Asian, European Emissions Impact U.S. Air Quality
Up to 15
percent of U.S. air pollution comes from Asian and European sources,
according to a study from the Nelson Institute for Environmental
Studies at the University of Wisconsin-Madison.
"It is useful to understand how much air pollution is coming from
areas outside our own region, so that when we're thinking about how to
cut down ozone concentrations, we can take into account what factors we
have control over and what factors we don't have control over," said Tracey Holloway,
a professor of environmental studies in the Center for Sustainability
and the Global Environment (SAGE), who led the new study.
Unlike the protective stratospheric ozone layer, surface ozone is a
pollutant and has been implicated in increased mortality rates,
respiratory and cardiovascular disease and vegetative and crop damage,
the researchers said.
Using a computer model that analyzed global wind data and chemical
emissions from various countries, the research group found that the
impact of Asian and European ozone contributions varies across the
While previous computer modeling studies have examined ozone
transportation between entire continents, often focusing on spring and
summer, Holloway said. "[Our study] is the first that has laid out the
seasonality of ozone import to specific regions of the United States."
Overall, the models showed Asian and European emissions contributed
three to 18 percent of total surface ozone on a monthly average basis
across the United States. The western states endured the heaviest
impact, due to their proximity to Asia and the predominance of
west-to-east wind currents, Holloway said. Foreign emissions
contributed an annual average of 12 percent of the total surface ozone
along the West Coast, but only six to ten percent along the East Coast.
Spring and fall peaks of imported ozone were evident in all regions
as a result of the optimal combination of a strong jet stream across
the Pacific Ocean and stability of ozone during these seasons.