Long-term occupational exposure to cotton dust containing endotoxin is associated with chronic respiratory symptoms and a more rapid decline in forced expiratory volume in 1 sec (FEV1), but the mechanisms of endotoxin-related effects remain unclear. Shi et al. examined associations between recent and past airborne endotoxin exposures, longitudinal change in FEV1, and respiratory symptoms in a cohort of Chinese cotton textile workers. This prospective cohort study followed 447 cotton textile workers from 1981 to 2006 at approximately 5-year intervals. The authors found that past cumulative exposure to endotoxin was associated with reduced FEV1 only among retired cotton workers. Among all cotton workers, past exposure was associated with reduced FEV1 only among those hired