There is growing concern about adverse developmental effects in infants and young children from prenatal exposure to environmental air pollutants, including polycyclic aromatic hydrocarbons (PAH), particulate matter (PM2.5), and environmental tobacco smoke (ETS). The proposed study combines expertise in molecular epidemiology and biomarkers, state-of- the-art pollutant monitoring techniques, and a strong theoretical framework to guide assessment of the impacts of these pollutants on fetal and child growth and development. The specific aims are: 1. To test the hypothesis that prenatal exposure to airborne polycyclic aromatic hydrocarbons (PAH) adversely affects fetal growth and early childhood growth and development, after controlling for non-PAH components of PM2.5, ETS, nutritional status (essential fatty acids and antioxidants) and other potential confounders; 2. To explore whether non-PAH components of PM2.5, and ETS have an independent effect on birth outcomes and childhood growth and development, after controlling for PAH, and to explore possible interactions between PAH, PM2.5 and ETS; and 3. To estimate the relative contribution of ambient PAH pollution vs. ETS and other indoor PAH sources to a) personal PAH exposure and PAH-DNA adducts and b) impairment of fetal growth and early child development. To achieve these aims, the international team of researchers will carry out a prospective cohort study of 400 nonsmoking pregnant women living in Krakow, Poland, and will follow their newborns for 12 months postnatally. Fetal growth will be assessed at birth by weight, length, head circumference, and size for gestational age. Childhood growth and developmental outcomes will be measured using the Fagan Test and the Bayley Scales. Strengths of the research include the combination of personal inhalation monitoring of PAH and PM2.5 with biomarkers (umbilical cord blood levels of PAH-DNA adducts, cotinine, essential fatty acids, antioxidants and lead) to estimate in utero exposure to the pollutants of interest and potential confounders. The Polish cohort provides a valuable model for study since emissions from coal burning and traffic are relatively high. However, the results will be broadly applicable since exposures to PAH, ETS and PM2.5 during pregnancy are common in virtually all industrialized regions of the world. It is anticipated that this research will provide relevant data to policymakers concerned with protecting the health of young children.