Characterization of Respiratory Exposures at a Microwave Popcorn Plant with Cases of Bronchiolitis Obliterans

Abstract

Eight former workers from a microwave popcorn packaging plant were reported to have severe obstructive lung disease consistent with bronchiolitis obliterans. Investigations into respiratory exposures at this plant were done during August through November of 2000. Samples were collected to assess airborne particulate concentrations, particle size distributions, endotoxins, oxides of nitrogen, organic gases and vapors, and other analytes. Bulk corn and flavoring components were also analyzed for endotoxins and culturable bacteria and fungi. Workers in the microwave production areas of the plant were exposed to particulates and a range of organic vapors from flavorings. The particles were comprised largely of salt and oil/grease particles. Respirable dust concentrations (area plus personal) in the microwave mixer job category, the highest job exposure category in the plant, ranged from 0.13 milligrams per cubic meter of air (mg/m3) to a high of 0.77 mg/m3. Endotoxin concentrations were below 60 endotoxin units per cubic meter of air (EU/m3). Qualitative sampling for volatile organic compounds (VOCs) in the air detected over 100 different VOCs in the microwave area. The predominant compounds identified in the microwave mixing room included the ketones diacetyl, methyl ethyl ketone, acetoin, and 2-nonanone, and acetic acid. Diacetyl, the predominant ketone in the plant, was present in concentrations ranging from below detectable limits to 98 parts per million parts air by volume (ppm), with a mean of 8.1 ppm (standard deviation 18.5 ppm). The average ketone concentrations were highest in the microwave mixing room where the 10 area samples had a mean diacetyl concentration of 37.8 ppm (SD 27.6 ppm) and a mean acetoin concentration of 3.9 ppm (SD 4.3 ppm). These data show that workers involved in microwave popcorn packaging can be exposed to a complex mixture of VOCs from flavoring ingredients; animal studies show that diacetyl can cause airway epithelial injury, although the contributions of other specific compound(s) associated with obstructive respiratory disease in these workers is still unresolved.

Evaluation of Flavorings-Related Lung Disease Risk at Six Microwave Popcorn Plants

“…A NIOSH cross-sectional medical and environmental survey at plant A (the index plant) revealed an elevated prevalence of obstructive lung disease that was associated with cumulative exposure to diacetyl, the predominant butter-flavoring chemical in the air of the plant. 1,2 In experiments conducted at NIOSH, rats exposed to vapors from a butter flavoring used at this plant developed severe injury of their airway epithelium. 3 Rats developed similar airway damage (although less extensive) with inhalation of vapors of pure diacetyl.…”

Diacetyl Exposures at Four Microwave Popcorn Plants

“…(1) The highest measurement in this data set was 3.9 ppm. This difference may be due in part to the collection of area samples during the NIOSH work to characterize exposure.…”

“…The basic production process has been described in detail by others. (1,3) Photographic illustrations of a mixing room and the larger plant filling and packaging areas have been published. (1) The facilities in this report were similar in layout.…”

“…(1) A wide variety of airborne contaminants were measured in the plant, including area concentrations of the ketones diacetyl, acetoin, 2-nonanone, and methyl ethyl ketone. Among these ketones, diacetyl concentrations evaluated using NIOSH Method 2557 were the highest, with mean concentration of all area samples (n = 53) of 8.1 ppm.…”

Lung function (spirometry) testing in employees at a flavorings manufacturing plant - Indiana.

“…Increasing cumulative exposure of workers to diacetyl has been associated with an increased prevalence of abnormal lung function [Kreiss et al 2002;Kullman et al 2005;NIOSH 2004]. In animal experiments conducted by NIOSH, rats exposed to vapors from diacetyl developed severe injury to their airways [Hubbs et al 2004].…”