Opinion: Why are activists causing unnecessary alarm, Dr Jacqueline Rowarth asks.
Nobody wants a baby to be born prematurely, and the latest media shock-horror link to nitrate in drinking water is, yet again, a distraction from the real causes already identified in New Zealand: social and economic inequalities in health such as smoking, low education and poverty which disproportionately affect Māori wahine/women.
This is from the NZ Child and Youth Epidemiology 2015 report which also states that "wahine/women with a maternal age under 20 or over 35 years have higher rates of prematurity".
In New Zealand approximately 7.4 per cent of births are defined as preterm (less than 37 weeks of gestation) and there has been no significant change in percentage this century.
Between 2010 and 2014, preterm birth rates were close to the New Zealand rate in all DHBs but were higher in Counties Manukau, Taranaki, Hawke's Bay, Hutt Valley, Capital & Coast, Canterbury, West Coast, and Southern DHBs, and lower in Northland, Auckland, Waitemata, Whanganui, Wairarapa, Nelson Marlborough and South Canterbury DHBs.
A check of nitrate in ground water and wells indicates no relationship between higher nitrate and increased incidence of preterm pregnancies.
Whatever region is examined, very few wells are considered to be over the World Health Guideline for nitrate in drinking water (50 mg/l) and few are even above half the guideline recommendation.
In Hawke's Bay, one of the areas picked out for higher preterm pregnancies, approximately 6 per cent of well samples were between half the drinking water standard and the standard. Most of these wells were not used for domestic purposes.
In the Waikato, which is slightly below the average for preterm pregnancies, more than 9 per cent of groundwater sites have nitrate concentrations above the accepted drinking water guideline and a third have concentrations over half this value.
With no relationship apparent in New Zealand, questions should be asked about why the report from overseas received such coverage.
People are being scared completely unnecessarily, just as they were when nitrate in drinking water was linked to colorectal cancer (CRC) because of research in Denmark.
At the time of the CRC media fuss, University of Otago Professor of Colorectal Surgery Frank Frizzelle pointed out that the nitrate-CRC research globally was inconclusive, "there is no logical reason or cause and effect."
The Stanford University research which started the pre-term baby furore has tried to find cause and effect, but the goal of estimating the average concentration of nitrate in public tap water served to each woman during pregnancy overlooks the vast number of sources of dietary nitrate available.
The World Health Organisation (WHO) reports that drinking-water nitrate is usually less than 14 per cent of total dietary nitrate, but the figure varies widely.
Dr Jacqueline Rowarth. Photo / Supplied
Forty per cent has been indicated as possible in the Netherlands where nitrate concentration has been described by the European Environment Agency as "often higher than the drinking water standard".
Reassuringly for pregnant women everywhere, research published in 2020 reports a significant decrease in the Netherlands in preterm birth from 6.1 per cent in 2010 to 5.6 per cent in 2015 – so nitrate in drinking water is not causing a problem.
Despite this, the Stanford University researchers attempted to correct for a number of factors such as age, race, number of pregnancies and infant gender.
They could not, however, consider other environmental co-exposures, including other contaminants in drinking water and acknowledged that it is possible that exposure to co- occurring contaminants or their interactions could contribute to the observed elevated odds of pre-term birth.
Previous research in the San Joaquin valley, one of the areas in the pre-term study, found a strong association between pesticide use and adverse birth outcomes.
Researchers from the University of Cincinnati College of Medicine have added prenatal exposure to common drugs such as amoxicillin, caffeine, chlorpheniramine, promethazine, and pseudoephedrine, in conjunction with higher levels of dietary nitrites (including animal, plant, and total nitrites) to pre-term problems.
Pre-term pregnancies are complicated and in searching for cause and effect, the Stanford researchers quoted conclusions from 1951 on the blue baby syndrome - which has been disproved by the WHO.
Listen to Jamie Mackay interview Dr Jacqueline Rowarth on The Country below:
"A review of the literature found no incidences of methaemoglobinaemia at nitrate concentrations below 45 mg/L nitrate nitrogen in drinking-water for bottle-fed infants aged under 6 months. Most studies failed to account for bacterial contamination."
None of the science or science-based explanations has stopped activists regurgitating all the old arguments of colorectal cancer and blue baby syndrome with the new research on preterm babies ... and causing unnecessary alarm.
When the CRC research hit the news, Professor Frizelle cautioned against over-interpretation "particularly in the environment we are in where we have a big anti-dairy lobby and water purity lobby who want to throw everything they can on the fire to say it is causing all this damage".
The warnings need repeating as they don't appear to have been heard.
Of note for activists campaigning against cows is that in the Waikato report on drinking water, the Regional Council highlighted the fact that higher nitrate concentrations were found at market gardening sites than other sites.
But preterm pregnancies are related to other issues and they are where we should be concentrating efforts.
• Dr Jacqueline Rowarth is an adjunct professor with Lincoln University and a farmer-elected director on the Boards of DairyNZ and Ravensdown. The analysis and conclusions above are her own. jsrowarth@gmail.com
