Daily exceedance concentration hours: A novel indicator to measure acute cardiovascular effects of PM_(2.5)in six Chinese subtropical cities

摘要

Background: Daily mean concentration cannot fully address the hourly variations of air pollution within one day. As such, we proposed a new indicator, daily exceedance concentration hours (DECH), to explore the acute cardiovascular effects of ambient PM(2.5 ()particles with aerodynamic diameters less than 2.5 mu m). The DECH in PM2.5 was defined as daily total concentration-hours 25 mu g/m(3).