Volcanic environments: "biomonitoring" their links to thyroid cancer.

Abstract

Thyroid cancer is on the increase in many parts of the world, in particular the papillary histotype and its follicular variant. Meanwhile, microcarcinomas are multiplying at a faster rate than larger tumors, although it has recently been reported that more aggressive forms are also on the rise [1–3]. While this upsurge in thyroid cancer incidence has been attributed by a number of researchers to the increasing application of sophisticated image technology, an array of environmental factors may also be inculpated [4]. Thus, increased exposure to radiation, nutritional determinants as high intake of iodine and selenium deficiency, and certain industrialized carcinogens in our industrialized lifestyle are all likely to be involved [5]. In the past few decades, volcanic areas have also been associated with increased incidence of papillary thyroid cancer (PTC). This has put volcanology in the spotlight for the purpose of deciphering the putative mechanisms generating the disease, while also exploring the potential of this natural phenomenon to act as a disease promoter. For example, in a register-based epidemiologic study it was shown that residents of Catania province, Sicily, living in proximity to Italy’s largest volcano, Mount Etna, had a higher incidence of PTC than the population of the rest of Sicily [6]. Although there are objective limitations to interpreting findings from population-based registries, the intensity of screening carried out in special centers in the vicinity of the volcano should be carefully considered while also bearing in mind the geophysical factors [7]. In this connection, of particular interest is the paper by Malandrino et al., recently published in Endocrine [8], which sheds considerable light on the present topic and offers a degree of insight into the various pathways linking volcanoes to development of thyroid cancer [8]. The authors conducted a cohort comparison study, evaluating a number of environmental pollutants in the water and atmosphere, in residents of the volcanic area surrounding Mount Etna in the province of Catania and in a control area. In the volcanic region, they laid emphasis on assessment of the level of biocontamination by the ‘‘trace element pollution’’ produced by eruptions, which, inevitably, modifies the surroundings. This ultimately impacts human health, since retention of these elements in the soils results in their being readily transferred into water and plants, and so on up the food chain. Based on data obtained from the Sicilian Regional Registry for Thyroid Cancer, thyroid cancer incidence doubled in the volcanic area as compared to the control area (from 18.5 to 9.6/105 inhabitants in the volcanic and the control areas, respectively), the increase concerning mainly the papillary histotype. In the volcanic area, several trace elements were increased in both drinking water, in particular, and in lichens as compared to the control area, hence demonstrating water as well as atmospheric pollution [8]. & Leonidas H. Duntas ledunt@otenet.gr