Learn About Popcorn Lung Development and Research

What Is Popcorn Lung and How Does It Develop

Popcorn lung, officially called bronchiolitis obliterans (BO), is a serious lung disease that damages the smallest airways in the lungs called bronchioles. The name "popcorn lung" came from cases discovered in workers at popcorn manufacturing facilities in the 2000s. The disease causes these tiny airways to become scarred and narrowed, making it increasingly difficult for air to move through the lungs. Unlike many lung diseases that develop slowly over decades, popcorn lung can progress relatively quickly once it starts.

The disease develops when a person inhales chemicals that irritate and inflame the lung tissue. The most well-known chemical linked to popcorn lung is diacetyl, a flavoring compound used in butter-flavored microwave popcorn and other food products. When workers breathed in diacetyl dust and vapors during manufacturing, their lungs became damaged. The inflammation causes the small airways to become filled with scar tissue, which gradually blocks airflow. Over time, the lungs lose their ability to transfer oxygen to the bloodstream effectively.

Popcorn lung differs from other chronic lung diseases in several ways. Conditions like emphysema destroy the air sacs themselves, while popcorn lung specifically scars the small airways that connect to those sacs. This makes it a unique pattern of lung damage. The disease is also considered irreversible—once the scarring occurs, current medical treatments cannot undo the damage. This is why prevention through avoiding exposure to harmful chemicals is so critical.

The timeline for developing popcorn lung varies between individuals. Some workers exposed to high levels of diacetyl showed signs of the disease within months, while others took years to develop symptoms. Factors that influence how quickly the disease develops include the concentration of chemicals in the air, how long and frequently a person was exposed, and individual differences in how people's lungs respond to injury. Smoking and other pre-existing lung conditions may also increase vulnerability.

Practical takeaway: Understanding that popcorn lung develops from inhalation of specific chemicals—not from genetics or lifestyle factors alone—helps explain why certain workplace exposures carry particular risks. Recognizing the connection between environmental exposure and this disease is the first step in prevention and early detection.

The Role of Diacetyl and Other Harmful Chemicals

Diacetyl is a chemical compound that creates a buttery flavor and aroma in food products. For decades, food manufacturers used diacetyl extensively in microwave popcorn flavoring, where workers faced the highest exposure levels. The chemical appears as a dust and vapor that workers inhaled during manufacturing, flavoring, and packaging processes. When inhaled repeatedly, diacetyl triggers an abnormal immune response in the lungs that leads to the scarring characteristic of popcorn lung.

The discovery of popcorn lung in workers happened in the early 2000s when doctors noticed an unusual cluster of lung disease cases among employees at a popcorn manufacturing plant in Missouri. Eight workers at one facility developed bronchiolitis obliterans, a disease that was previously rare in people under age 60. Researchers investigating these cases found that diacetyl exposure was the common factor. This discovery led to investigations at other popcorn facilities across the United States, where additional cases were identified. The pattern was clear: workers handling diacetyl-containing flavoring had significantly higher rates of this lung disease compared to the general population.

Beyond diacetyl, researchers have identified other chemicals that can cause similar lung damage. These include:

• 2,3-pentanedione, a chemical used as a diacetyl substitute in some flavorings
• Acetoin, another butter flavoring chemical
• Acetic anhydride, used in manufacturing processes
• Chlorine gas, which can occur in industrial accidents
• Ammonia, common in cleaning products and certain manufacturing settings
• Sulfur dioxide, released during welding and in some food processing

The mechanism by which these chemicals cause lung damage is still being researched, but scientists understand that they trigger inflammation in the small airways. This inflammation leads to excessive production of collagen, a protein that forms scar tissue. The scar tissue progressively blocks the airways, reducing the lungs' capacity to exchange oxygen and carbon dioxide. Even after exposure stops, the scarring process may continue, which is why early detection and removal from exposure is critical.

Following public health awareness about diacetyl, many food manufacturers reformulated their products to eliminate or reduce this chemical. The Occupational Safety and Health Administration (OSHA) has issued guidance on controlling exposure to diacetyl and other chemicals associated with popcorn lung. However, not all countries have the same regulations, and some smaller facilities may not have implemented these changes. Workers in developing nations may still face significant exposure risks from these chemicals.

Practical takeaway: Knowing which chemicals are associated with popcorn lung helps workers identify potential hazards in their workplace. If your job involves handling butter flavorings, cleaning supplies, or working in facilities where acetoin or pentanedione are used, understanding these risks allows you to take precautions and advocate for safer working conditions.

Occupational Exposure and At-Risk Workers

Occupational exposure remains the primary pathway for developing popcorn lung, though the disease can theoretically result from any significant inhalation of harmful chemicals. Workers in specific industries face the highest risks. Popcorn manufacturing facilities represent the most well-documented source of exposure, particularly in roles where workers handle raw flavoring chemicals or packaged popcorn seasoning. The Centers for Disease Control and Prevention (CDC) has investigated multiple cases in workers at microwave popcorn facilities, with some facilities reporting cases among several employees.

Beyond popcorn manufacturing, workers in other food flavoring facilities face similar risks. These include facilities that produce butter flavoring for crackers, cheese products, baked goods, and other food items. Workers who mix, apply, or package these flavorings experience direct exposure to diacetyl and related chemicals. Employees in smaller operations and those working with inadequate ventilation face particularly high risks. Some cases of popcorn lung have also been identified in workers at facilities producing e-liquid for electronic cigarettes, where diacetyl and similar flavorings were initially used without adequate controls.

The specific jobs within these facilities that carry the highest risk include:

• Flavoring technicians who mix and prepare butter flavoring chemicals
• Packaging line workers who fill and seal popcorn bags with flavored product
• Quality control inspectors who spend time in areas with high chemical concentrations
• Maintenance workers who clean equipment contaminated with flavoring residue
• Warehouse workers who handle large quantities of flavoring materials
• Equipment operators in facilities with poor ventilation systems

A significant case occurred at a popcorn facility in Jasper, Missouri, where nine workers developed bronchiolitis obliterans between 2000 and 2007. These workers had direct contact with diacetyl-containing flavorings and worked in areas where ventilation was limited. OSHA investigations found that exposure levels in some areas of the facility exceeded safety recommendations. This case became one of the most extensively studied popcorn lung clusters and led to major changes in workplace safety standards for the food flavoring industry.

Exposure levels vary dramatically depending on workplace conditions. Workers in facilities with modern ventilation systems and proper protective equipment face significantly lower risks than those in older facilities with minimal controls. A worker's length of employment also matters—someone who worked in a popcorn facility for 15 years at high exposure levels faces greater risk than someone with 2 years of exposure. Individual susceptibility varies too; some people may develop symptoms after relatively brief exposure, while others with longer exposure may never develop the disease, though this does not mean they were not harmed by the exposure.

Practical takeaway: If you work in food manufacturing, flavoring production, or related industries, learning about the specific exposures in your workplace helps you recognize hazards. You can then request information about ventilation systems, request protective equipment, and monitor your own health for early warning signs. Understanding which roles carry the highest risk can also guide decisions about job placement within your facility.

Symptoms, Diagnosis, and Early Detection

Popcorn lung symptoms often develop