PM2.5 and all-cause mortality

The US EPA and the WHO claim that PM2.5 is causal of all-cause deaths. Both support and fund research on air quality and health effects. WHO funded a massive systematic review and meta-analyses of air quality and health-effect papers. 1,632 literature papers were reviewed and 196 were selected for meta-analyses. The standard air components, particulate matter, PM10 and PM2.5, nitrogen dioxide, NO2, and ozone, were selected as causes and all-cause and cause-specific mortalities were selected as outcomes. A claim was made for PM2.5 and all-cause deaths, risk ratio of 1.0065, with confidence limits of 1.0044 to 1.0086. There is a need to evaluate the reliability of this causal claim. Based on a p-value plot and discussion of several forms of bias, we conclude that the association is not causal.