UBC Faculty Research and Publications

Exposure in grain elevators: are we measuring the relevant agent? (presentation) Kennedy, Susan M. 2008

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Exposures in grain elevators: are we measuring the relevant agent? Relationship between grain dust, endotoxin, and 1,3 β - D glucan exposure levels Susan Kennedy, Karen Bartlett, Helen Dimich-Ward Occupational and Environmental Hygiene Program University of British Columbia, Vancouver CANADA Presented at:  American Industrial Hygiene Conference and Exhibition, Toronto Canada, 1999 Acknowledgements: • Human Resources Development Canada • Beryl Kirk; Lyn Peters, Jim Benyon • BC Terminal Elevator Operators Association • Grain Workers Union • British Columbia Lung Association • Dept of Environmental Sciences, Wageningen Agricultural University Composition of grain dust: • varies with geographic site, species, season, storage temperature, … • major components: • fractured kernels, seeds, husks • animal feces • storage mites, insects • bacteria, moulds • crustal particles (incl. silica) • pesticides Rationale: Grain components and respiratory health • Dust • assoc. with ↑ respiratory symptoms; ↓ lung function • Endotoxins • potent pro-inflammatory agent (gram neg. bacteria) • assoc. with grain fever, acute & chronic resp. symptoms • 1,3 β -D glucans • major fungal cell wall component  (also found in some bacteria, most plants) • some evidence of link with irritant symptoms Objectives: As part of mandated grain elevator monitoring program: • Measure dust, endotoxin and glucan levels • Record readily available “determinants of exposure” data • Compare exposure levels, determinants of exposure • Evaluate significance of results for future studies and for prevention Sampling methods: method detail gravimetric sampling 37 mm open faced cassettes, flow rate: 1.7 l/min for 6-7 hours heat-depyrogenated glass fibre filtres endotoxin analysis kinetic, turbidimetric LAL assay; Pyrogent 5000 ® reagent 1,3 β-D glucan analysis rabbit polyclonal anti-laminarin inhibition assay Determinants of exposure evaluated: elevator 6 companies job group 10 job title groups time in  tasks / locations sweeping; maintaining machinery in elevator; outdoors; in office or control room; in maint.shop weather / season season (2 sampling periods); temperature, humidity; % rain, sun grain type / amt. tonnage of grain received / shipped per day; grain species: % wheat, barley, rye, canola, other Personal Samples - Summary Results dust (mg/m3) endotoxin (ng/m3) glucan (μg/m3) n 376 371 187 range < 0.13 - 63.7 <0.28 - 17,650 <2.9 - 96.8 < DL 21.0% 13.7% 19.8% GM (GSD) 0.63 (3.8) 11.4 (17.6) 7.92 (2.8) ‘reference’ level 4.0 1 5.0 2 % > ref. val 10.4% 50.1% 1: ACGIH ;  2: Dutch Health Council, proposed Dust v. Endotoxin Concentration in Air 0.1 1 10 100 1000 10000 100000 0.01 0.1 1 10 100 Dust Concentration (mg/m3) E n d o t o x i n  ( n g / m 3 ) R=0.83, p<.001 Dust v. 1,3 β-D Glucan Concentration in Air 1 10 100 1000 0.01 0.1 1 10 100 Dust Concentration (mg/m3) G l u c a n  ( u g / m 3 ) R=0.77, p<.001 Endotoxin v. Glucan Content  (per g. dust) 1 10 100 0.1 1 10 100 1000 10000 Endotoxin Content (ng/g.dust) G l u c a n  C o n t e n t  ( u g / g . d u s t ) R = -0.04 Factors associated with increased exposure Dust Endotoxin Glucan Job groups • sweeper • cleaner fl. op • sweeper • cleaner fl. op • sweeper • cleaner fl. op Tasks (time) • sweeping •maintenance • sweeping •maintenance • sweeping •maintenance • misc. tasks Elevator • company A • company A • company A Factors associated with decreased exposure Dust (mg/m3) Endotoxin (ng/m3) Glucan (ug/m3) Job groups • trackshed op. • control op • supervisor • trackshed op. • control op. • supervisor none Tasks • time outdoors • time outdoors none Season • winter model R2 0.38 0.47 0.40 Determinants of exposure - summary of comparison • Endotoxin and glucan levels • highly correlated with dust level • Determinants of dust v. endotoxin • jobs / tasks same rank order • endotoxin significantly decreased in winter • Determinants of dust v. glucan • same high exposure jobs / tasks • signif. differences re low / med exposure rankings Relevance: for future studies of possible health consquencies of grain elevator exposures Question: With only job title and company information, how are jobs categorized into exposure risk groups, according to dust, endotoxin, glucan level? Job groups - ordered by dust and endotoxin level 0 1 2 3 co nto l o p su pe rv. tra ck sh ed pe lle t p l ba se /an ne x ele ctr /m w dis tr/b ins sh ee tm eta l sw ee pe r cle an er fl. D u s t  L e v e l  ( m g / m 3 ) 0 25 50 75 100 125 150 175 200 225 E n d o t o x i n  L e v e l  ( n g / m 3 ) Dust Endotoxin Job groups - ordered by dust and glucan level 0 1 2 3 co nto l o p su pe rv. tra ck sh ed pe lle t p l ba se /an ne x ele ctr /m w dis tr/ bin s sh ee tm eta l sw ee pe r cle an er fl. D u s t  L e v e l  ( m g / m 3 ) 0 5 10 15 20 25 30 35 G l u c a n  L e v e l  ( u g / m 3 ) Dust Glucan Jobs ordered by mean endotoxin level (by season) 0.1 1 10 100 1000 control operator pitman supervisor electr./millwright pellet plant op distributor/bintop sheetmetal mech basemt/gall./annex cleaner fl.op sweeper endotoxin (GM), ng/m3 Aug-Oct Jan-Mar Endotoxin and Glucan Content in dust Endotoxin Glucan job groups • Sweeper • Cleaner Fl. Op • Sheet Metal ↑ ↑ ↑ - - ↓ tasks • sweeping • maintenance in elevator • time outside ↑ ↑  - - - ↑ season/ weather • winter ↓ - elevator • company A • company B • company C ↑ - - ↓ ↓ Model R2 0.43 0.16 Conclusions: is dust level a good surrogate for other biologically active grain components? • Glucan: • dust a poor surrogate - esp. at low dust levels • Endotoxin: • chronic effects studies: dust a reasonable surrogate, if … seasonal changes in endotoxin are cyclic (needs to be evaluated) • acute effects studies: dust a poor surrogate

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