Anyone who has been around people smoking marijuana with a bong know that it produces a lot of secondhand smoke. Now Patton Khuu Nguyen and Kathy Hammond have shown that the amount of secondhand smoke is huge. Their paper, “Fine Particulate Matter Exposure From Secondhand Cannabis Bong Smoking” published in JAMA Network Open reports the amont of ultrafine particle (PM2.5) pollution in an apartment where students were smoking marijuana in a bong.
Pollution levels peaked out at 1200 to 2500 µg/m3 way above the 35 µg/m3 EPA standard for outdoor air and 5-10 times higher than the EPA threshold for hazardous air pollution, 250 µg/m3.
These levels are higher than observed for tobacco smoke, including when generated by a hookah.
These ultrafine particles compromise functioning of blood vessels and lungs and increase the risk of heart and lung disease. More people end up in emergency rooms on days with high ultrafine air pollution.
The full citation is: Nguyen PK, Hammond SK. Fine Particulate Matter Exposure From Secondhand Cannabis Bong Smoking. JAMA Netw Open. 2022 Mar 1;5(3):e224744. doi: 10.1001/jamanetworkopen.2022.4744. PMID: 35353170. It is available for free here.
Stanton Glantz blog 
For comparison purposes: this is what it looks like when you’re approaching 300:
The marijuana bong passed 300 in the first ten minutes.
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