Acephate is an organophosphate insecticide. It is used on food crops, citrus trees, as a seed treatment, on golf courses, and in commercial or institutional facilities. At one time acephate was used commonly in and around homes, but most of those uses are no longer allowed. Acephate has been registered by the U.S. EPA since 1973.

Acephate products may be sold as powders, liquids, granules, tablets, and in water-soluble packets. About 100 products that contain acephate are currently registered.

Acephate can kill target insects when they touch it or eat it. When insects eat acephate, their bodies turn it into a chemical called methamidophos, which is another, stronger insecticide. Acephate is less toxic in mammals because mammal bodies do not turn it into methamidophos very well.

Acephate and methamidophos affect the nervous system, causing over-activity in the nerves, muscles, or brain. Acephate is absorbed into plants, so insects that feed on treated plants may eat acephate.

People can be exposed while applying acephate by breathing in the spray mist or by getting spray or granules on their skin. Lower levels of exposure can happen if people work with acephate-treated soils or plants. People may eat acephate residues on fruits or vegetables that were treated with acephate.

Humans and animals absorb acephate into the body quickly when it is eaten, breathed in, or gets on the skin. In animal studies, acephate was absorbed into the blood and went to skin, liver, kidneys, and heart.

In humans and other mammals, about three quarters of the acephate moves through the body unchanged. Some is broken down into smaller chemicals, and a very small amount converts to methamidophos. In rats, most acephate was cleared through the urine, with small amounts cleared through the feces or exhaled breath. Acephate clears the body quickly; less than one percent of the acephate remained in rats three days after eating it.

The EPA classifies acephate as a "possible human carcinogen." When animals were fed acephate in their diets for two years, a greater number of them had liver or adrenal gland tumors. Mice that were fed high doses of acephate all at once had DNA damage in blood cells, although the damage was repaired four days after the exposure.

When rats were fed acephate every day for generations, the animals had reduced mating success and lower survival of their offspring. No changes in nervous system development, behavior or cognitive abilities were seen in offspring in pre- and post-natal exposure studies. Acephate exposure has not been known to cause organophosphate-associated conditions such as intermediate syndrome or Organophosphate-Induced Delayed Polyneuropathy.

In general, children may be more sensitive to pesticides than adults. However, there are currently no studies indicating that children are more sensitive to acephate, specifically. Children may have different symptoms than adults, such as drooling, seizures, muscle weakness, lethargy, coma, and pupil constriction.

Acephate is moderately toxic to birds, depending on the species. Acephate-related health effects in wild birds are reduced eggs, egg hatching, and hatchling survival, and possibly disrupted migratory patterns.

Acephate is slightly toxic to fish and amphibians. After high exposures, salamander hatchlings had decreased growth, activity, and feeding, and increased muscle and spinal column deformities. Acephate is a broad-spectrum insecticide and is highly toxic to bees and other beneficial insects.