Cadmium: a global assessment of mineral resources, extraction, and indicators of mine toxicity potential

Mostly produced as a by-product of zinc (Zn) mining, cadmium (Cd) is used in solar photovoltaic cells, battery storage, alloys, pigments, plating, and in nuclear reactors. However, it is also a regulated toxic substance with a long history of environmental and health impacts. As the mining of both Zn and Cd will need to increase to support the global energy transition, the status of Cd as either a resource or a pollutant has major implications for global supply chains and environmental management. Here, we present a new global, site-specific database and analysis of Cd resources in Zn-bearing mineral deposits and mines. Our database, which exceeds past Cd studies in scope, transparency and replicability is made available in full to support future assessments of Cd and Zn resources, mine production and associated risks. It includes 927 sites subject to detailed geological data compilation and analysis. Collectively, these sites suggest a new global resource estimate of 3.3 Mt Cd (95% confidence interval: 2.7-6.1 Mt). A preliminary geospatial analysis of sites in our database and mine toxicity indicators was also conducted. It shows that: - A human population of approximately 3.27 million live within 10 km of sites containing Cd resources, - similar to 31% of the world's Cd resources sit within 20 km of International Union for the Conservation of Nature protected areas, and - Some 28% of Cd mobilised annually by mining originates from areas hosting seasonal or permanent surface water cover. As similar to 27% of Cd resources are in countries that do not refine it, our study highlights the need for further research exploring global Cd trade flows and associated emissions. Heavy metal pollution in mining and metal production regions is an ongoing challenge, and our global dataset refines our understanding of its magnitude and distribution.