Association of Cancer Incidence and Duration of Residence in Geothermal Heating Area in Iceland: An Extended Follow-Up

<div><p>Background</p><p>Residents of geothermal areas have higher incidence of non-Hodgkin’s lymphoma, breast cancer, prostate cancer, and kidney cancers than others. These populations are exposed to chronic low-level ground gas emissions and various pollutants from geothermal water. The aim was to assess whether habitation in geothermal areas and utilisation of geothermal water is associated with risk of cancer according to duration of residence.</p><p>Methods</p><p>The cohort obtained from the census 1981 was followed to the end of 2013. Personal identifier was used in record linkage with nation-wide emigration, death, and cancer registries. The exposed population, defined by community codes, was located on young bedrock and had utilised geothermal water supply systems since 1972. Two reference populations were located by community codes on older bedrock or had not utilised geothermal water supply systems for as long a period as had the exposed population. Adjusted hazard ratio (HR), 95% confidence intervals (CI) non-stratified and stratified on cumulative years of residence were estimated in Cox-model.</p><p>Results</p><p>The HR for all cancer was 1.21 (95% CI 1.12–1.30) as compared with the first reference area. The HR for pancreatic cancer was 1.93 (1.22–3.06), breast cancer, 1.48 (1.23–1.80), prostate cancer 1.47 (1.22–1.77), kidney cancer 1.46 (1.03–2.05), lymphoid and haematopoietic tissue 1.54 (1.21–1.97), non-Hodgkin´s lymphoma 2.08 (1.38–3.15) and basal cell carcinoma of the skin 1.62 (1.35–1.94). Positive dose-response relationship was observed between incidence of cancers and duration of residence, and between incidence of cancer and degree of geothermal/volcanic activity in the comparison areas.</p><p>Conclusions</p><p>The higher cancer incidence in geothermal areas than in reference areas is consistent with previous findings. As the dose-response relationships were positive between incidence of cancers and duration of residence, it is now more urgent than before to investigate the chemical and physical content of the geothermal water and of the ambient air of the areas to detect recognized or new carcinogens.</p></div

Kaplan-Meier estimates of event free proportion for breast cancer, prostate cancer, pancreas cancer and non-Hodgkin’s lymphoma (NHL) since the census 1981.

<p>Dashed line indicates population in geothermal heating area, and black line population in the cold reference area.</p

Kaplan-Meier estimates of event free proportion for all cancers since the census 1981, dashed line indicate population in geothermal heating area, and black line population in the cold reference area.

<p>Kaplan-Meier estimates of event free proportion for all cancers since the census 1981, dashed line indicate population in geothermal heating area, and black line population in the cold reference area.</p

Number of all cancers and selected cancer sites among men and women combined, hazard ratio (HR), 95% confidence intervals (CI) compared with the populations in warm reference area and cold reference area, adjusted for age, gender, education, type of housing, and smoking habits, without and with stratification into categories of cumulative years of residence in the respective areas.

<p>Number of all cancers and selected cancer sites among men and women combined, hazard ratio (HR), 95% confidence intervals (CI) compared with the populations in warm reference area and cold reference area, adjusted for age, gender, education, type of housing, and smoking habits, without and with stratification into categories of cumulative years of residence in the respective areas.</p

Population numbers and CHD deaths in Iceland in 2010, and expected population numbers and CHD deaths in 2040 if 2010 rates persist.

<p>Population numbers and CHD deaths in Iceland in 2010, and expected population numbers and CHD deaths in 2040 if 2010 rates persist.</p

Estimated deaths per 100.000 prevented or added in 2040.

<p>Estimated deaths by risk factor change, under three risk factor scenarios.</p

Future CHD mortality rate among 25–74 year old Icelanders in three different risk factor scenarios.

<p>Future CHD mortality rate among 25–74 year old Icelanders in three different risk factor scenarios.</p

Data on sample characteristics and risk factor values from the Reykjavik study (1981) and REFINE Reykjavik study (2006 and 2010).

<p>Data on sample characteristics and risk factor values from the Reykjavik study (1981) and REFINE Reykjavik study (2006 and 2010).</p

Data sources.

<p>CHD mortality in 2010 was not available.</p

CHD deaths per 100,000 prevented or added as a result of risk factor changes, under three cardiovascular risk factor scenarios.

<p>May not sum to total due to rounding.</p