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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

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E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Metaldehyde

Trade and Other Names: Some trade names include Antimilace, Antimitace, Ariotox, Cekumeta, Deadline, Halizan, Limatox, Meta, Metason, Namekil, Ortho Metaldehyde 4% Bait, Slug Death, Slug Pellets, Slug-Tox and Slugit Pellets.

Regulatory Status: Metaldehyde is a slightly toxic compound, and products containing it will be in EPA Toxicity Class II or III [1,2]. 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", as well as the signal word CAUTION or WARNING. Because of its potential short-term and long-term health effects on wildlife, metaldehyde is a Restricted Use Pesticide (RUP). RUPs may be purchased and used only by certified applicators.

Chemical Class: Not Available

Introduction: Metaldehyde is a molluscicide 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 used to attract and kill slugs and snails. It is applied in the form of granules, sprays, and dusts, or pelleted or grain bait, typically to the ground around the plants or crops. It works primarily in the stomach by producing toxic effects after it is ingested by the pest. It may be formulated with or without calcium arsenate and is also available in a mixed formulation with thiram.

Formulation: It is applied in the form of granules, sprays, and dusts, or pelleted or grain bait, typically to the ground around the plants or crops.

It may be formulated with or without calcium arsenate and is also available in a mixed formulation with thiram.

Toxicological Effects:

• Acute toxicity: Metaldehyde is slightly to moderately toxic by ingestion, with reported oral LD50 values of 227 to 690 mg/kg in rats, 207 mg/kg in cats, 100 to 1000 mg/kg in dogs, 200 mg/kg in mice, 175 to 700 mg/kg in guinea pigs, and 290 to 1250 mg/kg in rabbits [8,185]. A child died after ingesting 3000 mg (approximately 75 to 100 mg/kg for a 30 to 40 kg child) of metaldehyde [186]. Via the dermal route, it is also moderately toxic. The dermal LD50 for this molluscicide in rats is from 2275 mg/kg to greater than 5000 mg/kg [8]. Metaldehyde is moderately toxic by inhalation; the 4-hour inhalation LC50 in rats is 0.2 mg/L, and the 2-hour inhalation LC50 in mice is 0.35 mg/L [8]. Irritation of the skin, eye, and mucous membranes of the upper airways and gastrointestinal tract may result from contact with metaldehyde [8]. Within a few hours of accidental or intentional ingestion, the following symptoms appeared in humans: severe abdominal pain, nausea, vomiting, diarrhea, fever, convulsions, coma, and persistent memory loss. Other symptoms of high 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 and eventual death in extreme cases [185]. Kidney injury and liver cell death ('necrosis') may also occur [30,31]. Mental deficiencies and memory loss from ingestion poisoning may persist for 1 year or more [185]. It is thought that the formation of acetaldehyde in the gastrointestinal tract is responsible for the narcotic effects observed with metaldehyde exposure [185].
• Chronic toxicity: Dosages which are not toxic when given singly do not cause illness when repeated [185]. Long-term, repeated skin exposure to metaldehyde may result in dermatitis (skin inflammation) in humans [185]. Prolonged eye exposure can cause conjunctivitis [8]. In 2-year toxicity studies and three-generation reproductive studies in rats, changes in liver enzyme activity and increased liver and ovary weight at dietary doses of about 12.5 mg/kg/day were found [185]; 50% of female rats given this dose showed paralysis [8,185]. Effects on the brain (e.g., impairment of memory) may also be possible with chronic exposure at very high levels.
• Reproductive effects: During a three-generation study of rats exposed to chronic ingestion of metaldehyde, adverse effects were seen on reproduction and on the survival rate of offspring [31]. Doses of 50 and 250 mg/kg/day interfered with the reproduction of female rats in another three-generation test [1,31]. These data suggest that metaldehyde is likely to cause reproductive effects only at high levels.
• Teratogenic effects: Dietary doses of 10, 50, and 250 mg/kg of metaldehyde were not teratogenic in three generations of experimental female rats [1,31]. There were some increases in relative liver weights in some offspring [185]. This evidence suggests that metaldehyde is unlikely to cause teratogenic effects.
• Mutagenic effects: Metaldehyde has been reported to be a suspected mutagen [70]. However, there was no evidence of mutagenicity when metaldehyde was tested on five strains of bacteria [185]. The evidence regarding mutagenicity of metaldehyde is inconclusive.
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• Carcinogenic effects: Dietary doses as high as 250 mg/kg/day over a 2-year period did not increase the incidence of tumors in male and female rats [185]. The study suggests that metaldehyde is not carcinogenic.
• Organ toxicity: Metaldehyde or its breakdown byproducts, 'metabolites,' may cause problems in the central nervous system by an unknown mechanism [8,185]. It may also cause lesions in kidneys and the liver following systemic distribution, as well as inflammation of the skin, eye, and mucous membranes of the airways and gastrointestinal tract with direct contact [8,185].

• Fate in humans and animals: Metaldehyde is readily absorbed into the bloodstream from the gastrointestinal tract [31,185]. Metaldehyde's primary decomposition product in the body is acetaldehyde [1,185]. Its metabolites can cross the blood-brain barrier, as evidenced by their effect on the level of consciousness of animals [8].

Ecological Effects:

• Effects on birds: Death of birds feeding in metaldehyde-treated areas has been reported, although the precise acute oral LD50 values or subchronic dietary LC50 values were unavailable [1]. Excitability, tremors, muscle spasms, diarrhea, and difficult or rapid breathing was observed in poultry that were exposed to metaldehyde [31].
• Effects on aquatic organisms: Metaldehyde is reported to be practically nontoxic to aquatic organisms [1,187].
• Effects on other organisms: The 4% pelleted bait is reported to be toxic to wildlife [8]. When used as directed, bait agents with 6% active ingredient are not toxic to bees (30). Bait pellets containing metaldehyde are attractive to dogs [11]. Pets should be confined during application, and kept away from application and storage sites [187].

Environmental Fate:

• Breakdown in soil and groundwater: Metaldehyde is of low persistence in the soil environment, with a half-life on the order of several days [8]. It is weakly sorbed by soil organic matter and clay particles, and is soluble in water [1,8]. Due to its low persistence, it is not a significant risk to groundwater.
• Breakdown in water: Metaldehyde undergoes rapid hydrolysis to acetaldehyde, and should be of low perstistence in the aquatic environment [1].
• Breakdown in vegetation: Many types of flowers lose their color when they come in contact with metaldehyde dust or spray [30].

Physical Properties:

• Appearance: Metaldehyde is a white or colorless crystalline solid with a mild characteristic odor and a powdery appearance [1].
• Chemical Name: r-2,c-4,c-6,c-8-tetramethyl-1,3,5,7-tetroxocane [1]
• CAS Number: 108-62-3
• Molecular Weight: 176.20
• Water Solubility: 260 mg/L @ 30 C [1]
• Solubility in Other Solvents: i.s. in acetic acid; s. in hot carbon disulfide [1]; s. in ethyl alcohol; v.s. in benzene and chloroform; s.s. in ethanol and diethyl ether [1]
• Melting Point: Sublimes at approx. 112 C [1]
• Vapor Pressure: Negligible at room temperature [1]
• Partition Coefficient: Not Available
• Adsorption Coefficient: 240 [11]

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: Not Available
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Lonza, Inc.
17-17 Route 208
Fair Lawn, NJ 07410

• Phone: 800-777-1875
• Emergency: Not Available
  

References:

References for the information in this PIP can be found in Reference List Number 10

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.