Metaldehyde

Description

Metaldehyde (CAS: 108-62-3) is a polymer of acetaldehyde that is used as a pesticide against snails and slugs, and also as a fuel. It was discovered by von Liebig in 1835, and a century later its use as a molluscicide was proposed by Gimingham and Newton in 1937. It is manufactured by reacting acetaldehyde with various acids at a low temperature. As a molluscicide, metaldehyde is used for controlling slugs and snails in gardens of a variety of vegetable and ornamental crops. For this purpose it is available in both solid and liquid formulations with metaldehyde concentrations ranging from 1.8 to 8% in pellet form, or in concentrations of up to 20% in liquid formulations. Some metaldehyde formulations may consist of other pesticides, such as arsenic; while others may contain toxic solvents like ethylene glycol. Therefore, a thorough forensic analysis of the product is recommended to assess complete risk associated with ingestion of these products.
Children under the age of 3 years and pets are most commonly poisoned by ingestion of pellets or cakes containing metaldehyde. Intoxication by metaldehyde is typically acute, characterized initially by gastrointestinal and subsequently followed predominantly by neurologic signs. Vomiting, diarrhea, ataxia, tremors, convulsions, and hyperthermia are among the most common toxic signs in children and animals. Other clinical signs in children include mental confusion, muscle cramps and tremors, loss of consciousness, and coma. The proximate neurotoxic mechanisms are not known but reduced levels of neurotransmitters such as serotonin and g-aminobutryric acid (GABA) are implicated. Delayed effects of acute exposure include hepatotoxicity characterized by hepatic necrosis and increased serum liver enzymes. In general, males metabolize metaldehyde twice as fast as females. Therefore, female animals are more sensitive to metaldehyde poisoning compared to males. Most of the neurotoxic signs are seen at dose levels greater than 100 mg of metaldehyde per kilogram. Developmental studies have shown that metaldehyde exposure during pregnancy does not adversely affect fetuses.
Chronic metaldehyde exposure is unlikely. However, experimental research has shown that metaldehyde is toxic under chronic exposure conditions. In males, chronic metaldehyde exposure causes testicular atrophy and is also toxic to the prostate gland. It causes atrophy of the prostate gland. It is not clear whether the effects on male gonads are due to endocrine disruption or through a different mechanism. There is also suggestive evidence of carcinogenic potential based on the presence of benign tumors in female rats and mice of both sexes.
Provided treatment is initiated early in cases of acute exposure, prognosis is good. In dogs, the mortality rate in a recently completed study was 16%. Because there is no specific antidote, treatment consists of decontamination measures and symptomatic therapy. Recent formulations of metaldehyde pesticides contain denatonium benzoate, a bittering agent. The purpose of adding the bittering agent is to deter excessive ingestion of the products. This, along with new labeling guidelines highlighting the risk to children and pets has caused annual cases to drop significantly since 2006.

Chemical properties

white fine crystalline powder

Chemical properties

Metaldehyde is a white crystalline powder with a mild menthol odor.

The Uses of Metaldehyde

There are over 50 pesticides containing metaldehyde registered for use in the United States. It is commonly used as a pesticide against slugs and snails. It is formulated in ready to use liquid, paste, granules, pellets, minipellets, or meal baits. It is also used as a camping fuel. It may be purchased in a tablet form for the latter use.

What are the applications of Application

2,4,6,8-Tetramethyl-1,3,5,7-Tetraoxacyclooctane is a compound that has been proposed as a potential pesticide

Definition

ChEBI: Metaldehyde is a member of the class of tetroxocanes that is 1,3,5,7-tetroxocane which carries four methyl groups at positions 2,4,6 and 8. It is a potent molluscicide and the active ingredient in most slug pellets used for crop protection. It has a role as a molluscicide and a fuel.

Flammability and Explosibility

Flammable

Agricultural Uses

Molluscicide: A tetramer of acetaldehyde, metaldehyde is a molluscicide used in a variety of vegetable and ornamental crops in the field or greenhouse. It may be formulated with or without calcium arsenate and is also available in a mixed formulation with thiram. A U.S. EPA restricted Use Pesticide (RUP).

Trade name

ANTIMILACE®; ARIOTOX®; CEKUMETA®; DEADLINE®; DURHAM®; HALIZAN®; LIMATOR®; META®; METASON®; NAMEKIL®; SLUG-TOX®; TRAILS END®

Safety Profile

Human poison by ingestion. Human systemic effects by ingestion: convulsions or effect on seizure threshold. Moderately toxic by inhalation and skin contact. Experimental reproductive effects. Mutation data reported. A flammable solid. When heated to decomposition it emits acrid smoke and irritating fumes. See also ALDEHYDES.

Potential Exposure

It is used as a poison for slugs and snails, and as a fuel in small heaters.

First aid

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. 1716 Metaldehyde If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.

Environmental Fate

Metaldehyde is of low persistence in the soil. It is degraded aerobically with a half-life of approximately 67 days to inactive residues. Metaldehyde is soluble in water. Metaldehyde undergoes rapid hydrolysis to acetaldehyde in an aquatic environment.

storage

Color Code—Red: Flammability Hazard: Store in a flammable storage area. Prior to working with metaldehyde you should be trained on its proper handling and storage. Store in tightly closed containers in a cool, wellventilated area away from strong oxidizers. Where possible, automatically transfer material from drums or other storage containers to process containers. Drums must be equipped with self-closing valves, pressure vacuum bungs, and flame arresters. Use only nonsparking tools and equipment, especially when opening and closing containers of this chemical. Wherever this chemical is used, handled, manufactured, or stored, use explosion-proof electrical equipment and fittings.

Shipping

UN1332 Metaldehyde, Hazard Class: 4.1; Labels: 4.1-Flammable solid

Toxicity evaluation

The toxic mechanism in snails and slugs is different from that in mammals and birds. Metaldehyde irreversibly damages mucous secreting cells of snails and slugs on which these organisms depend. In animals and birds, the proximate toxic mechanism of metaldehyde is not known, but is either due to toxicity of metaldehyde itself or of its metabolite acetaldehyde on the brain and other tissues. The fundamental neurotoxic molecular mechanisms are not known, but a depression of serotonin and GABA is suspected to play a role.

Incompatibilities

Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides