Exposure-related Declines in the Lung function of Cotton Textile Workers: Relationship to Current Workplace Standards

Abstract

Abstract To evaluate the effectiveness of the current workplace standards in preventing chronic health effects from cotton dust exposure, a 5-yr longitudinal study of a large multimill population of cotton textile and synthetic process workers, employed at a major U.S. textile company, was conducted. To control for and assess the effect of type of work area on annual change in lung function, we limited the analysis to those 1,817 subjects who, throughout their textile work history at the company, worked exclusively in cotton yarn manufacturing or slashing and weaving, or in synthetic textile mills. The expected effect of smoking on average annual change in lung function was demonstrated for both cotton and synthetic workers. Despite lower overall dust exposure, cotton yarn workers exhibited steeper annual declines in lung function than did workers in slashing and weaving; this difference persisted within each smoking category, indicating a dust potency effect. There were mill differences in annual change in lung function among cotton workers, potentially masking an exposure effect. A smoking-work area interaction persisted after adjusting for mill differences, with the largest annual declines observed in cotton yarn workers who smoke. A significant dose-response relationship was seen in cotton yarn manufacturing between annual declines in FEV1, FVC, and FEF25–75 and average exposure by mill, and the larger declines were found in mills using the highest percentage and lowest grade of cotton. Synthetic textile workers had larger declines than did cotton textile workers, which were not explained by smoking or duration of employment. Unrecognized and unmeasured causative exposures or selection bias could explain this result. The current cotton dust standards appear to protect against the chronic effects of exposure in smokers and nonsmokers in slashing and weaving. No dose-response relationship was noted, and the observed mean annual decline in FEV1 and FVC for these workers was 25 ml/yr or less. For yarn manufacturing workers a dose-response relationship was noted. For nonsmokers in this area, the observed mean annual decline in FEV1 and FVC was similar to that reported for workers in slashing and weaving, indicating the absence of a significant health effect of existing exposures; at the current dust standard for yarn manufacturing, however, the dose-response model predicted slightly steeper declines for these workers compared with workers in slashing and weaving. For current smokers in yarn manufacturing, the synergistic effect of exposure and current smoking produced accelerated annual declines in FEV1. These results suggest that, in the short term, smokers should be restricted from working in yarn manufacturing areas, and in the long term, the feasibility of lowering respirable dust levels to provide protection for all yarn manufacturing workers should be evaluated.