Re: possibly dangerous particles in hookah smoke.
It probably isn't the actual smoke. I have sucked hookah smoke through super fine filter paper and I couldn't detect any particulate matter on the filter paper with an analytic balance. Detection meaning a difference in the final mass after drying and initial mass that is larger than the .00001g that the balance is capable of measuring.
And I will have to dig up some old HS science fair data on particulate matter present in the air in smoking vs. non-smoking venues and the O2/CO2 concentrations in smoking vs. non-smoking environment. Obviously you can guess what trend I found. Maybe I will have to dig out the stuff I made for the first and get some sensors for the second and test my local hookah bar a few times and set it up and smoke with friends like I normally would.