Do the benefits from Cycling outweigh the harm of pollution So in riding to work on a daily basis, do the physiological benefits gained from cycling to work get outweighed by the harm that pollution does to the body? I.e. does it cause more harm that it prevents.  

My concern is that when riding to work, I am breathing harder and riding with the daily traffic, so exposing myself potentially to higher levels of pollution than I would riding on a weekend day or away from heavy traffic.  This has the potential for causing respiratory issues, especially in Arizona where dust particles can cause irritation.  Does this concern negate the positive benefits such as increased respiratory capacity, reduced blood pressure, etc.?
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.)