Could air pollution be undermining our intelligence?

Mom’s pollution exposure may lower baby’s IQ

Paul Taylor

Last updated on Friday, Jul. 24, 2009 10:03AM EDT

Could air pollution be undermining our intelligence?

In the first study of its kind, U.S. researchers have found a link between pregnant women being exposed to air pollution and lower IQs of their children.

"This is a warning bell," said the lead author of the study, Frederica Perera, director of the Columbia Center for Children’s Environmental Health in New York.

"We need to pay greater attention to this vulnerable window … when the developing fetal brain is extremely sensitive to many different neurotoxic substances."

The findings are based on 249 children of mothers who live in low-income neighbourhoods of the south Bronx and northern Manhattan.

For a 48-hour period during their pregnancies, the mothers wore air monitors that measured pollutants known as polycyclic aromatic hydrocarbons or PAHs. These chemicals are produced by burning coal, diesel, oil and gas. Tobacco is another source of PAHs, although the women in the study were all non-smokers.

At the age of 5, the children were given intelligence quotient tests. The study showed that the children of mothers exposed to the highest level of PAHs had IQ scores that were between 4.3 and 4.6 points lower than kids whose moms had the least pollution exposure.

Dr. Perera said the lower IQs scores were similar to the effects of low levels of lead, another toxin that can hinder normal mental development.

The study, published in the journal Pediatrics, took into account other factors that may have influenced the children’s IQ scores, such as exposure to second-hand smoke, mother’s education and the quality of the home environment for learning.

Although the findings need to be confirmed with additional research, Dr. Perera said, it’s worrisome that typical levels of urban pollution may have lifelong consequences on a developing fetus.

"The major source of pollution was traffic – diesel and gasoline-powered trucks, buses and automobiles," she said, noting the families lived relatively far from smoke-spewing power plants and large coal-burning factories.

"These levels are relatively low and they are really comparable with what would be found in many urban areas across the U.S. and I expect in Canada, as well."

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