WHO 將空氣品質指引的 PM2.5 濃度標準砍半

從年平均不高於 10μg/m³，降到 5μg/m³。

World Health Organization - WHO global air quality guidelines: particulate matter (‎PM2.5 and PM10)‎, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide (2021/9/22)

Reuters - New WHO air-quality guidelines aim to cut deaths linked to fossil fuels (2021/9/23)

日本経済新聞 - 大気汚染物質「PM2.5」の許容濃度、WHOが半分に (2021/9/24)