Everyone knows that smoking tobacco is really bad for your health. And everyone knows that indirect secondhand exposure to tobacco smoke is really bad, especially in children.  Now there is evidence that thirdhand smoke — residual chemical compounds from tobacco, including nicotine, that stick to clothing, drapes, bedspreads, ceiling tiles, carpeting and other indoor surfaces — can be absorbed, ingested, and inhaled for months and even years after the smoke vanishes, continuing to damage health. Last year, Matthew Diebel reported on the effect thirdhand smoke has on mice:

A study by scientists at the Department of Energy’s Lawrence Berkeley National Laboratory found that newborn mice that lived in cages containing smoke-treated fabric for three weeks weighed significantly less than their counterparts in a control group. In addition, both newborn and adult mice exposed to thirdhand smoke experienced changes in blood cell counts associated with the immune system, leading to inflammatory and allergic reactions.

The research team believes the results of the mice experiment can apply to humans, too.


Especially, Diebel says, human children:

In a paper published in the journal Scientific Reports, Hang’s team noted that human babies and toddlers are at greater risk because they come into contact with contaminated surfaces while crawling on carpets and sleeping on smoke-infused bedding.


William Wan finds more data revealing health dangers from the persistence of toxic tobacco chemicals in indoor environments:

One study this year showed third-hand smoke increased risk of lung cancer in mice. Another study last year showed liver damage and diabetes in mice. A third study this year focused on casinos and showed that six months after smoking was banned, heavy smoke residue remained on the walls and carpet.

The latest study, published Wednesday in the journal Science Advances, shows how tobacco smoke from outdoor air can seep into a nonsmoking classroom and coat its surfaces, and how those hazardous chemicals often become airborne again and circulate throughout buildings via central air conditioning systems.

“It shows that just because you’re in a nonsmoking environment, it doesn’t mean you aren’t exposed to tobacco,” said Peter DeCarlo, an atmospheric chemist at Drexel University in Philadelphia and lead author of the study. “That Uber car you jump into, the hotel room you stay in, even a classroom where smoking hasn’t been allowed for decades: These are places where you are often exposed to a lot more than you expect.”


Cleveland Clinic asked pulmonologist Humberto Choi to identify 5 dangers of thirdhand tobacco smoke — especially to children and other non-smokers:

1. Thirdhand smoke may be a culprit in more cancer cases

“There’s been an increased interest recently because we are seeing more lung cancer cases that are not related directly to firsthand or secondhand smoking,” Dr. Choi says. “So we’re looking at other causes for cancer aside from direct exposure.”

2. Thirdhand smoke may damage DNA

One study found that being exposed to thirdhand smoke may cause damage and breaks in human DNA. Researchers tested human cells in a laboratory rather than actual humans. But Dr. Choi says DNA damage is a real risk and can increase your chances of disease.

3. Residue may react with airborne chemicals to form carcinogens

When you smoke in a room or car, toxic chemicals like nicotine cling to walls, clothing, upholstery and other surfaces, as well as your skin. Results of a study published in 2010 found that when this nicotine reacts with nitrous acid in the air, it forms carcinogens, which are compounds that can cause cancer.

Although this suggests a dangerous connection, “It hasn’t been proven that thirdhand smoke is correlated with any other conditions,” Dr. Choi says. “And that will be very difficult to prove because we are all exposed to it no matter how hard we try to avoid it.”

For this reason, the specific risks of thirdhand smoke are still not completely clear, he says.

4. Children are most at risk

“I think children are the most vulnerable to thirdhand smoke because of exposure to surfaces like the floor and on their clothes and other objects in the house,” Dr. Choi says.

This is particularly true for very young children who frequently touch objects and then put their hands in their mouths. This can increase their exposure to the toxic chemicals.

Non-smoking adults who live with regular smokers are also at a much higher risk for thirdhand smoke exposure. Dr. Choi says it may be helpful to study these individuals in the long term.

5. Removing the residue is very difficult

Thirdhand smoke residue builds up over time on most surfaces it touches. It can remain for weeks, months or even years. It resists normal cleaning methods and you can’t air it out of rooms or cars with fans or vacuums, Dr. Choi says.

For this reason, sometimes the only solution is replacing carpets, repainting walls and/or cleaning ventilation systems. So it’s expensive to completely rid a room of thirdhand smoke and eliminate the risk of exposure to future tenants or owners.


Caitlin O. Smith asked a pediatrician:

Jonathan Klein, M.D., FAAP, an associate executive director of the American Academy of Pediatrics, likens second- and thirdhand smoke to lead. “These days,” he said, “people wouldn’t think twice about the fact that you can’t have lead paint flakes in a house where children live. So if you think about the parallel, then is it OK to have circulating second- and thirdhand smoke toxins in the air that children are forced to breathe? No, of course not.”


The AAP recommends:

  • Do not allow smoking inside your home or car
  • Do not allow smoking near you, your children, or your pets
  • Ask anyone who cares for your child or pet to follow these rules- and tell them why
  • E-cigarette vapor or aerosol also contains chemicals. Do not let anyone use e-cigarettes in your home, car, or near your child or pet
  • The only way to completely protect against thirdhand smoke is to quit. The AAP recommends talking to your child’s pediatrician about ways to keep your child healthy



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