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by Shelly Connor — last modified Apr 11, 2014 01:58 PM
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Information on daily exposure to pyrethroid chemicals

Pyrethroids: The Poisons we Keep Closest to Home

A study recently published by Environmental Science & Technology instills concern over pyrethroid insecticides, which are used globally in more than 3,500 commercial products. Pyrethroids, a potent neurological disruptor, were found in two-thirds of adults, children and homes tested, according to the recent study conducted by University of California, Davis researchers. Furthermore, a study, published previously in 2010, revealed a similar exposure rate of around 70%, the highest rate of exposure being found in children.

Replacing previously discontinued organophosphate pesticides for residential application, use of pyrethroid insecticides claimed to offer a solution to pest management while being virtually benign to human health. Pesticide products containing pyrethroids are often described as “safe as chrysanthemum flowers” (being a chemically engineered extract from the chrysanthemum plant). Available information on pyrethroid toxicity and risks of exposure, however, might be enough to question their safety and potentially compel further research.


Pyrethroids are the most frequently used insecticide in the U.S., with both home and garden applications as well as use in agriculture.  Common pyrethroid insecticides are used in indoor sprays, pet shampoos, aerosol bombs and crop treatments. Pyrethroids are a synthetic chemical, similar to the pyrethrin extract made from chrysanthemum flowers, which have been modified to increase potency, toxicity, and persistence.

They are an excitatory nerve poison that, acting upon the sodium ion channels in nerve cell membranes, kills insects through repetitive discharges in their nerve impulses leading to paralysis and death. Though humans and other mammals have enzymes that detoxify pyrethroids from paralyzing the nervous system like they would an insect’s, mammals are still susceptible to pyrethroid poisoning.

In 1991, the EPA summarized the reported incidents of pyrethroid related incidents to over 9,000—only organophosphate insecticides, pyrethroid’s precursor, were the cause of more incidents (over 15,000).

Pyrethroid toxicity can range anywhere from unpleasant to life-threatening depending on an individual’s reaction to the chemical. Skin rashes, asthma, hives, and eye irritation are some examples of low-level reactions. In one case, physicians in New York reported that a woman suffered from heart failure roughly five minutes after beginning to wash her dog with pyrethrin shampoo. A similar case reported an 11 year-old girl died only a few hours after developing a severe asthmatic attack from a pyrethrin shampoo as well.

There are also concerns of the long-term impacts of pyrethroid exposure. Research done on the effects of pyrethroids on the circulatory system reveal that exposure can cause a dramatic rise in blood sugar as well as a decrease in the amount of hemoglobin in the blood, in a test conducted with gerbils. The study also found that hemoglobin levels remained low for 2-3 weeks after exposure. Pyrethrins are also successful in disrupting reproductive hormones in humans and mammals. A study conducted with dairy cows revealed that the milk of cows, following pyrethroid treatment, had detectable levels of pyrethroids—providing support for the concern that nursing mothers can expose their children.

Aside from mammals, pyrethroid exposure has negative effects on birds, fish and other aquatic animals, beneficial insects, and honeybees as well. Pyrethrins are so toxic to bees that only .02 micrograms is sufficient to kill them.


Simply employing an alternative method of pest control can mitigate exposure to pyrethroids and their potential health risks. A large number of incidents of pesticide poisonings occur by neglect for best management practices. One of the most sustainable and comprehensive means of pest control is called integrated pest management (IPM).  Universities, databases, action-groups, and various blogs and websites can offer many resources for the best IPM practices.


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