Health, Transport and the Environment: The Impacts of the COVID-19 Lockdown on Air Pollution.

Lockdown measures were initiated in Italy on March 9th after the start of the SARS-CoV-2 epidemic to flatten the epidemic curve. The aim of the present study was to assess the impact of restrictive measures in the Apulia Region, southern Italy, on air quality from March to April 2020. We applied a dual-track approach. We assessed citizen mobility and vehicle traffic with mobility network data and information obtained from satellite tracking, and we evaluated and compared pollutant concentration data as measured by monitoring stations maintained by the Regional Agency for Environmental Protection and Prevention of Apulia (ARPA). The results showed a decrease in the weekly mean NO concentration recorded by urban traffic stations during the lockdown period. In particular, in the city of Bari, the average NO concentration decreased from 62.2 μg/m in March 2019 to 48.2 μg/m in March 2020. Regarding PM10 levels, the average concentrations at the individual traffic stations showed no particular variation compared to those in the same months of the previous year, except for Bari-Caldarola Station in March 2019/2020 (-value < 0.001) and in April 2019/2020 (-value = 0.04). In particular the average in March 2019 was ~26.9 μg/m, while that in March 2020 was ~22.9 μg/m. For April, the average concentration of PM10 in 2019 was 27.9 μg/m, while in 2020, the average was ~22.4 μg/m. This can be explained by the fact that PM10 levels are influenced by multiple variables such as weather and climate conditions and desert dust advections.