Indeed. My father quit smoking from one day to the next in the mid-60s, when a surgeon friend showed him photos of a smoker's lung. The info was available.
I'm glad to hear that your father successfully quit his first time. According to the American Cancer Society, he belongs to a 7-percent minority. Please see my response above for more statistics and qualitative data about what information was - and is - available.
1) Understood by whom?
2) How deep was the "understanding?" In other words, what did it signify for people's health and well being?
If your argument is that medical professionals understood the health risks associated with smoking by the late '70s, I agree. But everyday people, those most affected by smoking-related illnesses, continue to underestimate the danger.
"Smokers underestimated their relative risk compared to non-smokers and, contrary to previous
interview surveys, believed they have a lower risk of developing lung cancer than the average smoker."
"These findings suggest that at least heavy smokers significantly underestimate their risk of premature mortality."
So, this leads to the second question: how does smokers' understanding of risks — or lack thereof — have practical implications for their behavior?
Among current U.S. smokers, the odds of wanting to quit, trying to quit and successfully quitting are still quite poor. About 30 percent of smokers do not want to quit. Sixty percent reported that they will not try to quit this year. And only seven percent reported successfully quitting their first time.