Population Health

September 19, 2018

Understanding why eastern U.S. air pollution levels are more stagnant in winter

Image of particulate haze over eastern Pennsylvania in winterNew research led by the University of Washington shows why winter air pollution levels in the Eastern United States have remained high, despite overall lower levels of harmful emissions from power plants and vehicles throughout the year.

Air pollution occurs when sulfur dioxide from power plants and nitrogen oxides from both power plants and cars follow various paths to form hazardous sulfate and nitrate particulates.

This multiphase path becomes more important with wintertime air as a result of colder temperatures and less sunlight, leading to a weaker response of sulfate and nitrate to emissions reductions.

The findings suggest that more emissions reductions, of both sulfur and nitrogen oxides, will be needed to improve wintertime air quality in the Eastern U.S. and other cold climates.

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