Third-hand smoke is just as deadly as first- and second-hand smoke, according to a recent study.
While first-hand smoke refers to the smoke inhaled by a smoker and second-hand smoke to the exhaled smoke and other substances emanating from the burning cigarette that can get inhaled by others, third-hand smoke is the second-hand smoke that gets left on the surfaces of objects, according to a press release.
Researchers from the University of California, Riverside conducted the first animal study of the effects of third-hand smoke. They found that third-hand smoke ages over time and becomes progressively more toxic.
"We studied, on mice, the effects of third-hand smoke on several organ systems under conditions that simulated third-hand smoke exposure of humans," Manuela Martins-Green, a professor of cell biology who led the study, said in a statement. "We found significant damage occurs in the liver and lung. Wounds in these mice took longer to heal. Further, these mice displayed hyperactivity."
They found alterations in multiple organ systems and excreted levels of a tobacco-specific carcinogen similar to those found in children exposed to second-hand smoke in mice exposed to third-hand smoke in the lab.
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 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, according to a press release.
In behavioral tests the mice exposed to third-hand smoke also showed hyperactivity.
"The latter data, combined with emerging associated behavioral problems in children exposed to second- and third-hand smoke suggests that with prolonged exposure, they may be at significant risk for developing more severe neurological disorders," Martins-Green said.
Investigators said third-hand smoke is a potential health threat to children, spouses of smokers and workers in environments where smoking is, or has been, allowed. Contamination of the homes of smokers by third-hand smoke is high, both on surfaces and in dust, including children's bedrooms.
Researchers said third-hand smoke, which contains strong carcinogens, has been found to persist in houses, apartments and hotel rooms after smokers move out.
Although the potential risks attributed to third-hand smoke exposure are increasing, virtually nothing was known about the specific health implications of acute or cumulative exposure -- until now.
Investigators said more research needs to be done.
"There is a critical need for animal experiments to evaluate biological effects of exposure to third-hand smoke that will inform subsequent human epidemiological and clinical trials," Martins-Green said.
