Are current Chinese national ambient air quality standards on 24-hour averages for particulate matter sufficient to protect public health？

With rapid economic development and urbanization in recent decades, China has experienced the worsening of ambient air quality. For better air quality management to protect human health, Chinese government revised national ambient air quality standards （NAAQS） for particulate matter （PM） in 2012 （GB3095-2012）. To assess the effectiveness of current NAAQS for PM on public health in Chinese population, we conducted a meta- analysis on published studies examining the mortality risk of short-term exposure to PM with aerodynamic diameters less than 10 and 2.5μm （PM10 and PM2.5） in China. The reported 24-hour concentrations of PM10 and PM2.5 in studies ranged from 43.5 to 150.1 μg/m^3 and 37.5 to 176.7 μg/m^3. In the pooled excess, mortality risk estimates of short-term exposure to PM. In specific, per 10 μg/m^3 increase in PM10, we observed increases of 0.40% （95%CI： 0.33%, 0.47%）, 0.57% （95%CI： 0.44%, 0.70%） and 0.49% （95%CI： 0.40%, 0.58%） in total, respiratory and cardiovascular mortality, per 10/μg/m^3 increase in PM2.5, we observed increases of 0.51% （95% CI： 0.38%, 0.63%）, 0.62% （95%CI： 0.52%, 0.73%） and 0.75% （95%CI： 0.54%, 0.95%） in total, respiratory and cardiovascular mortality. Finally, we derived 125 μg/m^3 for PM10 and 62.5 μg/ m^3 for PM2.5 as 24-hour recommendation values based on the pooled estimates. Our results indicated that current Chinese NAAQS for PM could be sufficient in mitigating the excess mortality risk from short-term exposure to ambient PM. However, future research on long-term exposure cohort studies in Chinese population is also essential in revising annual averages for PM in Chinese NAAQS.