Waste engine oils are hazardous waste oils originating from the transportation sector and industrial heavy-duty machinery operations. Improper handling, disposal, and miscellaneous misuses cause significant air, soil, sediments, surface water, and groundwater pollution. Occupational exposure by prolonged and repeated contact poses direct or indirect health risks, resulting in short-term (acute) or long-term (chronic) toxicities. Soil pollution causes geotoxicity by disrupting the biocenosis and physicochemical properties of the soil, and phytotoxicity by impairing plant growth, physiology and metabolism. Surface water pollution impacts aquatic ecosystems and biodiversity. Air pollution from incineration causes the release of greenhouse gases creating global warming, noxious gases and particulate matter eliciting pulmonary disorders. The toxicity of waste engine oil is due to the total petroleum hydrocarbons (TPH) composition, including polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, ethylbenzene, xylene (BTEX), polychlorinated biphenyls (PCBs) congeners, organometallic compounds, and toxic chemical additives. The paper aims to provide a comprehensive overview of the ecotoxicological effects, human and animal health toxicology and exposure to waste engine oils. It highlights the properties and functions of engine oil and describes waste engine oil generation, disposal and recycling. It provides intensive evaluations and descriptions of the toxicokinetics, metabolism, routes of exposure and toxicosis in human and animal studies based on toxicological, epidemiological and experimental studies. It emphasises the preventive measures in occupational exposure and recommends risk-based remediation techniques to mitigate environmental pollution. The review will assist in understanding the potential risks of waste engine oil with significant consideration of the public health benefits and importance.
The research aimed to assess the influence of arbuscular mycorrhizal fungi (AMF) inoculation on the growth, tolerance, and phytoremediation capacity of Alocasia calidora (Schott) G.Don used in heavy metal/metalloid-polluted soil under field conditions. Five new, young A. calidora plants were planted in each treatment and control plot (1 m × 1 m). AMF inoculum was supplemented on days 0, 30, 60, and 90 in the treatment plot, and the experiment was conducted for 120 days. Substantial growth was observed in the roots and shoots of AMF-inoculated A. calidora. In the shoots of treated A. calidora, a high accumulation of Cu, As, Ni, Mn, and Pb was observed. The AMF-treated plant exhibited a higher accumulation of Cu, Fe, and Ni in the roots (P < 0.05). The removal efficiencies in the AMF-treated soil were 84.67, 74.82, 81.61, 80.77, 88.21, 92.26, 92.35, and 67.32% for As, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, correspondingly, while, for control, the corresponding values were 61.24, 52.42, 62.95, 33.46, 57.89, 61.45, 71.19, and 54.98%. AMF-treated A. calidora demonstrated an increased tolerance and metal/metalloid accumulation in response to a variety of compounds, including tryptophan, S-(4-nitrobenzyl) glutathione, 5,7,2',3'-tetrahydroxy flavone, 5,2-dihydroxy flavone, indole-acrylic acid, and various tripeptides. A. calidora proliferation, tolerance, and metal/metalloid accumulation were enhanced by the inoculated AMF. Therefore, treating soil contaminated with heavy metals/metalloids can be accomplished by combining AMF with plants.