Heavy metal contamination of the Nigerian environment from e-waste management: A systematic review of exposure pathway and attendant pathophysiological implications.

Nigerian environment has become a depository of worrisome levels of toxicants including heavy metals. Electrical and electronic equipment which leads to the generation of e-waste is one of the considerable sources of environmental contaminants in Nigeria. This systematic review deployed Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) method to analyze various empirical and quantitative outputs on heavy metal components of e-waste management sites in Nigeria and investigated the distribution of heavy metals in several environmental matrices such as soil, water, surface dust, plant and blood of e-waste scavengers. Also, the probable environmental multi-transformation that ultimately potentiates the susceptibility of humans to the pathophysiological effects and genetic related disorders of exposure to heavy metal component of e-waste was discussed. The relative abundance of metals in soils due to inappropriate e-waste handling is given as follow: Fe>Cu>Pb>Zn>Mn>Co>Cr>Ni>As>Cd, in underground and surface water: Zn>Fe>Cu>Cr>Mn>Pb>Hg>Ni>Co>Cd>As; in surface dusts: Fe>Zn>Pb>Cu>Mn>Cr>Ni>Cd>Co; in plants: Pb>Cu>Mn>Zn>Ni>Cr>Cd obtained from the Nigerian environment. Moreso, the estimated abundance of heavy metals in the blood of e-waste scavengers is Nigeria is given as Cr>Cd>Hg>Zn>As>Pb>Cu>Mn>Fe. Conclusively, this study does not only show that various matrices of Nigerian environment is contaminated with heavy metal but also that the pattern of abundance differ in the environment and in biological systems with the latter having the abundance of Pb, Cr and Cd and the former having the abundance of Cu, Zn and Fe.

Alterations in viscera histoarchitecture and organosomatic index as biomarkers of toxicity induced by Aba-Eku and Olusosun solid waste landfill leachates in Rattus norvegicus.

Solid waste disposal generates leachate, a mixture of deleterious chemical, physical and microbial contaminants, which poses risk to human and wildlife health. Leachate toxicity on relative organ weight and histopathology of important viscera in mammalian body is scarce. Leachate induced toxic effects on organosomatic indices and histopathology of vital mammalian organs were investigated. Wister rats were orally exposed to 1 - 25 % of raw and simulated leachates from Aba-Eku and Olusosun landfills for 30 days. At post-exposure, organosomatic index and histoarchitectural assessment of major viscera (heart, spleen, thymus and lungs) were conducted. The physico-chemical and organic compositions of the leachates were analysed using standard protocol. The tested leachates decreased weekly and terminal body weights, and altered organosomatic index of examined viscera in rats. The histoarchitecture of the investigated viscera revealed pathologies that ranged from mild to severe degeneration, cellular infiltration, haemorrhage, congestion, necrosis, disorganization of tissues and vacuolations. Others include increased histiocytes within the bronchial associated lymphoid, lymphoid depletions, haemosiderin deposits and apoptosis were observed in the examined viscera. Physico-chemical analysis of the leachates showed different concentrations of toxic metals, PAHs and PCBs that were higher than national and international permissible limits allowed in wastewaters. The physico-chemical compositions of the leachates are capable of eliciting the observed alterations in organosomatic indices and histopathological lesions in mammalian viscera. Xenobiotic components of the leachates possibly generated free radicals and/or directly disrupted the organ architectures. These findings suggest health risk to wildlife and human population exposed to emissions from waste landfills.

Carcinogenic and non-carcinogenic risk assessment of consuming metal-laden wild mushrooms in Nigeria: Analyses from field based and systematic review studies.

This study investigated the potential health risk associated with the consumption of metal-laden mushrooms in Nigeria. Concentrations of Pb, Cd, Cr, Cu, Ni, Zn and Al in wild mushrooms collected from the Nigerian environment were measured using atomic absorption spectrometer. Also, systematic analysis of articles on metal accumulation in mushrooms from Nigeria were obtained from scientific databases. Using hazard model indices, the metal concentration in mushrooms were evaluated for their potential carcinogenic and non-carcinogenic health risk when consumed by adults and children. Zn and Cd, respectively, had the highest and lowest mean concentrations (mg kg-1) in the analysed mushrooms from the field study, while Fe and Co, respectively, had the highest and lowest mean concentrations (mg kg-1) in the systematically reviewed articles. In the field study, the percentage distribution of THQ of the heavy metals greater than 1 was 0% and 42.85% for adults and children respectively. While for the systematic study, 30% and 50% of the heavy metals for adults and children respectively exceeded the limit of 1. The hazard indices obtained from both the systematic and field studies for both age groups were all >1, indicating significant health risk. The findings from both the systematic and field studies revealed that consuming metal-laden mushrooms by adults and children increases the carcinogenic risk to Cd, Cr, and Ni since they exceeded the acceptable limit of 1E-04 stated by USEPA guideline. Based on the findings from the systematic and field studies, it suggests that consuming mushrooms collected from metal polluted substrates increases carcinogenic and non-carcinogenic health risk among Nigerians.

