Cadmium Selenide, Cadmium Sulfide, Cinnabar and Lead Oxide toxicity
I found an answer to my question. Typically oil paint manufacturers will write what pigments are used in their paints. The pigments are classified according to the 'color index' or C.I. These pigments may actually have different chemical composition, but nevertheless the color index can be used to search the pigment database here: http://www.artiscreation.com/red.html

For example, PR106 stands for genuine Vermillion, which is true Cinnabar and has a toxicity rating of C according to the table linked above, where A is non-toxic and D is extremely toxic.

Most colors that are marketed as 'cinnabar' are actually composed of various different pigments, most often not actually containing mercury.