When Canadians picture a radon-exposed worker, they picture a miner. The peer-reviewed evidence says otherwise.
The occupations with the largest numbers of radon-exposed workers in Canada are administrative assistants, general office support workers, receptionists, and elementary and kindergarten teachers.
TL;DR: A 2022 study in Scientific Reports estimates that 603,000 Canadian workers are exposed to radon above 100 Bq/m³ — about 3.3% of the workforce. Roughly two-thirds of them sit between 100 and 200 Bq/m³, below Canada's action level. The new federal workplace limit, in force 30 January 2027, applies to federally regulated workplaces — around 8% of the Canadian workforce — while the highest-exposure industries the research identifies sit largely in provincial jurisdiction.
What the research found
The study is Characterizing occupational radon exposure greater than 100 Bq/m³ in a highly exposed country, published in Scientific Reports in December 2022 by researchers at CAREX Canada, the University of Calgary, the Occupational Cancer Research Centre and BC Cancer.
It is the first systematic assessment of radon exposure across the whole Canadian workforce rather than only among uranium and underground workers. Radon concentrations from two Canadian workplace surveys were modelled and applied to the indoor worker population by occupation, industry, province and sex, using 2016 labour force data.
These are modelled estimates, not a census of measurements. That is a real limitation and the authors say so: they call for radon surveys across more industries and occupations to characterise occupational exposure properly. It remains the best national estimate available.
Of Canada's 18,268,120 workers, an estimated 603,000 are exposed to radon above 100 Bq/m³.
| Exposure level | Share of exposed workers | Approximate number |
|---|---|---|
| 100–200 Bq/m³ | 68% | 413,000 |
| 200–400 Bq/m³ | 23% | ~139,000 |
| 400–800 Bq/m³ | 5.8% | ~35,000 |
| Above 800 Bq/m³ | 2.8% | ~17,000 |
An important distinction, and it cuts against the headline. The 603,000 figure is exposure above 100 Bq/m³ — the World Health Organization's reference level, not Canada's. Canada's action level is 200 Bq/m³. Roughly a third of the 603,000 — about 190,000 workers — are above the Canadian guideline. The remaining two-thirds are in a band where Health Canada recommends no action is required.
That is the honest reading, and it is also where the story gets more interesting rather than less.
Where the exposure actually is
The industries with the largest numbers of exposed workers are educational services; professional, scientific and technical services; health care and social assistance; and public administration.
Mining, quarrying, and oil and gas extraction behave differently. That sector has comparatively few exposed workers in total, but the largest proportion at the extreme end: 43.6% of its exposed workers are above 800 Bq/m³, compared with 1.5% in educational services.
So there are two distinct pictures. A small number of workers exposed to very high concentrations in resource extraction — already governed by the Naturally Occurring Radioactive Materials framework and, for uranium, by the Canadian Nuclear Safety Commission. And a much larger number of office, school and health care workers exposed to moderate concentrations, most of whom have never been considered a radon-exposed population at all.
One finding that has had almost no attention
The study estimates that 52% of exposed workers are women, although women make up 48% of the labour force.
The study reports that difference as a finding; it does not set out a cause, and we are not going to supply one. What can be said is narrower and still worth saying: radon exposure in Canada is not evenly distributed across the workforce, and any occupational health response built on the assumption that the exposed population looks like a mining workforce will miss most of the people in it.
What the new federal limit reaches
On 30 January 2027, SOR/2026-10 lowers the radon exposure limit for federally regulated workplaces from 800 to 200 Bq/m³ as an annual average. A federal limit has existed for years — what changes is the number, which drops fourfold, and the wording, which shifts from “no employee shall be exposed” to “the employer must ensure.”
Its scope is defined by jurisdiction rather than by exposure. The Regulatory Impact Analysis Statement accompanying the regulation states that Part II of the Canada Labour Code “applies to all federally regulated work places, which employ approximately 1.3 million employees, or about 8% of the Canadian workforce.”
Those workplaces are air, rail, road and marine transportation; pipelines; banks; telecommunications and broadcasting; postal and courier services; grain elevators and feed and seed mills; uranium mining; Crown corporations; First Nations band councils; Parliament; and the federal public administration.
Set that list beside the industries the research identifies as most exposed. Educational services, health care and social assistance, and professional, scientific and technical services are overwhelmingly provincially regulated. Public administration is split — the federal public service is covered, provincial and municipal government is not.
We are not putting a number on the overlap, and neither does the research; exposure is not distributed evenly across jurisdictions and any figure would be invented. But the qualitative point is not in dispute: the sectors where the most radon-exposed Canadian workers are found sit largely outside the reach of the new federal limit.
This is not a criticism of the regulation. Federal jurisdiction is what the federal government can legislate for, and lowering the limit from 800 to 200 within that jurisdiction is a real protection for 1.3 million people. It is an observation about the gap between where a rule applies and where an exposure sits — and about who has to act without a rule telling them to.
The 100–200 band is not a footnote
Two-thirds of exposed Canadian workers — some 413,000 people — are in the 100 to 200 Bq/m³ range. Below Canada's action level. Above the WHO reference level.
