Mortality among workers in the geothermal power plants at Larderello, Italy

Background: Since the early 1990s, various European electricity companies have set up a research program, named EURELEX, devoted to the development of a comprehensive and validated title-occupation -job-exposure matrix (i.e., an instrument to assess exposures from occupations and jobs), in order to estimate and quantify past exposure to a number of potentially carcinogenic agents plus a few selected other toxic substances. The EURELEX program was first applied in Italy to a cohort of geothermal workers in Larderello, Tuscany. Methods: The cohort mortality study comprised 4,237 men who had worked at the geothermal power plant between 1950 and 1990. Vital status and death certificates were obtained from registration offices in the municipality of birth or death. Particular attention was paid to neoplastic effects of exposure to asbestos, largely used in the past for pipeline insulating purposes. The matrix allowed the workers to be subdivided into several categories according to estimated asbestos exposure. Smoking information was not available. Results: No excess mortality was found for all causes and total cancer mortality. A small excess of pleural cancer (2 obs. vs 1.4 exp.) was not statistically significant. The effect of other agents included in the matrix was also examined: the small excess of leukemia among those exposed to solvents prior to 1963 (year of benzene ban in Italy) did not reach the level of statistical significance. No cases of leukemia were found among the workers presumed to have been exposed to important ELF electromagnetic fields. Conclusion: The study provides reassuring information on a large cohort of a unique geothermal power plant since no significant excess mortality for asbestos related cancers was observed. Furthermore, it represents a useful application and validation of a comprehensive job- exposure matrix for the electric industry in Europe.