An Interview with the Director

Joseph Martin from the Rover Tobacco Control Library at UC Davis, interviewed Dr. Georg Matt, Professor at San Diego State University and Director of the Thirdhand Smoke Resource Center, to learn more about thirdhand smoke. Read or listen to their conversation.

By Joseph Martin
June 2019

Listen to the podcast here or read below.

Hello, and welcome to Bytes, a podcast produced by the Rover Tobacco Control Library at UC Davis. I’m Joseph Martin, and in this episode we’re going to be speaking with Dr. Georg Matt about thirdhand smoke.

Dr. Matt is a Professor and Chair of the Department of Psychology and the Director of the Thirdhand Smoke Resource Center at San Diego State University. His research has focused on the protection of nonsmokers from exposure to tobacco smoke, and he has been the author or co-author of a number of groundbreaking studies on thirdhand smoke. We were very pleased to be able to set up a telephone interview, so let’s welcome him to our program. Thank you for speaking with us, Dr. Matt!

Dr. Matt: 
You are welcome. Thank you very much for inviting me.

Mr. Martin:
I think it’s interesting that you’re coming to tobacco control from a background in Psychology, and I wonder if you wouldn’t mind telling us a little about how you got interested in tobacco control, and when you first started research related to thirdhand smoke?

Dr. Matt:
I moved to San Diego in 1988, the year when Prop 99 was approved on the November ballot and added a 25 cent tax on each pack of cigarettes.  In 1995 and 1996 my son and daughter were born, and around the same time, California banned smoking in most indoor workplaces, including bars, restaurants.  This was a pretty radical idea back then.  As expected, these policies had an immediate and dramatic impact on secondhand smoke exposure in the workplace, bars, and restaurants, but these policies did not address smoking in private homes, cars, and apartment buildings. Unfortunately, this is where children spent most of their time and where children get exposed to secondhand smoke. 
With two small children at home, it became clear to me that the otherwise very progressive smoking policies of the 1990s had a big loophole because they did not directly impact the environments most important to children.  With small children at home, I was also reminded that children experience their physical environment very differently from adults. They crawl around on floors, play on carpet, and collect on their hands and clothes quite a bit of dust and dirt. They want to touch, feel, and explore every possible object with their little hands, and then put their fingers and everything nearby in their mouths: their parents’ fingers, toys, keys, remote controls – you name it. 
As a psychologist interested in health behaviors, these observations raised some important questions: what are the different pathways through which children are exposed to tobacco smoke? And how can we help parents who smoke avoid exposing their children to secondhand smoke?  One strategy is to adopt strict home smoking bans and to never smoke near a child. But when we studied the impact of home smoking bans, we ran into an interesting puzzle:  Why is it that children continue to show exposure to tobacco smoke chemicals even if their parents don’t smoke indoors, nobody smokes near the children, and even if parents had quit smoking altogether?
We found answers to this puzzle when we looked closer at the properties of the chemicals that make up tobacco smoke. We learned that tobacco smoke leaves behind a residue – chemical compounds that can stick to almost anything they come in touch with.  This is what launched our research on thirdhand smoke. It became clear to us that if we want homes, hotels, and cars that are 100% free of toxic tobacco smoke pollutants, we not only have to prevent secondhand smoke, but we also have to address the toxic residue that smoking leaves behind in indoor environments.

Mr. Martin:
I think most listeners will be familiar with the concept of secondhand smoke, but what is thirdhand smoke? How does it differ from secondhand smoke, and how do we become exposed to it? 

Dr. Matt:
In a nutshell, thirdhand smoke is the chemical residue that is left behind in all indoor environment where tobacco has been smoked.  It collects in dust, accumulates on surfaces, and becomes embedded in any and all objects you can find in an indoor environment. That includes carpets, furniture, pillows, blankets, toys, cups, plates, bookshelves, books, clothes, towels — simply everything.
While the term thirdhand smoke is relatively new, we have known about, smelled, seen, felt, and known about thirdhand smoke for a long time. If you ever attended a party were people smoked, you have smelled thirdhand smoke on your clothes the next morning.  If you ever had the misfortune to arrive late at a hotel and were assigned a smoker room, you have smelled the unpleasant odor of thirdhand smoke. If you every stood next to a smoker in an elevator, you know that thirdhand smoke comes off a smoker after she or he smoked. Or if you ever looked at a new apartment where the walls had a brown-yellowish discoloration you have seen thirdhand smoke.
While we have known about the unpleasant smell and stains of thirdhand smoke for many years, it has only been over the last 15-20 years that scientists paid serious attention to what this smell and what these stains are all about.  We now know that thirdhand smoke is not just a bad odor or and brownish stain. 
Thirdhand smoke is a mixture of toxic chemical left behind by secondhand smoke that remains on surface and in dust that is re-emitted into the air, that is re-suspended from dust deposits, and that reacts with oxidants and other compounds in the environment to produce new pollutants.  Tobacco smoke does not just disappear in thin air. Tobacco smoke leaves behind a toxic legacy that can remain for years after a cigarette has been extinguished. 

