Fig. 4

The plots of the overall effect of \(\text {PM}_{10}, \text {SO}_2, \text {NO}_2, \text {O}_3\), and CO on COPD. When all exposure factors are fixed at the 50th percentile (median), these are the relative exposure-factor estimates as they change to the 25th, 30th, \(\ldots\), 70th, and 75th percentiles.