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 PM2.5 (particles with aerodynamic diameters less than 2.5 μm). The DECH in PM2.5 was defined as daily total concentration-hours > 25 μg/m3. Methods A generalized additive model with a quasi-Poisson link was applied to estimate the associations between day-to-day variation in PM2.5 DECH and day-to-day variation in cardiovascular mortality in six subtropical cities in Guangdong Province, China. Results The analysis revealed significant associations between PM2.5 DECHs and cardiovascular mortality. A 500 μg/m3 ∗ h increase in PM2.5 DECHs at lag03 was associated with an increase of 4.55% (95% confidence interval (CI): 3.59%, 5.52%) in cardiovascular mortality, 4.45% (95% CI: 2.81%, 6.12%) in ischemic cardiovascular mortality, 5.02% (95% CI: 3.41%, 6.65%) in cerebrovascular mortality, and 3.00% (95% CI: 1.13%, 4.90%) in acute myocardial infarction mortality. We further observed a greater mortality burden using PM2.5 DECHs than daily mean PM2.5 (6478 (95% CI: 5071, 7917) VS 5136 (95% CI: 3990, 6305)). Conclusion This study reveals that PM2.5 DECH is one important exposure indicator of ambient PM2.5 to measure its cardiovascular mortality effects in Pearl River Delta region; and that using daily mean concentration could under-estimate the mortality burden compared with this new indicator.
Bibliographical noteFunding Information:
This study is funded in part by supported by the Medical Science and Technology Research Foundation of Guangdong Province ( A2017269 and A2016250 ) and Key Special Project of National Key Research and Development Plan Program ( 2016YFC0207000 ).
All Science Journal Classification (ASJC) codes
- Environmental Science(all)