World Health Organization (WHO) set a serial of interim target for PM guideline(World Health Organization 2006) based on the accumulative evidence on the harmful effects of PM2.5 aiming at reducing disease burden. Although this WHO interim target for PM guideline quantitatively measures a possible gradient relations with PM exposures, no review has been conducted to summarize the effect of PM on CVD mortality according to different interim targets of WHO.Methods:
We searched PubMed and Embase databases for cohort studies that reported the association between CVD mortality and long-term exposure to outdoor PM. The following inclusion criteria were used for the screening: (i) investigated the association between CVDs mortality and ambient long- term PM exposure; and (ii) cohort study; and (iii) provided sufficient data to calculate hazards ratio (HR) with 95%CI. Studies that met the following were excluded: (i) irrelevant to PM or CVD mortality; (ii) study period shorter than 1 year; (iii) indoor rather than outdoor PM exposure; (iv) non-cohort study.Results:
The exposure to PM2.5 significantly increased CVD mortality by 14% (HR = 1.14, 95%CI = 1.09–1.19, I2 = 92.4%) for every 10 μg/m3 increment. However, there was no significant association between PM10 exposure and CVD mortality (HR = 1.02, 95%CI = 0.89–1.16, I2 = 96.3%). Pooled effects of PM2.5 were similar among subgroups with different WHO interim targets. We do not find an clear relationship between increasing trend of PM10 and hazard ratio.Conclusion:
Ambient PM2.5 exposure level was positively associated with overall mortality of CVD. Results from this study echo continuous efforts on lowering the ambient PM level to the strictest standard (AQG), particularly for the developing countries.