Dirty skies

Air in Luxembourg City is dirty, and getting dirtier. The average level of nitrogen oxides is around 50 mcg in Hamilius and Bonnevoie, above the european limit of 40 micrograms per cubic meter. Nitrogen oxides means diesel cars.
Because of the way a diesel engine works, with an excess of air inside the engine (rather than "just enough" as in a petrol engine, which is what causes CO emissions), nitrous oxides are more likely to be formed. The nitrous oxides combine with low level ozone to form smog. Diesel engines emit high levels of nitrogen oxides (NOx) and particulate matter (PM), and in addition, a complex mixture of gases many of which are known or suspected cancer causing agents. Diesel exhaust exacerbates asthma and causes inflammation of the airways. Diesel exhaust is an important contributor to airborne concentrations of fine particle pollution, especially in urban areas.
This means that most european governments are supporting (fiscally or directly) low CO2 emitting diesel cars that are still responsible for deteriorating air quality in major cities. Since diesel versions are more expensive them the petrol versions of the same model, I guess the auto industry bosses most be happy.