A new study has found that secondhand cannabis smoke from bongs can be even more harmful than tobacco due to an increased concentration of fine particulate matter.
Researchers from the University of California, Berkeley, who published their report on the Jama Open Network this week, conducted their experiment with students from the university. They measured levels of fine particulate matter before, during and after eight cannabis social-smoking sessions in the living room of an apartment near campus.
They found that secondhand bong smoke contains fine particulate matter in much higher concentrations and is more dangerous compared with secondhand tobacco smoke.
The students, who provided their own cannabis and bongs, remained anonymous and were not observed during the two-hour smoke sessions.
“We exerted no control and gave no direction to the students on how to smoke the cannabis in the bong,” said S Katharine Hammond, a professor who oversaw the study alongside graduate student Patton Khuu Nguyen, to the San Francisco Chronicle. “They were free to smoke as much as they wanted when they started the session.”
Hammond and Nguyen used an aerosol monitor to measure the air quality before, during and after each session, which they then compared with the data collected from tobacco smokers in a hookah setting.
They found that fine particulate matter from cannabis bong smoking was at least four times greater than the smoke produced by tobacco.
“Patton and I compared the particulate exposure from the bong hits to the air quality of the orange sky days after the wildfires of September 2020 … The concentrations were five to 10 times greater in the living room during the smoking,” Hammond told the Chronicle.
The study, conducted over two months in 2018, also found that fine particulate matter concentrations took a significantly long time to return to pre-smoking levels. In one of the sessions, the concentration stayed at more than 10 times the original concentration level, 12 hours after the group had stopped smoking.
Cannabis has long held a reputation as less harmful than cigarettes, but Hammond said she hopes the study will alert people to the reality that it comes with its own serious risks to the smoker and those around them.
“This cohort study suggests that, contrary to popular beliefs, bong smoking is not safe … Incorrect beliefs about SHCS [second hand cannabis smoke] safety promote indoor cannabis smoking,” the study said.
“It can actually affect the health of children who are nearby or other people in pretty serious ways,” Hammond added in a statement to USA Today. “We need to wake up to that.”