Emeritus Prof Paul Connett, an environmental chemist, of St Lawrence University, New York, outlined the “case against fluoride” at a public meeting attended by about 60 people.
He is director of the International Fluoride Action Network, and lead author of The Case Against Fluoride.
Prof Connett said several studies, including some in New Zealand, had shown only relatively minor dental-health benefits arising from fluoridating a water supply.
However, several recent studies suggested fluoride was implicated in reducing IQ levels among young people, and other studies raised concerns about potentially adverse effects on brain and bone health.
New Zealand was one of only eight countries in the developed world where more than 50% of the public water supply was fluoridated.
Some public health authorities, including in New Zealand, appeared to be concerned they would be “losing credibility” for their other public health programmes if they began rethinking their attitude to fluoridation, he said.
• In comments on the New Zealand Ministry of Health internet site, ministry officials said tooth decay caused pain and loss of self-esteem, and about $500 million a year was spent in treating it in New Zealand each year.
Fluoridation and a healthy diet were the most cost-effective ways to prevent dental decay.
Health officials said fluoride, at the low levels found in the New Zealand water supply, was not toxic.
An “independent” review of Prof Connett’s views on fluoridation had been undertaken, and they saw no evidence requiring any change to the water fluoridation policy.