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 September 28, 2026

Highest city

280.1Bq/m³

Dryden

Ontario city average

91.1Bq/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	199.8 Bq/m³	1.0× under
5	Renfrew	192.5 Bq/m³	1.0× under
6	Espanola	186.2 Bq/m³	0.9× under
7	Smiths Falls	185.0 Bq/m³	0.9× under
8	Bancroft	184.2 Bq/m³	0.9× under
9	Neebing	175.7 Bq/m³	0.9× under
10	Wingham	174.2 Bq/m³	0.9× under
11	Perth	166.8 Bq/m³	0.8× under
12	Carleton Place	166.3 Bq/m³	0.8× under
13	Gananoque	164.5 Bq/m³	0.8× under
14	Petrolia	159.6 Bq/m³	0.8× under
15	Prescott	159.4 Bq/m³	0.8× under
16	Rayside-Balfour	155.1 Bq/m³	0.8× under
17	Thunder Bay	149.2 Bq/m³	0.7× under
18	Skatepark	143.4 Bq/m³	0.7× under
19	Amherstburg	140.8 Bq/m³	0.7× under
20	Arnprior	139.9 Bq/m³	0.7× under
21	Owen Sound	139.4 Bq/m³	0.7× under
22	Paris	137.3 Bq/m³	0.7× under
23	Walpole Island	133.4 Bq/m³	0.7× under
24	Napanee Downtown	126.2 Bq/m³	0.6× under
25	Ancaster	118.0 Bq/m³	0.6× under
26	Marathon	117.6 Bq/m³	0.6× under
27	Kingston	116.8 Bq/m³	0.6× under
28	North Perth	115.8 Bq/m³	0.6× under
29	Orangeville	115.4 Bq/m³	0.6× under
30	Greater Sudbury	114.9 Bq/m³	0.6× under
31	South Huron	113.3 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	Goderich	111.1 Bq/m³	0.6× under
35	Deseronto	110.1 Bq/m³	0.6× under
36	Brockville	107.0 Bq/m³	0.5× under
37	Peterborough	106.3 Bq/m³	0.5× under
38	Woodstock	105.2 Bq/m³	0.5× under
39	Huron East	102.6 Bq/m³	0.5× under
40	Clarence-Rockland	102.1 Bq/m³	0.5× under
41	Port Colborne	100.8 Bq/m³	0.5× under
42	Sarnia	100.1 Bq/m³	0.5× under
43	North Bay	98.8 Bq/m³	0.5× under
44	Bells Corners	97.1 Bq/m³	0.5× under
45	Picton	96.6 Bq/m³	0.5× under
46	Casselman	93.7 Bq/m³	0.5× under
47	Temiskaming Shores	93.3 Bq/m³	0.5× under
48	Cambridge	92.9 Bq/m³	0.5× under
49	Omemee	91.7 Bq/m³	0.5× under
50	Delaware	91.6 Bq/m³	0.5× under
51	Elliot Lake	87.3 Bq/m³	0.4× under
52	Windsor	84.6 Bq/m³	0.4× under
53	St. Thomas	83.3 Bq/m³	0.4× under
54	Ingersoll	82.8 Bq/m³	0.4× under
55	Petawawa	82.8 Bq/m³	0.4× under
56	Ottawa	82.5 Bq/m³	0.4× under
57	Hawkesbury	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	80.1 Bq/m³	0.4× under
61	South River	78.5 Bq/m³	0.4× under
62	Hanover	76.0 Bq/m³	0.4× under
63	Stratford	75.8 Bq/m³	0.4× under
64	Milton	75.6 Bq/m³	0.4× under
65	Norfolk County	75.2 Bq/m³	0.4× under
66	Innisfil	72.8 Bq/m³	0.4× under
67	Bourget	72.1 Bq/m³	0.4× under
68	Aylmer	71.8 Bq/m³	0.4× under
69	Iroquois Falls	70.8 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	69.7 Bq/m³	0.3× under
73	Quinte West	68.6 Bq/m³	0.3× under
74	Cornwall	67.6 Bq/m³	0.3× under
75	Sault Ste. Marie	67.2 Bq/m³	0.3× under
76	London	66.2 Bq/m³	0.3× under
77	Brantford	65.5 Bq/m³	0.3× under
78	Powassan	65.5 Bq/m³	0.3× under
79	Lambton Shores	65.3 Bq/m³	0.3× under
80	Gravenhurst	65.2 Bq/m³	0.3× under
81	Camlachie	65.1 Bq/m³	0.3× under
82	Uxbridge	62.7 Bq/m³	0.3× under
83	Thessalon	62.6 Bq/m³	0.3× under
84	Bracebridge	62.3 Bq/m³	0.3× under
85	Bluewater	62.0 Bq/m³	0.3× under
86	Welland	61.4 Bq/m³	0.3× under
87	Waterloo	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	56.3 Bq/m³	0.3× under
91	Midland	56.2 Bq/m³	0.3× under
92	Thorold	55.0 Bq/m³	0.3× under
93	Willowdale	53.7 Bq/m³	0.3× under
94	Huntsville	53.6 Bq/m³	0.3× under
95	St. Catharines	52.8 Bq/m³	0.3× under
96	Oakville	52.0 Bq/m³	0.3× under
97	Orillia	50.8 Bq/m³	0.3× under
98	Etobicoke	49.1 Bq/m³	0.2× under
99	North York	48.6 Bq/m³	0.2× under
100	Niagara Falls	47.7 Bq/m³	0.2× under
101	Collingwood	47.6 Bq/m³	0.2× under
102	Cobourg	47.2 Bq/m³	0.2× under
103	Kirkland Lake	46.7 Bq/m³	0.2× under
104	Barrie	46.3 Bq/m³	0.2× under
105	Scarborough	45.8 Bq/m³	0.2× under
106	Mississauga	44.5 Bq/m³	0.2× under
107	Brampton	42.4 Bq/m³	0.2× under
108	Concord	42.0 Bq/m³	0.2× under
109	Ajax	40.9 Bq/m³	0.2× under
110	Bradford West Gwillimbury	40.3 Bq/m³	0.2× under
111	Wasaga Beach	39.9 Bq/m³	0.2× under
112	Oshawa	38.3 Bq/m³	0.2× under
113	Deep River	38.0 Bq/m³	0.2× under
114	Newmarket	36.0 Bq/m³	0.2× under
115	Markham	33.8 Bq/m³	0.2× under
116	Hearst	33.3 Bq/m³	0.2× under
117	Toronto	33.1 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	28.8 Bq/m³	0.1× under
121	Pickering	28.2 Bq/m³	0.1× under
122	Parry Sound	27.1 Bq/m³	0.1× under

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