The air you breathe, county by county
Fine-particle pollution lodges deep in the lungs, and ozone makes summer air hard on kids and asthmatics. KnowYourExposure tracks modeled CDC estimates for every US county - your annual average, and how many unhealthy-air days you actually had.
Quick Answers
What are PM2.5 and ozone? PM2.5 is fine-particle pollution from traffic, industry, and wildfire smoke; ozone forms in hot, sunny air. EPA health standards: 9 ug/m3 annual PM2.5, 35 ug/m3 daily, 70 ppb 8-hour ozone.
How do I check my area? Enter your ZIP code on the KnowYourExposure homepage to see your county's air quality alongside your radon zone and water report.
How to read your county's numbers
Annual PM2.5 average vs 9 ug/m3 - your year-round exposure. Unhealthy particle days vs the 35 ug/m3 daily limit - usually wildfire smoke or winter inversions. Unhealthy ozone days vs 70 ppb - hot, sunny afternoons risky for kids and asthmatics.
Figures are CDC Environmental Public Health Tracking modeled county estimates (2022) - a screening view, not a monitor at your address. For today's live AQI, use AirNow.gov.
How to protect your indoor air
On smoke or ozone-alert days, keep windows closed and run a HEPA air purifier sized to the room; a MERV-13 HVAC filter helps the whole house. Sensitive groups feel effects below the federal limits, so plan outdoor activity around the AirNow forecast the same way you would weather.