Research has shown that groundwater resources in certain provinces of China are contaminated with arsenic and that the numbers of affected people have risen year by year.
In the most recent survey - conducted by the Chinese Ministry of Health between 2001 and 2005 - more than 20,000 (5%) of the 445,000 wells tested showed arsenic concentrations higher than 50 µg/L. According to official estimates, almost 6 million people consume drinking water with an arsenic content of more than 50 µg/L and almost 15 million are exposed to concentrations exceeding 10 µg/L (the guideline value recommended by the WHO).
Given the sheer size of China and the time and expense involved in testing for arsenic contamination, several more decades would probably be required to screen all of the millions of groundwater wells.
Accordingly, a group of researchers from Eawag and the China Medical University in Shenyang de-veloped a statistical risk model making use of existing data on geology, soil characteristics and topographic features. This model was calibrated using available arsenic measurements. The predictions of unsafe or safe areas showed a high level of agreement, both for known high-risk areas and for areas where elevated arsenic levels had been ruled out by sampling campaigns.