Susceptible windows of long-term childhood exposure to air pollution on adult self-reported bronchitic symptoms

Background: Childhood exposure to air pollution has long-term effects on adult bronchitic symptoms, but the age windows of susceptibility are understudied. Methods: We included 1444 participants from the Southern California Children’s Health Study, who were recruited at ages ∼9–10 years in 1992–1993 or 1995–1996 or ages ∼5–7 years in 2002–2003, followed until high-school graduation, and re-contacted again in adulthood (mean age=33years) to collect self-reported bronchitic symptoms. Yearly average nitrogen dioxide (NO₂), 8-h maximum ground-level ozone (O₃), and particulate matter of ≤10 µm in diameter (PM₁₀) were estimated by using inverse-distance squared spatial interpolation to participants’ residential history from conception to age 16 years. Log Poisson Distributed Lag Models were fitted to identify susceptible windows of childhood exposure to air pollution on adult bronchitic symptoms adjusted for childhood and adult confounders. We explored sex-specific susceptible windows. Results: We identified ages 1–2years as a susceptible window in which NO₂ exposure was associated with a higher risk of adult bronchitic symptoms, with the largest associations observed at age 1 year (risk ratio per 10ppb=1.12; 95% confidence interval: 1.01, 1.25). We observed both positive (ages 12–15years) and inverse (ages 8–11years) associations with O₃ exposure. Suggestive evidence of increased risk at ages 3–4 years was observed for PM₁₀. There was no evidence of sex differences. Conclusion: Early childhood might be a particularly susceptible window of exposure to NO₂ (ages 1–2years) and possibly for PM₁₀ (ages 3–4years) for increased risk of adult bronchitic symptoms, while early adolescence (ages 12–15years) might be a susceptible window for O₃ exposure.