Arsenic levels have risen to alarming levels in many districts of the north-eastern Indian state of Bihar, officials say.
A state government survey has revealed that arsenic levels in up to 12 districts of the state of Bihar are now a threat to life. Patna, the state capital, is among the affected areas.
The Bihar Public Health and Engineering Department (PHED) study, according to the BBC, reveals that the average arsenic content in drinking water in the 12 districts is 500 parts per billion (ppb).
The World Health Organisation says that levels above 10 ppb present health hazards. The Indian health authorities have fixed the permissible limit at 50ppb.
Apart from Patna, the other worst affected districts are Darbhanga, Bhojpur, Vaishali, Bhagalpur, Samastipur, Buxar, Khagaria, Begusarai, Katihar, Chapra and Munger.
Arsenic, an odourless and tasteless semi-metal element, occurs naturally in the environment and sometimes as a by-product of agricultural and industrial activities.
In many villages falling in the 12 districts people have complained of weakening and bending of the bones and dreadful rashes and lumps on the skin.
With the help of the United Nations children's agency, Unicef, Bihar's Public Health & Education Department has been marking hand pumps and tube wells with different colours to indicate whether the water is safe to drink.
The first signs that arsenic-contaminated water might be a major health issue emerged in the 1980s, with the documentation of poisoned communities in Bangladesh and the Indian state of West Bengal, which neighbours Bihar.