Pulmonary function among cotton textile workers. A study of variability in symptom reporting, across-shift drop in FEV1, and longitudinal change.
A study of longitudinal changes in symptoms and across shift changes in pulmonary function in Chinese cotton textile workers was conducted as part of a longitudinal investigation of respiratory disease in textile workers in Shanghai, China. The original cohort included 447 textile workers, 232 females, in two cotton mills who were surveyed by a respiratory symptom questionnaire and spirometric testing before and after a work shift on the first day of the work week in 1981. Area air sampling for cotton dust and endotoxins was performed in the opening, cleaning, carding, drawing, roving, combing, and spinning departments. A followup survey which evaluated the same parameters was conducted in 1986. In both surveys, preshift values of 1 second forced expiratory volume (FEV1) and forced vital capacity (FVC) were compared with measured values in a population of silk yarn workers to obtain equations for predicting expected values. A total of 385 subjects, 197 females, mean age 36.9 years, participated in the followup survey. Median cotton dust exposures measured in the followup survey varied from 0.24 to 0.7mg/m3. Endotoxin concentrations ranged from 0.004 to 0.75 micrograms/cubic meter. The dust concentrations measured in both surveys were generally stable. The overall prevalence of chronic symptoms, around 33%, was similar in both surveys, except dyspnea which increased. Only 10% of the subjects consistently reported the same specific symptoms. Approximately 6.7% of the subjects who ever reported symptoms were inconsistent in their responses. Subjects who consistently reported specific symptoms exhibited accelerated decreases in FEV1 and FVC compared to those who never or inconsistently reported these symptoms. The highest reported rate of loss, -139 milliliter (ml) per year, occurred in four subjects who had byssinosis in both surveys. Comparison of subjects who had a greater than 5% cross shift decrease in FEV1 in both surveys with those who showed such a response in only one survey or did not show such a response at all indicated that they had the largest 5 year decreases in FEV1, -267ml versus -224 and - 180ml. The authors conclude that despite the pronounced survey to survey variability in responses, cotton textile workers who consistently report respiratory symptoms or experience across shift FEV1 decrements of 5% or greater appear to have an increased risk for lung function impairment.