depending on the specific PM2.5 measure used.
Results were similar although slightly attenuated in the fully adjusted model,
which included an additional term for mean county-level residential radon concentrations.
In the fully adjusted model, a HR of 1.15 (95% CI, 0.99–1.35) was observed for lung cancer mortality associated with each 10 μg/m3 increase in PM2.5 (1979–1983) concentrations. A significant positive association (HR per each 10 μg/m3 = 1.27; 95% CI, 1.03–1.56) was observed for PM2.5 (1999–2000). Figure 1 presents adjusted HRs (95% CIs) for lung cancer mortality according to categorical indicators of PM2.5 (1999–2000) concentrations. No association was observed between PM2.5 and mortality from nonmalignant respiratory disease overall (see Table E1 in the online supplement). There was no evidence that the proportional hazards assumption was violated (P > 0.05).