New Study Shows Thirdhand Smoke from THC Reacts in the Air to Form New Compounds

A new study by Drs. Aaron Wylie and Jonathan Abbatt from the University of Toronto Department of Chemistry demonstrates that THC from cannabis smoke reacts with ozone in the air to create new chemicals that can linger on walls and furniture.

December 2, 2020

By: American Chemistry Society

THC, the psychoactive component of cannabis, is found in secondhand smoke from cannabis and remains on nearby surfaces after smoking stops. Researchers reporting in the December issue of Environmental Science & Technology have demonstrated that ozone –– a component of outdoor and indoor air –– can react with THC that is deposited on glass or cotton surfaces and the reaction produces new compounds. The researchers describe these compounds for the first time.

Smoking cannabis or tobacco emits chemicals that remain in the air (secondhand smoke) or deposit onto surfaces, including walls, windows, clothing, and upholstery (thirdhand smoke). Unlike the secondhand variety, thirdhand smoke can linger long after a person stops smoking. Nicotine, a chemical in thirdhand tobacco smoke, reacts with other chemicals in the air and on surfaces, producing new compounds that can also become airborne. Because the smoke from cannabis is chemically different from tobacco smoke, University of Toronto researchers Drs. Aaron Wylie and Jonathan Abbatt wanted to characterize the compounds formed when THC reacts with ozone in the air.

The researchers coated glass and cotton cloth, to simulate windows and clothing, with a THC solution. Then, they exposed the surfaces to concentrations of ozone that could exist in indoor air. In their analysis, they found that over time, the amount of THC on glass and cotton decreased, while the quantities of three THC oxidation products increased.

In other experiments, the team used a smoking machine to deposit cannabis smoke onto cotton. Upon exposure to ozone, the same three compounds formed at roughly the same rate as observed for the THC-coated cloth. The health effects of these compounds are unknown at this time.

The researchers say that, because of the low volatility of THC and the three oxidation products, the compounds are likely to be emitted into the air where they could be inhaled in smaller amounts than nicotine from thirdhand tobacco smoke. They say, however, that somebody could still be exposed to thirdhand THC and these new compounds through ingestion if they, for example, put a contaminated object or their fingers in their mouth after touching a surface contaminated by cannabis smoke. 


Note: Content was edited for style and length

Click here to read the research study.

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