Frequently Asked Questions

Thirdhand smoke (THS) is the contamination that persists in the air and on surfaces after smoking has stopped. Smoking a cigarette generates two kinds of tobacco smoke: mainstream smoke that is inhaled by the smoker and sidestream smoke from the smoldering cigarette. Secondhand smoke (SHS) is a combination of the sidestream smoke and the mainstream smoke exhaled by smokers. Thirdhand smoke (THS) refers to the SHS gases and particles that stick to and become embedded in materials and objects, like carpet, walls, furniture, blankets, and toys. THS is not strictly smoke, but chemicals that adhere to objects from which they can release back into the air or accumulate in house dust. Some chemicals in THS are not released by the cigarette, but result from chemical transformation of tobacco smoke components that happen in the environment. THS can linger indoors for a long time - months to years. People can be exposed to THS by touching contaminated surfaces (absorption through the skin), by eating contaminated objects or dust, and by breathing in air and re-suspended THS components.

Tobacco smoke can adhere to indoor surfaces such as walls, windows, furniture, and floors. It does not simply blow away. Smoke can also adhere to skin, hair, and clothing, and can be transferred into environments where smoking is not allowed. Layers of THS residue can build up over time and can remain there for years because common cleaning methods such as vacuuming and wiping surfaces do not remove THS.

Touch - You can be exposed if you touch a surface near where someone has smoked. Your skin will absorb the particles.

Smell - It is possible to breathe in THS particles in the air.

Ingestion - Young children are at risk of ingesting THS when they teethe on household objects that are contaminated with tobacco smoke residue.

Burned tobacco products (eg. cigarettes, hookah), electronic cigarettes, and smokeless tobacco have all been shown to leave nicotine and/or tobacco smoke residue in indoor environments.

Many of the harmful chemicals that are present in mainstream tobacco smoke and secondhand smoke (SHS) are also present in THS. Levels in the air of some of these chemicals even increase over time. Health effects of exposure to mainstream and SHS is greatly known. The reports of the United States Surgeon General have concluded that every organ in the body can be harmed by exposure to cigarette smoke. We also know a great deal about the toxins in tobacco smoke and how they cause disease.

Currently, there is very little information on the unique health effects of THS because research on THS and health have only recently begun. We do know that THS is a source for long-term exposure to harmful pollutants because they can persist on surfaces for months, or even years. The most common complaints from people exposed to THS are the bad smell and taste of air, stuffy nose, eye irritation and symptoms of allergy. These are concerns, but not yet definite evidence, that asthma could be aggravated by THS exposure. Studies have demonstrated harmful effects of THS in cultured cell systems and animal models, but these have not yet been shown to occur in people. Some examples are: 1) In an experiment involving the buildup of THS on cloth over a year, researchers found that the cloth became very contaminated. If an infant were to suck on even a small piece of the cloth, the infant could absorb a substantial dose of specific tobacco carcinogens (chemicals that cause cancer) equivalent to about one-third of the daily dose to a cigarette smoker. 2) Smoke from very few cigarettes created a THS residue that killed human and mouse cells cultured in the laboratory. This same sample of THS also produced breaks in DNA (genetic material found in cells). This is a concern since failure to properly repair DNA strand breaks can lead to mutations in the DNA and this may eventually lead to cancer. 3) THS can release volatile chemicals (gases that are in the air). Some of these gases have been shown to injure or kill mouse cells in culture. Acrolein, an example of one of the gases that may be part of THS, is believed to contribute to cancer and heart disease. 4) Most cells in the human body contain small "organelles" called mitochondria, which produce the fuel that drives and controls vital cell processes. THS causes a phenomenon called "stress-induced mitochondrial hyperfusion" which stresses cells and can eventually lead to cell death. 5) Mice exposed to THS develop signs of liver damage and changes in blood sugar and insulin levels similar to those found in diabetics. These conditions worsen when mice are fed a high fat ("western") diet when exposed to THS. Mice also have signs of a generalized inflammatory condition, can show delayed wound healing and can develop signs of hyperactivity. Research is ongoing to confirm if the harmful effects of THS observed in cultured cells and animals occur in people.

Possibly. THS has been found in homes with no-smoking rules and homes of non-smokers where smokers have previously lived. In hotels with only partial smoking restrictions, THS has been found in both smoking and non-smoking rooms. Also, depending on smoking rates and vehicle turnover frequency, it is likely that many rental cars and used cars will have THS contamination.

Children and Families - Infants and small children are likely to have more exposure to THS than adult because THS contaminates house dust and surfaces. Infants and children spend more time on the floor, have frequent hand to mouth behaviors, explore objects in their environment with their mouth, put non-food items in their mouths, engage in active play at home, and breathe in more dust-contaminated air than adults, in relation to their body size. They also may be more susceptible to the harmful effects of THS contaminants than adults, as children may metabolize chemicals differently than adults, are rapidly developing, and have more years of life ahead. High levels of THS breakdown products have been measured in the urine of infants and young children. Renters - People who live in rental homes or apartments are at higher risk of THS exposure because properties change occupants frequently and smoking bans often do not apply to private spaces such as homes. Children who live in apartments show a higher level of exposure to tobacco chemicals than children who live in detached housing, even when they are not exposed to secondhand smoke. Occupational Exposure - Employees and patrons in environments where smoking is allowed (eg. hotels, casinos) are more likely to be exposed to THS.

