Run-Yun: I had a similar condition when I went to Malaysia for a short visit. As soon as I hit Kuala Lumpar, I had a coughing and hacking condition until I left (or fled, more like it). Doesn't matter where the pollution comes from- which country it originated from makes no difference and doesn't do anything to explain or treat your condition. What's important is if something is in the air that affects your breathing. Maybe a result of pollution, maybe a result of exercise induced asthma, maybe there's some extra pollen in the air- who knows? Whichever it is, see a doctor. They can take a thorough history and hopefully isolate the problem.