TABLE I.

Comparison between second-hand smoke (SHS) and third-hand smoke (THS).

	Secondhand smoke (SHS)	Thirdhand smoke (THS)
Source	Composed of the main-stream smoke exhaled by active smokers and side-stream smoke expelled from the lit tobacco product	A residual contamination from tobacco smoke that remains after cigarette is extinguished, usually cling to hair, skin, clothing, and furniture surfaces
Major compounds	Benzene, toluene, styrene, acetone, xylene, naphthalene, formaldehyde, polonium-210, phenol, PAHs, nicotine, 3-ethenylpyridine, carbon monoxide, and N-nitrosamine	Nicotine, 3-ethenylpyridine, phenol, cresols, formaldehyde, tobacco-specific nitrosamines, naphthalene, xylene, styrene, benzene, and toluene (Basically, the compounds of THS are very similar to SHS but at lower concentration)
Related disease	Lung cancer, oral cancer, asthma, chronic obstructive pulmonary disease (COPD), and coronary heart disease	Allergic symptoms, asthma, and altering brain and lung development in children