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 121 cities.

Updated August 16, 2026

Highest city

280.1Bq/m³

Dryden

Ontario city average

91.7Bq/m³

across 121 cities

Above action level

4/ 121

cities

Ontario Cities Ranked by Indoor Radon Levels
#	Location	Avg level	Monitors	vs action level
1	Dryden	280.1 Bq/m³	24	1.4× over
2	Brant	255.5 Bq/m³	14	1.3× over
3	Atikokan	241.4 Bq/m³	9	1.2× over
4	Dorchester	204.7 Bq/m³	33	1.0× over
✓ Below EPA action level (200 Bq/m³)
5	Renfrew	192.5 Bq/m³	39	1.0× under
6	Espanola	186.2 Bq/m³	7	0.9× under
7	Smiths Falls	185.0 Bq/m³	74	0.9× under
8	Neebing	184.1 Bq/m³	8	0.9× under
9	Bancroft	183.5 Bq/m³	89	0.9× under
10	Wingham	174.2 Bq/m³	36	0.9× under
11	Perth	171.2 Bq/m³	121	0.9× under
12	Gananoque	166.3 Bq/m³	39	0.8× under
13	Carleton Place	165.7 Bq/m³	261	0.8× under
14	Petrolia	160.5 Bq/m³	33	0.8× under
15	Prescott	159.6 Bq/m³	83	0.8× under
16	Rayside-Balfour	155.1 Bq/m³	25	0.8× under
17	Thunder Bay	149.9 Bq/m³	141	0.7× under
18	Skatepark	144.2 Bq/m³	39	0.7× under
19	Owen Sound	141.5 Bq/m³	120	0.7× under
20	Arnprior	141.2 Bq/m³	87	0.7× under
21	Paris	140.1 Bq/m³	56	0.7× under
22	Amherstburg	138.5 Bq/m³	85	0.7× under
23	Walpole Island	131.4 Bq/m³	88	0.7× under
24	Napanee Downtown	126.2 Bq/m³	12	0.6× under
25	Kingston	118.0 Bq/m³	369	0.6× under
26	Ancaster	117.7 Bq/m³	327	0.6× under
27	Marathon	117.6 Bq/m³	10	0.6× under
28	Orangeville	116.1 Bq/m³	113	0.6× under
29	North Perth	114.6 Bq/m³	41	0.6× under
30	Greater Sudbury	113.4 Bq/m³	164	0.6× under
31	South Huron	113.3 Bq/m³	19	0.6× under
32	Belleville	113.0 Bq/m³	104	0.6× under
33	Prince Edward	113.0 Bq/m³	16	0.6× under
34	Goderich	112.0 Bq/m³	43	0.6× under
35	Deseronto	110.1 Bq/m³	13	0.6× under
36	Peterborough	107.2 Bq/m³	154	0.5× under
37	Brockville	105.8 Bq/m³	51	0.5× under
38	Woodstock	105.4 Bq/m³	76	0.5× under
39	Huron East	101.9 Bq/m³	30	0.5× under
40	North Bay	101.2 Bq/m³	74	0.5× under
41	Clarence-Rockland	100.6 Bq/m³	254	0.5× under
42	Sarnia	100.1 Bq/m³	58	0.5× under
43	Picton	97.8 Bq/m³	34	0.5× under
44	Port Colborne	97.7 Bq/m³	22	0.5× under
45	Bells Corners	97.4 Bq/m³	1956	0.5× under
46	Casselman	93.7 Bq/m³	69	0.5× under
47	Cambridge	93.6 Bq/m³	172	0.5× under
48	Temiskaming Shores	93.3 Bq/m³	7	0.5× under
49	Omemee	93.0 Bq/m³	104	0.5× under
50	Delaware	92.1 Bq/m³	98	0.5× under
51	Elliot Lake	92.1 Bq/m³	13	0.5× under
52	St. Thomas	83.9 Bq/m³	80	0.4× under
53	Windsor	83.7 Bq/m³	110	0.4× under
54	Ingersoll	83.5 Bq/m³	49	0.4× under
55	Hawkesbury	83.0 Bq/m³	42	0.4× under
56	Ottawa	82.9 Bq/m³	1949	0.4× under
