The Homeland Security Department last month released what they said was nontoxic gas into New York’s Grand Central Station to trace how chemicals might flow through the terminal in a terrorist attack. We speak with biological and chemical terrorism expert Leonard Cole, who asks what this “nontoxic gas” actually was. He wrote a book about how–in the 1950s and 1960s, U.S. government scientists ran a series of tests to determine how easy it would be to expose large numbers of people to a lethal bacteria. [includes rush transcript]