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Study Links Prenatal Exposure to Pyrethroid Insecticides and Learning Problems

(Beyond Pesticides, February 8, 2011) Research published February 7, 2011 in the online edition of the journal Peditatrics shows that children more highly exposed to pyrethroid insecticides and piperonyl butoxide (PBO), a synergist added to increase the potency of pyrethroids, are three times as likely to have a mental delay compared to children with lower levels. The study, “Impact of Prenatal Exposure to Piperonyl Butoxide and Permethrin on 36-Month Neurodevelopment,” measured exposure to pesticides using maternal and umbilical cord plasma samples and in personal air samples, collected using backpack air monitors during pregnancy. Children were then tested for cognitive and motor development (using the Bayley Scales of Infant Development) at three years of age. Children with the highest prenatal exposures scored about 4 points lower on the test.

That’s about the same intelligence loss caused by lead, Philip Landrigan, MD, a pediatrics professor and environmental health expert at New York’s Mount Sinai School of Medicine, told USA Today. Pyrethroid pesticides kill bugs by “being toxic to the developing brain,” Dr. Landrigan says. The results are “very believable and should be taken seriously.”

Pyrethroid pesticides have increased in popularity over the past decade due in large part to the phase-out of most residential uses of once-popular organophosphate insecticides, which were removed from the market because of concerns of neurotixicity and children’s health. However, pyrethroid insecticides are potential neurodevelopmental toxicants, but have not been widely evaluated for developmental toxicity. The researchers’ objective was to explore the association between prenatal exposure to permethrin, a commonly used pyrethroid insecticide for termites, ants and other household insects, and neurodevelopment at three years of age. They measured PBO rather than permethrin, which breaks down too quickly to give reliable data.

Synthetic pyrethroids are chemically formulated versions of the natural-based pesticide pyrethrum, made from extracts from plants in the chrysanthemum family. A widely used class of insecticides, synthetic pyrethroids are designed to be more toxic and longer lasting than pyrethrum, and therefore are more potent to insects and pose elevated risks to humans. Exposure to synthetic pyrethroids has been reported to lead to headaches, dizziness, nausea, irritation, and skin sensations. EPA classifies permethrin as a possible human carcinogen. Many synthetic pyrethroids have been linked to disruption of the endocrine system, which can adversely affect reproduction and sexual development, interfere with the immune system, and increase chances of breast cancer. Synthetic pyrethroids have also been linked to respiratory problems such as hypersensitization, and may be triggers for asthma attacks.

Rather than use pesticides, lead author Megan Horton, PhD, a postdoctoral research fellow at Columbia University’s Mailman School of Public Health, suggests that parents utilize common-sense measures to control pests, such as eating only in home eating areas, not bedrooms; keeping cracks and crevices in the house repaired to keep out pests; using trash cans with a lid and liner to contain garbage; and, storing food properly.

For more information on permethrin, see the Pesticide Gateway. For least toxic methods for controlling household insects, see Beyond Pesticides’ “Have a Pest Problem?” webpage.


One Response to “Study Links Prenatal Exposure to Pyrethroid Insecticides and Learning Problems”

  1. 1
    Deb Bechtel Says:

    Another exposure route parents need to be alert for is automatic pesticide dispensers! In the tourist town of Morro Bay, CA, I UNKNOWINGLY parked my 2 week old grandson’s pram under a dispenser outside a toy shop at a small indoor mall while my daughter went in. A month later the shop clerk (friend of daughters) asked me about pesticides because she was ill and thought it was caused by the pesticide dispenser. I WAS FURIOUS! Permethrin released at 15 minute intervals because the mall owner is too cheap to install fans to keep flies out!? The owner said “It’s only Pyrethrins….like chrysanthemums.” That’s the lie the salesman told him. It was Permethrin. And over the toy shop door where children are exposed!

    LOOK UP on walls near doorways, in shops and in public areas! They are often plastic and the size of a thermos bottle. They are mounted outside our normal range of vision. WARNINGS should be posted!

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