[sgtlethargic]

Why do parts of California have such bad air pollution?
Sources of air pollution in California include vehicular emissions, demand for energy production through fossil fuels, and household energy consumption as well as wildfires as a prominent natural cause. Areas of relatively dense populations often experience higher daily pollution levels as a result of increased traffic, industry, and domestic emissions. Locations in or near the Klamath, Sierra-Nevada, and Coastal mountains, among numerous other mountainous areas, are more likely to experience elevated pollution levels as a result of wildfires, despite having less pollution most of the year.


California’s most populous cities, including Los Angeles, San Diego, San Jose, and San Francisco, are all located near California’s coastal mountain ranges. Here, westerly sea breezes can create a pollution-trapping effect in which emissions blown inland become trapped by the mountains, inversion layers, and stagnant air. Without a means for dispersion, pollution accumulates in the coastal valleys.3


Warm temperatures and abundant sunshine, for which California’s coast is known, bake nitrogen oxides and volatile organic compounds, creating ozone. As summer temperatures rise, as they have in recent years, so too do California’s ozone levels.


In addition to ozone, warming temperatures have also contributed to California’s rising PM2.5 levels. Increasingly hot and dry conditions have drastically increased the threat of California wildfires. Since 1970, the number of annual burned acreage has risen eightfold, while over the same time period summer temperatures have increased by 2.5 degrees.4

https://www.iqair.com/us/usa/california