@article {Lavignethoraxjnl-2021-217602, author = {Eric Lavigne and Niilo Ryti and Antonio Gasparrini and Francesco Sera and Scott Weichenthal and Hong Chen and Teresa To and Greg J Evans and Liu Sun and Aman Dheri and Lionnel Lemogo and Serge Olivier Kotchi and Dave Stieb}, title = {Short-term exposure to ambient air pollution and individual emergency department visits for COVID-19: a case-crossover study in Canada}, elocation-id = {thoraxjnl-2021-217602}, year = {2022}, doi = {10.1136/thoraxjnl-2021-217602}, publisher = {BMJ Publishing Group Ltd}, abstract = {Background Ambient air pollution is thought to contribute to increased risk of COVID-19, but the evidence is controversial.Objective To evaluate the associations between short-term variations in outdoor concentrations of ambient air pollution and COVID-19 emergency department (ED) visits.Methods We conducted a case-crossover study of 78 255 COVID-19 ED visits in Alberta and Ontario, Canada between 1 March 2020 and 31 March 2021. Daily air pollution data (ie, fine particulate matter with diameter less than 2.5 {\textmu}m (PM2.5), nitrogen dioxide (NO2) and ozone were assigned to individual case of COVID-19 in 10 km {\texttimes} 10 km grid resolution. Conditional logistic regression was used to estimate associations between air pollution and ED visits for COVID-19.Results Cumulative ambient exposure over 0{\textendash}3 days to PM2.5 (OR 1.010; 95\% CI 1.004 to 1.015, per 6.2 {\textmu}g/m3) and NO2 (OR 1.021; 95\% CI 1.015 to 1.028, per 7.7 ppb) concentrations were associated with ED visits for COVID-19. We found that the association between PM2.5 and COVID-19 ED visits was stronger among those hospitalised following an ED visit, as a measure of disease severity, (OR 1.023; 95\% CI 1.015 to 1.031) compared with those not hospitalised (OR 0.992; 95\% CI 0.980 to 1.004) (p value for effect modification=0.04).Conclusions We found associations between short-term exposure to ambient air pollutants and COVID-19 ED visits. Exposure to air pollution may also lead to more severe COVID-19 disease.Data may be obtained from a third party and are not publicly available. Data are on secured server and cannot be accessible to the public.}, issn = {0040-6376}, URL = {https://thorax.bmj.com/content/early/2022/03/30/thoraxjnl-2021-217602}, eprint = {https://thorax.bmj.com/content/early/2022/03/30/thoraxjnl-2021-217602.full.pdf}, journal = {Thorax} }