Exactly, you mention beliefs, while the point was (is?) one of science. By the way, have you ever heard of banning coal BBQs? I'm not sure at all that the exposure is less severe. Say you are at a party, there's a BBQ 20ft away, and some annoying guy lights a cig 10ft away. I'd bet you money that the BBQ harms you more, or at least emits more than 4 times (you need to scale by the square, diffusion of a fluid) PM2.5 than the cigarette.