Acute temporal effect of ambient air pollution on common congenital cardiovascular defects and cleft palate: a case-crossover study

This symmetric bidirectional case-crossover study examined the association between short-term ambient air pollution exposure during weeks 3-8 of pregnancy and certain common congenital anomalies in Ulaanbaatar, Mongolia, between 2014 and 2018. Using predictions from a Random Forest regression model, authors assigned daily ambient air pollution exposure of particulate matter <2.5 um aerodynamic diameter, sulphur dioxide, nitrogen dioxide, and carbon monoxide for each subject based on their administrative area of residence. We used conditional logistic regression with adjustment for corresponding apparent temperature to estimate relative odds of select congenital anomalies per IQR increase in mean concentrations and quartiles of air pollutants. The adjusted relative odds of cardiovascular defects (ICD-10 subchapter: Q20-Q28) was 2.64 (95% confidence interval: 1.02-6.87) per interquartile range increase in mean concentrations of particulate matter <2.5 um aerodynamic diameter for gestational week 7. This association was further strengthened for cardiac septal defects (ICD-10 code: Q21, odds ratio: 7.28, 95% confidence interval: 1.6-33.09) and isolated ventricular septal defects (ICD-10 code: Q21.0, odds ratio: 9.87, 95% confidence interval: 1.6-60.93). We also observed an increasing dose-response trend when comparing the lowest quartile of air pollution exposure with higher quartiles on weeks 6 and 7 for Q20-Q28 and Q21 and week 4 for Q21.0. Other notable associations include increased relative odds of cleft lip and cleft palate subchapter (Q35-Q37) and PM2.5 (OR: 2.25, 95% CI: 0.62-8.1), SO2 (OR: 2.6, 95% CI: 0.61-11.12), and CO (OR: 2.83, 95% CI: 0.92-8.72) in week 4. Our findings contribute to the limited body of evidence regarding the acute effect of ambient air pollution exposure on common adverse birth outcomes.