Nuclear Fallout and Forensics

Apparently the nuclear tests conducted from 1955 to 1963 have left a lot of carbon-14 in the atmosphere. Levels of this carbon-14 rapidly equalized around the globe and have been decaying at a steady rate ever since. What's interesting is that these levels are then deposited into teeth when they form around age 12. This means that by finding the amount of carbon-14 in teeth, forensic scientists can determine the age of an individual.

Legacy of Nuclear Tests May Provide New Forensic Tool

The above-ground nuclear tests that occurred between 1955 and 1963 dramatically increased the amount of the isotope carbon-14 in the atmosphere. The levels rapidly equalized around the globe, even though the explosions occurred at only a few locations, and entered plants in the food chain through photosynthesis. By eating plants, and animals that feed on plants, human absorb carbon-14 and exhibit levels of the benign, traceable isotope that are similar to atmospheric concentrations. What is more, carbon-14 decays with a half-life of 5,730 years, a phenomenon that scientists can exploit as a way to determine the ages of objects that contain the isotope. For the new study, Jonas Frisén of the Medical Nobel Institute in Stockholm, Sweden, and his colleagues analyzed the carbon content of tooth enamel. Because teeth do not exhibit any turnover during a person's life, the scientists can determine when a tooth formed by comparing its carbon-14 content to past atmospheric levels. In addition, adult teeth form during a distinct period of childhood development around age 12, so this information can be translated into the age of an individual.