The Cold War yielded a lot of horror stories. One of them was in St. Louis, where low-income housing and schools were routinely gassed in order to practice attacks on Russian cities. Also, there may have been radiation in the gas. Just to make it perfect.
Did you know that St Louis resembles cities in Russia? Until 1994, neither did the residents of St Louis. They were made aware of it when some documents from the 1950s and 1960s were declassified, and a St Louis professor named Lisa Martino-Taylor took a look through them. She discovered that the US considered attacking Russia with biological weapons. To test the dispersal of those weapons, they found a US city that resembled those cities in the USSR, and gassed it.
Blowers were set up on the tops of low-income housing and schools, and, occasionally blew a fine powder over the nearby communities. The powder was zinc cadmium sulfide, officially. Martino-Taylor thinks that there were radioactive particles mixed in.
The military claims that the exposure to zinc cadmium sulfide, a fluorescent powder, posed no health risk to the people below, and that no radioactive particles were ever dispersed over St Louis. They don't, however, dispute that they gassed (or powdered) unconsenting citizens – or that they chose the poorest neighborhoods to perform chemical testing in. Or that the tests went on for over a decade.