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Gilster-Mary Lee Corporation, Jasper, Missouri
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January 2006
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Journal Article:NIOSH health hazard evaluation report
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Description:In August 2000, the Missouri Department of Health and Senior Services requested technical assistance from the National Institute for Occupational Safety and Health (NIOSH) in an investigation of severe obstructive lung disease (bronchiolitis obliterans) in former workers of the Gilster-Mary Lee popcorn plant in Jasper, Missouri. Affected workers had worked in the room where butter flavoring was mixed into heated soybean oil (mixing room) and in the adjacent microwave popcorn packaging-area. A NIOSH medical and environmental survey at the plant in November 2000 showed that plant employees had 3.3 times the rate of obstruction on NIOSH spirometry tests compared to national rates; the prevalence of obstruction in never-smokers was 10.8 times the national rate. Nineteen of 21 workers with obstruction had fixed obstruction (unresponsive to bronchodilators), and most chest x-rays and diffusing capacity tests were normal. These findings are consistent with constrictive bronchiolitis obliterans. Five of six quality control (QC) workers who repeatedly popped bags of product in microwave ovens (approximately 100 bags per worker per work shift) in a poorly ventilated room were found to have obstruction on spirometry. A strong exposure-response relationship was demonstrated between quartiles of estimated cumulative exposure to diacetyl (a volatile butter flavoring chemical contaminating the air in the plant) and the frequency of airways obstruction on spirometry tests. NIOSH investigators provided air purifying respirators that filtered both vapors and particulates for mixers and assisted with employee training in respiratory protection. In January 2001, NIOSH investigators conducted a detailed engineering control assessment and provided exposure control recommendations. NIOSH performed seven additional cross-sectional medical and environmental surveys from April 2001 through August 2003 to determine if controls were effective in reducing exposures and protecting workers. Follow-up Environmental Findings: As a result of the implementation of exposure controls from January 2001 through May 2003, average diacetyl air concentrations declined two orders of magnitude in the mixing room (from 38 ppm to 0.46 ppm) and the QC laboratory (from 0.54 to 0.002 ppm), and three orders of magnitude in the packaging area (from 1.69 ppm to 0.002 ppm for machine operators). Follow-up Medical Survey Findings: A total of 373 current workers participated in one or more NIOSH surveys. Participation by current workers at each survey ranged from 71% to 91%. One hundred eighty six of the 373 total participants participated in more than one survey (50%). However, participation in more than one survey was much greater for workers hired prior to the first NIOSH survey (Cohort-1; 100 of 146 participants, 68%) than for workers hired after the first NIOSH survey (Cohort-2; 86 of 227 participants, 38%). From the first to last survey, there was a statistically significant decline in the prevalence of eye, nose, and throat irritation in Cohort-1 participants but no significant changes in the prevalences of other symptoms or spirometry abnormalities, or in mean percent predicted FEV1. Cohort-2 participants had lower prevalences of symptoms and spirometry abnormalities, and a higher mean percent predicted FEV1, compared to Cohort-1 participants at their first survey. There were no statistically significant changes in these outcomes over time for Cohort-2 participants. Of the 88 Cohort-1 participants who participated in three or more NIOSH medical surveys, 19 (22%) had FEV1 declines of greater than 300 ml and/or 10% from their first to their last spirometry test, compared to 3 of 41 (7%) Cohort-2 participants who participated in three or more surveys. Four of nine participants who worked as mixers after the 1st NIOSH survey had FEV1 declines of greater than 300 ml and/or 10% of baseline, including one mixer who declined more than 1300 ml in nine months while working as a mixer. The total FEV1 decline in this mixer was 2800 ml over 2.75 years, which included a 1500 ml decline over two years after stopping work as a mixer. The NIOSH investigation at the Gilster-Mary Lee microwave popcorn plant in Jasper, Missouri, determined that inhalation exposure to butter flavoring chemicals is a risk for occupational lung disease. With the exposure controls implemented to date, workers in the microwave popcorn packaging area should now be at minimal risk as long as isolation of the mixing room and mezzanine is maintained and all ventilation systems are operational. The exposure controls implemented in the QC laboratory have likely minimized the risk to workers in this area as well. However, QC laboratory workers should have regularly scheduled spirometry to assure that their lung function remains stable. Mixers are still at potential risk from open handling of butter flavorings and from tank emissions. Use of appropriate respiratory protection by mixers and other workers who enter the mixing room and mezzanine area is a short-term solution to this problem. Re-engineering the oil and butter flavoring mixing process to a closed system (so that mixers do not have to handle open containers of flavoring and no longer have to open tanks that contain heated oil and/or butter flavoring) is recommended to eliminate this risk. Until a closed process is implemented, all workers who enter the mixing room or mezzanine should use appropriate respiratory protection when in those locations and should have regularly scheduled spirometry to identify early declines in lung function that may be due to exposures to butter flavoring chemicals.
NIOSHTIC No. 20029487
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