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 August 30, 2026
Highest city
280.1Bq/m³
Dryden
Ontario city average
91.1Bq/m³
across 122 cities
Above action level
4/ 122
cities
| # | 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 |
| 4 | Dorchester | 204.7 Bq/m³ | 1.0× over |
| ✓ Below EPA action level (200 Bq/m³) | |||
| 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 | Neebing | 184.1 Bq/m³ | 0.9× under |
| 9 | Bancroft | 183.5 Bq/m³ | 0.9× under |
| 10 | Wingham | 174.2 Bq/m³ | 0.9× under |
| 11 | Perth | 171.2 Bq/m³ | 0.9× under |
| 12 | Gananoque | 166.3 Bq/m³ | 0.8× under |
| 13 | Carleton Place | 165.3 Bq/m³ | 0.8× under |
| 14 | Petrolia | 160.5 Bq/m³ | 0.8× under |
| 15 | Prescott | 158.5 Bq/m³ | 0.8× under |
| 16 | Rayside-Balfour | 155.1 Bq/m³ | 0.8× under |
| 17 | Thunder Bay | 149.9 Bq/m³ | 0.7× under |
| 18 | Skatepark | 144.2 Bq/m³ | 0.7× under |
| 19 | Owen Sound | 140.8 Bq/m³ | 0.7× under |
| 20 | Paris | 140.1 Bq/m³ | 0.7× under |
| 21 | Arnprior | 139.6 Bq/m³ | 0.7× under |
| 22 | Amherstburg | 138.5 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 | Kingston | 117.7 Bq/m³ | 0.6× under |
| 26 | Marathon | 117.6 Bq/m³ | 0.6× under |
| 27 | Ancaster | 117.5 Bq/m³ | 0.6× under |
| 28 | Orangeville | 116.1 Bq/m³ | 0.6× under |
| 29 | North Perth | 114.6 Bq/m³ | 0.6× under |
| 30 | Greater Sudbury | 113.4 Bq/m³ | 0.6× under |
| 31 | South Huron | 113.3 Bq/m³ | 0.6× under |
| 32 | Belleville | 113.0 Bq/m³ | 0.6× under |
| 33 | Prince Edward | 113.0 Bq/m³ | 0.6× under |
| 34 | Goderich | 112.0 Bq/m³ | 0.6× under |
| 35 | Deseronto | 110.1 Bq/m³ | 0.6× under |
| 36 | Peterborough | 106.7 Bq/m³ | 0.5× under |
| 37 | Brockville | 105.8 Bq/m³ | 0.5× under |
| 38 | Woodstock | 105.4 Bq/m³ | 0.5× under |
| 39 | Huron East | 101.9 Bq/m³ | 0.5× under |
| 40 | Clarence-Rockland | 100.6 Bq/m³ | 0.5× under |
| 41 | North Bay | 100.6 Bq/m³ | 0.5× under |
| 42 | Sarnia | 100.1 Bq/m³ | 0.5× under |
| 43 | Picton | 97.8 Bq/m³ | 0.5× under |
| 44 | Port Colborne | 97.7 Bq/m³ | 0.5× under |
| 45 | Bells Corners | 97.4 Bq/m³ | 0.5× under |
| 46 | Casselman | 93.7 Bq/m³ | 0.5× under |
| 47 | Cambridge | 93.6 Bq/m³ | 0.5× under |
| 48 | Temiskaming Shores | 93.3 Bq/m³ | 0.5× under |
| 49 | Omemee | 92.2 Bq/m³ | 0.5× under |
| 50 | Delaware | 92.1 Bq/m³ | 0.5× under |
| 51 | Elliot Lake | 92.1 Bq/m³ | 0.5× under |
| 52 | St. Thomas | 83.9 Bq/m³ | 0.4× under |
| 53 | Ingersoll | 83.5 Bq/m³ | 0.4× under |
| 54 | Hawkesbury | 83.0 Bq/m³ | 0.4× under |
| 55 | Windsor | 83.0 Bq/m³ | 0.4× under |
| 56 | Ottawa | 82.8 Bq/m³ | 0.4× under |
| 57 | Guelph | 82.3 Bq/m³ | 0.4× under |
