Editing Smog (section)

===Levels of unhealthy exposure===
The [[United States Environmental Protection Agency|U.S. EPA]] has developed an [[air quality index]] to help explain air pollution levels to the general public. 8 hour average ozone concentrations of 85 to 104 [[parts per notation|ppbv]] are described as "Unhealthy for Sensitive Groups", 105 ppbv to 124 ppbv as "unhealthy" and 125 ppb to 404 ppb as "very unhealthy".<ref name=epa/> The "very unhealthy" range for some other pollutants are: 355 μg m<sup>−3</sup> – 424 μg m<sup>−3</sup> for [[PM10]]; 15.5 ppm – 30.4ppm for CO and 0.65 ppm – 1.24 ppm for NO<sub>2</sub>.<ref>{{Cite journal | url = http://www.epa.gov/ttn/oarpg/t1/memoranda/rg701.pdf | title = Guidelines for the Reporting of Daily Air Quality – the Air Quality Index (AQI) | date = May 2006 | publisher = United States Environmental Protection Agency, Office of Air Quality Planning and Standards | issue = EPA-454/B-06-001 | archive-url = https://web.archive.org/web/20060725183242/http://www.epa.gov/ttn/oarpg/t1/memoranda/rg701.pdf | archive-date = 25 July 2006 | url-status = dead }}</ref>