Mitochondrial dysfunctions elicited by solid waste leachates provide insights into mechanisms of leachates induced cell death and pathophysiological disorders.

Emissions (mainly leachates and landfill gases) from solid waste facilities are laden with mixtures of dangerous xenobiotics implicated with significant increase in various pathophysiological disorders including cancer, and eventual mortality of exposed wildlife and humans. However, the molecular mechanisms of solid waste leachates induce pathophysiological disorders and cell death are still largely unknown. Although, evolving evidence implicated generation of reactive oxygen species and oxidative stress as the possible mechanism. Recent scientific reports are linking reactive oxygen species and mitochondrial dysfunctions as the player mechanism in pathophysiological disorder and apoptosis induced by xenobiotics in solid waste leachates. This systematic review presents an explicit discussion of recent scientific findings on the structural and functional alterations in mitochondria induced by solid waste leachates as the molecular mechanisms plausibly responsible for the pathophysiological disorders, cancer and cell death reported in landfill toxicology and epidemiological studies. This review aims to increase scientific understanding on solid waste leachate induced mitochondria dysfunctions as the key player in molecular mechanisms of solid waste induced toxicity. The findings in this review were mainly from using primary cells, cell lines, Drosophila and fish. Whether the findings will similarly be observed in mammalian test systems in vivo and particularly in exposed humans, remained to be investigated. Improvement in technological advancements, enforcement of legislation and regulations, and creation of sophisticated health surveillance against exposure to solid waste leachates, will expectedly mitigate human exposure to solid waste emissions and contamination of the environment.

In vivo antiplasmodial activities and acute toxicity assessment of two plant cocktail extracts commonly used among Southwestern Nigerians.

Discovering and developing the desired antimalarials continue to be a necessity especially due to treatment failures, drug resistance, limited availability and affordability of antimalarial drugs and costs especially in poor malarial endemic countries. This study investigated the efficacies of two plant cocktails; CtA and CtB, selected based on their traditional usage. Efficacies of the cocktail extracts, chloroquine and pyrimethamine against Plasmodium berghei berghei were evaluated in mice using the suppressive, curative and prophylactic test models, after oral and intraperitoneal acute toxicity determination of the plant cocktails in accordance with Lorke's method. Data was analyzed using SPSS software version 23.0 with level of significance set at P < 0.05. The median lethal dose was determined to be higher than 5000 mg/kg body weight orally for both CtA and CtB; and 316.23 mg/kg body weight intraperitoneally for CtA. Each cocktail exhibited high dose dependent Plasmodium berghei berghei inhibition which was 96.95% and 99.13% in the CtA800 mg/kg and CtB800 mg/kg doses in the curative groups respectively, 96.46% and 78.62% for CtA800mg/kg and CtB800mg/kg doses in the suppressive groups respectively, as well as 65.05% and 88.80% for CtA800mg/kg and CtB800mg/kg doses in the prophylactic groups respectively. Throughout the observation periods, the standard drugs, chloroquine phosphate and pyrimethamine maintained higher inhibitions up to 100%. These findings demonstrate that CtA and CtB possess good antimalarial abilities and calls for their development and standardization as effective and readily available antimalarial options. The acute toxicity results obtained underscore the importance of obtaining information on toxicities of medicinal plant remedies before their administration in both humans and animals.

Plastic pollution threat in Africa: current status and implications for aquatic ecosystem health.

