Geologic environments and health in China.

Editorial Natural geologic environments in China affect human health in a variety of ways through interactions between geochemical, hydro-logic, and biologic processes and human activities. Numerous national-scale cases serve as examples, including correlations between the distribution of Keshan and Kaschin-Beck diseases (both thought to be associated with nutritional deficiencies) and the northeast– southwest-oriented low selenium belt in temperate forests and for-est–grass regions (Fang 2002). The areas of fluorine-related endemic ailments, which occur in one-half of China's 2,171 counties, have a distribution that tends to match that of regions with high-fluorine rocks, aquifers, springs, and coals (Cai 1995). Environmental factors such as climate, along with the human activities and cultural customs, can also enhance health impacts in areas with high natural background concentrations of hazardous geo-chemical compounds. The serious arsenicism in parts of Guizhou Province is related not only to the high arsenic content (as high as 35,000 ppm) in local Permian coal deposits but also to the cold and humid winter conditions on the high plateau in the western part of the province. Residents there heat their homes by burning locally obtained coal in open fires. Because most houses do not have chimneys , the arsenic-containing smoke goes directly into the living areas. Moreover, residents often hang corn and chili peppers over the fires in their homes to dry them for later use. This practice can transfer the arsenic from the coal coating and permeating the peppers and corn by sublimation, and then of course entering the body when the food is eaten (Zheng 1996). Naturally occurring radioactive radon gas is also a health problem in some regions of China. In these areas the radon, which has been linked to lung cancer, can enter homes either through direct emission from rocks or soils, or through bricks that have been made from radon-rich mining waste. Some health problems are related to special landscape settings. Tens of millions of people in China rely on karst aquifers for drinking water. These aquifers are formed by dissolution of soluble limestone bedrock, which forms caves, sinkholes, and other related features; the groundwater resources that these aquifers contain are vulnerable to contamination. Such problems are widespread: in southwest China, limestone covers an area of more than 500,000 km 2. Because of karst development in these areas, water resources in the region are based on nearly 3,000 underground streams, with a total length of some 14,000 km …