Cyto-genotoxic potential of petroleum refinery wastewater mixed with domestic sewage used for irrigation of food crops in the vicinity of an oil refinery

Petroleum refinery wastewater combined with domestic sewage were collected from the open channel in the vicinity of Mathura oil refinery, UP (India) and analysed by inductively coupled plasma optical emission spectrometry (ICP-OES) and gas chromatography-mass spectrometry (GC-MS) for elemental analysis and organic pollutants, respectively. Several potentially toxic and non-toxic elements were found to be present in the wastewater samples. GC-MS analysis revealed the presence of several organic contaminants including pesticides. Wastewater samples were extracted using amberlite XAD4/8 resins and liquid-liquid extraction procedures using different organic solvents. The extracts were tested for their cyto-genotoxic potential using bacterial (Salmonella mutagenicity test, E. coli K-12 DNA repair defective mutants, Bacteriophage λ assay) and plant (Vigna mungo phytotoxicity test, Allium cepa chromosomal aberration assay) systems. A significant increase was observed in the number of revertants of TA97a, TA98 and TA100 strains with the test samples and XAD concentrated samples were found to be more mutagenic than liquid-liquid extracts. Colony forming units (CFUs) of DNA repair defective mutants of E. coli K-12 recA, lexA and polA declined significantly as compared to their isogenic wild-type counterparts with the test samples. Significant reduction in plaque forming units (PFUs) of bacteriophage λ was also found on treatment with the solvent extracts. Presence of several toxic pollutants in the wastewater apply prohibitive action on the seed germination process. Germination rate of Vigna mungo seeds as well as radicle and plumule lengths were found to be affected when treated with different concentration of wastewater as compared to control. Present study also indicated concentration dependent reduction in mitotic index of A. cepa i.e., 16.38% at 5% and 9.74% at 100% wastewater and percentage of aberrant cells were highest at 100% effluent. Present findings indicated that mutagenicity/genotoxicity of wastewater is due to the mixture of genotoxins; poses serious hazards to the receiving waterbodies which require continuous monitoring and remedial measures for their improvement.