Even with improvements resulting from regulation, 80 million people in the United States are still breathing air that does not meet at least one EPA air-quality standard. The EPA Web site maps noncompliant or "nonattainment" areas by pollutant type based on the ground-based monitoring network. For example, the Los Angeles region is categorized as "extreme" nonattainment for 1-hour ozone levels (the only region in the country with an "extreme" designation) and "serious" nonattainment for carbon monoxide and particulate matter.