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Filters provide a kind of handle for cigarette users who want to avoid burning their lips or fingers, wasting tobacco, or having to pull stray tobacco bits off their tongues.
Triacetin can make up as much as 10% of a filter, and its low volatility means it doesn't evaporate quickly at normal temperatures, so it could be a good indicator of long-term emissions from a butt, Poppendieck explained.
The question that Poppendieck and his team considered, therefore, was not the impact of filters on smokers themselves. Rather, they focused on emissions from discarded butts, which are largely just used filters.
"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, to remove some potential variables associated with the behavior of actual smokers.
Extinguished cigarettes 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.
Most of the chemicals from the extinguished butts were emitted in the first 24 hours, Poppendieck noted. However, nicotine and triacetin concentrations were still about 50% of the initial level 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 [second- 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.
Figuring out what to call these newly discovered and measured emissions has been challenging. In the lab, Poppendieck and his team refer to them loosely as "after smoke" or just butt emissions.
No matter what terminology is used, the research team wants people to know that the chemicals remain long after the cigarette goes out. People have been asked to not throw their cigarettes out car windows, because it takes years for the butts to degrade.
Poppendieck wants people to also know they can put used butts in sealable metal or glass jars with sand instead of leaving them out in the open.
"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." Source:
National Institute of Standards and Technology Journal reference:
Gong, M. et al . (2020) Measurement of chemical emission rates from cigarette butts into air. Indoor Air. doi.
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