The follow up of incidence of malignant mesothelioma using GIS

Introduction
The aim of the current study was to extend the previously presented cohort of malignant mesothelioma cases (1964–2005) on the Slovenian territory to the year 2009 and to predict the possible new shape of mesothelioma curve.

Methods
The cohort of mesothelioma cases has been followed by the Cancer Register at the Institute of Oncology Ljubljana. Using the Geographical Information System (GIS), it was possible to locate each mesothelioma case on the map of Slovenia, city/village and the map representing individual streets/buildings. A regression equation was used to calculate the mesothelioma trend in the next years predicted by the incidence in the past 40 years.

Results
In the period from 1964 to 2009, approximately 600 mesothelioma cases were diagnosed. We still observe 4 major clusters: one around the largest asbestos-cement plant in Slovenia, one around the shipyard, one around the train factory and one in the central Slovenia, where different smaller asbestos users were located. More than 90% of all cases lived within a 2-km radius of the asbestos main sources and/or worked in one of the asbestos plants. By using the sophisticated GIS, we located industrial sources, waste material disposals and wind direction on the same map. The curve of the mesothelioma incidence from 1964 to 2009 is exponential. According to the calculated trend, it is still difficult to predict the plateau of the curve.

Discussion
Based on the results it is necessary to rethink the quality of cleaning the environment polluted by asbestos, to search for unknown sources and to intensively study new screening methods for an early mesothelioma detection. The method used for this study could be used in any other country.