Polycyclic Aromatic Hydrocarbons and Birth Defects in California

Abstract

Background: Ambient air pollution has been associated with several birth defects, though few studies have examined polycyclic aromatic hydrocarbons (PAHs), specifically. Our aim was to assess the relationship between maternal exposure to ambient PAHs in the first two months of pregnancy and risk of several structural birth defects as part of the Berkeley-Stanford Children’s Environmental Health Center (Children’s Health and Air Pollution Study).Methods: PAHs were assessed through a combination of intermittent monitoring and estimated PAH concentrations based on daily, collected NO and CO measurements in the San Joaquin Valley of California. Daily exposure values were spatially interpolated from the air quality monitoring stations’ locations to women’s residence locations in early pregnancy using inverse distance-squared weighting with a maximum interpolation radius of 25 km. We used data from 1028 cases and 975 controls from the California center of the National Birth Defects Prevention Study (1997-2011) to examine quartiles of exposure to risk of neural tube defects (N=281), gastroschisis (N=223), and cleft lip with or without cleft palate (N=364) or cleft palate only (N=162). Models were adjusted for maternal race/ethnicity, education and vitamin use in early pregnancy. Results: We found suggestive associations between PAHs and neural tube defects including spina bifida and anencephaly with evidence of an exposure-response across quartiles of PAHs. High ambient PAHs during the first two months of pregnancy were associated with a small increased risk of neural tube defects [odds ratio (OR)=1.23; 95% confidence interval (CI):0.83, 1.82]. We found inverse associations between PAHs and risk of gastroschisis (OR=0.58; 95% CI:0.37, 0.90) and cleft lip with or without cleft palate (OR=0.66; 95% CI:0.46, 0.95).Conclusions: Some results were in the unexpected direction, but results are consistent with our previous observed associations between other traffic-related air pollutants and neural tube defects in the San Joaquin Valley of California.