First UK study links higher radon areas to significantly increased lung cancer risk

The radon map of Northern Ireland

People living in parts of Northern Ireland with the highest radon levels are more than twice as likely to develop lung cancer, according to a major new study that for the first time connects national radon mapping with cancer registry data at a regional scale.

The research, led by Queen’s University Belfast in collaboration with Trinity College Dublin, analysed radon exposure patterns alongside data from the Northern Ireland Cancer Registry (NICR), revealing clear differences in lung cancer risk between areas with varying radon levels.

Published in the international journal Environmental Geochemistry and Health, the findings mark the first UK-wide effort to directly link mapped radon exposure with cancer outcomes in this way, offering new insight into how environmental factors may influence disease risk across communities.

Clear link between radon levels and cancer risk

The study found that residents in areas classified as having the highest radon concentrations had more than double the likelihood of developing lung cancer compared with those living in lower exposure areas.

Crucially, this association remained even after researchers accounted for other major risk factors, including smoking, air pollution, age, sex and socioeconomic conditions. This suggests the variation in cancer risk cannot be explained by those factors alone.

Radon is a naturally occurring radioactive gas that is invisible and odourless, that forms when uranium, a metal found in rocks and soil, slowly breaks down underground. It has no colour, smell or taste, which means it can build up inside homes and buildings without being noticed.

Radon typically seeps up through the ground and can enter properties through cracks in floors, gaps around pipes, or spaces in walls and foundations. Levels can vary widely depending on local geology, with certain areas more prone to higher concentrations due to the type of rock beneath them.

Low awareness despite simple testing options

Despite the risks, awareness of radon exposure remains low, with many households unaware they may be living in areas where higher levels are more likely.

Testing for radon is relatively straightforward and costs around £50, with national radon maps providing an initial guide to whether a property may be in a higher risk area. However, researchers caution that elevated levels can still occur in homes located in areas generally classified as low risk.

Lead author Claire Delargy, a PhD researcher with the Cancer Epidemiology and Data Research (CEDAR) Group at Queen’s University Belfast, said the findings underline the practical value of existing tools for the public.

“Radon cannot be seen or smelt, but it can be measured relatively easily, and testing is the only way to know the levels in your home,” she said.

Public health implications and need for better mapping

Researchers say the study highlights opportunities to strengthen public health approaches, particularly by improving awareness and encouraging more widespread testing in areas where elevated radon levels are more likely.

Current UK radon maps categorise areas into broad bands rather than providing continuous, high-resolution estimates of concentration. The study suggests that more detailed mapping could allow for a more precise understanding of how risk varies geographically and support more advanced epidemiological research.

Senior author Dr Daniel Middleton, also from the CEDAR Group at Queen’s University Belfast, said the findings demonstrate how existing data can already be used to inform public health decisions, while pointing to areas for improvement.

“This study shows that widely available radon maps can reflect differences in lung cancer risk at a population level, which has important implications for public health,” he said, adding that more detailed mapping could help refine how prevention efforts are targeted.

He also stressed that while radon is a significant factor, smoking remains the dominant cause of lung cancer, noting that most radon-related lung cancer cases occur in people who smoke.

Population-level findings, not individual risk

The researchers emphasise that the study is based on area-level radon estimates rather than measurements from individual homes, meaning exposure levels can vary within mapped regions.

As a result, the findings reflect patterns across populations rather than predicting individual risk, reinforcing the importance of household testing to understand personal exposure.

The study adds to growing evidence that environmental factors such as radon play a measurable role in cancer risk, with the findings expected to inform future research, public health messaging and potential improvements in how risk is mapped and managed across Northern Ireland.

UK maps of radon

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At a glance

• First UK study to link radon mapping data with cancer registry statistics at regional scale

• People in highest radon areas more than twice as likely to develop lung cancer

• Link remains after accounting for smoking, pollution, age, sex and deprivation

• Radon is invisible and odourless but can build up indoors

• Home testing costs around £50 and is the only way to confirm levels

• Awareness of radon risk remains low among households

• Current radon maps use broad categories rather than detailed estimates

• Researchers call for improved mapping and increased public awareness

• Smoking remains the leading cause of lung cancer overall