Chronic exposure to volcanic environments and cancer incidence in the Azores, Portugal.

Whether volcanic environments pose a risk in cancer incidence is unknown. We investigated this question in two populations, one from an area with active manifestations of volcanism (Furnas) and another from an area without volcanic activity since 3 million years ago (Santa Maria), both in Azores. Incidence data on cancer among the populations of Furnas and Santa Maria during 1991-2001 were obtained from medical records of local health centers. Age-standardized rates and relative risks were estimated. Overall incidence rates were higher in the volcanically active area when observing all cancers and both sexes combined. However, the non-volcanically active area presented higher rates of cancer of digestive, respiratory and intrathoracic organs, mainly in males, while the area with volcanic manifestations showed higher rates of cancer of lip, oral cavity and pharynx, in both sexes, and female breast. Relative risk estimates between both populations suggest a higher risk for cancer in some groups of organs in Furnas, especially of lip, oral cavity and pharynx cancer, and breast, that may be partially explained by the chronic exposure to environmental factors resulting from volcanic activity, such as hazardous gases and aerosols, much of them associated to trace metals.