When a young child loses a baby tooth, tradition instructs that we place the tooth under the child’s pillow. That night, so the story goes, the Tooth Fairy comes, takes the teeth (and per some, turns it into a star) and leaves a coin (or more) where the tooth once was.

The Tooth Fairy is fiction, but in the late 1950s, there was a lady who wanted baby teeth. Her name was Louise Reiss.

Reiss, a medical doctor, believed that nuclear weapons testing in the United States was harmful to those in nearby areas. Specifically, the nuclear tests produced strontium-90, a carcinogenic radioactive isotope, and Reiss and others believed that people near the blasts were absorbing strontium-90 and other things. Because strontium-90 is similar, chemically, to calcium; and because our bones absorb calcium, there was a good chance that our bones were also absorbing radioactive fallout.

To test, Reiss came up with an outside-the-box idea to use of the most available bone out there — baby teeth — to measure the effect of nuclear fallout on our bodies. Children were losing these teeth anyway — why not donate them to science?

Working with the Washington University Dental School and Saint Louis University, Reiss and others set out on what would later be called the “Baby Tooth Survey.” Over the course of a dozen years ending in 1970, the group collected nearly 300,000 baby teeth from St. Louis area children. (The children were given the button pictured above in exchange; whether the Tooth Fairy also visited is unknown, and the Tooth Fairy was unavailable for comment.) The results weren’t promising. A November 1961 report noted that strontium-90 levels in children’s teeth were increasing as the years went on, suggesting that radioactive materials from nuclear fallout was, in fact, being absorbed into the bodies of those exposed. A subsequent study showed that children born after 1963 had fifty times more strontium-90 than those born before nuclear testing began.

In 1963, with the knowledge of the first Baby Tooth Survey study now available, the United States agreed to and ratified the Partial Nuclear Test Ban Treaty; nations which are signatories to the treaty agree to not perform nuclear weapons tests above-ground. For Americans, this is probably a very good thing. A 2001 study using a subset of the teeth collected by Reiss and matching them with their owners concluded that those who died of cancer before age 50 had a higher level of strontium-90 in their teeth than those who survived past 50.

Bonus fact : There are three countries which are known to have tested nuclear weapons yet have not signed the Partial Nuclear Test Ban Treaty: China, North Korea, and perhaps surprisingly, France. France did not sign the treaty because, according to the Arms Control Association, the agreement did not go far enough — it didn’t include an “end to weapons production, reconversion of stocks, and a ban on possession and use.” Nevertheless, France has not tested a nuclear weapon above ground since 1974, when they did so on the French Polynesian atoll of Moruroa.

From the Archives: Tooth Be Told: After getting over a cold, should you change your toothbrush?

Related: “High-Yield Skepticism: The Creative Process and Problem Solving” by Louise Reiss. Also — but supplies are limited! — $39.95 (plus shipping) will net you some uranium ore of your very own.