The amount of fluoride added to Dunedin's tap water has
been regularly dropping below Ministry of Health
guidelines. Photo supplied.
The amount of fluoride being added to Dunedin's drinking
water is regularly dropping below Ministry of Health
guidelines, following a Dunedin City Council decision to lower
the dose, it has been confirmed.
The revelation has prompted Cr Richard Thomson to call for a
policy rethink, while Public Health South medical officer of
health Dr Marion Poore warned, over time, it was possible
more tooth decay could result.
''This means that the benefits of fluoridated water supply to
the whole community are reduced,'' she said.
The council voted in May last year to reduce the amount of
fluoride being added to the city's drinking water from 0.85mg
per litre to 0.75mg per litre. The council had previously
targeted 0.85mg per litre to ensure the dose administered
fell within ministry guidelines, which recommended a range
between 0.7mg per litre and 1mg per litre to protect against
However, council water production manager Gerard McCombie
warned councillors at the time the change to the lower target
could result in the actual dose dropping below the ministry's
guidelines. That was because of inaccuracies in the delivery
mechanism which meant the actual dose administered fluctuated
each time, he said.
A majority of councillors voted to proceed anyway, urged on
by Cr Kate Wilson, who suggested the change, and the switch
to a lower dose was made days later.
Since then, the actual dose being administered had dropped
below ministry guidelines 65 times, data released to the
Otago Daily Times following an official information
That compared with just five misses in the first half of the
year, before the change to a lower target was made.
Mr McCombie told the ODT trying to hit the lower
target, rather than fall within the range, was ''a bit like
trying to hit the bullseye with every dart''.
''Sometimes, we're a bit above it, but quite a bit of the
time we are below it,'' he said.
As a result, council staff were reviewing the entire dose
system to try to improve accuracy, although absolute accuracy
would be ''impossible to guarantee'', he said.
Cr Wilson defended the decision to lower the dose, saying
councillors wanted to set it, rather than leave it up to
They also wanted to take a ''conservative'' approach, given
public concern, including about the health of infants
consuming fluoridated water with powdered baby formula, she
She was also surprised council staff had not reported the
problem to councillors, or adjusted their sights.
''I'm not quite sure why it is so flexible. I think if you're
targeting 0.75 and you're finding you're getting a whole lot
of readings below 0.7, then you should be aiming higher.
''That's what the idea of a target is.''
However, she conceded regularly missing the target was
''something we may need to address''.
''If we're not hitting that, I'm very happy to open the
Cr Thomson - also a Southern District Health Board member -
said the decision to lower the dose had been made ''on the
hoof'', and the council now needed to rethink its approach.
He did not know if the repeated misses - sometimes for more
than a week on end - raised public health concerns, but said
that was the ''fundamental question''.
''Does it matter? And, if it does, then in my view, we need
to have another look at it.''
Fluoride was added to 85% of the city's drinking water - at
the Mt Grand and Southern water treatment plants - and had
been credited by health authorities with reducing levels of
However, opponents have mounted repeated campaigns to end
''mass medication'', citing a variety of health concerns. The
council received 34 public submissions on fluoride at its
last annual plan budget hearing, the most on a single
Dr Poore said the ministry's recommendations aimed to reduce
tooth decay for the whole community.
''Tooth decay is the most common chronic disease in our
community and causes misery ... loss of a smile, painful
infections, requirement for dental procedures, time off work
''It makes sense to add fluoride to community water supplies
in a way that the recommended levels are reached consistently
- do it properly to get the most benefit,'' she said.
However, she acknowledged there could be ''challenges''
maintaining exact levels.