Groundwater quality in parts of Punjab fails drinking water standards. Uranium has been found above WHO provisional guidance levels in parts of the Malwa, arsenic in parts of the south-west and the bet lands, and fluoride, selenium, nitrate and heavy metals in various districts.
The uranium is generally attributed to geogenic sources concentrated by over-extraction rather than to any industrial cause, though phosphatic fertiliser and coal ash have both been proposed as contributors and the question is not settled.
The state's response has been reverse osmosis plants in affected villages and, in some areas, canal-based piped water supply. Both work where they are maintained.
The health claims made about this contamination in the press have run far ahead of the epidemiology, in the same pattern as the pesticide argument.
What is not disputed is that a substantial number of Punjab villages cannot safely drink their own groundwater, in a state that is the granary of the country.
The deeper the borewell the worse it often is. Several of the contaminants concentrate in the deeper aquifer, so the answer to a falling table can make the quality problem worse rather than better.
The uranium reporting in the Malwa is the most contested. Geological origin, fly ash from thermal plants and fertiliser residue have all been proposed and none has been established.
Testing is the weak link. A village learns its water is unsafe when somebody comes to test it, and the sampling coverage across the state's habitations is partial and irregular.