Statistical Quantification of COVID-19 Lockdown Effect on Air Quality From Ground-Based Measurements in Ontario, Canada

Abstract:

With lockdowns implemented in many parts of the world, because of the COVID-19 pandemic, air quality appears to have improved. Preliminary measurements and studies from around the world have highlighted drops in nitrogen dioxide, carbon monoxide and other critical pollutants. Some of these studies were able to correlate these drops in pollutants with local decreases in transportation and/or industry during lockdowns. None of these studies, however, took into consideration potential seasonal variability, transboundary influences, or other factors and the statistical significance of these drops compared to similar time periods in previous years. This investigation quantified the statistical significance of changes to air quality indicators from ground-based measurements in Southern Ontario to determine if COVID-19 restrictions directly impacted local air quality. This method accounts for seasonal variability, transboundary influences, and new factors, such as COVID-19 restrictions, in explaining trends in the levels of NO2, CO, O3 and PM2.5. Based on this analysis, it appears that COVD-19 restrictions had a significant impact on air quality levels, particularly nitrogen dioxide, at sites throughout the province. The significance of the impact varied based on transboundary influences and local factors. To the best of our knowledge, the statistical method developed here is the first of its kind to be applied to air quality data.