Assessment of levels of heavy metals in small pelagic fish species: A case study of Encrasicholina punctifer and Rastrelliger kanagurta in Dar es Salaam Coast, Tanzania
Assessment of levels of heavy metals in small pelagic fish species: A case study of Encrasicholina punctifer and Rastrelliger kanagurta in Dar es Salaam Coast, Tanzania
This study aimed to assess the concentration of Arsenic, Cadmium, Chromium, Lead, Mercury, Methylmercury, Nickel, Copper, Iron, and Zinc in Encrasicholina punctifer and Rastrelliger kanagurta from the Dar es Salaam coast. The samples were prepared digested accordingly and analysed using 4210 MP AES for As, Cd, Cr, Pb, Ni, Fe, Cu, and Zn while DMA-80 was used for Hg and MeHg.
Concentrations of Cu, Fe, Zn, Pb, Hg and MeHg estimated for E.punctifer at Kunduchi fish market (1.179-3.174 mg kg-1, 6.787-19.771 mg kg-1, 12.568 -20.624 mg kg-1, 0.35-1.533 mg kg-1, 0.035-0.049 ng kg-1, and 0.036-0.058 ng kg-1) and from Ferry fish market (1.117-2.181mg kg-1, 3.821-6.492 mg kg-1, 7.406-10.261mg kg-1, 0.124-1.418 mg kg-1 , 0.031-0.042ng kg-1 and 0.030-0.040 ng kg-1) while for R. kanagurta from Kunduchi fish market (0.978-3.942 mg kg-1, 3.868-16.262mg kg-1, 2.796-14.397mg kg-1, 0.481-1.435mg kg-1, 0.033-0.05ng kg-1 and 0.03-0.046 ng kg-1) and at Ferry fish market (1.159-3.191mg kg-1, 4.343-14.463 mg kg-1, 0.613-6.583 mg kg-1, 0.225-1.934 mg kg-1, 0.039-0.066 ng kg-1 and 0.034-0.056 ng kg-1) were recorded. R. kanagurta and E.punctifer showed highest levels of Zn and Fe in samples from both sites.
The results indicate that Pb was slightly higher than the recommended limits for human consumption whereas the rest were far below the set limits by international organizations. As, Cd,Cr and Ni were not detected for all the samples in this study.
EDI, THQ and HI were calculated to assess the human health risks that can be posed by the detected heavy metals. The results showed all EDI values below the maximum tolerable limits (MTL) for heavy metals. THQ and HI values were within the tolerable ranges with calculated values of less than 1. In general, the concentrations of heavy metals in all the fish samples in this study were below the permissible limits set by the FAO and WHO indicating that the sampled fish species pose no immediate risk to human health.
While the current situation at the research sites looks hazard-free, ongoing monitoring is recommended since pollutants vary with the prevailing circumstances and elements in an ecosystem.