British journal of industrial medicine
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A follow-up study of lung function tests and dust measurements was undertaken in ginnery workers employed in five ginning factories. Respiratory symptoms and respiratory function tests (FEV1 and FVC) were first recorded in 1967 on a total of 382 workers (323 permanently employed ginnery workers, 35 seasonal farfara workers, and 24 fire brigade men as controls). In 1969 after a six-month break from ginning before the start of the season, a follow-up study of lung function tests was undertaken on 96% of the same workers (306 ginnery workers, 35 farfara, and 24 fire brigade men). ⋯ The overall differences were statistically significant. There was a marked trend showing a positive association between prevalence of byssinosis and level of cotton dust concentration in the factories. The correlation between dust levels and the prevalence of byssinosis was nearly perfect when the time factor was included.