For whatever its worth, over 500 thousand a year die due to the use of tobbaco, about 250 thousand die from booze and not one death has been reported caused by pot.
One of the reasons drug legalizers always get the dog walked on them in debates is because they utilize this supposed "statistic". As if sucking the smoke of one type of burning leaves into your lungs is significantly less hazardous than another? Neither is extremely bright from a long term health standpoint, the only reason you don't have a "pot" column is that no one has an agenda to regulate it or tax it for its evils (since its illegal) and therefore they don't actively track it like booze or smokes.
That's baloney. Plenty of studies have indicated that smoking XX amount of grass is equivalent to smoking an ungodly amount of cigarettes. The anti-grassers love quoting this meaningless stat, and would like nothing more than to pin XX,XXX number of deaths per year on the hazards of smoking grass.