Fujian Province in south-east China has the highest incidence of respiratory and gastrointestinal tract cancers in the whole country. The culprit in all likelihood is well water which is contaminated by high levels of radioactive radon gas.  Radon is a breakdown product of uranium, an element commonly found in many rocks, such as granite. About 1 in 500 people will contract cancer by drinking a liter of radioactive water a day. The tragedy is that the problem can be solved relatively easily. If air is bubbled through the water, the radon dissipates! In North America drinking water is monitored for radioactivity so such problems cannot arise in municipal systems but in certain areas well water may have unacceptable levels of radioactivity.