Three things make that band matter more than it first appears.
There is no threshold below which radon is harmless. Risk is a function of concentration multiplied by duration and declines continuously as concentration falls; it does not switch off at any particular number. Health Canada advises that mitigation is worth considering where results approach the guideline.
A second Canadian study points the same way. Work published in the International Archives of Occupational and Environmental Health estimated the lung cancer burden from occupational radon exposure in Canada and concluded that the greatest burden occurs among workers exposed at low levels — because there are so many more of them. A small risk across a large population produces more cases than a large risk across a small one.
In fairness to that paper, its headline finding is that the overall burden is small: roughly 0.8% of Canadian lung cancers, about 188 cases in 2011, attributable to occupational radon exposure. We are not claiming a hidden epidemic. The point is narrower and it is the authors’ own: within that burden, most of it sits with workers at lower exposure levels, not with the small number at very high ones.
And the federal regulation itself directs attention to that band. Section 10.4(2)(h) of the Canada Occupational Health and Safety Regulations lists, among the criteria a qualified person must consider during a hazard investigation, whether radiation levels are likely to exceed 50 per cent of the applicable limits. Once the limit is 200 Bq/m³, 50 per cent of it is 100 Bq/m³.
That is not a second exposure limit and it creates no obligation to act at 100 Bq/m³. But it means the regulation asks a qualified person to consider exactly the range in which the research places two-thirds of Canada's exposed workers. The empirical data and the regulatory criterion converge on the same number, apparently by coincidence, and nobody appears to have noticed.
What this means if you are a provincially regulated employer
No province or territory has a radon-specific workplace exposure limit. That does not mean nothing applies.
Every Canadian jurisdiction imposes a general duty on employers to take reasonable precautions against recognised hazards. Radon is a Group 1 carcinogen, it is the second leading cause of lung cancer in Canada, and Health Canada's 200 Bq/m³ guideline covers all indoor spaces including workplaces. A recognised hazard with a published national guideline is squarely within what a general duty is meant to catch.
The practical trigger is almost always a person rather than an inspector: a worker asks, a health and safety committee raises it, a tenant enquires. From that point the hazard is identified and the employer knows. What happens next is the entire question — and inaction after identification is precisely what general duty provisions exist to address.
For a school board, a hospital, a municipality or a professional services firm, this research is the clearest available answer to “why would we test?” Their sector is named in it.
Common questions
How many Canadian workers are exposed to radon?
An estimated 603,000 are exposed above 100 Bq/m³, about 3.3% of the workforce, according to Brobbey et al. (2022). Roughly 190,000 of those are above Canada's action level of 200 Bq/m³.
Which workers are most exposed?
By number, administrative assistants, general office support workers, receptionists, and elementary and kindergarten teachers. By industry, educational services; professional, scientific and technical services; health care and social assistance; and public administration.
Aren't miners the most exposed?
Miners are the most exposed by level, not by number. 43.6% of exposed workers in mining, quarrying and oil and gas extraction are above 800 Bq/m³, against 1.5% in educational services. But far more people work in offices and schools.
Does the new federal limit cover these workers?
Only where the employer is federally regulated — about 8% of the Canadian workforce. Education, health care and most professional services are provincially regulated, where the general duty applies instead of a numeric limit.
Is 100–200 Bq/m³ dangerous?
Health Canada recommends no action below 200 Bq/m³. No radon concentration is risk-free, and Canadian research suggests the largest share of the occupational lung cancer burden falls among workers exposed at lower levels, simply because there are far more of them. Health Canada is the health authority on radon in Canada and its guidance is the reference.
Read next
Which rules apply to your workplace · Workplace radon rules by province · Our result came back at 180 — are we finished? · How commercial radon testing works
RadonTest.ca provides testing logistics and laboratory submission. We do not perform radon mitigation and we do not interpret health risk — Health Canada is the health authority on radon in Canada. This page summarises published research and publicly available regulatory information and is not legal or health advice. The research described here was conducted independently of RadonTest.ca and its authors have no connection to this company.
Sources
Brobbey A, Rydz E, Fenton S, Demers PA, Ge CB, Peters CE. “Characterizing occupational radon exposure greater than 100 Bq/m³ in a highly exposed country.” Scientific Reports 2022;12:21323. doi:10.1038/s41598-022-25547-x. Open access.
Ge CB, Kim J, Labrèche F, Song C, Heer E, Arrandale VH, Pahwa M, Peters CE, Demers PA. “Estimating the burden of lung cancer in Canada attributed to occupational radon exposure using a novel exposure assessment method.” International Archives of Occupational and Environmental Health 2020;93:871–876.
Canada Gazette, Part II, Vol. 160, No. 3 — SOR/2026-10 and its Regulatory Impact Analysis Statement; Canada Occupational Health and Safety Regulations (SOR/86-304), ss. 10.4, 10.26; Health Canada, Canadian radon guideline; CAREX Canada; International Agency for Research on Cancer, Monograph Vol. 100D.