Boys appear to be more vulnerable than girls to the insecticide chlorpyrifos

August 8, 2012

A new study is the first to find a difference between how boys and girls respond to prenatal exposure to the insecticide chlorpyrifos. Researchers at the Columbia Center for Children's Environmental Health (CCCEH) at the Mailman School of Public Health found that, at age 7, boys had greater difficulty with working memory, a key component of IQ, than girls with similar exposures. On the plus side, having nurturing parents improved working memory, especially in boys, although it did not lessen the negative cognitive effects of exposure to the chemical.

Results are published online in the journal .

In 2011, research led by Virginia Rauh, ScD, Co-Deputy Director of CCCEH, established a connection between prenatal exposure to chlorpyrifos and deficits in and IQ at age 7. Earlier this year, a follow-up study showed evidence in that even low to moderate levels of exposure during pregnancy may lead to long-term, potentially irreversible changes in the brain. The latest study, led by Megan Horton, PhD, explored the impact of and the home environment on these .

Dr. Horton and colleagues looked at a subset of 335 mother-child pairs enrolled in the ongoing inner-city study of , including measures of prenatal chlorpyrifos in umbilical cord blood. When the children reached age 3, the researchers measured the home environment using the Home Observation for Measurement of the Environment (HOME) criteria, including two main categories: 1) environmental stimulation, defined as the availability of intellectually stimulating materials in the home and the mother's encouragement of learning; and 2) parental nurturance, defined as attentiveness, displays of physical affection, encouragement of delayed gratification, limit setting, and the ability of the mother to control her negative reactions. The researchers tested IQ at age 7.

While home environment and sex had no moderating effect on IQ deficits related to chlorpyrifos exposure, the researchers uncovered two intriguing findings related to sex differences, albeit of borderline statistical strength: first, that chlorpyrifos exposure had a greater adverse cognitive impact in boys as compared to girls, lowering working memory scores by an average of three points more in boys than girls (96.5 vs. 99.8); and second, that parental nurturing was associated with better working memory, particularly in boys.

"There's something about boys that makes them a little more susceptible to both bad exposures and good exposures," says Dr. Horton. "One possible explanation for the greater sensitivity to chlorpyrifos is that the insecticide acts as an endocrine disruptor to suppress sex-specific hormones. In a study of rats, exposure to the chemical reduced testosterone, which plays a critical role in the development of the male brain."

Going forward, Dr. Horton will look at how sex and the may influence the effects of to other environmental toxicants, such as those found in air pollution. "I expect this information will be useful in efforts to develop new interventions to protect children from the potentially negative consequences of early exposure to harmful chemicals," says Dr. Horton.

The insecticide chlorpyrifos was widely used in homes until 2001 when the U.S. Environmental Protection Agency restricted indoor residential use, permitting continued commercial and agricultural applications. Since that time, a drop in residential levels of chlorpyrifos has been documented by Robin Whyatt, DrPH, Co-Deputy Director of CCCEH. The chemical continues to be present in the environment through its widespread use in agriculture (food and feed crops), wood treatments, and public spaces such as golf courses, some parks, and highway medians. People near these sources can be exposed by inhaling the chemical, which drifts on the wind. Low-level exposure can also occur by eating fruits and vegetables that have been sprayed with chlorpyrifos. Although the chemical is degraded rapidly by water and sunlight outdoors, it has been detected by the Columbia researchers in many urban residences several years after the ban went into effect. Many developing countries continue to use in the home setting.

Explore further: Pesticide exposure linked to brain changes: study

Related Stories

Pesticide exposure linked to brain changes: study

April 30, 2012
When pregnant women are exposed to moderate levels of a common pesticide, their children may experience lasting changes in brain structure linked to lower intelligence, a US study said Monday.

Prenatal pesticide exposure tied to lower IQ in children

April 21, 2011
(PhysOrg.com) -- In a new study suggesting pesticides may be associated with the health and development of children, researchers at the University of California, Berkeley's School of Public Health have found that prenatal ...

Prenatal exposure to phthalates linked to decreased mental and motor development

September 6, 2011
A newly published study by researchers at Columbia University's Mailman School of Public Health heightens concerns over the potential health effects on children of a group of ubiquitous chemicals known as phthalates. Phthalates ...

Recommended for you

Higher manganese levels in children correlate with lower IQ scores, study finds

September 21, 2017
A study led by environmental health researchers at the University of Cincinnati (UC) College of Medicine finds that children in East Liverpool, Ohio with higher levels of Manganese (Mn) had lower IQ scores. The research appears ...

Researchers see popular herbicide affecting health across generations

September 20, 2017
First, the good news. Washington State University researchers have found that a rat exposed to a popular herbicide while in the womb developed no diseases and showed no apparent health effects aside from lower weight.

One e-cigarette with nicotine leads to adrenaline changes in nonsmokers' hearts

September 20, 2017
A new UCLA study found that healthy nonsmokers experienced increased adrenaline levels in their heart after one electronic cigarette (e-cigarette) with nicotine but there were no increased adrenaline levels when the study ...

Higher levels of fluoride in pregnant woman linked to lower intelligence in their children

September 20, 2017
Fluoride in the urine of pregnant women shows a correlation with lower measures of intelligence in their children, according to University of Toronto researchers who conducted the first study of its kind and size to examine ...

India has avoided 1 million child deaths since 2005, new study concludes

September 19, 2017
India has avoided about 1 million deaths of children under age five since 2005, driven by significant reductions in mortality from pneumonia, diarrhea, tetanus and measles, according to new research published today.

Gulf spill oil dispersants associated with health symptoms in cleanup workers

September 19, 2017
Workers who were likely exposed to dispersants while cleaning up the 2010 Deepwater Horizon oil spill experienced a range of health symptoms including cough and wheeze, and skin and eye irritation, according to scientists ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

sdsavage
not rated yet Aug 10, 2012
Just for perspective, I looked at the most recent USDA-AMS pesticide detection program (PDP) data for chlorpyrifos. Of the 12,455 food samples tested for that chemical, 97.1% had no detectible chlorpyrifos residues. 1.6% had between 1 and 10 parts per billion. 0.7% had between 10 and 100 ppb. and 0.24% had between 100 and 1000 ppb. No samples were over 1 part per million.

It is good that the in-home uses of chlorpyrifos were ended, but the agricultural use (though declining) is not a significant route of exposure

Steve Savage, Ph.D.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.