Water Scarcity

The pressure on water resources is increasing rapidly. Nowhere is this more felt than in Asia, home to 60% of the world’s population.

The contamination of groundwater with arsenic poses a risk to the health of millions of people, especially in the densely populated river deltas of Southeast Asia. To date, no method has been available for identifying high-risk areas without conducting costly sampling campaigns.

Arsenic is one of the most important inorganic contaminants found in drinking water. This metalloid occurs as a natural component of underground rocks worldwide, with small quantities being dissolved in groundwater as a result of weathering. The inorganic salts of arsenic are tasteless and odourless, but highly toxic to humans. If ingested over long periods, even low concentrations can cause damage to health, including hyperpigmentation of the skin, disorders of liver and kidney function, and various types of cancer.

Problems arise from the fact that firstly, arsenic concentrations can vary widely at the local level and, secondly, in many areas people are completely unaware of the risk because their well water or groundwater has never been tested for arsenic. Arsenic concentrations below 10 µg/L are deemed to be safe. This concentration is therefore recommended by the World Health Organization as a guideline value for arsenic in drinking water.

In the deltas of the Red River and the Mekong, Eawag detected arsenic concentrations exceeding 100 µg/L in one in five of the samples analysed, with maximum values as high as 3000 µg/L. In the Irrawaddy delta (Myanmar), a study supported by Unicef found arsenic concentrations of more than 50 µg/L at two thirds of the sampled wells.