Brain delay: air pollutants linked to slow childhood mental development.

Pollutants spewing from vehicles and power plants may be harmful to fetal brains, new evidence suggests. The study is the first to directly link delayed cognitive development in children to their mothers' exposure during pregnancy to common air pollutants called polycyclie aromatic hydrocarbons, or PAHs.

Earlier studies established a similar relationship between slowed neurological development and prenatal exposure to lead, says Frederica P. Perera, the Columbia University environmental health scientist who led the new study.

Last year, other researchers reported that secondhand cigarette smoke may also dull kids' wits (SN: 1/15/05, p. 37). Such smoke also contains PAHs.

"These pollutants come largely from combustion of fossil fuels, including gasoline, diesel, and coal," Perera says. PAHs come in hundreds of chemical varieties, at least some of which are carcinogenic.

For their study, Perera and her colleagues first outfitted several hundred pregnant women with air-quality monitors that fit into small backpacks. The volunteers lived in upper Manhattan and the Bronx, N.Y. For 2 days, the monitors measured eight kinds of PAHs in the air surrounding each woman.

The researchers tested blood from mothers and infants after delivery and then annually tested each child's cognitive abilities.

They also recorded each child's birthweight and other measurements and assessed each mother's exposure to lead and secondhand smoke, her marital status, and other factors that can affect a child's development.

In a previous phase of the study, Perera's team had concluded that women who breathed high concentrations of PAHs during pregnancy were more likely than other women to have children with low birthweights or reduced fetal growth.

For their new report in an upcoming Environmental Health Perspectives, the team analyzed data on 183 children who had reached the age of 3.

By that age, the 42 children whose mothers had been exposed to the most PAHs "scored significantly less well on a test of cognitive development" than did the rest of the children in the group, Perera says. The youngsters of highly exposed mothers "were more than twice as likely to be developmentally delayed, according to this test," she adds.

The well-designed study took many, though not all, possible developmental factors into account before attributing any effect to PAHs, says developmental psychologist Philip Sanford Zeskind of Carolinas Medical Center in Charlotte, N.C. While pregnant women can take simple steps to avoid some harmful exposures, including cigarette smoke, "people don't have many choices" when it comes to avoiding ambient air pollutants such as PAHs, he says.

"This study offers clear evidence of a detrimental effect of prenatal exposure [to PAHs] on child cognitive development," comments Kimberly Yolton of Cincinnati Children's Hospital Medical Center. She adds that it "should encourage us to think creatively about ways in which we can reduce this exposure for pregnant women and young children;'

Perera proposes that "better pollution controls on what comes out of tailpipes or smokestacks" PAH concentrations could be cut by public-policy measures that, for example, reduce power plant emissions overall or replace old, diesel-burning buses with vehicles that are either more fuel efficient or that don't burn fossil fuels, she says.