And since you neglected to bother with anything else I posted, I can only surmise that you can't.
Please explain that to my paternal Grandfather. He's dead. Died from lung cancer brought-on by smoking tobacco (onset was 5 years after he'd quit in 1972). Ripe old age of 55, he was. Family history of cancer? Nope. Did he commit suicide, or was he poisoned? You make the call...
Philip Morris execs publicly insisting that there were no health hazards involved in smoking tobacco up until the late '70's. (As of 1961, they already had strong scientific evidence that tar was a carcinogen). Tobacco was even readily available to children in retail outlets at that point in time.
No different than if they'd served him a strychnine-tainted cocktail, and assured him it was safe. It wasn't 100% sure to kill him, but it did.