Persistent organochlorine pollutants in Lake Bosomtwi and Weija Lake and their potential toxicological health implications
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Date
March, 2015.
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Abstract
This research work focused on the assessment of organochlorine pollutants in two water bodies and
their health implications on aquatic species and humans. The research involved conducting
systematic assessment of occurrence and burden of indicator polychlorinated biphenyls and
organochlorine pesticides in water, sediment and fish samples.The main objective focused on the
determination of persistent organochlorine pollutants as well as their bioaccumulation in fish species
and their toxicological risk assessment on human population via drinking of water and dietary intake
of fishes from the two water bodies. Lake Bosomtwi and Weija Lake were the study areas and
investigations started from January 2012 to June 2014. Instrumental Neutron Activation Analysis
(INAA) was used for determination of extractable organochlorines (EOCs) and bound
organochlorines (BOCs). The EOCs were further characterized with Capillary Gas Chromatography
equipped with Electron Capture Detector (GC - ECD). Hexane was used as extraction solvent for the
extraction of OC pollutants from the water samples whiles, the sediment and fish samples were
sonicated on ultrasonic bath using hexane/acetone (3:1) solvent system. The extracts were then
cleaned up on a combined florisil-silica adsorbent packed in glass column. Ecotoxicological impact
of sediments on aquatic species was assessed using two sediment quality guidelines. The impacts of
OC pollution on humans was assessed by estimating daily exposure and cancer and non cancer
hazard ratios on consumption of the studied fishes. ANOVA was applied to determine the
differences in the mean concentration. The average levels of extractable organochlorine were 0.71
mg/L and 0.39 mg/L for the water samples from the Weija and Bosomtwi respectively. The sediment
compartments had average extractable organochlorine content of 3.57 mg/kg from the Weija while
that from Bosomtwi was 3.28 mg/kg. The average BOC content in the sediments were respectively,
0.48 mg/kg and 0.46 mg/kg for Weija and Bosomtwi samples. In the fish compartments, EOC
composition varied from 6.89 mg/kg to 9.02 mg/kg for Weija species while those from Bosomtwi
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were from 3.99 mg/kg to 4.63 mg/kg. The concentrations range for the detected organochlorine
pesticides (OCPs) were <0.01 µg/l to 4.30 µg/l, <0.01 µg/kg to 15.23 µg/kg, <0.01 µg/kg to 23.70
µg/kg for the water, sediment and fish samples respectively, while those for the PCBs were <0.01
µg/l to 4.72 µg/l for Lake water, <0.01 µg/kg to 7.55 µg/kg for sediments and <0.01 µg/kg to 32.40
µg/kg for the fish species. Statistically significant differences in the mean concentrations of the OCs
were detected. The ecotoxicological impacts of measured organochlorine pollutants in the sediments
to aquatic species showed that toxicity of ƩPCB, p,p'-DDT, P,P'-DDE and ƩDDT to aquatic species
was below ERL Estimated daily intake (EDI) of organochlorine as a result of consumption of the
studied fishes for children ranged from 0.002 µg/kg to 0.176 µg/kg and those for adults were from
0.0011 µg/kg to 0.0892 µg/kg. EDIs were however, far below reference doses (RFDs) recommended
by United State Environmental Protection Agency (USEPA). Risk assessment in terms of
carcinogenic and non-carcinogenic effects on humans on consumption of the fishes revealed that
eating of Tilapia zilli, Tilapia nile and Tilapia galilaea from the Weija Lake present no risk of
carcinogenic effect. However, more than one in a million of the consuming population on eating
Clarias gariepinus can get cancer as a result of HCHs contamination. Consumption of fishes from
the Lake Bosomtwi was found to present no carcinogenic effect. In general, the overall findings
showed that levels of pollutants detected in the two water bodies posed minimum to no risk to
communities that depend on the Lakes for livelihood.
Description
A thesis presented to the Department Of Chemistry, College Of Science, in partial fulfilment of the requirements for the award Of Doctor of Philosophy degree in Environmental Chemistry, 2015