We analyzed pulmonary function test results and respiratory questionnaire information on 2287 workers collected in medical surveillance programs of 21 knitting plants using cotton yarn. Testing and questionnaires had been administered by a private consulting firm (ELB Associates, Inc. of Chapel Hill, NC) and conformed to the requirements in the current OSHA Standard for Occupational Exposure to Cotton Dust.

Prevalence of byssinosis was less than 2% and chronic cough, chronic phlegm, and dyspnea were no more common in the knitting workers than reported for workers in non-dusty trades. Linear regression analysis showed the estimated decline with age of the forced expiratory volume in one second (FEV(1)) for non-smoking knitting workers to be similar to predicted values.

An estimate of the total years worked in knitting trades was obtained for approximately 60% of the workers from plant management. Categorical analysis showed a consistent trend for reduction of FEV(1) as percent of predicted with increasing packyears of cigarette consumption, but no consistent association of reduction in FEV(1) with increasing years of knitting work. Linear regression models fitted to the data showed increasing pack-years of cigarette smoking to be significantly associated with decreasing FEV(1), but years of knitting work was not.

The mean FEV(1) declined slightly over the workshift for all smoking groups. The magnitude of the decline tended to be larger for workers in knitting rooms with higher dust concentrations measured with vertical elutriators. However, this was not a consistent finding for all smoking categories or for other indices of cotton dust exposure.

In these data chronic loss of lung function and increased prevalence of respiratory symptoms were clearly associated with cigarette smoking. Findings suggested that acute declines in FEV(1) over the workshift were associated with knitting room dust concentrations, but there was little evidence for a significant chronic effect of knitting room work on the respiratory health of the workers.