Sir, I would like to add some further useful references to Drs Dar-Odeh and Abu-Hammad's interesting paper on narghile (hookah, shisha) smoking.1 For instance, Indian cancer specialists have earlier noted that the South-East Asian water pipe 'does not appear to produce precancerous oral lesions'.2 Regarding smokeless tobacco, the important fact that tobacco smoking and chewing act synergistically is indeed noteworthy.3 Also, an impressive study about leukoplakia showed that hookah smoking 'did not lead to any appreciable number of lesions, because neither the smoke nor the pipe are too warm'.4

As for the study on bronchogenic carcinoma,5 not only were 14 of the 17 smokers heavy users (>110 g, ie the weight equivalent of 110 cigarettes) and the hygienic conditions unknown but also in the same region, Jindal et al. showed that almost one third of all patients with bronchogenic carcinoma and 94.4% of the 54 women had never smoked.6 Pollution, kerosene, and even radon are important. In fact, about two dozen publications point in the other direction, including the first aetiological study ever carried out on this issue with exclusive/ever hookah smokers.7 As for the other scarcely reported cases of other types of cancer (oesophageal, bladder, pancreatic) and other diseases (contact eczema, tuberculosis or aspergillosis, etc), the attention was often drawn to a non-rigorous methodology (simultaneous use of other products eg qât, cigarettes, bidis, pan, etc; strongly neglected hygiene; unclear current profile and past smoking career).8 This applies to the few cases of oral squamous cell carcinoma studied by El-Hakim et al. who, surprisingly, also mention 'the heat generated from the smoke' and the 'irritation by tobacco juice products'.9 This is not possible because the inhaled hookah smoke temperature is below that of the ambient air and, unlike a cigarette, pipe or cigar, no 'tobacco juice' can reach the smoker's mouth further to a trip of up to 200 to 300 cm on average (not to mention the bath).

Dar-Odeh and Abu-Hammad1 warn against the great amount of 'tar'. However, cigarette 'tar' and hookah tar are completely different. Narghile smoke is mainly made up of water and glycerol (no biological activity) and is far less concentrated in chemicals (hundreds vs thousands) than cigarette smoke.8 As for the great amounts of aldehydes and polycyclic aromatic hydrocarbons, these are not those of human 'smoking sessions' but those artificially produced by an unrealistic narghile smoking machine (one puff every 17 s for a full hour...) supposed to mimic the average narghile smoker. Amazingly, the only hot debate has been about the international standard smoking machine for cigarettes which draws only but a few puffs every 60 s. Hookah smoking machines set with different parameters revealed completely different toxicant yields.8,10,11,12 As a conclusion, the main clearly and early identified public health problem is carbon monoxide.8,13 Unfortunately, tobacco harm reduction policies are still taboo so the hookah epidemic has been worsening for a decade now.14