Since 1950 to 2018, about 6.3 billion tonnes of plastics have been produced worldwide, 9% and 12% of which have been recycled and incinerated, respectively. Human population increase and consistent demand for plastics and plastic products are responsible for continuous increase in the production of plastics, generation of plastic waste and its accompanied environmental pollution. We have reviewed in this paper, the most relevant literatures on the different types of plastics in production, the hazardous chemical constituents, prevailing disposal methods and the detrimental effects of these constituents to air, water, soil, organisms and human health viz-a-viz the different disposal methods. Papers that reported environmental and public health effects of plastic constituents but not plastics directly were also reviewed. Varieties of plastics used in the production of many consumable products including medical devices, food packaging and water bottles contain toxic chemicals like phthalates, heavy metals, bisphenol A. brominated flame retardants, nonylphenol, polychlorinated biphenylethers, dichlorodiphenyldichloroethylene, phenanthrene etc.

Pharmaceutical industries are among the major contributors to industrial waste. Their effluents when wrongly handled and disposed of endanger both human and environmental health. In this study, we investigated the potential genotoxicity of a pharmaceutical effluent, by using the Allium cepa, mouse- sperm morphology, bone marrow chromosome aberration (CA) and micronucleus (MN) assays. Some of the physico-chemical properties of the effluent were also determined. The A. cepa and the animal assays were respectively carried out at concentrations of 0.5, 1, 2.5, 5 and 10%; and 1, 5, 10, 25 and 50% of the effluent. There was a statistically different (p < 0.05), concentration-dependent inhibition of onion root growth and mitotic index, and induction of chromosomal aberrations in the onion and mouse CA test. Assessment of sperm shape showed that the fraction of the sperm that was abnormal in shape was significantly (p < 0.05) greater than the negative control value. MN analysis showed a dose-dependent induction of micronucleated polychromatic erythrocytes across the treatment groups. These observations were provoked by the toxic and genotoxic constituents present in test samples. The tested pharmaceutical effluent is a potentially genotoxic agent and germ cell mutagen, and may induce adverse health effects in exposed individuals.

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.

Information on the potentials of electronic waste (e-waste) leachate to induce genotoxicity in eukaryotic cells is scarce. In this study, we investigated the potential of raw and simulated e-waste leachates to induce cytotoxicity and DNA damage in Allium cepa. Roots of onion bulbs were grown in five concentrations: 1, 5, 10, 25 and 50% (v/v; leachate/tap water) of each of the leachate sample, tap water (negative control) and 0.25 ppm lead nitrate (positive control). Cytogenetic and root length inhibition analyses were evaluated at 48 and 72 hours respectively. There was concentration-dependent significant (p < 0.05) inhibition of root growth and cell proliferation compared to the negative control. The leachates also induced morphological modifications of the roots and cytological aberrations such as anaphase bridge, sticky chromosomes and binucleate cells. Fe, Cd, Mn, Cu, Ni, Cr As, Zn and Pb analysed in the samples were believed to play significant role in the observed cytogenotoxicity in A. cepa. These observations indicate that e-waste leachate contained substances capable of inducing cytotoxicity and somatic mutations in A. cepa. This is of environmental and public health importance in Nigeria and other developing nations whose populations are at risk of e-waste exposure.