A new study carried out in Denmark and published in the International Journal of Cancer concluded that there is an increase risk of colorectal cancer in connection with nitrates in drinking water. The dangerous rates are also at concentrations far below the current drinking water standards and are mainly seen in private water supplies. It is often from fertilizer used in agricultural production.
Researchers calculated how much nitrates the subjects were exposed to where they lived and compared this to information about cancer diagnosis. A total of 2.7 million people were followed between 1978 and 2011. Nitrate was measured in more than 200,000 drinking water samples, making the study the largest and most detail in the area.
Yearly about 5,000 Danes contract colorectal cancer. In this study people who were exposed to the highest concentrations of nitrates in drinking water (about 9.3 mg per liter of water) had a 15% greater risk of getting colorectal cancer when compared to those who had the least exposure(less than 1.3 mg per liter of water). The current standard for nitrates in Denmark is 50 mg per liter of water but in the study the colorectal cancer rates were already seen in those drinking 4 mg per liter of water. The standard set complies with that set by the WHO. Changes in these standards should be made.