An idle facebook discussion, wherein I discuss eating thousands of liters of toothpaste.

A Facebook friend posted a meme discussing the dangers of fluoride toothpaste, so I did a little math:

“It takes 5-10 grams of sodium fluoride to kill a full grown human. Fluoride drinking water contains less than a single part per million. (about 0.5 ppm, usually.) The average person consumes a bit more than a swimming pool worth of water in their lifetime. (Around 87,000 liters). The amount of fluoridated water that would be required to reach 5 grams of sodium fluoride? 10 million liters. Humans are literally incapable of drinking enough fluoridated water to kill themselves, or even enough to cause tooth color mottling, the first effect of fluoride buildup to appear. (Other fluoride salts than sodium fluoride can be used, but similar math applies.)
 
What about toothpaste, though? Well, sodium fluoride in toothpaste (or in fluoridated water) reacts with apatite (the mineral your teeth are made of- I’m fairly sure the pun was intended) to to form fluorapatite, which occurs naturally in enamel. (There’s a lot of fluoride on Earth- as the lowest atomic weight halogen, there’s a ton of it around.) The levels of fluoride in toothpaste are pretty carefully calculated so that most of it is used in the reaction that forms fluorapatite, and the rest gets spat out. In order to actually get fluoride poisoning from toothpaste, which has around 1,000 ppm of fluoride, you’d have to eat several thousand liters of toothpaste. Again, rather impractical. You’ll never put enough toothpaste in your mouth to cause even the most minor of symptoms, even if you retained 100% of the fluoride (which your body slowly flushes out over time) and none of it reacts with the apatite in your teeth.
 
Fluoride poisoning does occur, but not from toothpaste or fluoridated drinking water. More often, it’s from industrial waste or wells built in regions with certain types of high-fluoride granite.”
Moral of the story? Don’t eat thousands of liters of toothpaste.
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3 comments

  1. You are extremely stupid. 0.5 ppm is unusually low for artificially fluoridated water. The nominal concentration is usually at least 0.7 ppm. You haven’t distinguished between fluoride and sodium fluoride, and the 5 to 10 g range is high even for fluoride, let alone sodium fluoride. The fact that fluoride is a cumulative poison has also not been taken into account. To top it all off, you can’t even get the simple arithmetic right. 0.5 ppm is equivalent to 0.5 mg/L. So in 10 million litres of water with a fluoride concentration of 0.5 ppm there is 5 million milligrams of fluoride, which is the same as 5 thousand grams, or 5 kilograms. The idea that 10 million litres of fluoridated water is required to reach 5 grams of sodium fluoride is laughable. You’re out by three orders of magnitude. Since you are innumerate, have no knowledge of toxicology, and are scientifically illiterate, it’s probably a good idea to stay away from this kind of discussion, genius.

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    1. Aww, I got my first ever angry commenter on this blog! Well, I just pulled most of my data off of wikipedia, did some math off the top of my head, and posted it on facebook. Not to mention I study geology, and most of my chemistry is oriented towards that, rather than biochemistry. Errors are not improbable.

      Thankfully, though, I’m a reasonable human being who doesn’t usually run around on the internet insulting random people. That fact really helps me sleep at night. You, on the other hand, are intensely rude even when you’re NOT anonymous on the internet. Not to say I’m innocent of that, but I really don’t think you’re likely a pleasant person in real life. You seem dedicated towards shutting down conversation, rather than engaging in it.

      Also, just because I’m not a saint, and enjoy occasional pettiness, your blog is ugly and your rhetoric is overblown.

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  2. Call the poison control center at 412-390-3381 if you swallow toothpaste. I’m sure it’s for liability reasons; it just can’t be because humans are that stupi…. Uhh, never mind.

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