Early-Life Ozone Exposure and Asthma and Wheeze in Children

Importance: Ozone (O₃) is the most frequently exceeded air pollutant standard in the US. While short-Term exposure is associated with acute respiratory health, the epidemiologic evidence linking postnatal O₃exposure to childhood asthma and wheeze is inconsistent and rarely evaluated as a mixture with other air pollutants. Objectives: To determine associations between ambient O₃and subsequent asthma and wheeze outcomes both independently and in mixture with fine particulate matter and nitrogen dioxide in regions with low annual O₃concentrations. Design, Setting, and Participants: This cohort study consisted of a pooled, multisite analysis across 6 US cities using data from the prospective ECHO-PATHWAYS consortium (2007-2023). Included children had complete airway surveys, complete address histories from age 0 to 2 years, and a full term birth (≥37 weeks). Logistic regression and bayesian kernel machine regression (BKMR) mixture analyses were adjusted for child anthropomorphic, socioeconomic, and neighborhood factors. Exposures: Exposure to ambient O₃in the first 2 years of life derived from a validated point-based spatiotemporal model using residential address histories. Main Outcomes and Measures: The primary outcome was asthma and wheeze at ages 4 to 6 years; the secondary outcome was asthma and wheeze at ages 8 to 9 years. Outcomes were based on caregiver reports derived from a validated survey. Results: The analytic sample of 1188 participants had a mean (SD) age of 4.5 (0.6) years at the age 4 to 6 years visit and consisted of 614 female participants (51.7%) and 663 mothers who had a bachelor's degree or higher (55.8%). The mean (SD) O₃concentration was 26.1 (2.9) parts per billion (ppb). At age 4 to 6 years, 148 children had current asthma (12.3%) and 190 had current wheeze (15.8%). The odds ratio per 2 ppb higher O₃concentration was 1.31 (95% CI, 1.02-1.68) for current asthma and 1.30 (95% CI, 1.05-1.64) for current wheeze at age 4 to 6 years; null associations were observed for outcomes at age 8 to 9 years, and for sensitivity covariate adjustment. BKMR suggested that higher exposure to O₃in mixture was associated with current asthma and wheeze in early childhood. Conclusions and Relevance: In this cohort study with relatively low ambient O₃exposure, early-life O₃was associated with asthma and wheeze outcomes at age 4 to 6 years and in mixture with other air pollutants but not at age 8 to 9 years. Regulating and reducing exposure to ambient O₃may help reduce the significant public health burden of asthma among US children.