QUESTION 1: What’s the story about the Mexican study which linked mother’s prenatal urinary level to the decrease in their child’s IQ?
This study got a lot of local media coverage because anti-fluoride activists used it to argue against fluoridation in New Zealand.
Published last year, the study reported a decline in child IQ as their mother’s prenatal urinary fluoride levels increased. Anti-fluoride activists like Paul Connett (who visited New Zealand last month on a speaking tour) declared it would mean the end of fluoridation worldwide. He claimed the effect of maternal prenatal urinary F on child IQ was large and the relationship highly significant.
Although the reported relationship between prenatal fluoride levels and children’s IQ was statistically significant it explained only 3% of the IQ variation, meaning that if a factor which really influenced child IQ had been included in the study the association with prenatal urinary F would probably not have appeared.
The high degree of scattering of data points in the study (see slide below) illustrates the problem. When this scatter is taken into account the predicted decrease in child IQ turns out not to be statistically significant. Paul Connett’s claimed decrease of child IQ by 5-6 points for an increase of 1 mg/L in mother’s prenatal urinary F is actually 5-6 ± 26 IQ points which is, statistically, not different to zero IQ points.
I described Paul Connett’s misrepresentation of the prenatal maternal fluoride study in my blog article last month “Paul Connett’s misrepresentation of maternal F exposure study debunked and in an opinion piece on Health Central
Mary Byrne, the coordinator of the local anti-fluoride activist group, Fluoride Free NZ, criticised these articles in a response published on Health Central (see “Opinion: Mary Byrne – Fluoridation promoter wrong to discredit landmark study”) and on my blog as a right of reply (”Anti-fluoride group coordinator responds to my article”). My response to her criticism has also been published on my blog (see “Mary Byrne’s criticism is misplaced and avoids the real issues”). I recommend these articles to any reader wishing to dig deeper.
QUESTION TWO: What’s happening with the fluoridation bill currently before parliament?
The Health (Fluoridation of Drinking Water) Amendment Bill had its first reading in December 2016. A large number of written and oral submissions were made on the bill and officials have drafted suggestions for its amendment. This will happen during the second reading which is now due (it is currently 14th on the Parliament Order Paper.)
The bill transfers decisions on fluoridation away from local councils to District Health Boards. It arose because councils had become frustrated by activist pressures on them and the fact they had no expertise to adjudicate on the science when reacting to this pressure.
Anti-fluoride groups and activists have now been intensely pressuring MPs to reject the bill.
But a meeting at parliament organised by activists in February for visiting US anti-personality Paul Connett had an audience of only three MPs. A strong indication this pressure has been counterproductive. While changes will be made in the second reading the bill’s rejection is highly unlikely.
Based on the submissions and the subsequent reports from officials I expect the bill will be changed to clarify who pays for fluoridation, the remaining role of councils and mechanisms for community consultation.
Dr Ken Perrott is the Science Advisor for Making Sense of Fluoride, Inc., an Australasian group of academics, scientists health specialists and students which works to counter misrepresentation about community water fluoridation.
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