Children's IQ Degraded By Mothers' Exposure to Air Pollutants

PAHs are chemicals emitted by the burning of coal, diesel, oil and gas, or other organic substances such as tobacco. In cities, motor vehicles are a major source of PAHs.

The study found that children exposed to high levels of PAHs in New York City had full scale and verbal IQ scores that were 4.31 and 4.67 points lower, respectively, than those of less exposed children.

"The decrease in full-scale IQ score among the more exposed children is similar to that seen with low-level lead exposure," says lead author Frederica Perera, DrPH, professor of environmental health sciences and director of the Columbia Center for Children's Environmental Health.

"This finding is of concern because IQ is an important predictor of future academic performance, and PAHs are widespread in urban environments and throughout the world," she said.

Air pollution on a New York City street June 2, 2009 (Photo by Kevin Tuhumury)

The study included children who were born to non-smoking Black and Dominican American women age 18 to 35 who lived in Washington Heights, Harlem or the South Bronx.

The children were followed from in utero to five years of age. The mothers wore personal air monitors during pregnancy to measure exposure to PAHs and they responded to questionnaires.

At five years of age, 249 children were given an intelligence test known as the Wechsler Preschool and Primary Scale of the Intelligence, which provides verbal, performance and full-scale IQ scores.

The researchers developed models to calculate the associations between prenatal PAH exposure and IQ.

They accounted for other factors such as second-hand smoke exposure, lead, mother's education and the quality of the home caretaking environment.

High PAH levels were defined as above the median of 2.26 nanograms per cubic meter (ng/m3) of air.

Study participants exposed to air pollution levels below the average were designated as having "low exposure," while those exposed to pollution levels above the average were identified as "high exposure."

A total of 140 children out of the 249 tested were classified as having high PAH exposure.

"The good news is," said Dr. Perera, "that we have seen a decline in air pollution exposure in our cohort since 1998, testifying to the importance of policies to reduce traffic congestion and other sources of fossil fuel combustion byproducts."

Airborne PAH concentrations can be reduced through currently available controls, alternative energy sources and policy interventions, she said.

Funded by the National Institute of Environmental Health Sciences, a component of the National Institutes of Health, the U.S. Environmental Protection Agency and several private foundations, the study findings are published in the August 2009 issue of the journal "Pediatrics."

Copyright Environment News Service, ENS, 2009. All rights reserved.