Air Quality by ZIP Code: What the Numbers Mean for Your Health
What Is the Air Quality Index (AQI)?
The Air Quality Index runs from 0 to 500. Values below 50 are "Good" β safe for everyone. Values above 100 are "Unhealthy for Sensitive Groups." Above 150 is "Unhealthy" for all. ZipScore shows the average annual AQI for each ZIP code, derived from EPA monitoring data.
PM2.5: The Most Dangerous Pollutant
Fine particulate matter (PM2.5) β particles smaller than 2.5 micrometers β can penetrate deep into lungs and enter the bloodstream. Long-term exposure is linked to heart disease, lung cancer, and stroke. The WHO recommends annual average PM2.5 below 5 ΞΌg/mΒ³; the US EPA standard is 12 ΞΌg/mΒ³.
Ozone vs. Particle Pollution
Ground-level ozone (smog) is most dangerous on hot, sunny days in urban areas. It's particularly problematic in LA, Denver, and other sunny metros. Particle pollution is worse near highways, industrial areas, and in areas affected by wildfire smoke.
Finding Clean-Air ZIP Codes
Visit our Best for Air Quality page to browse ZIP codes ranked by air quality. ZIP code profiles also show the air quality grade alongside crime, schools, and cost of living β giving you a complete picture of neighborhood livability.
Seasonal Variation
Air quality varies seasonally. Summer brings higher ozone in most regions. Fall and winter can bring worse particle pollution in areas prone to atmospheric inversions. Always check multiple seasons worth of data before committing to a location.