At this point, handheld electronic vapes are a part of daily life for many. Not uncommonly, they are used indoors and around others, with many assuming the devices are less harmful than cigarettes. 

But scientists now warn that pollution from one of these devices could expose nearby people to a mix of complex reactive chemicals. One new study even suggests that emissions from the devices can change after lingering in indoor air. 

What's happening?

According to a study published in December 2025 in Environmental Science and Technology, aerosols released from e-cigarettes can become more chemically reactive after sitting in indoor air. 

The research team noted that previous findings have indicated that terpene flavoring chemicals in vape pollution can react with indoor ozone to form organic hydroperoxides. According to the study, these peroxides can break down into radicals when they dissolve in wet environments. 

The researchers also found that redox-active metals released by vaping can become concentrated in ultrafine particles, leading to increased radical formation through what they described as "Fenton-like reactions." The co-authors found that this process creates a "chemical cocktail" of particles small enough to be inhaled straight into the lungs. 

"Our study reveals that the chemical cocktail of metal nanoparticles and reactive peroxides in aged e-cigarette aerosols creates a unique profile of respiratory health risks," co-author Ying-Hsuan Lin told Newsweek in a statement. 

The study specifically looked at what this could mean for people exposed indirectly, including bystanders in indoor spaces. 

Why is clean air important?

Reactive oxygen species are known to damage cells and tissues. According to the study's co-authors, the radicals formed from aged vape pollution may increase oxidative stress when inhaled, particularly after particles reach the more moist regions of the respiratory system. 

Together, the metals (including arsenic, tin, and lead) and peroxides in the ultrafine particles can make vape smoke more potent than previously recognized. 

Meanwhile, exposure to vape emissions has been a public health concern since before this study, leading to numerous vape bans. Newsweek reported that scientists warned that breathing secondhand vape pollution may pose health risks for non-users, and the impact accumulates with repeated exposure. 

What can be done about these risks?

On a policy level, the researchers recommend treating vaping aerosols similarly to secondhand smoke. 

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For individuals, reducing indoor exposure to vape pollution is among the first steps to lowering risk. Additionally, talking to friends and family about these risks and even reaching out to local officials to increase awareness could be effective and practical ways to make a difference. 

Legislation to curb the use of vapes has been proposed and implemented across the United States and around the world. Proponents of regulating the devices have expressed concern about youth health in particular and about the growing litter problem driven predominantly by disposable vapes, which contain plastics and lithium batteries.

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