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In order to evaluate chronic effects of long-term exposure to cotton dust on respiratory health, and the role of dust and endotoxin, longitudinal changes in lung function and respiratory symptoms were observed prospectively from 1981 to 2001 in 447 cotton textile workers, along with 472 silk textile controls. The results from five surveys conducted over the 20-yr period are reported, including standardised questionnaires, pre- and post-shift spirometric measurements, work-area inhalable dust sample collections and airborne Gram-bacterial endotoxin analysis. Cotton workers had more persistent respiratory symptoms and greater annual declines in forced expiratory volume in one second (FEV1) and forced vital capacity as compared with silk workers. After exposure cessation, in the final 5-yr period, the rate of FEV1 decline tended to slow in nonsmoking males, but not in nonsmoking females. Workers who reported byssinotic symptoms more persistently suffered greater declines in FEV1. Chronic loss in lung function was more strongly associated with exposure to endotoxin than to dust. In conclusion, the current study suggests that long-term exposure to cotton dust, in which airborne endotoxin appears to play an important role, results in substantial adverse chronic respiratory effects.

To evaluate chronic loss of lung function in cotton dust-exposed workers, a 5-yr follow-up study was performed in Shanghai, China from 1981 to 1986. Workers at a nearby silk thread manufacturing mill were used as a control population. There were 384 cotton textile workers restudied from an original group of 446, and 403 silk workers restudied from the original 468. The presence of byssinosis among retested cotton workers at the time of first survey was 7.3%. The prevalence of byssinosis was 9.7% at the initial survey among those lost to follow-up. No byssinosis was found among control subjects. The mean annual decline in FEV1 was 39.5 ml among cotton workers and 30.6 ml for silk workers (p < 0.05). The greatest annual decrements were found among smoking cotton workers, but nonsmoking cotton workers also lost lung function at a faster rate than silk nonsmokers (annual loss = 33.3 ml versus 24.4 ml, respectively). Autoregressive modeling revealed that after adjustments for age, sex, height, and smoking, cotton dust exposure was significantly associated with decline in FEV1. Moreover, across-shift drop of 5% or more at the time of first survey was predictive of 5-yr decline in FEV1. Cotton workers who had an acute response (5% or greater drop in FEV1 at the time of first survey) suffered a 57.0 ml/yr FEV1 drop compared with a 35.1-ml drop among cotton workers with less acute response at baseline (p < 0.01). Silk workers with or without 5% across-shift drops had similar annual rates of decline (-33.8 ml and -36.1 ml, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Longitudinal variability in respiratory responses, including symptom reporting and across-shift change in ventilatory function, were examined in relation to long-term loss of ventilatory function in a group of 447 cotton textile workers in Shanghai, China. The study used a standardized respiratory questionnaire and standardized spirometric testing before and after a work shift on the first day of the workweek. Prediction equations for FEV1 were generated from a group of silk textile workers from the same city. Environmental samples included both vertical elutriated cotton dust and endotoxin levels. There was considerable variability in symptom reporting between the baseline and 5-year follow-up survey for all symptoms. However, subjects who consistently reported symptoms had a significantly accelerated 5-year loss in FEV1 compared with those who never reported symptoms. Subjects with symptoms of chest tightness or dyspnea at one survey lost FEV1 at a rate intermediate between the never or both groups. Moreover, subjects with an across-shift change in FEV1 of more than 5 percent at both surveys had the greatest loss in FEV1 over 5 years (-267 ml) when compared with one-time responders (-224 ml), and nonresponders (-180 ml), though the differences were not significant. Workers with chest tightness and chronic bronchitis in both surveys were overrepresented in the high dust and endotoxin areas. Our results indicate that even with substantial survey-to-survey variability in responses, there is important information contained in both questionnaires and across-shift spirometry. Among cotton workers, consistent responders to either symptom questionnaire or across-shift FEV1 decrements of > or = 5 percent appear to be at increased risk for lung function impairment.

The prevalence of byssinosis and nonspecific respiratory symptoms was studied in 887 textile workers with at least two years of employment in two cotton mills and one silk mill in Shanghai, the People's Republic of China. A standardized respiratory questionnaire was used, and environmental sampling was performed with vertical elutriators and colorimeter grading. Eight percent of the cotton textile workers complained of byssinosis. The reports of byssinosis were mostly mild (grade 1/2), more prevalent among women, and unrelated to duration of employment or elutriator dust levels. Nonspecific respiratory symptoms were significantly more prevalent among cotton textile workers than silk workers. After adjustment for age, gender, and smoking in logistic regression models, the odds ratios for the effect of working in cotton textile mills on chronic bronchitis, chronic cough, and frequent chest illness were 3.3, 2.9 and 4.7, respectively. Although none of the symptoms were related to current dust levels, the range of exposures was narrow, and information was only available on current levels of cotton dust. This study represents the first respiratory survey of the textile industry in China using diagnostic criteria similar to that used in the United States and England; it defines a cohort for prospective investigation.

