Map of Air Quality and Ozone Levels in the US

Click on the map to enlarge it in a pop-up window.

Interactive version best usable on a desktop computer or desktop mode (↗): Find County Data (Welcome to County Explorer box) → Maps tab and click Energy & Environment to expand menu → Air Quality → Ozone Level

Produced by the National Association of Counties (NACo) from an analysis of Environmental Protection Agency (EPA) data, this choropleth map of the UNITED STATES colorizes the counties light orange, orange, teal, and purple depending on concentrations of ground-level ozone concentrations — numbered in parts per billion — in the atmosphere. Update: the color scheme in the interactive map linked above has been changed. Black and light grey counties indicate counties without data on the map. Ozone at the ground level in urban, suburban, and rural areas alike can cause health complications (↗) such as decreased lung function, excessive coughing, wheezing, airway inflammation, and chest pain, among others. Light-orange counties have less than 60 parts per billion ozone, orange counties have 60 up to 65 ppb, teal counties have between 65 and 69 ppb, and purple counties (none shown) would have over 70 ppb. While no counties are colored purple in this map, NACo's County Explorer interactive map website (linked above) notes that 184 counties in 22 states have been designated as nonattainment areas. The nonattainment areas listed here by the EPA (↗) are counties "that do not meet EPA's 2015 standards for ground-level ozone of 70 parts per billion as of November 2018."