Regional variation of cancer mortality incidence and its relation to selenium levels in China.

The epidemiological relationship between selenium level and age-adjusted human cancer mortality (incidence) was studied in 24 regions located in eight provinces of China. Statistically significant inverse correlation was found between age-adjusted total cancer death rates and selenium levels in whole blood from local residents. In the areas with high selenium levels, there was significantly lower mortality in both males and females from cancer of the stomach and esophagus. In addition, an inverse correlation between regional distribution of liver cancer incidence and selenium contents in blood and grains in Qidong county, an area with high risk of hepatoma, was observed. With the intention of providing selenium supplements to residents living in low selenium regions, the selenium content in grains was raised by means of foliar spraying of crops with Na2SeO3 solution.