Health hazard evaluation report: HETA-2003-0112-2949, ConAgra Snack Foods, Marion, Ohio.
NIOSH has identified evidence of fixed obstructive lung disease consistent with bronchiolitis obliterans in workers exposed to airborne butter flavoring chemicals at several microwave popcorn plants. In 2002, NIOSH learned that a worker who had mixed oil and butter flavorings for microwave popcorn production at the ConAgra Snack Foods plant in Marion, Ohio, had been diagnosed with severe fixed obstructive lung disease consistent with bronchiolitis obliterans. During an initial visit to the plant in January 2003, NIOSH identified production processes and work practices similar to those of other microwave popcorn plants. Specifically, workers handled many different butter flavorings in open containers and poured the flavorings into open tanks of heated soybean oil. The tanks did not have local exhaust ventilation and the workers did not use respiratory protection. Oil and flavoring mixing activities and all heated tanks were located in one room (slurry room) adjacent to the packaging line area, and the air pressure in this room was positive relative to the packaging line area. NIOSH proceeded to conduct a detailed health and environmental survey at this plant from March 3 to March 10, 2003, in order to characterize exposures and lung function in mixers and other workers. The main findings from this survey included: 1. The mean time weighted average diacetyl air concentration in the slurry room was 1.14 parts per million parts air (ppm). This air concentration is similar to those measured by NIOSH at two other microwave popcorn plants where mixers also developed fixed obstructive lung disease. 2. Three of 12 current slurry room workers were found to have airways obstruction on NIOSH spirometry tests. Two did not respond to bronchodilators, while one did respond but the forced expiratory volume in the first second of exhalation (FEV1) remained below normal. All three had normal diffusing capacity. These findings are consistent with bronchiolitis obliterans. 3. After adjustments to the slurry room ventilation by ConAgra, the slurry room was found to have negative air pressure relative to the packaging area. 4. The mean time weighted average diacetyl air concentration in the packaging area was 0.02 ppm. 5. Five workers in the packaging area had fixed obstruction on spirometry, normal diffusing capacity, and no history of work in the slurry room. All were smokers but were relatively young (average age 36), making smoking a less likely explanation for their obstruction. If packaging area air concentrations of flavoring chemicals were higher in the past when the slurry room was under positive pressure, it is possible that some packaging area workers developed airways obstruction as a result. 6. Two of 11 current quality assurance (QA) lab workers were found to have abnormal spirometry. One had obstruction that was unresponsive to bronchodilator and had a normal diffusing capacity. Another had restriction. Prior to the installation of an enclosure with exhaust ventilation for the microwave ovens, the average diacetyl air concentration in the QA lab at the ConAgra plant was 0.018 ppm, compared to 0.56 ppm in the QA lab at another plant where five of six QA workers were found to have airways obstruction. At the ConAgra plant and other microwave popcorn plants, the pattern of lung function test abnormalities in workers who regularly mix butter flavorings with heated soybean oil implies a risk for the development of fixed airways obstruction from inhalation of flavoring-related chemicals. Nearby packaging workers may also be at risk if flavoring chemicals or dust in the air of the slurry room contaminate the air in the packaging area. Recommendations for engineering controls, use of personal protective equipment, and medical surveillance for exposed workers are provided in this report.