Permethrin

PERMETHRIN

Permetherin is extremely toxic to aquatic life, bees, and other wildlife. It should not be applied to crops or weeds where foraging may occur.

Permethrin, like all synthetic pyrethroids, is a neurotoxin. Symptoms include tremors, incoordination, elevated body temperature, increased aggressive behavior, and disruption of learning. Laboratory tests suggest that permethrin is more acutely toxic to children than to adults.

The U.S. Environmental Protection Agency (EPA) has classified permethrin as a carcinogen because it causes lung tumors in female mice and liver tumors in mice of both sexes. Permethrin inhibits the activity of the immune system in laboratory tests, and also binds to the receptors for a male sex hormone. It causes chromosome aberrations in human and hamster cells.

Permethrin is toxic to honey bees and other beneficial insects, fish, aquatic insects, crayfish, and shrimp. For many species, concentrations of less than one part per billion are lethal. Permethrin causes deformities and other developmental problems in tadpoles, and reduces the number of oxygen-carrying cells in the blood of birds.

Aquatic Insects: Because it is a broad spectrum insecticide, permethrin has severe impacts on aquatic insects. Permethrin applications to forest streams caused “a major increase in the density of drifting invertebrates” described as “catastrophic.” (Drifting animals are those that are sufficiently poisoned by the insecticide that they are washed down-stream.) Most applications were also followed by “rapid depletion of bottom fauna,” insects that live in the stream bed. Recovery required between 1 and 18 months. Mayflies and damselflies are the most sensitive species. Permethrin also bioconcentrates in aquatic insects; bioconcentration factors in stoneflies ranged from 43 to 570.

Fish: Permethrin is highly toxic to fish. This toxicity is due, in part, to the sensitivity of their nervous system. Fish also lack the enzymes that break down permethrin in other animals. Permethrin bioconcentrates in fish, so that concentrations in fish are higher than the concentration in the water in which the fish live. Bioconcentration factors (the ratio between the concentration in the fish and the concentration in the water) up to 113 have been measured in brook trout, 59 up to 613 in Atlantic salmon, 59 and up to 631 in rainbow trout.