Uptake and mobilization trends of heavy metals in various fishes grown in contaminated water bodies and sediment

Abstract

Heavy metals contamination in different environmental segments have become very significant pollution concern in most of the developing countries now-a-days. Rapid expansion of industrialization without having proper plans, excessive use of agrochemicals, and frequent occurrences of natural disasters are the major sources of heavy and toxic metals pollution in environmental ecosystems. Therefore, the present study has investigated the heavy and toxic metals contamination status in different fish species grown in polluted waterbodies in the vicinity of Dhaka Export Processing Zone (DEPZ), which is the fastest growing industrial area in Bangladesh. The fishes, and sediments samples have been digested with the acid mixtures following the standard established procedures and then analyzed for the heavy and toxic metal contamination using the Flame-AAS method. A total of six heavy and toxic metals such as Cr, Cu, Zn, Fe, Pb and Cd have been studied in different parts of various fishes [Ctenopharyngodonidella(Grass carp), Labeorohita (Nola), Heteropneustesfossilis (Shing,jiol), Cyprinuscarpio (Carfu), Puntius gonionotus (Thai Surputi)], sediments, and water samples. Different metal concentrations determined in fishes, sediments, and water samples were compared with standard permissible/tolerable values set up by WHO, USEPA, EU, and other countries. Water pollution indices, sediment quality indices, and metal contamination data in various fish species revealed the severe pollution status in the study area due to the drastic impacts of the emission of toxic complex effluents from different industries located in and around of DEPZ. Average concentrations of different metals in water and sediment were found to be in the order of Fe > Zn > Cu >Pb> Cr > Cd and Fe>Cu>Zn>Cr>Pb>Cd respectively. Heavy metals contents found in waterbodies and sediments exceeded the permissible levels of WHO and USEPA suggesting serious metals pollution to the respective aquatic environment. Different fish species showed variation in the uptake and translocation of heavy metals in their bones and muscles and average metals concentrations analyzed in various fishes followed the order of Zn>Fe >Pb> Cr> Cu> Cd. Evaluation of the mobilization of metals in different organs of various fish bodies revealed the occurrence of the highest accumulation of metals in bones whereas the lowest uptake of the respective metals was observed in the muscles. The ranges of different metals concentrations (mg/kg) in various fishes were as follows- Pb: 4.55‒12.65, Cd: 0.08‒0.46, Cr: 0.04‒5.47, Cu: 0.36‒3.25, Zn: 71.28‒399.57, Fe: 86.09‒384.65. The extents of different metals found in various fish muscles were relatively higher than the tolerable limits of FAO and WHO. The estimated daily intake (EDI) data of different fishes revealed that the analyzed fish species are not safe for human consumption as per the recommended daily dietary allowance limit set up by USEPA. The Targeted Hazard Quotient (THQ) values for most of the metals studied were below 1 which suggest that people may not experience significant health hazards immediately if they consume metal contaminated fishes. However, the total metal THQ (TTHQ) and Hazardous Index (HI) data pointed out the potential non-carcinogenic health hazards risks to people who are continuously consuming different fishes grown in the polluted aquatic system within the study area. KEYWORDS: Fishes, Water, Sediments, Heavy Metals, Bio concentration Factor, Health Risks.