Spatio-Temporal Trends in Wildfire Smoke Exposures at Schools and Childcare Centers in the United States and Implications for Child and Adolescent Health.

Abstract

Background: Wildfires are on the rise in the Unites States. Epidemiological evidence demonstrates that wildfire smoke exposure is harmful to health, especially for children and adolescents. We quantified temporal and regional trends in wildfire smoke exposure at United States public schools and childcare centers to inform risk assessment, mitigation strategies, and policy.

Methods: We derived annual smoke days (binary indicator of wildfire "smoke day" versus "non-smoke day" determined using smoke plume identification from satellite imagery and simulated air trajectories from fire locations), and student-smoke-days for public schools (n=115,612) and childcare centers (n=131,372) across the United States from 2006-2023 using national daily wildfire PM_2.5 products. Indoor/outdoor PM₂.₅ mass concentration ratios were derived for West Coast facilities (n=71) with nearby PurpleAir monitors.

Results: Mean annual smoke days increased from 6.8 to 54.4 at schools (during the academic year) and from 9.4 to 112.2 at childcare centers (year-round) between 2006 and 2023, totaling 2.64 and 1.02 billion student-smoke-days in 2023, respectively. Smoke-day counts were highest in the South and Midwest, while the West experienced the most severe days. Median (IQR) indoor/outdoor PM₂.₅ ratios for schools across working-hours was 0.86 (0.54, 1.39), indicating substantial but variable building protection.

Conclusions: Exposure to wildfire smoke days at youth educational facilities increased rapidly over time, especially between 2019 and 2023, with substantial regional differences in magnitude and severity. Schools and childcare centers can play a pivotal role in wildfire smoke preparedness through implementation of clean-air strategies and exposure mitigation plans to protect child and adolescent health.