Researchers say they're surprised by how much harmful ozone and ozone-causing chemicals are drifting into the Colorado mountains from urban and rural areas below.
Scientists from the National Center for Atmospheric Research and NASA say an intensive examination of pollution along the populated northern Front Range found ozone all the way up to the mountainous Continental Divide.
They say mountain ozone levels were similar to or greater than levels at lower elevations in some cases.
Researchers gathered data from aircraft, balloons and ground stations from the Denver area to Fort Collins, about 60 miles away, from mid-July through last week.
The scientists stressed they are in the early stages of reviewing the data and were hesitant to offer many specifics. They expect to start making data public by the end of the year.
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