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.

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 "bomb pulse" of radioactive carbon generated by nuclear tests in the ...