Ventilatory function of factory workers exposed to tea dust.

A cross-sectional study was conducted in order to determine the prevalence of respiratory symptoms and the effect on ventilatory capacity in workers exposed to tea dust for at least five years during the sifting process of tea manufacture compared to a control group of field workers who were not exposed to tea dust previously. Fifty-three subjects each in the study and control groups were matched for age, sex, ethnic group and height. Prevalence of chronic respiratory symptoms was obtained by questionnaire. Spirometric measurements included forced vital capacity (FVC), forced expiratory volume in the first second (FEV1.0) and forced mid-expiratory flow rate (FEF 25-75%). The study group had a chest radiograph. The odds ratio for any chronic respiratory symptom was 11.6 (95% confidence interval [CI] = 3.7-39.4) in the study group. Mean values for the spirometric tests were lower in the study group; the differences in FEV 1.0 and FEF 25-75% were significant. Tuberculosis was not found in the study group, while one subject (2.4%) had radiological evidence of bronchiectasis. It may therefore be concluded that chronic tea dust exposure causes increased prevalence of respiratory symptoms and a significant degree of small airways obstruction.