Nitrate risk to unborn babies focus of $1.2m water study

Scientists seeking to determine whether nitrates in drinking water have an impact on unborn babies have received $1.2 million to undertake a study of 700,000 births in New Zealand.

The researchers, of the University of Otago, will map pregnant people’s exposure to nitrate during pregnancy, to determine any links to premature births.

In doing so, they will create a national database of contaminants in drinking water in New Zealand for the first time – opening the door to other research into how water affects other health issues.

Nitrate is one of the country’s most common drinking water contaminants, largely driven by agricultural activity. Nitrates leaching into water from dairy farming has increased substantially since 1990.

Dr Tim Chambers, the study lead, applied for the grant from the Health Research Council after mounting evidence from overseas suggested that nitrate was linked to pre-term births and possibly to birth defects.

To be considered safe, drinking water in New Zealand needs under 11.3 milligrams of nitrate-nitrogen per litre (mg/L). That level was set to ensure families avoid blue baby syndrome, after it was discovered that nitrates in baby formula were making babies sick.

However, studies now show there may also be a link between nitrates and unborn babies.

A study from California, involving 1.4 million babies, caused particular concern. It tracked the nitrate levels women were exposed to in subsequent pregnancies and found the risk of early pre-term birth (at least nine weeks early) increased by half when nitrates in drinking water were above 5mg/L. If nitrate levels were above 10mg/L the odds of a pre-term birth more than doubled.

After the study was released, the Liggins Institute, New Zealand’s authority on pregnancy and baby health, was commissioned by the Ministry of Health to review the evidence on nitrate and birth outcomes. It concluded that findings were ‘‘inconsistent’’ and said more work was needed.

Chambers’ team now plans to undertake that work, by creating a drinking water database that combines information from New Zealand’s 57 local councils, mapping it against 700,000 births over 15 years to measure nitrate exposure levels.

He said the work would take three years.

Data shows an increasing number of rural families across Aotearoa are drinking water with levels that are considered unsafe even by current measures – most of it from unregulated, private bores.

One analysis said as many as 138,000 New Zealanders could be on water supplies with nitrate levels above 5mg.