It seems that if you are interested in checking air quailty, the mountains in Norway make an excellent choice. Sensors there can detect the carbon readings from a single fox, according to this article. This sensitive detection also allows scientists to tell where certain pollutants are coming from, including those emitted as greenhouse gases from our cars. With the rapid industrialization of China, more greenhouse gases are present in Arctic Norway than ever before. One particular interesting piece from the article is that researchers can tell where automotive exhaust came from due to differences in the formulation of fuel made standard in a particular country.
Also discussed in the article, but unrelated to automobiles, were mercury from the burning of fillings in dead people's teeth, which can be traced to certain Asian countries, and a suggested smoking ban. Pretty interesting stuff fills the air we breathe, wouldn't you say?