Well, if you take some lab rats (hairy screed comes to mind), and force them into inhaling the equivalent of 10 packs per day, I guess you could conclude that the rats are gonna have an issue with 2nd hand smoke. Say, who’s getting the 1st hand smoke and forcing the rats to inhale it?
Has there been a study done of putting people in a closed room for two hours and filling it with exhaust fumes from one car; another room with people in a room where everyone smokes and see which room has more deaths? Oh then there should be a third room filled with carbon monoxide which emits no odor.