Air Quality and Automobile. Status on Air Quality in Large Cities

The automotive industry is facing three major environmental challenges. The first is to limit global warming to no more than +2°C by 2050, with a sharp reduction in CO ₂ emissions from vehicles (in Europe, -37.5% in 2030 compared with 2021). Also, emissions will have to be measured and anticipated over the entire vehicle life cycle, thus integrating emissions no longer from well to wheel but from cradle to grave. The second challenge is to cope with the increasing scarcity of natural resources, which means that resources must be used only when necessary, and materials must be managed sustainably. The third challenge concerns air quality, the importance and impact of which are closely linked to ever-increasing urbanization: more than a billion people worldwide live in the world's hundred largest megacities (10 million inhabitants or more). Some of them have already recorded pollutant concentrations twenty-five times higher than the limits recommended by the World Health Organization (WHO). So it's natural to ask how air quality has evolved over the last few decades, particularly in major urban centers. Air quality is the result of a complex balance between emissions of atmospheric pollutants, their chemical and/or physical transformation under the influence of meteorological conditions and imports. However, due to regional specificities, the great complexity of the atmospheric environment and the non-linear production processes of certain pollutants, the relationship between emissions and air quality is rather difficult to establish in a simple and unique way. This article begins by taking stock of trends in pollutant concentrations attributable to cars in major European urban centers. Secondly, it proposes an updated assessment of the contribution of automobiles to local air pollution.

After a brief history of air quality, we'll go back over the definition of certain key terms, then give an overview of emissions and concentrations of atmospheric pollutants from local to European levels. We'll also zoom in on ozone, a secondary pollutant that occurs mainly in summer. We will demonstrate the positive impact of new automotive technologies, highlighted by prospective studies based on air quality modelling. We will also draw some preliminary lessons from the effect of Covid-19-related health containment on air quality, which has led to a 70% reduction in road traffic and associated emissions in the Île-de-France region.