Size in the city: New York pollution may lower birth weight. (Science Selections).

Current levels of environmental pollutants in New York City can adversely affect fetal development, according to a new study by a team led by Frederica Perera of Columbia University's Center for Children's Environmental Health [EHP 111:201-205]. The study found a significant link between prenatal exposure to common environmental pollutants--including the combustion by-products polycyclic aromatic hydrocarbons (PAHs) and the once widely used organophosphate pesticide chlorpyrifos--and reduced birth weight and head circumference in two inner-city minority populations. (In recent years, the U.S. Environmental Protection Agency has regulated chlorpyrifos, and residential uses are being phased out.)

The researchers monitored more than 260 black and Dominican women during their pregnancies and collected biological samples from each mother and baby at delivery. During pregnancy, the mothers wore personal air monitors to gauge their exposure to eight airborne carcinogenic PAHs. The team used plasma levels of chlorpyrifos to estimate exposure to this pesticide and plasma levels of cotinine to estimate environmental tobacco smoke exposure (all of the mothers were nonsmokers). The team's approach combined use of biomarkers with epidemiologic methods. This is the first study to use prenatal personal air monitoring and biomarkers to assess the effects of these particular prenatal exposures on birth outcomes.

The team found that median exposure to chlorpyrifos during pregnancy was associated with a 4% decrease in birth weight and a 2% decrease in birth length in the overall cohort. They also found that median exposure to PAHs during pregnancy was associated with a 9% reduction in birth weight and a 2% reduction in head circumference in black newborns. No significant reductions were noted in Dominicans. In addition, the study linked prenatal exposure to chlorpyrifos with decreased birth weight and birth length in both black and Dominican infants. The mechanism for these agents' observed effects on fetal growth and development is not known. There was no significant effect correlated with environmental tobacco smoke, possibly because all the mothers are themselves nonsmokers.

In previous studies of mothers and newborns in Krakow, Poland, the researchers had found associations between these same birth outcomes and PAH exposure. However, the Polish population was exposed to 46% higher concentrations of PAHs than the present New York City cohort due to air pollution from coal burning. The fact that the New York City effects were seen at lower concentrations is of concern, according to Perera, because several studies have reported that reduction in head circumference at birth or during the first year of life correlates with lower IQ and poorer cognitive functioning and school performance in childhood.

The lack of an association between PAH exposure and adverse effects in the Dominican newborns may be due to unmeasured differences in exposure and susceptibility, the researchers speculate. The fact that birth outcomes such as weight, head circumference, and age of fetus at delivery were overall less favorable and more variable in blacks compared to Dominicans could also explain the difference. The authors are evaluating whether genetic and other susceptibility factors influence risk from these exposures.