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No excess of obstructive airway disease was found in a group of 265 cotton gin workers when compared with other San Joaquin Valley agricultural workers. After an average of eight weeks' employment in San Joaquin Valley cotton gins, 125 workers showed no appreciable deterioration of pulmonary function compared with pre-employment measurements. In studies of pulmonary function during a workshift, cotton gin workers showed slightly greater mean decrements than control agricultural workers. These differences did not reach a level of statistical significance and were lower than those usually found in byssinosis. The unusual temporal pattern of employment in cotton gins in California precludes a simple approach to diagnosis by symptoms. No correlation was found in this study between symptoms of byssinosis and objective decrements in FEV1. The questionnaire as proposed by the Cotton Dust Standard was found to be of no value in detecting reactors in this study of gin workers.

In a previous study we found no significant effects of acute exposure to the cotton gin environment on FEV 1 in San Joaquin Valley gin workers compared with concurrent control subjects, nor was there an excess of obstructive lung disease among the same gin workers. The present study looked at the mean annual decline in FEV 1 , FEV 1 /FVC, and FEF25-75% in San Joaquin Valley cotton gin workers vs concurrent control subjects over four years. The FEV 1 of gin workers completing all four years of the study declined 27.3 ml vs 35.5 ml in control subjects (p = 0.37); FEV 1 /FVC declined 0.21 percent in gin workers and 0.23 percent in control subjects (p = 0.86); FEF25-75% declined 0.058 L/s in gin workers and 0.066 L/s in control subjects (p=0.68). Also, the mean annual rate of change of FEV 1 was less among the gin workers who did not complete all four years than the gin workers completing all four years. The presence of "byssinosis" symptoms did not significantly influence the results. This prospective, longitudinal study failed to find any detrimental effect of the cotton gin environment on the rate of decline of FEV 1 , FEV 1 /FVC, and FEF25-75%. This result was independent of "byssinosis" symptoms and the effect of "dropouts."