Nuclear Tests Leave Mark in Teeth, Reveal Age

Aboveground testing of nuclear bombs during the 1950s and 1960s produced large amounts of radioactive carbon that diffused around the globe. One of the places this radioactive element ended up is in our teeth, a new study reports. ... In their study, the researchers were able to determine the ages of 22 individuals to within 1.6 years by comparing the amount of C14 in their teeth to the known concentrations of C14 in the atmosphere.

... Beginning in 1955, the global concentration of C14 in the atmosphere spiked due to increased nuclear bomb testing taking place in various countries worldwide, including the United States. C14 acts just like regular carbon and can react with oxygen to form carbon dioxide. Plants incorporate the radioactive carbon dioxide by photosynthesis. By eating plants and the animals that feed on plants, the C14 concentration in the human body closely parallels that in the atmosphere at any given time.

One place in the human body where carbon is incorporated is in the teeth, where it makes up approximately 0.4 percent of the hard outer covering of the tooth known as the enamel. During childhood, the enamel forms at different times depending on the tooth and is laid down only once. The final formation of enamel occurs at age 12 in a child?s wisdom teeth. This means that the C14 concentration found in the enamel of the tooth reflects the amount of C14 that was in the atmosphere when the enamel formed.

Between 1955 and 1963, approximately 160 nuclear bombs were detonated aboveground in the United States. With the signing of the Limited Test Ban Treaty in 1963, nuclear testing in the United States, Great Britain and Russia moved underground and atmospheric concentration of C14 have since been dropping exponentially due to radioactive decay and atmospheric diffusion. - livesci

Nuclear bombs have another interesting connection to teeth. Check this out.