Environmental, plant and animal exposure to hazardous substances from electronic wastes (e-wastes) in Nigeria is increasing. In this study, the potential cytogenotoxicity of e-wastes leachate and contaminated well water samples obtained from Alaba International Electronic Market in Lagos, Nigeria, using induction of chromosome and root growth anomalies in Allium cepa, and micronucleus (MN) in peripheral erythrocytes of Clarias gariepinus, was evaluated. The possible cause of DNA damage via the assessments of liver malondialdehyde (MDA), catalase (CAT), reduced glutathione (GSH) and superoxide dismutase (SOD) as indicators of oxidative stress in mice was also investigated. There was significant (p < 0.05) inhibition of root growth and mitosis in A. cepa. Cytological aberrations such as spindle disturbance, C-mitosis and binucleated cells, and morphological alterations like tumor and twisting roots were also induced. There was concentration-dependent, significant (p < 0.05) induction of micronucleated erythrocytes and nuclear abnormalities such as blebbed nuclei and binucleated erythrocytes in C. gariepinus. A significant increase (p < 0.001) in CAT, GSH and MDA with concomitant decrease in SOD concentrations were observed in the treated mice. Pb, As, Cu, Cr, and Cd analyzed in the tested samples contributed significantly to these observations. This shows that the well water samples and leachate contained substances capable of inducing somatic mutation and oxidative stress in living cells; and this is of health importance in countries with risk of e-wastes exposure.

Existing studies have shown the systemic damage of titanium dioxide (TiO₂) or zinc oxide (ZnO) nanoparticles (NPs), but there is little or no existing knowledge on the potential adverse toxic effects of the mixture of the two. In order to investigate the in vivo toxic effect of the mixture of TiO₂ NPs and ZnO NPs, the acute toxicities of TiO₂ NPs, ZnO NPs by themselves, and their mixture (1:1) were determined. The systemic toxicities of the individual NPs and mixture were evaluated in mice using hematological indices, hepatic, renal, and lipid profile parameters, and histopathology as endpoints. NPs were intraperitoneally administered at doses of 9.38, 18.75, 37.50, 75.00, and 150.00 mg/kg bw each. Individual NPs and their mixture were administered daily for 5 and 10 d, respectively. The LD₅₀ of ZnO NPs was 299.9 mg/kg while TiO₂ NPs by themselves or TiO₂ NPs + ZnO NPs were indeterminate due to the absence of mortality of the male mice treated. TiO₂ NPs, ZnO NPs by themselves and TiO₂ NPs + ZnO NPs induced significant alterations in the hematological and biochemical parameters, with higher toxicity at 10 d. Histopathological lesions were observed in the liver, kidneys, spleen, heart, and brain of mice treated with the individual NPs and their mixture. TiO₂ NPs + ZnO NPs were able to induce a higher systemic toxicity than TiO₂ NPs or ZnO NPs individually. Our data suggest that more comprehensive risk assessments should be carried out on the mixture of NPs before utilization in consumer products.