The present study carried out to clarify the impact of heavy metals (Fe, Zn, Cu, Mn and Cd) pollution of Rosetta Branch on the antioxidant defence system activities and lipid peroxidation indicator MDA levels in O. niloticus tissues (liver and white muscles) collected from three stations from Rosetta Branch of River Nile in summer2014 and winter 2015. Rosetta Branch of River Nile exposed to high input of agricultural drainage water, sewage and industrial waste water which influence the living organisms especially fish. In the present study results revealed that the concentration of heavy metals (Fe, Zn, Cu, Mn and Cd) in water and fish samples increased in station II and III, especially in winter. In muscles of O. niloticus, the accumulation patterns of heavy metals were in the following order: Fe > Zn > Mn > Cu and Cd. The bioaccumulation factor (BAF) in winter was higher than summer. Antioxidant enzymes (SOD, CAT, GPx, GST and GR) activities and the indicator of lipid peroxidation MDA levels showed a significant increase in liver and white muscles of O. niloticus, in stations II and III, especially in winter. Moreover, the antioxidant enzymes activities and MDA levels were higher in liver than white muscles.

The increased utilization of silver nanoparticles (AgNPs) in multiple applications is leading to a rise in environmental contamination caused by their release, particularly in aquatic ecosystems. This study investigates the effects of different concentrations of AgNPs (10, 20, 50, and 100 µg/L) and bulk silver nitrate (AgNO₃) at 100 µg/L, on the hepatic antioxidant defense system, oxidative stress markers, and liver histopathology of Nile tilapia (Oreochromis niloticus), with sampling conducted biweekly over six weeks. AgNPs were chemically synthesized using trisodium acetate, yielding an average crystallite size of 29.92 nm. Results demonstrated that both antioxidant enzyme activities and lipid peroxidation (LPO) levels in Nile tilapia exhibited a dose-dependent response. During weeks 2 and 4, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), activities, along with LPO levels were significantly increased, while TAC levels notably decreased, especially at higher AgNPs concentrations. By week 6, antioxidant enzyme activities were suppressed, and LPO levels were markedly elevated in the higher AgNPs groups (AgNPs-50 and AgNPs-100). In contrast, fish exposed to bulk AgNO₃ exhibited activation of the enzymatic antioxidant system, although LPO levels remained elevated throughout the experimental period. Histopathological analysis revealed progressive liver damage, including congestion, dilation, fibrosis, fatty degeneration, and necrosis. These effects were more pronounced with higher doses of AgNPs. The results showed a mitigation response among all experimental groups during the first four weeks. However, by week 6, the antioxidant system in Nile tilapia exposed to higher doses of AgNPs failed to cope with the induced oxidative stress. This underscores the significantly higher ecological risks associated with prolonged exposure to AgNPs compared to AgNO₃, revealing a critical concern for the stability and health of aquatic ecosystems.

Lake Qarun is Egypt’s third-biggest lake, with an enclosed water system. The only source of water intake in the lake is drainage water, while evaporation is the only outflow path. This source of pollution affects water and fish; therefore, it threatens food security, which is an essential multi-dimensional goal in the United Nations 2030 Agenda. Fish contaminated with heavy metals are unsafe for humans and may cause serious health problems. Hence, this study aimed to determine the seasonality of heavy metals contents in the surface water and tissues of fishes (Tilapia zillii and Mugil cephalus) to assess and match the different exposure routes and possible health risks related to heavy metals in Lake Qarun. Various indices were estimated in the present research, based on the levels of heavy metals in the surface water and fish of the lake including heavy metal evaluation index (HMEI), chronic daily intake (CDI), target hazard quotient (THQ), hazard index (HI), carcinogenic health hazard (CHH), metal pollution index (MPI), estimated daily intake of heavy metals (EDI), and target cancer risk (TR). Additionally, the inverse distance weighting (IDW) technique from GIS was used to map the spatial distribution of the heavy metals in the lake during the seasons of summer and winter. Results revealed that higher metal contents were recorded in surface water and fish tissue samples during summer compared to winter. Moreover, the highest metal concentrations were reported in the eastern section of the lake. No health hazards were detected, either persuaded by the ingestion or dermal contact of Lake Qarun surface waters, while serious health hazards were recorded from the ingestion of both fish (especially T. zillii) during the study. Therefore, the residents and fishermen in the study area should be forewarned since they are highly exposed to all routes of health hazards related to heavy metals contents in the lake. In addition, an immediate consideration is necessary to avoid the continuous abuse of the lake by untreated sewage and agricultural effluents that limit the potential of Lake Qarun.

The Nile River islands are recognized as the most productive lands in Egypt. Although, these islands are vulnerable to several natural and man-made crises. The present study was aimed to evaluate the consequences of different anthropogenic activities on the heavy metals load and histological alterations inO. niloticusandS. galilaeuscollected from four different Nile River islands along the Great Cairo sector (Egypt), and the possible health risks for human consumers. Metals were accumulated in both fish muscles in the following order: Fe > Zn > Cu > Mn > Pb.S. galilaeuswas recorded higher metal pollution index thanO. niloticus, while El-Warrak Island was documented the highest MPI and hazard quotient among all sampling sites. All sampled tissues were recorded histopathological lesions in both fish. The present study may be considered as an early alert for habitual consumers, particularly at high consumption rates of some fish species.