When I was younger I thought second hand smoke was a myth. I smoked. Before I quit and even now I have given smoking a lot of thought. It does cause cancer and second hand smoke does too. Second hand smoke is not filtered by the lungs. It is smoke not consumed by the body and just blown out into the air and then breathed in by someone else. Of course it causes cancer just as much as first hand smoke because in reality second hand smoke is first hand smoke. Think about it.
Third hand smoke is not really smoke but the chemicals from smoking landing on everything and then obsorbed through the skin by anyone touching it. Third hand smoke is also first hand smoke turned back into a solid. No longer a vapor by heat. No different than ice melted then frozen again. Nitrous acid in the air mixes with the tobacco vapor and then lands on anything. We pick it up through our skin. Nothing good comes from smoking cigarettes. Even Marijuana should not be smoked but consumed as food. Marijuana is not toxic to the body according to DEA Judge Francis L. Young in his ruling dated Sept 6, 1988. Marijuana does not cause cancer. Tobacco does. Even ingested. People die from snuff and chewing tobacco. Mouth cancer, throat cancer, etc. Not Marijuana. Nitrous Acid comes from combustion. Research it and how it gets into our houses. Here is one link: http://journals.lww.com/epidem/Abstract/2004/07000/Exposure_to_NO2_and_Nitrous_Acid_and_Respiratory.15.aspx