I’ve written before about the developing science regarding the impacts of PM2.5 emissions. Short version – they’re bad for you. They’re even worse than we thought, and there’s increasing evidence that they cause a lot of harm at concentrations below the National Ambient Air Quality Standard of 12 ug/m3. 
The most recent report comes from Canada, which is particularly useful in measuring the impact of low concentrations of PM2.5 precisely because PM2.5 concentrations are relatively low there. … More