We've known since the mid-1900s that smoking causes lung cancer and health problems for those who smoke. Some years after that, we discovered that secondhand smoke, or the smoke passively inhaled by those who are around smokers, is harmful to health as well.
This month, a new study released by the Lawrence Berkeley National Laboratory found that third-hand smoke may be even more dangerous than second-hand smoke.
What is third-hand smoke? It's the nicotine residue that settles from exhaled cigarette smoke and clings to literally any surface, from clothing and carpets to cars and people.
It doesn't take a scientist to make the deduction that if both first-hand and second-hand smoke are dangerous, then third-hand smoke might be, too. But the effects of third-hand smoke on health have often been considered minimal or insignificant. The Berkeley study is important because it proves for the first time that third-hand smoke is just as mutagenic (read: cancer-causing) as other kinds of smoke.
One of the reasons that third-hand smoke is so dangerous is that though it contains less chemicals or tobacco by-products than second-hand smoke, the few that it does contain have an affinity to react with common household air pollutants, like ozone and nitrous acid. The resulting particles are incredibly damaging to cells, but are also tiny enough to enter a human body with minimum difficulty. They can be ingested, inhaled, or even quite literally "pass through human tissue," including skin.
Furthermore, third-hand smoke is near impossible to get rid of. Most smokers try to get rid of the smell of cigarette smoke by vacuuming, dusting, washing linens, and spraying air freshener. But none of these gets rid of stubborn third-hand smoke, and studies have so far found that the nicotine residue can last for at least two months after the last smoke, though some scientists say that it probably lasts a lot longer. In fact, it's so difficult to eliminate that the Berkeley study's recommended way to get rid of it is to just replace whatever might have been contaminated, whether it's a carpet or the bedsheets.
There is one silver lining here. Apparently, the acuteness or intensity of the third-hand smoke you're exposed to doesn't seem to matter as much as how often you're exposed to it. It has a much greater cumulative effect, which might be good or bad news depending on how you often you face such smoke.
The moral of the story is one that we already knew but bears repeating: Smoking is bad. It's bad for the smoker, it's bad for their family, and it's also bad for anyone they come into contact with.