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Third-hand Smoke Equal to Second-hand Smoke

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This past summer, we learned about the effects of thirdhand smoke.  Thirdhand smoke is a term for the toxins that are left behind on surfaces in rooms where cigarette smoke was released from people smoking cigarettes. A new study finds that the effects of thirdhand smoke may also be coming from the smokers’ bodies and clothes.

 In the previous study, exposure to thirdhand smoke for only 3 hours was enough to cause free radicals and oxidative stress to increase in the mitochondria in the cells lining the nose.  The research identified one of the pathways involved in the cells’ response, upon which cells depend for survival.  The reaction from cells trying to self-protect from the harmful cell changes that nicotine and smoke causes is significant.  This survival mechanism is activated only minutes after direct exposure to nicotine—and as we found out from this study, being in an environment where smoke had once been also activates this cellular survival pathway.  

Another study released earlier this month has found more evidence of the harmful effects of thirdhand smoke.  This study found that the people who smoke cigarettes are themselves off-gassing harmful carcinogenic toxins.   The pollutants released from smokers’ clothes and bodies released in the time span of just one hour was enough to equal the amount of second-hand smoke that 1-10 cigarettes releases.

This information means that merely being in the physical proximity of a smoker (who isn’t actively smoking) is just as harmful as standing next to someone actively smoking.  The researchers focused on a case study in a modern, non-smoking movie theater where they arranged smokers to enter the theater at a specified time.  The air quality in the movie theater was monitored and emission rates for the volatile organic compounds (VOCs) were recorded.

Of all the volatile compounds released and measured, over 51% of the compounds were acetic acid, acetone, and acetaldehyde.  Other notable emissions included 2,5-dimethylfuran, a marker used to measure indoor tobacco smoke.  One cigarette releases an average of 210 micrograms of 2,5-dimethylfuran, which is one of the ways the study calculated what the emissions from the smokers in the theater would translate into in direct cigarette smoke. 

The study was conducted during a family movie and also during an R-rated movie.  The emissions during the family movie were lessened, and there was a sharp increase in the emissions during the movie meant for an adult audience.

The study did an excellent job of setting up several control measures, such as not recirculating air in the theater and only using fresh air, to ensure that the results gathered were not skewed.  It’s a very interesting study worth reading with some very serious implications for smokers and non-smokers alike.


Sheu, Roger, et al. “Human Transport of Thirdhand Tobacco Smoke: A Prominent Source of Hazardous Air Pollutants into Indoor Nonsmoking Environments.” Environmental Studies, vol. 6, no. 10, 4 Mar. 2020, doi:10.1126/sciadv.aay4109.

Pozuelos, GL, et al. “Experimental Acute Exposure to Thirdhand Smoke and Changes in the Human Nasal Epithelial Transcriptome: A Randomized Clinical Trial.” JAMA Netw Open, vol. 2, no. 6, June 2019, doi:10.1001/jamanetworkopen.2019.6362.


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