USA Cities Ranked by Indoor Radon Levels

Measured averages from Airthings devices across USA. Action level: 4 pCi/L — the threshold at which remediation is recommended.

Duncannon, Pennsylvania has the highest measured indoor radon of any USA city at 25.5 pCi/L, based on Airthings measurements across 6416 cities.

Updated October 19, 2026

Highest city

25.5pCi/L

Duncannon

USA city average

2.8pCi/L

across 6,416 cities

Above action level

1228/ 6416

cities

Showing the 100 highest of 6416 ranked USA cities. For the full list in one place, open a state ranking below.

USA Cities Ranked by Indoor Radon Levels
#	Location	Avg level	vs action level
1	Duncannon, Pennsylvania	25.5 pCi/L	6.4× over
2	Ashville, Ohio	20.3 pCi/L	5.1× over
3	East Douglas, Massachusetts	19.1 pCi/L	4.8× over
4	Prospect, Pennsylvania	17.6 pCi/L	4.4× over
5	Jacobus, Pennsylvania	17.3 pCi/L	4.3× over
6	Zion, Pennsylvania	16.4 pCi/L	4.1× over
7	Sand Hill, Pennsylvania	15.9 pCi/L	4.0× over
8	Calcutta, Ohio	15.6 pCi/L	3.9× over
9	Greenville, Pennsylvania	15.0 pCi/L	3.8× over
10	Russellton, Pennsylvania	14.9 pCi/L	3.7× over
11	Grafton, North Dakota	14.8 pCi/L	3.7× over
12	Madison, New Hampshire	14.4 pCi/L	3.6× over
13	Palmerton, Pennsylvania	14.1 pCi/L	3.5× over
14	Apollo, Pennsylvania	13.5 pCi/L	3.4× over
15	Dayton, Virginia	13.4 pCi/L	3.4× over
16	Akron, Pennsylvania	13.4 pCi/L	3.3× over
17	Millersburg, Ohio	13.4 pCi/L	3.3× over
18	Kutztown, Pennsylvania	13.3 pCi/L	3.3× over
19	Georgetown, Pennsylvania	13.2 pCi/L	3.3× over
20	Industry, Pennsylvania	13.2 pCi/L	3.3× over
21	Shippensburg, Pennsylvania	13.2 pCi/L	3.3× over
22	Manheim, Pennsylvania	13.2 pCi/L	3.3× over
23	Bowling Green, Kentucky	13.2 pCi/L	3.3× over
24	North Fork Village, Ohio	13.1 pCi/L	3.3× over
25	Angola, Indiana	13.1 pCi/L	3.3× over
26	Big Timber, Montana	13.1 pCi/L	3.3× over
27	Grill, Pennsylvania	13.1 pCi/L	3.3× over
28	China, Maine	12.9 pCi/L	3.2× over
29	Saint Marys, Ohio	12.9 pCi/L	3.2× over
30	Bloomsburg, Pennsylvania	12.9 pCi/L	3.2× over
31	Sun Valley, Pennsylvania	12.8 pCi/L	3.2× over
32	Mosheim, Tennessee	12.6 pCi/L	3.2× over
33	Deadwood, South Dakota	12.5 pCi/L	3.1× over
34	Langdon, North Dakota	12.5 pCi/L	3.1× over
35	Robesonia, Pennsylvania	12.4 pCi/L	3.1× over
36	Danville, Ohio	12.3 pCi/L	3.1× over
37	Old Orchard Beach, Maine	12.3 pCi/L	3.1× over
38	LaFollette, Tennessee	12.2 pCi/L	3.1× over
39	Atlantic, Iowa	12.0 pCi/L	3.0× over
40	Doe Valley, Kentucky	12.0 pCi/L	3.0× over
41	Hooksett, New Hampshire	12.0 pCi/L	3.0× over
42	West Hills, Pennsylvania	12.0 pCi/L	3.0× over
43	Cherryville, Pennsylvania	11.7 pCi/L	2.9× over
