Old movies with dangerous “special effects” that weren’t special effects

Anyone ever watch an old movie (pre-60s) and wonder how they did that cool special effect but then you google it and find out it wasn’t an effect? They actually did that super dangerous thing, people got sent to the hospital, a crew person died, and the actors got cancer some years later, then you’re just like, oh 😳

I can think of a couple like people actually trapped in a burning building, lots of real “almost hit by a train” scenes, the famous asbestos used as snow. What else you got?