Persistent Organochlorine Compounds Levels in Selected Fish Species from Lake Victoria and Associated Human Health Risks

Abstract

Nile perch (<i>L. niloticus </i>) and Nile tilapia (<i>O. niloticus</i>) 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 <i>L. niloticus</i> and <i>O. niloticus</i> respectively. HCB levels ranged from <0.18 to 0.59µg/kg in <i>L. niloticus</i> and <0.18µg/kg in <i>O. niloticus</i>. Aldrin ranged from <0.14 to 0.34µg/kg in <i>L. niloticus</i> whereas it was not detected in <i>O. niloticus</i>. Moreover, Dieldrin residues ranged from <0.17 to 1.06µg/kg in <i>O. niloticus</i> but were not detected in <i>L. niloticus</i>. Generally, there were slightly higher levels of the detected OCPs in <i>L. niloticus</i> than the corresponding levels in <i>O. niloticus</i> 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.