Objectives-To study the prevalence of byssinosis and other respiratory abnormalities in workers exposed to cotton dust in Guangzhou in two factories that processed purely cotton.

Methods-All the 1320 workers exposed were included.

The controls were 1306 workers with no history of occupational dust exposure.

Total dust and inhalable dust were measured by Chinese total dust sampler and American vertical elutriator respectively.

A World Health Organisation questionnaire was used.

Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were measured by a Vitalograph spirometer.

Results

The median inhalable dust concentrations ranged from 0.41 to 1.51 mg/m3 and median total dust concentrations from 3.04 to 12.32 mg/m. 3 The prevalence of respiratory abnormalities in the cotton workers were (a) typical Monday symptoms 9.0% ; (b) FEV1 fall by =5% after a shift 16.8% ; (c) FEV1 fall by =10% after a shift 4.2% ; (d) FEV1<80% predicted 6.1% ; (e) FEV1/FVC<75% 4.0% ; V) cough or phlegm 18.2% ; (g) chronic bronchitis 10.9% ; and (h) byssinosis, defined by (a) plus (b) 1.7%. With the exception of (d), most of the prevalences increased with increasing age, duration of exposure, and cumulative inhalable dust exposure.

No increasing trends of respiratory abnormalities were found for current total dust, inhalable dust, and cumulative total dust concentrations.