My dad was always worried about botulism. I don't know what happened, but he would refuse to eat dented cans and things like that, just in case.

Botulism is why home canning is dangerous - more so than a factory.

Maybe lived through the famous nationwide botulism scare (the reason black olives are in cans to this day).

That was 1919: My dad was born in the 50's. His grandparents would have lived through it, though I'm not sure if one half was in the US at the time. I'd ask why, but he died some years back. I know that particular botulism outbreak still affects folks' attitudes towards pans.

I figure it was either stories from his parents - his father ran a grocery for some years. I know they had cans with missing labels around, but I don't think they had dents. Or it could be that someone (maybe him) got really sick. I just cannot remember - either one would make my father anxious, though. (He was cautious with car jacks, and always put a tire underneath. Something happened to someone he knew).

I do know that canned goods have gotten a bit safer, but not if the can has been dented or damaged.

Source? All I found was in line with https://www.smithsonianmag.com/history/botulism-outbreak-gav... that covered olives being part of the scare, but no source said black olives were only to be sold in came because of it.

I also thought black olives can be purchased in glass jars ...