The fresh mountain air of the North Cascades is rated Class I, most pristine under the Clean Air Act. While the air quality is excellent, it is not without pollutants. The park lies in the path of prevailing southwesterly winds blowing from rapidly growing urban-industrial areas near the Puget Sound. The mark of humankind's activity can be found everywhere within the park.
Windborne pollutants are deposited on glaciers in the watershed via precipitation. As the ice melts, water carries the pollutants into the food chain, moving from tiny aquatic insects called macroinvertebrates to fish to land mammals and eventually even back to humans.
As a Class I area, the park deserves the highest level of air-quality protection. Consequently, park managers are cooperatively involved with US Geological Survey and the National Park Service's comprehensive air resources management program designed to assess air pollution impacts and protect air quality related resources.
The air resources management program at North Cascades includes monitoring, research, and data collection. The core program includes long-term monitoring for ozone, sulfur dioxide, nitrogen oxides, organic carbon and fine particulates. Visibility and acid precipitation are also measured through remote cameras and water quality testing. In addition, an ongoing effort is underway to determine the biological effects of selected air pollutants on park resources.