Byssinosis: a follow-up study of workers exposed to fine grade cotton dust.

A follow-up study was made in a group of cotton workers processing fine grade cotton fibres. Respiratory symptoms and ventilatory capacity were first recorded in 1962 and later in 1971. In 1962, 20 men and 23 women were examined whereas in 1971 only 15 of the men and 13 of the women were still in the mill. In 1962 no case of byssinosis was recorded. The prevalence of chronic cough and chronic bronchitis was higher among men than women. In 1971 the incidence of byssinosis was 20% in men and 23% in women and the prevalence of all other respiratory symptoms had also increased. In men there was a significant mean decrease of the forced expired volume in 0·75 sec (FEV0.75) over the shift both in 1962 (P<0·05) and in 1971 (P<0·01). In women the mean acute decrease of FEV0.75 over the shift in 1962 was not statistically significant (P>0·05), but in 1971 it was (P<0·05). The mean acute reductions of FEV0·75 were considerably higher in 1971 than in 1962. In byssinotics these changes were considerably higher than in non-byssinotics. The chronic effect on ventilatory capacity of exposure to fine cotton dust was not observed in this study.