While the life expectancy in the US is lower than in the rest of the developed nations, I don't think that's due to pollution. More like general lifestyle and access to healthcare.
It's always shocking to me to go to Europe (or New Zealand, or even Canada) and see how much healthier and leaner people look. And it's horrifying to visit the mid-west and see how corpulent people are. Watch some of the original Sesame Street episodes or other US TV shows from 40 years ago, and see how skinny everyone looked.
Pollution is a problem, but I think lifestyle and healthcare access are larger ones right now.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson