Hikers are being asked to help monitor ozone pollution in New Hampshire's mountains.
The Appalachian Mountain Club is giving hikers special cardboard cards that turn various shades of tan and brown when exposed to pollution.
Each year, more than 60,000 hikers seek the views on Mount Washington alone. But once they get there, the panorama might not be what they expected because of haze and ozone pollution.
The club says ozone levels on mountaintops often are higher than those found in major U.S. cities. The club's Visibility Volunteers Project is gathering information to be used for public education and to advocate for improving air quality.
The club started the program in May 2003. That year it got 100 cards from hikers in Maine to Virginia. This year, it expects to receive 250.