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 143 cities.

Updated October 25, 2026

Highest city

8.1pCi/L

Northwest Harwinton

Connecticut city average

2.3pCi/L

across 143 cities

Above action level

13/ 143

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
13	New Hartford Center	4.0 pCi/L	1.0× over
✓ Below EPA action level (4 pCi/L)
14	Branford Center	3.9 pCi/L	1.0× under
15	Heritage Village	3.6 pCi/L	0.9× under
16	Georgetown	3.5 pCi/L	0.9× under
17	Seymour	3.4 pCi/L	0.9× under
18	Durham	3.3 pCi/L	0.8× under
19	Woodmont	3.2 pCi/L	0.8× under
20	Killingly Center	3.2 pCi/L	0.8× under
21	Jewett City	3.2 pCi/L	0.8× under
22	Windsor Locks	3.1 pCi/L	0.8× under
23	Woodbury Center	3.1 pCi/L	0.8× under
24	Prospect	3.1 pCi/L	0.8× under
25	Wolcott	3.1 pCi/L	0.8× under
26	Clinton	3.0 pCi/L	0.8× under
27	West Torrington	3.0 pCi/L	0.8× under
28	North Branford	3.0 pCi/L	0.7× under
29	Central Waterford	2.9 pCi/L	0.7× under
30	East Haven	2.9 pCi/L	0.7× under
31	New Milford	2.9 pCi/L	0.7× under
32	Plainfield	2.9 pCi/L	0.7× under
33	Lake Pocotopaug	2.9 pCi/L	0.7× under
34	Ledyard Center	2.8 pCi/L	0.7× under
35	City of Milford (balance)	2.8 pCi/L	0.7× under
36	Pawcatuck	2.8 pCi/L	0.7× under
37	Ellington	2.7 pCi/L	0.7× under
38	New Preston	2.7 pCi/L	0.7× under
39	Norwich	2.7 pCi/L	0.7× under
40	Oxford	2.6 pCi/L	0.7× under
41	Sherman	2.6 pCi/L	0.7× under
42	Colchester	2.6 pCi/L	0.6× under
43	Kent	2.6 pCi/L	0.6× under
44	Wilton	2.6 pCi/L	0.6× under
45	Cromwell	2.5 pCi/L	0.6× under
46	Southbury	2.5 pCi/L	0.6× under
47	Guilford	2.5 pCi/L	0.6× under
48	Shelton	2.5 pCi/L	0.6× under
49	Farmington	2.5 pCi/L	0.6× under
50	Bethlehem Village	2.4 pCi/L	0.6× under
51	North Haven	2.4 pCi/L	0.6× under
52	Plainfield Village	2.4 pCi/L	0.6× under
53	Waterbury	2.4 pCi/L	0.6× under
54	Middlebury	2.4 pCi/L	0.6× under
55	Torrington	2.3 pCi/L	0.6× under
56	Southport	2.3 pCi/L	0.6× under
57	Winsted	2.3 pCi/L	0.6× under
58	Terryville	2.3 pCi/L	0.6× under
59	Middletown	2.3 pCi/L	0.6× under
60	Tariffville	2.3 pCi/L	0.6× under
61	Byram	2.3 pCi/L	0.6× under
62	Stamford	2.2 pCi/L	0.6× under
63	Moosup	2.2 pCi/L	0.6× under
64	Preston City	2.2 pCi/L	0.6× under
65	Trumbull	2.2 pCi/L	0.6× under
66	Newtown	2.2 pCi/L	0.6× under
67	Oakville	2.2 pCi/L	0.6× under
68	Orange	2.2 pCi/L	0.6× under
69	Niantic	2.2 pCi/L	0.6× under
70	Wallingford	2.2 pCi/L	0.5× under
71	Bridgeport	2.1 pCi/L	0.5× under
72	Stratford	2.1 pCi/L	0.5× under
73	Old Saybrook 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	Westbrook Center	1.9 pCi/L	0.5× under
82	North Stamford	1.9 pCi/L	0.5× under
83	Hamden	1.9 pCi/L	0.5× under
84	Higganum	1.9 pCi/L	0.5× under
85	Collinsville	1.9 pCi/L	0.5× under
86	Kensington	1.9 pCi/L	0.5× under
87	Canaan	1.9 pCi/L	0.5× under
88	Meriden	1.9 pCi/L	0.5× under
89	Willimantic	1.9 pCi/L	0.5× under
90	Fairfield	1.8 pCi/L	0.5× under
91	Greenwich	1.8 pCi/L	0.5× under
92	Darien	1.8 pCi/L	0.5× under
93	Hebron	1.8 pCi/L	0.5× under
94	New Canaan	1.8 pCi/L	0.4× under
95	Canton Valley	1.8 pCi/L	0.4× under
96	Danbury	1.7 pCi/L	0.4× under
97	Watertown	1.7 pCi/L	0.4× under
98	Coventry Lake	1.7 pCi/L	0.4× under
99	Manchester	1.7 pCi/L	0.4× under
100	Groton	1.7 pCi/L	0.4× under
101	Madison	1.6 pCi/L	0.4× under
102	Bristol	1.6 pCi/L	0.4× under
103	Mansfield City	1.6 pCi/L	0.4× under
104	Norwalk	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	Simsbury Center	1.6 pCi/L	0.4× under
108	Plainville	1.6 pCi/L	0.4× under
109	Woodbridge	1.6 pCi/L	0.4× under
110	Storrs	1.5 pCi/L	0.4× under
111	Old Greenwich	1.5 pCi/L	0.4× under
112	Bethel	1.5 pCi/L	0.4× under
113	North Granby	1.5 pCi/L	0.4× under
114	Glastonbury Center	1.5 pCi/L	0.4× under
115	New Haven	1.4 pCi/L	0.4× under
116	Long Hill	1.4 pCi/L	0.3× under
117	Blue Hills	1.4 pCi/L	0.3× under
118	Newington	1.4 pCi/L	0.3× under
119	Suffield Depot	1.4 pCi/L	0.3× under
120	Rockville	1.4 pCi/L	0.3× under
121	Milford	1.4 pCi/L	0.3× under
122	Mystic	1.3 pCi/L	0.3× under
123	Weatogue	1.3 pCi/L	0.3× under
124	Terramuggus	1.3 pCi/L	0.3× under
125	Deep River Center	1.2 pCi/L	0.3× under
126	Salmon Brook	1.2 pCi/L	0.3× under
127	Wallingford Center	1.2 pCi/L	0.3× under
128	New Britain	1.2 pCi/L	0.3× under
129	Essex Village	1.1 pCi/L	0.3× under
130	Poquonock Bridge	1.1 pCi/L	0.3× under
131	West Hartford	1.1 pCi/L	0.3× under
132	East Hartford	1.1 pCi/L	0.3× under
133	Litchfield	1.1 pCi/L	0.3× under
134	Cheshire	1.0 pCi/L	0.3× under
135	Naugatuck	1.0 pCi/L	0.3× under
136	Moodus	1.0 pCi/L	0.3× under
137	Pemberwick	0.9 pCi/L	0.2× under
138	Branford	0.8 pCi/L	0.2× under
139	Glastonbury	0.8 pCi/L	0.2× under
140	West Haven	0.8 pCi/L	0.2× under
141	South Coventry	0.7 pCi/L	0.2× under
142	South Windsor	0.7 pCi/L	0.2× under
143	Hartford	0.6 pCi/L	0.1× under

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