The Covid-19 hospitalization risk associated with air pollution in New York state counties after the 2023 Quebec wildfires.

Background: Air pollution from the 2023 Quebec wildfires affected New York state (NY) with daily average PM_2.5 levels that peak on June 7. Increased Covid-19 hospitalizations were recorded weeks after the wildfires. This study analyses the trend of Covid-19 hospitalization in NY counties after the 2023 Quebec wildfires and estimates their association with higher PM_2.5 concentration levels, compared to 2022.

Design and methods: A Bayesian spatiotemporal regression model was used to estimate the impact of wildfire smoke on Covid-19 hospitalizations. Four periods of pre/post-wildfire and 7-day post-wildfire daily hospitalization periods were considered to compare the association of daily average PM_2.5 levels, from May 1 to June 7, with daily Covid-19 hospitalization rates in NY counties in 2022 and 2023. The pre/post-wildfire and 7-day post-wildfire periods considered a lag of 2, 4, 6, and 8 weeks and 24, 48, 72, and 96 h, respectively. The model was adjusted for sociodemographic factors.

Results: The Covid-19 hospitalization rate followed an increasing trend in the second, third and fourth pre/post-wildfire periods in 2023 in contrast with 2022 when no trends were identified. Each PM_2.5 unit increase was associated with a 2%; 6% and 7% Covid-19 higher hospitalization risk in periods 2, 3, and 4, respectively, in 2023 only. These findings identify a potential impact of wildfire smoke on the severity of Covid-19 morbidity after 2 weeks of the wildfires. Robust spatiotemporal analyses can be used to identify specific at-risk areas and communities to support public health decision-making and health strategies.

Conclusions: This study identifies a higher risk of Covid-19 hospitalization in New York State associated with higher air pollution levels from the 2023 Quebec wildfires, in the first week and 2, 3, and 4 weeks after the wildfires. These findings concur with the increasingly investigated association of air pollution with severe Covid-19. The methodological approach of this study shows the utility of spatiotemporal epidemiological analyses and need for future research on wildfire smoke as a potential determinant of severe Covid-19. With more frequent and extreme climate events it is paramount to improve our understanding of many potential health impacts of wildfires to prepare strategies to deal with, and potentially anticipate, environmental health and healthcare responses in wildfire-prone regions.