A properly designed respiratory disease monitoring and surveillance program for the effects of cotton dust uses tools similar to those used clinically but provides a different focus--the potential for disease prevention in individuals and the control of excess exposures in groups. Both surveillance and monitoring require the use of standard instruments (questionnaires and pulmonary function equipment) with careful attention to equipment calibration and standard methods for administering tests. Monitoring focuses on the individual to identify early evidence of disease and to detect those subjects who are susceptible even under usually well controlled exposure circumstances. Surveillance is successful when designed to collect information at regular intervals (based on type and level of exposure and previously measured response) and the results are interpreted according to reasonably rigorous criteria. A major additional component is the examination of surveillance results according to groups based on job, exposure, work tenure, and other risk factors (e.g., smoking).

Characteristics of subjects with nonreproducible lung function tests (test failures) are described in two studies of occupational respiratory disease. According to current guidelines for spirometry, subjects with test failure are excluded from analyses of epidemiologic pulmonary function data. Among 415 Chinese cotton textile workers, the prevalence of byssinosis was 5.8% for subjects with repeatable tests and 13.3% for subjects with test failure. In regression analysis, the estimate of the association between cotton dust exposure and FEV1 decreased when subjects with test failure were excluded. In a second cohort of 378 asbestos-exposed machinists, the prevalence of chronic bronchitis was significantly greater among those with test failure. Considering only subjects with repeatable measurements, FEV1 was lower among textile workers with byssinosis and machinists with chronic bronchitis than among their asymptomatic coworkers. This suggests that, on average, subjects with poor test performance had lower (unobserved) FEV1 values, and therefore that the exclusion of subjects with test failure may cause selection bias.

Byssinosis, a lung disease caused by cotton dust, has been the subject of recent controversy. Debates over the nature of the disease, possible interactions with cigarette smoking, and the proposed reevaluation of the cotton dust standard by the Occupational Safety and Health Administration have tended to overlook the plight of affected workers and to obscure the most effective means for preventing the disease. The present lack of definitive information is no reason for inaction, nor for depriving disabled workers of adequate financial compensation. In this respect, byssinosis is no different from other public health hazards for which action must often be taken on the basis of incomplete evidence.

Epidemiologic approaches to improved understanding of the several reactions observed in cotton processors began in 1955 with Schilling's symptom classification of Monday-morning chest tightness. To date, epidemiologic studies have identified the importance of increasing years of exposure to the development of both specific and nonspecific chronic respiratory symptoms and of acute change in pulmonary function. The few longitudinal studies suggest similar associations with accelerated loss of pulmonary function. Respirable dust level has been associated, cross-sectionally, with symptoms and with acute function change, but studies have not yet been made with sufficient prospective collection of both exposure and health effects data to estimate accurately the association of continued exposure with accelerated loss of lung function or development of disability. Furthermore, there has been very limited field study comparing exposure to respirable dust distinguished from exposure to endotoxin. With careful attention to features of study design and analytic plans, investigators can take advantage of simple technology to examine the fate of the acute responder, the potential for recovery if exposure is reduced or ceased, and the long-term dose response relationship between different cumulative measures of exposure and chronic disease.

Pulmonary function tests were performed pre and post workshift on 887 textile workers with at least two years of employment in two cotton mills and one silk mill in Shanghai, the People's Republic of China. Environmental sampling was performed with vertical elutriators, and pulmonary function was performed with standardized techniques. Cotton textile workers were found to have greater across-shift decrements in forced expiratory volume in 1 s (FEV1.0) than silk workers. Increasing duration of exposure resulted in increasing acute decrements in FEV1.0, although significant acute decrements were found in workers with less than five years of exposure. The acute changes in FEV 1.0 were noted in both symptomatic and asymptomatic cotton workers, though the difference between the across-shift change in FEV1.0 (delta FEV1.0%) of the byssinotics and nonbyssinotics increased as work duration increased. There was no difference in preshift FEV1.0 between the cotton and silk workers, but several selection factors likely influenced the observations.