Trace elements in water, sediment and commonly consumed fish from a fish farm (NE Zimbabwe) and risk assessments

Abstract

Limited information is available on trace element-water contamination and health risk assessment of small-scale intensive fish farming in low-income settings. Such information creates awareness among fish consumers, policy makers and the scientific community, regarding dietary exposure and health risks for not well-reported settings. The concentrations of potentially toxic trace elements in water, sediment and fish (T. rendalli, O. nitloticus and M. salmoides) were determined by spectrometry. The ecological and potential human health risks were assessed for Magobo dam, NE Zimbabwe, using the Hakanson ecological approach and the United States Environmental Protection Agency risk-assessment model, respectively. Concentrations in water and sediment appeared to increase in the order: cadmium < arsenic < lead. They restricted water use for irrigation and human consumption. The potential ecological risk factors for individual trace elements were below the index range for low risk. The potential ecological risk index for the dam (7.20) did not constitute ecological risk. The concentrations of trace elements in fish significantly varied with species, length and tissue (p < 0.05). The concentrations of arsenic and lead in gills, liver and muscle for O. niloticus and arsenic in M. salmoides were greater than international maximum permissible limits for fish. The target cancer risk due to dietary exposure to arsenic in the three fish species was in the range 10-6. There is no obvious cancer risk to the exposed population.

Impacts of the Residual Trace Metals of Aquaculture in Net Cages on the Quality of Sediment

“…In the Magobo Reservoir, Zimbabwe, Kanda et al [ 50 ] found that all concentrations of toxic trace elements were below the threshold effect-TEL/minimum threshold for freshwater ecosystems, suggesting that there are no obvious adverse biological effects.…”

“…Kanda et al [ 50 ] investigated the ecological risks and potential ecological risks of the Magobo Reservoir, Zimbabwe, and found that the ecological risk was less than 40 and the potential ecological risk was less than 150, and therefore was moderate.…”

“…The application of geochemical and ecotoxicological indices are important tools for the assessment of sediment quality and have been used in research related to the impacts of aquaculture activity on sediments [ 9 , 13 , 17 , 18 , 50 , 51 ].…”

Arsenic Exposure via Contaminated Water and Food Sources

“…For instance, topsoil around abandoned and active gold mines in western Ghana presents As concentrations in the range 1807-8401 mg/Kg, causing significant contamination in a wider area and especially in surface water and groundwater sources [158]. Nigeria Cereals Fish and shellfish 0.001-0.029 0-5.2 [178,190] South Africa Mussels Fish and shellfish 0.82-3.4 0.5-4.5 [191,192] Tanzania Fish 0-5 [193] Zimbabwe Vegetables Fish 0.19-5.8 0.05-0.42 [194,195]…”