Carbaryl is classified as moderately to very toxic, and is classified as a likely human carcinogen (cancer-causing substance) by the Environmental Protection Agency.

A family of chemicals, called carbamates, is of potential concern to humans. Carbaryl is a carbamate chemical. Carbamates work by interfering with the transmission of nerve signals. The chemical process they attack is common to insects, humans, dogs and cats, so they harm more than just the target insect. Indeed, thousands of acute toxic poisonings have been logged at poison control centers across the United States. 

Children, and particularly toddlers, are especially vulnerable. Their nervous systems are still developing, so the damage done can be greater and more lasting.

Carbaryl also inhibits enzymes required for detoxification, which are important to the functioning of the immune system.

Carbaryl is extremely toxic to aquatic and estuarine invertebrates, including insects and crustaceans, and moderately to highly toxic to fish. This underlines the need to keep any carbaryl spray away from all bodies of water, which is why spraying close to water is legally prohibited. However, several sightings have been reported of carbaryl being sprayed by the Town of Grand Lake and THC Enterprises along Grand Lake in the channel at Point Park and on Moose Lake in the summer of 2007.

Carbaryl is toxic to aquatic organisms, such as rainbow trout and bluegill. Some accumulation of carbaryl can occur in catfish, crawfish and snails, as well as in algae and duckweed. It is also harmful to salmon.

In view of EPA findings, repeated heavy soakings with large quantities of carbaryl on scattered trees, from the ground up to 35 feet, with high potential for drift and off-target pesticide movement, very likely has a negative impact on native and residential bee and beneficial insect populations. The spraying may actually kill bark beetle predators and increase bark beetle problems in the very stands where prevention and protection is most needed.

Hundreds of species of birds’ diets consist solely or mainly of insects, many of which carbaryl kills. In fact, it is estimated that carbaryl kills approximately 100 non-target insects. Therefore, the diet of many birds is reduced or eliminated with carbaryl spray, adversely affecting these birds.

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Environmental Fate of Carbaryl