One Marijuana Joint Produced 4.4 Times More Fine Particles Than a Tobacco Cigarette Indoors | Research

The takeaway

Controlled experiments in a two-story house found that smoking one marijuana joint produced 4.4 times the average PM2.5 concentrations compared to one tobacco cigarette, and opening windows only partially reduced levels.

Public health officials setting indoor air quality policies; landlords and property managers; household members concerned about secondhand smoke.

4.4x more PM2.5 from marijuana vs tobacco; opening windows cut levels 67%

What the researchers found

A marijuana joint produced average 5-hour PM2.5 concentrations of 38.9-80.7 mcg/m3 across three experiments, compared to 15.0-15.2 mcg/m3 for a tobacco cigarette. Opening three windows reduced marijuana smoke PM2.5 by 67%, but levels still exceeded those from tobacco with windows closed.

Why it matters

As marijuana legalization spreads, understanding secondhand smoke exposure in homes is critical. The finding that marijuana produces substantially more fine particles than tobacco in the same home environment has direct implications for household members, including children.

The numbers in context

Tobacco cigarette: 5-hour mean PM2.5 of 15.2 and 15.0 mcg/m3 (2 experiments). Marijuana joint: 38.9, 79.8, and 80.7 mcg/m3 (3 experiments). Ratio: 4.4x more PM2.5 from marijuana. Opening 3 windows by 12.7 cm reduced marijuana PM2.5 by 67%, but levels remained above tobacco levels with windows closed.

How the study worked

Controlled experiments in a detached two-story, 4-bedroom home using research-grade calibrated PM2.5 monitors in all 9 rooms. Machine-smoked a Marlboro cigarette (2 experiments) or pre-rolled marijuana joints (3 experiments) in the living room. Measured 5-hour PM2.5 concentrations.

What this study cannot tell us

Machine smoking may not perfectly replicate human smoking patterns. Only one brand of cigarette and pre-rolled joints were tested. The house had specific ventilation characteristics that may not represent all homes. Only PM2.5 was measured, not chemical composition.

How to read the evidence

Moderate: controlled experimental conditions with calibrated instruments and repeated measurements, though limited to one house and machine smoking.

When this study was published

Published in 2022.

The bigger picture

This is among the most rigorous indoor air quality comparisons of marijuana versus tobacco smoke. The 4.4x difference likely reflects the larger joint size and different combustion characteristics. These data support extending indoor smoking restrictions to marijuana.

Questions still open

How do other consumption methods (vaping, edibles) compare for indoor air quality? Does the chemical composition of marijuana PM2.5 differ from tobacco PM2.5 in health-relevant ways? Would whole-home ventilation systems adequately address marijuana smoke?

Common questions

Why does marijuana produce more smoke than tobacco?

A marijuana joint is typically larger than a cigarette, burns at different temperatures, and users tend to hold smoke longer. The study used pre-rolled joints versus standard cigarettes, so the size difference contributes to the PM2.5 gap.

Does opening windows solve the problem?

Opening three windows reduced marijuana PM2.5 by 67%, but the resulting levels still exceeded what a tobacco cigarette produced with windows closed. Ventilation helps but does not eliminate the exposure.

Read the original research

Measuring PM2.5 concentrations from secondhand tobacco vs. marijuana smoke in 9 rooms of a detached 2-story house.

The Science of the total environment, 852, 158244

View on PubMed ↗Publisher’s paper ↗

Citation

Ott, Wayne R; Wallace, Lance A; Cheng, Kai-Chung; Hildemann, Lynn M. (2022). Measuring PM2.5 concentrations from secondhand tobacco vs. marijuana smoke in 9 rooms of a detached 2-story house.. The Science of the total environment, 852, 158244. https://doi.org/10.1016/j.scitotenv.2022.158244