Is microwave popcorn toxic?

© Photographer: Graça Victoria

Popcorn is one of the world's most popular confections, frequently enjoyed in ballparks, movie theaters and at home. Popcorn makers sell three billion bags of microwave popcorn every year [source: Seattle Post-Intelligencer]. However, some doctors and consumer groups have been concerned that a chemical used to give microwave popcorn its tasty butter flavor may pose a serious health hazard.

The chemical is called diacetyl, and it's used in the production of microwave popcorn, but it has also likely led to scores of factory workers developing a severe lung condition. Diacetyl occurs naturally in some foods, including butter and many dairy products, fruits, wine and beer. It's reportedly used in "thousands" of food products to add or increase butter flavoring [source: Seattle Post-Intelligencer].

Hundreds of factory workers have developed a condition called "popcorn lung," also known by the medical name bronchiolitis obliterans. The condition is caused by inhalation of diacetyl fumes, which cause scarring in the lungs. Sufferers of popcorn lung have difficulty exhaling, and when severe, the condition can be fatal. In many cases of severe bronchiolitis obliterans, only a lung transplant will save a patient's life. Some former popcorn factory workers died while waiting for transplants.

In September 2007, the murmurs of concern surrounding microwave popcorn became louder as some began to wonder whether consumers were in danger as well. The publicity, caused in part by a suspected case of popcorn lung in a consumer, led four major popcorn makers to announce that they planned to drop diacetyl. The companies -- Weaver Popcorn Co., ConAgra Foods Inc., American Popcorn Company and General Mills Inc. -- had, as of early September, phased out use of the chemical or claimed they would within a year. The companies differed in their reasons for dropping the chemical, but some cited consumer concerns or issues of worker health.

­In 2003 and 2004, federal health officials looked into the cases of several hundred sick workers at popcorn manufacturing plants. Those workers were diagnosed with popcorn lung, likely caused by inhalation of diacetyl fumes. The owner of a popcorn company in Montana died from complications believed to be related to ingredients in popcorn flavoring [source: Seattle Post-Intelligencer]. It's not only hundreds of popcorn factory workers -- workers in candy and potato chip factories have gotten sick as well, as have at least 20 more workers who manufactured products with diacetyl [source: Seattle Post-Intelligencer]. More than $20 million in damages have been paid out as a result of lawsuits filed by factory workers harmed by diacetyl, and as previously mentioned, some workers have died [source: Seattle Post-Intelligencer].

The sick workers in popcorn and candy factories were exposed to large quantities of diacetyl fumes on a daily basis, but could consumers be at risk? On the next page, we'll look at what's believed to be the first case of a popcorn lover suffering from bronchiolitis obliterans.

Risks for Consumers of Microwave Popcorn

It's likely safe to consume microwave popcorn at home,
It's likely safe to consume microwave popcorn at home,
© Photographer: Cerlobea | Agency:

Dr. Cecile Rose, a lung specialist at the National Jewish Medical and Research Center in Denver, Colo., diagnosed the first case of popcorn lung in a consumer of microwave popcorn. That consumer, a man named Wayne Weston, claimed he made microwave popcorn at least twice a day for 10 to 12 years. He said that he loved the smell of buttered popcorn and would open the bag in front of his face and inhale the fumes. But over time Weston developed difficulty breathing and an incessant cough, which eventually landed him in the care of Dr. Rose, an expert on popcorn lung.

While Dr. Rose said that there's no definitive link between Watson's consumption of microwave popcorn and his illness, the connection appears strong. Tests of Watson's home revealed that when popcorn was being cooked, fume levels were comparable to those found in factories [source:]. It likely didn't help that Watson placed his face directly in the path of the diacetyl-laced steam billowing from popcorn bags and did so thousands of times.

In July 2007, Dr. Rose sent a letter about her findings to government health officials, who said they would look into the case. Dr. Rose's tests showed that Watson's symptoms were consistent with popcorn lung, and after he stopped eating buttered popcorn, his lung function improved. He was able to stop taking some of his medications. He also lost 50 pounds.

Eating microwave popcorn is not believed to be harmful. The danger comes from the fumes given off in the cooking process, and consistent exposure to those fumes may be dangerous. The Food and Drug Administration has said that diacetyl is safe to consume, but some consumer rights advocates say more studies need to be done. Proposed legislation in California would ban diacetyl, and a Congresswoman from Connecticut requested that the FDA ban diacetyl until its effects are better understood.

An impending report from the FDA, expected to be released in September 2007, will look at the gases produced when microwaving popcorn. The report should also reveal the quantity of diacetyl and other chemicals to which consumers may be exposed. But some observers complain that the study examines only the type and quantity of fumes produced by microwave popcorn and not their health effects.

The results of the study were released to popcorn makers in 2006, but the FDA said more time was required for peer review and revision before the study could be published in a scientific journal. The FDA claimed it allowed popcorn makers to examine the study to make sure no trade secrets were revealed, but some questioned the decision, with one scientist telling the Seattle Post-Intelligencer that the move was "questionable science at its worst" [source: Seattle Post-Intelligencer].

In the meantime, while factory workers should be concerned, it's probably safe to continue eating buttered popcorn -- just be careful around the fumes or look for a brand that doesn't use diacetyl. For the average popcorn lover, it shouldn't be a problem. The director of the Center for Science in the Public Interest told the Associated Press that the trans fats found in buttered popcorn were more dangerous to consumers than diacetyl [source:].

For more information about diacetyl, the potential dangers of microwave popcorn and other related topics, please check out the links on the next page.

Related HowStuffWorks Articles

More Great Links


  • "4 major popcorn makers to drop toxic chemical." Associated Press. Sept. 5, 2007.
  • "Popcorn-lung patient inhaled directly from bags." Associated Press. Sept. 6, 2007.
  • Emery, Chris. "ConAgra to drop popcorn flavoring." Baltimore Sun. Sept. 6, 2007.,0,5666138.story?coll=bal-pe-asection
  • Harris, Gardiner. "Doctor Links a Man's Illness to a Microwave Popcorn Habit." New York Times. Sept. 5, 2007.
  • Schneider, Andrew. "That buttery aroma might be toxic, too." Seattle Post-Intelligencer. Aug. 30, 2007.