Diversity of Dangers of Thirdhand Smoke

While tobacco smoking is largely accepted as a significant source of primary indoor air pollutants, it is only recently that thirdhand smoke -- the invisible remains of cigarette smoke that deposit on carpeting, clothing, furniture and other surfaces – has become  recognized as a contributor to indoor pollution. Manuela Martins-Green, from the University of California/Riverside (California, USA), and colleagues studied an animal model that simulated third-hand smoke exposure of humans, to assess the effects of third-hand smoke on several organ systems.   The mice exposed to third-hand smoke in the lab showed alterations in multiple organ systems and excreted levels of a tobacco-specific carcinogen similar to those found in children exposed to second-hand smoke (and consequently to third-hand smoke).  In the liver, third-hand smoke was found to increase lipid levels and non-alcoholic fatty liver disease, a precursor to cirrhosis and cancer and a potential contributor to cardiovascular disease.  In the lungs, third-hand smoke was found to simulate excess collagen production and high levels of inflammatory cytokines (small proteins involved in cell signaling), suggesting propensity for fibrosis with implications for inflammation-induced diseases such as chronic obstructive pulmonary disease and asthma. In wounded skin, healing in mice exposed to third-hand smoke showed many characteristics of the kind of poor healing observed in human smokers who have gone through surgery. Finally, in behavioral tests the mice exposed to third-hand smoke showed hyperactivity. The study authors observe that: “with prolonged exposure, [children] may be at significant risk for developing more severe neurological disorders,” and submit that: “These results provide a basis for studies on the toxic effects of [thirdhand smoke] in humans and inform potential regulatory policies to prevent involuntary exposure to [thirdhand smoke].”