In a study by the Central Pollution Control Board, the Bharalu and Kolong rivers of Assam have featured among 71 most polluted in the country.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/polluted-rivers-editorial
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/assam-tribune
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/river-pollution
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/kolong
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-conservation
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/industrial-pollution
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/central-pollution-control-board-cpcb
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/assam
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/meghalaya