Most polluted city in France?

I read today in my hometown newspaper in France that the city of Annecy (an hour away from where I was born) was the second, most polluted French city. This immediately made me think, how is that measured and what is the number one city and the last one on the list, showing clearly that some newspapers and their journalists are pathetic when it comes to convey information you can use.

The answer to my first question is that in that global study, from the Word Health Organization (WHO), is measuring particle Pollution in PM10 (solid droplets of less than 10 micrometers in diameter) and PM2.5 (yes, less than 2.5 micrometers!). These buggers are so small that they can get into your lungs and cause some serious health problems.

Oh, by the way, the most polluted French City is Marseilles in the South of France. Tomorrow, I'll dig a bit more into that survey...