PlainAir — Air-Quality Data, Guides & Research https://plainairdata.com Plain-language analyses of official EPA Air Quality System (AQS) data: editorial guides and original research from PlainAir, an independent air-quality-data publisher. en-us Sun, 14 Jun 2026 07:08:21 GMT <![CDATA[National Trends in Good Days Percentage from 2020 to 2024]]> https://plainairdata.com/research/national-good-days-trend-2020-2024/ https://plainairdata.com/research/national-good-days-trend-2020-2024/ Research <![CDATA[State Averages of Median AQI Across 2020-2024]]> https://plainairdata.com/research/state-avg-aqi-trends-2020-2024/ https://plainairdata.com/research/state-avg-aqi-trends-2020-2024/ Research <![CDATA[Top 10 U.S. Counties with the Most Unhealthy Air Days, 2024]]> https://plainairdata.com/research/top-10-counties-unhealthy-2024/ https://plainairdata.com/research/top-10-counties-unhealthy-2024/ Research <![CDATA[Understanding the Air Quality Index (AQI): A Complete Guide]]> https://plainairdata.com/guides/understanding-aqi/ https://plainairdata.com/guides/understanding-aqi/ Guides <![CDATA[Best and Worst Air Quality in the US: County Rankings]]> https://plainairdata.com/guides/best-worst-air-quality/ https://plainairdata.com/guides/best-worst-air-quality/ Guides <![CDATA[Cities with the Best and Worst Air Quality in the US]]> https://plainairdata.com/guides/cities-with-best-worst-air-quality/ https://plainairdata.com/guides/cities-with-best-worst-air-quality/ Guides <![CDATA[The 5 Most Common Air Pollutants Explained]]> https://plainairdata.com/guides/common-air-pollutants/ https://plainairdata.com/guides/common-air-pollutants/ Guides <![CDATA[How Air Pollution Affects Your Health: EPA Data & Guidance]]> https://plainairdata.com/guides/how-air-pollution-affects-health/ https://plainairdata.com/guides/how-air-pollution-affects-health/ Guides <![CDATA[Using Air Quality Data to Choose Where to Live]]> https://plainairdata.com/guides/choosing-where-to-live-air-quality/ https://plainairdata.com/guides/choosing-where-to-live-air-quality/ Guides <![CDATA[How Wildfire Smoke Affects Air Quality: What the EPA Data Shows]]> https://plainairdata.com/guides/wildfire-smoke-air-quality/ https://plainairdata.com/guides/wildfire-smoke-air-quality/ Guides <![CDATA[AQI Pollutants Explained: What Each One Means for Your Health]]> https://plainairdata.com/pollutant-guide/ https://plainairdata.com/pollutant-guide/ Guides