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While increasing evidence suggested that PM 2.5 is the most harmful fraction of the particle pollutants, the health effects of coarse particles (PM 10–2.5 ) have been inconclusive, especially on cerebrovascular diseases, we thus evaluated the effects of PM 10 , PM 2.5 , and PM 10–2.5 on stroke mortality in six Chinese subtropical cities using generalized additive models. We also conducted random-effects meta-analyses to estimate the overall effects across the six cities. We found that PM 10 , PM 2.5 , and PM 10-2.5 were significantly associated with stroke mortality. Each 10 μg/m 3 increase of PM 10 , PM 2.5 and PM 10-2.5 (lag03) was associated with an increase of 1.88% (95% CI: 1.37%, 2.39%), 3.07% (95% CI: 2.35%, 3.79%), and 5.72% (95% CI: 3.82%, 7.65%) in overall stroke mortality. Using the World Health Organization's guideline as reference concentration, we estimated that 3.21% (95% CI: 1.65%, 3.01%) of stroke mortality (corresponding to 1743 stroke mortalities, 95% CI: 896, 1633) were attributed to PM 10 , 5.57% (95% CI: 0.50%, 1.23%) stroke mortality (3019, 95% CI: 2286, 3777) were attributed to PM 2.5 , and 2.02% (95% CI: 1.85%, 3.08%) of stroke mortality (1097, 95% CI: 1005, 1673) could be attributed to PM 10-2.5 . Our analysis indicates that both PM 2.5 and PM 10-2.5 are important risk factors of stroke mortality and should be considered in the prevention and control of stroke in the study area. [ABSTRACT FROM AUTHOR]

Though significant associations between particulate matter (PM) air pollution and cardiovascular diseases have been widely reported, it remains unclear what characteristics, such as particle size and chemical constituents, may be responsible for the effects. A time-series model was applied to examine the cardiovascular effects of particle size (for the period of 2009–2011) and chemical constituents (2007–2010) in Guangzhou, we controlled for potential confounders in the model, such as time trends, day of the week, public holidays, meteorological factors and influenza epidemic. We found significant associations of cardiovascular mortality with PM 10 , PM 2.5 and PM 1 ; the excess risk (ER) was 6.10% (95% CI: 1.76%, 10.64%), 6.11% (95% CI: 1.76%, 10.64%) and 6.48% (95% CI: 2.10%, 11.06%) for per IQR increase in PM 10 , PM 2.5 and PM 1 at moving averages for the current day and the previous 3 days (lag 03 ), respectively. We did not find significant effects of PM 2.5-10 and PM 1-2.5 . For PM 2.5 constituents, we found that organic carbon, elemental carbon, sulfate, nitrate and ammonium were significantly associated with cardiovascular mortality, the corresponding ER for an IQR concentration increase at lag 03 was 1.13% (95% CI: 0.10%, 2.17%), 2.77% (95% CI: 0.72%, 4.86%), 2.21% (95% CI: 1.05%, 3.38%), 1.98% (95% CI: 0.54%, 3.44%), and 3.38% (95% CI: 1.56%, 5.23%), respectively. These results were robust to adjustment of other air pollutants and they remained consistent in various sensitivity analyses by changing model parameters. Our study suggests that PM 1 and constituents from combustion and secondary aerosols might be important characteristics of PM pollution associated with cardiovascular mortality in Guangzhou. [ABSTRACT FROM AUTHOR]

