Impact of Confinement on the Reduction of Pollution and Particulate Matter Concentrations. Reflections for Public Transport Policies

Different initiatives have been implemented to improve air quality in large cities, such as encouraging travel by sustainable modes of transport, promoting electro-mobility, or the car-free day. However, to date, we have not found statistics that indicate to what extent the concentration levels of particulate matter PM(2.5), PM(10) and nitrogen oxides (NO(x)) pollutants decrease as a result of public policy. We used official data from the Chilean Government’s national air quality information system (SINCA) for the Santiago metropolitan region and estimated the impact of the confinement by COVID-19 on the ambient concentration average values of NO(x) gases and particulate matter PM(2.5) and PM(10), which are the main air pollutants produced by the transport sector after CO(2). We found that in general there are significant differences between the average levels of gas emissions for 2020 compared to 2019. In particular, we found that, for the months of total confinement May-July, the monthly average levels decreased between 7% and 19% for particulate matter PM(2.5), between 18% and 50% for PM(10) and between 34% and 48% for NO(x). With the return to the new normality, these improvements in ambient concentration levels may be affected by the increase in private transport trips, due to the reluctance of citizens to return to mass public transport. Our results, therefore, represent the maximum impact that can be expected in reducing ambient concentration levels in the city of Santiago of Chile when a mobility reduction of gasoline vehicles is implemented.