Is chronic airway obstruction from cotton dust exposure reversible?
BACKGROUND
Exposure to cotton dust is known to cause chronic airway obstruction, but there is little information on whether the obstructive impairment is reversible after the exposure stops.


METHODS
Longitudinal changes in lung function were evaluated among 429 cotton textile workers and 449 silk workers in Shanghai, China, beginning in 1981. Both active and retired workers were tested every 4 to 6 years for 15 years.


RESULTS
Overall, cotton workers had greater annual declines in forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC). Compared with active workers, retired cotton workers had lower annual loss of FEV1, although the retired workers had a greater loss during their active employment than the currently active workers. No such trends were detected in silk workers. Annual declines in FEV1 in retired cotton workers were smaller with increasing time since retirement. Multivariate analysis showed that retirement was a substantial contributing factor for improved FEV1 and FVC in the cotton workers, especially among those who did not smoke. Correspondingly, remission of airflow obstruction, defined as a ratio of FEV1 and FVC of less than 70%, was more common in retirees than in the active workers, and more common in nonsmokers than in smokers.


CONCLUSIONS
Chronic airway obstruction related to long-term exposure to cotton dust may be partially reversible after the exposure ceases, although lung function does not return to the level found in unexposed workers.
Department of Environmental Health (Occupational Health Program), Harvard School of Public Health, Boston, Massachusetts 02115, USA.
Xiao-Rong
XR
Wang
Hong-Xi
HX
Zhang
Bi-Xiong
BX
Sun
He-Lian
HL
Dai
Lei-Da
LD
Pan
Ellen A
EA
Eisen
David H
DH
Wegman
Stephen A
SA
Olenchock
David C
DC
Christiani
D000328:Adult; D000402:Airway Obstruction / Q000209:etiology*; D015331:Cohort Studies; D032561:Cotton Fiber; D004391:Dust; D005260:Female; D006801:Humans; D007221:Industry; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016273:Occupational Exposure / Q000009:adverse effects* / Q000706:statistics & numerical data; D012129:Respiratory Function Tests; D012907:Smoking; D013997:Time Factors
D004391:Dust