A survey of respiratory disease in cotton operatives. II. Symptoms, dust estimations, and the effect of smoking habit.

48-53. In association with a survey of cotton workers dust levels were measured in 11 of the mills. Levels varied from 1·15 mg/m to 4·8 mg/m excluding fly. Analysis of the survey of workers in relation to the dust levels showed an increase in abnormal symptoms and a greater reduction in ventilatory function in those exposed to the higher dust concentrations. No such relationship was found between dust concentration and prevalence of bronchitic symptoms. Smokers showed a higher frequency of byssinotic symptoms and a greater loss of ventilatory function than non-smokers at all levels of dust exposure. The correlation between dust levels and the frequency of byssinotic symptoms and the loss of ventilatory function was increased by including a time factor. By expressing the dust exposure as mg years/m it can be predicted that approximately 10% of subjects exposed to 0·5 mg/m of dust for 40 years will have the symptoms of byssinosis.