Women who breathe air heavily polluted with ozone are at particular risk for having babies afflicted with intra uterine growth retardation-which means babies only fall within the 15th percentile of their expected size. The findings were published early online on the Web site of Environmental Health Perspectives, the journal of the National Institute for Environmental Health Sciences (NIEHS).
"These findings add further evidence that our ozone standards are not protecting the most vulnerable members of the population," says Frank D. Gilliland, M.D., Ph.D., professor of preventive medicine at the Keck School and the study's senior author.
Gilliland and his colleagues examined birth records from 3,901 children who were born in California between 1975 and 1987 and participated in the Children's Health Study. Researchers with the USC-led Children's Health Study have monitored levels of major pollutants in a dozen Southern California communities since 1993, while following the respiratory health of more than 6,000 students in those communities.
The researchers gathered data such as the children's gestational age and birth weight, as well as their mothers' zip code of residence at birth. Then they determined levels of ozone, carbon monoxide and other pollutants in the air in each zip code of residence during each mother's pregnancy. Researchers only considered full-term births for the study and controlled for factors such as mothers' smoking habits.
They found that each increase of 12 parts per billion (ppb) of average daily ozone levels over a mother's entire pregnancy was associated with a drop of 47.2 grams (g)-about a tenth of a pound-in a baby's birth weight. And the association w
Contact: Kathleen O'Neil
University of Southern California