Heavy Metal Analysis and Consumer Risk Assessment from Common Carp (Cyprinus carpio L.) Bioaccumulation in Lake Dambal, Ethiopia.

Abstract

Heavy metals are accumulated in fish by absorption from aquatic ecosystems via their gills or skin, as well as consumption of contaminated particles and food. This cause adverse health effects on the consumers via fish intake. The aim of this study was, therefore, to investigate some heavy metal level in water and fish tissue, bioaccumulation level, and consumer risk assessment from Common carp (Cyprinus carpio L.) consumption in Lake Dambal, Ethiopia. A cross sectional-based experimental research design was used to collect the primary data from water and fish samples taken from the selected sites. Three sampling sites were randomly selected from different parts of the lake following the pollution level of the area. Nine liters of water samples and 27 different-sized Common carp were collected from the three sampling sites in the dry season (February-April 2023) for heavy metal content analysis in water and fish. Samples were transported to the Oromia Environmental Protection Laboratory Center after being kept in an ice box at 4oC. The heavy metals were analyzed using an ICP-OES spectrophotometer. The Bioaccumulation Factor (BAF), Estimated Weekly Intake (EWI), Target Hazard Quotient (THQ), Hazard Index (HI), and Carcinogenic Risk (CR) of the heavy metals were also assessed. Fe, Cu, Zn, Pb, and Cr were the heavy metals identified from the samples. The mean concentration of Fe, Cu, Zn, Pb, and Cr were 13.17+15.58, 0.076+0.01, 0.20+0.12, 0.09+0.04 and 0.012+0.01 mg/L in the water samples, respectively. It was also 4.72±1.49, 0.131±0.03, 2.62±0.30, 2.68±0.19 and 0.04±0.03 mg/kg in the fish tissue, whereas it was 14.90±14.15, 8.95±7.22, 0.12±0.12, 0.48±0.36 and 0.04±0.06 mg/kg in the fish liver, respectively. The mean concentrations of heavy metals in the water, fish tissue and liver were in descending order: Fe>Zn>Pb>Cu>Cr. The result also showed a significant difference in heavy metal concentration among the study sites (p<0.05). Except for Pb, which was highest in fish tissue, all the heavy metal concentrations in the water fish tissue were highest in Site 1. In other words, except for Zn, the highest content in the liver was recorded in Site 2. The highest heavy metals in both edible tissue and liver were recorded in large fish (p<0.05). In all cases, Pb content was higher than the maximum permissible limit. The BAF of all heavy metals in fish muscle and liver showed an increasing trend with an increase in fish size with an order of Zn>Pb>Fe >Cr >C. The highest BAF of most metals was recorded in the liver. The highest BAF factor of Cu, Zn, Cr, and Pb in fish muscle and liver was observed in Site 3 and Site 2, respectively. The BAF of Zn, Pb, and Cr in the muscles and liver of fish were above one, indicating bioaccumulation. Similarly, the highest EWI of Fe (0.129) and Pb (0.093) were recorded in Site 2 and Site 3, respectively, but EWI of Cu (0.005), Zn (0.086) and Cr (0.002) were highest in Site 1. The EWI of heavy metals was lower than the recommended daily intake (RDI) value. THQ and HI were highest in females. Similarly, the TQH of Fe, Cu, Zn, and Pb was highest in children. The THQ of all heavy metals was less than one in males and females. Pb and Cr have carcinogenic risk values ranging from 6.8x10-4 -7.86x10-4 and 4.03x10-4 -1.14x10-3 , respectively, indicating that they are within the acceptable range (10–6 to 10–4 ). Generally, the result indicates that fish consumption is not at risk today, except for the Pb, which was above the permissible limit, but indicates bioaccumulation, which could be a health risk if the pollution is not managed. Therefore, effective pollution source management and follow-up are critical for the long-term health of consumers.