Characteristics of former and two current worker groups constituting Subcohort 1 before interventions and Subcohort 2 after interventions began to lower exposure.

ap-values for tests of equality of medians or prevalence comparing Former Workers and Current Workers employed in 2000.
bp-values for tests of equality of medians or prevalence comparing Subcohort 1 and Subcohort 2.
cPositive response to "Do you usually have a cough?"
dPositive response to "Do you get short of breath walking with people of your own age on level ground?"
ePulmonary function test (PFT) interpretation of each worker's initial test.