Authors
Perera, FP., Rauh, V., Tsai, W., Kinney, P., Camann, D., Barr, D., Bernert, T., Garfinkel, R., Tu, Y., Diaz, D., Dietrich, J., Whyatt, RM.

Title
Effects of transplacental exposure to environmental pollutants on birth outcomes in a multiethnic population

Journal
Environmental Health Perspectives, 111 (2): 201-205; 2003.

Summary
Pregnant women are potentially exposed to a number of contaminants that are ubiquitous in the environment. Certain pesticides and polycyclic aromatic hydrocarbons (PAHs) have been shown to alter, modify or mimic estrogen. PAHs are a group of over 100 different chemicals that are produced by the incomplete combustion of fossil fuel, oil and gas, industrial processes or other organic substances such as tobacco or charbroiled meat. Hormones are essential for normal fetal development and it is unknown if the fetus can adapt to a changing endocrine milieu. It is known that urban minority groups are at a higher risk of adverse pregnancy outcomes and they are also more likely to be exposed to ambient air pollution, environmental tobacco smoke (ETS) and pesticides. The objectives of this study were to determine if prenatal exposure to environmental pollutants was negatively associated with birth weight, length and head circumference after controlling for effects of known physical, biologic, and toxic determinants of fetal growth.

Subjects were Dominican and African-American women from Washington Heights, Central Harlem and South Bronx, New York. Only nonsmoking women aged 18-35 who were free from diabetes, hypertension, known HIV, and had resided in the area for at least one year were eligible for the study. The researchers conducted personal interviews with each woman in order to gather demographic, lifestyle and dietary data. As well, during the 3rd trimester of their pregnancy women had to wear a small backpack containing a personal monitor which collected vapors and particles 2.4 micrograms in diameter on a cleaned microfiber filter and polyurethane foam cartridge backup. The women wore the packs during the day for 2 consecutive days and placed the monitor near the bed at night. The samples were later analyzed for PAHs. The authors determined compliance by randomly placing motion detectors in the backpacks of selected women. Eight-five percent of the total number of motion detections occurred during waking hours. Quality control measures were taken to ensure accuracy in the flow, rate, time and completeness of documentation. Blood samples were collected from the mother within 1 day postpartum, and umbilical cord blood was collected at delivery in order to measure plasma chlorpyrifos levels. Finally, fetal growth information was abstracted from each infant's medical records following delivery. This included the infant's gestational age at birth, date of delivery, sex, birth weight, complications of pregnancy at delivery, and any medications that the mother took during pregnancy.

The final analysis included 263 women with valid prenatal personal monitoring data on PAHs, cord or maternal blood samples, complete questionnaire data, birth outcome data, and high quality monitor data. Present smokers with cotinine levels > 25ng/ml were also excluded.
One hundred percent of the women had detectable levels of one or more PAHs. After adjusting for several other factors, PAHs were found to be significantly associated (p=0.02) with decreased birth weight and smaller head circumference (p=0.04) among African Americans. This translated into a 9% reduction in birth weight and 2% decrement in head circumference due to PAHs. The organophosphate pesticide chlorpyrifos was associated with reduced birth weight (p=0.01) among African-Americans and reduced length (p=0.003) among Dominicans.

This study had a strong exposure assessment through the use of personal monitoring devices and serum biomarkers for exposure. The implications of the findings are important. Studies have shown that low birth weight and reduced head circumference at birth or during the first year of life is correlated with lower IQ and school performance. However, some factors may limit the generalization of these results. First, the personal monitoring devices were measured at only one point of time and the women's exposure levels may have varied greatly throughout their pregnancies. Second, the study had a modest sample size and the relationships seen in low income minority women may be different in women with dissimilar cultural, ethnic and socioeconomic backgrounds.