Popcorn lung, known medically as bronchiolitis obliterans, is extremely rare in the general population. Outside of very specific high-risk groups, the number of confirmed cases worldwide remains in the low hundreds. Most people encounter the term through headlines about vaping, but the condition has been documented far more often after organ transplants and industrial chemical exposure than from e-cigarette use.
What Popcorn Lung Actually Is
Bronchiolitis obliterans is a condition where the smallest airways in the lungs become scarred and narrowed, permanently restricting airflow. Unlike asthma, the obstruction doesn’t respond to bronchodilators or other medications that relax the airways. Once the scarring occurs, it’s largely irreversible. The name “popcorn lung” comes from a cluster of cases in the early 2000s among workers at microwave popcorn factories who were breathing in a butter-flavoring chemical called diacetyl.
The Original Popcorn Factory Cases
The CDC documented the first cluster in 2000 when an occupational medicine physician reported eight cases of fixed obstructive lung disease in former workers at a single microwave popcorn factory in Missouri. Of those eight patients, four were mixers who handled flavoring chemicals directly and four worked in packaging. Additional cases were later identified at a flavoring manufacturing facility and another popcorn factory in Nebraska.
These cases led to significant changes in workplace safety standards for the food flavoring industry, and many manufacturers reduced or eliminated diacetyl from their products. The total number of occupational cases across the U.S. remained small, concentrated almost entirely among workers with heavy, prolonged exposure to flavoring chemicals in poorly ventilated environments.
Where Popcorn Lung Is Most Common
The group most frequently affected by bronchiolitis obliterans isn’t factory workers or vapers. It’s transplant recipients. The condition is a well-known complication of lung transplantation, where the immune system gradually attacks the transplanted tissue. It also affects roughly 2% to 3% of all patients who receive bone marrow transplants from a donor, and about 6% of those who develop chronic graft-versus-host disease, a condition where transplanted immune cells attack the recipient’s body.
Other known triggers include severe respiratory infections, exposure to industrial fumes and gases (such as nitrogen dioxide or sulfur dioxide), and certain autoimmune conditions. In each of these scenarios, the mechanism is the same: something causes inflammation that damages the small airways, and the body’s healing response produces scar tissue that narrows them permanently.
Vaping and Popcorn Lung Risk
This is the question most people are really asking, and the honest answer is that confirmed cases of popcorn lung from vaping are vanishingly rare. As of 2024, medical literature contains only isolated case reports. One published case involved a woman in her 40s who vaped and developed rapid-onset shortness of breath and cough. Lung function testing showed severe airway obstruction that didn’t improve with bronchodilator treatment, and imaging revealed extensive air trapping, a hallmark of bronchiolitis obliterans. A lung biopsy confirmed the diagnosis.
The concern about vaping originally arose because some e-cigarette liquids contained diacetyl and related flavoring chemicals. While many manufacturers have since removed diacetyl from their products, not all have, and regulation varies widely. The levels found in e-cigarettes have generally been far lower than what popcorn factory workers were inhaling, which is one reason confirmed cases remain so scarce.
It’s worth understanding that vaping causes other forms of lung injury that are more common and better documented. EVALI (E-cigarette or Vaping Use-Associated Lung Injury), first identified in 2019, is an umbrella term covering several lung diseases linked to e-cigarettes. The American Lung Association lists bronchiolitis obliterans as one possible form of EVALI, but most EVALI cases involve different patterns of lung damage, particularly acute inflammatory injury rather than the chronic airway scarring seen in popcorn lung. EVALI can be fatal and caused a significant outbreak in 2019, largely linked to vitamin E acetate in THC-containing vape products.
Why It’s Hard to Diagnose
Part of the reason popcorn lung appears so rare may be that it’s genuinely difficult to confirm. Standard chest X-rays are neither sensitive nor specific enough to detect it. High-resolution CT scans can show suggestive patterns like mosaic attenuation (patchy differences in lung density) and air trapping on exhaled images, but these findings alone aren’t definitive. Lung function testing can show obstruction that doesn’t respond to bronchodilators, which raises suspicion, but the gold standard for diagnosis is a surgical lung biopsy, an invasive procedure that many patients and doctors are reluctant to pursue.
In transplant recipients, clinicians typically rely on a sustained decline in lung function over time rather than biopsy. The diagnosis requires ruling out a long list of other possible causes, including infection, acute rejection, and weight gain affecting breathing mechanics. In non-transplant patients, the diagnostic path is even less standardized, meaning mild or early cases could easily be misdiagnosed as asthma, COPD, or another obstructive lung disease.
Putting the Risk in Perspective
For someone who doesn’t work in a flavoring factory and hasn’t had a transplant, the odds of developing popcorn lung are extraordinarily low. The condition has no meaningful prevalence rate in the general population because it occurs almost exclusively in people with specific, identifiable exposures. Even among vapers, confirmed cases remain limited to individual case reports rather than clusters or epidemics.
That said, the rarity of a confirmed diagnosis doesn’t necessarily mean vaping carries zero risk to your small airways. The long-term effects of inhaling flavoring chemicals at low levels over many years aren’t fully understood, and the difficulty of diagnosing bronchiolitis obliterans means some cases may go unrecognized. What is clear is that the dramatic “vaping causes popcorn lung” headlines have outpaced the actual evidence. The real, documented respiratory risks of vaping are more likely to involve other forms of lung inflammation and injury than this specific condition.