Aldrin and dieldrin are the common names of two insecticides that are closely related chemically; aldrin is readily converted to dieldrin in the environment and in the human body. Their toxicities do not differ significantly. The main effects from short-term exposure to high levels or doses of aldrin and dieldrin are headache, dizziness, irritability, loss of appetite, nausea, muscle twitching, convulsions, and loss of consciousness; death may occur at extremely high exposures or doses. All symptoms disappear with time after removal from a nonlethal exposure. The use of protective clothing and respirators is necessary under conditions when high exposures may occur.
Long-term occupational exposure to fairly low levels of aldrin and dieldrin has not been documented as resulting in any demonstrable adverse effects. Studies with animals fed dieldrin have shown that the liver can be damaged and the ability of the immune system to protect against infections can be suppressed. Oral doses of aldrin and dieldrin have caused liver cancer in mice but not in rats. Although there is inadequate evidence to judge whether aldrin/dieldrin are carcinogenic in humans, the Environmental Protection Agency (EPA) considers aldrin and dieldrin probable carcinogens based on sufficient evidence in animals. There is inconclusive evidence in humans, but more evidence in animals, that exposure of a pregnant female to aldrin and dieldrin may be associated with harm to the fetus.
Aldrin and dieldrin were widely used from the 1950s to the early 1970s. Aldrin has been used as a soil insecticide to control root worms, beetles, and termites. Dieldrin has been used in agriculture for soil and seed treatment and in public health to control disease vectors such as mosquitoes and tsetse flies. Dieldrin has also had veterinary use as a sheep dip and has been used in treatment of wood and mothproofing of woolen products. Persons could be occupationally exposed to aldrin and dieldrin from inhalation and by absorption through the skin. Most uses for aldrin and dieldrin were banned in 1975; at present these compounds are no longer produced in or imported into the United States.
Although dieldrin is persistent in soil, environmental background levels are known to be decreasing slowly. Residual contamination may be present at waste sites from the disposal of used stocks. Where this is appreciable, a potential exists for exposure to cleanup workers. Air and water appear to be sources of minor importance to the general population with regard to aldrin and dieldrin exposure. In the past, food products grown in soil treated with aldrin or dieldrin have probably been the primary source of dieldrin residues in fatty tissues of the general population; however, since 1970, dietary intake has shown a significant decrease. Because neither aldrin nor dieldrin are currently produced in or imported into the United States, their use is believed to be minimal. Possible new releases may come from the use of individually owned stockpiles of aldrin for the underground control of termites, although because importation of aldrin ceased more than 3 years ago, it is believed that there is very little, if any, termiticide stock left in this country. Higher exposure rates can be expected for persons residing in homes treated with aldrin for termite control. Improper application practices by applicators may result in unnecessarily high exposure to occupants of treated structures.
In 1974, EPA suspended nearly all uses of aldrin and dieldrin on the basis of cancer risks for both compounds. Ultimately, all uses on food crops were banned. Use of aldrin as a subterranean termiticide continued after 1974, but the sole importer ceased importation in 1985 and cancelled its registration in 1987, and all other termiticide registrations of aldrin have been either cancelled or suspended.
The most likely way that aldrin and dieldrin have entered the human body in the past is by eating food grown in treated soil, by eating products from animals previously exposed to these insecticides (fish, poultry, or beef), or by drinking water or milk containing the compounds. Since aldrin and dieldrin cannot be used on farm crops at this time, the risk of exposure through these routes has been reduced. Exposure to indoor air in aldrin-treated structures may presently be the most likely source of exposure. It is possible to breathe air containing aldrin or dieldrin in homes that have been treated with these compounds for termite control. There is also potential for exposure to the applicators and nearby residents if improper procedures are used. Occupationally, aldrin and dieldrin may enter the body by penetrating the skin. However, since these compounds are no longer available to any extent, this route of exposure is no longer likely except as a potential threat to cleanup workers at hazardous waste sites.