Ozone blowing over from Asia is raising background levels of a major ingredient of smog in the skies over western US states, according to a new study appearing in today’s edition of the journal Nature.
The amounts are small and, so far, only found in a region of the atmosphere known as the free troposphere, at an altitude of two to five miles, but the development could complicate US efforts to control air pollution.
Though the levels are small, they have been steadily rising since 1995, and probably longer, said lead author Owen R Cooper, a research scientist at the University of Colorado attached to the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colorado.
“The important aspect of this study for North America is that we have a strong indication that baseline ozone is increasing,” said Cooper. “We still don’t know how much is coming down to the surface. If the surface ozone is increasing along with the free tropospheric ozone, that could make it more difficult for the US to meet its ozone air quality standard.”
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