Copper Compounds: A Narrative and Regulatory Review of Agricultural Uses, Risks, and Environmental Assessment

Background: Copper is a trace element involved in key physiological and biochemical processes in humans, animals, and plants, and its homeostasis is tightly regulated. However, excessive exposure may cause adverse health and environmental effects. Copper-based plant protection products contribute to dietary exposure to copper and remain indispensable for the control of several crop diseases. Methods: This review summarizes the current state scientific and regulatory evidence on agricultural copper, identifies major knowledge gaps, and discusses strategies to support its sustainable use. A structured literature review was conducted using the PECO framework to define eligibility criteria, while key principles of the PRISMA 2020 statement were applied to improve the transparency of study identification and selection. Results: The available evidence confirms the dual role of copper as an essential micronutrient and a potentially toxic element, with adverse effects depending on exposure level, chemical form, bioavailability, and physiological status. Although copper remains an effective agricultural tool, long-term use may promote soil accumulation and environmental impacts. Current environmental risk assessment frameworks, originally developed for organic chemicals, do not fully account for the environmental behavior of inorganic metals. The review also examines copper occurrence, biological functions, agricultural uses, environmental fate, toxicity, and regulatory frameworks. Conclusions: Sustainable copper use requires balancing crop protection benefits with human health and environmental protection. Dietary exposure from authorized copper-based PPPs is generally considered negligible according to current EFSA PRIMo assessments, whereas occupational exposure and environmental accumulation remain important concerns. Future environmental risk assessment frameworks should better account for the environmental fate, natural background concentrations, bioavailability, and speciation of inorganic metals such as copper, thereby improving the scientific basis of regulatory decision-making.