The citizens of London learned a hard lesson about the effects of air pollution on December 5, 1952. As people shoveled coal into their stoves, they had no idea that a tragedy would occur shortly. Vast amounts of smoke exited the chimneys, which in combination with light winds and moist air created a thick, toxic smog. The phenomena caused several thousands of deaths from pneumonia, bronchitis, tuberculosis or heart failure during the following week. Learn more information in this three part documentary.