There is a controversy brewing in the e-cigarette world that centers around the seemingly innocuous topic of buttery flavored e-liquids. While the average person may have never even heard of diacetyl, it's been on the lips—literally and figuratively—of vapers for the last seven years, and it's landed at least one high-end e-liquid company in some hot water.
"Everyone knew about diacetyl," Russ Wishtart, host of the vaping podcast Click Bang! who has done a number of episodes on the topic, told me.
Diacetyl (DA) is a chemical used in food flavoring. It infuses food with a creamy, buttery taste, so it's usually found in products that have butter, cheese, or caramel flavors. Diacetyl and acetyl propionyl (AP)—a kind of "sister chemical" that is nearly identical to DA—are also found in many flavored vaping liquids, especially those with a "dessert" flavor (think butterscotch, vanilla, or caramel).
When you eat or drink something that contains diacetyl, it's considered harmless—it even occurs naturally in some milk products, and in a few wines and beers. But inhaling it is a different story, and can have serious health risks. Because of this, vapers have been concerned about the presence of DA and AP in e-juices for awhile now, and many trade organizations have limits on the levels of DA and AP that can be present in the liquids they stock.
Over the last few years, manufacturers and vendors have been testing their products for these chemicals, sharing the results with consumers, and altering recipes to eliminate them. That process really ramped up towards the end of last year when researchers published a paper in Nicotine and Tobacco Research that found, of the 159 sweet and creamy flavored e-liquids tested, 74 percent had DA, AP, or both.
"They were telling people that they had tested it and it was free of diacetyl"
"The whole issue didn't exist before we published our study," said Konstantinos Farsalinos, a researcher at the Onassis Cardiac Surgery Center in Greece, and lead author of the study. "There were discussions in e-cigarette consumer forums—vapers forums—on the internet, but there was no discussion in the scientific community. So we learned a lot from vapers."
In the wake of the study, many e-liquid companies scrambled to test their products and ease customers' minds. But at least one company has now come under fire for not revealing the high levels of AP in some of its liquids, even though it knew about these levels for months.
Five Pawns is a high-end e-liquid manufacturer based in California. The company commissioned a lab to test its liquids as early as May of 2014. But the company didn't release any results publicly until June of this year, after a UK-based e-cigarette retailer published its own lab results on Five Pawns products. Five Pawns ordered those results taken down via a cease and desist order, and wrote on its website that those tests were "fraudulent," publishing its own lab results instead.
But even Five Pawns' own tests showed alarmingly high rates of AP in some liquids. In Farsalinos's study, the researchers converted National Institute for Occupational Safety and Health limits on diacetyl inhalation to determine an estimated safe amount to inhale through vaping. For AP, that limit was 137 micrograms per day. One of Five Pawns' flavors had AP levels of 627.7 micrograms per millilitre. I couldn't find any formal studies on the volume of e-liquid vapers use per day, but an online survey of users by E-Cigarette Forum found the plurality of respondents (22.6 percent) vape four to five millilitres per day. A majority of respondents (59.8 percent) said they vape between two and six millilitres per day.
What really bothered Wishtart and others in the vaping community wasn't the high levels, but that Five Pawns had spent the past few months assuring vendors and customers that its products didn't contain any DA or AP at all. Five Pawns declined to be interviewed for this story.
"They were telling people who were purchasing wholesale from them and importing the product to other countries that they had tested it and it was free of diacetyl and acetyl propionyl," Kate Ackerman, a board member at the Electronic Cigarette Trade Association (ECTA) of Canada, told me over the phone.
After Five Pawns published its lab results, the ECTA had to alert members to pull some of the products from the shelves because they contained AP levels above the organization's limits. Anything with more than 100 micrograms per milliliter of AP can't be sold by ECTA members, which meant five Five Pawns liquids had to be taken off the market in Canada, while another three liquids required "disclosure labelling."
"Our decision with Five Pawns wasn't meant to be punitive. We were forced into a recall situation because we have no control over what they're doing," Ackerman told me. "Our guidelines were originally put in place right from the very beginning when we started as an organization back in 2012. They're updated whenever we receive new information from science and medical researchers."
The risks of inhaling DA were first discovered in the summer of 2000, when a handful of workers in a microwave popcorn plant in Missouri started getting diagnosed with a rare, severe, irreversible lung disease called bronchiolitis obliterans. Even non-smokers who worked at the plant were getting sick, and investigators soon discovered it was linked to inhaling diacetyl—which gave the popcorn that "real butter" taste—on a daily basis. Soon after, NIOSH, the research branch of the US Occupational Safety and Health Administration (OSHA), recommended guidelines for factories where DA and AP is used, to prevent workers from getting sick. But OSHA has yet to translate those recommendations into meaningful regulation.
But while there are regulations on diacetyl to keep workers safe, there are currently no regulations at all on e-cigarettes in the US, and that means DA and AP can be added to vaping liquids in the same levels as are allowed in food products. There hasn't been any research that shows the effects of inhaling e-cigarette liquids that contain DA or AP, but many manufacturers and consumers are concerned that it could have similarly dangerous risks.
"Diacetyl is a respiratory toxin, so when you breath it in, it irritates the lungs," said Jessica Barrington-Trimis, a researcher at the University of Southern California and the Tobacco Center of Regulatory Science. "That's not a problem if you're eating it because it doesn't get into the lungs at all."
Barrington-Trimis is currently conducting a study that compares the respiratory health of vapers who use unflavored e-cigarettes to those who prefer flavored varieties, and said more research is needed to understand the potential risks of these chemicals. But in the meantime, she doesn't see why manufacturers don't just err on the side of caution and avoid DA and AP altogether.
On Five Pawns' blog, the company wrote that it didn't intend on removing AP from its current recipes (though the company is cooking up some new flavors that will be DA and AP free). It also noted that there's a difference between inhaling DA all day in a factory and taking a few puffs from an e-cigarette, and that cigarettes contain both DA and AP, yet bronchiolitis obliterates isn't common.
But Barrington-Trimis—and others, including Wishtart and Farsalinos—wasn't sold.
"It's possible that inhaling through an e-cigarette could be even more damaging to the lungs than a factory setting, because they're designed to take that aerosol deep into your lungs," she said. "At the end of the day, they don't need to be using either one of these chemicals."
Correction 8/11/15: This story initially stated that NIOSHA had created guidelines for diacetyl exposure in US factories. While that is correct, we've clarified that section to explain that NIOSHA guidelines are just that, and only OSHA can create specific regulation to limit diacetyl exposure.