Oil Painting and Chemistry
One of the things I've learned since starting into the oil painting thing is a highly narrow bit of chemistry. Each color is caused by pigment (mostly). And a lot of those pigments are quite unpleasant to the body: cadmiums, chromiums, cobalts, and more. But, specifics of how the specific compound affects the body is indicative of whether it will harm the body when it's in a paint form.
Lead pigments (there are 3 or so for lead white, along with some yellow/red varieties) harm the body when eaten. Cadmium pigments (cadmium seleno-sulfides, mostly) are less bad; they will stay in you if eaten, sort of. Apparently particle size is a significant aspect to this, and modern artist pigments are designed to limit harm this way. Cobalts and chromiums are considered less harmful- not sure why. Mangenese can cause issues as well- in specific forms.
This goes on and on, of course. It's quite an education in what constitutes "toxicity".