Mr. Martin:
Who’s most at risk? Are some people more vulnerable than others?

Dr. Matt:
To understand who is most vulnerable and most at risk, it is important to understand how exposure to thirdhand smoke takes place.  Exposure to secondhand smoke takes place when we inhale air that contains the side stream smoke from a smoldering cigarette and the main stream smoke that is exhaled by a smoker.  Secondhand smoke exposure occurs while someone smokes or shortly after someone smokes.
When we talk about thirdhand smoke, exposure takes place not only by inhaling the air in a room or car where previous users have smoked.  Exposure can also take place through the skin by dermal transfer through and by putting polluted objects in your mouth. Dermal transfer could take place when a child plays on a carpet, holds a toy, or wears clothes that are polluted with thirdhand smoke.  Thirdhand smoke can be ingested when, for instance, children put toys or fingers in their mouths, or when we eat off plates that have been polluted with thirdhand smoke.  
Given this multiple pathways of exposure, we believe that young children are the group most at risk for thirdhand smoke exposure.  More than any other age group, young children spend time indoors where thirdhand smoke may be present. They explore their surroundings with their hands and mouths. And because their organ and immune systems are not yet fully developed, they are more vulnerable to the disruptive and damaging properties of thirdhand smoke chemicals.  In addition to children, we know that persons with respiratory and cardiovascular illnesses and those with compromised immune systems are more likely to feel the short-term effects and long-term consequences. Finally, thirdhand smoke exposure is contributing to health disparities found among lower-income, lower-education, ethnic-racial minorities.  This is partly because housing is often more affordable in older, multi-unit buildings where thirdhand smoke levels are higher. 

Mr. Martin:
How long does thirdhand smoke persist in a home, or a vehicle, or a workplace? Is there any way to remove it once it’s been found to be present?

Dr. Matt:
Thirdhand smoke builds up over time in carpets, walls, furniture, toys, pillows, etc. creating reservoirs where thirdhand smoke can be stored for years.  Exactly how long thirdhand smoke persists depends on how much and over what period of time tobacco smoke was able to build up. In one case, the owner of a large house was a heavy smoker and when she passed away, the house was left unoccupied and was sold a year later.  When we measured thirdhand smoke residue on walls, furniture, and in dust, the levels were comparable to what we find in homes of current active smokers. In another study of more than 200 apartments in multiunit housing, we found thirdhand smoke residue in each and every home we studied. This included several apartments of nonsmokers who had strict smoking bans and lived in their apartments for more than two years. In about 5% of these nonsmoker apartments, we found thirdhand smoke at levels comparable to smoker rooms in hotels.  
Because thirdhand smoke becomes embedded in carpets, furniture, and walls, it is very difficult to remove it once it has built up.  If a thirdhand smoke reservoir is superficial, washing, wiping, vacuuming, and airing out a room or car might be enough. When a reservoir is deep, wiping and washing may provide temporary relief, but thirdhand smoke chemical will soon come back out form their reservoirs.  In that case, carpets, furniture, cabinet, and even wallboards may have to be replaced to get rid of thirdhand smoke. This problem is well understood in the real estate and hospitality industries, among used car dealers, and in the cleaning and remediation business. Cleaning up a heavily polluted home or car can be a very expensive proposition.
There is another important issue I want to mention when it comes to cleaning up THS.  Humans are very sensitive to unpleasant odors, which is why car dealers, real estate agents, and the hospitality industry try to mask unpleasant odors with fragrances.  But adding a pleasant fragrance does not make a toxic chemical go away. These masking strategies simply try to fool our noses, and in fact can make things even worse. If someone has asthma, adding fragrances to air that already carries toxic thirdhand smoke chemicals will make things just worse.  
When customers complain about unpleasant odor, business sometimes offer air purifiers or odor eaters, claiming to remove pollutants.  These approaches work by using a chemical reaction to change an odorant chemical compound into an odorless chemical compound. The scientific literature shows that this approach is highly problematic because oxidants, such as ozone, are strong lung irritants and need to be treated very carefully.  Depending on the type and amount of pollutants, the reaction process with ozone may take months or years to have an impact and it may affect some pollutants not at all. But even if used carefully, the chemicals with which ozone reacts can form a variety of harmful by-product and new secondary pollutant.  We advise against using ozone machines and similar air purifiers because they can make a bad situation worse and are unlikely to be ineffective in environments that are highly polluted. Remember that just because we can no longer smell stale tobacco smoke does not mean that we are safe. In fact, the odorant chemical may have been converted into even more harmful odorless compounds.