44	Lebanon South, Pennsylvania	11.7 pCi/L	2.9× over
45	Shrewsbury, Pennsylvania	11.7 pCi/L	2.9× over
46	Hughesville, Pennsylvania	11.6 pCi/L	2.9× over
47	Heath, Ohio	11.6 pCi/L	2.9× over
48	Conway, New Hampshire	11.4 pCi/L	2.9× over
49	Strasburg, Pennsylvania	11.3 pCi/L	2.8× over
50	Centre Hall, Pennsylvania	11.3 pCi/L	2.8× over
51	Trentwood, Washington	11.3 pCi/L	2.8× over
52	Leesport, Pennsylvania	11.3 pCi/L	2.8× over
53	DuBois, Pennsylvania	11.3 pCi/L	2.8× over
54	Cementon, Pennsylvania	11.2 pCi/L	2.8× over
55	Wrightsville, Pennsylvania	11.2 pCi/L	2.8× over
56	Okauchee Lake, Wisconsin	11.0 pCi/L	2.7× over
57	Peru, Indiana	10.9 pCi/L	2.7× over
58	Barneveld, Wisconsin	10.9 pCi/L	2.7× over
59	Rushville, Indiana	10.9 pCi/L	2.7× over
60	Quarryville, Pennsylvania	10.9 pCi/L	2.7× over
61	Stewartstown, Pennsylvania	10.7 pCi/L	2.7× over
62	Factoryville, Pennsylvania	10.6 pCi/L	2.6× over
63	Scobey, Montana	10.5 pCi/L	2.6× over
64	Idaho Springs, Colorado	10.4 pCi/L	2.6× over
65	Moorefield, West Virginia	10.3 pCi/L	2.6× over
66	Lee, New Hampshire	10.3 pCi/L	2.6× over
67	Rutherford, Pennsylvania	10.2 pCi/L	2.6× over
68	La Vale, Maryland	10.2 pCi/L	2.6× over
69	Lewistown, Montana	10.2 pCi/L	2.6× over
70	New Glarus, Wisconsin	10.2 pCi/L	2.5× over
71	Spencer, Iowa	10.1 pCi/L	2.5× over
72	Williamsport, Maryland	10.1 pCi/L	2.5× over
73	Spirit Lake, Idaho	10.1 pCi/L	2.5× over
74	Spry, Pennsylvania	10.1 pCi/L	2.5× over
75	West Yellowstone, Montana	10.0 pCi/L	2.5× over
76	Frazeysburg, Ohio	10.0 pCi/L	2.5× over
77	Mountville, Pennsylvania	10.0 pCi/L	2.5× over
78	Harmony, Minnesota	10.0 pCi/L	2.5× over
79	Granite Falls, Washington	10.0 pCi/L	2.5× over
80	Gambier, Ohio	9.9 pCi/L	2.5× over
81	Beaver Falls, Pennsylvania	9.9 pCi/L	2.5× over
82	Windsor, Pennsylvania	9.9 pCi/L	2.5× over
83	Limestone, Maine	9.9 pCi/L	2.5× over
84	Lebanon Junction, Kentucky	9.9 pCi/L	2.5× over
85	Gate City, Virginia	9.9 pCi/L	2.5× over
86	Bellefontaine, Ohio	9.8 pCi/L	2.4× over
87	Glen Rock, Pennsylvania	9.8 pCi/L	2.4× over
88	Spurgeon, Tennessee	9.8 pCi/L	2.4× over
89	Sinking Spring, Pennsylvania	9.8 pCi/L	2.4× over
90	Obetz, Ohio	9.7 pCi/L	2.4× over
91	Dallas Center, Iowa	9.7 pCi/L	2.4× over
92	Riverside, Pennsylvania	9.7 pCi/L	2.4× over
93	Jermyn, Pennsylvania	9.7 pCi/L	2.4× over
94	Ossipee, New Hampshire	9.6 pCi/L	2.4× over
95	Clayton, New York	9.6 pCi/L	2.4× over
96	Eureka, Montana	9.5 pCi/L	2.4× over
97	Lyndon, Kentucky	9.5 pCi/L	2.4× over
98	Shanor-Northvue, Pennsylvania	9.5 pCi/L	2.4× over
99	Janesville, Minnesota	9.5 pCi/L	2.4× over
100	Spirit Lake, Iowa	9.5 pCi/L	2.4× over

See all States ranked by radon level