The short answer is yes, it is, but it’s easy to understand why some people think it isn’t.
When we look at chemical toxicity, we need to understand that there are several different classes.
Firstly, there are chemicals for which any level of exposure is undesirable, as with sufficient exposure over time they will have an effect on our health, possibly with lethal outcomes. In this category we have asbestos, lead, and any of the tars and other combustion products in cigarettes.
There are other chemicals, however, which although toxic in higher concentrations, are either completely harmless, or even beneficial at low levels. In this category we have most transition metals such as copper, zinc and iron.
But the trouble is that this is not obvious if you look at the data, and fluoride is a case in point. If you look at the MSDS for sodium fluoride you find that it is an S7 poison – the highest category. Little wonder that some people are leery about having it in their water.
So what does fluoride do in your body?
Mostly, it reacts with your bones. In this regard it is unusual, as most other toxins attack your organs somehow. But the fluoride attacks your bones. This is why in Breaking Bad it is the chemical of choice for disposing of bodies…..
So if you are exposed to enough of it to be harmful it causes horrible internal burns which are very difficult to treat. Whenever I have had to handle hydrofluoric acid (it’s used to make industrial strength brick cleaner) I’ve gone the full monty in terms of protective gear.
But in water it’s nowhere near this strength. The fluoridating agent in municipal waters is fluorosilicic acid, a by-product of aluminium production, and it gives a level of fluoridation of about 2mg/L.
At this concentration it is too low to be harmful – no matter how much water you drink – but it still reacts with your teeth. I don’t think anyone quite understands the mechanism, but it would be some sort of inorganic composite where the fluoride combines with the calcium phosphate (that your teeth are made of) to produce some sort of calcium fluorophosphate, that is in some way chemically resistant to the chemical decay process (caused by lactic acid that is made by anaerobic bacteria).
And this has certainly been confirmed by every study in this area – so you may drink municipal water – and use toothpaste, with absolute confidence that your teeth are being protected.