What EPA's radon map says about Essex County

Essex County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Essex County ranks higher in radon potential than 100% of rated counties (the 100th percentile).

How Essex County compares

About 823,938 people live in Essex County, Massachusetts, spread over 492.514 square miles. Population density there runs about 1,673 people per square mile. Among counties sharing Essex County's EPA zone, it outranks 99% of them by population. EPA's geology-based Region 1 groups Essex County with 58 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Essex County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. Some Essex County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

Testing and mitigation in Essex County

Mitigation cost doesn't depend on Essex County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Massachusetts's state radon program

Essex County's test kit answers today; a Airthings radon monitor keeps answering for Essex County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Essex County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.