Winter Air Quality

Under the Clean Air Act Amendments of 1977, Yellowstone is one of 156 national parks and wilderness areas that are designated Class I airsheds, requiring the most stringent protection. The winter air quality at a given location in Yellowstone depends primarily on proximity to roads, parking areas, employee housing, and visitor lodging. During the 2006–07 winter, 46% of visitors entered the park on a plowed road, 33% by snowmobile, and 21% by snowcoach. Although visitation is far lower in the winter than in the summer, oversnow vehicles produce more emissions. Prolonged exposure to air pollutants such as carbon monoxide (CO), fine particulate matter (PM <2.5 micrometers), and hydrocarbons can pose health risks.

 
Updated 2/20/08