Hazard connected to endogenous gas emissions in Greece

Abstract

Like other geodynamically active areas, Greece is also affected by a large number of geogenic gas manifestations that occur either in form of point sources (fumaroles, mofettes, bubbling gases) or as diffuse soil gas emanations. Geogenic sources could have strong impact on human health. CO2 and H2S are the main gases responsible for acute mortality due to their asphyxiating and/or toxic properties. Gas hazard is often disregarded because in fatal episodes the death cause is often not correctly attributed. Geodynamic active areas can release geogenic gases for million years over wide areas and it is therefore important not to underestimate potential risks. A preliminary estimation of the gas hazard has been made for the time period of the last 20 years considering the whole population of Greece. In this period at least two fatal episodes with a total of three victims can be attributed to geogenic gases (specifically CO2). This gives a risk of 1.3x10-8 fatalities per annum. This risk is unevenly distributed and depends on many factors with the most important being the geographical distribution of the gas manifestations, while also the source strength, the gas composition, the meteorological conditions and the topography of the area will contribute to the determination of the local risk. Although low, this risk has not to be neglected, not only because possibly underestimated but also because simple countermeasures could be adopted. Dangerous areas can be easily identified and delimited by geochemical prospections and their hazard properly evidenced.