Figure 1.

Annualized changes in FEV₁ (ml/yr) over 15 yr associated with repeated cross-shift drops at the first three surveys among 408 cotton and 417 silk workers, estimated by multiple linear regression models, in which age, height, smoking status, and sex were adjusted. ΔFEV₁ drop was defined as ΔFEV₁ < 0. P = 0.007 and P = 0.0001 for cotton workers with two and three drops, respectively, in comparison with the cotton reference group (without a drop); P > 0.05 for silk workers with two or three drops in comparison with the silk reference group. Solid squares, silk; solid diamonds, cotton.