A gentleman describing himself on Twitter as a celebrity dentist called Dr Gerry Curatola put out this alarming tweet on the 9th of December 2013. “There is enough #flouride in a standard tube of toothpaste that, if ingested, can be fatal to two small children.” This being twitter I have no idea if this really was tweeted by Dr Curatola. I am not even aware that there were any celebrity dentists, let alone exactly where Dr Curatola stands in the pantheon of tooth titans. I’ll leave the management of his reputation to him, and concentrate on the facts.
Anyway I saw the old tweet getting retweets in my timeline, so I thought I’d investigate.
So can eating toothpaste kill a child?
Fluoride, to give it its correct spelling, is like most things. It certainly can be dangerous, but it is the dose that makes the poison. And fortunately we are in a good position to judge exactly what dose is poisonous. The toxicological term for the minimum amount of a substance that is harmful is the TDLo, the lowest toxic dose. This isn’t the amount that is enough to actually kill someone, just the lowest dose at which harmful effects can be detected. This usually has to be inferred from animal studies because there are moral issues involved with doing this kind of experiment on humans. But as it happens we do have data on humans for flouride, so this data is more reliable than usual.
The actual figure is 3mg per Kg per day. So if we assume a toddler weighs 12.5Kg and we are talking about killing two of them we will need 2 x 3 x 12.5 mg of fluoride or 75mg. This isn’t, I must point out, a lethal dose. It is the daily dose that has been shown to have an adverse health effect. Eating that much fluoride in one go is not a good idea, and I would not suggest that anybody do it, but it is unlikely to kill either of our small children outright. It is probably not going to do them any harm at all unless it turns into a habit.
So how much toothpaste would you need to eat to get that amount of fluoride? EU regulations restrict it to 0.15% or less, and 0.1% is a typical level. Taking the higher value, this means that you would need 50ml of toothpaste to deliver the required 75mg. A large tube of toothpaste is about 100ml.
So the idea that eating a whole tube of toothpaste is enough to kill two children is not really realistic. There is just about enough fluoride in toothpaste that you could just about get to a harmful level if you made it a daily item on your toddlers diet, but you are a long way short of a lethal dose. The lowest dose that has ever killed anyone outright is 4000mg, for an adult in Canada. That is well over 20 tubes of fluoride containing toothpaste. Most people would probably survive a higher dose. Small children would be a risk at lower levels because of their smaller size, but should still survive eating a single tube.
So the conclusion is that there really is nothing to worry about if you find that a child has tucked into the kind of quantities of toothpaste they might reasonably be expected to encounter. It isn’t something to be encouraged, but it is nothing to panic about either.
IARC Monogr Eval Carcinog Risk Chem Hum. 1982 Apr;27:237-303. Inorganic fluorides used in drinking-water and dental preparations
Can Med Assoc J. Apr 1945; 52(4): 345–349. PMCID: PMC1581810 Acute Fluoride Poisoning I. M. Rabinowitch