Perpetual drought + constant wildfires.
I am not knowledgeable about the stats you provided but since the fires (over a year now) LA has been consistently red except for some rainy days, although it’s even been red during the rain. We can figure it out but we are leaving LA!
Little deceptive using the WHO interim targets there, those are way lower than the US EPA AQI standard. Show me Europe during the same time …
Out here on the US West Coast we have been under the influence of a strong inversion that has been trapping air near the surface for the last several days. In addition to stagnant air us up in the Pacific Northwest have had persistent fog. Get up above 1500’ and the weather is clear and warm!