The permissible limit for arsenic established by World Health Organisation is 0.01 mg/l.
Prolonged arsenic contamination is known to cause cancer and skin diseases besides affecting reproductive health. Apart from Assam, arsenic-laced water is a serious problem in West Bengal, Uttar Pradesh, Jharkhand, Chhattisgarh, Bihar and Manipur.
A survey report by the Northeast Institute of Science and Technology also established high fluoride content in groundwater in six districts, five of which are also arsenic-affected. These districts include Kamrup Metro, where Guwahati is situated.
Groundwater in central Assam’s Karbi Anglong was found to have a fluoride content of 15-20 mg/l while in certain areas of Guwahati and outskirts it went up to 6.88 mg/l.
The WHO permissible limit is 1.5 mg/l.
Ingestion of 10-20 mg of fluoride per day for more than 10 years leads to crippling skeletal fluorosis, the report said. Inhabitants of at least half a dozen villages in Karbi Anglong district suffer from fluorosis in varying degrees.