Work Tasks as Determinants of Grain Dust and Microbial Exposure in the Norwegian Grain and Compound Feed Industry.
OBJECTIVE
The grain and compound feed industry entails inevitable risks of exposure to grain dust and its microbial content. The objective of this study was therefore to investigate task-dependent exposure differences in order to create knowledge basis for awareness and exposure reducing measures in the Norwegian grain and compound feed industry.


METHODS
A total of 166 samples of airborne dust were collected by full-shift personal sampling during work in 20 grain elevators and compound feed mills during one autumn season and two winter seasons. The personal exposure to grain dust, endotoxins, β-1→3-glucans, bacteria, and fungal spores was quantified and used as individual outcomes in mixed models with worker nested in company as random effect and different departments and tasks as fixed effects.


RESULTS
The exposure levels were highest in grain elevator departments. Exposure to endotoxins was particularly high. Tasks that represented the highest and lowest exposures varied depending on the bioaerosol component. The most important determinants for elevated dust exposure were cleaning and process controlling. Cleaning increased the dust exposure level by a factor of 2.44 of the reference, from 0.65 to 1.58mg m(-3), whereas process controlling increased the dust exposure level by a factor of 2.97, from 0.65 to 1.93mg m(-3). Process controlling was associated with significantly less grain dust exposure in compound feed mills and the combined grain elevators and compound feed mills, than in grain elevators. The exposure was reduced by a factor of 0.18 and 0.22, from 1.93 to 0.34mg m(-3) and to 0.42mg m(-3), respectively, compared with the grain elevators. Inspection/maintenance, cleaning, and grain rotation and emptying were determinants of higher exposure to both endotoxin and β-1→3-glucans. Seed winnowing was in addition a strong determinant for endotoxin, whereas mixing of animal feed implied higher β-1→3-glucan exposure. Cleaning was the only task that contributed significantly to higher exposure to bacteria and fungal spores.


CONCLUSIONS
Cleaning in all companies and process controlling in grain elevators were the strongest determinants for overall exposure, whereas seed winnowing was a particular strong determinant of endotoxin exposure. Exposure reduction by technical intervention or personal protective equipment should therefore be considered at work places with identified high exposure tasks.
1.Department of Chemical and Biological Work Environment, National Institute of Occupational Health, PO Box 8149 Dep, Oslo N-0033, Norway anne.straumfors@stami.no.
Anne
A
Straumfors
1.Department of Chemical and Biological Work Environment, National Institute of Occupational Health, PO Box 8149 Dep, Oslo N-0033, Norway.
Kari Kulvik
KK
Heldal
2.Division of Environmental Epidemiology, Institute of Risk Assessment Sciences, PO Box 80178, Utrecht 3508TD, The Netherlands.
Inge M
IM
Wouters
1.Department of Chemical and Biological Work Environment, National Institute of Occupational Health, PO Box 8149 Dep, Oslo N-0033, Norway.
Wijnand
W
Eduard
D000391:Air Microbiology; D000395:Air Pollutants, Occupational / Q000032:analysis*; D000821:Animal Feed / Q000032:analysis*; D001419:Bacteria; D004391:Dust / Q000032:analysis*; D002523:Edible Grain / Q000382:microbiology; D004731:Endotoxins / Q000032:analysis; D004784:Environmental Monitoring / Q000295:instrumentation; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis*; D009664:Norway; D016273:Occupational Exposure / Q000032:analysis; D011482:Protective Devices; D013172:Spores, Fungal; D017132:Workplace; D047071:beta-Glucans / Q000032:analysis
D000395:Air Pollutants, Occupational; D004391:Dust; D004731:Endotoxins; D047071:beta-Glucans
bacteria; endotoxin; exposure assessment; fungal spores; grain industry; β-1→3-glucans