In the wake of the Camp Fire in Paradise, California, the state's northern areas saw pollution levels that surpassed those in China and India - two of the most polluted nations in the world.Advertisement
Despite these dips in air quality, a recent report from IQAir, a global air quality database, found that average pollution levels in the US met the World Health Organization's standards for healthy air in 2018. But a few individual cities struggled to hit the same target.
The report listed dozens of US cities with "moderate" air quality, which could cause respiratory problems for sensitive individuals (e.g. children, older adults, or people with lung or heart disease) performing outdoor activities. Other cities showed pollution levels that fell just short of the WHO threshold.
Since these cities were often located in the same metropolitan area, we distilled the report's data to include only large metros (those with at least one million residents).
Sacramento had the worst air pollution of any major city on earth in November.
Los Angeles is also struggling to recover from the California wildfire season.
In 2018, San Francisco's air quality reached levels that could cause coughing and irritation.
San Diego's air quality earned an 'F' letter grade.
Cincinnati, Ohio suffers from particle pollution, which is often produced by construction sites and automobiles.
Coal-fired power plants spell bad news for air quality in Indianapolis, Indiana.
Pittsburgh, Pennsylvania was just shy of WHO's clean air threshold.
Traffic congestion in Boston, Massachusetts could be polluting the air.