Popcorn lung is extremely rare in the general population. Formally called bronchiolitis obliterans, this condition scars and narrows the tiny airways deep in the lungs, making it progressively harder to breathe. Outside of a few specific high-risk groups, most people will never encounter it. The nickname comes from a cluster of cases among workers in microwave popcorn factories who inhaled a butter-flavoring chemical called diacetyl, but even among those workers the total number of confirmed cases remained small.
Who Actually Gets Popcorn Lung
The vast majority of bronchiolitis obliterans cases fall into two categories: people who have received an organ transplant, and workers with heavy occupational exposure to certain inhaled chemicals. There is no meaningful rate of this disease in the broader public.
Lung transplant recipients face the highest risk by far. Up to 50 to 60 percent of patients who survive five years after a lung transplant develop the condition as a form of chronic organ rejection. It accounts for more than 30 percent of all deaths that occur after the third year following surgery. Bone marrow transplant recipients also face elevated risk, with roughly 3 to 9 percent developing it after the procedure. In both cases, the immune system’s response to the transplanted tissue drives the scarring.
Among flavoring-industry workers, documented cases have been serious but numerically small. A CDC investigation between 2004 and 2007 identified a total of seven workers across four flavor manufacturers in California with severe fixed obstructive lung disease tied to diacetyl exposure. Earlier cases at a Missouri popcorn plant first drew attention to the problem in the early 2000s. These clusters led to significant workplace safety changes, and the number of new occupational cases has dropped since then.
The Vaping Connection
Much of the recent public concern about popcorn lung centers on e-cigarettes and vaping. Some e-cigarette liquids contain diacetyl as a flavoring agent, and the CDC lists it among the potentially harmful substances found in e-cigarette aerosol. The logic is straightforward: if inhaling diacetyl in a factory caused lung scarring, inhaling it from a vape pen could too.
However, there are no confirmed cases of bronchiolitis obliterans directly attributed to vaping in the published medical literature. The wave of vaping-related lung injuries reported in 2019 and 2020, which involved thousands of cases, was a different condition entirely. That outbreak, called EVALI, was primarily linked to vitamin E acetate in illicit THC cartridges, not diacetyl. The two conditions damage the lungs in different ways.
This doesn’t mean vaping diacetyl is safe. The concentrations in e-cigarettes are generally much lower than what factory workers inhaled, but the lungs process inhaled substances differently than the digestive system. A flavoring chemical that’s perfectly safe to eat can still irritate or damage airways when breathed in repeatedly. The long-term effects of low-level, chronic diacetyl inhalation from vaping simply aren’t known yet.
How It’s Diagnosed
Popcorn lung can be tricky to identify because its early symptoms, persistent cough, shortness of breath, and wheezing, overlap with asthma and other common lung conditions. What sets it apart is that the airway obstruction is fixed, meaning bronchodilators (the inhalers that open airways in asthma) don’t help.
Diagnosis typically starts with a breathing test called spirometry, which measures how much air you can push out of your lungs and how quickly. If that shows fixed obstruction, a high-resolution CT scan looks for a characteristic mosaic pattern: patchy areas where air gets trapped in some parts of the lungs while flowing normally through others. These findings sometimes only appear on scans taken while you’re exhaling, so doctors may request both inhale and exhale images. In some cases, a lung biopsy confirms the diagnosis by showing the physical scarring of the small airways.
Progression and Treatment Options
Bronchiolitis obliterans is irreversible. The scar tissue that narrows the airways doesn’t heal or go away. Treatment focuses on slowing further damage and managing symptoms. For transplant patients, adjusting immune-suppressing medications is the primary approach. For occupational cases, removing the person from the chemical exposure is the critical first step, though lung function lost before that point typically doesn’t return.
Corticosteroids and other anti-inflammatory medications can help slow progression in some patients, but response varies widely. In the most severe cases, a lung transplant becomes the only option, though this carries its own significant risks, including the possibility of developing the same condition again in the new lungs. The prognosis depends heavily on how early the condition is caught and what caused it. Workers whose exposure stopped early have fared better than transplant patients dealing with ongoing immune-mediated damage.
Workplace Protections That Reduced Risk
The popcorn factory cases in the early 2000s prompted major changes in how flavoring chemicals are handled industrially. The National Institute for Occupational Safety and Health established recommended exposure limits for diacetyl and a related chemical called 2,3-pentanedione, and employers in the flavoring industry are expected to keep workplace air levels below those thresholds. Engineering controls like better ventilation systems, enclosed mixing processes, and respiratory protection for workers have become standard in facilities that handle these chemicals. Some manufacturers have reformulated their products to eliminate diacetyl entirely, though substitute chemicals aren’t always well studied for inhalation safety.
For the average person who eats microwave popcorn at home, the risk is essentially zero. Consumer exposure to diacetyl from opening a bag of popcorn is thousands of times lower than what factory workers experienced during eight-hour shifts in poorly ventilated mixing rooms.