Natural state? Water purity measure corrected

The equation for measuring water purity has been corrected but a freshwater ecologist questions whether this adjustment is sufficient to prevent pollution. The official equation measuring the human impact on groundwater has been revised to better reflect levels of pollution. Water scientist Dr Mike Joy has been campaigning for years to get the Ministry of the Environment to adjust the way they measure water purity. He has had something of a win. Admitting they had the figures wrong, Stats NZ has downgraded the 3 grams of nitrate allowed per cubic metre of water for it to be considered in a "natural state". Dr Mike Joy joins Kathryn to discuss why these measures are so important.