Free nitrate water testing undertaken by Greenpeace Aotearoa in Southland this week has found high contamination levels in the water supplies of both Gore and Lumsden townships, as well as surrounding rural areas.

Elevated nitrate levels in some water samples tested in Gore on Wednesday reflected that 65% of the town’s water supply is sourced from nitrate contaminated bores located on a dairy farm.

“It was striking to find water samples from public supplies in Gore and Lumsden with nitrate levels greater than 4 milligrams/litre (mg/L)” says Greenpeace lead climate and agriculture campaigner Christine Rose.

“The major concern here is that nitrate above 5 mg/L has been found to increase the risk of preterm birth, according to a recent Californian study.”

80% of New Zealanders have access to water that is under 1 mg/L for nitrate. 800,000 New Zealanders, mostly in rural areas, are exposed to potentially hazardous levels of nitrate above 1 mg/L in drinking water.

The highest nitrate reading of the whole Greenpeace testing programme of over 1000 samples was recorded this week, from a dairy farm in the region. It showed 21.5 mg/L (NO3-N) – almost double the maximum acceptable value for nitrate in drinking water.

“Our testing has revealed concerningly high levels of nitrate in both public town and individual household bore water supplies,” says Rose.

“No-one should have to wonder if the water from their kitchen tap is safe to drink. But for many of the people coming in for testing, this is their reality.”

The maximum acceptable value for nitrate in drinking water is 11.3 mg/L, set in the 1950s in response to Blue Baby Syndrome. Exposure to nitrate levels above this level can prevent the blood from delivering oxygen effectively in the body, posing a serious risk to health. However, emerging evidence from substantive studies around the world shows that there are potential health risks at much lower levels of nitrate in drinking water.

In particular, elevated levels of nitrate in drinking water have been linked to increased risks of bowel cancer and preterm birth. A Danish study found that at over 1 mg/L risks of bowel cancer can increase, while a US study found health risks increased with every additional milligram of nitrate in drinking water.

Greenpeace conducted 112 tests in Lumsden on Tuesday and Gore on Wednesday this week, and preliminary analysis found 65% of samples above the cancer risk level of 1 mg/L, while 20% were above the preterm birth risk level of 5 mg/L. Three samples exceeded the current nitrate standard of 11.3 mg/L including two at or above 21 mg/L. Of all the samples identified as coming from town supplies, 41% showed over 4 mg/L for nitrate.

Worsening nitrate contamination of drinking water is linked to the huge boost in the use of synthetic nitrogen fertiliser, and increase in dairy cow numbers over the past 30 years.

Synthetic nitrogen fertiliser and concentrated cow urine make their way into aquifers, and from there, into people’s bore drinking water. As dairy cow numbers in New Zealand doubled between 1990 and 2019, and the use of synthetic nitrogen fertiliser increased by almost 700%, nitrate contamination also increased with rural communities the worst impacted.

“Access to safe drinking water is a basic human right,” says Rose. “But both household bore and public supplies in these dairy intensive areas are showing concerning levels of nitrate contamination.”

“We’ve heard from farmers that they expect the Government to regulate cow numbers, and phase out synthetic nitrogen fertiliser and imported feed. Intensive dairying is putting their health and communities at risk.”

Greenpeace is continuing its water testing programme in Ashburton this Saturday. In 2021, the organisation’s testing found that the area’s drinking water was “loaded with nitrate contamination”.

“Everyone should be able to trust that their water is safe to drink,” says Rose. “Big Dairy is taking that right from rural New Zealanders.”