| Summary: | Background and aims: Previous studies in geothermal and volcanic areas have shown high risk of certain types of cancers. The aim was to study the association between residence in geothermal areas and the incidence and mortality of cancer in Iceland. Material and Methods: Studies I - IV are all population-based cohort studies. Records for individuals aged 5-64 years were obtained from the 1981 census, and they were followed through the years 1981-2013. A personal identifier was used in record linkage with nation-wide emigration, cause-of-death, and cancer registries. The exposed and reference populations were defined according to community codes, different ages of hot water supply systems, and age of bedrock. Hazard ratio, 95% confidence intervals stratified with and without cumulative years of residence were estimated in Cox-model, and different covariates were taken into account. Result: In these studies, with 33 years of follow-up, and nearly 1000 cancer cases, a high incidence was found in the population of the geothermal areas in comparison with the reference populations for all cancers combined, pancreatic cancer, breast cancer, prostate cancer, kidney cancer, combined cancers of the lymphoid and haematopoietic tissue, non-Hodgkin lymphoma and basal cell carcinoma of the skin. In the mortality study, high mortality for breast cancer, prostate cancer, kidney cancer, and non-Hodgkin lymphoma, in addition to high mortality for suicide and influenza were found in the populations of geothermal areas compared with the reference populations. The cumulative years of residence increased the risk, and dose response relation was found through the degree of volcanic/geothermal activity. Requiring five years latency yielded a higher hazard ratio. Conclusion: The result indicates high cancer risk in geothermal areas. The cause for this high incidence is not known from these ecological studies. Further studies are needed on the chemical and physical content of the geothermal water and the ambient air of the areas to ...
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