The air in cities are getting dirty mostly due to diesel car emissions. In order to save the planet from global warming a lot of diesel cars has been sold in Europe due to lower co2 emissions. They were sold as clean diesel cars but were not really clean emitting a lot nox/pm2.5 small particle emissions. The small particles are a danger to public health. It is time we go fully electric/hybrid car in the cities or remove cars from the city centers all together. I do not think a car drivers in cities has the right to pollute the air quality that pedestrians breathe.