Some people will argue about anything. I don't even know why this topic was brought up. We all know that the best air in the U.S. is West Coast air. It's simple if you think about it. West Coast air has traveled thousands of miles over open ocean depositing any impurities into the vast Pacific before finally reaching the golden coast as nothing more than pure, wholesome air.
If you don't believe me, let's look at the empirical evidence. Where are the best trees in the U.S. grown . . . that's right, in that magnificent West Coast troposphere.