Connecticut Cities Ranked by Indoor Radon Levels

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

Northwest Harwinton has the highest measured indoor radon in Connecticut at 8.1 pCi/L, based on Airthings measurements across 142 cities.

Updated October 19, 2026

Highest city

8.1pCi/L

Northwest Harwinton

Connecticut city average

2.3pCi/L

across 142 cities

Above action level

12/ 142

cities

Connecticut Cities Ranked by Indoor Radon Levels
#	Location	Avg level	vs action level
1	Northwest Harwinton	8.1 pCi/L	2.0× over
2	Derby	6.8 pCi/L	1.7× over
3	Ansonia	6.0 pCi/L	1.5× over
4	Montville Center	5.3 pCi/L	1.3× over
5	Danielson	5.0 pCi/L	1.3× over
6	East Hampton	4.9 pCi/L	1.2× over
7	Old Mystic	4.7 pCi/L	1.2× over
8	Cos Cob	4.5 pCi/L	1.1× over
9	Baltic	4.4 pCi/L	1.1× over
10	South Woodstock	4.3 pCi/L	1.1× over
11	Windham	4.3 pCi/L	1.1× over
12	Madison Center	4.0 pCi/L	1.0× over
✓ Below EPA action level (4 pCi/L)
13	New Hartford Center	4.0 pCi/L	1.0× under
14	Branford Center	3.9 pCi/L	1.0× under
15	Heritage Village	3.6 pCi/L	0.9× under
16	Georgetown	3.6 pCi/L	0.9× under
17	Seymour	3.4 pCi/L	0.8× under
18	Durham	3.3 pCi/L	0.8× under
19	Woodmont	3.2 pCi/L	0.8× under
20	Jewett City	3.2 pCi/L	0.8× under
21	Windsor Locks	3.1 pCi/L	0.8× under
22	Woodbury Center	3.1 pCi/L	0.8× under
23	Prospect	3.1 pCi/L	0.8× under
24	Wolcott	3.1 pCi/L	0.8× under
25	Clinton	3.0 pCi/L	0.8× under
26	West Torrington	3.0 pCi/L	0.8× under
27	North Branford	3.0 pCi/L	0.7× under
28	East Haven	3.0 pCi/L	0.7× under
29	Central Waterford	2.9 pCi/L	0.7× under
30	New Milford	2.9 pCi/L	0.7× under
31	Plainfield	2.9 pCi/L	0.7× under
32	Lake Pocotopaug	2.9 pCi/L	0.7× under
33	Ledyard Center	2.8 pCi/L	0.7× under
34	City of Milford (balance)	2.8 pCi/L	0.7× under
35	Pawcatuck	2.8 pCi/L	0.7× under
36	Ellington	2.7 pCi/L	0.7× under
37	New Preston	2.7 pCi/L	0.7× under
38	Norwich	2.7 pCi/L	0.7× under
39	Oxford	2.6 pCi/L	0.7× under
40	Sherman	2.6 pCi/L	0.7× under
41	Colchester	2.6 pCi/L	0.6× under
42	Kent	2.6 pCi/L	0.6× under
43	Wilton	2.6 pCi/L	0.6× under
44	Cromwell	2.5 pCi/L	0.6× under
45	Southbury	2.5 pCi/L	0.6× under
46	Shelton	2.5 pCi/L	0.6× under
47	Guilford	2.5 pCi/L	0.6× under
48	Farmington	2.5 pCi/L	0.6× under
49	Bethlehem Village	2.4 pCi/L	0.6× under
50	North Haven	2.4 pCi/L	0.6× under
51	Waterbury	2.4 pCi/L	0.6× under
52	Middlebury	2.4 pCi/L	0.6× under
53	Torrington	2.3 pCi/L	0.6× under
54	Southport	2.3 pCi/L	0.6× under
55	Winsted	2.3 pCi/L	0.6× under
56	Terryville	2.3 pCi/L	0.6× under
57	Middletown	2.3 pCi/L	0.6× under
58	Tariffville	2.3 pCi/L	0.6× under
59	Byram	2.3 pCi/L	0.6× under
60	Plainfield Village	2.3 pCi/L	0.6× under
61	Stamford	2.2 pCi/L	0.6× under
62	Moosup	2.2 pCi/L	0.6× under
63	Preston City	2.2 pCi/L	0.6× under
64	Trumbull	2.2 pCi/L	0.6× under
65	Newtown	2.2 pCi/L	0.6× under
