In legal terms, there is no practical difference between putting chlorine or fluoride into public water supplies, the High Court in New Plymouth heard today.
In each case, the purpose is the improvement or maintenance of public health, senior Crown counsel Austin Powell told a judicial review into the rights of local councils to fluoridate water supplies.
It involved introducing a chemical to water that inevitably found its way into the body of someone who drank it, and in the minutest degree altered the composition of that body.
Representing the Attorney-General in what is a test case on fluoridation, Mr Powell was commenting on an earlier claim by anti-fluoridation group New Health NZ that chlorination to remove bacteria was quite different from fluoridation, which amounted to mass medical treatment violating individual rights.
Referring to numerous legal cases worldwide that dealt with fluoridation, mass medication and an individual's rights to refuse treatment, Mr Powell said while there were generally recognised rights to freedom from the state, a natural boundary was reached where the individual must engage with society.
For example, Mr Powell said he lived in Wellington where he was exposed to higher levels of carbon monoxide than he would prefer.
"But that's just one of the vicissitudes of living in an organised community," he told Justice Hansen, who will deliver a judgement on whether South Taranaki District Council has the legal right to fluoridate the water in Patea and Waverley.
Regarding human rights and the power of the state, Mr Powell drew a parallel with inoculation: if the government decided compulsory immunisation was necessary to stop the spread of disease, then everyone would have to submit to it.
Fluoridation was not such a direct interference with an individual's autonomy, since after water entered a property at the boundary it was up to the person living there whether or not to drink it.
The common finding of courts here and overseas was that for individual human rights to be violated, a minimum threshold must be crossed, the court heard.
Fluoridation was consistently found not to reach that threshold, Mr Powell said.
New Zealand's Bill of Rights Act - in just 11 words in Section 11 - enshrined rights to refuse medical experimentation and treatment, but went no further in terms of protecting bodily integrity.
The courts had since recognised Parliament was being deliberately selective when enacting the legislation. The words "medical treatment"were included, but not defined, he said.
Yesterday, barrister Lisa Hansen, acting for New Health NZ, said New Zealand has no law allowing councils to introduce fluoride. She said the practice was merely a convention established by a court case half a century ago which went to appeal and eventually to the Privy Council in London, with the Lower Hutt City Council winning, thus establishing a general and implied power to councils.
She said fluoridation was a therapeutic action, unlike adding chlorine to make water safe, and its use denied people the right to choose whether they wanted to take a medication - one that was highly unlikely to benefit them.
Today, 48 per cent of New Zealanders lived in communities with fluoridation, put into water supplies by 22 of the country's 67 local authorities. However, today's context was quite different, legally, ethically and in terms of the science, she said.
Ms Hansen referred to research that showed fluoride taken via the water supply did nothing to prevent tooth decay because the method did not provide enough of the element to make an impact.
On the other hand, gels and toothpaste containing fluoride could have a beneficial effect. They provided "topical" (local) protection, rather than the "systemic"(ingested) approach used by fluoridation.
Excessive fluoride carried risks of dental fluorosis, which could leave teeth chalky and mottled. One research outcome showed fluoridation doubled the incidence of this complication, she said.
Nobody living in a community where water was fluoridated could escape it, unless they stayed at home and produced their own food, she told the court.
Where fluoridation was used overseas, it was done so under a statute, but New Zealand did not have that.
If fluoridation was ever to be lawful, there would need to be a specific provision to permit it and no other substances, such as lithium or contraceptives.