1) they reflect different sources of air-pollution (NO2 reflects traffic related air-pollution, whereas PM2.5 is a combination of traffic and non-traffic sources), 2) they were considered in previous studies (Cole et al., 2020, Liang et al., 2020, Travaglio et al., 2020, Wu et al., 2020), and 3) they are responsible for the highest number of years of life lost compared to other pollutants in Europe (Ortiz 2019).