Secondhand marijuana smoke reached concerning levels at golf courses and other outdoor locations | Research

The takeaway

Observational measurements found secondhand marijuana smoke PM2.5 levels up to 149 micrograms per cubic meter at outdoor locations, with over 20% of golf course visits encountering marijuana smoke.

Environmental health researchers, cannabis policy makers, public health regulators

Peak secondhand marijuana PM2.5: 149 ug/m3 at outdoor locations

What the researchers found

Across 24 visits to 10 golf courses, over 20% of visits encountered marijuana smoke, with peak PM2.5 exposures reaching 149 micrograms per cubic meter. Average outdoor exposures near public smoking/vaping were more than 3 times higher than those near enclosed sources. In-car secondhand smoke leakage produced higher outdoor exposure than building-based indoor emissions.

Why it matters

As cannabis legalization expands and outdoor use increases, understanding secondhand exposure levels in public spaces helps inform policies about where cannabis smoking should be permitted.

The numbers in context

24 visits to 10 golf courses; >20% of visits encountered marijuana smoke; peak PM2.5 up to 149 ug/m3; outdoor smoking/vaping exposure >3x higher than near-car or near-building emissions; 23 total exposure events documented

How the study worked

Pilot observational study measuring PM2.5 exposure from marijuana smoke at golf courses (24 visits to 10 courses over 6 months) and other outdoor locations (public parks, near parked cars, near residential garages). Total of 23 marijuana exposure events documented.

What this study cannot tell us

Pilot study with small number of measurement events. PM2.5 levels alone do not identify specific harmful compounds in marijuana smoke. Golf courses may not be representative of all outdoor exposure scenarios. Cannot determine health effects from measured exposure levels.

How to read the evidence

Novel pilot observational study with direct measurements, but small number of events and inability to characterize specific smoke components are limitations.

When this study was published

Published 2023

The bigger picture

Most secondhand smoke regulations focus on tobacco and indoor spaces. This study highlights that outdoor marijuana smoke exposure in public settings can reach levels of concern, potentially necessitating cannabis-specific outdoor smoking policies.

Questions still open

At what PM2.5 level does secondhand marijuana smoke become a health concern? Should outdoor cannabis smoking regulations mirror tobacco smoking restrictions?

Common questions

How much secondhand marijuana smoke is there in outdoor public spaces?

This study found peak PM2.5 levels of 149 micrograms per cubic meter near outdoor marijuana smokers, and over 20% of golf course visits encountered marijuana smoke exposure.

Is outdoor marijuana smoke worse than smoke leaking from buildings?

Yes. Average outdoor exposure near someone openly smoking or vaping marijuana was more than 3 times higher than exposure near a car or building where marijuana was being used indoors.

Read the original research

PM2.5 exposure to marijuana smoke on golf courses and other public outdoor locations: A pilot observational study.

The Science of the total environment, 896, 165236

View on PubMed ↗Publisher’s paper ↗

Citation

Cheng, Kai-Chung; Huang, Gan; Hildemann, Lynn M. (2023). PM2.5 exposure to marijuana smoke on golf courses and other public outdoor locations: A pilot observational study.. The Science of the total environment, 896, 165236. https://doi.org/10.1016/j.scitotenv.2023.165236