I remember seeing advice, years ago, to let lettuce sit in a weak bleach solution before use. But I doubt that’s ever been followed by many people. Current advice (at least at home) seems to be to rinse lettuce to remove dirt ( https://hgic.clemson.edu/factsheet/safe-handling-of-lettuce-... ). Apparently most health problems from lettuce are on the surface and not particularly hard to get off.