Persistent organic pollutants (POPs) and per- and polyfluoroalkyl substances (PFASs) in liver from wild and farmed tilapia (Oreochromis niloticus) from Lake Kariba, Zambia: Levels and geographic trends and considerations in relation to environmental quality standards (EQSs)

The current study was carried out to investigate a wide variety of persistent organic pollutants (POPs) in wild and farmed tilapia (Oreochromis niloticus) in Lake Kariba, Zambia, and assess levels of POPs in relation to Environmental Quality Standards (EQSs). Concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyls (PBDEs), and perfluoroalkyl substances (PFASs) were determined in liver samples of tilapia. PFASs compounds PFOS, PFDA and PFNA were only detected in wild fish, with the highest median PFOS levels in site 1 (0.66 ng/g ww). Concentrations of POPs were in general highest in wild tilapia. The highest median n-ary sumation DDTs (93 and 81 ng/g lw) were found in wild tilapia from sites 1 and 2, respectively 165 km and 100 km west of the fish farms. Lower DDE/DDT ratios in sites 1 and 3 may indicate relatively recent exposure to DDT. The highest median of n-ary sumation 17PCBs (3.2 ng/g lw) and n-ary sumation 10PBDEs (8.1 ng/g lw) were found in wild tilapia from sites 1 and 2, respectively. The dominating PCB congeners were PCB-118,-138,-153 and-180 and for PBDEs, BDE-47,-154, and-209. In 78% of wild fish and 8% of farmed fish n-ary sumation 6PBDE concentrations were above EQSbiota limits set by the EU. This warrants further studies.

Automated summary

The current study investigated the levels of persistent organic pollutants (POPs) in wild and farmed tilapia in Lake Kariba, Zambia, and assessed their levels in relation to Environmental Quality Standards (EQSs). Organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyls (PBDEs), and perfluoroalkyl substances (PFASs) were detected in liver samples of tilapia. Higher concentrations of POPs were generally found in wild tilapia, and specific POPs compounds were only detected in wild fish. The study also found that some of the POPs concentrations exceeded EQSbiota limits set by the EU, indicating the need for further studies.