Evaluation of microplastics and selected heavy metal contaminants in water and selected fish species from Lake Victoria, Uganda

Abstract

This study evaluated the presence, source and characteristics of MPs and HMs (Lead, Cadmium, Chromium, and Copper) in water and their bioaccumulation status in three commercial fish species of C. gariepinus, L. niloticus, and O. niloticus and from three landing sites of Wairaka, Katosi, and Portbell on the shores of Lake Victoria, Uganda. Human health risks from exposure to microplastics and heavy metal contaminants in water and fish were assessed. Conductivity, temperature, pH, and total dissolved solids in water samples were recorded using a portable pH/Temp/Cond/TDS meter. Fish length was measured with a tape measure, and wet weights were recorded using an analytical balance. Microscopic analysis of MPs was done using a stereospecific microscope. MP identity verification was done using an ATR-FTIR Spectrometer whereas HM analysis was done using an AAS. In water, Pb had the highest concentration observed at Wairaka site (1.46±0.11 ppm). Within the fish varieties, O. niloticus had the highest concentration of copper (0.31±0.36 ppm) at the Katosi site. MP abundance and types varied, with fibres, films, and microbeads being the predominant morphotypes which were mainly HDPE, PE or PVC type. In water, the highest number of microplastics was in Wairaka, followed by Portbell and Katosi with 30±0.63, 20±0.32, and 14±0.41 particles per litre respectively. In fish, O. niloticus had the highest microplastic concentrations in all the three species (24±1.36 particles per kg). The overall target hazard quotient values were less than 1, which suggests that there is no significant health risk linked with the intake of heavy metals through consuming water and fish or through direct skin contact. Total CR results were above 1×10-6 but below 1 ×10-4. There is no evidence to suggest that consuming water and fish or coming into contact with water containing the specified heavy metal pollutants poses any risk of getting cancer