Emerging investigator series: deposited particles and human lung lining fluid are dynamic, chemically-complex reservoirs leading to thirdhand smoke emissions and exposure

Thirdhand smoke (THS) persists in locations where smoking previously occurred and can be transported into non-smoking environments, leading to non-smoker exposure. Laboratory experiments using high-resolution mass spectrometry demonstrate that deposited particulate matter (PM) and smoke-exposed surrogate lung lining fluid (LLF) are substantial, chemically-complex reservoirs of gas-phase THS emissions, including hazardous air pollutants, polycyclic aromatic compounds, and nitrogen/oxygen-containing species. Both PM and LLF are persistent real-world THS reservoirs that chemically evolve over time, and can act as vehicles for the transport and emission of reactive pollutants and their reaction byproducts (e.g., acrolein). Deposited PM on clothes, furnishings, bodies, and/or airways will emit volatile to semi-volatile gases over long lifetimes, which can re-partition to other indoor materials and increase their overall persistence. On the other hand, LLF off-gassing consists predominantly of volatile organic compounds in amounts influenced by their aqueous solubilities, and their persistence in breath will be prolonged by re-distribution across internal aqueous reservoirs, as corroborated by multicompartment modeling in this study.

Automated summary

Thirdhand smoke (THS), the residual smoke left in a location where smoking has occurred, can persist and expose non-smokers to harmful substances. Laboratory experiments have shown that deposited particulate matter and smoke-exposed surrogate lung lining fluid are reservoirs of gas-phase THS emissions containing hazardous air pollutants and other harmful compounds. These reservoirs can transport and emit reactive pollutants and their byproducts, increasing their overall persistence. The off-gassing of THS from deposited particulate matter and lung lining fluid can also contribute to indoor air pollution.