• Don't allow smoking at any time indoors, near children, and near homes where smoke could enter through windows, doors, or ventilation systems.
• Minimize children's contact ith adult skin and clothes that have been contaminated with THS. This might include having smokers wash their hands, shower, change, and/or wash their clothes before coming in contact with children.
• Perform frequent surface cleaning, dusting, and vacuuming with HEPA filter equipped vacuum cleaners. Avoid carpet for flooring.
• Create and insist on smoke-free environments for the child, including smoke-free multi-unit housing, home smoking bans, tobacco-free caregiver environments, hotels, cars, and playgrounds.

There are sensitive tests that can measure the potential for human exposure by collecting and testing samples of chemicals present in air, dust and surfaces. These environmental samples allow for the determination of concentrations of TS-derived toxins to which people are in contact. However, these tests are not commercially available at this time.

Exposure to THS-derived toxic chemicals might also be studied by quantifying the presence of specific tracers (biomarkers) in body fluids such as blood, urine, and saliva. These biomarker measurements can give a picture of exposures over different time ranges ( typically a few days). Finding one or more biomarkers of THS is a major goal of the California Consortium on Thirdhand Smoke.

The most effective way to reduce THS exposures is by strictly enforcing indoor smoking bans. In homes which there has been smoking activity in the past, odors and toxic chemicals may linger several months, or even years, after smoking ended. Those homes may require replacement of the TS-affected materials (eg. carpet, Sheetrock), or a thorough professional clean-up. Using an ozone generator is not recommended because ozone can react with THS chemicals to make them more toxic.

Marijuana - Marijuana cigarettes contain a leaf that is usually burned, and do produce a TS-like residue which would include the user's exhaled smoke and the smoke that it emitted from the burning end of the cigarette. Although marijuana products have not yet been studied as thoroughly as tobacco products, marijuana aerosol contains some of the same ingredients as tobacco smoke. They produce particulate matter that contains carcinogens also found in tobacco smoke. Therefore, many of the toxins present in THS will likely be found in the THS from marijuana.

Electronic Cigarettes - Electronic cigarettes, or e-cigarettes, do not burn a leaf and therefore do not produce side-stream smoke. E-cigarettes heat a fluid containing a mixture of chemicals that creates and aerosol vapor that looks like cigarette smoke. Users of e-cigarettes may exhale large amounts of vapor which settles on indoor surfaces, much like THS. The major concern about e-cigarette residues is that early research has found that nicotine deposited on surfaces reacts with a common environmental chemical to produce carcinogenic tobacco specific nitrosamines. This reaction could occur with nicotine derived from e-cigarette aerosol.

Many states in the U.S. and many countries worldwide prohibit smoking indoors at work to protect employees from exposure to secondhand smoke. With the exception of some hospitals, we currently do not know of any workplace protections against THS exposure. In the absence of legal protections, it is important to educate co-workers and supervisors about the nature of THS pollutants, THS exposure, and exposure-related risks.This is particularly important if someone suffers a precondition that creates special health risks or sensitivities (eg. asthma, pregnancy). If those efforts are unsuccessful, we suggest contacting your HR department or union representatives, and seeking assistance from a local tobacco control advocacy group

Stale or aged tobacco smoke odor is easily recognized and almost universally experienced as unpleasant. When one smells tobacco smoke, it is an immediate warning sign that one has just inhaled and been exposed to a mixture of volatile tobacco smoke pollutants that include known irritants, inflammatory agents, and known and suspected human carcinogens. Because odors are only experienced if a compound is present above a threshold concentration, the absence of odor cannot be interpreted as the absence of exposure to tobacco smoke pollutants. The presence of odor does indicate that THS is present.

When outdoor smokers come inside, the odor they emit is not simply a nuisance. The tobacco smoke odor we smell is a direct sign that a mixture of odorant and odorless tobacco smoke pollutants has been brought into the home on the clothes, skin, hair, and in the exhaled breath of the smoker. Inside the home, the pollutants off-gas into the air, and nonsmokers are now exposed to them through inhalation. In addition, some of these compounds will now adsorb, deposit, and accumulate in the indoor environment even though no cigarettes were smoked indoors. There are three main strategies for preventing tobacco smoke pollutants from clothes and on persons from entering and building up in a home

1) Leave clothes worn while smoking outside the home (e.g., patio, garage).

2) Immediately wash clothes worn while smoking.

3) Ask smokers to wash their hands and shower immediately upon entering the home.