Maryland Cities Ranked by Indoor Radon Levels

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

Williamsport has the highest measured indoor radon in Maryland at 10.7 pCi/L, based on Airthings measurements across 178 cities.

Updated August 16, 2026

Highest city

10.7pCi/L

Williamsport

Maryland city average

2.6pCi/L

across 178 cities

Above action level

21/ 178

cities

Maryland Cities Ranked by Indoor Radon Levels
#	Location	Avg level	Monitors	vs action level
1	Williamsport	10.7 pCi/L	19	2.7× over
2	Green Valley	7.6 pCi/L	21	1.9× over
3	Manchester	7.5 pCi/L	12	1.9× over
4	Saint James	7.2 pCi/L	9	1.8× over
5	Urbana	6.1 pCi/L	40	1.5× over
6	Mount Airy	6.1 pCi/L	60	1.5× over
7	Bartonsville	5.8 pCi/L	12	1.4× over
8	Londontowne	4.9 pCi/L	16	1.2× over
9	Huntingtown	4.9 pCi/L	14	1.2× over
10	Keedysville	4.8 pCi/L	15	1.2× over
11	Paramount-Long Meadow	4.7 pCi/L	6	1.2× over
12	Westminster	4.6 pCi/L	59	1.1× over
13	Friendly	4.5 pCi/L	7	1.1× over
14	Robinwood	4.5 pCi/L	14	1.1× over
15	Dunkirk Town Center	4.5 pCi/L	15	1.1× over
16	Chesapeake Beach	4.3 pCi/L	19	1.1× over
17	Maugansville	4.3 pCi/L	11	1.1× over
18	Chesapeake Ranch Estates	4.2 pCi/L	6	1.0× over
19	Davidsonville	4.2 pCi/L	27	1.0× over
20	New Windsor	4.0 pCi/L	19	1.0× over
21	Kingsville	4.0 pCi/L	6	1.0× over
✓ Below EPA action level (4 pCi/L)
22	Pikesville	4.0 pCi/L	31	1.0× under
23	Hagerstown	3.9 pCi/L	30	1.0× under
24	Mellwood	3.8 pCi/L	6	1.0× under
25	Hampstead	3.8 pCi/L	16	1.0× under
26	Hughesville	3.7 pCi/L	7	0.9× under
27	Bel Air North	3.7 pCi/L	28	0.9× under
28	Spencerville	3.7 pCi/L	7	0.9× under
29	Fairland	3.6 pCi/L	10	0.9× under
30	Oakland	3.6 pCi/L	9	0.9× under
31	Langley Park	3.6 pCi/L	6	0.9× under
32	Naval Academy	3.6 pCi/L	7	0.9× under
33	Crownsville	3.5 pCi/L	16	0.9× under
34	Hunt Valley	3.5 pCi/L	22	0.9× under
35	Randallstown	3.5 pCi/L	11	0.9× under
36	Colesville	3.5 pCi/L	19	0.9× under
37	Upper Marlboro	3.4 pCi/L	11	0.9× under
38	Ashton-Sandy Spring	3.4 pCi/L	6	0.9× under
39	Owings	3.4 pCi/L	21	0.9× under
40	Sykesville	3.4 pCi/L	103	0.9× under
41	Dunkirk	3.4 pCi/L	12	0.8× under
42	Cape Saint Claire	3.4 pCi/L	26	0.8× under
43	Elkton	3.4 pCi/L	25	0.8× under
44	Garrison	3.3 pCi/L	10	0.8× under
45	Frostburg	3.3 pCi/L	6	0.8× under
46	Highland	3.3 pCi/L	95	0.8× under
47	Taneytown	3.3 pCi/L	19	0.8× under
48	Huntingtown Town Center	3.2 pCi/L	6	0.8× under
49	Hillsmere Shores	3.2 pCi/L	11	0.8× under
50	La Plata	3.2 pCi/L	14	0.8× under
51	Burtonsville	3.2 pCi/L	12	0.8× under
