The amount of lead you are gonna get from a single fitting or two is minuscule. You could eat the whole thing and it’s probably not gonna do anything to you. Brass alloys typically have trace lead, which is why this warning is put on them.

Prop 65 warnings have to be put on anything or anywhere that has even trace residues of listed substances. It’s a total chicken little law. Restaurants have to post prop 65 signs because seafood and cooked meat they serve could have listed substances in them.