A prospective cohort study on the association between residential radon exposure and melanoma incidence in Switzerland

Abstract

Background and Aim: Radon is radioactive noble gas found in earth crust. It tends to accumulate in buildings, and is estimated to account for half of the ionizing radiation dose received by humans. Skin is the second most exposed organ to ionizing radiation from radon. The aim of this study was to evaluate the association between residential radon exposure and melanoma incidence in selected Swiss cantons. Methods: The study included 1.3 million adults (20+ years) from the Swiss National Cohort (SNC) who were residents in the cantons of Vaud, Neuchâtel, Valais, Geneva, Fribourg, and Ticino at the study baseline (04.12.2000). Cases of primary tumours (ICD-O-3: 8720-8790/3+ melanoma) were identified using data from these cantonal cancer registries, linked to the SNC. Long-term residential radon and ambient ultraviolet exposure from sun were assigned to each individual’s addresses at baseline. We used Cox proportional hazard models with age as the underlying time scale and adjusted for birth cohort, canton, sex, socioeconomic position, educational attainment, civil status, mother tongue, outdoor occupation with potential sun exposure as fixed explanatory variables and stratified by follow-up period. Potential effect modifiers were also tested. Results: Among the study population, we observed 4937 incident cases of melanoma during an average 8.9 years of follow-up. The adjusted hazard ratio for per 100 Bq/m³ increase in residential radon levels at age 45 was 1.11 (95% CI: 1.00, 1.23). Radon effect was higher at younger ages and became null at higher ages. Ambient long-term UV exposure was not associated with melanoma incidence across all ages. Conclusion: Residential radon exposure might be a relevant risk factor for melanoma incidence, especially for people at younger ages. Accumulation of radon gas is preventable via built-in solutions applicable to dwelling. Such measures are important for public health. Keywords: Radon exposure, melanoma incidence, prospective cohort, Switzerland