I've just looked at the government's Air Quality Index web site www.airnow.gov. There appears to be a ton of info/data covering the continental U.S.
For anyone planning a move or traveling, this site should be helpful, especially when combined with the info from scorecard.org and from the map at the bottom of our housing page at ciin.org.
For those with MCS, relocating or traveling can be really difficult. Having places to find reliable information about different places can help, but no one resource will be perfect. Combining data from these 3 sources will help develop a clearer picture of the places on anyone's list of possibilities.