Assessing the health risks of natural CO2 seeps in Italy

Industrialized societies which continue to use fossil fuel energy sources are considering adoption of Carbon Capture and Storage (CCS) technology to meet carbon emission reduction targets. Deep geological storage of CO(2) onshore faces opposition regarding potential health effects of CO(2) leakage from storage sites. There is no experience of commercial scale CCS with which to verify predicted risks of engineered storage failure. Studying risk from natural CO(2) seeps can guide assessment of potential health risks from leaking onshore CO(2) stores. Italy and Sicily are regions of intense natural CO(2) degassing from surface seeps. These seeps exhibit a variety of expressions, characteristics (e.g., temperature/flux), and location environments. Here we quantify historical fatalities from CO(2) poisoning using a database of 286 natural CO(2) seeps in Italy and Sicily. We find that risk of human death is strongly influenced by seep surface expression, local conditions (e.g., topography and wind speed), CO(2) flux, and human behavior. Risk of accidental human death from these CO(2) seeps is calculated to be 10-8 year-1 to the exposed population. This value is significantly lower than that of many socially accepted risks. Seepage from future storage sites is modeled to be less that Italian natural flux rates. With appropriate hazard management, health risks from unplanned seepage at onshore storage sites can be adequately minimized.