Picking a place to live

I plan to stay in New York for some time yet but there are times when the expense, danger, lack of space...

NYC is the third worst overall for air. Also scoring near the top for lead in the air and water pollution. This is not only bad news for current asthma sufferers like myself, NYC is now at the point where one in eight children have asthma and one in four in certain parts as opposed to six percent for the general population.
Diesel fumes are responsible for 4000 deaths per year in New York State. This might have to do with the 30,000 trucks entering Manhattan each day.

Whether I will stay in the U.S. is uncertain so I've sought out information on other cities. I wasn't able to find isolated pollution reports but did find some Total Quality of Life stats which use pollution as a factor. New York makes it to 39th on the list of the world's best cities and nationally the US only makes it to thirteenth.

Note:
At one point I asked a related question using Google Answers.