I believe the science. Also personal experience. I watched my grandfater die a painful death from lung cancer. I know smokers who can run a marathon and I know smokers who can't run at all. A family friend died at 55 from lung cancer. It's not hype.
IF I HAD A MINE SHAFT, I don't think I would just abandon it. There's got to be a better way. -- Jack Handley, The New Mexican, 1988.