Popcorn lung gets its name from a cluster of factory workers who developed a rare, serious lung disease after breathing in artificial butter flavoring at a microwave popcorn plant in Missouri in the early 2000s. The medical name is bronchiolitis obliterans, but the connection to popcorn factories was so striking that the nickname stuck.
The Factory Outbreak That Started It All
Between 2000 and 2002, workers at a microwave popcorn factory in Missouri began showing up with an unusual pattern of lung disease. They had trouble breathing, and their symptoms didn’t respond to typical treatments. The CDC investigated and identified bronchiolitis obliterans, a rare and life-threatening form of fixed obstructive lung disease, among the workers. The culprit was a chemical called diacetyl, the compound used to give microwave popcorn its artificial butter flavor.
Diacetyl is naturally present in real butter in tiny amounts, but in factory settings, heated liquid flavorings released it as a volatile vapor. Workers on the production line inhaled concentrated diacetyl fumes day after day. A NIOSH investigation confirmed that diacetyl and a related compound called acetoin were the major volatile components of the butter flavoring vapor these workers breathed in. The Missouri cases drew national attention, and reporters and the public quickly adopted “popcorn lung” as shorthand for the condition. The name captured both the cause and the tragedy in two words.
What Popcorn Lung Actually Does to Your Airways
Bronchiolitis obliterans targets the bronchioles, the smallest airways deep inside your lungs. When you inhale a chemical like diacetyl repeatedly, it triggers inflammation in these tiny tubes. Over time, the inflammation leads to scarring that narrows or completely blocks them. Unlike a temporary illness where swelling goes down and you recover, this scarring is permanent. The damage is irreversible.
That’s what makes popcorn lung so different from conditions like asthma. In asthma, the airways tighten and swell but can relax again with medication. In bronchiolitis obliterans, scar tissue physically replaces the airway lining. Air gets trapped in the lungs, and breathing out becomes progressively harder. The result is a chronic, worsening shortness of breath, dry cough, and wheezing that doesn’t improve with inhalers the way asthma would.
How It’s Diagnosed
Because the symptoms overlap with asthma, COPD, and other lung conditions, diagnosing popcorn lung takes some work. Doctors typically start with your health history, including any chemical exposures or vaping habits, and listen to your breathing. From there, they’ll order imaging like a chest X-ray or CT scan and pulmonary function testing, a noninvasive test that measures how much air you can breathe in and out. In some cases, a lung biopsy is needed, where a small piece of tissue is removed and examined under a microscope to confirm the characteristic scarring pattern.
Treatment Slows It but Can’t Reverse It
There is no cure for popcorn lung. The scarring in the bronchioles is permanent, so treatment focuses on slowing the disease’s progression and managing symptoms. The most common approach involves corticosteroids like prednisone, which reduce inflammation by suppressing the immune system. Bronchodilators, medications that relax the muscles around the airways, can help open breathing passages and provide some relief.
If the disease was triggered by a chemical exposure, removing yourself from that environment is the single most important step. For people whose blood oxygen levels drop too low, supplemental oxygen becomes part of daily life. In the most severe cases, when the disease progresses despite treatment and becomes life-threatening, a lung transplant may be the only remaining option.
The Popcorn Industry’s Response
After the Missouri cases made headlines, major popcorn manufacturers moved to eliminate diacetyl from their products. Weaver Popcorn removed it from its products in 2007. ConAgra Foods, the largest microwave popcorn maker and the company behind Orville Redenbacher and Act II, announced it would follow. The industry largely shifted to substitute chemicals, though some replacements like 2,3-pentanedione raised their own safety questions.
NIOSH established recommended exposure limits of 5 parts per billion for diacetyl and 9.3 parts per billion for 2,3-pentanedione over an eight-hour workday. These are extremely low thresholds, reflecting how potent these chemicals are when inhaled. Notably, OSHA has never set legally enforceable limits for diacetyl or related flavorings. The NIOSH numbers are recommendations, not requirements.
Why Vaping Revived the Concern
The popcorn lung conversation resurfaced with the rise of e-cigarettes. A 2015 study from Harvard’s School of Public Health tested 51 flavored e-cigarette products and found diacetyl in more than 75 percent of them. Out of 51 flavors tested, 39 contained detectable levels of diacetyl. The same study also found acetoin and 2,3-pentanedione, two related chemicals flagged as potential respiratory hazards by the flavoring industry itself.
The concentrations in e-cigarettes are lower than what factory workers inhaled, and no large-scale outbreak of bronchiolitis obliterans has been definitively linked to vaping. But the presence of a chemical already proven to destroy the smallest airways in your lungs raised alarms among public health researchers. The long-term effects of inhaling these compounds through e-cigarettes, potentially for years or decades, remain an open question. What is clear is that diacetyl doesn’t belong in your lungs at any concentration, and the name “popcorn lung” serves as a lasting reminder of what happens when it gets there.