Ecotoxicological and health risk assessing of heavy metals and microplastics in African catfish (Clarias gariepinus) of Burullus Lake, Egypt.

چکیده اصلی

One of the most serious pollution problems in aquatic lake systems is contamination by heavy metals (HMs) and microplastics (MPs). These pollutants cause serious harm to aquatic organisms. The research focused on studying HMs (Mn, Cd, Pb, Ni, and Cr) and MPs in organs of Clarias gariepinus inhabitant of Burullus Lake. Water and live fish samples were collected from the northwestern part of the lake, preserved and then transferred for laboratory analyses. HMs were analyzed using digestion methods with nitric acid and hydrogen peroxide. For MPs, 10% potassium hydroxide was used. The metal ions followed these orders Mn > Cr > Cd > Ni > Pb and Mn > Cr > Cd > Pb > Ni in the liver and muscle, respectively. In water, this order was Mn > Cr > Pb > Ni > Cd. The highest bioconcentration factor (BCF) was for Mn in both tissues; the lowest was Pb in the liver and Cd in the muscle. The metal concentrations exceeded the limits reported by FAO/WHO. The estimated daily and weekly intakes (EDI and EWI) were higher than 1 in both adults and children. The hazard index (HI) was within the limit of 1. The values were higher for Cd, Pb, and Ni than the tolerable value of lifetime carcinogenic risk according to USEPA of (10-5). The most abundant microplastics (MPs) were transparent lines, followed by colored fibers and then colored fragments. The polymeric composition of microplastics was 333 T Teflon (polytetrafluoroethylene [PTFE]) in the intestine and 118 T (low-density polyethylene [LDPE]) in the muscle. The pollution load index for MPs was more than 1 in both tissues. The histopathological changes indicated a loss of detoxification ability and intestinal integrity, as manifested by hepatocellular necrosis and vacuolar degeneration. Intestinal lesions exhibited villous sloughing along with necrobiotic alterations and iron deposition. It is concluded that high contamination ratios of MPs were observed in the tested samples and these ratios may increase within time if water and sediments are not treated effectively.

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