The effect of COVID-19 lockdown/post-lockdown and season on children's exposure to PM2.5 and time expenditure by environment type

BACKGROUND/AIM PM₂.₅ concentration differs by environment type (indoor, outdoor, automobile). Elevated PM₂.₅ exposure is associated with children’s poor cognitive/mathematical performance, a strong predictor of poor later academic performance. The Bridging the Environment and Neurodevelopment for Children’s Health Study provided low-cost personal air quality sensors to 30 Washington, D.C. metro-area children to investigate the relationship between daily air pollution exposures and children’s cognitive performance. We investigated whether, between COVID-19 lockdown and post-lockdown periods, there were significant differences between measured location-specific (indoor, outdoor, automobile) PM₂.₅ values and time spent in these locations, as well as these exposures’ correlation with children’s cognitive performance. METHODS Each data collection round included children (age 8-11) wearing the air quality sensor for 3 days during which parents recorded their activities; on day 3, children completed cognitive assessments. We collected data during winter 2020-2021 (Round 1) and spring/summer 2021 (Round 2). We used: Friedman tests to assess differences in average PM₂.₅ and time spent by activity location for each round, Wilcoxon signed-rank tests to evaluate change over time and Spearman correlation tests to evaluate correlation between location-specific PM₂.₅/time exposure and cognitive performance. RESULTS We found that there were significant differences in PM₂.₅ exposure by activity type during the post-lockdown period--PM₂.₅ exposure outside was significantly greater than that measured indoors or in an automobile (median outdoors = 5.11 µg/m³; indoors = 3.25 µg/m³; automobile = 2.66 µg/m³). There were significant differences based on average time spent (logged in quarter-hour increments) in these locations rounds 1 vs. 2: outdoors (median=0.92 hours vs. 2.17 hours) and in automobiles (median=1.25 hours vs. 2.75 hours). These exposures weakly correlated with cognitive performance. CONCLUSION Our findings suggest seasonal effects of place-based PM₂.₅ exposure and the effects of the cessation/the resumption of "normal life” during the COVID-19 pandemic’s phases. KEYWORDS--air pollution-child health-cognitive outcomes