Is There a Cross-Generational Association between Air Pollution and Childhood Asthma?

Abstract

Background: Air pollution is a well-established risk factor for childhood asthma, yet its potential cross-generational effects remain largely unexplored. Objectives: To estimate the association between grandmaternal and maternal exposure to ambient air pollution during pregnancy and asthma in the grandchild. Methods: This nationwide register-based cohort study included 85,963 Swedish children. Childhood asthma was defined as purchase of at least two asthma medications during the first 6 years of life. Residential addresses were geocoded and high-resolution air pollution concentrations of particulate matter with a diameter of 2.5 μm or less (PM2.5), elemental carbon (EC), nitrogen oxides (NOx) and primary PM2.5 (pPM2.5) including EC, primary organic aerosols (POA) and mineral dust/ash were extracted from the coupled DEHM/UBM atmospheric model system. Grandmaternal exposure was estimated for the year the mother was born, and maternal exposure for the birth year of the child. Logistic regression was used to estimate odds ratios (ORs) for asthma by exposure quartiles, adjusting for individual, familial, and area-level socioeconomic covariates. Results: Both grandmaternal and maternal exposure to pPM2.5, EC, and NOx during pregnancy were associated with higher odds of asthma in the grandchildren. For grandmaternal exposure to pPM2.5, ORs were 1.06 (95% CI: 1.00–1.12), 1.09 (1.03–1.15), and 1.06 (1.01–1.13) for the second, third, and fourth quartiles, respectively, compared to the first. Maternal exposure showed similar patterns, with ORs for pPM2.5 in the highest quartile reaching 1.10 (1.04–1.17). No clear concentration–response relationship was observed. Associations were reduced only slightly after adjustment for maternal/grandmaternal exposure, respectively. Conclusions: Our findings indicate a cross-generational association between exposure to ambient air pollution and childhood asthma, proposing that respiratory vulnerability may begin earlier than previously recognized. Since the results did not show a clear concentration–response, further studies are needed.