Tracing the Legacy of Gold Mining: Comparative Insights into Water Contamination and Human Health Risks in Italy and Portugal

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The long-term environmental legacy of historical gold mining continues to pose significant concerns about water quality and human health. This study evaluates and compares the impacts of former gold mines on groundwater (GW) and surface water (SW) quality, and the associated human health risks, at the Crocette/Pestarena mining district (Italy) and the Jales mine (Portugal), characterized by different post-closure conditions. Hydrochemical data from three sampling campaigns in Italy and a single campaign in Portugal were integrated with pollution indices (Heavy Metal Pollution Index, HPI; Heavy Metal Evaluation Index, HEI; and Water Pollution Index, WPI) and a Human Health Risk Assessment (HHRA) under different exposure scenarios. Arsenic was identified as the main contaminant, exceeding drinking water standards in 75% of the Italian and 53% of the Portuguese samples. Exceedances were also recorded for Al, Cd, Fe, Mn, Ni and Pb. The pollution indices identified localized GW pollution downstream of the tailings in Italy, whereas more diffuse pollution, affecting both GW and SW, was observed downstream of the tailings and the passive water treatment system in Portugal. The HHRA revealed unacceptable non-carcinogenic and carcinogenic risks for GW ingestion in both study areas, primarily driven by As. In contrast, risks associated with recreational exposure to SW through ingestion and dermal contact remained within acceptable thresholds. These findings highlight the importance of long-term monitoring and effective intervention strategies to manage water resources in areas persistently impacted by former mining activities.