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Fixed airways obstruction in a microwave popcorn packaging facility

Susanna G. Von Essen, MD

Univ. of Nebraska Medical Center

Omaha, NE


A 54-year-old, non-asthmatic, nonsmoker had worked for four years in a microwave popcorn packaging facility, where his duties included mixing flavorings with oil and salt. One week after beginning to use a new artificial butter flavoring (containing jalapeño peppers), he developed blurred vision from corneal ulceration, and worsening of his mild chronic cough, which was productive of white sputum. Bibasilar rales were apparent on auscultation of the chest. Pulmonary function tests showed mild airway obstruction, with no improvement after albuterol inhalation. The diffusing capacity for carbon monoxide was normal. A computed tomographic scan of the thorax with inspiratory and expiratory views was suggestive of mild air trapping.

The work facility received raw corn and produced packaged popcorn. The process of mixing salt, oil, and flavoring produced visible dust. Popcorn was then added; and packaged into single-serving bags for use in microwave ovens. The popcorn processing plant subsequently closed down for two weeks. During this time, the patient was treated with prednisone 40 mg per day for fourteen days. One week after the first clinic visit, he reported improvement in his cough and his FEV1. After the plant reopened, he returned to his full time job, mixing the previous butter flavoring. When he was reassessed six weeks after diagnosis, his FEV1 had further increased, but still had residual mild airway obstruction. His cough had resolved, and his corneal ulcerations had healed. Till this date, the worker continues to be employed at this facility.

Table 1: Listing of Pulmonary Function Tests

  FVC (%) FEV1 (%) FEV1/FVC FEF 25-75% RV/TLC (%) DLCO (%)
At diagnosis 3.88 (83) 2.55 (67) 66 1.53 (39) 44.3 (126) 27.6 (107)
One week later 4.45 (94) 3.02 (79) 68 1.87 (48) 41.8 (119) 28.2 (109)
Six weeks later 4.94 (105) 3.22 (84) 65 1.71 (44) 35.6 (101) 24.4 (95)

In summary, this microwave popcorn plant worker routinely exposed to an artificial butter flavoring developed respiratory abnormalities and corneal ulcerations after handling a new flavoring. PFTs showed a fixed airway obstruction. The patient showed improvement after stopping exposure to the new butter flavoring. Corticosteroids may have also played a role in his improvement [1].

Microwaveable Popcorn


An unusual concentration of bronchiolitis obliterans-type symptoms in a small population of former employees at a microwave popcorn packaging facility in Missouri was reported in the spring of 2000 [2-4]. Epidemiological investigations suggested that workers exposed to flavorings at these popcorn factories were at risk for developing fixed obstructive lung disease. The butter-like flavoring for popcorn is provided by the chemical Diacetyl (2, 3- Butanedione). Diacetyl occurs naturally in butter, coffee and bay oil, and has previously not been described as toxic when inhaled. At this time, it is still unclear if Diacetyl is the causative agent for this disease.

It is believed that these cases represent a new and potentially lethal occupational pulmonary disease, Popcorn Workers' Lung [5]. All occupational health providers are encouraged to monitor employees who work in and around food flavorings. Any eye, upper respiratory and pulmonary symptoms among these workers require investigation. Unless exposure is stopped and therapy is initiated early on, the changes may be rapidly progressive and irreversible. Good work practices to reduce exposure to the suspect agents should be urged. These include engineering projects to improve ventilation and isolate ventilation in the mixing room from that in other areas of the plant, and personal protective equipment such as air-purifying respirators with cartridges that filter organic vapors and particulates [4]. If any such cases are identified, the state public health department and National Institute for Occupational Safety and Health (NIOSH) should be notified immediately (Richard Kanwal, MD at 1-800-232-2114 or rnk@cdc.gov). The Centers for Disease Control and Prevention (CDC) has currently no evidence to suggest risk for consumers in the preparation and consumption of microwave popcorn.


If any ATS member has experience with similar cases, please e-mail to asood2@siumed.edu.


1. Parmet, A.J. and S. Von Essen, Rapidly progressive, Fixed Airway Obstructive Disease in Popcorn Workers: A New Occupational Pulmonary Illness? J Occup Environ Med, 2002. 44(3): p. 216-218.
2. Fixed obstructive lung disease in workers at a microwave popcorn factory--Missouri, 2000-2002. MMWR Morb Mortal Wkly Rep, 2002. 51(16): p. 345-7.
3. From the Centers for Disease Control and Prevention. Fixed obstructive lung disease in workers at a microwave popcorn factory--Missouri, 2000- 2002. JAMA, 2002. 287(22): p. 2939-40.
4. Kreiss, K., et al., Clinical bronchiolitis obliterans in workers at a microwave-popcorn plant. N Engl J Med, 2002. 347(5): p. 330-8.
5. Schachter, E.N., Popcorn worker's lung. N Engl J Med, 2002. 347(5): p. 360-1.