Thirdhand tobacco smoke: emerging evidence and arguments for a multidisciplinary research agenda

Abstract

Background: There is broad consensus regarding the health impact of tobacco use and secondhand smoke exposure, yet considerable ambiguity exists about the nature and consequences of thirdhand smoke (THS).

Objectives: We introduce definitions of THS and THS exposure and review recent findings about constituents, indoor sorption-desorption dynamics, and transformations of THS; distribution and persistence of THS in residential settings; implications for pathways of exposure; potential clinical significance and health effects; and behavioral and policy issues that affect and are affected by THS.

Discussion: Physical and chemical transformations of tobacco smoke pollutants take place over time scales ranging from seconds to months and include the creation of secondary pollutants that in some cases are more toxic (e.g., tobacco-specific nitrosamines). THS persists in real-world residential settings in the air, dust, and surfaces and is associated with elevated levels of nicotine on hands and cotinine in urine of nonsmokers residing in homes previously occupied by smokers. Much still needs to be learned about the chemistry, exposure, toxicology, health risks, and policy implications of THS.

Conclusion: The existing evidence on THS provides strong support for pursuing a programmatic research agenda to close gaps in our current understanding of the chemistry, exposure, toxicology, and health effects of THS, as well as its behavioral, economic, and sociocultural considerations and consequences. Such a research agenda is necessary to illuminate the role of THS in existing and future tobacco control efforts to decrease smoking initiation and smoking levels, to increase cessation attempts and sustained cessation, and to reduce the cumulative effects of tobacco use on morbidity and mortality.

Figure 1

Physical-chemical processes of nicotine reactions with nitrous acid on indoor surfaces. (A) Illustration of surface-mediated nitrosation of nicotine. (B) Proposed mechanism for the formation of TSNAs. Adapted from Sleiman et al. (2010b). Abbreviations: (a), proposed mechanism for formation of NNA; (b), proposed mechanism for formation of NNK; (c), proposed mechanism for the formation of NNN; (g), gas phase; HCHO, formaldehyde; (s), on surface; secondary products are those created by indoor chemical reactions from primary tobacco smoke products (e.g., NNK from nicotine).

Figure 2

Mass spectrum and size distribution of secondary organic aerosol generated during nicotine reaction with ozone. Adapted from Sleiman et al. (2010a) with permission from Elsevier. dN/dlogP is the normalized particle number per size range.

Figure 3

Reaction products and proposed pathways (shown by arrows) for nicotine reactions with ozone. Reprinted from Sleiman et al. (2010a) with permission from Elsevier. m/zis the mass to charge ratio used to interpret mass spectral data.