You've probably heard of ozone — a colorless gas that has been in the news a great deal — but did you know that there is good ozone and bad ozone? Good ozone occurs naturally in the earth's upper atmosphere, where it helps shield against the sun's damaging ultraviolet rays. Sadly, this good ozone has been depleted in some parts of the world due to pollution, forming an "ozone hole."

Bad ozone forms in the lower atmosphere when pollutants from cars and smokestacks undergo chemical reactions in the presence of sunlight and high temperatures. This bad ozone is hazardous to human health and the environment and becomes a particular problem in the summer months. Hikers are especially vulnerable because ozone often accumulates at high elevations such as mountain summits, where air pollution transported by wind can build up. Also, hikers breathe air in more deeply, thereby increasing their exposure. The AMC is involved in efforts to monitor ozone in the White Mountains and to inform the public about ozone and what can be done about it.

The Research
Since 1986, the AMC has monitored ozone levels at the summit and base of Mount Washington in cooperation with the White Mountain National Forest, the New Hampshire Department of Environmental Services Air Resources Division, the U.S. Environmental Protection Agency, and the Mount Washington Observatory. An additional site was added in 1997 in Pittsburg, N.H. The AMC operates the three monitoring sites in accordance with EPA ozone-monitoring protocols and submits the data to the state of New Hampshire, which then sends the data to the EPA.

The AMC's monitoring shows that ozone levels are often higher at higher elevations. Analysis of the AMC's long-term data reveals that the average daily ozone levels on Mount Washington's summit (approximately 6,288 feet) are two to five times higher than the lower-elevation sites at Camp Dodge and in Pittsburg (at approximately 1,500 feet and 1,368 feet respectively). This finding is consistent with other high-elevation sites where ozone is monitored, such as New York's Adirondack Mountains and the Great Smoky Mountains of Tennessee and North Carolina.

There are several reasons for the elevated ozone levels at mountain summits. One is that ozone is transported to summits by wind from other regions where air pollution is great. (See a graphic showing wind patterns on clean-air days vs. high-smog days in the Northeast.) Another is that ozone does not dissipate as much at summits as it does below treeline, because there are fewer surfaces (such as trees, etc.) that come into contact with the ozone and break it down. Finally, there is less "mixing" of the air at high summits.

In addition to having higher levels of ozone, higher summits tend to see ozone levels remain high for longer periods, in contrast to lower elevations where ozone levels tend to vary predictably over the course of the day. At lower elevations, the lowest ozone levels tend to occur in the morning and the highest in the afternoon (when temperatures are highest and the sun's rays are strongest). AMC researchers have found that these cyclical daily or "diurnal" patterns of ozone concentration hold true at the low-elevation Camp Dodge and Pittsburg monitoring sites, while at the Mount Washington summit site, ozone remains consistently high throughout the day, resulting in a higher background level that continues to build in extended pollution events.

The AMC monitors ozone at the base and summit of Mount Washington 24 hours a day from late May through the end of September. As of September 2002, ozone levels at the AMC's monitoring sites were in compliance with current federal standards overall, although short-term levels on Mount Washington occasionally exceeded the health standards. In addition, a hiker-health study conducted by the AMC found that hikers suffer lung impairment even when ozone is within federally acceptable levels.

What Can You Do?
There are steps you can take to protect yourself from unhealthy ozone exposure. The first is to be informed. Listen to radio reports or check the Air Quality Index on the Web to find the daily ozone forecast. One good site to check is the Hikers for Clean Air Website, which has links to ozone forecasts for each state along the Appalachian Trail. In addition, in the summer of 2002, AMC huts began including ozone information in their morning weather reports. On days of bad air quality, you should consider hiking below treeline or postponing your hike, especially if you have a respiratory or cardiac condition.

If you are active on days when ozone levels are high, be sure to reduce your exertion if you notice symptoms such as coughing, wheezing, tightness in the chest, and/or restricted breathing.

In addition to these protective measures, since ground-level ozone originates in pollution from human activity, there are many steps we can each take as individuals to help reduce the problem year-round:

• Use less electricity. (Electrical generating stations or power plants are a significant source of the pollutants that form ground-level ozone.)
• Use clean modes of transportation, such as bikes or low-emission vehicles; carpool and limit the amount you drive. (Automobile exhaust is another major source of ozone pollution.)
• Actively participate in regional air-quality policy.
  • Become a member of a conservation group, such as the AMC.
  • Keep up to date on pressing environmental issues and voice your opinion on proposed policy changes. You can do this by joining our free Conservation Action Network, which will send you monthly updates plus periodic emails when it's time to take action on important issues such as air quality.

See the EPA's Website for more specific ideas on things that you can do to help reduce air pollution.