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THEY were locked away in an old ammunition bunker near St Louis, in dozens of cardboard boxes. Each was in its own manilla envelope, with an index card identifying the donor. These 85,000 baby teeth were collected in the late 1950s and early 1960s from children in the St Louis area to study the effects of radioactive fallout in the environment. The fallout came from hundreds of above-ground nuclear tests in America and other parts of the world. The radioactive isotope Strontium-90, one of the by-products of the bombs, spread into the atmosphere, fell onto the land, was ingested by dairy cows and passed into the milk supply. Strontium-90, like calcium, was concentrated in childrens teeth in detectable amounts. In 1958 scientists in St Louis began a campagin to collect baby teeth to study the link between above-ground testing and human exposure. The undisputed link between the tests and a radioactive element in baby teeth provided much of the impetus for the 1963 Test Ban Treaty, which outlawed above-ground nuclear weapons-testing. The rediscovery of the 85,000 samples, about a quarter of the total collected, has spurred a new effort to study the link between early childhood exposure and health problems in later life. There is already some evidence that 1950s children in St Louis grew into adults with a higher-than-average rate of cancer. Now researchers at the Radiation and Public Health Project, based in Brooklyn, are attempting to find more than 6,000 of the teeth donors to track their health problems or, in some cases, their premature deaths. | 
