In some countries, arsenic is the most important chemical pollutant in ground water and drinking water. The Bengal Delta region is particularly affected as 35 million people have been drinking arsenic-rich water for the past 20-30 years, of which one million are currently suffering from chronic arsenic poisoning. In the Red River Delta around the Vietnamese capital of Hanoi, EAWAG researchers have recently identified another highly arsenic contaminated groundwater area. In some locations, the contamination in Vietnam exceeds the standard value of 10 µg arsenic per liter recommended by the World Health Organization (WHO) 300 times. Measures to mitigate the arsenic problem include not only the development of low-cost arsenic detection and easy to use arsenic removal methods, but also dissemination of information to professionals and consulting services to public authorities.