Occurrence and Health Implications of Heavy Metals in Microplastics from Otuoke Surface Waters

Microplastics (MPs) have become ubiquitous contaminants in aquatic environments, raising increasing concern due to their ability to adsorb and transport toxic heavy metals. These small synthetic polymer particles (<5 mm) originate from diverse anthropogenic sources, including industrial effluents, municipal wastewater, and the degradation of plastic waste. Owing to their hydrophobic surfaces and large surface-area-to-volume ratio, MPs readily bind heavy metals such as cadmium, copper, chromium, iron, manganese, nickel, lead, and mercury, thereby enhancing metal persistence, mobility, and bioavailability in aquatic ecosystems. The association of heavy metals with MPs poses serious environmental and public health risks, as these complexes may be ingested by aquatic organisms and transferred through food webs, ultimately exposing human populations.This study investigates the occurrence of heavy metals adsorbed onto microplastics in the surface waters of the Otuoke River, South-South Nigeria, and evaluates the potential human health risks associated with their exposure. Surface water samples were analyzed to identify and quantify MPs and associated heavy metal concentrations, followed by health risk assessment using established exposure and toxicity models. The findings provide insight into the extent of metal contamination mediated by MPs and highlight potential risks to local communities that depend on the river for domestic, agricultural, and fishing activities. The results contribute region-specific data to the growing body of literature on microplastic pollution and serve as a scientific basis for environmental monitoring, public health protection, and pollution mitigation strategies in the Niger Delta region.