That's what the hookah smokers always seem to claim, but the NYT says yes they are:

That study also found that the water in hookahs filters out less than 5 percent of the nicotine. Moreover, hookah smoke contains tar, heavy metals and other cancer-causing chemicals. An additional hazard: the tobacco in hookahs is heated with charcoal, leading to dangerously high levels of carbon monoxide, even for people who spend time in hookah bars without actually smoking, according to a recent University of Florida study.