Background. The effect of nanoparticles (NPs) on aquatic environments is poorly studied. Aim. This study evaluates the toxicity of joint effects of these different metal nanoparticles and their bulk in mixtures (Al2O3, CuO, and SiO2) on fish using histological biomarker. Materials and Methods. The bulk and nano sizes of three salts (Al2O3, CuO, and SiO2) were used. Nanosizes ranged from 25 nm to 100 nm. The juvenile fishes of Clarias gariepinus (mean Length: 12.3 ± 3.5 cm; mean weight: 18.52 ± 6.41 g) were used for the acute and chronic toxicity tests. They were exposed to 7 mg/L each of the bulk and nano sizes of the three metallic oxides either singly or in mixtures for 28 days. The basis for the sublethal concentration was that the 96 hr acute toxicity of the varied sizes of the three metallic oxides was nontoxic up to the concentrations of 100 mg/L with no significant mortality at the highest exposure concentrations. The gills were collected for histopathology. Results. Of the three metal oxide nanoparticles, SiO was the most toxic, with histopathological alteration index (HAI) of 20.0, followed by nano-CuO (HAI, 10.0) and nano-Al2O3 (HAI, 2.0). In single exposure, the gill alterations include high frequencies of erosion of gill lamella (EGL), hypertrophy (HPT), oedema (OD), and necrosis (N). Less damage was observed at the combination of the metal oxide nanoparticles of SiO + Al2O3, SiO + CuO and SiO + Al2O3 + CuO in equal (1 : 1—HAI, 2 and 6; 1 : 1 : 1—HAI, 6) and unequal ratios (1 : 2—HAI, 16 and 6; 2 : 1—HAI, 8 and 6). Similarly, all bulk combinations were also antagonistic except for the equal ratio of bulk CuO (HAI, 20) and bulk Al2O3 (HAI, 10) that gave additive effect with HAI of 32. Conclusion. The joint actions of nano Al2O3 and CuO with SiO produced a low toxic effect, unlike the high toxicity of their single trials; this also indicates that nano Al2O3 and CuO are antagonists. Similarly, among the bulk metal oxides (SiO, Al2O3, and CuO), CuO was the most toxic. Bulk SiO and Al2O3 are antagonistic on the effects of CuO on the fish gill. There is need to properly document the ecological implications of nanoparticles in the aquatic environment.

Study Background: Lead continues to be a significant public health problem in developing countries, where there are considerable variations in the sources and pathways of exposure. Aim: This study investigates the level of lead in drinking water sources in Shomolu, Yaba and Bariga areas of Lagos State, Nigeria and the human risk exposure using a mice model. Materials and Methods: Water samples were collected in public water sources (borehole, sachet water, bottle water and tap water) and analyzed for lead using Flame Atomic Absorption Spectrophotometer (Varian model-AA240FS) equipped with a lead hollow cathode lamp. Contamination factor was determined. Healthy Mature female albino-mice, weighing 25.3 ± 2.5 g were exposed to the contaminated drinking water for 28 days to the different concentrations of lead nitrate: 1 mg/l, 10 mg/l, 50 mg/l, 500 mg/l and 1000 mg/l. Blood and liver were collected for hematology liver function test and histopathology. Results: Lead concentrations in public water sources in Shomolu, Bariga and Yaba areas of Lagos State were below 5.0 µg/l and contamination factor were less than 1.0. At 1.0 mg/l (1000 µg/l) Lead exposure, the relative weight increase in this group (as compared to the controlled group) was very slow, up to the 14 th day (with weight loss of 3.17 g and relative weight loss of 23.1%), then increased up to the 28 th day (with weight loss of 7.34 g, and relative weight gain of 18.4%). At 50.0 mg/l Lead exposure, there was a rapid weight decrease, a greater relative weight loss was experienced at the 14 th day (weight gain, 1.36 g and 67.0% relative weight loss), then there was weight recovery at the 28 th day (weight gain of 4.60 g, 25.8% relative weight loss). The 100.0 mg/l Lead exposed group showed steady decrease in weight, 14 th day had a weight gain of 2.02 g and relative weight loss of 51.0% while the 28 th day had 2.10 weight gain and 66.1% weight loss respectively. In the 500.0 mg/l Lead exposure group, a similar trend was observed as with 1.

This study assessed the levels of oxidative stress biomarkers in gills and liver, as well as the activities of transaminases in the liver of Nile tilapia (Oreochromis niloticus), exposed to pharmaceutical effluents. The pharmaceutical effluents were collected from two pharmaceutical industries in Lagos, Nigeria. The assessment of physicochemical characteristics of the effluents indicated that some parameters were not in accordance with NESREA limits. The acute toxicity studies showed that 96hrLC 50 values of "effluent A" and "effluent B" were 27.0 ml/L and 18.0 ml/L respectively. The juveniles of O. niloticus were exposed to 1/100 th and 1/10 th LC 50 s of the two effluents for a period of 14 and 28 days. These concentrations significantly increased the level of the lipid peroxidation product, malondialdehyde. There was also inhibition of the activities of superoxide dismutase and catalase as well as significantly lower levels of reduced glutathione after 28 days. The levels of the transaminases (aspartate aminotransferase and alanine transaminase) were elevated in the liver of the fish after the exposure to the effluents. The present findings showed that the wastewater caused oxidative stress and hepatocellular damage in the fish suggesting potential ecotoxicological risks of the wastewater to aquatic organisms.