June 2002: Scientists Determine Anthrax Used in Attacks Is Two Years Old or Less

Scientists working with the FBI’s anthrax attacks investigation determine that the anthrax used in the attacks was relatively new. A series of nuclear weapons tests in the US in the 1950s left traces of carbon-14. Every year, the quantity of carbon-14 diminishes at a predictable rate. So, by “calculating the ratio of carbon-14 to the normal kind in residue of plants eaten by the cow from which the [anthrax] was made,” investigators learn that the anthrax had been grown within the last two years. The anthrax is no more than two years older than when it was sent, which would mean the anthrax cannot be older than roughly September 1999. [New York Times, 6/23/2002; New York Times, 8/5/2008]