People living in areas with the highest mapped radon exposure have more than double the risk of lung cancer, according to a study led by Queen’s University Belfast (QUB), supporting the use of radon mapping to help guide prevention and screening initiatives.

Published in the journal Environmental Geochemistry and Health, this population-based case-control study investigated the association between residential radon atlas metrics and lung cancer risk in Northern Ireland, where screening programmes are currently under development.

The study linked national radon mapping data with cancer statistics from the Northern Ireland Cancer Registry to assess whether geographical differences in exposure corresponded with differences in lung cancer risk.

The authors analysed 1,687 primary lung cancer cases diagnosed in 2006 and 2014 and compared them with 8,094 healthy controls drawn from the Northern Ireland Cohort for the Longitudinal Study of Ageing – an initiative run by QUB.

Cases and controls were linked to the UK Health Security Agency and British Geological Survey’s Indicative Atlas of Radon using postcode data.

The atlas categorised 1 km² areas according to the percentage of homes exceeding the radon action level of 200 Bq/m³, ranging from Class 1 areas in which less than 1% of homes were above the threshold, through to Class 6 in which 30–100% of homes were above the threshold.

Logistic regression models adjusted for age, sex, smoking status, deprivation and particulate matter (PM)2.5 exposure were used to estimate lung cancer risk.

Lung cancer risk and radon levels

Overall, individuals living in the highest radon exposure areas (Class 6) had more than double the risk of lung cancer compared with those living in lower exposure areas (adjusted odds ratio [OR] 2.24, 95% CI 1.25–3.92).

The association became apparent only after adjustment for PM2.5 exposure, which the authors identified as an important negative confounder because urban areas in Northern Ireland with higher air pollution tended to have lower radon exposure.

Subgroup analyses showed stronger associations in men (OR 2.84, 95% CI 1.30–6.07) and in small-cell carcinoma (OR 4.39, 95% CI 1.45–10.91). Elevated risks were also observed for adenocarcinoma (OR 3.08, 95% CI 1.24–6.62).

The authors estimated that 0.7% of lung cancer cases in Northern Ireland could theoretically be attributable to residence in the highest radon atlas category, equating to approximately 10 preventable cases annually.

However, they stressed that these estimates should be treated as illustrative given the limitations of area-based exposure assessment.

Supporting targeted screening strategies

The absence of household-level radon measurements, the lack of lifetime residential histories and no information on occupational radon exposure limited the study’s findings. Atlas-based exposure classification could underestimate the true radon-related risk because many homes in the highest atlas category may still fall below the action threshold, the authors said.

Nevertheless, they noted that the findings support the epidemiological utility of publicly available radon atlas data, particularly in settings where individual household measurements are unavailable.

Senior study author, Dr Daniel Middleton, lecturer at QEB’s Cancer Epidemiology and Data Research Group, said: ‘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.

‘It also highlights that moving towards more detailed, continuous estimates of radon concentration could support more advanced research and help refine how we target prevention efforts.

‘However, it is important to emphasise that smoking remains the dominant cause of lung cancer. Stopping smoking is still the most effective way to reduce risk. Notably, most radon-related lung cancer patients also smoke cigarettes.’

Dr Middleton and his team concluded that future studies should evaluate the cost-effectiveness of targeting high-radon regions for lung cancer awareness campaigns and screening initiatives, particularly as targeted lung cancer screening expands across the UK.

Reference
Delargy CM et al. Lung cancer risk in relation to indicative radon atlas metrics in Northern Ireland: a population-based case–control study using secondary data. Environ Geochem Health 2026;48:295.