Asthma’s Link to Prenatal Exposure to Air Pollution

A newly published study finds that higher exposure to the fine particulate matter in air pollution at midgestation is associated with asthma development later in childhood, and particularly in boys.

Because the influence of particulate air pollution on respiratory health starts in utero and may be sex-specific, and because fetal lung growth and structural development occurs in stages, the effects on asthma and other respiratory disorders later in life may differ based on the timing of exposure to air pollution.

Accordingly, in a study published online and slated for the November 1 issue of the American Journal of Respiratory and Critical Care Medicine, researchers attempted to identify sensitive times during gestation for the effects of prenatal exposure to particulate matter with a diameter of 2.5 µm (PM2.5) or smaller on the later development of pediatric asthma in a cohort of urban pregnant women in Boston, Massachusetts.

The study included 736 full-term children. Each mother’s daily PM2.5 exposure was estimated over gestation. The authors then looked at the association between weekly averaged PM2.5 levels during pregnancy and cases of diagnosed asthma in the children by age 6. They also compared the association based on the children’s sex.

The results showed that higher PM2.5 exposure between 16 and 25 weeks of gestation were significantly associated with early childhood asthma development. Further analysis showed that the association existed for boys but not girls.

“A more definitive characterization of vulnerable (time) windows may provide insight into underlying mechanisms when coupled with the understanding of lung growth, airway structural and functional development, and asthma pathophysiology,” the study authors concluded.

—Michael Gerchufsky

Reference:

Hsu H-HL, Chiu Y-HM, Coull BA, et al. Prenatal particulate air pollution and asthma onset in urban children: identifying sensitive windows and sex differences. Am J Respir Crit Care Med. 2018;192(9):1052-1059. https://doi.org/10.1164/rccm.201504-0658OC.