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

Our plain-English summary of Mortality among workers in the geothermal power plants at Larderello, Italy, by E. Pira, M. Turbiglio, M. Maroni, et al (American Journal of Industrial Medicine, 1999).

The study

• Authors: E. Pira, M. Turbiglio, M. Maroni, P. Carrer, C. La Vecchia, E. Negri, R. Iachetta
• Journal: American Journal of Industrial Medicine
• Published: 1999;35(5):536-9
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

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 absestos 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.

In plain English

This retrospective cohort mortality study followed men who worked at least three months at the Larderello geothermal power plant, Tuscany, Italy, between 1950 and 1990. Of 4,237 workers on record, 255 women and 36 untraced men were excluded, leaving 3,946 men. There were 977 deaths over 90,482 man-years. The plants' steam supply ducts were insulated with asbestos. A job-exposure matrix called EURELEX was used to estimate cumulative asbestos exposure, although exposure data were unavailable for some workers. Deaths were compared with Italian national death rates. Overall, 977 deaths occurred against 1,295 expected (SMR 75.4). Lung and laryngeal cancer deaths were below expected. Two pleural cancer deaths occurred against 1.4 expected (SMR 139.3, 95% CI 15.6 to 502.8), which was not statistically significant. Both were in asbestos-exposed workers; one had also been exposed to asbestos before working at the plant. Among solvent-exposed workers, 4 leukaemia deaths occurred against 1.6 expected, which was also not significant. Smoking information was not available. The authors concluded that the study provides reassuring information and is a useful application and validation of the EURELEX matrix.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: retrospective cohort mortality study, with observed deaths compared to deaths expected from Italian national rates (standardized mortality ratios), also corrected using rates for the province of Pisa
• Who was studied: men who worked at least three months at the Larderello geothermal power plant, Tuscany, Italy, between 1 January 1950 and 31 December 1990. 4,237 subjects were on record; 255 women and 36 untraced men were excluded, leaving 3,946 men studied. There were 977 deaths over 90,482 man-years, with follow-up from 1950 to 1990.
• Exposure: asbestos used to insulate the ducts carrying geothermal steam (fiber type not stated). Cumulative exposure was estimated with the EURELEX job-exposure matrix in fibers/l/years and grouped as not exposed, up to 5,000, and more than 5,000 fibers/l/years; exposure data were not available for some workers. Solvent exposure (exposed or not) and extremely low frequency electromagnetic fields were also considered.
• Main results:
  • Whole cohort: 977 deaths observed vs 1,295 expected, SMR 75.4
  • Whole cohort: SMRs below 100 for laryngeal cancer (58.9 in the text; Table I gives 57.9) and lung cancer (68.5)
  • Whole cohort: 2 pleural cancer deaths vs 1.4 expected, SMR 139.3 (95% CI 15.6 to 502.8), not statistically significant
  • Both pleural cancer deaths occurred in asbestos-exposed workers. The SMR was 321 (one case) in the up to 5,000 fibers/l/year category and 994 (one case) in the more than 5,000 fibers/l/year category. Neither estimate was statistically significant.
  • Of the two mesothelioma cases, one also had a history of asbestos exposure before employment at the plant, which was included in the matrix
  • Highest asbestos category: no lung cancer excess (6 observed vs 6.4 expected, SMR 94.0, 95% CI 34.3 to 204.7 in Table II). The authors took this to indicate that asbestos exposure in this cohort must have been modest.
  • Solvent-exposed workers: 4 leukaemia deaths vs 1.6 expected, SMR 242.9 (95% CI 65.3 to 621.9), not statistically significant. All 4 cases had solvent exposure before 1963.
  • None of the leukaemia cases had been exposed to important electromagnetic fields according to their individual activity code
• The authors' conclusion: The authors concluded that the study provides reassuring information on a large cohort from a unique geothermal power plant, since no significant excess mortality from asbestos-related cancers was observed. They also concluded that it is a useful application and validation of the EURELEX job-exposure matrix for the European electricity industry.
• Limitations the authors state:
  • No information was available on tobacco smoking
  • Confidence intervals accounted for random variation in the observed numbers only. For rarer causes of death, random variation in the expected numbers may also matter.
  • Exposure data were not available for some workers
  • For solvents, only exposed or non-exposed status was available, not quantitative levels
  • The leukaemia excess among solvent-exposed workers was far from significant and must be interpreted with caution

Topics

The National Library of Medicine indexes this study under subjects our site covers: Power plants and utilities.

Medical terms in this study, explained in our Lexicon: Carcinogenic, Death Certificate, Statistical Significance.

Related studies

• Malignant mesothelioma in thermoelectric power plant workers in Italy — P. Crosignani, F. Forastiere, et al. (1995)
• Risk of cancer among Danish utility workers--a nationwide cohort study — C. Johansen, J.H. Olsen (1998)
• Mortality in a cohort of cement workers in a plant of Central Italy — F. Giordano, V. Dell'orco, et al. (2012)
• Mortality rates among nuclear industry workers at Lucas Heights Science and Technology Centre — R.R. Habib, S.M. Abdallah, et al. (2005)
• Asbestos related health hazards among power plant workers — Y. Lerman, A. Finkelstein, et al. (1990)
• Extrapulmonary neoplasms among asbestos-exposed power plant workers — I.G. Ron, H. Ron, et al. (1999)

Browse more research in American Journal of Industrial Medicine, or return to medical research.