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Cross-shift Airway Responses and Long-Term Decline in FEV₁ in Cotton Textile Workers

¹ Department of Environmental Health (Environmental and Occupational Medicine and Epidemiology Program), Harvard School of Public Health, Boston, Massachusetts; ² Department of Community and Family Medicine, The Chinese University of Hong Kong School of Public Health, Hong Kong, China; ³ Shanghai Putuo District People's Hospital, Shanghai, China; and ⁴ Pulmonary and Critical Care Unit, Massachusetts General Hospital, and Department of Medicine, Harvard Medical School, Boston, Massachusetts

Correspondence and requests for reprints should be addressed to David Christiani, M.D., M.P.H., Harvard School of Public Health, 665 Huntington Avenue, Building I-1407, Boston, MA 02115. E-mail: dchris{at}hsph.harvard.edu

Rationale: Acute airway response, measured as cross-shift change in FEV₁, to cotton dust may lead to subsequent chronic loss of lung function in exposed workers.

Objectives: To explore the association between the magnitude and frequency of cross-shift change and chronic loss of FEV₁.

Methods: Four hundred eight cotton workers and 417 silk workers from Shanghai textile mills were observed prospectively for 20 years, with cross-shift measurements at baseline and follow-up surveys at approximate 5-year intervals. To account for repeated measures of 5-year change, generalized estimating equations were used to estimate the relationship between the magnitude of cross-shift change in FEV₁ (FEV₁) and subsequent 5-year annualized change. Linear regression models were used to examine the association between the number of drops in cross-shift FEV₁ (FEV₁ < 0) and annualized change over the entire study period.

Measurements and Main Results: Exposure to cotton dust was associated with a 10 ml/year decrement in 5-year annualized FEV₁ decline. In addition, every 10 ml in FEV₁ drop was associated with an additional 1.5 ml/year loss in annualized FEV₁ decline. The association between the frequency of drops and annualized decline was stronger for cotton workers than for silk workers over the entire study period.

Conclusions: Cotton workers had larger and more frequent drops, as well as excessive chronic declines in FEV₁, than did silk workers. The magnitude and frequency of cross-shift drops were associated with chronic loss in FEV₁ over the entire 20-year period examined.

Key Words: cross-shift FEV₁ change • chronic changes in lung function • cotton textile workers • cotton dust • occupational lung disease

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject There is a strong relationship between acute airway response and chronic loss in FEV1 in cotton textile workers. Chronic airway obstruction is most likely a consequence of both long-term exposure and repeated acute airway responses. What This Study Adds to the Field Cotton workers had larger and more frequent drops, as well as excessive chronic declines in FEV1, than did silk workers. The magnitude and frequency of cross-shift drops were associated with chronic loss in FEV1 over the entire 20-year period examined.