Wildfires across the American West caused so much deadly air pollution in 2020 that they far more than overcame the drop in pollution caused by pandemic-responsive travel restrictions, according to a new air quality report. The findings, released Tuesday by IQAir Group, a Swiss-based air-quality technology company, show an overall 7% increase in fine particulate (PM2.5) pollution for the year nationwide despite a 13% drop between March and July from reduced fossil fuel combustion. Climate change worsens wildfires in multiple ways as heated temperatures and drought turn landscapes into proverbial tinder boxes. Of the world’s 25 most polluted cities last September, 24 were in California and Oregon, with heavy smoke in Weed, California, driving PM2.5 levels to 471 times the WHO’s target. (Washington Post $, Wall Street Journal $; Climate Signals background: Wildfires; 2020 Western wildfire season)