West side, east side: radon data across Hamilton County

Cincinnati sorts itself by side of town, and plenty of people assume radon does too. The Ohio Department of Health's ZIP-level test data tells a more interesting story. The Mill Creek is not the dividing line. Distance from the old city core is. Here is what the numbers show for west side and east side neighborhoods, and what each common house type needs from a test.

The west side, ZIP by ZIP

These figures come from pre-mitigation tests reported by Ohio-licensed radon professionals since 2010. "Median" is the middle result, and the percentage is the share of tests above EPA's 4.0 pCi/L action level.

• Westwood and Cheviot (45211): median 1.8 pCi/L, 16 percent of 854 tests above 4.0
• West Price Hill, Covedale, and part of Delhi Township (45238): median 1.8, 15 percent of 1,068
• College Hill and part of Finneytown (45224): median 2.0, 20 percent of 654
• Mount Healthy, North College Hill, and Springfield Township (45231): median 2.1, 21 percent of 1,127
• Mount Airy, Groesbeck, and White Oak (45239): median 2.0, 19 percent of 722
• Sayler Park and part of Delhi (45233): median 2.4, 23 percent of 517
• Colerain Township around Northgate (45251): median 1.5, 17 percent of 754
• Colerain Township around Dent and Taylor Creek (45247): median 2.3, 25 percent of 1,016
• Dunlap and Dry Ridge in northern Colerain (45252): median 2.9, 32 percent of 215
• Cleves, Miamitown, and Hooven (45002): median 2.7, 33 percent of 411
• Harrison (45030): median 3.7, 48 percent of 783

The east side, ZIP by ZIP

• Walnut Hills and East Walnut Hills (45206): median 1.3, 9 percent of 512
• Oakley (45209): median 1.6, 9 percent of 1,181
• Columbia Tusculum, East End, and Linwood (45226): median 1.6, 11 percent of 725
• Hyde Park and Mt. Lookout (45208): median 1.9, 14 percent of 2,419
• Roselawn, Bond Hill, and Golf Manor (45237): median 2.2, 22 percent of 568
• Mt. Washington and California (45230): median 2.1, 21 percent of 2,207
• Madisonville, Mariemont, and Fairfax (45227): median 2.3, 26 percent of 1,544
• Madeira and Indian Hill (45243): median 2.3, 24 percent of 2,266
• Blue Ash and Montgomery (45242): median 2.4, 27 percent of 2,423
• Symmes Township (45249): median 2.4, 29 percent of 1,256
• Anderson Township and Newtown (45244): median 2.6, 31 percent of 2,198
• Terrace Park (45174): median 2.5, 32 percent of 359

The pattern is in versus out, not west versus east

Line the two lists up and they look alike. The neighborhoods nearest downtown on both sides, Westwood and West Price Hill in the west and Walnut Hills and Oakley in the east, sit in the single digits to mid-teens. The ring farther out, College Hill and Mount Healthy to the northwest and Mt. Washington and Roselawn to the east, lands around 20 percent. The outer suburbs and river towns climb from the mid-twenties into the thirties, and Harrison posts the highest share of any Hamilton County ZIP with more than a few dozen tests, 48 percent.

Whichever side of town you live on, a house farther from the core has better odds of a high result in this data. The same climb shows up past the county line, where Mason, West Chester Township, and Loveland each report more than a third of tests above 4.0.

What might be behind it

The dashboard counts results; it does not explain them. Several factors plausibly contribute, and it is worth being clear that none is proven by this data alone.

Soil and sediment. The 1993 U.S. Geological Survey assessment of Ohio's radon potential noted that homes over glacial outwash and alluvium had the highest radon measurements, probably because gas moves easily through coarse, permeable sediment, while homes on end moraines had the lowest. Harrison, Cleves, and Miamitown sit along the Great Miami and Whitewater river valleys, where sand and gravel fill much of the valley floor.

House age and design. The inner neighborhoods are dominated by older houses, while the outer ring is mostly postwar ranches, split-levels, and later subdivisions with full basements. Basement size, slab condition, and how tightly a house is built all change how hard it pulls on the soil.

Who gets tested. Much professional testing happens during home sales, and sales activity is not spread evenly across the county. A neighborhood where more houses change hands will report more tests, and possibly different ones.

Testing the house types you find on each side

• Older brick or frame house with a full basement, common in Westwood, Price Hill, Walnut Hills, and Hyde Park: test in the basement if anyone uses it, otherwise on the first floor, and keep the kit well away from the sump and floor drain.
• Postwar ranch on a slab or crawl space, found in many first-ring and second-ring neighborhoods: test on the main living level in a bedroom or family room.
• Split-level, found on both sides: test the lower level and, if there is a room over a crawl space, that room too. Ohio's protocol has professionals test each foundation type separately.
• Newer subdivision house with a full basement, the typical outer-suburb build: look for a capped radon pipe in the basement before you test, since a passive system changes what the fix would cost.

Look up your own ZIP in our radon levels by ZIP code table, and read how to interpret those numbers before drawing conclusions from them. For neighborhood notes, see the Cincinnati area page or Anderson Township. When you are ready to test, the radon testing page covers kits and professional tests, and we are a call or text away if your result lands above 4.0.