Canada Radon publishes community-level indoor radon context from Health Canada's Cross-Canada Survey of Radon Concentrations in Homes and related open releases. Named datasets and licence links are on data sources. Testing and mitigation practice are covered under how to test and mitigation.

Coverage

The atlas tracks 117 municipalities. Of those, 34 carry a direct survey geography match and 83 use a regional or provincial proxy until a finer breakout is available. Data tiers appear on every city page.

What the survey measures

Participating homes deploy long-term alpha-track (or equivalent) detectors, typically three months or longer, preferably including heating season. Health Canada and partners aggregate results by available geography and publish open summaries (means, shares at or above 200 Bq/m³). Survey means describe tested homes in a geography. They are not a census of every dwelling and not a reading for any single address.

Guideline framing

Health Canada's indoor radon guideline is 200 Bq/m³ in the normal occupancy area. Remedial measures are recommended within a reasonable time frame at 200–600 Bq/m³, and within about one year above 600 Bq/m³. Risk rises with concentration and with time; there is no known threshold of zero risk below 200 Bq/m³. Smoking multiplies lung-cancer risk at a given concentration; averages do not encode smoking status.

Data tiers

• Direct. Mean and percent-above-guideline come from a survey geography matched to that municipality or its named metro breakout.
• Regional. The nearest broader survey geography is shown and labeled. Treat these pages as regional potential indicators, not house-level evidence.

Cadence

The Cross-Canada Survey is not an annual municipal retest calendar. Pages do not invent yearly Bq/m³ series. Where multi-year rankings carry a survey vintage forward for continuity, notes flag that the underlying survey did not re-sample that year. Short-term tests (days) remain screening tools, common in real estate; confirm with long-term results.

Professionals and standards

Measurement and mitigation professionals are certified through the Canadian National Radon Proficiency Program (C-NRPP). Canadian General Standards Board (CGSB) standards cover radon control in new construction and mitigation practice. Hire C-NRPP professionals for elevated results and retest after mitigation.

Using a city page

Treat the city mean and percent-above-guideline as a reason to test, not as a substitute for a reading in your home. Note the data tier, compare lightly with the provincial figure, then place a long-term detector on the lowest lived-in level through heating season. If results are elevated, hire a C-NRPP professional and retest after mitigation.

Limitations

A low city average does not guarantee a low home; a high average does not guarantee every home is elevated. Geology and building stock both matter; house-to-house variation often exceeds city-to-city average gaps. For decisions about your property, run a long-term test on the lowest lived-in level. Primer: Indoor Radon in Canada.