ＰＭ２．５

noun

PM2.5; fine particulate matter

Refers to airborne particles with a diameter of 2.5 micrometers or less, often discussed in air quality reports and health advisories.

• 今日きょうはＰＭ２．５の濃のう度どが高たかいので、マスクを着つけたほうがいい。

  Since the PM2.5 concentration is high today, you'd better wear a mask.

• 中ちゅう国ごくの大だい都と市しでは、ＰＭ２．５が深しん刻こくな問もん題だいになっている。

  In large Chinese cities, PM2.5 has become a serious problem.