Marijuana Smoke Contains Some Chemicals at Higher Levels Than Tobacco Smoke | Research

The takeaway

Systematic comparison found marijuana smoke contained up to 20 times more ammonia and 3-5 times more hydrogen cyanide and nitric oxide than tobacco smoke, though some carcinogens were lower.

Read this if you smoke marijuana and want to know exactly what chemicals are in the smoke compared to tobacco.

Marijuana smoke: 20x more ammonia, 3-5x more HCN than tobacco smoke

What the researchers found

Researchers prepared marijuana and tobacco cigarettes identically and analyzed their smoke under two standardized smoking conditions, comparing both mainstream (inhaled) and sidestream (environmental) smoke.

Mainstream marijuana smoke contained ammonia at levels up to 20-fold higher than tobacco. Hydrogen cyanide, nitric oxide, and certain aromatic amines were found at 3-5 times higher concentrations in marijuana smoke.

However, some polycyclic aromatic hydrocarbons (PAHs), known carcinogens, were actually lower in mainstream marijuana smoke compared to tobacco. The pattern reversed for sidestream smoke, where marijuana had higher PAH concentrations.

The overall composition was qualitatively similar between marijuana and tobacco smoke, meaning they contained the same types of chemicals, but in different quantities.

Why it matters

While tobacco smoke chemistry is extensively documented, marijuana smoke had received limited analysis. This systematic comparison provided the first comprehensive side-by-side data, revealing both reassuring findings (lower PAHs in mainstream smoke) and concerning ones (much higher ammonia and HCN).

The numbers in context

Ammonia: up to 20x higher in marijuana smoke. Hydrogen cyanide, NO, NOx, aromatic amines: 3-5x higher in marijuana. PAHs: lower in mainstream marijuana but higher in sidestream marijuana smoke.

How the study worked

Marijuana and tobacco cigarettes were prepared identically and machine-smoked under two standardized conditions. Both mainstream and sidestream smoke were analyzed for the complete suite of chemicals routinely tested in tobacco smoke, including ammonia, hydrogen cyanide, nitrogen oxides, aromatic amines, and PAHs.

What this study cannot tell us

Machine smoking may not replicate human smoking behavior (marijuana users typically inhale more deeply and hold longer). The study analyzed chemicals but did not measure health outcomes. Marijuana cigarette composition varies widely in the real world.

How to read the evidence

This is a well-controlled laboratory analysis comparing standardized cigarettes under consistent conditions, providing moderate evidence about smoke chemistry (though not health outcomes).

When this study was published

Published in 2008. This study is frequently cited in discussions of marijuana smoke health risks. The rise of vaporization and edible consumption has since reduced reliance on smoking for many users.

The bigger picture

This study helped move the conversation about marijuana smoke health risks from assumption to data. The finding that marijuana smoke is not simply "the same as tobacco smoke" but has its own distinct chemical profile is relevant for public health communication.

Questions still open

Do the higher ammonia and HCN levels in marijuana smoke translate to measurable respiratory harm? Does the typical marijuana smoking pattern (deeper inhalation, longer breath-holding) amplify exposure to these chemicals?

Common questions

Is marijuana smoke safer than tobacco smoke?

This study showed it's not a simple comparison. Marijuana smoke had higher levels of some harmful chemicals (ammonia, HCN) but lower levels of others (some PAHs). The different smoking patterns also matter. Neither can be considered "safe" to inhale.

Does vaporizing avoid these chemicals?

Vaporization heats cannabis below combustion temperature, which should avoid producing most combustion byproducts like ammonia, HCN, and PAHs. However, vaporizer emissions have their own chemical profiles that are still being characterized.

Read the original research

A comparison of mainstream and sidestream marijuana and tobacco cigarette smoke produced under two machine smoking conditions.

Chemical research in toxicology, 21(2), 494-502

View on PubMed ↗

Citation

Moir, David; Rickert, William S; Levasseur, Genevieve; Larose, Yolande; Maertens, Rebecca; White, Paul; Desjardins, Suzanne. (2008). A comparison of mainstream and sidestream marijuana and tobacco cigarette smoke produced under two machine smoking conditions.. Chemical research in toxicology, 21(2), 494-502.