August 20, 2018

  • Prolonged exposure to high levels of heated diacetyl in microwave popcorn factories has been linked to the irreversible lung damage known as “popcorn lung”.
  • Diacetyl has been found to be present in some vaping liquids, at levels ranging from unmeasurable to as high of 239 µg (micrograms) per e-cigarette, with almost all measuring below 30 µg.
  • There is no known link between e-cigarettes and popcorn lung.


Based on research involving a small sampling of vaping product, we have been hearing about the potential of vaping to cause “popcorn lung” since December 2015. As this was again featured on Facebook in mid-November 2017, it’s time to separate the facts from the speculation.

Limited Product Testing

This research paper reports that over 7,000 vaping products were on the market in 2015, but the researchers only tested a small sampling – 51 different e-cigarettes manufactured by nine “leading brands” with flavors that the researchers “deemed were appealing to youth.”

The research examined e-cigarettes as well as vaping fluid sold separately, which accounts for a large portion of the market. They only tested product from well known manufacturers, which are not identified, ignoring the vast majority of the vaping industry.

The vaping industry can be divided into two groups: Those that sell assembled, ready-to-use e-cigarettes and those that sell vaping juice and vaping hardware separately. For the most part, the assembled e-cigarettes are sold with as much information on ingredients as your typical cigarette – in other words, none at all. Let the buyer beware, because you have as little idea what may be in there as in traditional tobacco cigarettes.

The rest of the vaping industry is more interested in producing a high quality product with known ingredients, and in many cases there isn’t any nicotine at all. The vast majority of vaping liquid contains low amounts of nicotine, although liquids containing high nicotine are available – usually to help wean smokers from cigarettes as they reduce the nicotine level of their vaping fluid.

Nicotine is toxic, and its presence in cigarettes and some vaping liquids is a known danger. That said, vaping has become a common path away from cigarettes and also from nicotine for a majority of users. It is also generally considered far safer than tobacco cigarettes.

The Chemicals Examined

This study looks at the presence of diacetyl, 2,3-pentanedione (acetyl propionyl), and acetoin in the 51 fluids tested. Of the 51, 39 contained some level of diacetyl, the chemical responsible for the “popcorn lung” mentioned in most of the headlines. Levels ranged from detectable but too low to measure to 239 µg per e-cigarette.

2,3-Pentanedione was detected in 23 flavors, while acetoin was found in 46. 2,3-Pentanedione levels ranged from present to 64 µg per e-cigarette and acetoin from present to 529 µg per e-cigarette.

At the time this study was done, only three papers had been published on the flavoring chemicals used in e-cigarettes. The researchers did not study the level of nicotine present in the e-cigarettes they tested.

Popcorn Lung and Buttery Flavoring

Popcorn lung was first found among workers involved in manufacturing microwave popcorn, and it was soon associated with the use of diacetyl and other chemicals used in butter flavoring. Prior to this, diacetyl was generally considered safe for consumption – but it had not been tested as an inhalant. (Some vaping companies use 2,3-Pentanedione for buttery flavoring, a chemical the FDA generally recognized as safe.)

This research addresses the lack of transparency by some e-cigarette manufacturers about ingredients, and we should be grateful to the researchers for taking a step that a segment of the vaping industry didn’t want to deal with.

We can also be grateful that the researchers included a table (see Appendix) showing the 51 flavors they tested as well as the levels of diacetyl, 2,3-pentanedione, and acetoin in each flavor tested, making it easy to review their findings. The table does not list brands or not whether an assembled e-cigarette was being tested or a separate vaping liquid.

How Dangerous Are These Chemicals?

Thanks to microwave popcorn, heated diacetyl is now known to cause lung problems when inhaled for an extended period of time. From the research paper:

The Flavoring and Extract Manufacturers Association of the United States released a report in April 2012 on respiratory health and safety in the food-manufacturing workplace that highlighted the potential risks associated with inhaling diacetyl and a long list of other food flavoring chemicals.

FEMA and the Flavoring and Extract Manufacturers Association of the United States recommend use of the following notice with chemicals known to present a danger:

WARNING – This flavor may pose an inhalation hazard if improperly handled. Please contact your workplace safety officer before opening and handling, and read the MSDS. Handling of this flavor that results in inhalation of fumes, especially if the flavor is heated, may cause severe adverse health effects.

At the time of publication in late 2015, there were industry standards covering inhalation exposure to diacetyl and 2,3-pentanedione in the workplace, but no standards had been established for the general public or for children. In other words, as of December 2015, nobody knew what was a safe level of exposure and what was a dangerous level outside of the manufacturing plant. Until that changes, it is impossible to set meaningful exposure limits for those using e-cigarettes. Vaping outdoors – or even indoors – is a very different environment than a factory, so occupational levels are meaningless for those receiving far less exposure than they would if they worked manufacturing microwave popcorn or vaping fluid.

One further tidbit: Tobacco cigarettes contain 10 to 100 times as much diacetyl and 2,3-pentanedione as vaping, something not mentioned in this research paper. If anything, this shows vaping to be significantly less likely to produce popcorn lung than tobacco.

Our advice: If you work in a microwave popcorn factory or other facility where you are exposed to heated diacetyl regularly, you should probably not vape and certainly not smoke, as this will only increase your risk of popcorn lung.

Sensational Headlines

For better or worse, sensational headlines are a powerful way to get people to click on a link to an article on the internet, which in turn is a great way for a website to display numerous ads in hopes of monetizing the interest in whatever topic it happens to be. These headlines are called clickbait and their publishers are click farms, existing only to make a profit based on the sheer quantity of people coming to their websites.

Here are some of the more sensational headlines about this research paper that have been published in the past two years:

More accurately: A chemical found in some e-cigs has been linked to popcorn lung, but it is found in very low levels in most e-cigs when it is present.

Some less sensational (more responsible) headlines:


As with most things in life, vaping has some level of risk, but until that risk can be quantified, it is impossible to set a reasonable exposure level. We are indebted to the researchers who produced this paper for the time and energy invested in determining how prevalent three specific chemicals were in a sampling of vaping products. This is a good beginning to developing the knowledge necessary to make educated decisions.

At this time there is no known link between vaping and developing popcorn lung, although that may be a distinct possibility depending on the level of diacetyl present in the vaping liquid selected and how frequently one vapes. As the researchers conclude, more research needs to be done – a lot more.

Until then, it is good to know that Public Health England considers vaping 95% less dangerous than smoking cigarettes.


Appendix: The Test Results

This table is adapted from a high resolution 5.8 MB TIFF image included in the original research paper. It has been optimized for use on the web and faster downloading but not otherwise modified.

Entries marked <LOQ are detectable as present but below the ability for the lab to quantify, while those marked <LOD means the chemical was not present or was below the detectable level.

Of the 51 flavors tested, 21 had unmeasurable or undetectable levels of diacetyl, 32 of 2,3-pentanedione, and 11 of acetoin. A total of seven had unmeasurable or undetectable levels of all three chemicals.

As always, feel free to comment in our Facebook group or email us if you have any questions or concerns about the content of this article.

Keywords: #popcornlung #diacetyl #vaping #e-cigarette #vapehealth #vapemyths

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