yes, pollution in China is severe in most of cities/towns. I know summer days are prime time for hiking, biking...the problems are the more intense the activity, the faster a person breathes and the greater the amount air breathed in. The effects of air pollution can include respiratory discomfort, difficulty breathing, tightness in the chest, reduced lung function, bronchitis and asthma attacks. I suggest that if you live in a city where summer smog is a factor, try exercising in the morning, when it's cooler, and before traffic starts to build. Choose parks, recreation areas and quiet roads situated away from traffic. When air quality is particularly bad, consider exercising indoors, reducing workout intensity, or holding off for a day.