New Zealand has one of the highest rates of bowel cancer in the world and a recent study has found there's a link between nitrate in water and the risk of developing this cancer.
In some areas around the country, nitrate levels in the water are higher than what is recommended in the study.
So the obvious question is, could drinking it be contributing to our high bowel cancer numbers?
That's what Victoria University's Mike Joy and Otago University's Michael Baker have been looking into. Professor of Public Health Michael Baker explains what the concerns are.