The report identified Anderson, California, an area 150 miles outside Sacramento, as the city with the worst air pollution in 2018. Anderson had an average score of 28 on the WHO air quality index, while Sacramento had an average score of nearly 15 — the highest among large metros in the US. Both levels are considered "moderate."
For a brief time in November, Sacramento had the worst air pollution of any major city on earth due to the Camp Fire blaze. The city's air quality has since improved, but it has taken a while for the smoke to lift.