Scientists are reporting that thirdhand smoke (THS) — the invisible remains of cigarette smoke that deposits on carpeting, clothing, furniture and other surfaces — may be even more of a health hazard than previously believed.

Lauren M. Petrick, Alona Svidovsky, and Yael Dubowsk, Faculty of Civil and Environmental Engineering, Technion – Israel Institute of Technology, Haifa, Israel, showed that nicotine, a major constituent of THS, participates in surface reactions with indoor oxidants, such as ozone or NOx, resulting in the formation of secondary organic aerosol (SOA) and surface products.

Exposure to these potentially toxic pollutants can occur to babies crawling on the carpet or people napping on a sofa. Also dermal and hand-to-mouth exposures are possible, e.g., people eating food tainted by thirdhand smoke.

While the half-life of sorbed nicotine is approximately 11.5 h at [O₃] = 55 ppb, unpublished studies of cotinine oxidation estimate a half-life of 5 d at the same ozone concentration. Thus, personal exposures may continue to occur on the order of hours to days.

• Thirdhand Smoke: Heterogeneous Oxidation of Nicotine and Secondary Aerosol Formation in the Indoor Environment,
  Lauren M. Petrick, Alona Svidovsky, Yael Dubowsk
  Environ. Sci. Technol. 2011, 45 (1), 328–333
  DOI: 10.1021/es102060v