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

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.

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.

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.

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.

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.