Biomarkers of airway acidity and oxidative stress in exhaled breath condensate from grain workers

Rationale: Grain workers report adverse respiratory symptoms due to exposures to grain dust and endotoxin. Studies have shown that biomarkers in exhaled breath condensate (EBC) vary with the severity of airway inflammation. Objectives: The purpose of the study was to evaluate biomarkers of airway acidity (pH and ammonium [NH₄⁺]) and oxidative stress (8-isoprostane) in the EBC of grain workers. Methods: A total of 75 workers from 5 terminal elevators participated. In addition to EBC sampling, exposure monitoring for inhalable grain dust and endotoxin was performed; spirometry, allergy testing, and a respiratory questionnaire derived from that of the American Thoracic Society were administered. Measurements and Main Results: Dust and endotoxin levels ranged from 0.010 to 13 mg/m³ (median, 1.0) and 8.1 to 11,000 endotoxin units/m³ (median, 610) respectively. EBC pH values varied from 4.3 to 8.2 (median, 7.9); NH₄⁺ values from 22 to 2,400 μM (median, 420); and 8-isoprostane values from 1.3 to 45 pg/ml (median, 11). Univariate and multivariable analyses revealed a consistent effect of cumulative smoking and obesity with decreased pH and NH ₄⁺, and intensity of grain dust and endotoxin with increased 8-isoprostane. Duration of work on the test day was associated with decreased pH and NH₄⁺, whereas duration of employment in the industry was associated with decreased 8-isoprostane. Conclusions: Chronic exposures are associated with airway acidity, whereas acute exposures are more closely associated with oxidative stress. These results suggest that the collection of EBC may contribute to predicting the pathological state of the airways of workers exposed to acute and chronic factors.