Assessment of the Health and Ecological Risk of Flame Retardants in Sediment and E-waste along the Warri River/Creeks in Delta State, Nigeria

Abstract

Polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants widely used as flame retardants in electronic materials, with increasing environmental relevance due to their release from informal electronic waste (e-waste) recycling activities. This study assessed the occurrence, spatial distribution, and ecological risk of selected PBDE congeners in electronic waste materials and surface sediments along the Warri River and its associated creeks in Delta State, Nigeria. Electronic waste samples and surface sediments (0–5 cm) were collected from ten locations representing gradients of anthropogenic activity, and analyzed using gas chromatography–mass spectrometry following Soxhlet extraction and silica gel clean-up. Total PBDE concentrations (ΣPBDE) in e-waste ranged from 0.017 to 11.250 mg/kg, with the highest levels recorded at Efieki Edumurhe, indicating a major emission hotspot associated with informal dismantling activities. Sediment concentrations ranged from 0.009 to 2.635 mg/kg, with Udu Bridge identified as the principal depositional sink, reflecting hydrodynamic redistribution of particulate-bound contaminants. Congener profiles showed dominance of mid-brominated PBDEs in e-waste and higher brominated congeners in sediments, suggesting combined effects of legacy inputs, selective partitioning, and environmental transformation processes. Comparative analysis revealed clear source–sink decoupling, with downstream accumulation occurring independently of local emission intensity. Ecological risk assessment using the risk quotient approach indicated high to very high risk levels at several locations, particularly Udu Bridge and Ekpan Bridge, highlighting potential adverse effects on benthic organisms and aquatic ecosystem function. The findings demonstrate that informal e-waste handling significantly contributes to PBDE contamination and that sediment systems act as long-term sinks and secondary sources, with implications for ecological stability and potential human exposure through aquatic food webs.