Jan. 13, 2011 -- Thirdhand smoke, the nicotine residue that is left behind on furniture, walls, and carpeting after a cigarette has been smoked in a room, can become airborne a second time, a new study shows.
The resulting particulates, a toxic mix of ozone and nicotine, are so small that they can easily penetrate into the deepest parts of the lung, and over time, scientists say, could contribute to breathing problems like asthma or even cancer.
“Quantitatively, exposure via secondhand smoke is much greater and a more likely concern with regards to health,” says study researcher Yael Dubowski, PhD, a senior lecturer at Technion-Israel Institute of Technology in Haifa, Israel. “However, exposure to harmful compounds via thirdhand smoke and thirdhand smoke transformations is an additional source for skin and lung exposure.”
What’s more, Dubowski says, because ozone can continue to pull nicotine off surfaces and back into the air for months, exposure to thirdhand smoke may continue long after smoking in the area has ceased.
A Third Way to Be Exposed to Cigarette Smoke
Only recently have scientists have begun to measure and understand the dangers of exposure to thirdhand smoke.
“There’s nicotine in tobacco smoke, obviously. The portion of that nicotine that’s not absorbed by the human body, that nicotine goes someplace, and one of the places it goes is that it sticks on the surfaces of the room that you’re in,” says James F. Pankow, PhD, professor of chemistry and civil and environmental engineering at Portland State University in Oregon.
Previous research has shown that thirdhand smoke can rub off onto skin and even be ingested if food is eaten that’s been exposed to smoke. It was also shown that dust could carry thirdhand smoke to the lungs.
The new study, which is published in the journal Environmental Science & Technology, shows that nicotine residues can interact with other indoor air pollutants and become airborne again.
“Nicotine can come back off of that surface to react with ozone,” says Pankow, “It forms particles.”
Those particles, known as secondary organic aerosols, are so small that they may be inhaled deeply into the lungs, where they are hard for the body to clear.
Studying Cigarette Residues
For the study, Dubowski and her team impregnated three different kinds of materials, cellulose (a proxy for plant-based building materials like wood), paper, and cotton, with nicotine and exposed them to ozone under dry and humid conditions.
They were able to see that nicotine remained on the surfaces to be wiped off onto skin or clothing.
They were also able to measure, however, that nicotine could “desorb” off a surface back into the air where it might be inhaled on its own or react with other indoor air pollutants like ozone to form particulates.
The researchers also found that humid conditions appeared to be somewhat protective against exposure to the products of thirdhand smoke.
“This may not be very significant under normal indoor conditions where relative humidity is governed by comfort and kept around 60%,” says Dubowski. “However, in airplanes, where relative humidity is particularly low, less than 20%, and ozone concentrations can reach higher than 100 parts per billion, the potential for exposure to products of thirdhand smoke products may be greater.”