Abstract:
Heavy and toxic metals contamination in various environmental segments in the vicinity of industrial areas is one of the most serious problems to maintain the environmental quality and sustainability in Bangladesh. Heavy and toxic metals are being discharged with wastewater from industrial and agricultural activities into Lakes and Rivers and their rates of mobilization and transportation into the surrounding environment have greatly accelerated in Bangladesh in recent years. In this study, water, sediments, and different fishes were collected during the winter season in 2019 from the aquatic ecosystems of Dhaka Export Processing Zone (DEPZ) Lake and Bangshi River in Savar, Dhaka which is considered as highly contaminated sites (HCS). Similarly, the representative water, sediments, and typical fishes were collected from long range contaminated sites (LCS) located at Kalihati Upazila in Tangail District. The sediment, water, and fishes samples have been digested with the acid mixtures following the standard procedures and then analyzed for determining the heavy and toxic metal contamination status, using the Flame-AAS and HG-AAS methods. A total of eight heavy and toxic metals such as Cr, Cu, Ni, Fe, Mn, Pd, Cd and As have been studied in all fish, sediment, and water samples. Different metal concentrations determined in fish, sediments, and water samples were compared with standard permissible/tolerable values set up by WHO, USEPA, and other countries such as China, India. Water pollution indices, sediment quality indices and metal contamination data in various fish species revealed that the entire highly contaminated sites (HCS) are severely polluted. In the long range contaminated sites (LCS), Mn in fishes; Fe, Mn, and Pb in water; Cu, Ni and Cr concentrations in sediments have been found considerably higher than the corresponding permissible levels of WHO, USEPA, India, and China. The highest concentration of metals appeared in fishes living in the middle and demersal layers. The estimated daily intake (EDI) data of different fishes in the highly contaminated sites, revealed that the analyzed fish species are not safe for human consumption as per the recommended daily dietary allowance limit set by USEPA. The Targeted Hazard Quotient (THQ) values for all metals studied were below 1 (except As and Pb for some species), which suggested that people would not experience significant health hazards immediately if they consume metal contaminated fishes. However, the total metal THQ (TTHQ) data pointed out the potential non-carcinogenic health hazards risks to the highly-exposed consumers in the polluted study area. The excessive consumption of metals contaminated fishes over a long period of time might cause the developments of severe carcinogenic effects in people as the calculated Target Cancer Risk (TR) values were found much higher than the USEPA threshold levels.
KEYWORDS: Fishes, Water, Sediments, Heavy Metals, Bioconcentration Factor, Health Risks
