Perera, F, V Rauh, WY Tsai, P Kinney, D Camann, D Barr, T Bernert, R Garfinkel, Y-H Tu, D Diaz, J Dietrich and RM Whyatt. 2002. Effects of Transplacental Exposure to Environmental Pollutants on Birth Outcomes in a Multi-Ethnic Population. Environmental Health Perspectives doi:10.1289/ehp.5742. [Online 31 October 2002].

In an innovative, community-based research project, Perera et al. discovered that "environmental pollutants at levels currently encountered in New York City adversely impact fetal development." Their work, focused on two inner-city minority populations and carried with the collaboration of community groups, examined the impact of polycyclic aromatic hydrocarbons (PAHs), environmental tobacco smoke (ETS) and an organophosphate pesticide (chlorpyrifos). They found effects linking elevated levels of the environmental contaminants to smaller birth weight and smaller head circumference. For the endpoints measured in people studied (all non-smokers) ETS had no effect.

What did they do? Perera et al. studied associations between exposure to PAHs, chlorpyrifos and ETS and birth outcome in pregnant African American and Dominican volunteers living in Dominican Heights, Central Harlem and South Bronx. A total of 263 women participated in the research. Active smokers were excluded from the study, as were women who reported not smoking but whose blood cotinine levels were high enough to suggest active smoking.

Perera et al. assessed exposure to the contaminants using a combination of 3 methods:

• The volunteers wore a small backpack containing air sampling equipment during two days in their third trimester of pregnancy. The sampled air was then analyzed for PAH levels by an independent laboratory.
• Umbilical cord blood was collected at birth and maternal serum was sampled within one day following birth.
• Participants completed a 45-minute survey which provided information about smoking history, alcohol use, travel, consumption patterns of food likely to contain PAHs (e.g., grilled meat), pesticide use in the home, etc.

From medical records, Perera et al. obtained measurements of birth weight, length and head circumference, and then looked for associations between these birth outcomes and the environmental contaminants, using statistical techniques to control for potential confounding variables.

What did they find? All participants in the survey had detectable inhalation levles of at least one PAH. Chlorpyrifos was detected in 98% of all maternal serum and 94% of all umbilical cord blood. Forty-two percent of mothers and 45% of newborns had cotinine levels indicative of ETS exposure.

PAH had a significant adverse effect on birth weight and head circumference among African American but not Dominican infants. For African American babies, higher exposure in the womb to PAHs was associated with lower birth weight and smaller head circumference, while exposure to chlorpyrifos was associated with decreased birth weight. After adjusting statistically for chlorpyrifos exposure, African American babies experienced a 10% in birthweight and 2% in head circumference with the highest level of PAH exposure.

In Dominicans, chlorpyrifos exposure was associated with decreased birth length.

Cotinine was not a significant predictor of adverse birth outcome.

What does it mean? As noted by the authors, "this study provides evidence that environmental pollutants at levels currently encountered in New York City adversely impact fetal development."

While the sample size was relatively small and the environmental sampling was not exhaustive, the research nonetheless revealed clear impacts of exposure to PAHs and chlorpyrifos and thus should heighten concern about environmental exposures that are experienced by residents of large urban centers.

As Perera et al. note, "a number of studies have reported that reduction in head circumference at birth or during the first year of life correlates with lower I.Q. as well as poorer cognitive functioning and school performance in childhood." The finding in this report indicating lower head circumference with higher PAH exposure would suggest that PAH contamination is yet another factor undermining inner city school performance. This suggests that steps to reduce PAH exposure, for example by controlling diesel emissions, should be pursued actively.