Mr. Martin:
What about electronic cigarettes and vaping? Do they produce thirdhand smoke?

Dr. Matt:
Yes, electronic cigarettes and vaping leave behind residue from their emissions and therefore produce thirdhand smoke.  However, because the emission from regular cigarettes and electronic cigarettes differ, the composition of thirdhand smoke from regular cigarettes and electronic cigarettes will also differ.  Both forms of thirdhand smoke residue include nicotine and other tobacco specific compounds such as 3 EP, formaldehyde, acrolein, and benzene. Overall, the concentration and rate of thirdhand smoke build up from electronic cigarettes is significantly lower than that from conventional cigarettes.  While this suggests less polluted indoor environment and a lower health risk compared to conventional cigarettes, the negative impacts of electronic cigarettes are far from trivial and are not yet well understood. One important reason why we do not yet fully understand the consequence of electronic cigarettes is that the devices and how they are used can differ in many ways, including the type of e-liquid, the temperature at which the e-liquid is heated, and how well a device is maintained.  All three factors have a significant impact on the profile of toxic compounds that are produced by electronic cigarettes. 

Mr. Martin:
What kinds of things can people do to limit exposure to thirdhand smoke? In particular, what can parents do to protect their children? 

Dr. Matt:
Because it is difficult and expensive to clean up thirdhand smoke, the focus has to be on prevention.  Whenever possible, stay in a location with a comprehensive and well-implemented 100% smoking ban.  

Whenever you rent a new apartment, buy a home, make reservations for a hotel room or rental car, or buy a used car, make sure to ask about their smoking policies.  Read the smoking policies and confirm that it includes e- cigarette. Make sure that smoking is prohibited everywhere in the building and there are no loopholes such as grand-fathering clauses allowing some resident to continue to smoke.  Ask what happens if someone violates the policy and what you should do when you notice someone smoking. Look for evidence of tobacco use such as litter, burn-marks, odor. See if there is clearly visible signage reminding users, owners, and guests that this is a 100% smoke-free environment.  Find out as much as you can if previous owners or renters were smokers. If you are not convinced that a home, or hotel room is non-smoking, request another.
Finally, reinforce a company’s good policy choices. Thank the management and staff for having strong smoke-free policies, and post a positive review on social media.

Mr. Martin:
Where is thirdhand smoke research headed? What do we still need to learn?

Dr. Matt:
First I would say we need population studies of the prevalence of thirdhand smoke pollution and exposure and how this may differ between mild-weather and cold-weather climates where outdoor smoking is less of an option.
Also, the contribution of thirdhand smoke to the overall harm caused by tobacco products and the contribution of thirdhand smoke to health disparities in low-income, low-education. We need to identify specific markers that distinguish secondhand smoke from thirdhand smoke exposure, and the chemical and biological mechanism by which thirdhand smoke affects the immune system, respiratory and cardiovascular health.
In addition, low-cost DIY test kits that can be used by laypersons to determine if their car, apartment, business, hotel room, used furniture, hand-me down toys, antiques are polluted with thirdhand smoke and we need cost-effective cleaning, remediation methods. Finally, educating the public, health care providers, apartment managers, real estate agents, rental car companies, hotel managers, policy makers about thirdhand smoke.  I encourage your listeners to visit for information.

Mr. Martin:
Thank you speaking with us, Dr. Georg Matt!

Dr. Matt:
You are most welcome.

Mr. Martin:
And thank you all for listening. The Bytes podcast is a production of the Rover Tobacco Control Library, which is a funded project of the California Tobacco Control Program. We’re working on a series of episodes on the statewide projects of the CTCP as well new research and emerging issues in tobacco control.
If you’ve got an idea for a podcast, or if you have thoughts or suggestions you’d like to share, please send me a message a
I’m Joseph Martin, and this has been Bytes.

The original podcast was recorded by UC Davis Rover Library.

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