New Zealand's leading environmental organisations are urging the Government to slash the nitrate pollution limit in waterways, after studies linked high levels of nitrate to cancer and premature births.
The current health limit of nitrate in drinking water is 11.3 mg/L, in line with the recommended limit set by the World Health Organization. However, that number is over ten times higher than 0.87 mg/L, the nitrate level linked to increased bowel cancer risk in a major Danish study published in 2018.
Speaking to Breakfast this morning, Dr Tim Chambers, a senior research fellow in the health, environment and infection research unit at the University of Otago, said evidence showed there was a link between adverse health effects and high levels of nitrate in drinking water.
"The level we need to set it at is still up for debate but we know the lower the limit is, the safer it will be," Chambers said.
The Danish study was the most comprehensive piece of evidence available, Chambers said, as it had surveyed the effects of nitrate levels on over 2 million people over a 15 to 20 year period.
Despite its findings, the WHO had yet to revise its limits, Chambers said, which were only set to counter blue baby syndrome, and not emerging evidence of bowel cancer and premature birth.
Joining Chambers on Breakfast was Greenpeace senior advisor Steve Abel, who pointed to the steep increase in the use of synthetic nitrogen fertiliser on farms in the past 30 years as the cause for high levels of nitrate in New Zealand's drinking water.
"What we’ve seen is an increase in the amount of nitrate in groundwater contamination. The cause of that is a big increase in the use of synthetic nitrogen fertiliser, a big intensification of dairying primarily, that leads to nitrogen leeching down into the ground, into groundwater and into people’s drinking water.
"We’ve got to lower the nitrate levels for ecological reasons, but also for human health reasons."
Greenpeace had recently conducted nitrate testing in Canterbury, including Dunsandel and Woodend, discovering concerningly high levels of nitrate contamination.
Twenty-seven per cent of bores in Dunsandel were above the 5 mg/L limit for premature birth, while 75 per cent of bores in the town were above the Danish study limit for potential risk of bowel cancer.
Four bores were also found to be well over the legal health limit, Abel describing them as "off the Richter scale". Abel told 1 NEWS the highest reading was 12.9 mg/L.
Those numbers were of particular concern given Christchurch's drinking water was supplied entirely from groundwater. Nationally 53 per cent of drinking water comes from the ground.
However, Abel said it was not the fault of the farmers, but rather fertiliser companies Ravensdown and Ballance, who distributed 98 per cent of synthetic nitrogen fertiliser in New Zealand.
"They’ve been pushing farmers to put it on the land to grow the grass, to cram the land with cows. They are the ones who are liable, it is not about blaming farmers," Abel said.
"We do not need this synthetic nitrogen fertiliser in our agricultural systems, in fact if we want to have healthy land, healthy rivers and healthy people we need to get rid of synthetic nitrogen fertiliser. Moving to regenerative and organic forms of farming has to be the future."
In response, the fertiliser companies and the Fertiliser Association of New Zealand told 1 NEWS they were determined to assist their farmer owners with reducing environmental impact and said banning synthetic nitrogen fertiliser would leave a gaping hole in the economy.
"It is not for an activist group or a farmer-owned co-operative to tell farmers which system they must adopt," they said in a statement.
"Real livelihoods and local communities are at stake. Banning manufactured N fertiliser would leave a $7 billion hole and cost 70,000 jobs."
The companies also rejected the claim they "pushed" synthetic fertiliser onto farmers, since the collectives were owned by those who used the product themselves.
"In Canterbury, farms are already operating within some of the strictest limits in the country. As a result Environment Canterbury says that we are starting to see improvements in some rivers, but acknowledge that improvements in groundwater will take longer."
Abel told Breakfast the Government needed to "act now" and reduce the nitrate levels dramatically to under 1 mg/L, in line with evidence from the Danish study.
"This is an opportunity for us to lead the world and the challenges we face both for the environment and for human health and the climate," he said.
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