Carbon Monoxide, Charcoal and Shared Hoses in Hookah Use

Canadian public health sources treat waterpipe smoke as harmful. Health Canada names hookah among the tobacco products whose smoke raises your risk of negative health effects. Public Health Ontario’s September 2021 evidence brief goes further on specifics: it cites a study measuring 57.2 to 367 mg of carbon monoxide per waterpipe session against 14 to 23 mg for one cigarette, and it ties much of that to the charcoal used to heat the tobacco.

What Health Canada says

Health Canada does not have a standalone page on waterpipe health that we could find. Two of its pages carry relevant statements. Its second-hand smoke page says the smoke from the lit end of a tobacco product such as a cigarette, pipe, cigar or hookah increases your risk of negative health effects. The same page lists carbon monoxide, benzene, formaldehyde and hydrogen cyanide among chemicals formed during combustion in every smoked tobacco product, and says second-hand smoke contains more than 7,000 chemicals, of which hundreds are toxic.

The 2022 Canadian Tobacco and Nicotine Survey summary reports that 0.6% of Canadians aged 15 and older, about 180,000 people, used a water-pipe to smoke tobacco in the past 30 days. That figure was unchanged from 2021. The warnings printed on waterpipe tobacco packs are covered on our cigar, pipe and hookah tobacco page.

Carbon monoxide and charcoal

Public Health Ontario, an Ontario government agency, reviewed 32 systematic and other reviews published from 2015 onward. It reports a study finding that waterpipe smoke contains 57.2 to 367 mg of carbon monoxide per smoking session, whereas one cigarette yields 14 to 23 mg. The amount in waterpipe smoke is largely due to the amount of charcoal used. Electric heating lowered it, but it raised volatile aldehydes, which are linked to respiratory disease, so the brief says there is no safe heating method.

The brief also reports that exhaled carbon monoxide and carboxyhemoglobin were significantly higher in waterpipe smokers than in non-smokers and than in cigarette smokers. It notes that some waterpipe smoking can lead to carbon monoxide poisoning that needs medical attention.

How it compares with cigarettes

The brief concludes that both waterpipe and cigarette smoking are harmful, with many similar health effects. Tobacco-based waterpipe smokers are exposed to similar levels of nicotine and to significantly lower levels of tobacco-specific nitrosamines. In five studies that compared the smoke itself, waterpipe smoke contained more particulate matter, carbon monoxide, polycyclic aromatic hydrocarbons, volatile aldehydes, tar and toxic metals than cigarette smoke.

All nine reviews on lung cancer found positive associations with waterpipe smoking, with odds ratios between 2.12 and 4.58. Results were mixed for head and neck, gastric and bladder cancers. Six reviews on smoking during pregnancy found a link to low birth weight, and one strong-quality meta-analysis put the odds ratio at 2.39.

Shared hoses and bowls

The brief says smoking and sharing a waterpipe may spread infectious pathogens because the equipment is not cleaned well enough between smokers. It reports that the effectiveness of disposable mouthpieces is undetermined, since contamination can sit in the hose and the water bowl, which are cleaned less often and are harder to clean. The COVID-19 point in the brief rests on known facts about the virus and typical waterpipe use, with no real-world study behind it.

Lounge air

The brief reports one study of waterpipe lounges with fine particulate matter at 515 micrograms per cubic metre, against a US Environmental Protection Agency limit of 35. A study of waterpipe lounges across Canada, where presumably only herbal products are smoked, also found hazardous levels of particulate matter. Non-smoking sections of waterpipe cafes had similar levels to restaurants where cigarettes are smoked, so a separate smoking area inside a venue does not remove the risk to non-smokers. The rules that apply to these venues are set out in the provincial hookah lounge comparison.

How strong the evidence is

Of the 32 reviews, nine were rated strong, nine moderate and 14 weak. Many of the underlying studies did not control for other tobacco smoking, and many were done in Middle Eastern or other developing countries, which limits how well the results transfer to Canada. The brief says that makes it difficult to assess the true harms of waterpipe-only smoking.

What we could not confirm

• A Health Canada page that compares waterpipe and cigarette harm directly. We found none, so every comparison above comes from Public Health Ontario.
• Waterpipe findings from the Alberta Chief Medical Officer of Health report and from Ottawa Public Health. We could not open those pages.
• Whether Public Health Ontario has updated the brief since September 2021.
• The original studies behind the figures. We read the brief’s summary of them, so check the brief’s reference list before quoting a number as the study’s own.