A recently published US study finding that women who drink fluoridated water have lower IQ babies is being panned by a Bay of Plenty Medical Officer of Health Dr Neil de Wet, while being promoted by fluoride opponents.

Fluoride Free New Zealand says the results mean the 23 New Zealand councils that still fluoridate drinking water should stop using it immediately in order to protect the brains of the unborn.

Dr Neil de Wet says the study referred to is poor quality, has limited scientific value and is largely irrelevant to understanding issues regarding safety and effectiveness of water fluoridation.

'The safety of water fluoridation has been rigorously assessed many times over the last 60 years. There is a very strong scientific consensus and body of evidence that water fluoridation is safe and effective,” says Neil.

'It is very unlikely that the Bashash paper will withstand scientific scrutiny or make any meaningful contribution to this scientific understanding of the safety of water fluoridation.”

The study published on Tuesday in the US Government's Environmental Health Perspectives finds that children born to mothers exposed to fluoride while pregnant, have significantly lower IQ scores.

This is particularly relevant to New Zealand where half of the population is currently subjected to fluoridation, says Fluoride Free New Zealand National Coordinator and Media Spokesperson, Mary Byrne.

Slamming Neil de Wet's comment that the study is 'poor quality”, Mary says the study was published in Environmental Health Perspectives, a monthly peer-reviewed journal of research and news published with support from the National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health, U.S. Department of Health and Human Services.

The study was conducted by a team of scientists from University of Toronto, University of Michigan, McGill University, Indiana University, Mount Sinai School of Medicine and Harvard School of Public Health, by a group of researchers who have produced over 50 papers on the cognitive health of children in relationship to environmental exposures.

It was funded by the US Government's National Institute of Health and was a multi-million dollar study. This was the group's first study of fluoride - their other studies mostly dealing with lead, mercury and other environmental neurotoxins.

This study offers confirmation of previous studies in Mexico, China and elsewhere, says Mary. Some of those studies had higher fluoride exposures than are commonly found in fluoridating countries, but many did not.

The sole study in a country with artificial water fluoridation is by Dunedin dentist Jonathan Broadbent. 'That study found no association between water fluoridation and IQ and was trumpeted by fluoridation defenders,” says Mary. 'But that study was shown to have almost no difference in total fluoride intake between the children with fluoridated water and those with non-fluoridated water, since at least half of the children in the non-fluoridated area were given fluoride supplements.

'This left only a small proportion of the study children without substantial fluoride exposure. Nor did this study look at maternal fluoride exposure during pregnancy, which could be the most vulnerable time of exposure.”

Neil also recommends the Broadbent study as a ‘recent high quality study by the University of Otago' which has provided strong evidence that water fluoridation in New Zealand does not have an adverse effect on IQ. (Broadbent, et al 2015 www.ncbi.nlm.nih.gov/pubmed/24832151)

The Ministry of Health recommended 1ppm until the 1990s when it reduced to a range from 0.7ppm to 1ppm, with a target of 1ppm. The US Human and Health Services have directed a maximum of 0.7ppm for fluoridation.

The paper also reports that in the USA, which is 70 per cent fluoridated, urine fluoride ranges from about 0.5 to 1.5 mg/L which fully overlaps the range found in the Mexican study.

'The child of a mother who was drinking water with 0.85ppm fluoride would be predicted to have 5 IQ lower IQ points than if the mother had drunk water with close to zero fluoride in it. This obviously has huge consequences for New Zealand children,” says Mary.

'Pregnant women in New Zealand in fluoridated areas likely have similar levels of urine fluoride as those in the Mexican study. Urine fluoride reflects total fluoride intake from all sources, not just fluoridated water.

'The study authors are cautious in their conclusions, as is common for scientists. But the implications of this study are enormous. There have been 58 other human studies looking at fluoride exposure and harm to the brain - 51 of them have found an association.”