Fluoride is known to contaminate groundwater reserves globally. Excess fluoride, wherever present in groundwater in INdia, is mainly in the concentration range of 1.5 to 6.5 mg L-1 against its critical limit of 1.5 mg L-1 in drinking water.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/defluoridation-groundwater-agra-city-using-low-cost-adsorbents
[2] http://admin.indiaenvironmentportal.org.in/category/author/r-p-singh
[3] http://admin.indiaenvironmentportal.org.in/category/author/y-singh
[4] http://admin.indiaenvironmentportal.org.in/category/author/d-swaroop
[5] http://admin.indiaenvironmentportal.org.in/category/journal/bulletin-environmental-contamination-and-toxicology
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/fluoride
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/agra-t
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/groundwater-quality
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health