Correlation between radon and skin cancer risk unclear

After smoking, the radioactive noble gas radon is the most important cause of lung cancer. Scientists from the Swiss Tropical and Public Health Institute (Swiss TPH) in Basel have now investigated whether there is a further correlation between radon exposure in the home and the risk of dying from skin cancer. The study was published in the specialist journal "Environmental Health Perspectives". In the view of the BfS, the Swiss study provides no conclusive evidence that radon is a relevant risk factor for skin cancer – even if radon causes the skin considerable radiation exposure.

Content and findings of the study

The trigger for the study is the high number of malignant melanoma cases (malignant skin cancer). After Australia and New Zealand, Switzerland has the third highest illness rate in the world. For the study, 1,900 deaths from malignant melanoma in the years 2000 to 2008 in people under the age of 20 from throughout Switzerland were analysed. Researchers calculated the radon exposure of these people in their homes using a model based on around 45,000 measurements from the Swiss Federal Office of Public Health. The UV levels to which people were exposed in their homes were also measured.

The study found that the risk of dying from malignant melanoma rises with increasing radon exposure. The increase in risk falls with increasing age. So according to the study, the risk of dying from malignant skin cancer increases in 30-year-olds by 41 percent for each increase in radon exposure by 100 becquerels per cubic metre and for 60-year-olds by 16 per cent. In addition, the study investigated the risk of dying from other types of skin cancer (e.g. basal cell carcinoma, squamous cell carcinoma). No significant correlation was found between these and radon exposure.

Evaluation of the study

It is unclear whether the risk increase for malignant melanoma observed in the study is attributable to long-term radon exposure. Important factors that influence the risk of dying from malignant skin cancer are insufficiently or not at all considered in the study.

So although the most important risk factor for the incurrence of skin cancer – UV radiation – was also investigated, it was not in an appropriate form. Playing a central role in melanoma risk are the sudden exposure of untanned skin to UV radiation, for example by holidaying in regions with a high UV index, the number of birthmarks and the number of incidents of sunburn.

Also, it has been ascertained in different studies that it is important in the investigation of skin cancer risk to carefully consider social status so as to avoid any bias. Furthermore, mortality depends on how early the skin cancer is detected. If one of these factors correlates with the calculated radon exposure, an ostensible correlation could arise.

The study further indicates weaknesses in the determination of radon exposure: The radon concentrations in the home were not measured but were estimated from calculations – and these only for the home in which the person lived at the start of the study.

In summary it can be ascertained that the study provides no conclusive evidence that radon in the home increases the skin cancer risk. However, in cohort studies such as the German uranium mine workers study, no increased mortality from skin cancer has been observed to date compared with the general population – even though the radon concentrations for underground workers in uranium mines are generally significantly higher than in the general population. This does not preclude that radon could present a risk factor for skin cancer. However, the findings of the mine workers study conclusively supported the evidence that the risk of developing lung cancer from radon is significantly higher than the possible skin cancer risk.

Regardless of the findings of the Swiss study, it is clear that increased radon concentrations in spaces that are used frequently and for many hours through the day present an appreciable health problem. Therefore, protective measures should be considered when planning both new-builds as well as the structural renovation of houses.