A working staff of the Beijing Environment Protection Monitoring Center checks the monitoring data for the PM2.5 measure of air quality in Beijing, capital of China, Jan. 7, 2012. Beijing's environment authority on Jan. 21, 2012 released the PM2.5 measure of air quality, which is considered stricter than its previous standard of PM10. Particles 2.5 microns or less in diameter (PM2.5) are referred to as "fine" particles and are believed to pose greater health risks than larger particles because they can embed deep in people's lungs. (Xinhua/Gong Lei)