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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 μm). The DECH in PM 2.5 was defined as daily total concentration-hours > 25 μg/m 3 . Methods A generalized additive model with a quasi-Poisson link was applied to estimate the associations between day-to-day variation in PM 2.5 DECH and day-to-day variation in cardiovascular mortality in six subtropical cities in Guangdong Province, China. Results The analysis revealed significant associations between PM 2.5 DECHs and cardiovascular mortality. A 500 μg/m 3 ∗ h increase in PM 2.5 DECHs at lag 03 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 PM 2.5 DECHs than daily mean PM 2.5 (6478 (95% CI: 5071, 7917) VS 5136 (95% CI: 3990, 6305)). Conclusion This study reveals that PM 2.5 DECH is one important exposure indicator of ambient PM 2.5 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. [ABSTRACT FROM AUTHOR]

Background Epidemiological studies have reported significant association between ambient fine particulate matter air pollution (PM 2.5 ) and mortality, however, few studies have investigated the relationship of mortality with PM 2.5 and associated mortality burden in China, especially in a multicity setting. Methods We investigated the PM 2.5 -mortality association in six cities of the Pearl River Delta region from 2013 to 2015. We used generalized additive Poisson models incorporating penalized smoothing splines to control for temporal trend, temperature, and relative humidity. We applied meta-analyses using random-effects models to pool the effect estimates in the six cities. We also examined these associations in stratified analyses by sex, age group, education level and location of death. We further estimated the mortality burden (attributable fraction and attributable mortality) due to ambient PM 2.5 exposures. Results During the study period, a total of 316,305 deaths were recorded in the study area. The analysis revealed a significant association between PM 2.5 and mortality. Specifically, a 10 μg/m 3 increase in 4-day averaged (lag 03 ) PM 2.5 concentration corresponded to a 1.76% (95% confidence interval (CI): 1.47%, 2.06%) increase in total mortality, 2.19% (95% CI: 1.80%, 2.59%) in cardiovascular mortality, and 1.68% (95% CI: 1.00%, 2.37%) in respiratory mortality. The results were generally robust to model specifications and adjustment of gaseous air pollutants. We estimated that 0.56% (95% CI: 0.47%, 0.66%) and 3.79% (95% CI: 3.14%, 4.45%) of all-cause mortalities were attributable to PM 2.5 using China's and WHO's air quality standards as the reference, corresponding to 1661 (95% CI: 1379, 1946) and 11,176 (95% CI: 9261, 13,120) attributable premature mortalities, respectively. Conclusion This analysis adds to the growing body of evidence linking PM 2.5 with daily mortality, and mortality burdens, particularly in one Chinese region with high levels of air pollution. [ABSTRACT FROM AUTHOR]

In 2012, Chinese Environmental Bureau modified its National Ambient Air Quality Standards to include fine particulate matter (PM 2.5 ). Recent air pollution monitoring data shows that numerous locations have exceeded this standard, which may have resulted in avoidable adverse health effects. For example, among the 74 Chinese cities with PM 2.5 monitoring data in 2013, only three cities attained the annual air quality standard (35 μg/m 3 ). This study aimed to quantify the potential short- and long-term health benefits from achieving the Chinese ambient air quality standard and WHO’s air quality objectives. A generalized additive model was used to estimate the short-term association of mortality with changes in daily PM 2.5 concentrations, based on which we estimated the potential premature mortality reduction that would have been achieved during the period of 2012–2015 if the daily air quality standard had been met in Guangzhou, China; we also estimated the avoidable deaths if attaining the annual air quality standard using the relative risk obtained from a previous cohort study. During the study period, there were 160 days exceeding the national daily PM 2.5 standard (75 μg/m 3 ) in Guangzhou, and the annual average concentration (47.7 μg/m 3 ) was higher than the air quality standard of 35 μg/m 3 . Significant associations between PM 2.5 and mortality were observed. An increase of 10 μg/m 3 in PM 2.5 was associated with increases in daily death counts of 0.95% (95% CI: 0.56%, 1.34%) in natural mortality, 1.31% (95% CI: 0.75%, 1.87%) in cardiovascular mortality, and 1.06% (95% CI: 0.19%, 1.94%) in respiratory mortality. The health benefits of attaining the national daily air quality standard of PM 2.5 (75 μg/m 3 ) would have prevented 143 [95% confidence interval (CI): 84, 203] fewer natural deaths, including 84 (95% CI: 48, 121) fewer cardiovascular deaths and 27 (95% CI: 5, 49) fewer respiratory deaths. Had the annual PM 2.5 levels been reduced to 35 μg/m 3 , an estimated 3875 (95% CI: 1852, 6074) natural deaths, 2378 (95% CI: 800, 4230) cardiovascular deaths, and 227 (95% CI: -437, 1033) respiratory deaths could have been prevented. Even greater substantial mortality reductions could be achieved if the WHO’s air quality objectives were met. Our study suggests that air pollution is significantly associated with mortality in Guangzhou, and more stringent air quality standards would significantly reduce air pollution-related premature mortality. [ABSTRACT FROM AUTHOR]