Nitrates in US drinking water may cost US$8 billion a year

Friday, 26 July 2019

A denitrification wall at Silverstream Reserve, North Canterbury, has already significantly reduced nitrate levels in less than two months. (Video first published in January 2019)

Cancers potentially linked to high nitrate levels in drinking water could be costing the United States as much as US$8 billion (NZ$12b) every year in medical care and lost productivity.

The figure is from a United States study of the annual economic hit that country takes from healthcare for those with birth defects and cancer, which epidemiological evidence connects with nitrates in drinking water.

In the paper in Environmental Research, five scientists from North Carolina's Duke University and the Environmental Working Group in Washington DC used national nitrates data and risk ratios to work out how many adverse birth cases and cancers could be related to nitrate-contaminated drinking water.

A United States study shows exposure to nitrates in drinking water supplies could cost the country $US1.5 billion in cancer treatment alone each year. (File photo)

They found about 4700 cases of either very low birth weight, very pre-term birth or neutral tube defects could be attributed to such exposure.

**READ MORE:

A farm worker moves dairy cows to the milking shed in heavy rain. North Canterbury's nitrate levels are affected by polluted water flowing into aquifers from dairy farms. (File photo)

* ECan asks Govt to prioritise studies of links between nitrates and health

* ECan councillor says proposed plan changes don't go far enough to protect drinking water

The official opening in 2015 of stage one of the Central Plains Water irrigation scheme by then Prime Minister John Key, with dairy cows crossing from paddock to paddock.

* Christchurch's pure drinking water could be contaminated due to farming

* Environmentalists 'alarmed' but Environment Canterbury says water survey results 'expected'**

The researchers also discovered between 2300 and 12,594 annual nitrate-attributable cancer cases in the US, with the annual burden of cancer care costing between US$250 million and US$1.5b, along with lost productivity of US$1.3b to US$6.5b a year.

Environment Canterbury chief scientist Dr Tim Davie says Christchurch's drinking water is 'definitely' safe and will 'continue to be so', but will not be as pristine. (Video first published in December 2017)

Victoria University of Wellington freshwater ecologist Dr Mike Joy told Stuff the US figures showed what a drain high nitrate levels could be on individuals' health and on the economy.

New Zealanders and agencies here needed to be aware of the scale of this burden, he said.

The leader of a ground-breaking Danish study that followed 2.7 million Danes from 1978 to 2011, Dr Jörg Schullehner from Aarhus University, said last year those exposed to nitrate levels above 0.21 milligrams per litre of water had a 15 per cent greater risk of getting colorectal cancer and those exposed to greater than 0.87mg/l had 'significant' increased risk.

According to the US paper, exposure to nitrates in drinking water can account for up to 8 per cent of total colorectal cancer cases, of which between 12 per cent and 24 per cent are due to the nitrate exposure of those who use private wells, especially those whose well water has 1.1mg/l or more of nitrate-nitrogen.

Environment Canterbury (ECan) this week sent a letter to Minister of Health Dr David Clark asking him to prioritise research into the relationship between nitrate levels and colorectal cancer. The current maximum acceptable level of nitrate-nitrogen is 11.3mg/l, set in the national drinking water standards.

A spokesman said ECan would not release the letter publicly until Clark had responded.

Forest & Bird and the Public Health Association New Zealand recently wrote to ECan suggesting the council apply a 'precautionary approach' to managing high nitrate levels in Canterbury wells.

But the response from ECan chief executive Bill Bayfield has irked them.

Bayfield said managing nitrate was 'a critical component of what we do', as 'significant' work over the past nine years to control leaching showed.

'We also know that this work hasn't finished.

'Nitrate takes decades to travel through groundwater, and we can't go back and reduce leaching that occurred in the 1990s, so we do expect nitrate levels to rise before the improvements from today's strict farming rules become apparent,' Bayfield said.

Forest & Bird freshwater advocate Annabeth Cohen said ECan was 'refusing to show leadership' when it was known nitrates posed a risk to health 'at lower levels than currently exist in much of Canterbury's groundwater'.

'The freshwater environment in Canterbury is past the point of crisis and we are potentially heading for a disaster in human health. ECan is wasting time and dodging responsibility.'