In the 1950s, when half of American adults smoked, many freshmen unpacking at college were greeted by upperclassmen paid by tobacco companies to distribute free cigarettes. In 1964, the U.S. surgeon general said smoking causes lung cancer. Most people, however, had long intuited that inhaling smoke from a burning plant is unhealthy. In a 1906 O. Henry short story, a character asks, “Say, sport, have you got a coffin nail on you?”

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