Exposure to urban air pollution can affect the chromosomes of a developing fetus, a new study suggests. Babies born to mothers exposed to high levels of urban air pollution appear to have a greater chance of chromosomal abnormalities than those whose mothers breathed cleaner air.

Frederica P. Perera of the Columbia Center for Children's Environmental Health and her colleagues studied 60 infants born in New York City to nonsmoking mothers who were participating in an ongoing study that started in 1998. The team analyzed exposure rates to airborne pollutants known as polycyclic aromatic hydrocarbons (PAH)--which are present in vehicle exhaust, power plant emissions and tobacco smoke--in three low-income areas. "Although the study was conducted in Manhattan neighborhoods, exhaust pollutants are prevalent in all urban areas, and therefore the study results are relevant to populations in other urban areas," Perera notes.

The mothers-to-be filled out questionnaires and wore a portable air monitor for 48 hours during their third trimester. After the women gave birth, the scientists analyzed samples of umbilical cord blood and tested for chromosomal abnormalities. The team found that exposure to combustion pollutants was positively linked to chromosomal abnormalities in fetal tissue: newborns in the low-exposure group exhibited 4.7 abnormalities per thousand white blood cells. Babies born to mothers in the highest exposure group had 7.2 abnormalities per thousand cells.

"This evidence that air pollutants can alter chromosomes in utero is troubling since other studies have validated this type of genetic alteration as a biomarker of cancer risk," Perera remarks. "While we can't estimate the precise increase in cancer risk, these findings underscore the need for policymakers at the federal, state and local levels to take appropriate steps to protect children from these avoidable exposures." The findings appear in the current issue of the journal Cancer Epidemiology Biomarkers and Prevention.