Smoking a waterpipe for as little as an hour can trigger acute carbon monoxide poisoning, with symptoms including fainting, severe headaches and dizziness. A danger that extends to bystanders and café workers as well as those using the pipes.
The study, undertaken by a team from the University of Tsukuba in Japan, analysed 37 case reports covering 81 incidents of carbon monoxide (CO) poisoning or polycythemia (chronic CO poisoning) linked to waterpipe, hookah or shisha smoking. It is the first to systematically examine the behavioural and environmental factors behind these poisonings.
Researchers identified 68 cases of acute CO poisoning and 13 cases of polycythemia, predominantly affecting young adults aged 20-29. The most common symptoms were syncope (fainting), headache, dizziness, and nausea or vomiting—often occurring shortly after exposure, but in some cases delayed by hours.
Approximately one-quarter of cases developed symptoms only after individuals had left the smoking venue. About one-fifth occurred after less than one hour of waterpipe use, and another one-fifth occurred during outdoor smoking, demonstrating that even short-term or outdoor use does not eliminate the risk of CO poisoning.
Four cases involved individuals who had not smoked at all but were exposed to waterpipe smoke in enclosed spaces – including two workers in waterpipe cafés.
‘Both active and passive waterpipe smoking can cause acute CO poisoning, depending on the intensity, duration, and environment of exposure,’ the authors write. ‘Symptoms may arise not only during or immediately after smoking but also with a delayed onset.’
The review found that mass poisoning incidents, where multiple people were affected simultaneously, occurred primarily in closed environments such as basements and waterpipe cafés. In these cases, average carboxyhaemoglobin (COHb) levels – a marker of CO in the blood – were lower than in individual cases, suggesting that even moderate exposure in poorly ventilated spaces can affect multiple people.
Chronic exposure was also a concern. Among the 13 polycythemia cases, 12 involved daily waterpipe use. Polycythemia, a thickening of the blood caused by prolonged CO exposure, can lead to serious complications including deep vein thrombosis.
The researchers point to a critical gap in regulation. While waterpipe smoking has surged in popularity among adolescents and young adults in Western countries and Japan, environmental controls have not kept pace.
‘The implementation of environmental regulations for closed establishments is necessary to prevent mass CO poisoning and protect workers from it,’ the authors conclude.
They note that CO poisoning from waterpipes has been reported since at least 2009, and cases have risen alongside the global popularity of the practice. In Tokyo alone, 64 patients were transported to hospitals for acute CO poisoning from waterpipes over a 66-month period.
The authors call for further research into the behavioural and environmental factors that contribute to these poisonings, and for greater awareness among both users and health professionals that waterpipe smoke—often perceived as less harmful than cigarettes—carries significant acute risks.
‘Waterpipe-related poisoning incidents have risen in parallel with the growing popularity of waterpipe smoking,’ the study notes, urging that both public health messaging and regulatory action address this overlooked hazard.
The full research can be read here
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