Radon in Mississauga (2026): What the Data Shows, Older Neighbourhood Risk, and What Mississauga Homeowners Should Do

Flat-vector map of Canada with a coral red pin marking Mississauga, Ontario, alongside a circular badge showing 8% — Ontario's provincial share of homes above the Health Canada radon guideline

A note before you read. This article is general health and home-testing information for Mississauga homeowners, drawn from Health Canada, Peel Public Health, Cancer Care Ontario, Tarion, and the Canadian Cancer Society. It is not medical advice. See full disclaimers at the bottom.

If you live in Mississauga and you've been told radon isn't a big deal in the GTA, that's mostly true — but it's not the whole story. Mississauga and the Peel Region sit in a generally lower-radon part of Ontario: the provincial average from Health Canada's 2012 Cross-Canada Survey was about 8% of Ontario homes above the 200 Bq/m³ guideline, and the broader GTA tends to test below the provincial average due to the underlying St. Lawrence Lowlands sedimentary geology.

But: older Mississauga neighbourhoods carry higher risk than the city average suggests. Areas with predominantly 1950s–1970s housing — including Port Credit, Lakeview, Mineola, Lorne Park, and Clarkson — tend to feature older stone or block foundations and basements built before modern vapour barriers, both of which can produce meaningfully higher residential radon than newer construction. Combined with Mississauga's substantial population (~720,000 — Canada's seventh-largest city), even a "lower than average" rate translates to a meaningful number of homes worth testing.

This guide walks through the Mississauga and Peel Region data honestly, explains why some Mississauga neighbourhoods carry higher risk despite the lower regional average, and lays out the practical step-by-step from "I want to know" to "result in hand."

TL;DR for Mississauga homeowners

  • Ontario provincial average: about 8% of homes above the 200 Bq/m³ guideline (Health Canada 2012 Cross-Canada Survey).
  • Mississauga and the Peel Region tend to be lower-radon than the Ontario average due to St. Lawrence Lowlands sedimentary geology.
  • But older Mississauga neighbourhoods — Port Credit, Lakeview, Mineola, Lorne Park, Clarkson — built mostly 1950s–1970s with stone/block foundations and pre-modern vapour barriers can carry higher than average radon risk.
  • The only way to know your specific home's level is to test it. Long-term test, 91+ days, ideally during the heating season. Order a $89 long-term radon test kit →
  • For new-build Mississauga homeowners (Agreement of Purchase and Sale signed on or after February 1, 2021, and within the 7-year window), elevated radon may trigger up to $50,000 of Tarion warranty coverage for mitigation.

Table of contents

  1. What the published Mississauga/Peel radon data actually shows
  2. Why older Mississauga neighbourhoods carry higher risk
  3. Why Mississauga's average is lower than other Canadian cities
  4. What to do as a Mississauga homeowner
  5. Tarion warranty coverage for Mississauga new-build owners
  6. Local Mississauga and Peel resources
  7. FAQ — Mississauga-specific questions
  8. Disclaimers
  9. Sources

What the published Mississauga/Peel radon data actually shows

Mississauga-specific city-level radon survey data is more limited than for some other Canadian cities, but the broader Peel Region and Ontario context is documented:

  • Ontario provincial average (2012 Cross-Canada Survey): about 8% of homes above the 200 Bq/m³ guideline (Health Canada).
  • More recent Ontario testing has found about 25% of homes above the WHO recommendation of 100 Bq/m³, with about 8% above the Health Canada 200 Bq/m³ guideline.
  • Peel Public Health maintains a dedicated radon resource page recognizing radon as an important indoor air quality concern.
  • Mississauga / GTA tend to test on the lower end of the Ontario radon spectrum due to underlying St. Lawrence Lowlands sedimentary geology — similar dynamics to Toronto.

The takeaway: Mississauga's average is on the lower end by Ontario standards — but Mississauga's substantial population (~720,000) means even a single-digit-percentage rate translates to tens of thousands of homes potentially affected. And as the next section explains, older Mississauga neighbourhoods carry higher than average risk.

