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New Research Confirms Neurotoxicity of Pesticide Synergist PBO

(Beyond Pesticides, June 15, 2012) Researchers at the Duke University School of Medicine have developed a laboratory screening system for detecting neurotoxic chemicals and successfully tested it on more than 1,400 potential toxicants. The study confirms the high toxic activity of the chemical piperonyl butoxide (PBO), a chemical “synergist” used to increase the potency of more than 700 insecticides, including synthetic pyrethroids widely used in mosquito and community spray programs and for home use. The study, entitled “The Insecticide Synergist Piperonyl Butoxide Inhibits Hedgehog Signaling: Assessing Chemical Risks,” was published in the May 2012 edition of the journal Toxicological Sciences.

The testing shows that PBO disrupts a biological signaling system that is “critical in neurological development,” the researchers reported in the abstract of their paper. The study finds that the disruption of this critical pathway “may be the molecular basis for profound developmental defects in children exposed in utero to PBO.”

Piperonyl butoxide is not itself classified as a pesticide, but companies combine it with insecticides to increase their potency. PBO came into widespread use when the U.S. Environmental Protection Agency (EPA) phased out chlorpyrifos and other organophosphate pesticides nearly a decade ago after determining that they posed a risk to children’s health. As with many so-called “inert” ingredients, pesticide products often contain five to ten times more PBO than the active ingredient in the formulation. PBO is listed among the top 10 chemicals detected in indoor dust, often a significant route of exposure to children.

“We were concerned when our study confirmed that PBO disrupted neurological development pathways – especially given the widespread use of this chemical in American homes,” said Wei Chen, PhD, assistant professor at the Duke School of Medicine and an author of the new study. “Our study demonstrates the need for additional research and evaluation of the safety profile of PBO as a pesticide synergist and the value of high- throughput screening in assessing the potential toxicity of chemicals.”

Similar research published last year in the journal Pediatrics shows that children exposed to higher amounts of pyrethroid insecticides and PBO 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 at three years of age. Children with the highest prenatal exposures scored about 4 points lower on the test.

The Environmental Working Group has compiled a list of common household insecticide products that, among others, contain PBO:

• Raid Commercial Flying Insect Killer
• Raid Indoor Fogger Formula IV
• Raid Flea Killer Plus
• Black Flag Flying Insect Killer
• Ritter’s flea & Tick Spray
• Ortho Tomato & Vegetable Insect Killer
• Bonide Mosquito Insect Spray
• Terro Insect Killer
• Terro Carpenter Ant and Termite Killer

For more information on the many ways in which pesticides affect human health, see Beyond Pesticides’ Pesticide Induced Diseased Database.

All unattributed positions and opinions in this piece are those of Beyond Pesticides.


One Response to “New Research Confirms Neurotoxicity of Pesticide Synergist PBO”

  1. 1
    Don Hoernschemeyer Says:

    Thanks for your continued great work. I’ve often wondered about such synergists and “inert ingredients.”

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