57	Guelph	82.2 Bq/m³	358	0.4× under
58	Pembroke	82.1 Bq/m³	24	0.4× under
59	Shelburne	79.3 Bq/m³	34	0.4× under
60	South River	78.5 Bq/m³	14	0.4× under
61	Petawawa	76.6 Bq/m³	11	0.4× under
62	Stratford	75.7 Bq/m³	94	0.4× under
63	Norfolk County	75.2 Bq/m³	64	0.4× under
64	Milton	74.8 Bq/m³	324	0.4× under
65	Hanover	73.7 Bq/m³	73	0.4× under
66	Innisfil	73.4 Bq/m³	51	0.4× under
67	Aylmer	72.8 Bq/m³	22	0.4× under
68	Bourget	72.8 Bq/m³	44	0.4× under
69	Fort Erie	70.7 Bq/m³	29	0.4× under
70	Hamilton	70.1 Bq/m³	523	0.4× under
71	Burlington	69.4 Bq/m³	487	0.3× under
72	Quinte West	68.9 Bq/m³	97	0.3× under
73	Lambton Shores	67.7 Bq/m³	23	0.3× under
74	Cornwall	67.6 Bq/m³	71	0.3× under
75	Sault Ste. Marie	67.2 Bq/m³	48	0.3× under
76	Iroquois Falls	66.6 Bq/m³	9	0.3× under
77	London	66.1 Bq/m³	470	0.3× under
78	Powassan	65.5 Bq/m³	11	0.3× under
79	Brantford	65.2 Bq/m³	125	0.3× under
80	Camlachie	65.1 Bq/m³	25	0.3× under
81	Gravenhurst	64.7 Bq/m³	26	0.3× under
82	Bracebridge	63.7 Bq/m³	48	0.3× under
83	Uxbridge	62.9 Bq/m³	99	0.3× under
84	Thessalon	62.6 Bq/m³	7	0.3× under
85	Bluewater	62.0 Bq/m³	24	0.3× under
86	Waterloo	61.0 Bq/m³	755	0.3× under
87	Welland	60.4 Bq/m³	98	0.3× under
88	Timmins	59.4 Bq/m³	18	0.3× under
89	Angus	57.5 Bq/m³	41	0.3× under
90	Midland	57.3 Bq/m³	48	0.3× under
91	Kitchener	55.9 Bq/m³	253	0.3× under
92	Thorold	55.4 Bq/m³	33	0.3× under
93	Huntsville	54.2 Bq/m³	53	0.3× under
94	Willowdale	53.6 Bq/m³	474	0.3× under
95	Oakville	51.9 Bq/m³	678	0.3× under
96	St. Catharines	51.8 Bq/m³	204	0.3× under
97	Orillia	51.0 Bq/m³	79	0.3× under
98	Etobicoke	49.1 Bq/m³	540	0.2× under
99	Collingwood	48.6 Bq/m³	99	0.2× under
100	North York	48.3 Bq/m³	253	0.2× under
101	Niagara Falls	48.0 Bq/m³	61	0.2× under
102	Kirkland Lake	46.7 Bq/m³	9	0.2× under
103	Cobourg	46.4 Bq/m³	58	0.2× under
104	Barrie	45.8 Bq/m³	185	0.2× under
105	Scarborough	45.5 Bq/m³	529	0.2× under
106	Mississauga	44.4 Bq/m³	751	0.2× under
107	Brampton	42.4 Bq/m³	427	0.2× under
108	Concord	42.1 Bq/m³	120	0.2× under
109	Ajax	40.8 Bq/m³	255	0.2× under
110	Bradford West Gwillimbury	39.9 Bq/m³	95	0.2× under
111	Wasaga Beach	39.6 Bq/m³	41	0.2× under
112	Oshawa	38.4 Bq/m³	366	0.2× under
113	Deep River	38.0 Bq/m³	9	0.2× under
114	Newmarket	36.0 Bq/m³	412	0.2× under
115	Markham	33.6 Bq/m³	812	0.2× under
116	Toronto	33.1 Bq/m³	1915	0.2× under
117	Vaughan	32.5 Bq/m³	417	0.2× under
118	Richmond Hill	31.9 Bq/m³	721	0.2× under
119	Keswick	28.8 Bq/m³	71	0.1× under
120	Pickering	28.4 Bq/m³	91	0.1× under
121	Parry Sound	23.8 Bq/m³	24	0.1× under

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