What Kentucky's radon maps can and cannot tell you

The EPA divides the country into three radon zones. They were built from indoor measurements, geology, aerial radioactivity, soil parameters and foundation types, and they are colour-coded on a map published for every state including Kentucky.

The EPA is explicit about what the map is for: to “assist national, state and local organizations to target their resources and to implement radon-resistant building codes”. It is a planning instrument for agencies and code officials. It was never built to be a lookup tool for homeowners.

This is worth quoting rather than paraphrasing. On its own page describing the map, the EPA writes: “The Map of Radon Zones should not be used to determine if individual homes need to be tested. No matter where you live, test your home for radon.”

Kentucky’s map carries the same warning: “Homes with elevated levels of radon have been found in all three zones. All homes should be tested, regardless of zone designation.”

That is the whole point. A zone is a prediction averaged across an entire county. Your house is one building, with one foundation, one set of openings and one way of moving air. Two houses on the same street routinely return different readings, which is exactly why a county-level average cannot stand in for a measurement.

The Inner Bluegrass, the region that includes Fayette, Scott, Woodford, Jessamine, Clark, Madison, Franklin, and Bourbon counties, sits on Ordovician-age limestone rich in uranium-bearing phosphatic minerals. The Kentucky Geological Survey identifies this bedrock as among the most radon-productive in the eastern United States.

Karst dissolution has honeycombed that limestone with sinkholes, underground streams, and dissolved cavities that give radon an efficient network of pathways to the surface. Roughly 55 percent of Kentucky is underlain by rocks capable of developing karst terrain, and the Bluegrass sits in the heart of it.

Every county in the immediate Lexington metro area is classified EPA Zone 1, the highest risk category, predicting average indoor screening levels greater than 4.0 pCi/L. But that classification describes a region, not a house, which is why the EPA’s own advice remains: test.

Results come back in picocuries per litre, written pCi/L. The EPA has set the action level at 4.0 pCi/L; at that level or higher, both the EPA and the Kentucky Cabinet for Health and Family Services recommend installing a mitigation system.

Below it there is still a judgment to make. Any radon level poses some health risk, it is not possible to reduce radon to zero, and the best approach is to lower the level as much as reasonably possible. Between 2.0 and 4.0 the decision usually turns on how the lower level is used, because a storage basement and a bedroom are different exposures at the same reading.

On why any of it matters: the EPA names long-term radon exposure the leading cause of lung cancer among people who have never smoked, estimating roughly 21,000 radon-related lung cancer deaths per year in the United States.

The Kentucky Radon Program, operated through the Cabinet for Health and Family Services, provides free radon test kits to Kentucky residents. The Lexington-Fayette County Health Department also distributes free kits at 650 Newtown Pike during business hours.

We would rather you knew that than not. A free kit is a perfectly good way to find out whether you have a problem at all, and if the reading comes back low you have spent nothing and can retest in a couple of years.

Radon measurement and mitigation professionals in Kentucky should carry certification through the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). The Kentucky Radiation Health Branch within the Cabinet for Health and Family Services oversees radiation protection in the state.

That means the question “are you certified?” has a checkable answer, and it is a fair one to ask of anybody quoting on your house, ourselves included.

Test the house. It is the only step that produces a number about your building rather than your county, and both the EPA and the state say so in almost identical words: a test is the only way to know how much radon is in your home.

If the result is low, nothing further is needed and you retest in a couple of years. If it is high, the design of any system should follow measurements taken inside your house, not the zone your county sits in.