| 58 | Pembroke | 82.1 Bq/m³ | 0.4× under |
| 59 | Shelburne | 79.3 Bq/m³ | 0.4× under |
| 60 | South River | 78.5 Bq/m³ | 0.4× under |
| 61 | Hanover | 76.3 Bq/m³ | 0.4× under |
| 62 | Stratford | 75.7 Bq/m³ | 0.4× under |
| 63 | Norfolk County | 75.2 Bq/m³ | 0.4× under |
| 64 | Milton | 74.8 Bq/m³ | 0.4× under |
| 65 | Innisfil | 73.4 Bq/m³ | 0.4× under |
| 66 | Aylmer | 72.8 Bq/m³ | 0.4× under |
| 67 | Bourget | 72.8 Bq/m³ | 0.4× under |
| 68 | Petawawa | 71.2 Bq/m³ | 0.4× under |
| 69 | Fort Erie | 70.7 Bq/m³ | 0.4× under |
| 70 | Hamilton | 70.1 Bq/m³ | 0.4× under |
| 71 | Burlington | 69.4 Bq/m³ | 0.3× under |
| 72 | Quinte West | 68.9 Bq/m³ | 0.3× under |
| 73 | Lambton Shores | 67.7 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 | Iroquois Falls | 66.6 Bq/m³ | 0.3× under |
| 77 | London | 66.1 Bq/m³ | 0.3× under |
| 78 | Powassan | 65.5 Bq/m³ | 0.3× under |
| 79 | Brantford | 65.2 Bq/m³ | 0.3× under |
| 80 | Camlachie | 65.1 Bq/m³ | 0.3× under |
| 81 | Gravenhurst | 64.7 Bq/m³ | 0.3× under |
| 82 | Bracebridge | 63.7 Bq/m³ | 0.3× under |
| 83 | Uxbridge | 62.7 Bq/m³ | 0.3× under |
| 84 | Thessalon | 62.6 Bq/m³ | 0.3× under |
| 85 | Bluewater | 62.0 Bq/m³ | 0.3× under |
| 86 | Waterloo | 61.1 Bq/m³ | 0.3× under |
| 87 | Welland | 60.4 Bq/m³ | 0.3× under |
| 88 | Timmins | 59.4 Bq/m³ | 0.3× under |
| 89 | Angus | 57.5 Bq/m³ | 0.3× under |
| 90 | Midland | 57.3 Bq/m³ | 0.3× under |
| 91 | Kitchener | 55.9 Bq/m³ | 0.3× under |
| 92 | Thorold | 55.4 Bq/m³ | 0.3× under |
| 93 | Huntsville | 54.2 Bq/m³ | 0.3× under |
| 94 | Willowdale | 53.8 Bq/m³ | 0.3× under |
| 95 | Oakville | 51.8 Bq/m³ | 0.3× under |
| 96 | St. Catharines | 51.8 Bq/m³ | 0.3× under |
| 97 | Orillia | 51.0 Bq/m³ | 0.3× under |
| 98 | Etobicoke | 49.1 Bq/m³ | 0.2× under |
| 99 | North York | 48.3 Bq/m³ | 0.2× under |
| 100 | Collingwood | 48.2 Bq/m³ | 0.2× under |
| 101 | Niagara Falls | 48.0 Bq/m³ | 0.2× under |
| 102 | Kirkland Lake | 46.7 Bq/m³ | 0.2× under |
| 103 | Cobourg | 46.4 Bq/m³ | 0.2× under |
| 104 | Barrie | 45.8 Bq/m³ | 0.2× under |
| 105 | Scarborough | 45.5 Bq/m³ | 0.2× under |
| 106 | Mississauga | 44.4 Bq/m³ | 0.2× under |
| 107 | Brampton | 42.4 Bq/m³ | 0.2× under |
| 108 | Concord | 42.1 Bq/m³ | 0.2× under |
| 109 | Ajax | 40.9 Bq/m³ | 0.2× under |
| 110 | Bradford West Gwillimbury | 39.9 Bq/m³ | 0.2× under |
| 111 | Wasaga Beach | 39.6 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 | 33.6 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 | 31.9 Bq/m³ | 0.2× under |
| 120 | Keswick | 28.8 Bq/m³ | 0.1× under |
| 121 | Pickering | 28.4 Bq/m³ | 0.1× under |
| 122 | Parry Sound | 23.8 Bq/m³ | 0.1× under |