At 11:05 on a February night in 1953, a worker employed by the U.S. Army opened a valve on a motorized blower and for five minutes dispersed a mysterious fluffy powder into downtown St. Louis. So began military-sponsored tests in St. Louis that remained secret for four decades and, to this day, raise questions about what the government was up to in the Cold War operation. St. Louis was among several cities where the aerosol testing took place in the 1950s and 1960s with zinc cadmium sulfide, a chemical powder mixed with fluorescent particles so that dispersal patterns could be traced. In 1953 alone, the military conducted 16 tests involving 35 separate releases of zinc cadmium sulfide in St. Louis, many in an area described at the time as a densely populated slum district." The Army conceded later that the tests were part of a biological weapons program and that St. Louis was chosen because it roughly matched the population and terrain of Russian cities that the United States might attack. Relying heavily on documents obtained under the Freedom of Information Act, [Prof. Lisa] Martino-Taylor identifies connections between participants in the St. Louis testing and scientists who took part in wartime efforts to build the atomic bomb. Noting postwar efforts to test radioactive materials on Americans, she raises suspicions that the St. Louis testing involved not just materials called harmless by the Army but possibly radioactive isotopes. Martino-Taylor found in her research that the aerosol particles were milled so as to be easily absorbed into lungs.