Do the benefits from Cycling outweigh the harm of pollution
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2920084/ - "On average, the estimated health benefits of cycling were substantially larger than the risks relative to car driving for individuals shifting their mode of transport."

http://www.ncbi.nlm.nih.gov/pubmed/22124913 - "We estimate that beneficial effects of increased physical activity are substantially larger (3-14 months gained) than the potential mortality effect of increased inhaled air pollution doses (0.8-40 days lost) and the increase in traffic accidents (5-9 days lost)."

http://www.ncbi.nlm.nih.gov/pubmed/21816732 - "Public bicycle sharing initiatives such as Bicing in Barcelona have greater benefits than risks to health"

(Maybe your Arizona dust is an exception though. And dust masks do make it harder to breathe hard comfortably.)