3. Guidelines and standards

In 1993, the WHO lowered the health-based guideline for arsenic concentration in drinking water from 50 mg/L to 10 mg/L. This guideline has remained provisional although there is clear evidence of hazard, because there is uncertainty about the actual risk from long-term exposure to very low arsenic concentrations.

Most countries have adopted the WHO provisional guideline but the 10 mg/L is not currently feasible for a number of countries, including Bangladesh and India. These and many other countries retain the former WHO guideline of 50 mg/L. The most stringent national standard has been set at 7 mg/L in Australia.