Investigates where the concentrations of nitrate in the Danish drinking water is too high. The investigation was done mainly because of 2 reasons. 1) A group of Danish scientists concluded in a recent study that the risks of getting cancer was present when drinking water with nitrate levels at much lower levels (4 mg nitrate per liter water) than the current official acceptable levels (50 mg nitrate per liter water). The investigation showed that about 3.000 households with a privately-owned water well contained nitrate concentrations which was above the current acceptable levels of 50 mg nitrate per liter water. 2) The investigation was also relevant because the Danish government in the fall 2017 decided to drop the lawful requirement on collecting water samples for analysis for the described water wells – for example sampling the levels of nitrate in the water.