Adaptation to Occupational Exposure to Moderate Endotoxin Concentrations: A Study in Sewage Treatment Plants in Germany

Acute or chronic inhalation of endotoxin may lead to changes of lung function and inflammatory markers in the airways. Adaptation to workplace exposure may be possible. In this study, we investigated the possible difference in inflammatory markers assessed in nasal lavage fluid (NALF) in chronical exposure compared to voluntary subjects exposed acutely to endotoxin. We sought to define the variability of inflammatory markers in NALF and the dose-related changes after moderate exposure in naive subjects. Endotoxin exposure (4–1039 EU/m3) resulted from routine work during one shift in sewage treatment plants. Subjects were matched to pairs (8 workers escorted by 10 students). Inflammatory markers were investigated before, directly after, and 16 h after the shift end. Additional NALF samples were collected in students without any specific exposure after 3 days. In NALF, total cell count, and interleukin (IL)-8 and IL-1β concentrations were significantly higher in workers than in students at all times pointing to workplace-related long-lasting exposure resulting in adaptation. However, concentration of inflammatory markers without specific exposure in students showed a great variability, covering the whole range of values recorded in the workers. The findings of this study make us to recommend a repeated assessment of inflammatory markers in healthy volunteers before the investigation of exposure-related changes and a sample size adequate for statistical analysis.