Ambient air pollution and congenital heart defects in Lanzhou, China

Congenital heart defects are the most prevalent type of birth defects. The association of air pollution with congenital heart defects is not well understood. We investigated a cohort of 8,969 singleton live births in Lanzhou, China during 2010-2012. Using inverse distance weighting, maternal exposures to particulate matter with diameter ≤10μm (PM₁₀), nitrogen dioxide (NO₂), and sulfur dioxide (SO₂) were estimated as a combination of monitoring station levels for the time spent at home and the work location. We used logistic regression to estimate the associations, adjusting for maternal age, education, income, BMI, disease, folic acid intake and therapeutic drug use, and smoking; season of conception; fuels for cooking; and temperature. We found significant positive associations of Patent Ductus Arteriosus (PDA) with PM₁₀ during the 1^st trimester, 2^nd trimester and the entire pregnancy (OR _{1st trimester}=3.96, 95% Confidence Interval (CI): 1.36, 11.53; OR _{2nd trimester}=3.59, 95% Confidence Interval (CI): 1.57, 8.22; OR _{entire pregnancy}=2.09, 95% CI: 1.21, 3.62, per interquartile range (IQR) increment for PM₁₀ (IQR=71.2, 61.6, and 27.4 μg/m³ respectively)), and associations with NO₂ during 2^nd trimester and entire pregnancy (OR _{2nd trimester}= 1.92, 95% CI: 1.11, 3.34; OR _{entire pregnancy}=2.32, 95% Cl: 1.14, 4.71, per IQR increment for NO₂ (IQR=13.4 and 10.9 μg/m³ respectively)). The associations for congenital malformations of the great arteries and pooled cases showed consistent patterns. We also found positive associations for congenital malformations of cardiac septa with PM₁₀ exposures in the 2^nd trimester and the entire pregnancy, and SO₂ exposures in the entire pregnancy. Results indicate a health burden from maternal exposures to air pollution, with increased risk of congenital heart defects.