The author of the NZ study, environmental engineer Jayne Richards, believes nitrates in water are likely to be a “significant” contributing factor in colorectal cancers, having a similar effect to smoking or eating processed meat. According to the Ministry of Health, NZ has one of the highest bowel cancer rates in the world. The intensification of dairy farming in NZ is said to be the main cause of high nitrate levels in our water. This week’s study found a greater reading of nitrates around the farming strongholds of Canterbury, Southland and the Waikato. Levels tended to be higher in smaller wells close to rural areas.