Researchers at the National Institute of Standards and Technology have found that cigarette butts—the kind that litter our roads, sidewalks, and beaches—emit toxic chemicals into the air for days after the butt is extinguished. Old cigarette butts are not just litter. As a form of thirdhand smoke, the emissions from cigarette butts can expose non-smokers to toxic chemicals after smoking has stopped.

January 29, 2020

By: The National Institute of Standards and Technology

Cigarette butts pile up in parks, beaches, streets and bus stops, places where all types of littering are frowned upon. It is estimated that more than five trillion butts are generated by smokers worldwide each year. Concern about the environmental impact of this litter has prompted studies of how they cigarette butts affect water and wildlife habitats. So far, almost no one has studied the airborne emissions coming off these tiny bits of trash.

When Dustin Poppendieck was asked to evaluate them, he was skeptical. As a measurement scientist at the National Institute of Standards and Technology he realized there was no standard way of analyzing the amounts of chemicals swirling in the air around cigarettes hours and days after they had been put out. He was intrigued, but he also thought there might not be enough chemicals present to make the measurements meaningful.

What his team found, however, was that a used butt—one that is cold to the touch—can give off in one day up to 14% of the nicotine that an actively burning cigarette emits.

“I was absolutely surprised,” said Poppendieck. “The numbers are significant and could have important impacts when butts are disposed of indoors or in cars.” The measurements were performed under an agreement with the Food and Drug Administration as part of its analysis of the overall impact of cigarette smoking on people’s lives.

For a long time, most of the health impacts of smoking were misunderstood and often underestimated, in part because the emissions of cigarettes were not fully studied. Over the last 50 years, studies have improved our understanding of the health impacts of tobacco. We now know a lot about how cigarette smoking affects smokers’ own bodies as they inhale and exhale, referred to as mainstream smoking. We also know a lot about the health effects of secondhand smoke, which is the emissions from the end of a cigarette, pipe or cigar, and the smoke that is exhaled by smokers.

More recently, research has also examined thirdhand exposure, which comes from the chemical residue that stays on surfaces such as walls, furniture, hair, clothing and toys after a cigarette has been extinguished. Like mainstream smoking and secondhand smoke, thirdhand exposure can increase the risk of cancers and cause numerous other health problems, especially in the still-developing bodies and brains of infants and children.

Poppendieck’s team measured eight of the hundreds of chemicals typically emitted from cigarettes, including four that are on the FDA list of harmful and potentially harmful constituents. The overall goal of the study was to measure the emissions from cigarette butts and discover what happens to those emissions when the butts are left in different environments.

“If you have ever sat on a park bench when somebody next to you smoked, then they got up and left their cigarette butt behind, that odor you were smelling is indicative of what we are trying to capture and measure,” Poppendieck said. “Anyone with a good sense of smell knows it’s there.”

The team had to “smoke” over 2,100 cigarettes, although the scientists didn’t actually light up and inhale. Instead, Poppendieck’s team built a “smoking machine” that uses robotic movements to simulate what humans do when they light up. The machine was made to move air through each cigarette in the same way.

Once the cigarettes were “smoked”, the cigarettes butts were placed in a walk-in, stainless steel chamber in order to characterize airborne emissions. The team also tried to determine if environmental differences in temperature, humidity and saturation in water would change those emission rates.

They found that most of the chemicals from the cigarette butts were emitted in the first 24 hours, Poppendieck noted. However, about 50% of the nicotine and triacetin was still present five days later. The team also found that butts emitted these chemicals at higher rates when the air temperature was higher.

“The nicotine coming from a butt over seven days could be comparable to the nicotine emitted from mainstream and sidestream [secondhand or thirdhand] smoke during active smoking,” Poppendieck said. This means if you don’t empty an ashtray in your home for a week, the amount of nicotine exposure to nonsmokers could be double current estimates.

“You might think that by never smoking in your car when kids are present, you are protecting the nonsmokers or children around you,” Poppendieck said. “But if the ashtray in your hot car is full of butts that are emitting these chemicals, exposure is happening.”

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Image credit: National Institute of Standards and Technology