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 6191 cities.

Updated August 30, 2026

Highest city

25.5pCi/L

Duncannon

USA city average

2.8pCi/L

across 6,191 cities

Above action level

1198/ 6191

cities

Showing the 100 highest of 6191 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	Sand Hill, Pennsylvania	17.6 pCi/L	4.4× over
6	Jacobus, Pennsylvania	17.3 pCi/L	4.3× over
7	Calcutta, Ohio	16.4 pCi/L	4.1× over
8	Zion, Pennsylvania	16.4 pCi/L	4.1× over
9	Dayton, Virginia	16.3 pCi/L	4.1× over
10	Russellton, Pennsylvania	15.7 pCi/L	3.9× over
11	Kutztown, Pennsylvania	15.6 pCi/L	3.9× over
12	Greenville, Pennsylvania	15.0 pCi/L	3.8× over
13	Grafton, North Dakota	14.8 pCi/L	3.7× over
14	Atlantic, Iowa	14.4 pCi/L	3.6× over
15	Madison, New Hampshire	14.4 pCi/L	3.6× over
16	Palmerton, Pennsylvania	14.1 pCi/L	3.5× over
17	Manheim, Pennsylvania	13.6 pCi/L	3.4× over
18	Apollo, Pennsylvania	13.5 pCi/L	3.4× over
19	Bowling Green, Kentucky	13.4 pCi/L	3.4× over
20	Akron, Pennsylvania	13.4 pCi/L	3.3× over
21	Millersburg, Ohio	13.4 pCi/L	3.3× over
22	Georgetown, Pennsylvania	13.2 pCi/L	3.3× over
23	Shippensburg, Pennsylvania	13.2 pCi/L	3.3× over
24	Big Timber, Montana	13.1 pCi/L	3.3× over
25	Grill, Pennsylvania	13.1 pCi/L	3.3× over
26	China, Maine	12.9 pCi/L	3.2× over
27	Saint Marys, Ohio	12.9 pCi/L	3.2× over
28	Bloomsburg, Pennsylvania	12.9 pCi/L	3.2× over
29	Sun Valley, Pennsylvania	12.8 pCi/L	3.2× over
30	Mosheim, Tennessee	12.6 pCi/L	3.2× over
31	Deadwood, South Dakota	12.5 pCi/L	3.1× over
32	Langdon, North Dakota	12.5 pCi/L	3.1× over
33	Robesonia, Pennsylvania	12.4 pCi/L	3.1× over
34	Old Orchard Beach, Maine	12.3 pCi/L	3.1× over
35	Industry, Pennsylvania	12.1 pCi/L	3.0× over
36	Doe Valley, Kentucky	12.0 pCi/L	3.0× over
37	West Hills, Pennsylvania	12.0 pCi/L	3.0× over
38	Conway, New Hampshire	11.8 pCi/L	3.0× over
39	Cherryville, Pennsylvania	11.7 pCi/L	2.9× over
40	Lebanon South, Pennsylvania	11.7 pCi/L	2.9× over
41	Okauchee Lake, Wisconsin	11.7 pCi/L	2.9× over
42	Lewistown, Pennsylvania	11.7 pCi/L	2.9× over
43	Shrewsbury, Pennsylvania	11.7 pCi/L	2.9× over
44	Hughesville, Pennsylvania	11.6 pCi/L	2.9× over
45	Heath, Ohio	11.6 pCi/L	2.9× over
46	Quarryville, Pennsylvania	11.5 pCi/L	2.9× over
47	Strasburg, Pennsylvania	11.3 pCi/L	2.8× over
48	Centre Hall, Pennsylvania	11.3 pCi/L	2.8× over
49	Trentwood, Washington	11.3 pCi/L	2.8× over
50	Barneveld, Wisconsin	11.2 pCi/L	2.8× over
51	Cementon, Pennsylvania	11.2 pCi/L	2.8× over
52	Wrightsville, Pennsylvania	11.2 pCi/L	2.8× over
53	Granite Falls, Washington	11.0 pCi/L	2.7× over
54	Peru, Indiana	10.9 pCi/L	2.7× over
55	Rushville, Indiana	10.9 pCi/L	2.7× over
56	Osage, Iowa	10.9 pCi/L	2.7× over
57	Idaho Springs, Colorado	10.8 pCi/L	2.7× over
58	Hooksett, New Hampshire	10.8 pCi/L	2.7× over
59	Stewartstown, Pennsylvania	10.7 pCi/L	2.7× over
60	Yorktown, Indiana	10.7 pCi/L	2.7× over
61	Factoryville, Pennsylvania	10.6 pCi/L	2.6× over
62	Clayton, New York	10.6 pCi/L	2.6× over
63	Spirit Lake, Idaho	10.5 pCi/L	2.6× over
64	Scobey, Montana	10.5 pCi/L	2.6× over
65	Lolo, Montana	10.5 pCi/L	2.6× over
66	Danville, Ohio	10.3 pCi/L	2.6× over
67	Spencer, Iowa	10.3 pCi/L	2.6× over
68	Spry, Pennsylvania	10.3 pCi/L	2.6× over
69	Moorefield, West Virginia	10.3 pCi/L	2.6× over
70	Lee, New Hampshire	10.3 pCi/L	2.6× over
71	Rutherford, Pennsylvania	10.2 pCi/L	2.6× over
72	Lewistown, Montana	10.2 pCi/L	2.6× over
73	Mountville, Pennsylvania	10.2 pCi/L	2.6× over
74	Battle Ground, Indiana	10.2 pCi/L	2.5× over
75	New Glarus, Wisconsin	10.2 pCi/L	2.5× over
76	Honey Brook, Pennsylvania	10.1 pCi/L	2.5× over
77	Williamsport, Maryland	10.1 pCi/L	2.5× over
78	Frazeysburg, Ohio	10.0 pCi/L	2.5× over
79	Harmony, Minnesota	10.0 pCi/L	2.5× over
80	Garden View, Pennsylvania	10.0 pCi/L	2.5× over
81	Gambier, Ohio	9.9 pCi/L	2.5× over
82	North Conway, New Hampshire	9.9 pCi/L	2.5× over
83	Beaver Falls, Pennsylvania	9.9 pCi/L	2.5× over
84	Windsor, Pennsylvania	9.9 pCi/L	2.5× over
85	Gate City, Virginia	9.9 pCi/L	2.5× over
86	Cornwall, Pennsylvania	9.8 pCi/L	2.5× over
87	Grinnell, Iowa	9.8 pCi/L	2.5× over
88	Bellefontaine, Ohio	9.8 pCi/L	2.4× over
89	Glen Rock, Pennsylvania	9.8 pCi/L	2.4× over
90	Spurgeon, Tennessee	9.8 pCi/L	2.4× over
91	Sinking Spring, Pennsylvania	9.8 pCi/L	2.4× over
92	Dallas Center, Iowa	9.7 pCi/L	2.4× over
93	Riverside, Pennsylvania	9.7 pCi/L	2.4× over
94	Franklin, Maine	9.6 pCi/L	2.4× over
95	Priest River, Idaho	9.6 pCi/L	2.4× over
96	Ossipee, New Hampshire	9.6 pCi/L	2.4× over
97	Eureka, Montana	9.5 pCi/L	2.4× over
98	Janesville, Minnesota	9.5 pCi/L	2.4× over
99	Spirit Lake, Iowa	9.5 pCi/L	2.4× over
100	Chamberlain, South Dakota	9.4 pCi/L	2.4× over

See all States ranked by radon level