Incidence of cancer among residents of high temperature geothermal areas in Iceland: A census based study 1981 to 2010
Objective: To assess whether residence in a high temperature geothermal area, where inhabitants are exposed to geothermal emissions and water containing hydrogen sulphide and radon, is associated with the risk of cancer. Design: Observational cohort study where the population of a high temperature geothermal area (35 707 person years) was compared with the population of a cold, non-geothermal area (571 509 person years). The follow up from 1981 to 2010 was based on record linkage by personal identifier with nation-wide death and cancer registries. Through the registries it was possible to ascertain emigration and vital status and to identify the cancer cases, 95% of which had histological verification. The hazard ratio (HR) and 95% confidence intervals (CI) were estimated in Cox-model, adjusted for age, gender, education and housing. Setting: Iceland with 229 000 inhabitants. Participants: Persons 5 to 65 years of age from the 1981 National Census, total 74 806 individuals. Results: Adjusted HR in the high-temperature geothermal area for all cancers was 1.22 (95% CI 1.05 to 1.42) as compared with the cold area. The HR for pancreatic cancer was 2.85 (95% CI 1.39 to 5.86), bone cancer 5.80 (95% CI 1.11 to 30.32), breast cancer 1.59 (95% CI 1.10 to 2.31), lymphoid and hematopoietic cancer 1.64 (95% CI 1.00 to 2.66), and non-Hodgkin´s lymphoma 3.25 (95% CI 1.73 to 6.07). The HR for basal cell carcinoma of the skin was 1.61 (95% CI 1.10 to 2.35). The HRs were increased for cancers of the nasal cavities, larynx, prostate, thyroid gland and for soft tissue sarcoma; however the 95% CI included unity. Conclusion: More precise information on exposure is needed to draw firm conclusions from the findings. The significant excess risk of breast, and basal cell carcinoma of the skin, and the suggested excess risk of other radiation-sensitive cancers, indicates that radon exposure may contribute to the risk of cancer among the population in the high-temperature geothermal area. There are indications of an exposure-response relationship, as the risk was higher in comparison with the cold than with the warm reference area. Social status has been taken into account and data on reproductive factors and smoking habits show that these do not seem to explain the increased risk of cancers.
Lýðheilsuvísindi, Háhitasvæði, Krabbamein
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