They're as silly as they sound. Growing up, there was a sign when you enter the school's bus storage and maintenance area. More recently, I've seen them at Starbucks (for coffee), in the vinegar section of the grocery store, and on untreated lumber.
This isn't California being California, but it is well-meaning legislation getting out-of-hand because of enforcement mechanisms. It's like website cookie warnings. It was a nice idea, but it lead to a silly place.
Replying because I remembered coffee too, and had to look it up. ‘Good’(?) news is that it was decided in 2019(!) that coffee does not require a Prop 65 warning.
This isn't California being California, but it is well-meaning legislation getting out-of-hand because of enforcement mechanisms. It's like website cookie warnings. It was a nice idea, but it lead to a silly place.