Seattle, San Francisco and Los Angeles were also in top ten worst air conditions on earth

 Seattle, San Francisco and Los Angeles were also in the top 10, reflecting the wildfires' huge size and broad impact.

end quote from:

https://www.npr.org/2020/09/14/912701172/its-a-bit-surreal-oregon-fights-smoke-from-record-wildfires-during-a-pandemic