While the study results indicate that prenatal exposure to second-hand smoke can be harmful to the unborn child regardless of socioeconomic conditions, the data also suggest that lower-income children may be less able to compensate for these effects over the next few years of life. The study will appear in the March 2004 issue of the journal Neurotoxicology and Teratology.
The study, conducted by researchers at the Columbia Center for Children's Environmental Health, part of the Mailman School of Public Health at Columbia University, found that children whose mothers are exposed during pregnancy to second-hand smoke have reduced scores on tests of cognitive development at age two, when compared to children from smoke-free homes.
The reduction amounts to almost five developmental quotient points out of an average score of 100. In addition, the children exposed to second-hand smoke during pregnancy are approximately twice as likely to have developmental scores below 80, which is indicative of developmental delay.
These differences are magnified for children whose mothers lived in inadequate housing or had insufficient food or clothing during pregnancy. The combined effect results in a developmental deficit of about seven points in tests of cognitive performance.
While the influence of material hardship on the association between second-hand smoke and cognitive development was measured during the postnatal period, the test results show that the subjects' postnatal exposure to second-hand smoke does not confer any additional risk for developmental deficit over and above that contributed by prenatal exposure alone.
"These findings reveal the dangers for pregnant women and their unborn children of multiple 'toxic' exposures-both chemical and socioeconomic," said Dr. Virginia Rauh, a Deputy Director of the Center and Associate Professor at the Mailman School of Public Health and principal author of the study. "They show, for the first time, that urban children exposed to both conditions experience a kind of double jeopardy with consequences persisting into early childhood and possibly beyond."
The study is part of a broader, multi-year research project, "The Mothers & Children Study In New York City," started in 1998, which examines the health effects of exposure of pregnant women and babies to air pollutants from vehicle exhaust, the commercial burning of fuels, and tobacco smoking, as well as from residential use of pesticides, and cockroach and mouse allergens.
The research involved a sample of 226 infants of non-smoking African American and Dominican women in Washington Heights, Central Harlem and the South Bronx. Each of the women was interviewed during the third trimester of pregnancy, for approximately 45 minutes, by a specially trained bilingual interviewer.
From those interviews, data were obtained on their exposure to second-hand smoke, also known as Environmental Tobacco Smoke (ETS), and on their socioeconomic status and living conditions. The ETS exposure was further validated using a short-term biomarker of exposure: the level of cotinine in the umbilical cord blood at the time of delivery.
"This finding reinforces the need to prevent serious developmental problems in children by addressing harmful prenatal exposures," said Dr. Frederica P. Perera, Director of the Center and the study team leader. "From a health policy standpoint, it is important both to limit exposure to second-hand smoke and to better the living conditions of pregnant women and their children."
Other co-authors of this study include Drs. Robin Whyatt, Robin Garfinkel, Howard Andrews, Lori Hoepner, Andria Reyes, and Diurka Diaz of CCCEH and David Camann from Southwest Research Institute.
For more information or a copy of the study, please contact Heather Ross at 212-576-2700 x243.
Additional Contact: Dr. Gwen Collman 919-541-4980