The increased concentration of airborne particulate matter (PM) and nitrogen oxides (NOx) in the atmosphere of many European cities is still a major environmental problem.
Airborne particulate matter (PM) is a complex mixture of microscopic particles derived from natural sources, such as volcanic explosions, dust resuspension and pollen, and anthropogenic sources, such as transportations, combustion processes, processing of mineral and agriculture. They are responsible for various effects on climate, visibility reduction, acid rain and health effects, such as respiratory and heart problems and even cancer.
