The Boise metropolitan area is growing rapidly, with new housing developments, new shopping centers, and new roads. Automobile traffic is increasing and air quality declining as more people move into this region, long called the Treasure Valley for its natural riches.

International epidemiological studies have shown a strong correlation between ambient air pollution and respiratory illnesses. Such conditions appear to disproportionately harm children and elderly people who suffer from asthma and other respiratory illnesses, and anyone with chronic cardiovascular disease.

Because the Treasure Valley now accounts for about 60 percent of Idaho’s population, it is a focus of state concern about air quality, overall environmental quality, and public health. Environmental changes could restrict the region’s potential for future growth and development because the Clean Air Act requires that the Treasure Valley meet national air quality standards. Air quality conditions associated with winter inversions have already placed the Valley near noncompliance limits.