www.safe2use.com/poisons-pesticides/pesticides/permethrin/cox-report/cox.htm(in part, need to read all of it)
PERMETHRIN
The insecticide permethrin (in the synthetic pyrethroid family) is widely used on cotton, wheat, corn, alfalfa, and other crops. In addition, over 100 million applications are made annually in and around U.S. homes.
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 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.
Permethrin has been found in streams and rivers throughout the United States. It is also routinely found on produce, particularly spinach, tomatoes, celery, lettuce, and peaches.
A wide variety of insects have developed resistance to permethrin. High levels of resistance have been documented in cockroaches, head lice, and tobacco budworm.
BY CAROLINE COX
Caroline Cox is JPR’s editor.
Permethrin is used to kill pest in-sects in agriculture, home pest control, forestry, and in public health programs, including head lice control. It was first marketed in 1973. Worldwide, the dominant use of permethrin is on cotton, accounting for about 60 percent (by weight) of the permethrin used.1 In the U.S., al-most 70 percent of the permethrin used in agriculture is used on corn, wheat, and alfalfa.2 Over 100 million applications of permethrin are made each year in U.S. homes, and over 18 million applications are made in yards and gardens.3
Permethrin is a synthetic pyrethroid. Like most members of this family of insecticides, it has four isomers, molecules made up of the same atoms with different three-dimensional structures. (See Figure 1)
Mode of Action
Permethrin, like all synthetic pyrethroids, kills insects by strongly exciting their nervous systems. Permethrin makes the nervous system hypersensitive to stimuli from sense organs. Rather than sending a single impulse in response to a stimulus, permethrin-exposed nerves send a train of impulses. This excitation occurs because permethrin blocks the movement of sodium ions from outside to inside of the nerve cells. Permethrin’s mode of action is similar to that of the organochlorine insecticide DDT.5
Neurotoxicity
In mammals, permethrin has complex effects on the nervous system. As in insects, it causes repetitive nerve impulses. It also inhibits a variety of nervous system enzymes: ATPase, whose inhibition results in increased release of the neurotransmitter acetylcholine 7; monoamine oxidase-A, the enzyme which maintains normal levels of three other neurotransmitters 8; and acetylcholinesterase, the enzyme that breaks down acetylcholine.9 (Two large families of insecticides, the organophosphates and the carbamates, are acetylcholinesterase inhibitors.) In addition, permethrin inhibits a nervous system receptor, the GABAA receptor, producing excitability and convulsions.10 Finally, permethrin inhibits respiration (the process by which cells use sugars as an energy source) in a manner similar to other neurotoxic drugs.11 It is therefore not surprising that permethrin causes a wide variety of neurotoxic symptoms.
At relatively high doses, these neuro-toxic symptoms of permethrin include tremors, incoordination, hyperactivity, paralysis, and an increase in body temperature. These symptoms can persist up to three days.12 Other behavioral effects have been observed at lower doses. For example, sublethal exposure of mice to the permethrin-containing insecticide Ambush increased activities like chewing 13 ; sublethal exposure of rats to permethrin increased aggressive behavior, agitation, and resistance to being captured 14 ; and permethrin disrupted a learned feeding behavior in rats at doses of about 20 percent of the LD50. 15
Acute Lethal Dose
Eye and Skin Irritation Effects on the Immune System
Effects on Reproduction
Mutagenicity
Carcinogenicity
Other Chronic Effects
Synergy
Individual Susceptibility
“ It appears children may be more sensitive to permethrin than adults. Permethrin is almost 5 times more acutely toxic to 8-day-old rats than it is to adult rats.”