Vehicular air pollution is a mounting health issue of the modern age, particularly in urban populations of the developing nations. Auto rickshaws are not considered eco-friendly as to their inefficient engines producing large amount of particulate matter (PM), which poses a significant environmental threat.
Major transformations in the environmental composition are principally attributable to the combustion of fuels by automobiles. Motorized gasoline powered two-stroke auto-rickshaws (TSA) and CNG powered four-stroke auto-rickshaws (FSA)are major sources of air pollution in south Asia and produce toxic amount of PM to the environment. In this study, during the first phase, the PM of TSA and FSA was characterized by using proton induced x-ray emission (PIXE) analysis. The observations of the existing investigation recognized significant increase in Al (P < 0.05), P (P < 0.01), and Zn (P < 0.01) from the PM samples of FSA. In addition, the concentrations of Cu, Fe, K, Mn, Mg, Na, S and Si were also observed exceeding the recommended NIES limits. On the contrary, increased concentration of Sr and V were observed in the PM samples from TSA. It is generally believed that FSA generates smaller amount of PM but the data obtained from this study clearly shows that emissions from FSA are comprised of potentially more toxic substances than TSA. The current research is specific to the metropolitan population and has evidently revealed an inconsistent burden of exposure to air pollutants engendered by FSA in urban communities, which could lead to disruption of several biological activities and may cause severe damage to entire ecological system.
The second phase of this study was conducted to ascertain toxic effects on angiogenesis, embryo development, embryonic movement and phytotoxicity of the PM from TSA and CNG powered FSA. Based on high amounts of aluminum quantified during PIXE analysis of PM from TSA and FSA, different concentrations of aluminum sulfate were also tested to determine its eco-toxicological potential. The PM solution from FSA, TSA and Aluminum sulfate exhibited anti-angiogenic potential with reduction in total area of CAM. Morphological evaluation of embryos exhibited varying degrees of hemorrhages in different groups. In case of phytotoxicity screening using Zea mays, the results demonstrated that all three tested materials were equally phytotoxic at higher concentrations in seed germination(p<0.001). Aluminum sulfate proved to be a highly phytotoxic agent even at the lowest concentration examined.
During the last phase, of the study, the MTT assay demonstrated a significant (p<0.001) dose dependent cytotoxic effect for TSA, FSA and aluminum sulfate on the BHK-21 cell line, establishing that the PM from FSA is a highly cytotoxic material. Mutagenicity was assessed by fluctuation Salmonella reverse mutation assay adopting TA100 and TA98 mutant strains with (+S9) and without (-S9) metabolic activation. Despite the fact that different concentrations of PM from both sources i.e. TSA and FSA were highly mutagenic (p<0.001) even at lower concentrations, the mutagenic index was higher in TSA. The chronic toxicity study revealed that chronic exposure to PM emitted from FSA and TSA resulted in peribrochiolitis, emphesema and infilteration of leukocytes in lung tissues. On the other hand liver, cardiac and kidney tissues exhibited degeneration and necrosis. The data shows that all tested materials are equally ecotoxicand if the existing trend of atmospheric pollution by auto-rickshaws is continued, air-borne metals/heavy metals will seriously affect the normal growth of local inhabitants and increased contamination of agricultural products, which will amplify the dietary intake of toxic element and could result in genetic mutation or long-term health implications.