Cancer mortality and other causes of death in users of geothermal hot water

Background: Residents of geothermal areas have increased incidence of non-Hodgkin’s lymphoma, breast, prostate, and kidney cancers. The aim was to study whether this is also reflected in cancer mortality among the population using geothermal hot water for space heating, washing, and showering.

Methods: The cohort, 5-64 years of age, origin from the census 1981 and was followed through 1981-2009. Personal identifier was used in record linkage with nation-wide death registry. The exposed population was from communities with district heating generated from geothermal wells since 1972. Reference populations were from other areas with different degrees of volcanic/geothermal activity. Hazard ratio (HR) and 95% confidence intervals (CI) were adjusted for age, gender, education, housing, reproductive factors and smoking habits.

Results: Among those using geothermal water, the HR for all causes of death was 0.98 (95%CI 0.91-1.05) as compared with cold reference area. The HR for breast cancer was 1.53 (95%CI 1.04-2.24), prostate cancer 1.74 (95%CI 1.21-2.52), kidney cancer 1.78 (95%CI 1.03-3.07), and for non-Hodgkin’s lymphoma 2.01 (95%CI 1.05-3.38). HR for influenza was 3.36 (95%CI 1.32-8.58) and for suicide 1.49 (95%CI 1.03-2.17).

Conclusion: The significant excess mortality risk of breast, and prostate cancers, and non-Hodgkin’s lymphoma confirmed the results of similarly designed studies on cancer incidence among populations from high-temperature geothermal areas and users of geothermal hot water. The risk is not restricted to cancers with good prognosis, but also concerns fatal cancers. Further studies are needed on the chemical and physical content of the water and the environment emissions in geothermal areas.