Preprocessing cotton to prevent byssinosis.

237-247. A fundamental approach of cleaning or deactivating cotton prior to manufacturing has long been advocated to prevent byssinosis, but no trial had been conducted to test the feasibility of such an approach. In the study described, it was possible to be directed by both biological observations and the results of manufacturing trials. An exposure chamber was built in a cotton textile mill which had been previously studied as part of a large cross-sectional survey. The chamber was provided with an independent air conditioning system and a carding machine which served as a dust generator. Sixteen subjects, who had shown reductions in expiratory flow rate with exposure to cotton dust, were chosen to form a panel for exposure to raw cottons and cottons which had been preprocessed by heating, washing, and steaming. Indicators of effects were symptoms of chest tightness and/or dyspnoea, change in FEV, and fine dust levels over 6 hours of exposure. Exposure of the panel to no cotton dust resulted in no change in FEV and served as the control for subsequent trials. Exposure to strict middling cotton resulted in a byssinosis symptom prevalence of 22%, a significant decrement in FEV of 2·9%, and a fine dust level of 0·26 mg/m. Exposure to strict low middling cotton resulted in a byssinosis symptom prevalence of 79%, a decrement in FEV of 8·5%, and a fine dust level of 0·89 mg/m. Oven heating strict low middling cotton resulted in a byssinosis symptom prevalence of 56% and a relatively greater drop in FEV of 8·3% for 0·48 mg/m of fine dust. Washing the strict low grade cotton eliminated detectable biological effects with a symptom prevalence of 8%, an increase of 1·4% in FEV, and a dust level of 0·16 mg/m, but the cotton proved to be difficult to process. As an alternative method, strict low middling cotton was steamed initially in large dyeing vats, on a conveyor, in an autoclave, and in a modified yarn dyeing apparatus or pipe' steamer. Of these methods, autoclaving cotton was the most successful, reducing symptom prevalence to 8%, the drop in FEV to 0·4%, and the dust level to 0·23 mg/m. Development of a high capacity cotton steamer based on the small pipe' steaming model resulted in a symptom prevalence of 8%, a decrement in FEV of 0·8%, and a mean dust level of 0·27 mg/m. Regressions calculated from raw and high capacity steaming trials indicate that at low dust levels steamed cotton dust was roughly one half as biologically active as raw cotton dust.