Fig. 2
Causal dose-response relations between chronic exposures to PM2.5, O3, NO2 and the relative risk of mortality. The relative risks of mortality and 95% CIs are shown for higher decile groups against the lowest decile group (reference). The exposure concentration corresponding to each effect estimate represent the average concentration within the decile group. Vertical lines represent current national air quality standards for annual PM2.5 (12 μg·m−3) and annual NO2 (53 ppb). There is no long-term standard for O3