Wildland fire smoke and birth defects in California

This study investigates the association between wildfire smoke exposure, specifically fine particulate matter (PM_2.5), and the risk of selected structural birth defects in the San Joaquin Valley of California. Birth defects are a leading cause of infant mortality and an important contributor to childhood and adult morbidity. Major structural birth defects are diagnosed in 2 to 4% of infants in the United States. Environmental contaminants, including air pollution, have been suggested as potential risk factors for these anomalies.

Increased risk for several birth defects was observed with higher quartiles of wildfire smoke exposure. Notably, the third quartile of average fire density PM_2.5 was associated with increased odds of cleft lip (OR = 2.29; 95% CI: 1.12, 4.69), and the highest quartile of maximum fire density PM_2.5 was associated with increased risk of coarctation of the aorta (OR = 2.26; 95% CI: 1.02, 4.99). Spina bifida was consistently associated with higher exposure across multiple metrics, including a significant association with the highest quartile of maximum fire increment PM_2.5 (OR = 2.76; 95% CI: 1.14, 6.66).