THE fallout from cold war nuclear tests may prove the undoing of drug barons. Forensic scientists are using the rate at which the leftover radioactivity is taken up by living things to pinpoint precisely when plant-derived drugs were grown.
Impurities such as pollen in a drug batch can be used to work out where a shipment was cultivated, but knowing when the drugs were grown is also extremely useful evidence.
For instance, when the Taliban banned opium production in Afghanistan in 2000, the UN wondered how effective the ban was. They wanted to know if pre-2000 stockpiles were being sold, but had no way of dating seized hoards. They do now.
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A team led by Ugo Zoppi at the Australian Nuclear Science and Technology Organisation in New South Wales has found a way to date drug samples using the 鈥渂omb pulse鈥� of radioactive carbon generated by nuclear tests in the 1950s and early 1960s. When the 1964 Comprehensive Test Ban Treaty came into effect, the level of carbon-14 in atmospheric CO2 was twice the level it had been before nuclear testing began. Since then it has steadily declined as the isotope has been taken up by the oceans and living things.
Opium and marijuana, like all organic matter, have the same ratio of radioactive carbon-14 to carbon-12 that was in atmospheric CO2 when the plants were growing. So researchers can simply use the ratio to read off the age of a plant-derived drug. Traditional carbon dating, which measures the rate at which carbon-14 decays after an organism鈥檚 death, is too inaccurate, with an uncertainty of tens to hundreds of years.
Zoppi鈥檚 team has tested the technique with nine cocaine and opium samples of known ages. He says the technique was able to pinpoint the exact year each of them was grown.