A probabilistic approach to quantitatively assess the inhalation risk for airborne endotoxin in cotton textile workers

Endotoxin, a component of gram-negative bacterial cell walls, is a proinflammatory agent that induces local and systemic inflammatory responses in normal subjects which can contribute to the risk of developing asthma and chronic obstructive lung diseases. A probabilistic approach linking models of exposure, internal dosimetry, and health effects were carried out to quantitatively assess the potential inhalation risk of airborne endotoxin for workers in cotton textile plants. Combining empirical data and modeling results, we show that the half-maximum effects of the endotoxin dose (ED50) were estimated to be 3.3 × 105 (95% confidence interval (CI): 1.9-14.7 × 105) endotoxin units (EU) for the blood C-reactive protein (CRP) concentration, 1.1 × 105 (95% CI: 0.6-1.7 × 105) EU for the blood polymorphonuclear neutrophil (PMN) count, and 1.5 × 105 (95% CI: 0.4-2.5 × 105) EU for the sputum PMN count. Our study offers a risk-management framework for discussing future establishment of limits for respiratory exposure to airborne endotoxin for workers in cotton textile plants.