An influx of pollution from Asia in the western United States and more frequent heat waves in the eastern U.S. are responsible for the persistence of smog in these regions over the past quarter century despite laws curtailing the emission of smog-forming chemicals from automobile tailpipes and factories.
The study, led by researchers at Princeton University and the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory (GFDL), highlights the importance of maintaining domestic emission controls on cars, power plants and other industries at a time when pollution is increasingly global.
An influx of pollution from Asia in the western United States and more frequent heat waves in the eastern U.S. are responsible for the persistence of smog in these regions over the past quarter century despite laws curtailing the emission of smog-forming chemicals from automobile tailpipes and factories.
The study, led by researchers at Princeton University and the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory (GFDL), highlights the importance of maintaining domestic emission controls on cars, power plants and other industries at a time when pollution is increasingly global.
Published today in the journal Atmospheric Chemistry and Physics, the study looked at the sources of smog, also known as ground-level ozone, across a period ranging from the 1980s to today. Ground-level ozone, which is distinct from the ozone in the upper atmosphere that protects the planet from ultraviolet radiation, is harmful to human health, exacerbating asthma attacks and causing difficulty breathing. It also harms sensitive trees and crops.
Despite a 50 percent cut in smog-forming chemicals such as nitrogen oxides, commonly known as "NOx", over the past 25 years, ozone levels measured in rural areas of the west have actually climbed. And while ozone in the eastern U.S. has decreased overall, the levels can spike during heat waves.
Read more at Princeton University
Image: Surface-level ozone, also known as smog, has increased over the past quarter century at western U.S. rural sites during springtime, partly due to rising Asian pollution, whereas smog has decreased in the eastern U.S. but can spike due to heat waves, according to a new study from Princeton University and the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory (GFDL). Shown are the 1988-2014 trends in springtime ozone levels on days that were very smoggy (top panel) and on days that were of average smogginess (bottom panel), from observations (left) and from a model built by the Geophysical Fluid Dynamics Laboratory (right). Larger circles indicate sites where there is greater certainty about the ozone trend. On very smoggy days (top panel), ozone levels have declined in the east, as indicated by the blue circles. Ozone levels have increased in the west, as indicated by the red circles, despite a 50 percent reduction in the emission of smog-forming pollutants.
Images courtesy of Meiyun Lin, Princeton University Program in Atmospheric and Oceanic Sciences the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory
