Chlorpyrifos: The Cockroach-Killing Chemical That Harms Boys' Brains More Than Girls'

Chlorpyrifos is one of the most widely used pesticides in the U.S.

(Photo: Andrea Bernardro/Getty Images via Flickr)
The director of the Public Trust Project, Alison has written for Grist and Politics Daily, among others.

A common pesticide used in agriculture harms the developing brains of boys more than girls, according to a new study

Researchers at Columbia University found that exposure to chlorpyrifos in the womb was associated with lower I.Q. scores in boys at age seven than their female counterparts.

Chlorpyrifos is one of the most widely used pesticides in the United States—10 million pounds are applied annually to a wide range of crops, parks, and golf courses to keep insects at bay.

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Previously, chlorpyrifos was also approved for use in homes and gardens to kill cockroaches, and was a routine ingredient in many insecticides on the market to control ticks, fleas, ants, spiders, and more.

In 2001, the Environmental Protection Agency banned the sale of chlorpyrifos for use in homes because of mounting evidence that the chemical posed unnecessary health risks to children.

But scientists have continued to identify residues of chlorpyrifos in residences in the U.S. In some developing countries, it is still used indoors, where it can’t easily be broken down by sunlight or water, according to reporting by Environmental Health News.

Ample research has demonstrated that children who were exposed to chlorpyrifos in the womb have lower IQ scores and worse memories than children who did not suffer exposures. But these latest findings from Columbia University represent the first time scientists have identified differences in how boys and girls respond to prenatal exposure to chlorpyrifos.   

The study, published in July in Neurotoxicology and Teratology, followed 335 pairs of mothers and children from low-income neighborhoods in New York City as part of an ongoing effort to examine the effects of ordinary chemicals on public health outcomes.

Researchers tested umbilical cord blood when the children were born, social and environmental factors when the children were three years old, and at seven, analyzed the participants’ short-term memory skills, a key component of IQ. 

The study found that boys had short-term memory scores that were three points lower, on average, than girls with similar exposures to chlorpyrifos. 

Why boys are disproportionately affected is not entirely clear.  

“One possible explanation for the greater sensitivity to chlorpyrifos is that the insecticide acts as an endocrine disruptor to suppress sex-specific hormones,” Dr. Megan Horton, the study’s lead author, told ScienceDaily. “In a study of rats, exposure to the chemical reduced testosterone, which plays a critical role in the development of the male brain.” 

At present, agricultural workers are most at risk for chlorpyrifos exposure. To mitigate potential exposures, the EPA recommends that farmworkers wear double layered clothing and chemical-resistant gloves and shoes.

Meanwhile, the public interest law firm EarthJustice is suing the EPA to ban all remaining uses of chlorpyrifos, according to Environmental Health News, and the agency has plans to reevaluate the chemical, with a final decision expected in 2014.

How worried are you about chlorpyrifos? Be honest, had you ever heard of it before this article? Tell us in the comments.

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