The permissible limit for nitrates is 40 milligrams a litre, but in most areas, the presence of nitrates ranges between 45 and 100 mg/ litre.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/bengaluru-ground-water-high-carcinogens
[2] http://admin.indiaenvironmentportal.org.in/category/author/bosky-khanna
[3] http://admin.indiaenvironmentportal.org.in/category/newspaper/deccan-herald-bangalore
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/karnataka
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/groundwater
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/bangalore-d
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/groundwater-pollution
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/carcinogenicity
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/central-groundwater-board-cgwb
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/groundwater-quality
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/waste-disposal
[12] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-pollution