Summary of Available Information: A number of employees exposed to FFCD have developed serious respiratory illness presenting with persistent dry cough, wheezing, shortness of breath upon exertion, and fixed airways obstruction on spirometry. Several employees have been diagnosed with asthma or bronchiolitis obliterans. Bronchiolitis obliterans occurs when small airways become inflamed and scarred, resulting in the thickening and narrowing of the airways. The symptoms and airways obstruction range from mild to severe, and do not improve when the employee goes home or on vacation. Because bronchiolitis obliterans is a rare disease, some employees may have been potentially misdiagnosed with asthma, bronchitis, emphysema, and/or pneumonia. The loss of pulmonary function associated with severe bronchiolitis obliterans is permanent and some patients have been placed on lung transplant waiting lists. The National Institute for Occupational Safety and Health (NIOSH) has, and continues to investigate, the occurrence of severe lung disease in employees at microwave popcorn packaging plants (NIOSH, 2003) and flavorings manufacturing facilities (Kanwal and Kullman, 2007). NIOSH reported that medical tests of employees at microwave popcorn plants showed fixed airways obstruction, some cases consistent with bronchiolitis obliterans, and other respiratory illnesses such as occupational asthma. NIOSH concluded that the lung diseases identified in these microwave popcorn plant employees were likely due to exposure to butter flavoring chemicals (NIOSH, 2003; Kanwal, et al., 2006). NIOSH also described cases of fixed airways obstruction, including three cases consistent with bronchiolitis obliterans, among employees producing butter and vanilla flavorings containing diacetyl at a flavorings manufacturing facility (Kanwal and Kullman, 2007). NIOSH concluded that, in this facility,  [i]t is highly likely that exposures to diacetyl contributed to the occurrence of severe fixed obstructive lung disease.., but that the role of other flavoring chemicals was unknown (Kanwal and Kullman, 2007). NIOSH also reported that employees at microwave popcorn plants and a flavorings manufacturing facility experienced eye, nasal, and/or upper respiratory irritation and/or burns (NIOSH, 2003; Kanwal and Kullman, 2007). In some cases, skin and eye burns have required medical treatment. For more information about specific NIOSH Health Hazard Evaluations (HHE) regarding these chemicals, see http://www.cdc.gov/niosh/homepage.html. Recent studies have shown respiratory tract damage and death among rodents exposed to diacetyl and butter flavorings containing diacetyl. Hubbs and co-investigators demonstrated in a preliminary study that exposure of rats to 198.4 ppm of diacetyl for 6 hours caused necrosis of the nasal and tracheal epithelium (Hubbs, et al., 2004). In another preliminary study, exposure of mice to 200 and 400 ppm diacetyl via inhalation for 6 hours per day over 5 days caused death, acute necrotizing rhinitis, and erosive or necrotizing laryngitis (Morgan, 2006). This same study also showed exposure of mice to 200 and 400 milligrams per kilogram (mg/kg) diacetyl via oropharyngeal aspiration caused bronchiolar fibrosis and death. Recent inhalation studies have demonstrated that exposure of rats to butter flavoring vapors containing high concentrations of diacetyl (300 ppm) caused epithelial injury in the nasal passages and pulmonary airways (Hubbs, et al., 2002). See more from topic source: https://www.osha.gov/html/a-z-index.html