Nitrate in drinking water increases the risk of colorectal cancer, study finds

Nitrate in groundwater and drinking water, which primarily comes from fertilisers used in the agricultural production, has not only been subject to decades of environmental awareness -- it has also been suspected of increasing the risk of cancer. The largest epidemiological study ever carried out in this area now shows that there is a correlation -- also when the amount of nitrate in the drinking water is far below the current drinking water standard.

https://www.sciencedaily.com/releases/2018/02/180220095019.htm