THE ROLE OF ENDOTOXIN IN GRAIN DUST-INDUCED LUNG-DISEASE

To identify the role of endotoxin in grain dust-induced lung disease, we conducted a population-based, cross-sectional investigation among g rain handlers and postal workers. The study subjects were selected by randomly sampling all grain facilities and post offices within 100 mil es of Iowa City. Our study population consisted of 410 grain workers a nd 201 postal workers. Grain workers were found to be exposed to highe r concentrations of airborne dust (p = 0.0001) and endotoxin (p = 0.00 01) when compared with postal workers. Grain workers had a significant ly higher prevalence of work-related (cough, phlegm, wheezing, chest t ightness, and dyspnea) and chronic (usual cough or phlegm production) respiratory symptoms than postal workers. Moreover, after controlling for age, gender, and cigarette smoking status, work-related respirator y symptoms were strongly associated with the concentration of endotoxi n in the bioaerosol in the work setting. The concentration of total du st in the bioaerosol was marginally related to these respiratory probl ems. After controlling for age, gender, and cigarette smoking status, grain workers were found to have reduced spirometric measures of airfl ow (FEV(1), FEV(1)/FVC, and FEF(25-75)) and enhanced airway reactivity to inhaled histamine when compared with postal workers. Although the total dust concentration in the work environment appeared to have litt le effect on these measures of airflow obstruction, higher concentrati ons of endotoxin in the bioaerosol were associated with diminished mea sures of airflow and enhanced bronchial reactivity. Our results indica te that the concentration of endotoxin in the bioaerosol may be partic ularly important in the development of grain dust-induced lung disease .