Tag Archives: fluoidation

Reversed responsibility and the burden of proof


This tactic often comes up in discussions related to scientific and religious issues.

It’s usually used by someone who has made a claim and then been asked for evidence to support it. Their response is to demand that you show that the claim is wrong and if you can’t, to insist that this means their claim is true.

Science or Not has a brief article on this at The reversed responsibility response – switching the burden of proof. It says:

“People use this tactic to avoid supplying supporting evidence – usually because there is none. In attempting to distract you from this lack of evidence, they try to convince you that the responsibility of supplying evidence lies with you.”

This can be relatively trivial – a person might claim that there is plenty of evidence that climate change science is a scam or that community water fluoridation (CWF) is harmful. When asked for supporting evidence they ask you to “look it up” or “google it” yourself – implying that you are lazy to even ask then for their supporting evidence.

We can’t prove the impossible

Then there is the philosophically dishonest reversal of responsibility where they demand, for example, the supporter of CWF cite  studies showing CWF  does not cause harm. Dishonest because that is not how science works – it seeks to test specific situations for harm. One might produce study after study showing no specific harm but it is impossible to design a study showing anything is “safe.” The person can, therefore, dismiss each example showing no specific harm by insisting that this does not prove it is safe in all situations.

“Reversing the burden of proof is a form of the argument from ignorance fallacy, in which it is argued that a claim must be taken as true if it hasn’t been shown to be false.”

Yet, ideologically driven activists will often use this argument – maybe dressed up as the “precautionary principle.” For example, they will make submissions to community bodies conceding that perhaps they cannot produce any decisive studies showing CWF is harmful but the “precautionary principle” means that it should not be used until research shows it to be completely safe.

This is simply using ignorance – on the part of members of the community body as well as the activist – to prevent acceptance of a policy which is recommended by experts and health authorities. It’s an attempt to destroy the authority of evidence and science which should be centrally considered in such decisions.

What to do when confronted by this tactic

The Science or Not article gives advice on how to treat such tactics:

“Don’t be tempted to take on the task of falsifying the perpetrator’s claim. And don’t succumb to the pressure to accept it as true if you don’t have the evidence to refute it. Insist that they must provide supporting evidence from real-world tests.”

On the one hand, this means that community bodies who are offered submissions in this vein should demand the submitters produce the evidence and not rely on vague statements or claims. In particular, they should be wary of the use of “the precautionary principle” – unless there is enough evidence to suggest that it is applicable.

On the other hand, it means that if submitters do produce “evidence” that it must be critically and intelligently examined and not just accepted because it is full of citations. That would be submitting to the “authority” fallacy.

Finally, community bodies should be conscious of their own limitations. If they don’t have the skills for considering presented evidence properly then they should ask for the advice and opinions of real experts about that evidence.

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Onehunga and the “fluoride-free” myth

Onehunga Aquifer optimised

An aerial view of the Onehunga Water Treatment Plant

Recently I discussed the fluoridation issue with a self-diagnosed sufferer from fluoride sensitivity. He claimed to have irritable bowel syndrome (IBS) brought on by fluoride in drinking water. His doctor didn’t believe him but he knew better – every time he left his hometown (which is unfluoridated) for fluoridated areas his IBS returned. He assured me that the water in his city is “fluoride-free.”

I checked the published data for his city and found the natural levels of fluoride in the tap water is 0.4 ppm – not too much less than the recommended 0.7 ppm where community water fluoridation is used. He didn’t respond to my comment passing on this information – maybe it brought on an attack of IBS as stress is one of the known factors causing this.

This issue came up again at a recent Auckland City Council meeting which considered a request for fluoridation of the Onehunga water supply. Unlike most of Auckland Onehunga’s water is pumped from the Onehunga springs and is not fluoridated. In fact, a referendum in 2001 voted against a proposal to fluoridate.

But what struck me is the argument presented by one councillor that some resident of Onehunga moved there because the water is “fluoride-free” and it would violate their rights if the water supply is now fluoridated. That seems a very poor argument as anyone with a hangup about fluoride can buy and use a cheap water filter – far cheaper than shifting house. But the claim that Onehunga’s water is “fluoride-free” motivated me to check out the published data for fluoride in the Onehunga water.

This graph summarises the data from reports covering the years 2010 – 2014 (a single report covered 2011-2012):

So, Onehunga water is not “fluoride-free.” The average concentration is about 0.2 ppm (not too unusual for ground-water sources in New Zealand) but the actual concentrations can vary a lot. Customers would have occasionally been drinking water with a concentration as high as 0.9 or 1.1 ppm F during that time period.

Surely this would occasionally send any fluoride sensitive person into a bout of IBS, skin rash, or one of the myriads of other symptoms propagandists against community water fluoridation claim. Or perhaps only if they had been told about the high concentrations (see Fluoride sensitivity – all in the mind?).

Fluorine is the 13th most common element in the earth’s crust so it is inevitable that our food and drink contain traces derived from natural sources. In the real world, there is no such thing as “fluoride-free.”

Note: I don’t know if such variation is common with underground freshwater sources. The Onehunga aquifer  derives from rainwater soaking through lava flows around One Tree Hill. It could well be prone influences from historical industrial or other sources in the locality. Apparently it has high nitrogen levels and may also be influenced by broken sewer pipes.


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