental animals
exposed to it for a set time period. The 4-hour inhalation LC50 in rats
is 203 mg/m3. The 2-hour inhalation LC50 in mice is 348 mg/m3 (16).
Dosages which are not toxic when given singly do not cause illness
when repeated (13).
Long-term, repeated skin exposure to metaldehyde can result in
dermatitis, the inflammation of skin in humans (10). Prolonged eye
exposure can cause conjunctivitis. Two-year toxicity studies and three
generation reproductive studies in rats found liver enzyme activity and
increased liver and ovary weight at 250 mg/kg in the diet (12, 13).
Fifty percent of female rats given this dose showed paralysis (12).
During a 3-generation study of rats exposed to chronic ingestion of
metaldehyde, adverse effects were seen on reproduction and on the
survival rate of offspring (10). Dietary levels of 1,000 and 5,000 ppm
interfered with the reproduction of female rats in a 3-generation test
Dietary doses of 10, 50, 250 mg/kg of metaldehyde were not
teratogenic in three generations of experimental female rats (8).
Metaldehyde is suspected of causing mutagenic effects (6). There
was no evidence of mutagenicity when metaldehyde was tested on five
strains of bacteria (13).
Dietary doses as high as 250 mg/kg over a two-year period did not
increase the incidence of tumors in male and female rats (8).
Metaldehyde or its breakdown byproducts, 'metabolites,' may cause
problems in the central nervous system by some unknown mechanism. It
may also cause lesions, inflammation of the gastrointestinal tract,
liver damage, and brain damage (12). The autopsy of a 2-1/2-year-old
boy, who lived only 33 hours after ingesting one tablet of metaldehyde,
showed areas of collapse and congestion in the lungs, as well as
cellular changes in the liver and kidney (8).
Fate in Humans and Animals
The central nervous system is either depressed or excited by
metaldehyde or its metabolites. Metaldehyde is slowly decomposed in the
body to a substance called acetaldehyde, a chemical that acts like a
narcotic. Death from metaldehyde poisoning generally results from over
depression of control centers in the brain that are responsible for the
normal function of respiratory and vasomotor systems. Metaldehyde is
readily absorbed into the bloodstream from the gastrointestinal tract.
Its metabolites can cross the blood-brain barrier, as evidenced by their
effect on the level of consciousness of animals (12). Autopsies of dogs
poisoned with metaldehyde revealed congestion and hemorrhages in the
liver, kidneys and heart (13).
Effects on Birds
Birds may be killed if they feed in metaldehyde-treated areas (2).
Excitability, tremors, muscle spasms, diarrhea, and difficult or rapid
breathing was observed in poultry that was exposed to metaldehyde (12).
Effects on Aquatic Organisms
Available data suggest that metaldehyde is practically non-toxic to
aquatic organisms (17).
Effects on Other Animals (Nontarget species)
The 4% pelleted bait is toxic to wildlife (2). When used as
directed, bait agents with 6% active ingredient are not toxic to bees
(7). Bait pellets containing metaldehyde are attractive to dogs. Pets
should be confined during application, and kept away from application
and storage sites (17).
Breakdown of Chemical in Soil
Metaldehyde has a low potential for groundwater contamination.
While it does not adsorb strongly to soil particles, metaldehyde is
insoluble in water and it has a short soil half-life (15).
Breakdown of Chemical in Water
This material should not be applied directly to water.
Inappropriate storage or disposal, or cleaning of equipment can
contaminate water (2).
Breakdown of Chemical in Vegetation
Metaldehyde must not be applied to edible parts of plants.
Specific product labels should be referred to for particular crop
guidelines (e.g., 4% baits should not be applied to strawberries within
six days of harvest, nor to citrus within 14 days of harvest) (2). Many
types of flowers lose their color when they come in contact with
metaldehyde dust or spray (7).
PHYSICAL PROPERTIES AND GUIDELINES
Metaldehyde is a white or colorless crystalline solid with a mild
characteristic odor and a powdery appearance (1, 9, 12). It may be
formulated with or without calcium arsenate and is also available in a
mixed formulation with thiram (1, 7). It is flammable and burns with a
nonsmoking flame (8). It is dangerous when exposed to heat or flame and
can react with oxidizing materials (11). Thermal decomposition of
metaldehyde may release toxic oxides of carbon. Mixtures of metaldehyde
dust and air may explode (16). It is compatible with other substances
that are in neutral media. Metaldehyde is noncorrosive (7).
Metaldehyde should be used and stored under conditions that are not
hazardous. All precautions should be taken to ensure that bait does not
get mistaken for food or feed. As it is harmful if swallowed, it should
be kept out of the reach of children and pets. Contamination of the
edible parts of plants should be avoided when applying metaldehyde (1).
Breathing of its dust, as well as skin, eye, or clothing contact should
be avoided (2, 7). A respirator should be worn when using metaldehyde
dust (7). After handling, a thorough washing is recommended (1). All
unprotected persons should be kept out of the range of drift. Treated
areas must not be entered without protective clothing until dusts
settle. Metaldehyde is combustible and should be stored in its original
container in a cool place, to minimize sublimation. Prolonged storage
should be avoided (2).
Occupational Exposure Limits:
No occupational exposure limits have been established for
metaldehyde by OSHA, NIOSH or ACGIH (16).
|CAS #: ||108-62-3 (13)
|Specific gravity: ||1.27 (16)
|H20 solubility: ||insoluble in water (1); 23 mg/l (15)
|Solubility in other solvents: ||insoluble in acetic acid; soluble in hot carbon disulfide (12)
soluble to 1.8 g/100 ml in ethyl alcohol at 70 degrees C (1)
fully soluble in benzene and chloroform, but only slightly soluble in ethanol and diethyl ether (8)
|Melting point: ||246 degrees C (475 degrees F) (sealed capillary) (9, 13); 234-239 degrees (10)
|Boiling point: ||sublimes at 110-120 degrees C (13)
|Flash point: ||97 degrees F (36 degrees C) (16)
|Vapor pressure: ||Low at room temperature; considerable at higher temperatures (7)
|Chemical Class/Use: ||Aldehyde molluscicide
|Koc: ||240 g/ml (15)
Chevron Chemical Company
Agricultural Chemicals Division
6001 Bollinger Canyon Rd.
San Ramon, CA 94583
Review by Basic Manufacturer:
Comments solicited: October, 1992
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