The environment minister says New Zealand will continue to follow WHO guidelines on nitrate levels in the water despite international research finding much lower levels could still cause cancer.
Environment Minister David Parker. Photo: RNZ/ Dom Thomas
The first study into the country's nitrate in drinking water says one in six people could be drinking water polluted enough to cause colorectal cancer.
The research, overseen by Victoria and Otago Universities, calls for action from the horticulture and dairy industries.
The study used overseas research including a major Danish study that found a link with bowel cancer when levels were as low as 0.87mg/L of water.
The current safe level in New Zealand, as mandated by the World Health Organisation (WHO) was 11mg/L of water.
Earlier in February, Otago University senior research fellow Dr Tim Chambers said New Zealand should take a precautionary approach and reduce the maximum level from 11.3mg/L to 1mg/L.
But Environment Minister David Parker told Morning Report that WHO guidelines were being followed.
"So, there's no plan to immediately reduce the New Zealand standard for nitrates in drinking water."
"Maybe there'll be stricter limits in the future on the amount of nitrogenous fertiliser than can be applied" - Environment Minister David Parker
He acknowledged the Danish study and said more research needed to be done in Aotearoa.
"I'm sure it wouldn't be a shortage of money that would stop it [research] being done but that's really for the Ministry of Health, whether they see it to be a priority in light of that Danish study."
He said with regard to the health of rivers, there was already a cap on synthetic nitrogen that could be applied to land.
Some people were previously applying 300kg per annum so a reduction to 190kg was significant but there were other measures needed too, he said.
"Industry are bringing forward new cultivars that are diuretic that cause smaller urine patches, therefore less nitrates are lost to the waterways because the grass can take them up."
Yesterday Victoria University ecologist Mike Joy said cow urine was one of the major contributors to increased nitrate levels.
"He [Mike Joy] is right that there have been serious problems in south Canterbury from a river health point of view. I don't know yet whether he is right in respect of human health issues," the minister said.
On the back of the Danish study, Parker has asked the Health Ministry and the Director-General of Health to "look into it".
He said Ministry for Primary Industries was doing research into regenerative farming which would be less reliant on fertilisers.
"In addition to that, there will be some land-use change. There'll be new cultivars and maybe there'll be stricter limits in the future on the amount of nitrogenous fertiliser than can be applied."
He said it would take evidence of human health issues to bring down the limit of nitrate levels.
"We'll see."
Councils could enforce tougher limits if they deemed it necessary for river health, Parker said.
"It's not necessary now; two: you need stability in the system; three: a limit that applies everywhere in the country ... if you drop it lower, might not be correct for some parts."
He said the government had to be careful that it was not "over-regulating parts of the system".