It took me a few minutes to figure out how to read the Executive Summary (Table 0.1, page xvii).<p>The AQG number is the main recommendation, and refers to the concentration in micrograms per cubic meter (ug/m^3). So the report says the world should aim for 5 ug/m^3 or less of PM 2.5 annually, and 15 ug/m^3 or less PM 10 annually.<p>The interim targets are meant to be realistic goals to set along the way, so anywhere with worse than 75 ug/m^3 PM 2.5 on a daily basis might aim for that goal first.<p>I had to check how the concentrations compare to various AQI (Air Quality Index) reports, like my iPhone weather app. 5 ug/m^3 of PM 2.5 is an AQI of 21. Currently an AQI of 0-50 is considered “good”, so maybe down the road the scale will be adjusted based on these new recommendations.<p><a href="https://www.airnow.gov/aqi/aqi-calculator-concentration/" rel="nofollow">https://www.airnow.gov/aqi/aqi-calculator-concentration/</a><p>Curious to see what the previous recommendations were, the 2005 report has the same first 3 interim targets for PM 2.5 and PM 10. The current report’s 4th interim target is set to the AQG (final recommendation) level from the previous report, and the new AQG level is now lower than the previous one. This is because there is now stronger statistical evidence of health damage occurring at levels above the new recommendation, the data has shown we needed a new lower threshold.