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Acid-base equilibrium in exhaled breath condensate of grain elevator workers Do, Ron


Introduction: Workers in the grain industry have been reported to have adverse respiratory symptoms, primarily due to occupational exposure to grain dust. Exhaled breath condensate (EBC) may be a viable method in field studies to sample secretions of the lower airways. It is suggested that these secretions can predict inflammatory responses to inhaled irritants, such as grain dust. Studies have reported that the acid-base equilibrium in EBC varies with the severity o f airway inflammation. The purpose of the present study was to measure EBC pH and ammonium to assess the acid-base equilibrium of the airways in grain elevator workers. Methods: EBC collection was performed using commercially available equipment. Methodological issues pertaining to the collection, storage, and analysis of EBC were evaluated to produce a standard procedure suitable for our laboratory. The field component consisted of sampling EBC from workers employed at terminal elevators in the port of Vancouver. In addition, personal exposure monitoring to inhalable grain dust and endotoxin, completion of a respiratory questionnaire, spirometry and allergy testing were also performed, as part of a larger cross-sectional grain study. Results: 76 workers participated. EBC pH values varied from 4.3 to 8.2 (median: 7.94); ammonium values from 22 to 2384 μM (median: 420.4). Geometric mean dust and endotoxin levels were: 0.9 mg/m3 (GSD: 4.0) and 435 EU/m3 (GSD: 4.9) respectively. pH and ammonium were moderately correlated (1=0.53). Multivariable analysis showed that pH was lower in association with current smoking intensity and obesity, yet higher in current atopics. Lower pH was associated with duration of exposure on the study day before EBC collection and with working in one work area (seed/pellet plant), but not with measured grain dust or endotoxin exposure concentration. Lower ammonium was associated with chronic smoking intensity, duration of exposure on the study day, years of employment in the industry, and working in the seed/pellet plant; but significantly higher in association with grain dust measured on the study day. Conclusion: The collection of EBC is feasible in field studies. EBC pH and ammonium may be useful to measure airway inflammation related to acute and chronic occupational exposures.

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