Tests have so far detected the presence of excess fluoride and arsenic in 449 blocks in five districts and in 614 blocks in 18 districts of the State respectively.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/excess-fluoride-1063-blocks
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/assam-tribune
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-harvesting
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-quality
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/fluoride
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/drinking-water
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-supply
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/assam