Order a $89 long-term radon test kit →

Why older Mississauga neighbourhoods carry higher risk

Mississauga's housing stock spans roughly 75 years, from 1950s post-war development through the major suburban expansions of the 1980s–2000s and into ongoing new construction. Older Mississauga neighbourhoods carry higher radon risk than the city average suggests, for specific construction reasons:

Pre-modern foundation construction. Mississauga neighbourhoods developed predominantly in the 1950s–1970s — including Port Credit, Lakeview, Mineola, Lorne Park, and Clarkson — often feature stone or block foundations rather than modern poured-concrete slab construction. Older block foundations have more potential entry points for soil gas (joints between blocks, gaps around service penetrations, less-controlled foundation-to-soil interface) than monolithic poured-concrete construction.

Pre-modern vapour barriers. Newer Canadian residential construction typically includes a 6-mil polyethylene soil gas barrier under the basement slab and around the foundation. Pre-1980s construction often lacks this barrier entirely. Without a soil gas barrier, radon and other soil gases can move more freely from the surrounding soil into basement living areas.

Finished basements added later. Many older Mississauga homes have had basements finished as living space — bedrooms, rec rooms, home offices, in-law suites — without the foundation being upgraded for radon control at the same time. This means occupants spend more hours in the highest-radon part of the home than they would in unfinished-basement scenarios.

For owners of older Mississauga homes — especially in the lakeside neighbourhoods listed above, the older parts of Streetsville, and similar mid-century-built areas — the case for testing is stronger than the Peel Region average suggests.

Order your $89 long-term radon test kit →

Why Mississauga's average is lower than other Canadian cities

Geology is the main reason Mississauga's average is lower than prairie or Atlantic Canadian cities:

Geology. Mississauga sits on the St. Lawrence Lowlands sedimentary basin, on glacial soils derived from Ordovician shale and limestone bedrock. This geology contains lower uranium concentrations than the Canadian Shield bedrock under prairie cities or the Halifax Group bedrock under Halifax. Less uranium in the soil = less natural radon production = lower background residential radon levels.

Climate and construction. Mississauga has a typical Southern Ontario heating season (October–April) — similar to other Ontario cities. But the geology is doing most of the work in producing the lower-than-average rate.

That said, individual Mississauga homes can still test high depending on foundation, ventilation, basement use, small-scale geological variations, and the age-related factors described in the previous section.

What to do as a Mississauga homeowner

Step-by-step:

Step 1: Test (long-term, 91+ days). Health Canada's recommended test for a homeowner mitigation decision is a long-term alpha-track lab test, deployed for at least 91 days during the heating season (October–April in Mississauga), in the lowest lived-in level of your home. The test costs $89 all-in with RadonTest.ca — kit, tracked outbound, prepaid tracked Canada Post return label, and analysis at Lex Scientific in Guelph, Ontario (a C-NRPP-listed Canadian lab).

Step 2: Read your result. Below 200 Bq/m³, no mitigation is required (Health Canada recommends retesting every 5 years). Above 200 Bq/m³, mitigation is recommended. See our How to Read Your Radon Test Results and What to Do If Your Radon Level Is Above 200 Bq/m³ guides.

Step 3: Mitigate, if needed. A C-NRPP-certified mitigation contractor installs a sub-slab depressurization system at a typical Ontario cost of $2,500–$4,500. These systems typically reduce radon by up to 95% (Health Canada cites reductions of more than 80%; CARST cites up to 95%). Find a Mississauga-area C-NRPP-certified mitigator via the C-NRPP Find a Professional tool.

Step 4: Apply for Tarion warranty coverage (if applicable) AND/OR the Lungs Matter grant. See the Tarion section below. The Lungs Matter program offers up to $1,500 for eligible Canadians.

Step 5: Verify. Once mitigation is complete, run an independent post-mitigation test to confirm levels are below 200 Bq/m³.

