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Wildfire-specific particulate matter with diameters ≤ 2.5 µm (PM 2.5 ) is the key component of wildfire smoke, with potentially higher toxicity than PM 2.5 from other sources. In this nationwide population-based cohort study, we included 22,163,195 births from Brazil during 2010 2019. Daily wildfire-specific PM 2.5 was estimated through the chemical transport model. Time-varying Cox proportional hazards models were used to characterize the exposure-time-response (E-T-R) relationship between weekly wildfire-specific PM 2.5 exposure and preterm birth (PTB) risks, followed by subgroup analyses. A 10 µg/m 3 increment in wildfire-specific PM 2.5 was associated with a hazard ratio of 1.047 (95 % confidence interval CI: 1.032–1.063) for PTB. Stronger associations between wildfire-specific PM 2.5 and PTB were observed during earlier pregnancy, among female infants, and pregnant women < 18 years old, in ethnic minorities, with a length of education ≥ 11 years, from low-income or high-temperature municipalities, and residing in North/Northeast regions. An estimated 1.47 % (95 % CI: 1.01 % 1.94 %) of PTBs were attributable to wildfire-specific PM 2.5 in Brazil, increasing from 2010 to 2019. The PTBs attributable to wildfire-specific PM 2.5 surpassed those attributed to non-wildfire PM 2.5 (0.31 %, 95 % CI: 0.09 % 0.57 %). Wildfire emerged as a critical source contributing to the PM 2.5 -linked PTBs. Prioritized fire management and emission control strategies are warranted for PTB prevention. • Wildfire-sourced PM 2.5 increased the risk of preterm birth (PTB). • Critical exposure windows were in earlier pregnancies. • Female babies and young, minority, or higher-educated mothers were more vulnerable. • Higher risks were found in low-income, hot areas and the North/Northeast regions. • Wildfire-sourced PM 2.5 posed a greater PTB risk and burden than non-wildfire PM 2.5 .
Zhang et al. (Thu,) studied this question.