Jul 27 2012
A news article in the Sacramento Bee declares: “Harvard Study Finds Fluoride Lowers IQ – Published in Federal Gov’t Journal.” Except – this is not a news item, and it’s not really a study. The article is about a recently published systematic review and meta-analysis – not new data. The term “study” is vague, and I find it often causes confusion.
Far worse than this common imprecision is the fact that this article, under the “News” tab on the Bee website, is not actually a news report. It is a propaganda article written by the NYS Coalition Opposed to Fluoridation, Inc. and distributed as a press release. The Bee does post a disclaimer at the top of the page, reading:
This section contains unedited press releases distributed by PR Newswire. These releases reflect the views of the issuing entity and are not reviewed or edited by the Sacramento Bee staff. More information on PR Newswire can be found on their web site.
That’s better than nothing, but I wonder how many people reading the press release will notice and read the disclaimer. In my opinion, a news outlet should not reprint press releases sent out from advocacy organizations clearly intended to promote an agenda. They especially should not print them under the banner of “News.” The disclaimer is not adequate.
The review itself is being spread around the internet and multiple readers sent me links to the article or reporting about it. Not surprisingly, the press release from an anti-fluoride organization did not put the review into proper scientific context. The review concludes:
“The results support the possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment. Future research should include detailed individual-level information on prenatal exposure, neurobehavioral performance, and covariates for adjustment.”
“The possibility” of an effect justifying future research is not the same as concluding that there is an effect. But the problems with the way this review is being presented go far deeper. The implication being implied by anti-fluoride groups is that the fluoridation program is the US and elsewhere is putting children’s IQs at risk. This data, however, cannot be used to support that conclusion.
First it should be noted that almost all of the studies reviewed were conducted in China (one was conducted in Iran) – not in the US. China had a limited fluoridation program for a time, and has had no fluoridation of drinking water since 2002. So why, then, are most of the studies from China?
There are many rural areas of China that have naturally high levels of fluoride in the well water. The studies were largely looking at this exposure. Two studies looked at fluoride exposure from inhaling smoke from coal burning. So the question is – how do these levels of exposure relate to the amount of fluoride being added to water in the US (because toxicity is always all about dose)? There was a lot of variability across the studies, but generally the high fluoride groups were in the 2-10 mg/L range, while the reference low fluoride groups were in the 0.5-1.0 mg/L range (not including the coal burning studies, which had much higher fluoride levels).
The recommended fluoride level for fluoridated drinking water is 0.5-1.0 mg/L (similar in most countries – Australia, for example, uses 0.6-1.1 mg/L). The EPA set the upper safe limit at 4.0, with a secondary (voluntary) recommendation of 2.0. Areas with high natural fluoride actually have some of the fluoride removed from the drinking water.
In other words – fluoridated water in the US has the same level of fluoride as the control or low fluoride groups in the China studies reviewed in the recent article, and the negative association with IQ was only found where fluoride levels were much higher – generally above EPA limits.
There are many weaknesses to the epidemiological studies reviewed in the recent article – high heterogeneity, poor controlling for other variables, no indication of blinding of IQ assessments, and many others. But even taken at face value they do not indicate any association of between lower IQ and the fluoride levels added to drinking water in the US. In fact, those levels of fluoride were used as the controls in these studies showing higher IQ. (There was a lot of variance of the effect size, but the net effect size on IQ in the meta-analysis was -0.45 IQ points).
This fact has not stopped anti-fluoridation groups from exploiting the review for their own propaganda purposes. Otherwise respectable news outlets are unwittingly collaborating in this anti-scientific propaganda campaign by lazily reprinting these press releases in their news sections – without any editorial filter.
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