HUMAN HEALTH RISKS ASSESSMENT OF POLYBROMINATED DIPHENYL ETHERS IN FLOODPLAIN SOILS OF THE LOWER REACHES OF RIVER NIGER.

Abstract

The concentrations of the 39 PCBDs in the floodplain soils of the lower reaches of River Niger, Nigeria, were

determined with the aim of providing information on the contamination level, sources, and ecological and

human health risks in the soils. Soil samples were collected from thirteen (13) different locations and three

depths along the floodplain. Soil samples were soxhlet extracted using dichloromethane (DCM)/n-Hexane and

purified with florisil and silica gel column. The PCBDs were quantified using a gas chromatography-mass

spectrometry. Similarly, the average concentrations of Ʃ39 PBDEs in soils of 15-30cm depth were higher than

that of 0-15cm and 30-45cm. The 15-30cm and 30-45cm depths of FP12 and 15-30cm depth of FP13 have

higher concentrations (1297ng/g

-1

, 1226ng/g

-1 and 1169ng/g

-1

respectively) relative to other samples. On

average, the concentration of ∑39 PBDEs in the downstream section (FP9 to FP13) was higher than those in

the upstream (FP1 to FP5) and midstream section (FP6 to FP8) of the study area. The total cancer risk values

associated with these pollutants in the floodplain soils were higher than the potentially acceptable target risk

value of 10

-6

set by the US EPA signifying a high potential human carcinogenic risk in the floodplain soil of

LRRN. Based on the Principal component analysis and diagnostic source ratios, the major sources of metals

in these soils include industrial emissions, use of agrochemicals, and traffic emissions as well as the drilling

and production activities of the oil and gas industries. The PBDEsD could be from atmospheric deposition and

long range transport process as well as component of electrical transformers and those emitted during burning

of electronic wastes. The PBDEs could be from both fresh and historical inputs; PBDEs could be from technical

mixture used for paints, plastics, hydraulic fluids, dielectric insulating fluids for transformers, and capacitors;