The health risks associated with hookah usage are still relatively unstudied when compared to those of cigarettes or other means of tobacco consumption.[citation needed
] A common belief among younger users is that the smoke is significantly less dangerous than that from cigarettes.[citation needed
] The water moisture induced by the hookah makes the smoke less irritating and may give a false sense of security and reduce concerns about true health effects.
Doctors at institutions including the Mayo Clinic
have stated that use of hookah can be as detrimental to a person's health as smoking cigarettes,
and a controversial (see below) study by the World Health Organization also confirmed these findings.
Each hookah session typically lasts more than 40 minutes, and consists of 50 to 200 inhalations that each range from 0.15 to 0.50 liters of smoke.
Research shows that a single 45-minute session of hookah tobacco smoking (tobacco molasses) delivers slightly less tar
and carbon monoxide
(around 3-6%) than smoking a cigar.
The water used in the hookah bowl is often thought to have some filtering function as well as cooling and humidification of the smoke product. The water does clearly collect material from the smoke as it takes on a smell and residue may be visible after extended use without changing, however, whether this function has any health benefits is unclear.
The first[citation needed
] aetiologic study on hookah smoking and cancer
was published in May 2008. The authors find various levels of carcinogenicity in hookah usage (remarkably lower than in cigarette use). 
2005 World Health Organization report
In 2005, the World Health Organization
published a report regarding the use of water pipes
that noted the dangers of hookah usage. One year later, this document was criticized
in the Journal of Negative Results in Biomedicine
for what researchers claimed to be errors and misinterpretations in the original report. The WHO report findings were contested regarding its results in pertaining to the following aspects of hookah usage:
[LIST][*]biomedical (chemistry of smoke, health effects)[*]sociological (women and children use)[*]anthropological (Middle East, Asia, Africa, use in a real environment, types of smoking mixtures and pipes, and the consequences of modeling a complex social and human situation)[*]historical (about the origins of the device, since the first two sentences of the WHO report are inaccurate in this respect).[/LIST] The report has also been criticized for publication bias
It should be noted that the WHO report is not a study per se
but only a summary of studies selected by its authors for the purpose of issuing recommendations aiming at supporting national bans on.