(CNN) Adults living with children are more likely to vape than those without, putting kids at risk for what the authors of a new study describe as "the 'new' secondhand smoke."
"These children are potentially exposed to secondhand aerosols, an amalgam of compounds with yet unknown health consequences," the researchers wrote.
According to the research letter, published Monday in the journal JAMA Pediatrics, 4.9% of American adults living with someone 18 or under reported using e-cigarettes. That's versus 4.2% of adults living in households without children according to study author Jenny L. Carwile, an epidemiologist at Maine Medical Center, who also pointed out that these adults tend to be older.
The authors say this could reflect "the relatively young age of e-cigarette users" and the perception that vaping is safer than smoking combustible cigarettes.
These rates changed from place to place, from 2.3% in the District of Columbia to 7.7% in Oklahoma.
The data came from a nationally representative phone survey in 2016 and 2017. However, the researchers could not determine how much adults tended to vape in kids' presence or additional secondhand exposure from other people, such as siblings and peers.
Previous research has suggested that teens who live with someone who vapes are more likely to pick up the habit themselves.
The prevalence of vaping among adults isn't very different from that of middle schoolers, which was 4.9% in 2018, according to a report by the US Centers for Disease Control and Prevention.
In comparison, 20.8% of high schoolers are current e-cig users, according to the CDC report. Vaping increased nearly 80% among high schoolers and 50% among middle schoolers from the year before.
The authors of the new paper point out that, in addition to inhaling the aerosol secondhand, there's a risk that certain chemicals in e-liquids, namely nicotine, can be absorbed through the skin or even ingested. Experts warn of this particular risk among young children.
Dr. Robert Jackler, founder of Stanford Research into the Impact of Tobacco Advertising, previously told CNN that some e-liquids with high nicotine concentrations represent "a huge poisoning risk." Some bottles, many with sweet flavors, lack childproof caps and contain enough nicotine to kill an entire preschool class, he said.
With the rise in e-cig popularity has come a rise in calls to poison control centers, he added.