Abstract
The levels of PCBs in sediments, water, leachate and aquatic fauna ( Tilapia guineensis , Callinectes amnicola and Cardiosoma armatum ) found in and around e-waste dumpsites in Lagos and Osun States, South-West, Nigeria were analyzed using Gas Chromatography Electron Capture Detector (GC ECD) Agilent 7820A. All the 28 PCBs congeners studied were detected with the Σhexa-PCBs dominating in Lagos (21%) while the Σtetra-PCBs (24%) enriched the samples from Osun State. The concentrations of Σ- PCBs in decreasing order were Lagos: sediment ˃ fish gill ˃ fish muscles ˃ water ˃ crab ˃ leachate and Osun: fish gill ˃ fish muscle ˃ sediment ˃ crab ˃ water ˃ leachate. The concentrations of total indicator PCBs ( Σ7PCBs) in the sediment from Lagos (4.19 μg/kg) and Osun (8.58 μg/kg) exceeded the Canadian Sediment Quality standard threshold effect level (CSQ TEL) (0.03 μg/kg) and the National Oceanic Atmospheric Administration threshold effect level (NOAA TEL) for fresh and marine sediments.. The calculated toxic equivalent quotient (TEQ) for fish from Lagos and Osun (3.7 and 4.4) respectively further suggests a likely occurrence of adverse effects to humans who consume the fish. This study reveals the high health and ecological risks associated with e waste pollution in the aquatic environment. Keywords: e-waste, polychlorinated Biphenyls, aquatic environment, leachate
Highlights
Polychlorinated Biphenyls (PCBs) are a class of non-polar toxic chemical compounds consisting of 209 congeners (Adeyemi et al, 2009), out of which only about 130 are found in commercial mixtures
They are detected in a wide range of environmental compartments including biota, soil, water, air, sediment, plants and animal tissue in all regions of the earth. Their reported half-lives in soil and sediment range from months to years. Due to their very low solubility in water and low volatility, most of them are contained in sediments that serve as environmental reservoirs from which they may continue to be released over a long period of time for example, the life expectancy of electrical transformers that contain PCBs is 30 years or more. (Wang and Zhong, 2011)
Exposure to PCBs may enhance the genotoxic activity of similar compounds to cause more severe toxic effects which are explained by the binding of planar PCBs and PCDD/Fs to the aryl hydrocarbon (Ah) receptor (Boalt et al, 2014)
Summary
PCBs are a class of non-polar toxic chemical compounds consisting of 209 congeners (Adeyemi et al, 2009), out of which only about 130 (di- to deca-PCBs) are found in commercial mixtures They are water soluble organic compounds with 1 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings with a chemical formula of C12H10-xClx, where x = 1-10. The core indicator PCBs are the 7 ICES (International Council for the Exploration of the Sea) monitored congeners namely CB-28, CB-52, CB-101, CB-118, CB138, CB-153 and CB-180 (Boalt et al, 2014) They are listed as mandatory contaminants to be analyzed and reported within both the OSPARCOM (Oslo/Paris Convention for Protection of the Marine Environment of the North-East Atlantic (1992) and the HELCOM (Helsinki Commission) Conventions. This study investigated the levels of PCBs in the leachate, water, sediment and some aquatic fauna found in and around e-waste dumpsites as well as assessed the ecological risk posed to the organisms by PCBs contamination
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