66	Oakville	2.2 pCi/L	0.6× under
67	Orange	2.2 pCi/L	0.6× under
68	Niantic	2.2 pCi/L	0.6× under
69	Wallingford	2.2 pCi/L	0.5× under
70	Bridgeport	2.1 pCi/L	0.5× under
71	Stratford	2.1 pCi/L	0.5× under
72	Old Saybrook Center	2.1 pCi/L	0.5× under
73	Westbrook Center	2.1 pCi/L	0.5× under
74	Riverside	2.1 pCi/L	0.5× under
75	Westport	2.1 pCi/L	0.5× under
76	Wethersfield	2.1 pCi/L	0.5× under
77	Glenville	2.0 pCi/L	0.5× under
78	Ridgefield	2.0 pCi/L	0.5× under
79	East Norwalk	2.0 pCi/L	0.5× under
80	Cheshire Village	2.0 pCi/L	0.5× under
81	Hamden	1.9 pCi/L	0.5× under
82	Higganum	1.9 pCi/L	0.5× under
83	Collinsville	1.9 pCi/L	0.5× under
84	Kensington	1.9 pCi/L	0.5× under
85	North Stamford	1.9 pCi/L	0.5× under
86	Canaan	1.9 pCi/L	0.5× under
87	Meriden	1.9 pCi/L	0.5× under
88	Willimantic	1.9 pCi/L	0.5× under
89	Fairfield	1.8 pCi/L	0.5× under
90	Darien	1.8 pCi/L	0.5× under
91	Greenwich	1.8 pCi/L	0.5× under
92	Hebron	1.8 pCi/L	0.4× under
93	New Canaan	1.8 pCi/L	0.4× under
94	Canton Valley	1.8 pCi/L	0.4× under
95	Danbury	1.7 pCi/L	0.4× under
96	Watertown	1.7 pCi/L	0.4× under
97	Coventry Lake	1.7 pCi/L	0.4× under
98	Manchester	1.7 pCi/L	0.4× under
99	Groton	1.7 pCi/L	0.4× under
100	Madison	1.6 pCi/L	0.4× under
101	Bristol	1.6 pCi/L	0.4× under
102	Mansfield City	1.6 pCi/L	0.4× under
103	Norwalk	1.6 pCi/L	0.4× under
104	Simsbury Center	1.6 pCi/L	0.4× under
105	Tolland	1.6 pCi/L	0.4× under
106	Gales Ferry	1.6 pCi/L	0.4× under
107	Plainville	1.6 pCi/L	0.4× under
108	Woodbridge	1.6 pCi/L	0.4× under
109	Old Greenwich	1.5 pCi/L	0.4× under
110	Storrs	1.5 pCi/L	0.4× under
111	Bethel	1.5 pCi/L	0.4× under
112	North Granby	1.5 pCi/L	0.4× under
113	Glastonbury Center	1.5 pCi/L	0.4× under
114	New Haven	1.4 pCi/L	0.4× under
115	Long Hill	1.4 pCi/L	0.3× under
116	Blue Hills	1.4 pCi/L	0.3× under
117	Newington	1.4 pCi/L	0.3× under
118	Suffield Depot	1.4 pCi/L	0.3× under
119	Rockville	1.4 pCi/L	0.3× under
120	Milford	1.4 pCi/L	0.3× under
121	Weatogue	1.3 pCi/L	0.3× under
122	Mystic	1.3 pCi/L	0.3× under
123	Terramuggus	1.3 pCi/L	0.3× under
124	Deep River Center	1.2 pCi/L	0.3× under
125	Salmon Brook	1.2 pCi/L	0.3× under
126	Wallingford Center	1.2 pCi/L	0.3× under
127	New Britain	1.2 pCi/L	0.3× under
128	Essex Village	1.1 pCi/L	0.3× under
129	Poquonock Bridge	1.1 pCi/L	0.3× under
130	West Hartford	1.1 pCi/L	0.3× under
131	East Hartford	1.1 pCi/L	0.3× under
132	Litchfield	1.1 pCi/L	0.3× under
133	Cheshire	1.0 pCi/L	0.3× under
134	Naugatuck	1.0 pCi/L	0.3× under
135	Moodus	1.0 pCi/L	0.3× under
136	Pemberwick	0.9 pCi/L	0.2× under
137	Branford	0.8 pCi/L	0.2× under
138	Glastonbury	0.8 pCi/L	0.2× under
139	West Haven	0.8 pCi/L	0.2× under
140	South Coventry	0.7 pCi/L	0.2× under
141	South Windsor	0.6 pCi/L	0.2× under
142	Hartford	0.6 pCi/L	0.1× under

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