Questioning and opposing the addition of fluoride to Hawke's Bay's water supply was urged of the audience at a fluoride-free meeting last night.

About 100 people packed into the Napier Conference Centre where prominent critic Dr Paul Connett spoke about water fluoridation, and the harm he argued it posed to health and the environment.

The retired professor of environmental chemistry and toxicology at St Lawrence University is on a New Zealand speaking tour as the guest of Fluoride Free NZ.

This comes as a bill is before parliament which would gives District Health Boards (DHBs) the power to make decisions about water fluoridation - rather than local authorities.

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His presentation touched on a number of arguments, including that fluoridation was a reckless medical practice, that it violated the individuals right to informed consent to medical treatment, and that "the evidence that fluoride is neurotoxic and lowers IQ in children is very strong".

He said the widespread addition of the chemical was "unethical" as the normal distribution response people had to any substance meant only some would be helped, while others could face harm.

He urged it was time to move beyond fluoridation to better alternatives, saying this was the start of a "slippery slope" to mass medication of a population.

A spokeswoman for the Hawke's Bay District Health Board said it "strongly supports community water fluoridation, as a strongly evidence based and cost effective way to prevent tooth decay in our communities".

Last night Waipukurau dentist John Jukes also spoke, telling the audience how he began to question the merits of fluoridation as an undergrad.

The local took issue with the ethics of fluoridation, that there was no control over the dosage of the chemical, and that it was treating the symptom, not the problem.

He said fluoridation failed to prevent tooth decay – arguing Hastings residents' oral health was worse than Napier residents', despite Hastings water being fluoridated.

Currently Hastings is the only district in the Hawke's Bay area with a fluoridated water supply. Central Hawke's Bay had one fluoridated water supply until 2012.

Last March Mr Jukes appeared before the Health Select Committee speaking to his submission on the Health (Fluoridation of Drinking Water) Amendment Bill.