Abstract The World Health Organization sets up the Ambient Air Quality Guidelines mainly based on short-term and long-term health effects of air pollution. Previous studies, however, have generally revealed a non-threshold concentration-response relationship between air pollution and health, making it difficult to determine a concentration, below which no obvious health effects can be observed. Here we proposed a novel approach based on the concept of "number needed to treat", specifically, we calculated the reduction in air pollution concentrations needed to avoid one death corresponding to different hypothetical concentration standards; the one with the smallest value would be the most practical concentration standard. As an example, we applied this approach to the daily standard of ambient PM 2.5 (particulate matter with aerodynamic diameter ≤2.5 μm) in four Chinese cities. The calculation was based on the association between daily mortality and ambient PM 2.5 , which was examined by a generalized additive model with adjustment of important covariates. Significant associations were observed between PM 2.5 and mortality. Our analyses suggested that it is appropriate to have 50 μg/m3 as the daily standard of ambient PM 2.5 for the study area, compared to the current standard of which were directly adopted from the national standard of 75 μg/m3. This novel approach should be considered when planning and/or revising the ambient air quality guidelines/standards. Highlights • There is limited method for air pollution standard formulation. • The "number needed to treat" was proposed as one potential method. • We examined the acute association between PM 2.5 and mortality in four Chinese cities. • We then calculated the reduction in air pollution concentrations needed to avoid one death. • Finally, we suggested that 50 μg/m3 should be considered as daily standard of ambient PM 2.5 in the study area. Capsule This study proposes a new "number needed to treat" approach to help establish or revise daily ambient air quality standards. [ABSTRACT FROM AUTHOR]

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]

Abstract: Background: Heat waves have been reported to be associated with increased mortality; however, fewer studies have examined the effect modification by heat wave characteristics, individual characteristics and community characteristics. Methods: This study investigated the effect of extreme heat on mortality in 2 urban and 2 rural communities in Guangdong Province, China during 2006–2010. The effect of extreme heat was divided into two parts: main effect due to high temperature and added effect due to prolonged heat for several consecutive days. A distributed lag non-linear model was used to calculate the relative risk with consideration of lag days and potential confounding factors. Separate models were further fit by individual characteristics (cause of death, age and gender) and heat wave characteristics (intensity, duration and timing), and potential effect modification of community characteristics was examined using a meta-regression, such as educational levels, percentage of the elderly, Gross Regional Domestic Product (GDP). Results: The overall main effects (ER=8.2%, 95% CI: 3.4%, 13.2%) were greater than the added effects (ER=0.0%, 95% CI: −3.8%, 4.0%) on the current day. The main effect peaked at lag0–2, and was higher for the two rural areas compared to the two cities, for respiratory compared to cardiovascular mortality, for those ≥75years old and for females. The modifying effects of heat wave characteristics and community characteristics on mortality were not statistically significant. Conclusion: This study suggests the effects of extreme heat were mainly driven by high temperature, which can be modified by some individual characteristics. [Copyright &y& Elsevier]

Abstract: Background: Numerous studies have reported the association between ambient temperature and mortality. However, few multicity studies have been conducted in subtropical regions in developing countries. The present study assessed the health effects of temperature on mortality in four subtropical cities of China. Methods: We used “double threshold-natural cubic spline” distributed lag non-linear model (DLNM) to investigate the cold and hot effects on mortality at different lags in four subtropical cities. Then we conducted a meta-analysis to estimate the overall cold and hot effects on mortality at different lag days. Results: A U-shaped relationship between temperature and mortality was found in the four cities. Cold effect was delayed and persisted for about 27days, whereas hot effect was acute and lasted for 3days. In Changsha, Kunming, Guangzhou and Zhuhai, a 1°C decrease of temperature under the low threshold was associated with a lag0–27 cumulative relative risk (RR) of 1.061 (95% confidence interval (CI): 1.023–1.099), 1.044 (95% CI: 1.033–1.056), 1.096 (95% CI: 1.075–1.117) and 1.111 (95% CI: 1.078–1.145) for total mortality, respectively. And RR for 1°C increase of temperature above the hot threshold at the lag0 was 1.020 (95% CI: 1.003–1.037), 1.017 (95% CI: 1.004–1.030), 1.029 (95% CI: 1.020–1.039) and 1.023 (95% CI: 1.004–1.042), respectively. The cold and hot effects were greater among the elderly in Changsha, Guangzhou and Zhuhai. Meta analysis showed that the hot effect decreased gradually with lag days, with the greatest effect at current day (RR=1.023, 95% CI: 1.015–1.031); while the cumulative cold effect increased gradually with lag days, with the highest effect at lag0–27 (RR=1.076, 95% CI: 1.046–1.107). Conclusion: Both low and high temperatures were associated with increased mortality in the four subtropical Chinese cities, and cold effect was more durable and pronounced than hot effect. [Copyright &y& Elsevier]