Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets.

Particles less than 10 micrometers in diameter (PM10) pose a health concern because they can be inhaled into and accumulate in the respiratory system.

Particles less than 2.5 micrometers in diameter (PM2.5) are believed to pose the greatest health risks.

The Ministry of Environmental Protection began gauging public opinion on revised air quality standards on Nov. 16, 2011.

The new standards will, for the first time, include readings of concentrations less than PM2.5, a major cause of haze harmful to health, the ministry said in a statement.

顆粒物是指空氣中的灰塵、散土、煙灰、煙霧及液態(tài)小滴等顆粒。

PM10是指大氣中直徑小于10微米的顆粒物，稱(chēng)為可吸入顆粒物，由于其可進(jìn)入呼吸系統(tǒng)并聚集，對(duì)人體健康有一定隱患。

PM2.5是指大氣中直徑小于2.5微米的顆粒物，稱(chēng)為可入肺顆粒物，盡管粒徑小，但對(duì)人體的危害最大。

國(guó)家環(huán)保部從2011年11月16日開(kāi)始就新的《環(huán)境空氣質(zhì)量標(biāo)準(zhǔn)》征求公眾意見(jiàn)。

新標(biāo)準(zhǔn)首次將有害健康的灰霾“元兇”——PM2.5納入常規(guī)空氣質(zhì)量評(píng)價(jià)體系。