Concern about popcorn lung in the United States has grown as flavored e-cigarette use and occupational exposures in food manufacturing have risen. This article compiles the latest surveillance data, regulatory assessments, and exposure trends to clarify how many cases have been confirmed and what drives the numbers.
Public health agencies classify cases by exposure source and diagnosis method, making direct comparisons difficult across reports. The structured overview below highlights key metrics and data sources most relevant to U.S. cases.
| Source / Period | Primary Exposure Group | Reported Cases in U.S. | Key Notes |
|---|---|---|---|
| CDC Bronchiolitis Obliterans Cases (1990s–2020s) | Food flavoring workers with diacetyl exposure | Reported cluster >8, surveillance estimates vary | Many cases among microwave popcorn plant employees diagnosed before 2007 |
| e-Cigarette or Vaping Associated Lung Injury (EVALI) 2019–2020 | Users of THC and nicotine vaping products | 2,807 hospitalized or died; subset linked to vitamin E acetate | Popcorn lung symptoms reported in some cases, but definitive BO diagnosis less common |
| FDA Tobacco Product Reports (2016–2023) | Consumers of flavored nicotine e-cigarettes | Limited direct popcorn lung counts in filings | Manufacturers provide adverse event summaries; bronchiolitis obliterans is rare in filings |
| National Institute for Occupational Safety and Health (NIOSH) | diacetyl and 2,3-pentanedioneOngoing evaluations; updated HHEs since 2010s | Recommendations led to reduced diacetyl use in many plants; limited new severe cases |
Occupational Cases Linked to Microwave Popcorn Production
Exposure Settings and Worker Populations
Early 2000s investigations identified high rates of bronchiolitis obliterans among flavoring workers exposed to diacetyl in facilities producing microwave popcorn. Many cases were concentrated in states with large food processing sectors, where inhalation of diacetyl-laden steam occurred during opening, mixing, and packaging. Reduced diacetyl use and improved ventilation led to fewer new occupational diagnoses, yet older cohorts continue to be monitored for long-term outcomes.
Surveillance Data from State and Federal Programs
State occupational health programs and NIOSH hazard evaluations compiled case counts, with clusters documented in the Midwest and Gulf Coast regions. These systems rarely publish real-time totals, but retrospective analyses suggest several dozen severe cases were identified during peak investigation periods. The absence of a national mandatory bronchiolitis registry means these figures represent the best available estimates rather than a complete census.
EVALI Cases Associated with Vaping Products in 2019–2020
Clinical Features and Product Links
In 2019 and 2020, multiple patients using e-cigarettes presented with cough, shortness of breath, and imaging patterns suggestive of bronchiolitis obliterans, though vitamin E acetate was more strongly tied to acute lung injury. While popcorn lung was not the dominant clinical finding in EVALI, some reports described persistent airflow obstruction and bronchiolar changes consistent with early obstruction. Regulators emphasized removing vitamin E acetate from illicit THC cartridges, which reduced EVALI case numbers substantially by late 2020.
Limitations in Diagnosis and Reporting
Definitive bronchiolitis obliterans requires surgical lung biopsy, which is rarely performed during acute EVALI. As a result, many patients are classified based on clinical and imaging criteria rather than confirmed pathology. Public health surveillance captured severe respiratory injury but likely undercounts mild or subclinical cases that resolve without specialized care.
Regulatory Actions and Workplace Controls
Occupational Safety Standards
OSHA, NIOSH, and state agencies issued guidance limiting diacetyl and alternative flavoring chemicals in workplaces where aerosols are generated. Requirements for engineering controls, respiratory protection, and medical surveillance have reduced airborne concentrations in many facilities. Despite these measures, small manufacturers and newer vape production settings may still pose inhalation risks if substitution and ventilation practices are inadequate.
Flavor Restrictions in Consumer Products
Regulatory scrutiny on flavored e-cigarettes and enforcement against unauthorized additive combinations aim to limit new exposures. Manufacturers must report adverse events to the FDA, and several companies have reformulated products to remove or reduce diacetyl. Ongoing monitoring by public health agencies helps track whether case counts decline as controls tighten and legacy exposures resolve.
Key Public Health and Workplace Takeaways
- Occupational bronchiolitis obliterans cases were concentrated in microwave popcorn flavoring workers during the early 2000s.
- Surveillance data suggest several dozen severe cases were documented in recognized clusters, with ongoing monitoring of affected cohorts.
- EVALI in 2019–2020 caused severe lung injury, but definitive popcorn lung diagnoses were uncommon and vitamin E acetate was the primary driver.
- Regulatory limits on diacetyl in workplaces and flavoring products, along with enforcement actions, have reduced new exposures.
- Current risks from legal nicotine e-cigarettes are low compared to past illicit THC product exposures, though long-term outcomes remain under study.
FAQ
Reader questions
How many confirmed cases of popcorn lung have been documented in U.S. workers since the 1990s?
Large-scale national surveillance does not exist, but occupational health programs and NIOSH evaluations identified clusters exceeding eight confirmed cases in microwave popcorn facilities during the early 2000s, with additional smaller clusters in other states. Reports suggest several dozen severe cases were documented during peak investigations, though many exposed workers likely had milder, undiagnosed respiratory effects.
Are current e-cigarette users at significant risk for popcorn lung compared to past occupational exposures?
Current evidence indicates that illicit THC vaping products, not nicotine vaping, drove the EVALI outbreak linked to vitamin E acetate. While some users reported bronchiolitis obliterans-like features, definitive diagnoses remain rare. Regulatory removal of vitamin E acetate and tighter oversight of flavor additives have substantially lowered acute injury risks, though long-term outcomes among past users are still being evaluated.
Do flavored consumer products sold legally in the United States still contain diacetyl at levels associated with popcorn lung?
Food safety regulations generally prohibit diacetyl in inhalable consumer products, and manufacturers have reformulated many e-cigarettes and flavored foods. Occasional product tests occasionally detect low levels, but these are typically below thresholds associated with severe airway injury. Continued monitoring and enforcement reduce the likelihood of widespread new occupational or consumer cases.
What should individuals with persistent cough and wheezing do if they suspect popcorn lung from vaping or workplace exposure?
Anyone with ongoing respiratory symptoms and a history of diacetyl or vaping exposure should seek medical evaluation, preferably with a pulmonologist familiar with occupational and vaping lung disease. Spirometry, high-resolution CT imaging, and detailed exposure history help distinguish bronchiolitis obliterans from other conditions, enabling timely management and exposure cessation.