Environmental air quality standards were revised. The air quality index for monitoring fine particulate matter (PM2 s) was added.

修订环境空气质量标准，增加细颗粒物PM 2.5等监测指标。

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The Olympus E-PL5 and the Olympus E-PM2 bring a new level of freedom to the creative shooting experience.

ENGADGET: Olympus E-PL5 and E-PM2: Micro Four Thirds cameras with OM-D-like focusing, performance boosts (hands-on)

Pollution monitors often collect particulates that measure 10 micrometres across, known as PM10s, as well as the smaller PM2.5s.

BBC: Railway tracks

While PM2.5 is regulated by the EPA, ultrafine particles are not.

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