What Is Thirdhand Smoke?

Exposure may be particularly dangerous for infants and children

Thirdhand smoke is a relatively recent health concern in which nicotine and other chemicals from cigarette smoke remain on surfaces well after a person has smoked. These residues can then be ingested, inhaled, or absorbed through the skin, potentially increasing the risk of certain cancers and other serious diseases. Some of these chemicals can mix with common indoor pollutants to create toxins harmful to smokers and non-smokers alike.

Infants and small children are especially vulnerable due to hand-to-mouth behaviors. Although there are ways to remove thirdhand smoke from the home, the only surefire way is to protect yourself is to ban smoking where you live and to quit smoking if you do.

Routes of Exposure

Thirdhand smoke was a concept coined in 2009 by researchers at Massachusetts General Hospital in Boston in 2009. It is believed to pose health risks because the chemicals found in tobacco smoke don't dissipate in the air as one might suspect but rather cling to surfaces, objects, and fabrics in a room.

Unlike secondhand smoke, in which you inhale someone else's smoke, thirdhand smoke is the residue left behind that not only accumulates but can persist for months and even years.

This not only includes floors, walls, and counters but also clothing, furniture, toys, drapes, bedding, and carpets.

Unless the toxic chemicals are removed, they enter the body in one of three ways:

  • Ingestion: Nicotine and other chemicals from cigarette smoke can enter the body if you touch a surface and bring your hand to your mouth. Children can also ingest these substances by putting contaminated objects in their mouths.
  • Inhalation: Off-gassing is a term used to describe the release of residual contaminants back into the air, where they can be inhaled. This can occur while dusting, sweeping, shaking pillows, and turning on a fan or air conditioner.
  • Absorption: In the same way that nicotine patches deliver nicotine through the skin, nicotine and other chemicals left behind after smoking can be absorbed through the skin. Because children have more delicate skin, the potential risk of skin absorption may be greater.

Fabrics pose a special concern in that the chemicals from thirdhand smoke are difficult to remove from fibers and weave. A 2014 study published in PLoS ONE concluded than thirdhand smoke embedded in cotton terry cloth can potentially expose a toddler to seven times the amount of chemicals as passive smoking.

High humidity may reduce the risk by making the particles heavier and less likely to become off-gassed from surfaces. Regions with low humidity may have the opposite effect.

Chemicals in Thirdhand Smoke

Of the multitude of chemicals found in thirdhand smoke, there are several that are known to be carcinogenic (cancer-causing). These include arsenic, benzene, butane, cadmium, cyanide, formaldehyde, lead, nicotine, polycyclic aromatic hydrocarbons, and radioactive polonium-210.

There is also evidence that thirdhand smoke can react with common indoor pollutants to form all new and potentially more serious toxins. Among the concerns:

  • When mixed with nitrous oxide (created by fuel combustion and wastewater emission), the chemicals in thirdhand smoke can create carcinogenic nitrosamines associated with lung cancer, liver cancer, oral cancer, stomach cancer, and esophageal cancer.
  • When mixed with ozone (also generated from fuel combustion), the chemicals in thirdhand smoke break down into ultrafine particles, delivering formaldehyde and other carcinogenic compounds into the deeper airways of the lungs.

Dangers of Thirdhand Smoke

The research into thirdhand smoke is still relatively new, and, at present, many of the proposed hazards are more theoretic than established. With that said, there is mounting evidence of possible harms associated with thirdhand smoke. This includes:

  • Cancers: Nitrosamines above the recommended limits established by the U.S. Environmental Protection Agency (EPA) occur in 77% of smoker's homes. A 2014 review in the journal Environment International concluded that this translates to one case of cancer for every 1,000 people.
  • Coronary Thrombosis: Mice exposed to thirdhand smoke exhibited increased hemostasis (blood coagulation) and an increased risk of blood clots. Investigators with the Western University of Health Science concluded that this increases the risk of acute coronary thrombosis, which can obstruct blood flow to the heart and trigger a heart attack.
  • Fatty Liver Disease: Animal studies have shown that thirdhand smoke stimulates the accumulation of fat in liver cells, increasing the risk of non-alcoholic fatty liver disease (NAFLD). NAFLD is not only a precursor to cirrhosis and liver cancer but also a potential contributor to cardiovascular disease.
  • Hyperactivity: Secondhand smoke is linked to hyperactivity in children, and there is evidence that the same can occur with thirdhand smoke. This is likely caused by nicotine that acts as both a stimulant and depressant in the central nervous system.
  • Impaired Wound Healing: Thirdhand smoke was found to interfere with wound elasticity—in other words, how rapidly a wound heals and how extensively scar tissue develops.
  • Insulin Resistance: Studies in mice have found that the oxidative damage caused by thirdhand smoke reduces insulin receptors on pancreatic cells and increases the risk of insulin resistance (a precursor to type 2 diabetes).
  • Pulmonary Fibrosis: Animal studies suggest that off-gassed thirdhand smoke can affect the production of collagen in the smaller airways (bronchioles) and air sacs (alveoli) of the lungs, leading to the thickening and scarring of tissues (pulmonary fibrosis). This can further complicate breathing problems in people with asthma, COPD, or cystic fibrosis. It might even affect normal lung development in children

