Sources and risk evaluation of polybrominated diphenyl ethers in dust and soil from an urban environment in Nigeria

Environmental context Polybrominated diphenyl ethers (PBDEs) are compounds that have previously been widely applied in many consumer and commercial products; their use is banned because of their toxicity but they remain a legacy environmental pollutant. This study provides concentrations of PBDEs in indoor and outdoor dust and soils. Relationships between their occurrence patterns and origins are established, which informs our understanding of threats to human health from soil and air exposure. Rationale The concentrations of 39 polybrominated diphenyl ether (PBDE) congeners were determined in soil and dust samples of a typical Nigerian city in order to evaluate the spatial patterns, sources, and ecosystem and human health risks. The findings afford the necessary data to evaluate the temporal status, determine compliance with globally banned persistent organic pollutants, and provide guidance for designing strategies for surveillance, source control, risk reduction and management of environmental quality. Methodology Samples of soil and dust (indoor and outdoor) were obtained from 20 sites within the city. The soil and dust samples were subjected to Soxhlet extraction with an acetone/DCM/n-hexane mixture and cleaned up. The PBDEs in the extracts were separated and quantified by gas chromatography–mass spectrometry. Results The Σ39 PBDE concentrations of these samples varied between 1.69 and 590 ng g−1 for soil, whereas those of indoor and outdoor dust ranged from 0.45 to 112 and 0.54 to 60.4 ng g−1 respectively. Discussion Despite PBDEs being primarily indoor pollutants, their concentrations in soils exceeded those detected in indoor and outdoor dust, which may be attributed to soil’s higher sorption capacity and anthropogenic activities. The composition patterns in these media showed dominance of penta-BDEs, and exposure to these penta-BDEs has potential ecological consequences. The occurrence patterns and potential sources of PBDEs in soil and dust were evaluated using principal component analysis (PCA) and hierarchical cluster analysis (HCA). The behaviours and sources of PBDEs in soil and outdoor dust were similar, but differ from those of indoor dust. The use of the penta-BDE technical formulation is the likely source of PBDEs in these matrices. Exposure to PBDEs in soils and dust from this area poses no serious health risk but could pose an ecological risk. Despite the low concentrations of PBDEs in these media, there is a need for continued surveillance and the implementation of regulatory frameworks for the control of these persistent pollutants.