May 21, 2024

Inhalation Exposure and Surface Contamination Concerns from E-Cigarettes

By Kay Bechtold

While researchers have learned much about e-cigarettes in recent years, “we still don’t know everything,” Cheri Marcham, PhD, CSP, CIH, CHMM, FAIHA, told AIHA Connect attendees on Monday morning. Marcham, who led the team that developed AIHA’s white paper on e-cigarettes in the indoor environment, joined fellow team member Evan Floyd, PhD, CIH, for a presentation on topics ranging from how e-cigarettes have evolved over time to related guidelines and legislation. Two issues covered by Marcham and Floyd may be of particular interest to industrial hygienists and occupational and environmental health and safety professionals: exposures related to the inhalation of e-cigarette ingredients, especially flavorings, as well as surface contamination in vape shops and adjacent spaces.

Studying e-cigarettes remains difficult because there are now several different generations of the devices, though “they’re all generally the same in some sense,” Marcham explained: each one has a battery, a cartridge that holds the e-liquid or e-juice, and a heating element that heats the e-juice, which is what makes the vapor. Flavorings, additives, and additional potential exposures—for example, Floyd said, metals leaching out of the heating elements of e-cigarettes—present further challenges when it comes to studying their effects on vapers and those around them.

The e-liquid or e-juice in e-cigarettes has three main components: propylene glycol and vegetable glycerin, nicotine, and flavorings. Propylene glycol is often used to create theatrical fog for stage productions and concerts. Marcham pointed to evidence that people who are exposed to theatrical fog on a regular basis can develop health problems including asthma, decreased lung function, and respiratory irritation. “Compare that to intentionally inhaling it 16 hours a day” from an e-cigarette, she said. And heating or pyrolysis of glycerin can cause the chemicals formaldehyde, acrolein, and acetaldehyde to form in e-cigarette vapor, Marcham warned.

Formaldehyde is a known human carcinogen, and airborne concentrations of formaldehyde in an indoor environment where there’s uncontrolled vaping can cause exposures above the NIOSH recommended exposure limit of 16 parts per billion, Marcham said. For instance, during a NIOSH health hazard evaluation of a vape shop, the airborne concentration of formaldehyde was found to be as high as 31 ppb. Acrolein can damage the lining of the lungs, and acetaldehyde, a probable human carcinogen, can irritate the eyes, skin, and respiratory tract. Also found in e-juice is nicotine, which is known to cause numerous adverse health effects, and flavorings. Marcham estimated that more than 20,000 different e-cigarette flavors could be available on the market, ranging from fruit and candy flavors to ones that taste like bacon.

While the U.S. Food and Drug Administration considers some flavorings “generally recognized as safe” as food additives, Marcham cautions that GRAS substances and their thermal degradation products have not been evaluated for inhalation toxicity. One substance used in artificial butter flavoring, diacetyl, is considered GRAS, but it’s now known that aerosolized exposures to the chemical can cause the severe, irreversible lung disease bronchiolitis obliterans, or popcorn lung. 2,3-Pentanedione, which is used in some cases as a substitute for diacetyl, is also associated with respiratory disease when inhaled, Marcham noted, highlighting research that found diacetyl and 2,3-pentanedione in approximately 75 percent of flavored e-cigarettes.

Marcham also outlined her concerns related to diacetyl in the cannabis industry, which is relevant because most of the legal cannabis that is grown and produced is extracted for edibles or vaping. A NIOSH health hazard evaluation (PDF) at a cannabis grow and harvesting facility caught her attention because diacetyl was identified in screening air samples. Marcham’s theory is that diacetyl may be naturally present in cannabis facilities, similar to how the substance is naturally produced when coffee beans are roasted.

Other flavoring chemicals of concern include benzaldehyde, a substance used in cherry flavoring that has been shown to be cytotoxic and genotoxic to cell cultures; vanillin, cinnamaldehyde, and menthol, which are harmful to the endothelium; and ethyl maltol, a cytotoxic substance used to create flavors like cotton candy. Marcham also explained concerns related to flavoring emissions. For example, acrolein and formaldehyde emissions from flavored e-liquids are higher than those without flavoring.

Floyd went on to describe further potential exposures that stem from the heating elements of e-cigarettes, particularly popular disposable ones. He said that aerosols from these e-cigarettes have been found to contain at least 35 different elements or metals—many of which are not found in traditional cigarette smoke. With e-cigarettes, vapers may be exposed to elements including aluminum, manganese, and antimony.

It’s likely no surprise that a NIOSH health hazard evaluation in a vape shop where employees vaped throughout the day turned up detectable levels of nicotine, formaldehyde, diacetyl, and acetaldehyde in airborne samples, Floyd continued. Agency staff also found several metals, including tin, lead, nickel, and chromium, in surface samples taken in the vape shop.

“That makes sense,” Floyd explained. “Metals don’t evaporate and eventually settle onto surfaces.”

But research Floyd previously presented at AIHA’s annual conference showed that e-cigarette aerosols can spread through HVAC systems to adjacent parts of a building. This is a concern since many vape shops are located in strip malls or shopping centers where businesses and other establishments are adjacent to one another. Researchers found nicotine contamination on surfaces in shops adjacent to vape shops, while levels on surfaces in the vape shops themselves were lower than expected, which Floyd attributed to vape shops’ aggressive cleaning regimens. Display cabinets in adjacent shops were not cleaned as frequently, resulting in elevated nicotine contamination, he explained.

AIHA’s white paper on electronic cigarettes was first published in 2014 and was updated in 2018. The third version of the document is set to become available later this year; Marcham estimated July 2024. Individuals who are interested in being notified when the updated white paper is available can submit their contact information via the AIHA website.

Kay Bechtold is managing editor of The Synergist.

Read more coverage of AIHA Connect 2024.

For Further Reading

AIHA: “Electronic Cigarettes in the Indoor Environment” (PDF, 2018).

NIOSH: "Evaluation of a Medicinal Cannabis Manufacturing Facility with an Indoor and Outdoor Grow Operation" (PDF, 2019).

The Synergist: “Electronic Cigarettes and the IH” (May 2019).

The Synergist: “E-Cigarette Use Among Adult U.S. Workers” (May 2021).

The Synergist: “Outbreak of Lung Disease Associated with E-Cigarette Use” (October 2019).