From:  An expert position paper on environment, occupation and climate change effects on allergic respiratory diseases in Italy

 Recommended Air Quality Guidelines (AQG) levels and interim targets.

PollutantAveraging timeInterim targetAQG level
1234
PM2.5, μg/m3Annual352515105
24-houra755037.52515
PM10, μg/m3Annual7050302015
24-houra150100755045
O3, μg/m3Peak seasonb10070--60
8-houra160120--100
NO2, μg/m3Annual403020-10
24-houra12050--25
SO2, μg/m324-houra12550--40
CO, mg/m324-houra7---4

a 99th percentile (i.e., 3–4 exceedance days per year). b Average of daily maximum 8-hour mean ozone (O3) concentration in the six consecutive months with the highest six-month running-average O3 concentration. CO: carbon monoxide; NO2: nitrogen dioxide; PM10: atmospheric particulate matter with a diameter ≤ 10 μm; PM2.5: atmospheric particulate matter with a diameter ≤ 2.5 μm; SO2: sulphur dioxide. Reprinted from [4]. © WHO 2021. Licensed under the Creative Commons Attribution-NonCommercial-Share Alike 3.0 IGO licence (CC BY-NC-SA 3.0 IGO).