20 Million People at Risk in China for Arsenic Contamination in Groundwater

There may be an extra ingredient in China's groundwater: arsenic. Scientists have discovered that almost 20 million people across the country are at risk for being exposed to the chemical in their cooking and drinking water.

Officials have known that arsenic has polluted certain groundwater resources in China since the 1960s. Unfortunately, estimates of the number of affected people have risen each year. In fact, the most recent survey between 2001 and 2005 revealed that more than 5 percent of the 445,000 wells tested had arsenic levels higher than 50 µg/L.

Arsenic is one of the most common inorganic contaminants found in drinking water worldwide. While the inorganic salts of arsenic are tasteless and odorous, they can be highly toxic to humans. If ingested over long periods, even low concentrations can cause damage to a person's health.

Unfortunately, it's difficult for researchers to test every well in China. The sheer size of the country would make that endeavor last for years. In order to get past this issue, scientists developed a statistical risk model making use of existing data on geology, soil characteristics and topographical features. The model was calibrated using available arsenic measurements.

The model's predictions agreed with both safe and unsafe areas that had already been measured. In addition, it showed large areas that are possibly at risk. These areas included the basins of the Tarim (Xinjiang), Ejina (Inner Mongolia) and Heihe (Gansu). In fact, concentrations of arsenic above 10 µg/L are predicted for a total area of 580,000 km2. This means that about 20 million people across China live in high-risk areas for arsenic.

"The figure may be an overestimate, as we lack reliable information on the number of people with treated water supplies," said Annette Johnson, one of the researchers, in a news release.

The findings reveal that arsenic is a huge problem in China.  Yet the new method permits more targeted sampling campaigns and saves time in identifying populations at risk. This could be extremely useful into the future.

The findings are published in the journal Science.