Caroline Halsted and Alex Pew, National Center for Health Research
The dangers of smoking tobacco and exposure to second-hand smoke are well-known, but did you know that third-hand smoke can also cause serious health problems?
People can be exposed to second-hand smoke any time they are around someone who is smoking a cigarette. It comes from both the smoke from the tip of the cigarette and the smoke that the smoker is exhaling.[1] Second-hand smoke causes about 600,000 premature deaths every year worldwide.
The dangers of third-hand smoke were first introduced in 2006. Third-hand smoke (THS) is the tobacco residue that can remain on surfaces and dust for months after someone smokes a cigarette.[2] In some situations, third-hand smoke can even remain on fabric for a year and a half after the last exposure to cigarette smoke.[3] This residue can cause coughing, asthma, and respiratory tract infections.[4] Third-hand smoke is more likely to remain on indoor surfaces. Even in seemingly tobacco-free places, tobacco residue can remain on walls, floors, furniture, clothing, and even hair for months after a cigarette is smoked.[5] A study investigating the effects of short-term third-hand smoke found that exposed mice were more likely to develop lung cancer compared with mice that were not exposed to THS.[6]
Exposure usually occurs through skin contact. When someone touches a surface that has smoke residue on it, that residue ends up on their hands and becomes more of a risk when they touch their face or mouth. Non-smokers living in homes that were inhabited by smokers previously often have residue left on their hands.[5] One study found that THS can still be found in dust from homes 2 months after smokers moved out and the house had been cleaned.[7] Another study found that smokers’ homes contained THS even 6 months after they stopped smoking.[8] There is no research that looks at the THS levels in households years after smokers move out.
Exposure to THS can also occur outside of the home. A longitudinal study looking at second-hand and third-hand smoke in a casino found extremely high levels of residue on surfaces and in dust. For example, visiting this casino once for 4 hours significantly increased a person’s THS exposure. After a one-month smoking ban, surface nicotine decreased by 90% but nicotine and cancer-causing chemicals that were in dust decreased more slowly. It took 3 months for nicotine and cancer-causing chemicals in dust to decline by 90%. Fortunately, 6 months after the smoking ban, there was little risk of THS exposure from a single 4-hour visit to the casino.[9]
Because of the way people are most often exposed to third-hand smoke, children are particularly vulnerable. Children often crawl and play on the floor and furniture, and frequently make hand-to-mouth contact or put their mouths on household objects. Even so, many parents aren’t aware of the dangers of environmental tobacco smoke.
Parents should know that if they smoke in the car, their children can absorb the dangerous chemicals from the car upholstery, even if the child wasn’t inside at the time of the smoking. The same is true for smoking inside of the home. The more parents are aware of this issue, the less childhood exposure there will be. The American Academy of Pediatrics emphasizes that quitting smoking is the only way to ensure that your child is not exposed to third-hand smoke.[10] Make sure your friends aware of the dangers of third-hand smoke, and make sure you and your family avoid areas with possible environmental tobacco exposure. Smoking outside decreases exposure to third-hand smoke, but friends and family members will still be exposed to THS on the skin, hair, and clothes of smokers. While occasional exposure to low levels of THS is not expected to have long-term effects on health, frequent exposure may increase the risk of developing cancer.
The studies show that the amount of THS in air and dust in businesses and homes remains longer than you might expect but decreases with time. Thoroughly cleaning your home, washing or dry-cleaning clothing, and vacuuming your car and help remove dangerous chemicals that are left over after smoking. If you are working towards quitting or have already quit, it makes sense to thoroughly clean fabrics in order to reduce your and your family’s risk of exposure even more.[3]
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