Popcorn lung sounds like it might not be so bad, but don’t let the name fool you.

In the microwave popcorn industry, significant amounts of flavorings are often used to ensure the treat has a delicious and buttery flavor.  You may think that BMI is where we are headed with this, but in fact diacetyl is our concern today.  Diacetyl occurs naturally in alcoholic beverages, dairy products, and coffee, and is the chemical used to give microwave popcorn a buttery flavor.

Diacetyl exposure first came to public attention when eight former employees of the Gilster-Mary Lee popcorn plant in Missouri developed bronchiolitis obliterans.

Bronchiolitis obliterans is an inflammatory obstruction of the lung’s tiniest airways (see above) and can lead to respiratory failure.  Bronchiolitis obliterans is a mouthful (no pun intended), and was therefore coined the charming “popcorn lung.”

In 2000, the Missouri Department of Health called in NIOSH to recommend safety measures in the case of the eight workers exposed to diacetyl.

Diacetyl has been shown to cause epithelial damage that can lead to obliterative bronchiolitis in workers exposed to it during the production of microwave popcorn, flavorings, and other foods such as cookie dough and pet food.  (The related chemical, 2,3-pentanedione, a diacetyl substitute, has proved no less hazardous.)

In 2007 a Denver man was awarded $7.2 million in a
lawsuit against a popcorn maker and a grocery store
after getting popcorn lung from microwave popcorn.
He had eaten 2 bags of popcorn a day for 10 years.
(Fulton 2012)

Now that we’ve ruined home movie night, let’s expand the scope of “popcorn lung” by looking at another source of diacetyl: coffee.  Most American adults (54%) drink coffee every day*, and a study published in the August 2015 Toxicology Reports by Gaffney et al found high levels of diacetyl and 2,3-pentanedione in the air at a small coffee roasting plant.

They conducted sampling of three roasting batches and three grinding batches at varying distances from a commercial roaster and grinder.  Interestingly, the diketone concentrations were higher during grinding than those measured during roasting.

The results indicate that airborne concentrations of naturally occurring diacetyl and 2,3-pentanedione are associated with unflavored coffee processing.  These results are similar to the concentrations that have been measured in food flavoring facilities (like microwave popcorn factories), and are likely to exceed the recommended short-term occupational exposure limits.  In this study the analyses of exposure were found to be lower than concentrations that would cause responses in the human respiratory tract, but when compared with the exposure limits suggested by NIOSH for diacetyl in popcorn, are well above safe standards.

Pierce et al (2015), simulating a cafe setting, found the potential for risk to customers who stay in coffee shops for hours.  Samples were collected while a barista ground whole coffee beans, and brewed cups of coffee for customers.  The mean estimated exposures for the barista exceeded recommended eight hour occupational exposure limits for diacetyl and were comparable to measurements collected in various food and beverage production facilities.

Based on area sampling, the parts per million exceedances of the recommended occupational exposure limit may also occur for coffee shop workers who do not personally prepare coffee, but work near the process (and the customers socializing or lingering on their laptops).

Duling et al (2016) found bronchiolitis obliterans in five former coffee processing employees at a single workplace.  This prompted a NIOSH exposure study of current workers.  Exposure characterization was performed by: observing work processes, assessing the ventilation system and pressure relationships, analyzing headspace of flavoring samples, collecting and analyzing personal breathing zone, and area air samples by work area and job title.  Workers in the unflavored coffee grinding/packaging area had the highest mean diacetyl exposures, and 2,3-pentanedione exposures were highest in the flavoring room.

In honor of our apparent aim to poop on your party, keep an eye out for the roll that diacetyl plays not only in popcorn and coffee (and cookie dough and dog food), but also in the ever-controversial e-cig industry (Dr. Schumpert has a whole soap box about this one, so stay tuned).

A quick stop for a cuppa, a handful of buttery popcorn from a bag, or the passing whiff of an e-cig will not (I repeat, NOT) make your lungs look like this:

But, next time you plan to spend the day in a coffee shop, we recommend you find a well-ventilated seat by the door.


Diacetyl is an organic compound with the chemical formula (CH₃CO)₂. It is a yellow/green liquid with an intensely buttery flavor.

Diketone is a molecule containing two ketone groups. The most simple diketone is diacetyl.

Epithelium is one of the four basic types of animal tissue.  These tissues line the cavities and surfaces of blood vessels and organs throughout the body (including the lungs).


·        Jennifer S. Piercea, Anders Abelmann, Jason T. Lotter, Chris Comerford, Kara Keeton, Brent L. Finley. Toxicology Reports 2 (2015) 1200–1208.

·        Shannon H. Gaffney, Anders Abelmann, Jennifer S. Pierce, Meghan E. Glynn, John L. Henshaw, Lauren A. McCarthy, Jason T. Lotter, Monty Liong, Brent L. Finley.  Toxicology Reports 2 (2015) 1171–1181.

·        Matthew G. Duling, Ryan F. LeBouf, Jean M. Cox-Ganser, Kathleen Kreiss, Stephen B. Martin Jr., Rachel L. Bailey.  Journal of Occupational and Environmental Hygiene (2016).

·        Image: http://www.toxipedia.org/display/toxipedia/Diacetyl

·        *http://www.hsph.harvard.edu/news/multimedia-article/facts

·        http://www.npr.org/sections/thesalt/2012/09/20/161489994/man-wins-7-million-in-suit-claiming-microwave-popcorn-caused-lung-disease






“Federal court permits employees to sue Givaudan for diacetyl exposure.  The Seventh Circuit Court of Appeals has ruled that the manufacturer of diacetyl is not insulated from a lawsuit by exposed workers merely because their employer failed to warn them of the hazards of the substance.”  Read more…


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