Snorting cibachrome would knock you off your perch, but RA4 isn't all that bad. The developer smells pretty bad (strong amine smell, as with most chromogenic devs) and will cause skin sensitisation so I would never use it in a tray, but it's completely fine in drums. I use a Jobo and in most sessions, won't even get a whiff of it.

David: no. There's not enough silver in the paper, you need the dyes to get any meaningful density.