Study: In Utero Exposure To Urban Air Pollutants Can Affect Cognitive Development

Prenatal exposure to air pollutants in New York City can adversely affect child development, according to the results of a study by the Columbia Center for Children's Environmental Health (CCCEH) at Columbia University's Mailman School of Public Health.

Previous studies have shown that the same air pollutants can reduce fetal growth (both weight and head circumference at birth), but this study, which examined a group of the same children at three years of age, is the first to reveal that those pollutants can also affect cognitive development during childhood.

The study was published online April 24 in Environmental Health Perspectives and can be accessed at: http://www.ehponline.org/docs/2006/9084/abstract.html.

Investigators at the Center studied a sample of 183 three-year-old children of non-smoking African-American and Dominican women residing in the neighborhoods of Washington Heights, Central Harlem, and the South Bronx. They found that exposure during pregnancy to combustion-related urban air pollutants known as polycyclic aromatic hydrocarbons (PAHs) were linked to significantly lower scores on mental development tests and more than double the risk of developmental delay at age three.

Prenatal PAH exposures averaged 3.49 nanograms per cubic meter (ng/m3), with a range of 0.65 ng/m3 to 36.47 ng/m3. The infants who had been exposed prenatally to the highest PAH levels (upper quartile) scored significantly lower on a mental development index at age 3 than those with lower levels of PAH exposure. Such delay in cognitive development is indicative of greater risk for performance deficits in language, reading, and math in the early school years.

In the study, the mothers' exposure during pregnancy to varying levels of airborne PAHs was measured by personal air monitoring. PAHs enter the environment when combustion occurs -- such as from car, truck, or bus engines, residential heating, power generation, or tobacco smoking. Following inhalation by the mother, the pollutants can be transferred across the placenta to reach the fetus. Children were tested at age three using a standardized test of mental and psychomotor development.

The study is part of a broader multi-year research project. "The Mothers and Children Study in New York City," started in 1998, which examines the health effects of exposure of pregnant women and babies to indoor and outdoor air pollutants, pesticides and allergens.

"These findings are of concern, because compromised mental performance in the preschool years is an important precursor of subsequent educational performance deficits," said Dr. Frederica Perera, DrPH, director of the Center and lead investigator (http://www.mailman.hs.columbia.edu/ehs/15.html). "Fortunately, airborne PAH concentrations can be reduced by currently available pollution controls, greater energy efficiency, and the use of alternative energy sources."

"Identifying and attending to developmental delays in the preschool years is likely to be cost-effective and improve cognitive development," said Dr. Virginia Rauh, ScD, co-investigator and co-author of the study, "since the skills children bring with them to school not only affect educational outcomes but also determine how schools must spend their resources."

In this study, the children who were exposed in the womb to the highest levels of PAHs scored on average 5.7 points (6.3 percent) lower on cognitive tests than the less exposed children; and their risk of being developmentally delayed was 2.9-times greater than that of children who had lower prenatal exposure; both results were statistically significant.

The investigators controlled for other exposures that might have contributed to developmental problems such as socioeconomic factors, exposure to tobacco smoke, lead, and other environmental contaminants.

This article originally appeared in the 04/01/2006 issue of Environmental Protection.

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