Nile perch (L. niloticus) and Nile tilapia (O. niloticus) are the major commercial fish species in Lake Victoria region of Tanzania. This study was conducted to assess the levels of persistent organochlorine compounds, namely PCBs and OCPs in these two fish species and the probable human health risks associated with the consumption of these two fish species from Lake Victoria. Fish samples were collected between May and August 2016 and the necessary anthropometric measurements such as length and weight were taken. The extraction was done using a modified QuEChERS method and the identification and quantification of the chemicals were done using GC/ECDs. The results of this study revealed that fish species sampled were undersize, which was an indication of overfishing and abuse of bylaws. Among the 19 OCPs which were considered, only four (β-HCH, HCB, Aldrin and Dieldrin) were detected at measurable quantities. β-HCH ranged from <0.24 to 1.19µg/kg. The mean concentrations were 0.77±0.43µg/kg and 0.56±0.16µg/kg for L. niloticus and O. niloticus respectively. HCB levels ranged from <0.18 to 0.59µg/kg in L. niloticus and <0.18µg/kg in O. niloticus. Aldrin ranged from <0.14 to 0.34µg/kg in L. niloticus whereas it was not detected in O. niloticus. Moreover, Dieldrin residues ranged from <0.17 to 1.06µg/kg in O. niloticus but were not detected in L. niloticus. Generally, there were slightly higher levels of the detected OCPs in L. niloticus than the corresponding levels in O. niloticus mainly due to their differences in trophic levels and feeding habits. The indicator PCBs were not detected in all the investigated fish samples. The levels of all the detected organochlorines were far below the MRL set for fish and fishery products suggesting that the fresh fish from Lake Victoria are safe for human consumption. Low levels of the detected residues and non-detection of many organochlorines considered indicate that contamination in Lake Victoria has not reached alarming levels. The human health risk assessment of the detected organochlorines showed cancer risk from 8.6E-06 to 3.2E-05 for children and from 7.8E-06 to 1.3E-05 for adults indicating that there is a low cancer risk for both age groups. The non-cancer risks (HI) on the other hand, were 5.7E-02 for children and 4.7E-02 for adults, which is an indication of an insignificant risk.

A study was conducted in Lake Victoria to assess the occurrence, levels and risks of indicator polychlorinated biphenyls (PCBs) in four processed Lates niloticus (L.) products (salted-sundried, trims, smoked and deep-fried). Samples extractions were done using QuEChERS method while detection and quantification of congeners was done using a GC-ECD and GC-MS. Six PCBs (CB 28, CB 52, CB 118, CB 138, CB 153 and CB 180) were detected at measurable quantities in fish products. The PCBs; CB 138, CB 153 and CB 180 dominated the loading due to their structures and high degree of chlorination. However, the mean concentration of ΣPCBs in this study were below MRL of 75 µg/kg set for fish by European Commission, implying that the fish products were safe for human consumption in regard to indicator PCBs. Similarly, indicator PCBs, CB 138, CB 153 and CB 180 were more prevalent (20 to 80%) in all fish products than other congeners. For both adults and children the cancer risks were low-to-moderate (ranging from 2.0E-04 to 3.0E-04 for adults and 2.0E-04 to 1.0E-03 for children) while the non-cancer risks were insignificant as the Hazard Indices were less than one.

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This study assessed the health risks of organochlorine pesticides in fish products from Lake Victoria. Nine organochlorine pesticides (α-Hexachlorocyclohexane (HCH), β-HCH, γ-HCH (Lindane), Hexachlorobenze (HCB), Dieldrin, p, pꞌ-DDE, αendosulfan, Oxychlordane and αchlordane) were identified at variable levels in fish products. Of the nine organochlorine pesticides which were identified, p, pꞌ-DDE (3.73µg/kg) was the highest in deep fried Nile tilapia while the lowest amount was α-HCH (0.14 µg/kg) in smoked Nile tilapia. In the smoked products, several of the organochlorine pesticides were detected at high concentrations. This is attributed to the fact that organochlorine pesticides are fat soluble and therefore found in the lipid phase of the fish during smoking. There were high levels and prevalence of p, pꞌ-DDE, αendosulfan, HCB, Dieldrin and Lindane in deep fried Nile tilapia compared to other fish products probably due to environmental contamination. However, the levels of organochlorine pesticides in this study are below the maximum residual limits (MRLs) set by FAO/WHO for fish products indicating that the fish products were safe for human consumption and do not present health risks in terms of organochlorine pesticides residues.