Rapid population growth and poor waste management practice are among the main drivers of plastic pollution in modern times, thus making Africa a hotspot for plastic pollution both now and in the future. This study is a review of plastic pollution reports from the African aquatic environment with regard to causes, current status, toxicological implications and implications for ecosystem services. A total of 59 plastic pollution studies from 1987 to September 2020 were reviewed. They comprised 15 from North Africa (NA) (Algeria, Egypt, Morocco and Tunisia), six from East Africa (EA) (Ethiopia, Kenya, Tanzania and Uganda), 13 from West Africa (WA) (Ghana, Guinea-Bissau, Mauritania and Nigeria), and 25 studies from Southern Africa (SA) (South Africa). This shows that plastic pollution studies in Africa, according to the sub-regions, are in the order: SA > NA > WA > EA. High human population in the basins of African large aquatic systems is identified as the greatest driver enhancing plastic surge in the aquatic environment. The occurrence of plastics was mostly reported in the estuarine/marine environment (42 studies) compared to the freshwater environment (only 17 studies). Plastics have also been reported in the three compartments of the aquatic environment: water column, benthic sediment and animals. Zooplankton, annelids, molluscs, insects, fishes and birds were reported as bioindicators of plastic ingestion in the inland and coastal waters of Africa. Polyethylene, polyethylene terephthalate (polyester) and polypropylene were the common plastic polymers observed in the African aquatic environment. In situ toxicological implications of the ingested plastic polymers were not reported in any of the studies. However, reports from laboratory-controlled experiments showed that these polymers are deleterious to aquatic animal health. More research efforts need to delineate the plastic pollution status of the East, West and North of Africa. Furthermore, such studies are required to identify the plastic polymers and in situ ecotoxicological impacts of plastics on both animal and human health.

Bioactivity and modulatory functions of Napoleona vogelii on oxidative stress-induced micronuclei and apoptotic biomarkers in mice.

Napoleona vogelii is used in traditional medicine for the management of pain, inflammatory conditions and cancer. This study was conducted to investigate the modulatory mechanisms of methanol stem bark extract of N. vogelii on induction of micronuclei, apoptotic biomarkers and in vivo antioxidant enzymes in mice. Forty male albino mice were randomly divided into eight groups (n = 5) and were administered distilled water (DW, 5 mL/kg) as negative control, 100, 200 or 400 mg/kg of the extract respectively for 28 days before the injection of cyclophosphamide (CP, 40 mg/kg) i.p. on the 28th day. The remaining groups were administered 100, 200 or 400 mg/kg of the extract only for 28 days. Twenty four hours after injection of CP or administration of the last dose of extract, animals were euthanized by cervical dislocation and blood samples collected for determination of in vivo antioxidants, the spleen harvested for immunohistochemical expression of NFκB, Bcl-2, Bax and p53. Bone marrow smears were also made for the micronucleus assay. Treatment with the extract resulted in a significant (p < 0.0001) reduction in frequency of micronucleated polychromatic erythrocytes (MNPCEs) compared to CP exposed control conferring protection of 75.09, 94.74 and 96.84% at 100, 200 or 400 mg/kg respectively. In extract and CP exposed animals, there were significant (p < 0.05) increases in GSH, GST and SOD with a corresponding significant (p < 0.05) reduction in MDA. In addition, the extract significantly downregulated cytoplasmic levels of NFκB and Bcl-2 and upregulated Bax and p53. These findings demonstrate that N. vogelli may serve as an interesting lead for chemo-preventive drug development.

Microplastics in the marine environment: Current trends in environmental pollution and mechanisms of toxicological profile.

The global plastics production has increased from 1.5 million tons in the 1950s to 335 million tons in 2016, with plastics discharged into virtually all components of the environment. Plastics rarely biodegrade but through different processes they fragment into microplastics and nanoplastics, which have been reported as ubiquitous pollutants in all marine environments worldwide. This study is a review of trend in marine plastic pollution with focus on the current toxicological consequences. Microplastics are capable of absorbing organic contaminants, metals and pathogens from the environment into organisms. This exacerbates its toxicological profile as they interact to induced greater toxic effects. Early studies focused on the accumulation of plastics in the marine environment, entanglement of and ingestions by marine vertebrates, with seabirds used as bioindicators. Entanglement in plastic debris increases asphyxiation through drowning, restrict feeding but increases starvation, skin abrasions and skeletal injuries. Plastic ingestion causes blockage of the guts which may cause injury of the gut lining, morbidity and mortality. Small sizes of the microplastics enhance their translocation across the gastro-intestinal membranes via endocytosis-like mechanisms and distribution into tissues and organs. While in biological systems, microplastics increase dysregulation of gene expression required for the control of oxidative stress and activating the expression of nuclear factor E2-related factor (Nrf) signaling pathway in marine vertebrates and invertebrates. These alterations are responsible for microplastics induction of oxidative stress, immunological responses, genomic instability, disruption of endocrine system, neurotoxicity, reproductive abnormities, embryotoxicity and trans-generational toxicity. It is possible that the toxicological effects of microplastics will continue beyond 2020 the timeline for its ending by world environmental groups. Considering that most countries in African and Asia (major contributors of global plastic pollutions) are yet to come to terms with the enormity of microplastic pollution. Hence, majority of countries from these regions are yet to reduce, re-use or re-circle plastic materials to enhance its abatement.