In some areas there is too much of fluoride naturally and it must be removed, not added.

Geographical areas associated with groundwater having over 1.5 mg/L of naturally occurring fluoride, which is above recommended levels https://en.wikipedia.org/wiki/Water_fluoridation#/media/File...

Water in the UK is also supplemented with flouride. I think the point is that toothpaste contains more.

Only about 10% of it, according to Wikipedia. https://en.wikipedia.org/wiki/Fluoridation_by_country (75% of those with community water systems in the U.S., for reference.)

10% of water in UK, not 10% of toothpaste.

Sure. Of course toothpaste has flouride. There's nowhere that's untrue, I assume. But the person I responded to made a claim about water flouridation in the UK which was mostly false.

There are actually fluoride-free "natural" toothpastes that have unfortunately been growing more common. As one might expect, they are of dubious effectiveness.

In the United States, recommended fluoride levels in drinking water are 0.7ppm, whereas toothpaste is 1000ppm - 1500ppm.

So even with fluoridated water you want to avoid rinsing.

Do you have more information on this? I thought that fluoride was toxic and thus shouldn't be swallowed. Are the quantities too small to harm you yet sufficient to prevent the formation of caries?

Water fluoridation rates are well under dangerous levels - about 0.7 mg/L for artificially fluoridated water, vs 2+ mg/L long-term to actually cause any problems. Even that small amount helps with reducing tooth decay, as was shown in the US in studies starting in the 50s comparing areas with naturally fluoridated water with areas without it.

It's significant enough to prevent some tooth decay, but insignificant when it comes to toxicity.

It is a small amount. It helps, but is not enough to completely prevent cavities. You still need to brush your teeth like normal.

Fluoridation is by no means universal in the US—around 69.2% of public water in 2006, according to Wikipedia[1]. In some areas, resistance is strong and cuts across diverse political orientations. Portland's 2012 attempt to fluoridate, for example, drew opposition on the basis of libertarianism, environmentalism and science skepticism.

[1] https://en.wikipedia.org/wiki/Water_fluoridation_in_the_Unit...

Unless of course you drink filtered water.

Carbon filters are fine.