I’m surprised that Carter has lived this long. Like many of his generation, he probably smoked a lot during his years in the US Navy—hence the reason why we had a huge spate of World War II veterans die during the 1980’s and 1990’s from the adverse medical effects of smoking too many cigarettes.
It was those open vats of boiling degreasers used in all those factories thru the 1970’s.
There was a lot of asbestos on ships for fireproofing.
Asbestos plus smoking is an extreme negative synergy for lung cancer.
Back when I worked on vehicle brake design, a really smart engineer always told our mechanics it was deadly to smoke and breath brake dust.
After thirty years of non-smoking, your risk is about the same as someone who never smoked.
AFAIK, I don’t think he ever smoked, but his family has a history of cancer, given that history it’s amazing he made it to 90.