Ontario Cities Ranked by Indoor Radon Levels

Measured averages from Airthings devices across Ontario, Canada. Action level: 200 Bq/m³ — the threshold at which remediation is recommended.

Dryden has the highest measured indoor radon in Ontario at 280.1 Bq/m³, based on Airthings measurements across 122 cities.

Updated October 19, 2026

Highest city

280.1Bq/m³

Dryden

Ontario city average

91.2Bq/m³

across 122 cities

Above action level

3/ 122

cities

Ontario Cities Ranked by Indoor Radon Levels
#	Location	Avg level	vs action level
1	Dryden	280.1 Bq/m³	1.4× over
2	Brant	255.5 Bq/m³	1.3× over
3	Atikokan	241.4 Bq/m³	1.2× over
✓ Below EPA action level (200 Bq/m³)
4	Dorchester	197.3 Bq/m³	1.0× under
5	Renfrew	188.6 Bq/m³	0.9× under
6	Espanola	186.2 Bq/m³	0.9× under
7	Smiths Falls	185.4 Bq/m³	0.9× under
8	Bancroft	182.2 Bq/m³	0.9× under
9	Neebing	175.7 Bq/m³	0.9× under
10	Wingham	174.2 Bq/m³	0.9× under
11	Carleton Place	166.3 Bq/m³	0.8× under
12	Gananoque	164.6 Bq/m³	0.8× under
13	Perth	162.9 Bq/m³	0.8× under
14	Prescott	161.4 Bq/m³	0.8× under
15	Petrolia	159.9 Bq/m³	0.8× under
16	Thunder Bay	147.3 Bq/m³	0.7× under
17	Skatepark	143.4 Bq/m³	0.7× under
18	Amherstburg	142.7 Bq/m³	0.7× under
19	Arnprior	139.0 Bq/m³	0.7× under
20	Owen Sound	137.6 Bq/m³	0.7× under
21	Rayside-Balfour	136.2 Bq/m³	0.7× under
22	Paris	134.3 Bq/m³	0.7× under
23	Walpole Island	131.9 Bq/m³	0.7× under
24	Napanee Downtown	126.2 Bq/m³	0.6× under
25	Ancaster	118.3 Bq/m³	0.6× under
26	Marathon	117.6 Bq/m³	0.6× under
27	Kingston	117.5 Bq/m³	0.6× under
28	North Perth	115.8 Bq/m³	0.6× under
29	Orangeville	115.5 Bq/m³	0.6× under
30	Greater Sudbury	114.7 Bq/m³	0.6× under
31	South Huron	113.8 Bq/m³	0.6× under
32	Prince Edward	113.0 Bq/m³	0.6× under
33	Belleville	112.2 Bq/m³	0.6× under
34	Brockville	110.9 Bq/m³	0.6× under
35	Deseronto	110.1 Bq/m³	0.6× under
36	Goderich	107.7 Bq/m³	0.5× under
37	Peterborough	106.4 Bq/m³	0.5× under
38	Port Colborne	104.6 Bq/m³	0.5× under
39	Woodstock	104.5 Bq/m³	0.5× under
40	Huron East	102.5 Bq/m³	0.5× under
41	Clarence-Rockland	100.8 Bq/m³	0.5× under
42	Sarnia	100.1 Bq/m³	0.5× under
43	North Bay	97.3 Bq/m³	0.5× under
44	Bells Corners	97.1 Bq/m³	0.5× under
45	Elliot Lake	96.6 Bq/m³	0.5× under
46	Picton	96.6 Bq/m³	0.5× under
47	Casselman	93.7 Bq/m³	0.5× under
48	Petawawa	93.5 Bq/m³	0.5× under
49	Cambridge	93.4 Bq/m³	0.5× under
50	Temiskaming Shores	93.3 Bq/m³	0.5× under
51	Omemee	91.5 Bq/m³	0.5× under
52	Delaware	91.4 Bq/m³	0.5× under
53	Windsor	87.1 Bq/m³	0.4× under
