E-waste-derived microplastics and metals: Challenges, mechanisms, and sustainable mitigation strategies

Abstract

This review focuses on the impact of microplastics (MPs) and metals as two of the common co-pollutants of e-waste and how these are a concern in the terrestrial environment when encountered in recycling areas. Quantitative data indicate that contamination is severe. It has been reported that soils reached 34,100 MPs kg⁻¹ with metal levels 800 times above background, and Pb concentrations reached 3130 mg kg⁻¹, which lowered microbial activity and promoted phytotoxicity. In addition, the metals are deposited on the surfaces of the MPs, which are made of, e.g., polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polycarbonate (PC), thus serving them as a medium. This interplay creates a synergistic threat; MPs act as vectors that enhance metal bioavailability and transport, thereby amplifying ecological and human health risks beyond those of the contaminants alone. The presence and interaction of MPs and metals are determined by the properties of the polymer surface, soil pH, salinity, and organic matter. The most typical detection procedures are of metals encompassing acid digestion (HNO₃, HCl, H₂SO₄) and for MPs, density separation with ZnCl₂ or NaI without standardized terrestrial procedures. Experimental mitigation strategies, including electrocoagulation (>99 % of MP removal from wastewater), magnetic nanoparticle adsorption, and biochar or micro-based remediation, are alternative routes to scalable remediation. Despite these advances, a critical regulatory gap persists: no existing policies or frameworks specifically address the combined threat of MP-metal co-contamination in e-waste-polluted soils. Multidisciplinary and site-specific research is essential to indicate toxicity and permit effective toxicity remediation policies.