Tobacco has been the cause of death of millions of people from when it was first introduced. They didn't know it at first, but even after exclusive scientific studies linking cigarettes and cancer appeared in the 1920s and subsequent studies which showed cancer could be induced by using nicotine-free tobacco, which means that tar, with or without nicotine, was carcinogenic became overwhelming in the 1950s, they still denied it. They still held that there was no direct evidence linking tobacco and it's supposed harmful effects. Tobacco companies funded think tanks and lobbying groups, started health reassurance campaigns, ran advertisements in medical journals, and researched alternate explanations for lung cancer, such as pollution, asbestos and even pet birds. Denying the case against tobacco was "closed," they called for more research as a tactic to delay the inevitable regulation.
