Ministry of Education data shows drinking water at more than 20 schools had nitrate levels of 5.6 milligrams a litre or more - that's at least half the legal limit - but a level that has been linked to serious health outcomes. A recent New Zealand student of more than 750,000 births found an increased risk of premature birth at levels well below 5.6 milligrams, and international research links colorectal cancer to levels as low as one milligram per litre. So why are some children drinking high nitrate water? Keiller MacDuff reports.
