Scientists develop tooth enamel dating technique for disaster victim identification

From last year's Indian Ocean tsunami to the recent Hurricane Katrina, victims of large-scale disasters could be identified thanks to a new technique by which their real age at the time of death can be determined, scientists reported on Wednesday.

The new technique, developed by researchers at US Lawrence Livermore National Laboratory and the Karolinska Institute in Sweden, determines the amount of carbon-14 in tooth enamel.

Scientists can relate the extensive atmospheric record for carbon-14 to when the tooth was formed and calculate the age of the tooth and its owner, to an accuracy of within about 1.6 years.

Previous techniques, such as evaluating skeletal remains and tooth wear, are accurate only to within five to 10 years in adults.

Because enamel doesn't turn over, the carbon isotope laid down in it during tooth formation stays there, making tooth enamel a very good chronometer of the time of formation, scientists explain in this week's issue of the journal Nature.

The Swedish researchers already used enamel dating to help identify victims of last December's tsunami in Southeast Asia. Livermore researchers also provided information on this technique to US federal agencies as part of the laboratory's assistance in Hurricane Katrina relief work.

It is very hard to identify someone using only this technique, but forensic scientists can narrow down the number of people from a list of missing people, the researchers said.

Carbon-14, or radiocarbon, is naturally produced by cosmic ray interactions with air and is present at low levels in the atmosphere and food. Because humans eat plants, and animals that live off plants, the carbon-14 concentration in bodies closely parallels that in the atmosphere at any one time, the researchers explained.

They said that the technique for carbon-14 analysis using accelerator mass spectrometry is becoming increasingly sensitive and inexpensive.

Source: Xinhua

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