In September 2002, the National Institute for Occupational Safety and Health (NIOSH) received a request for a health hazard evaluation (HHE) from employees at Agrilink Foods Popcorn Plant, Ridgway, Illinois. The respiratory health concerns cited in the request included cough, shortness of breath, and chest pain; and exposure concerns included butter flavorings, coloring agents, and salt. We conducted a walk-through survey October 22-23, 2002 and an industrial hygiene survey November 5- 6, 2002. Average area diacetyl air levels in the mixing tank area, microwave popcorn packaging line, and quality control room were 0.60, 0.33, and 0.19 parts per million parts air by volume, respectively. Average personal diacetyl air levels for the mixer, microwave popcorn packaging line machine operator, and quality control workers were 0.37, 0.64, and 0.06 parts per million parts air by volume, respectively. On November 19-21, 2002, 35 current workers (73%) participated in health questionnaire interviews and spirometry and lung diffusing capacity testing. Comparisons to national data were performed which controlled for race, age group, and smoking status. These comparisons demonstrated that plant employees aged 17 to 39 had about a 3 times greater rate of chronic cough, and plant employees aged 40 to 69 who had never smoked had about a 2 times greater rate of shortness of breath. We supplemented our 35 spirometry test results with company results for individuals who did not volunteer in our study, and used spirometry tests for 41 workers for our analysis. Plant employees overall and plant employees aged 40 to 69 had about a 2 times greater rate of airways obstruction, compared to national rates. Despite the small number of workers in this study, we were able to demonstrate statistical significance for the elevated airways obstruction rate in workers aged 40 to 69. None of the tested workers with obstruction demonstrated reversibility with the administration of bronchodilator. The survey findings are best explained by work-related bronchiolitis obliterans due to exposures arising from the open configuration of the mixing tanks which allowed volatile organic compounds (VOCs) to be disseminated to other areas of the plant, as well as due to the quality control process where many bags of microwave popcorn were popped in a small room with minimal general dilution ventilation.