Trog, you must be in SLC! Worse polution in the US... Anyways, i spent some time in thailand a few years ago, theres some 10million people +/- 3million, the gov dosent even have an accurate count... i noticed there were TONS of bicycle commuters, and 95% of them wore a simple cotton face mask, not just bike commuters, but alot of people just walking on the sidewalks. Another quick note, drivers in there car are subject to 7 times more polution then you on your bike, i read this somewhere, i'll try to get a refrence for ya...
How about getting a neopreen ski mask? Id think that would help a little, the biggest help would to drink alot of water, both before and after your commute, it may not help your lungs, but it will flush the kidneys of all the fun stuff you inhale during the day.