Naled is an insecticide in the organophosphate pesticide family used primarily for mosquito control. Dibrom is a common brand name for naled products. About one million pounds are used annually in the U.S. Like all organophosphates, naled is toxic to the nervous system. Symptoms of exposure include headaches, nausea, and diarrhea. Naled is more toxic when exposure occurs by breathing contaminated air than through other kinds of exposure. In laboratory tests, naled exposure caused increased aggressiveness and a deterioration of memory and learning.
Naled’s breakdown product dichlorvos (another organophosphate insecticide) interferes with prenatal brain development. In laboratory animals, exposure for just 3 days during pregnancy when the brain is growing quickly reduced brain size 15 percent. Dichlorvos also causes cancer, according to the International Agency for Research on Carcinogens. In laboratory tests, it caused leukemia and pancreatic cancer. Two independent studies have shown that children exposed to
household “no-pest” strips containing dichlorvos have a higher incidence of brain cancer than unexposed children. Aerial applications of naled can drift up to one-half mile. According to the U.S. Environmental Protection Agency, naled is moderately to highly toxic to birds and fish. It also reduced egg production and hatching success in tests with birds and reduced growth in tests with juvenile fish.

Like most pesticides, commercial naled-containing insecticides contain ingredients other than naled. Many of these ingredients, according to U.S. pesticide law, are called “inert.” Except for tests of acute effects, toxicology tests required for the registration of a pesticide are not conducted with the combination of ingredients found in commercial products. Most inert ingredients are not identified on product labels, and little information about them is publicly available. For information about the inert ingredients in Dibrom products, see “Inerts in Dibrom Products,”. A symptom of exposure to naled that occurs at low doses (whether by breathing, through the skin, or orally) is inhibition of acetylcholinesterase (AChE). In studies conducted by naled manufacturers, exposure of rats to naled in air at a dose of 0.3 milligrams per kilogram of body weight (mg/kg) per day for three weeks, skin exposures of 20 mg/kg per day for 4 weeks, and oral exposure of 10 mg/kg per day for 4 weeks caused inhibition of AChE. Long-term exposure also caused AChE inhibition; reduced AChE activity occurred in dogs exposed orally to 2 mg/kg per day for 1 year and in rats exposed orally to the same dose for 2 years. In addition, the long-term study with dogs found that doses of 2 mg/kg per day also caused mineralization of the spinal cord.
Naled’s breakdown product dichlorvos inhibits the activity in rats of a nervous system enzyme called neuropathy target esterase. In experiments conducted by biochemists at the Postgraduate Institute of Medical Education and Research (India), doses of 6 mg/kg per day reduced the enzyme’s activity by about 40 percent. Inhibition of this enzyme causes partial paralysis of the hind legs followed by incoordination.