54	Hawkesbury	85.7 Bq/m³	0.4× under
55	Ingersoll	82.7 Bq/m³	0.4× under
56	Ottawa	82.6 Bq/m³	0.4× under
57	St. Thomas	82.2 Bq/m³	0.4× under
58	Guelph	82.1 Bq/m³	0.4× under
59	Pembroke	82.1 Bq/m³	0.4× under
60	Shelburne	81.4 Bq/m³	0.4× under
61	Iroquois Falls	79.5 Bq/m³	0.4× under
62	South River	78.5 Bq/m³	0.4× under
63	Stratford	76.5 Bq/m³	0.4× under
64	Hanover	76.3 Bq/m³	0.4× under
65	Milton	75.5 Bq/m³	0.4× under
66	Norfolk County	75.2 Bq/m³	0.4× under
67	Innisfil	72.3 Bq/m³	0.4× under
68	Bourget	72.1 Bq/m³	0.4× under
69	Aylmer	71.8 Bq/m³	0.4× under
70	Fort Erie	70.7 Bq/m³	0.4× under
71	Hamilton	70.0 Bq/m³	0.3× under
72	Burlington	69.4 Bq/m³	0.3× under
73	Quinte West	68.1 Bq/m³	0.3× under
74	London	67.4 Bq/m³	0.3× under
75	Cornwall	67.2 Bq/m³	0.3× under
76	Sault Ste. Marie	67.2 Bq/m³	0.3× under
77	Powassan	65.5 Bq/m³	0.3× under
78	Brantford	65.4 Bq/m³	0.3× under
79	Gravenhurst	65.2 Bq/m³	0.3× under
80	Lambton Shores	65.2 Bq/m³	0.3× under
81	Camlachie	65.1 Bq/m³	0.3× under
82	Welland	62.8 Bq/m³	0.3× under
83	Uxbridge	62.3 Bq/m³	0.3× under
84	Bluewater	62.0 Bq/m³	0.3× under
85	Bracebridge	61.8 Bq/m³	0.3× under
86	Waterloo	61.7 Bq/m³	0.3× under
87	Thessalon	61.3 Bq/m³	0.3× under
88	Timmins	59.4 Bq/m³	0.3× under
89	Angus	57.3 Bq/m³	0.3× under
90	Kitchener	56.2 Bq/m³	0.3× under
91	Midland	56.1 Bq/m³	0.3× under
92	Thorold	55.0 Bq/m³	0.3× under
93	Huntsville	54.3 Bq/m³	0.3× under
94	Willowdale	54.1 Bq/m³	0.3× under
95	St. Catharines	53.1 Bq/m³	0.3× under
96	Oakville	51.8 Bq/m³	0.3× under
97	Orillia	50.8 Bq/m³	0.3× under
98	Niagara Falls	49.4 Bq/m³	0.2× under
99	Deep River	49.1 Bq/m³	0.2× under
100	Etobicoke	48.7 Bq/m³	0.2× under
101	North York	48.7 Bq/m³	0.2× under
102	Collingwood	47.9 Bq/m³	0.2× under
103	Cobourg	47.2 Bq/m³	0.2× under
104	Barrie	46.7 Bq/m³	0.2× under
105	Kirkland Lake	46.7 Bq/m³	0.2× under
106	Scarborough	45.5 Bq/m³	0.2× under
107	Mississauga	44.6 Bq/m³	0.2× under
108	Brampton	42.3 Bq/m³	0.2× under
109	Concord	41.7 Bq/m³	0.2× under
110	Ajax	40.8 Bq/m³	0.2× under
111	Bradford West Gwillimbury	40.8 Bq/m³	0.2× under
112	Wasaga Beach	39.9 Bq/m³	0.2× under
113	Oshawa	39.2 Bq/m³	0.2× under
114	Newmarket	35.9 Bq/m³	0.2× under
115	Markham	34.5 Bq/m³	0.2× under
116	Hearst	33.3 Bq/m³	0.2× under
117	Toronto	33.2 Bq/m³	0.2× under
118	Vaughan	32.5 Bq/m³	0.2× under
119	Richmond Hill	32.0 Bq/m³	0.2× under
120	Keswick	28.5 Bq/m³	0.1× under
121	Pickering	28.2 Bq/m³	0.1× under
122	Parry Sound	27.0 Bq/m³	0.1× under

See Canada cities ranked by radon level See all Provinces ranked by radon level