[bootload]

"Saying this was common knowledge in 1996 is attributing your specialist knowledge to the entire population, who couldn't, and still can't, really be bothered by said knowledge."

Bad effects from smoking were know for years, same with the effects of asbestos, DDT. These days, it's fracking, global warming, junk-food and lack of exercise.

These ideas were all and are currently in the media. People being the irrational beings they are pick and choose what they want to believe. Belief doesn't change the truth.

[Intermernet]

The effects of smoking, Fracking, DDT, asbestos, global warming and junk-food have all had industry campaigns defending them. The only one in your list that hasn't is lack of exercise. This isn't to say that everything is a conspiracy driven by industry, but to illustrate that popular belief is often driven by popularist campaigns.

I would say that truth doesn't change belief, and unfortunately, it's belief that people act on.