Guwahati, June 18 -- By Nabarun Guha/Mongabay

Every day, 21-year-old Amjad Hussain, from Tapatjuri village in the Nagaon district of Assam, walks one kilometre to his neighbour Dilwar Hussain's house, where he weaves patis (mats) made from the agar tree to earn an income. His family considers this a small miracle considering that a few years ago, Amjad couldn't even take a step without a walking stick.

"Three of my sons developed bodily deformations, which we later learnt was because of the water we drink," says Amjad's mother, Halima Khatun. Her sons were showing symptoms of skeletal fluorosis, which is caused by consuming water with excess fluoride content. Her daughter was spared from this 'pani wala bemar' (water-borne disease), she...