In the early 1950's, the army set up motorized blowers on top of residential high-rises in low-income, mostly black St. Louis neighborhoods, including areas where as much as 70% of the residents were children under 12. The government told residents that it was experimenting with a smokescreen to protect the city from Russian attacks, but it was actually pumping the air full of hundreds of pounds of finely powdered zinc cadmium sulfide. The government admits that there was a second ingredient in the chemical powder, but whether or not that ingredient was radioactive remains classified. Of course it does.