The effect of air pollution on the length of survival of respiratory cancer patients is biologically plausible. Long-term exposure to air pollution has been extensively linked with mortality and cancer-specific mortality [19-23]. Previous studies also suggests that air pollution, especially PM2.5 and O3, has been associated with early
mortality in susceptible populations with chronic condi- tions such as COPD, diabetes, heart failure, or myocar- dial infarction [24,25]. These results are consistent with the findings from this study. The biological mechanisms by which air pollution can impact the length of survival of respiratory cancer patients is still unclear. However, it is clear that the respiratory system is an organ that is most directly affected by air pollution which carries many types of toxic chemicals including those with car- cinogenic potential [26]. These pollutants could reach the wall of respiratory system and even into the blood and other organs, and induce systematic inflammation [27]. Respiratory cancer patients are at increased risk for