Those who are wary about the negative health effects of smoking, and even secondhand smoke, can do many things to avoid exposure to the toxic chemicals associated with tobacco smoke. A new study conducted by Drexel researchers, however, suggests that third-hand smoke — the chemical residue from tobacco smoke that sticks to clothes, furniture or other surfaces — may not be as easy to evade.
The research, published on May 9 in the scientific journal Science Advances, found that third-hand smoke can permeate the air and circulate through smoke-free buildings via their ventilation systems.
College of Engineering professor Peter DeCarlo, who co-authored the research with Michael Waring, said the discovery was an accidental finding. Initially, DeCarlo was working with Drexel graduate student Anita Avery on her doctoral thesis, which looked into how outdoor air particles change chemically when they’re brought into a ventilated, indoor space.
“When we wrote the proposal to get funding for our initial project, there was no mention of third-hand smoke,” said DeCarlo. “It took us by surprise finding this chemical signature of residual tobacco smoke [because] we didn’t see it outdoors, only in indoor environments.”
Upon detecting the toxins, the pair took a detour from their initial project and began monitoring the transport of particles from outdoors to an empty, non-smoking classroom. They then measured the composition of the particles inside using an aerosol mass spectrometer — an instrument used to detect pollutants and how much of them are present in the air we breathe.
After gathering a month’s worth of data, DeCarlo and Avery found that 29 percent of the classroom’s total air mass contained third-hand smoke. This could mean that the particles that we are breathing in indoor spaces contain some chemical residue, according to DeCarlo, who heads a research group in the Drexel Air Resources Research Laboratory..
Given that they performed the experiment in a room where no one has been permitted to light a cigarette in decades, DeCarlo explored other ways the tobacco smoke came indoors. Some factors included the third-hand smoke being absorbed from the clothing of outsiders to indoor surfaces, and entering through windows or cracks in buildings. Ventilation systems of buildings played a huge role in the transport of the toxins, DeCarlo said.
“By mechanically ventilating and recirculating air, we take what happens in one room and make it happen in other rooms,” he said. “It really only takes one room on the same ventilation system for this smoke residue to get everywhere.”
Erin Katz, a Drexel senior co-oping as a research assistant under DeCarlo, performed a similar experiment using e-cigarettes — vapes, particularly — to see if vape smoke behaved similarly to tobacco smoke. Her finding uncovered that, although vaping is a healthier alternative to tobacco smoking, vaping indoors also contributes to third-hand smoke.
“People vape inside all the time often thinking it’s not as bad because there’s no smell left over,” she said. “But it still contains nicotine, and it can go on to react to oxidants in the atmosphere and form residual nicotine byproducts.”
Third-hand smoke particles are elusive and reactive by nature; they look for new surfaces to attach themselves to, which explains how third-hand smoke can be found in unexpected places such as hotels, rental cars or shared work spaces, DeCarlo said.
Removing third-hand smoke particles from a contaminated room is no easy feat, DeCarlo found. According to him, the chemical residue can persist for months, or even years.
“If you move into a place that has been previously smoked, the recommendation is to remove all of the carpeting, all of the curtains and window fixtures, and paint all of the walls three times,” he said. “That way, you’ll cover up the residual smoke in the house.”
Cigarette smoking claims the lives of more than 480,000 people per year in the United States. Meanwhile, 41,000 people die annually from second-hand exposure, according to the Centers for Disease Control and Prevention.
As for the health risks of third-hand smoke, although it’s a new area of study that requires additional research, the exposure to the chemical residue can still be detrimental, DeCarlo said.
“From what I’ve seen from the health research that’s been done, a lot of the same issues associated with direct smoking is also seen for third-hand smoke exposure,” he said. “That includes increased prevalence of asthma, risk of lung cancer, growth restrictions and immunity problems.”
In any case, Katz, a chemistry major, hopes this study galvanizes experts from other science fields to look further into third-hand smoke and determine its health effects, she said.