Order your Mississauga kit — $89 →

Tarion warranty coverage for Mississauga new-build owners

If you bought a new home in Mississauga with an Agreement of Purchase and Sale signed on or after February 1, 2021, and the home is within its 7-year warranty window, Tarion covers up to $50,000 of radon mitigation if a qualifying long-term test shows levels above 200 Bq/m³. The warranty travels with the home to subsequent owners.

For the full claim process, see our Tarion radon warranty claim guide. Note: meeting the test-type criteria is one of several conditions for a Tarion claim.

Local Mississauga and Peel resources

  • Peel Public Health — Radon (peelregion.ca/.../radon) — regional public-health radon information for Mississauga, Brampton, and Caledon
  • Cancer Care Ontario — Risk of Residential Radon Exposure (cancercareontario.ca)
  • Tarion — Radon warranty coverage (tarion.com)
  • Take Action on Radon — Ontario (takeactiononradon.ca/provinces/ontario)
  • Canadian Lung Association — Lungs Matter mitigation grant (lung.ca)
  • C-NRPP Find a Certified Professional (c-nrpp.ca) — Mississauga-area certified measurement and mitigation professionals

Note on Ontario building code. New-build Mississauga homes are subject to the 2024 Ontario Building Code, which requires a Level 1 radon "rough-in" province-wide.

Note on Ontario real estate disclosure. Ontario uses OREA's Form 220 (SPIS), which is voluntary but, once completed, requires truthful answers. The latent-defect doctrine applies. See our Real Estate Radon Guide.

FAQ — Mississauga-specific questions

How common is high radon in Mississauga? Mississauga sits in a lower-radon part of Ontario — the provincial average from the 2012 Cross-Canada Survey was about 8% of homes above the 200 Bq/m³ guideline, and Mississauga / GTA tend to test on the lower end of that. But Mississauga's substantial population means even a single-digit-percentage rate translates to a meaningful number of affected homes, and older Mississauga neighbourhoods carry higher than average risk. The only way to know your home's specific level is to test it.

Why is Mississauga lower-radon than other Canadian cities? Mississauga sits on the St. Lawrence Lowlands sedimentary basin (Ordovician shale and limestone bedrock), which contains lower uranium concentrations than the Canadian Shield bedrock under prairie cities like Calgary or Winnipeg.

Are some Mississauga neighbourhoods worse than others? Yes. Older Mississauga neighbourhoods — predominantly 1950s–1970s — carry higher risk than the city average due to older stone or block foundations and basements built before modern vapour barriers. Port Credit, Lakeview, Mineola, Lorne Park, and Clarkson are commonly cited examples; similar dynamics apply to other older parts of Mississauga (such as older sections of Streetsville and Cooksville). Newer subdivisions built since the 1990s typically have modern foundation construction and lower-than-average risk profiles, though individual home levels still vary substantially.

Does my newer Mississauga home have a radon rough-in? If your home was built under the 2024 Ontario Building Code (in force January 1, 2025), yes — there should be a capped vent pipe stub through the basement slab. Older Mississauga homes (built before 2025) generally do not have a radon rough-in, since the prior 2012 Ontario Building Code only required a rough-in in three designated areas (none of which were in Peel Region).

Can I claim Tarion warranty coverage if my Mississauga home tests above 200 Bq/m³? Possibly. If your home is in its 7-year Tarion warranty window from the original possession date, and you have a qualifying long-term test result above 200 Bq/m³, you may be able to claim up to $50,000 of Tarion-covered mitigation (for APS signed on or after February 1, 2021). See our full Tarion radon warranty claim guide.

How much does radon mitigation cost in Mississauga? Typical Ontario residential mitigation costs are $2,500–$4,500 for a sub-slab depressurization system installed by a C-NRPP-certified contractor. The Canadian Lung Association's Lungs Matter program may offset up to $1,500 for eligible homeowners.