As concerning as these risks are on paper, it is still unknown how much thirdhand smoke contributes to the onset of disease. Some researchers express doubt, for example, that nitrosamines can be readily absorbed or ingested in a way that can directly link them to cancer or other illnesses. It is simply too early to say; further research is needed.

Where the risk is likely greatest is in newborns and infants due to their smaller size and undeveloped immune systems.

A 2014 study found that newborns living in homes where 10 or more cigarettes are smoked per day are more likely to hospitalized than those where smoking is banned. According to the researchers, homes with fewer than 10 cigarettes had the lowest level of thirdhand smoke on surfaces.

Thirdhand smoke may also add to the existing risk of secondhand smoke in smoking households. Unlike secondhand smoke, the risk of third-hand smoke can increase over time as more toxins are deposited on surfaces.

How to Avoid Thirdhand Smoke

The best way to avoid thirdhand smoke is to have a zero-tolerance policy for smoking in your home or vehicle. Unlike secondhand smoke, ventilation does little to remove thirdhand smoke. Once it is there, you may not even know it.

Even if smoking is stopped, don't expect the problem to spontaneously disappear. Research from the University of California Riverside found that thirdhand smoke can persist on surfaces, especially fabrics and furniture, for 19 months. Thirdhand smoke can even persist after a room is painted and recarpeted.

If you anticipate being exposed to thirdhand smoke, there are things that you can do to protect yourself and your family:

  • Do not allow smoking inside your home or car.
  • Do not allow smoking near your family or pets.
  • Educate your family and friends about thirdhand smoke so that they understand the rules of the house.
  • Advise caretakers of the rules of the house. If hiring a caretaker, be sure to include "non-smoker" in the job posting. (In some states, it is tricky and potentially illegal to ask a potential employee if they smoke.)
  • If you’ve been in a house with smokers, shower thoroughly with soap and warm water even if they weren't smoking in front of you. Clean any toys and clothes exposed to smoke with detergent and hot water. The same applies to pets.

How to Remove Thirdhand Smoke

Removing thirdhand smoke is tougher than it sounds. Washing or dry cleaning alone may not cut it. In order for a cleanser to remove nicotine, it must be acidic. Yet most soaps are alkaline and fail to remove nicotine even from smooth surfaces.

On the flip side, acidic solutions like vinegar can remove thirdhand smoke from surfaces, but it is not always practical as it can damage granite, marble, limestone, onyx, travertine, and grout and leave a vinegary smell.

The removal of thirdhand smoke from a home can be very costly. Before moving into a new house or apartment, ask the landlord about the history of smoking in the house and what has been done to remedy this if the previous tenants were smokers.

The non-profit American Nonsmoker's Right Foundation recommend that landlords take the following measures:

  • Thoroughly wash walls and ceilings with detergent and hot water.
  • Repaint walls with two or three coats of paint but only after the walls have been cleaned. Nicotine can still seep through three layers of paint.
  • Remove carpeting and padding, washing the floors thoroughly before recarpeting.
  • Remove wallpaper, and wash the walls thoroughly before repapering or painting.
  • Replace all curtains, windows, and blinds.
  • Clean out ventilation ducts, and replace filters in the air conditioner or heating system.

A Word From Verywell

Thirdhand smoke is a relatively new concept but one that should be of concern to parents. As there is no such thing as a "safe" amount of secondhand smoke, no amount of thirdhand smoke should be considered "safe" if you have a newborn or infant (or are living with a severe respiratory disease like COPD).

By instating a smoking ban in the home, you can significantly reduce your exposure to thirdhand smoke. However, if someone in your home does smokes, restricting smoking to outdoor spaces may not be enough. The only guaranteed solution is for them to quit smoking, ideally under the care of a doctor with approved smoking cessation aids.

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