COTTON DUST AND ENDOTOXIN EXPOSURE-RESPONSE RELATIONSHIPS IN COTTON TEXTILE WORKERS

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Abstract
Endotoxin exposure has been implicated in the etiology of lung disease in cotton workers. We investigated this potential relationship in 443 cotton workers from 2 factories in Shanghal and 439 control subjects from a nearby silk mill. A respiratory questionnaire was administered and pre- and postshift forced expiratory volume (FVC) and flow in one second (FEV1) were determined for each worker. Multiple area air samples were analyzed for total elutriated dust concentration (range: 0.15 to 2.5 mg/m3) and endotoxin (range: 0.002 to 0.55 .mu.g U.S. Reference Endotoxin/m3). The cotton worker population was stratified by current and cumulative dust or endotoxin exposure. Groups were compared for FEV1, FVC, FEV1/FVC%, % change in FEV1 over the shift (.DELTA.FEV1%), and prevalences of chronic bronchitis and byssinosis, and linear and logistic regression models were constructed. No dose-response relationships were demonstrated comparing dust concentration to any pulmonary function or symptom variable. A dose-response trend was seen with the current endotoxin level and FEV1, .DELTA.FEV1%, and the prevalence of byssinosis and chronic bronchitis, except for the highest exposure level group in which a reversal of the trend was seen. The regression coefficients for current endotoxin exposure were significant (p < 0.05) in the models for FEV1 and chronic bronchitis but not in the models for .DELTA.FEV1% (i.e., acute change in FEV1) or byssinosis prevalence. The coefficient for dust level was never significant in the models. We conclude that exposure to increasing levels of airborne endotoxin is associated with an increased risk of pulmonary abnormalities among cotton workers, although those workers exposed to the highest levels may represent a "survivor population". The fact that we failed to show a significant relationship between exposure and acute change in FEV1 suggests that other etiologic factors may also be important.