Mailman researchers: insecticides may lower IQs

Household insecticides don’t just smell bad—they may cause adverse developmental effects in young children, according to a new study by researchers with the Mailman School of Public Health.
IQ scores of children at age three were approximately four points lower than average among children who had high exposure during pregnancy to piperonyl butoxide (PBO), an additive used in pyrethroids, a common class of insecticides.
“It is a very significant drop when you think about it in terms of shifting the distribution of IQ scores in a community,” Dr. Megan Horton, the lead researcher on the study, said.

Horton compared the effect to low-level lead exposure, and noted that it could be sufficient to shift the lower end of IQ scores into “an IQ category that may need special services.”

According to Dr. Robin Whyatt, one of the study’s authors and a deputy director of the Columbia Center for Children’s Environmental Health, studying these effects is important because pyrethroid insecticides are increasingly used as replacements for organophosphates, a class of insecticides that was regulated by the Environmental Protection Agency in 2001 following similar evidence of risks from prenatal exposure.

Although the results of the study are preliminary, the researchers recommend that pregnant women and those with young children avoid the use of spray pesticides.

“It’s prudent to avoid these exposures to the extent possible, if there’s any possibility that they may be causing harm,” Whyatt said.

The study, published in the March issue of the journal “Pediatrics,” was conducted by equipping a group of pregnant mothers from upper Manhattan and the South Bronx with backpack air monitors that detect traces of PBO in the surrounding air. It was the first study to examine potential adverse effects of pyrethroid insecticides in humans.

According to Horton, this type of insecticide is found in all household sprays, including those which kill ants or cockroaches, as well as in compounds used by professional exterminators.

Horton noted that the greatest density of spray insecticide use has been found in highly urban areas, especially in poorer areas with lower-quality housing which tend to experience more severe insect problems.

“We’ve actually worked with the New York City Housing Authority to try to move away from spraying,” Horton said.

Instead, researchers are focusing on using different pest-management techniques in city-owned buildings, such as sealing cracks, keeping trash contained, and employing traps, gels, and other lower-toxicity insecticides.

“It’s hard to just leave women with the message that using pesticides is bad, so you have to live with cockroaches,” Horton said. “That’s not very fair to say, and so it’s very nice that we have some clear research showing that integrated pest management can be effective.”

Horton and Whyatt both emphasized the need for further research in order to determine if the neurological effects persist in children beyond three years, and to discover whether the adverse effects come from the insecticides themselves or just the proxy compound used in the study.

henry.willson@columbiaspectator.com