Health impact of natural gas emission at Cava dei Selci residential zone (metropolitan city of Rome, Italy).

Natural gas hazard was assessed at Cava dei Selci, a residential neighbourhood of Marino (Rome) by a joint study of gas emissions and related health problems. Here a densely urbanized zone with 4000 residents surrounds a dangerous natural gas discharge where, along the years, dozens of animals were killed by the gas. Gas originates from Colli Albani volcano and consists mostly of CO 2 with ~ 1 vol% of H 2 S. In recent years, several gas-related accidents occurred in the urbanized zone (gas blowouts and road collapses). Some houses were evacuated because of hazardous indoor air gas concentration. Gas hazard was assessed by soil CO 2 flux and concentration surveys and indoor and outdoor air CO 2 and H 2 S concentration measurements. Open fields and house gardens release a high quantity of CO 2 (32.23 tonnes * day -1 ). Inside most houses, CO 2 air concentration exceeds 0.1 vol%, the acceptable long-term exposure range. In several houses both CO 2 and H 2 S exceed the IDLH level (Immediately Dangerous to Life and Health). An epidemiological cohort study was carried out on the residents of two Cava dei Selci zones with high (zone A) and medium (zone B) gas hazard exposure, using the rest of Marino as reference zone. We found excess mortality and emergency room visits (ERV) related to high exposure to CO 2 and H 2 S; in particular, an increased risk of mortality and ERV for diseases of central nervous system (HR 1.57, 95% CI 0.76-3.25 and HR 5.82, 95% CI 1.27-26.56, respectively) was found among men living in zone A.