tls: "A quick glance at your fellow passengers when getting off the plane in any American airport will reveal that Americans are in much worse health than the Chinese, air quality be damned. There is nothing passive about running every day."

On my end, I would like to know what my risk is and what the consequences of certain behaviors are. For instance, when you run, you breath in more air and more particles contained in that air. I would like to know whether the obvious benefits of jogging are outweighed by the increased risk of lung disease caused by inhaling more particulates when exercising strenuously. Also, although Chinese air passengers may generally appear healthier than American passengers, the Chinese have a lower life expectancy than Americans.

My 12-year-old son has in some ways performed a perfect small experiment in that regard. His asthma symptoms went away one year ago. Just by chance he downloaded an Ipod app that has vigorous exercise programs and started using it when he arrived in Wuhan 6 weeks ago. Hasn't had any problems caused by the exercise. Obviously, this is not a rigorous scientific result, but it is an interesting first look at the issue.

I would add that jogging is not a passive physical activity, but jogging without making any effort to find out the benefits and detriments in China is passive with respect to assessing health risks. I am not judging other people who don't assess their health risks; I am simply stating what I would do. We all have limited time and each us will have his or her own way of using time wisely.