Michael Baker: Otago University professor on the new study showing the link between nitrate in drinking water and premature births

New evidence suggests nitrate in drinking water could increase the risk of premature birth. 

A study of more than 700,000 birth records and estimated nitrate levels at the mother's residence, found it potentially contributes to about 4 percent of pre-term births every year. 

Otago University professor Michael Baker says this research, paired with similar studies carried out overseas, adds up to the need for an evaluation of nitrate levels in water.

"Denmark has recently reviewed its levels and it's dropped the level to 1.3 milligrams per litre, so that's about a tenth of that current level that we have in New Zealand. And they looked at a lot of evidence to do that." 

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Episode Transcript

Speaker 1 (00:00):
Cure.

Speaker 2 (00:01):
So what level is too high?

Speaker 1 (00:04):
Well, the current level sounds a bit technical, but eleven
point three mitigrams per liter of night rates and water
is the global regulatory limit, and that appears too high
because we've got this study showing an association between high
night rates and pre term birth, which is a real

(00:25):
problem across the globe. And also we've got a lot
of international studies, a growing number finding similar results. And
of course is the other association with bowel cancer and
night rates and drinking water. So I think it's adding
up to the need for us to revisit our level
and lower it. And you've got a country like Denmark

(00:48):
has recently reviewed its level levels and it's dropped the
level to one point three mitigrams per liter. So that's
about a tenth of that current level we have in
New Zealand, and they looked a lot of evidence to
do that and they convender an expert group to come

(01:08):
up with that level.

Speaker 2 (01:11):
Now, where would we find levels that you consider high
enough to cause preterm births in this country?

Speaker 1 (01:17):
Well, the good news is that about eighty percent of
New Zealanders are on public water supplies and their levels
are low, not really causing a problem. But it's about
twenty percent of people who are living more in rural
areas with their own water supplies, and unfortunately they're often
drawing water which is very heavily contaminated by surface water,

(01:39):
which in turn is contaminated from intensive agriculture.

Speaker 2 (01:44):
Okay, now, it's been said that most of our nitrate
exposure actually comes from what we eat, not what we drink.
What do you say to that.

Speaker 1 (01:51):
That's correct, and that's very well established. The difference is
that your body metabolizes the nitrates and food very differently
because you've got antioxidants there and they don't cause the
same effects. Whereas water that's coming in regularly, it doesn't
have that same effect from other substances in the water

(02:14):
to protect or in the food to protect you from
the laud exposure. So it's a very different form of exposure.
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