The pattern of association between all-cancer mortality risk and long-term exposure to PM2.5 (μg/m3). The pattern of association between all-cancer mortality risk and long-term exposure to PM2.5 (μg/m3). Solid line (95% CI: dashed line) based on fully adjusted model in Table 1, with natural spline on 2 degrees of freedom. The marks above the x-axis show the measurements with the crowdedness, indicating the distribution of PM2.5 concentration. Chit Ming Wong et al. Cancer Epidemiol Biomarkers Prev 2016;25:839-845 ©2016 by American Association for Cancer Research