Health effects associated with chronic exposure to low-level hydrogen sulfide from geothermoelectric power plants. A residential cohort study in the geothermal area of Mt. Amiata in Tuscany.

BACKGROUND

Geothermal power plants for the production of electricity are currently active in Mt. Amiata, Italy. The present study aimed to investigate the association between chronic low-level exposure to HS and health outcomes, using a residential cohort study design.

METHODS

Spatial variability of exposure to chronic levels of HS was evaluated using dispersion modelling. Cohorts included people residing in six municipalities of the geothermal district from 01/01/1998 to 31/12/2016. Residence addresses were georeferenced and each subject was matched with HS exposure metrics and socio-economic status available at census tract level. Mortality and hospital discharge data for neoplasms and diseases of the respiratory, central nervous and cardiovascular systems were taken from administrative health databases. Cox proportional hazard models were used to test the association between HS exposure and outcomes, with age as the temporal axis and adjusting for gender, socio-economic status and calendar period.

RESULTS

The residential cohort was composed of 33,804 subjects for a total of 391,002 person-years. Analyses reported risk increases associated with high exposure to HS for respiratory diseases (HR = 1.12 95%CI: 1.00-1.25 for mortality data; HR = 1.02 95%CI: 0.98-1.06 for morbidity data), COPD and disorders of the peripheral nervous system. Neoplasms were negatively associated with increased HS exposure.

CONCLUSIONS

The most consistent findings were reported for respiratory diseases. Associations with increased HS exposure were coherent in both mortality and hospitalization analyses, for both genders, with evidence of exposure-related trends. No positive associations were found for cancer or cardiovascular diseases.