Have a look at the Printing Inks Manual 5th Ed. 1993 available on Amazon!
They list the ingredients which contain natural and synthetic rubbers, metals as pigments, and rubber chemicals mainly used for curing and cross-linkage which are commonly used in leather tanning, printing industry, all forms of rubber gloves, and many dental materials.
The toners are <9 microns in size, aero-allergens, and electro-statically charged so just by looking at a printout opening a book or walking into a room over carpets you attract these allergens. They mostly affect your face, eyes, lips, hands and forearms. These same chemicals are also found in shampoos, dyes....My guess is its also a cause of delayed chronic occupational related asthma