Howell County, MO: EPA's radon zone, explained

EPA places Howell County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Howell County sits at the 53rd percentile nationally for radon potential — above 53 of every 100 rated counties.

Where Howell County sits nationally

Howell County, Missouri is home to about 40,762 people across 927.177 square miles. Population density there runs about 44 people per square mile. By population, Howell County is the 394th largest of every county sharing its EPA zone — the 62nd percentile by population within that zone. Geologically, Howell County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

Zone vs. an actual test

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Howell County's Zone 2 prediction lands in the gap between the two. Howell County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

If Howell County tests above the action level

For a Howell County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Missouri's state radon program

For Howell County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Howell County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

Where Howell County's figures come from

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone Howell County carries, the zone explainer covers what it does and doesn't tell you about any one house.