Paul Almacy/WHO

Arsenic is an element widely distributed in earth’s crust, and in groundwater in many countries. Long-term intake of arsenic contaminated water leads to arsenic poisoning or arsenicosis, with cancer of skin, bladder, kidney or lung or diseases of skin (colour changes, and hard patches on palms and soles), or blood vessels of legs and feet. Fresh evidence indicates possible association between intake of contaminated water to onset of diabetes, hypertension and reproductive disorders.

In India, the states of West Bengal, Jharkhand, Bihar, Uttar Pradesh, Assam, Manipur and Chhattisgarh are reported to be most affected by arsenic contamination of groundwater above the permissible level. WHO’s provisional guideline value for arsenic in drinking water - 0.01 mg/l (10 μg/l) (Source: Guidelines for drinking water quality, 4th edition, WHO, 2011). Permissible limit of arsenic in India in absence of an alternative source - 0.05 mg/l (50 μg/l). (Source: Indian Standards for Drinking Water, second revision of IS 10500, 2004).