This indicator shows how many days per year were assessed to have air quality that was worse than “moderate” in Champaign County, according to the U.S. Environmental Protection Agency’s Air Quality Index Reports. The period of analysis is 1980-2019, and the U.S. EPA’s air quality ratings analyzed here are as follows, from best to worst: “good,” “moderate,” “unhealthy for sensitive groups,” “unhealthy,” and “very unhealthy.”
While there has been no consistent year-to-year trend in the number of days per year rated to have air quality worse than moderate, the number of days in peak years has decreased since 2000. Where peak years before 2000 had between one and two dozen days with air quality worse than moderate (e.g., 1983, 18 days; 1988, 23 days; 1994, 17 days; 1999, 24 days), the year with the greatest number of days with air quality worse than moderate since 2000 was 2002, with 10 days.
There have been several years in the last decade that had no days with air quality worse than moderate; this did not occur at all before 2006. This, and the decrease in the number of days with air quality worse than moderate even in peak years, suggests that there has been some overall improvement in air quality, even without a clear year-to-year trend.
This data is sourced from the U.S. EPA’s Air Quality Index Reports. The reports are released annually, and our period of analysis is 1980-2018. The Air Quality Index Report websites does caution that "[a]ir pollution levels measured at a particular monitoring site are not necessarily representative of the air quality for an entire county or urban area," and recommends that data users do not compare air quality between different locations.
 Environmental Protection Agency. (1980-2016). Air Quality Index Reports. (Accessed 2 May 2017).