Where can I buy a long-term radon test kit in Mississauga? You can order a RadonTest.ca $89 all-in long-term kit online and receive it within a few business days anywhere in Mississauga — kit + tracked outbound + prepaid tracked Canada Post return label + analysis at a C-NRPP-listed Canadian lab.

Do I have to disclose elevated radon when I sell my Mississauga home? Ontario uses OREA's Form 220 (SPIS), which is voluntary but, once completed, requires truthful answers. The latent-defect doctrine applies under common-law principles, and a known elevated radon reading is generally treated as a material defect requiring disclosure. See our full Real Estate Radon Guide.

When is the best time of year to test in Mississauga? The heating season — October through April — produces the highest indoor radon levels and is the recommended testing window per Health Canada.

Where can I find a C-NRPP-certified radon mitigator in Mississauga? The C-NRPP Find a Certified Professional directory lists certified measurement and mitigation professionals by area. Mississauga and the broader Peel Region have a substantial C-NRPP-certified mitigator network.

Test your Mississauga home — $89, all in

Mississauga is on the lower end of the Ontario radon spectrum — but "lower than average" isn't "zero," older Mississauga neighbourhoods carry meaningfully higher risk than the city average, and the only way to know whether your specific home is in the lower-risk majority or the higher-risk minority is to test.

RadonTest.ca — $89 all-in (plus applicable tax). Long-term 91-day alpha-track test kit. C-NRPP-listed device. Analysed at Lex Scientific in Guelph, Ontario — Canadian lab, C-NRPP listed, ISO/IEC 17025 accredited by CALA. Tracked Canadian shipping both ways. Written lab report PDF delivered to your inbox.

Order — $89 →

Important disclaimers

Not medical, legal, or warranty advice. This article provides general health and home-testing information for Mississauga homeowners drawn from publicly available Health Canada, Peel Public Health, Cancer Care Ontario, Tarion, Canadian Cancer Society, and Canada Radon (Peel testing services) materials. It is not medical advice, legal advice, or warranty advice. Consult a qualified professional for specific decisions.

Statistics and citations. Ontario provincial figures are from Health Canada's 2012 Cross-Canada Survey of Radon Concentrations in Homes. National figures are from Health Canada's Radon: What You Need to Know fact sheet (2025). Mississauga-specific neighbourhood-risk observations reflect general reporting about older GTA housing stock and are not based on a single comprehensive Mississauga-only survey. Verify with a home-specific test before drawing conclusions about your own home.

Local Mississauga data. Statements about Mississauga radon levels reflect published Ontario and Peel Region materials. Radon levels vary substantially even between adjacent homes; community-level statistics do not substitute for a home-specific long-term test.

Mitigation cost. The $2,500–$4,500 mitigation cost range is a typical Ontario residential figure. Actual costs vary by home, foundation, complexity, and contractor.

Tarion qualification. Statements that the alpha-track test "qualifies" or "meets Tarion test-type criteria" mean only that the test method matches Tarion's published test requirements. They are not a representation that any specific home, test, or claim will be approved. A complete Tarion radon warranty claim requires several conditions — see our Tarion claim guide and tarion.com for the complete requirements. RadonTest.ca is independent from Tarion.

Lungs Matter grant. Eligibility, grant amounts, and program availability for the Canadian Lung Association's Lungs Matter program may change. Verify directly at lung.ca before relying on the program.

Real estate disclosure. Statements about Ontario real estate disclosure reflect general OREA / common-law latent-defect principles. Specific obligations for any individual transaction depend on the facts; consult an Ontario real estate lawyer.

No diagnosis or treatment claims. RadonTest.ca sells radon test kits. We do not diagnose, treat, or prevent disease.

No warranty as to completeness. RadonTest.ca makes no warranty as to the completeness or accuracy of the information herein and accepts no liability for decisions made in reliance on this article.

Sources & further reading

Mississauga- and Peel-specific

Health Canada / national

National associations and grants

Related RadonTest.ca articles