In vitro cytotoxic assessment of e-waste-related chemical pollution in impacted soil matrix.

The environmental quality and toxicity of soil from some selected informal e-waste sites in West Africa was assessed on PLHC-1 liver cells. In addition, toxicity mechanisms such as apoptosis, necrosis and necroptosis were analysed in order to determine the effect of the actual chemical mixture present in the e-waste soil matrix. The investigation revealed that although e-waste soil extracts (polar and non-polar) and elutriates were significantly cytotoxic at the tested concentration (16 mg soil EQ/ml), PLHC-1 cell viability was not reduced below 50%. The non-polar extracts were more toxic compared to polar extracts and elutriates. The cytotoxic potency of soil from the informal e-waste-recycling sites ranged in this order: Alaba > Godome-Kouhounou > Agbogblosie. The study revealed that all e-waste soil extracts and elutriates induced significant (P < 0.01) PLHC-1 cell death by apoptosis and necrosis; however, cell death by apoptosis was higher compared to that by necrosis. The results indicated that except for non-polar extracts (N4, B4 and G4) from open burning areas that induced significant (P < 0.01) PLHC-1 cell death by necroptosis, other extracts and elutriates could not cause cell death by necroptosis. The study has demonstrated that soils from the Alaba e-waste site in Lagos could be more toxic than soils from Godome-Kouhounou (Cotonou) and Agbogblosie (Accra) e-waste sites and further highlighted open burning as an informal e-waste-handling method with greater negative impact on soil quality in the e-waste sites. The study emphasizes the urgent need for regulatory agencies to introduce regular residue-monitoring programmes in order to forestall the adverse effects of soil pollution episodes in the e-waste sites.

Assessment of the risk of death of Clarias gariepinus and Oreochromis niloticus pulse-exposed to selected agricultural pesticides.

Aquatic organisms are often exposed briefly to high pesticide concentration. Survival time model was used to study risk of death in C. gariepinus and O. niloticus fingerlings exposed to 24 mg/L atrazine, 42 mg/l mancozeb, 1 mg/L chlorpyrifos and 0.75 µg/L lambda cyhalothrin for 15, 30, 45 and 60 minutes and continuously for 96 hours. Mortality, time-to-death, weight, length, and condition factor of the fingerlings were recorded. Results obtained showed tilapia was more susceptible than catfish to continuous exposure but not pulse exposure. The survival probability of both species was similar when exposed for 15, 30 and 45 minutes (p > 0.05) but differed after 60 minutes (p < 0.05). Risk of death of catfish exposed briefly to atrazine, mancozeb and chlorpyrifos for 60 minutes was similar to 96 hours continuous exposure, same for tilapia exposed to 1 mg/L chlorpyrifos (p > 0.05). Survival probability of tilapia exposed to chlorpyrifos for 15, 30, 45 and 60 minutes was similar (p > 0.05) and was not influenced by pulse length. Pesticide hazard and risk of death decreased as fish size (weight, length, and condition factor) increased. Pulse toxicity assessment using survival models could make pesticides exposure assessment more realistic by studying factors that can influence the toxicity of pesticides.

Comparative assessment of the acute toxicity, haematological and genotoxic effects of ten commonly used pesticides on the African Catfish, Clarias gariepinus Burchell 1822.

Freshwater fishes are faced with increasing threats due to intensification of agriculture. This study evaluated the haematological and genotoxic effects of exposure of the African Catfish, Clarias gariepinus to sublethal concentrations of commonly used pesticides in agricultural settings. The evaluated pesticides were abamectin, carbofuran, chlorpyrifos, cypermethrin, deltamethrin, dichlorvos, dimethoate, fipronil, lambda-cyhalothrin and paraquat. The fishes were initially exposed singly to the pesticides for 96 h periods to determine their LC50, followed by exposure to sublethal concentrations (1/100th 96 h LC50) over a 21 d period. In all cases, a control experiment with catfishes kept in dechlorinated municipal water was monitored simultaneously. The 96 h LC50 values was found to vary widely from 2.043 µgL-1 (Lambda-cyhalothrin) to 10284.288 µgL-1(Paraquat). Significant differences (P < 0.05) were observed between mean haematological parameters-WBC, RBC, HGB, HCT, MCH and MCHC in the exposed and control catfishes. More so, micronucleus and nuclear abnormalities occurred at significantly higher proportions in pesticide exposed catfishes. Holistic cradle to grave approach as well as fate analysis is required to mitigate the potential harmful effects of pesticides to fresh water fishes.

Polycyclic Aromatic Hydrocarbons in Ologe Lagoon and Effects of Benzo[b]fluoranthene in African Catfish.

BACKGROUND: Ologe Lagoon is an important water body that receives effluents from neighboring industries. These effluents may increase the levels of anthropogenic contaminants in the lagoon, thereby creating stressors for aquatic organisms. OBJECTIVES: To assess the occurrence of polycyclic aromatic hydrocarbons (PAHs) in Ologe Lagoon, along with the histopathological, biochemical and genotoxic effects of the most prevalent PAH compound. METHODS: An initial field study was performed to determine the concentrations of PAHs in Ologe Lagoon, followed by a chronic toxicity test to assess the effects of the most prevalent PAH compound in a fish model (Clarias gariepinus). RESULTS: High molecular weight PAHs were more predominant than low molecular weight PAHs in the lagoon, with B[b]F being the most predominant. The formation of micronuclei and binuclei was induced by a 10-fold increase over the present environmental concentration of B[b]F in Ologe Lagoon. Histopathological studies showed that epithelial necrosis, fused lamellae, shortened lamellae, and desquamation were the major histological anomalies induced by ERCs of B[b]F. Results from the biochemical assay indicated that ERCs of B[b] F increased aspartate aminotransferase and alanine transaminase levels in fish. Glutathione-S-transferase, superoxide dismutase and catalase were inhibited in the exposed fish, whereas malondialdehyde was significantly increased. CONCLUSIONS: Concentrations of fluoranthene, pyrene, benzo[a]anthracene, and benzo[a] pyrene in the surface water of Ologe Lagoon were above the Canadian Council of Ministers of the Environment's (CCME) safe limits, suggesting that the water may not be safe for domestic uses, and the present concentration of B[b]F in Ologe Lagoon may be chronically toxic to aquatic organisms, in terms of oxidative stress and hepatotoxicity. COMPETING INTERESTS: The authors declare no competing financial interests.