50 / 2023-04-25 21:16:10

Associations of early-life exposure to submicron particulate matter with childhood asthma and wheeze: a multi-city study in China

PM1; PM2.5; Early-life exposure; Childhood; Asthma; Wheeze

Background: Exposure to particulate matter (PM) has been associated with childhood asthma and wheeze. However, as a major contributor of PM_2.5 and even potentially more toxic than PM_2.5, the specific effect of PM₁ remain unclear.

Objectives: We investigated the effect of early-life (prenatal and first-year) exposure to size-segregated particles including PM₁, PM_1-2.5, PM_2.5, PM_2.5-10, and PM₁₀ on childhood asthma and wheeze.

Methods: Based on a multi-city study established between 2019 and 2020 in China, a total of 29,418 preschool children aged 3 to 6 years were included. Machine learning-based space-time model was applied to estimate early-life PM₁, PM_2.5, and PM₁₀ exposure at 1 × 1-km resolution. Multilevel logistic regression models were performed to evaluate the association of PM exposure with childhood asthma and wheeze.

Results: Of 29 418 children [15320 boys (52.1%) and 14098 girls (47.9%)] aged 3 to 6 years [mean (SD): 4.9 (0.9)], 2524 (8.6%) ever had wheeze and 1161 (3.9%) were diagnosed with asthma. Among all children, 18514 (62.9%) were breastfed for over 6 months and 787 (2.7%) had parental history of atopy. Of all the mothers, 75.6% (22 250) of them received education with university and above, and 2.3% (576) of them were current or former smokers during pregnancy. For household environment, 7525 (29.7%) families had passive smoke exposure in early life. Early-life PM₁, PM_2.5, and PM₁₀ exposure were significantly associated with increased risk of childhood asthma, with higher estimate for PM₁ [OR = 1.55 (95% CI: 1.27, 1.89), OR = 1.14 (95% CI: 1.03, 1.26), and OR = 1.11 (95% CI: 1.02, 1.20) for per 10-μg/m³ increase in PM₁, PM_2.5, and PM₁₀, respectively]. Non-significant association was observed for PM_1-2.5, suggesting that PM₁ rather than PM_1-2.5 contributed to the association between PM_2.5 and childhood asthma. As for childhood wheeze, we identified significant associations with early-life PM₁ and PM_2.5 exposure [OR = 1.23 (95% CI: 1.07, 1.41) and OR = 1.08 (95% CI: 1.01, 1.16) for per 10-μg/m³ increase in PM₁ and PM_2.5, respectively].

Conclusion: In this cross-sectional study, higher estimate effects were observed for the PM and childhood asthma with smaller particle size such as PM₁. The results also suggested that the association between PM_2.5 and childhood asthma was mainly attributable to PM₁.