Can polluted air cause birth defects?

Scientists have found new evidence that prenatal exposure to air pollution may cause congenital heart defects. However, inconsistencies with past results make the finding less than definitive, the researchers say.

Epidemiologist Pauline Mendola of the Environmental Protection Agency in Research Triangle Park, N.C., and her collaborators compared pollution statistics and records of births between 1997 and 2000 in seven Texas counties. The researchers focused on the quality of the air that women were breathing during their first 2 months of pregnancy, which a 2002 study in California had linked to certain congenital defects of the heart, lip, and palate.

In Texas, women who'd been exposed early in their pregnancies to relatively high concentrations of carbon monoxide, sulfur dioxide, or particulate matter were more likely than other women to have babies with certain heart defects. As the California study had, the new report identified a tentative link between ozone exposure and defects in the pulmonary arteries, which connect the heart and lungs.

By and large, however, the new study correlates different pollutants and heart defects than the California study did. Furthermore, pollutants don't appear to be associated with cleft lip or cleft palate, Mendola's team reports in the Aug. 1 American Journal of Epidemiology. "We did not find the same [associations] that they did in California, but we found other things," Mendola says.

Discrepancies aside, the new study strengthens the hypothesis that pollution and birth defects are linked, comments epidemiologist Gary M. Shaw of the California Birth Defects Monitoring Program in Berkeley, who participated in the earlier California study.