Preliminary gas hazard evaluation in Greece

Like other geodynamically active areas, Greece is also affected by a large number of geogenic gas manifestations. These occur either in the form of point sources (fumaroles, mofettes, bubbling gases) or as diffuse soil gas emanations. Geogenic sources release huge amounts of gases, which, apart from having important influences on the global climate, could also have a strong impact on human health. Gases have both acute and chronic effects. Carbon dioxide (CO2) and hydrogen sulphide are the main gases responsible for acute mortality due to their asphyxiating and/or toxic properties. Methane instead represents a risk for its explosive properties. Gas hazards are often disregarded because in fatal episodes connected to geogenic gases, the cause of death is often not correctly identified. Due to the fact that geodynamically active areas can release geogenic gases for millions of years over wide areas, it is important to realistically estimate potential risks. The present work produced a first catalogue of the geogenic gas manifestations of the whole Greek territory including relevant literature data. A preliminary estimation of the correlated risk 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 are likely due to exposure to geogenic gases (specifically CO2). This would give a risk of 1.3 x 10(-8) fatality from geogenic gas manifestations per annum. This value, although probably underestimated, is much lower than most other natural or anthropogenic risks.