52	Cumberland	3.1 pCi/L	11	0.8× under
53	Deale	3.1 pCi/L	8	0.8× under
54	Damascus	3.1 pCi/L	44	0.8× under
55	Bel Air	3.1 pCi/L	21	0.8× under
56	Brunswick	3.1 pCi/L	15	0.8× under
57	Mays Chapel	3.0 pCi/L	37	0.8× under
58	Aberdeen	3.0 pCi/L	15	0.8× under
59	Walkersville	3.0 pCi/L	21	0.8× under
60	Kemp Mill	3.0 pCi/L	14	0.7× under
61	Lutherville	3.0 pCi/L	25	0.7× under
62	Clover Hill	3.0 pCi/L	31	0.7× under
63	Fort Washington	3.0 pCi/L	9	0.7× under
64	Annapolis	2.9 pCi/L	27	0.7× under
65	White Oak	2.9 pCi/L	16	0.7× under
66	Adamstown	2.9 pCi/L	10	0.7× under
67	Eldersburg	2.8 pCi/L	51	0.7× under
68	Prince Frederick	2.8 pCi/L	12	0.7× under
69	Rising Sun	2.8 pCi/L	7	0.7× under
70	Linganore	2.8 pCi/L	10	0.7× under
71	Columbia	2.8 pCi/L	140	0.7× under
72	Leonardtown	2.8 pCi/L	22	0.7× under
73	Gambrills	2.8 pCi/L	47	0.7× under
74	Arnold	2.7 pCi/L	23	0.7× under
75	Fulton	2.6 pCi/L	28	0.7× under
76	Frederick	2.6 pCi/L	67	0.7× under
77	Mountain Lake Park	2.6 pCi/L	7	0.7× under
78	Savage	2.6 pCi/L	22	0.7× under
79	Jarrettsville	2.6 pCi/L	31	0.6× under
80	Owings Mills	2.5 pCi/L	14	0.6× under
81	Darnestown	2.5 pCi/L	36	0.6× under
82	Riverside	2.4 pCi/L	90	0.6× under
83	Bel Air South	2.4 pCi/L	15	0.6× under
84	Glenn Dale	2.4 pCi/L	18	0.6× under
85	Reisterstown	2.4 pCi/L	29	0.6× under
86	Catonsville	2.3 pCi/L	25	0.6× under
87	Ellicott City	2.3 pCi/L	67	0.6× under
88	North Laurel	2.3 pCi/L	36	0.6× under
89	Point of Rocks	2.3 pCi/L	15	0.6× under
90	Myersville	2.2 pCi/L	6	0.6× under
91	Odenton	2.2 pCi/L	31	0.5× under
92	North East	2.2 pCi/L	14	0.5× under
93	Parole	2.2 pCi/L	17	0.5× under
94	Potomac	2.2 pCi/L	104	0.5× under
95	Rockville	2.2 pCi/L	108	0.5× under
96	California	2.2 pCi/L	15	0.5× under
97	Cockeysville	2.2 pCi/L	12	0.5× under
98	Fallston	2.1 pCi/L	19	0.5× under
99	Severna Park	2.1 pCi/L	37	0.5× under
100	Germantown	2.1 pCi/L	67	0.5× under
101	Forest Glen	2.1 pCi/L	34	0.5× under
102	Crofton	2.0 pCi/L	48	0.5× under
103	North Kensington	2.0 pCi/L	15	0.5× under
104	Timonium	2.0 pCi/L	18	0.5× under
105	Hyattsville	2.0 pCi/L	10	0.5× under
106	Derwood	2.0 pCi/L	15	0.5× under
107	Herald Harbor	2.0 pCi/L	6	0.5× under
108	Chestertown	2.0 pCi/L	7	0.5× under
109	Brookmont	2.0 pCi/L	84	0.5× under
110	Carney	2.0 pCi/L	9	0.5× under
111	Lexington Park	2.0 pCi/L	22	0.5× under
112	Redland	2.0 pCi/L	27	0.5× under
113	South Bel Air	1.9 pCi/L	23	0.5× under
114	Clarksburg	1.9 pCi/L	61	0.5× under
115	Four Corners	1.9 pCi/L	35	0.5× under
116	Cabin John	1.8 pCi/L	58	0.5× under
