Air Quality of Work, Residential, and Traffic Areas during the COVID-19 Lockdown with Insights to Improve Air Quality

This study investigated the concentrations of air pollutants (NO, NO2, NOx, SO2, CO, O3, PM10, and PM2.5) at three sites with different traffic loads (work, residential, and traffic sites) before, during, and after the COVID-19 lockdown. The main objective of this study was to evaluate the effects and associated potential pollution control implications of the lockdown on the quality of ambient air at three selected sites in the urban area of Riyadh City. The average concentrations of NO, NO2, NOx, and CO decreased during the lockdown period by 73%, 44%, 53%, and 32% at the work site; 222%, 85%, 100%, and 60% at the residential site; and 133%, 60%, 101%, and 103% at the traffic site relative to the pre-lockdown period, respectively. The average concentration of O3 increased by 6% at the work site, whereas the concentration of SO2 increased by 27% at the residential site and decreased by 6.5% at the work site. The changes in PM10 and PM2.5 varied and did not exhibit a clear pattern. The air quality index (AQI) results indicated that the contribution to “undesired” air quality by O3 was 35.29% of the lockdown period at the work site while contributions to undesired air quality by PM10 and PM2.5 were 75.6% and 100% at the work site, 94.5% and 100% at the residential site, and 96.7% and 100% at the traffic site, respectively. The findings of this study are useful for devising effective urban pollution abatement policies. Applying control measures comparable to the lockdown measures over one week will result in a decrease of approximately 19% and 15% in CO mean concentration and 25% and 18% in NO2 mean concentration at residential and traffic sites, respectively.

Air Quality of Work, Residential, and Traffic Areas During the COVID-19 Lockdown with Insights to Improve Air Quality

This study investigated the concentrations of air pollutants (NO, NO2, NOx, SO2, CO, O3, PM10, and PM2.5) at three sites with different traffic loads (work, residential, and traffic sites) before, during, and after the COVID-19 lockdown. The main objective of this study was to evaluate the effects and associated potential pollution control implications of the lockdown on the quality of ambient air at three selected sites in the urban area of Riyadh City. The average concentrations of NO, NO2, NOx, and CO decreased during the lockdown period by 73%, 44%, 53%, and 32% at the work site, 222%, 85%, 100%, and 60% at the residential site, and 133%, 60%, 101%, and 103% at the traffic site relative to the pre-lockdown period, respectively. The average concentration of O3 increased by 6% at the work site, whereas the concentration of SO2 increased by 27% at the residential site and decreased by 6.5% at the work site. The changes in PM10 and PM2.5 varied and did not exhibit a clear pattern. The air quality index (AQI) results indicated that the contribution to “undesired” air quality by O3 was 35.29% of the lockdown period at the work site while contributions to undesired air quality by PM10 and PM2.5 were 75.6% and 100% at the work site, 94.5% and 100% at the residential site, and 96.7% and 100% at the traffic site, respectively. The findings of this study are useful for devising effective urban pollution abatement policies. Applying control measures comparable to the lockdown measures over one week will result in a decrease of approximately 19% and 15% in CO mean concentration and 25% and 18% in NO2 mean concentration at residential and traffic sites, respectively. Significant mitigation of urban air pollution could be accomplished through intermittent implementations of strict pollution control measures.

COVID-19-Related Changes in NO2 and O3 Concentrations and Associated Health Effects in Malta

The start of 2020 has been characterized by emission reductions in various countries across the globe following the implementation of different lock-down measures to control the transmission of the SARS-CoV-2 (COVID-19). Consequently, these reductions influenced the air quality globally. In this study, we focus on daily nitrogen dioxide (NO2) as well as ozone (O3) concentrations measured across the Maltese Islands between January and mid-October 2020. Changes in air quality are generally difficult to detect due to the complex composition and interactions occurring within the atmosphere. To quantify changes in NO2 and O3 concentrations during the COVID-19 period, we use a random forest machine learning algorithm to determine a business as usual counterfactual scenario. Results highlight a decrease in monthly mean NO2 concentrations by up to 54% in the traffic site of Msida (~21 μg m−3). In contrast, the monthly mean O3 concentrations during the COVID-19 months are up to 61% higher compared to a business as usual scenario in Msida (~28 μg m−3). In this study, we also estimate the differences in attributable fraction (AF) associated with short-term exposure to NO2 and O3 concentrations. In Msida, the AF is up to 0.9% lower and 0.8% higher for measured NO2 and O3 concentrations, respectively. Our results highlight the favorable effects of decreasing traffic-related emissions on NO2 concentrations however, we also note increases in other pollutants for example O3 concentrations which especially in the short-term can lead to various adverse health effects.