117	Kensington	1.8 pCi/L	19	0.4× under
118	Towson	1.8 pCi/L	64	0.4× under
119	North Potomac	1.8 pCi/L	43	0.4× under
120	Arden on the Severn	1.8 pCi/L	11	0.4× under
121	Spring Ridge	1.8 pCi/L	39	0.4× under
122	Ilchester	1.7 pCi/L	30	0.4× under
123	Somerset	1.7 pCi/L	13	0.4× under
124	Middletown	1.7 pCi/L	13	0.4× under
125	Rossmoor	1.7 pCi/L	19	0.4× under
126	Jessup	1.7 pCi/L	16	0.4× under
127	Charlestown	1.6 pCi/L	18	0.4× under
128	Perry Hall	1.6 pCi/L	15	0.4× under
129	Chevy Chase	1.6 pCi/L	41	0.4× under
130	Travilah	1.6 pCi/L	16	0.4× under
131	Havre de Grace	1.6 pCi/L	14	0.4× under
132	Riva	1.6 pCi/L	17	0.4× under
133	Wheaton	1.6 pCi/L	8	0.4× under
134	West Elkridge	1.6 pCi/L	9	0.4× under
135	Bethesda	1.5 pCi/L	84	0.4× under
136	South Kensington	1.5 pCi/L	27	0.4× under
137	Montgomery Village	1.5 pCi/L	41	0.4× under
138	Poolesville	1.5 pCi/L	14	0.4× under
139	Silver Spring	1.5 pCi/L	49	0.4× under
140	Hampton	1.5 pCi/L	15	0.4× under
141	Laurel	1.5 pCi/L	11	0.4× under
142	Takoma Park	1.5 pCi/L	39	0.4× under
143	Olney	1.5 pCi/L	44	0.4× under
144	Friendship Village	1.5 pCi/L	41	0.4× under
145	North Bethesda	1.5 pCi/L	51	0.4× under
146	Waldorf	1.5 pCi/L	8	0.4× under
147	Layhill	1.4 pCi/L	12	0.4× under
148	White Marsh	1.4 pCi/L	6	0.3× under
149	Lake Shore	1.3 pCi/L	8	0.3× under
150	Severn	1.3 pCi/L	23	0.3× under
151	Baltimore	1.3 pCi/L	97	0.3× under
152	Brooklyn Park	1.3 pCi/L	9	0.3× under
153	Glenmont	1.2 pCi/L	20	0.3× under
154	Gaithersburg	1.2 pCi/L	86	0.3× under
155	South Gate	1.2 pCi/L	11	0.3× under
156	Chevy Chase Village	1.2 pCi/L	21	0.3× under
157	Ballenger Creek	1.2 pCi/L	14	0.3× under
158	Maryland City	1.2 pCi/L	8	0.3× under
159	Chillum	1.1 pCi/L	25	0.3× under
160	Pasadena	1.1 pCi/L	12	0.3× under
161	South Laurel	1.1 pCi/L	12	0.3× under
162	University Park	1.1 pCi/L	7	0.3× under
163	Aspen Hill	1.1 pCi/L	9	0.3× under
164	Cloverly	1.1 pCi/L	14	0.3× under
165	Bennsville	1.0 pCi/L	6	0.2× under
166	West Laurel	1.0 pCi/L	11	0.2× under
167	Green Haven	0.9 pCi/L	23	0.2× under
168	Parkville	0.9 pCi/L	18	0.2× under
169	Mount Rainier	0.9 pCi/L	34	0.2× under
170	Chester	0.8 pCi/L	6	0.2× under
171	Elkridge	0.8 pCi/L	8	0.2× under
172	Glen Burnie	0.8 pCi/L	15	0.2× under
173	Fort Meade	0.7 pCi/L	6	0.2× under
174	Brandywine	0.7 pCi/L	7	0.2× under
175	Lansdowne	0.5 pCi/L	6	0.1× under
176	Milford Mill	0.4 pCi/L	6	0.1× under
177	College Park	0.4 pCi/L	6	0.1× under
178	Dundalk	0.3 pCi/L	6	0.1× under

See USA cities ranked by radon level See all States ranked by radon level