Toxicity Evaluation and Cytogenetic Screening of Process Water Using a Plant Bioassay

The effect of toxic substances on aquatic lives from a wastewater indiscriminately discharged into the environment during oil and gas exploration activities in Nigeria is the focus of this study. A plant bioassay, the Allium cepa test, was used for the cytogenotoxicity screening of process water on root growth inhibition and chromosome abnormalities in the meristematic roots of the plant. Results of the physicochemical analysis of the wastewater collected from Nigerian Agip Oil Company (NAOC) facility at Ogboinbiri in Bayelsa State at the point of discharge into the environment showed that it had an unpleasant odour, was slightly alkaline (pH 7.72) and had high electrical conductivity (2793.33 μS/cm). Lead, manganese, iron, chromium and nickel were present at amounts (0.13, 0.33, 4.47, 0.17 and 0.10 mg/l respectively) above national (NESREA) and international (USEPA) limits for effluent discharge. Macroscopic evaluation of A. cepa cultivated in the wastewater resulted in significant (p<0.05) concentration-dependent root growth inhibition with an EC50 value of 14.8 % at 96 h. Root tip cells of the onion bulbs processed for cytological studies by the aceto-orcein squash technique after exposure to the wastewater for 48 h at concentrations of 0.5, 1.0, 2.5, 5.0, and 10% (v/v; wastewater/tap water) showed chromosomal aberrations at all concentrations. Statistical analysis of microscopic results show significant (p<0.05) concentration-dependent frequency of aberrant chromosomes and reduction of mitotic index. The findings in this study calls for proper treatment of process water before its discharge into water bodies to avoid cyto-genetic damages to aquatic lives.Keywords: Toxicity, chromosome aberration, Allium cepa, process wate

Studies on the Physicochemical Properties and Genotoxicity of Effluents from a Dairy Industry

In this study, the physicochemical analysis of raw and treated effluents obtained from a dairy industry was carried out and it revealed the presence of zinc, iron, manganese, nitrates and sulphates at levels higher than Standards Organisation of Nigeria (SON) permissible limits. The pH of the effluents was acidic (pH 4.7 and 6.43 respectively). Results obtained from the macroscopic evaluation of Allium cepa after 96 hours of cultivation in both effluents showed a significant (p<0.05) concentration-dependent root growth inhibition. Root tip cells of A. cepa processed for cytological studies by the aceto-orcein squash technique after exposure to the effluents for 48 hours at concentrations of 0.5%, 1.0%, 2.5%, 5.0%, and 10% (v/v) showed chromosomal aberrations at all concentrations. Sticky chromosomes with bridges and laggards were the most observed, however, the frequency of these aberrant chromosomes was more in the raw compared with those in the treated effluent. Statistical analysis of microscopic results showed significant (p<0.05) reduction of mitotic index in a concentration-dependent relationship. The findings of this study have shown that a combination of physicochemical analysis and genotoxicity assay is effective in assessing the mutagenic components of industrial effluents for environmental monitoring of pollutants. The treated wastewater from the dairy industry, if discharged into water bodies without further treatment, could pollute the receiving water bodies and impair biolife.Keywords: Dairy effluent, genotoxicity, Allium cepa, physicochemical analysi

Genotoxicity Screening of Industrial Effluents using Onion bulbs (<i>Allium cepa L.</i>)

The potential cytotoxicity and genotoxicity of three industrial wastewaters (brewery, rubber and bottling) in Benin metropolis using the Allium cepa test were investigated. A series of five small onion bulbs werecultivated in 0.01, 0.1, 1, and 10% of the wastewaters (v/v) and after 48 hours, one root tip from each bulb was harvested and processed for cytological studies by the aceto-orcein squash technique. At 72h, their cytotoxic effects on the root tips showed strong growth retardation in high concentrations of all the wastewaters. Compared to the control, treatment with the wastewaters resulted in root growth inhibition with EC50values of 35, 50 and 62% for bottling, rubber and brewery effluents respectively, and decrease in mitotic index with increasingconcentration for all samples and these were statistically significant (

Human exposure to organochlorine pesticides in vegetables from major cities in south-south Nigeria

Contamination of vegetables with organochlorine pesticides (OCPs) during cultivation could affect their nutritional value and also results in adverse health effects to consumers. Thus, this study evaluates human exposure to OCPs in vegetables from major cities in south-south Nigeria. A total of eighty vegetables consisting of Vernonia amygdalina, Telfairia occidentalis, Desmodium intortum cv and Talinum triangulare obtained from four major cities (Warri, Benin, Yenagoa and Port-Harcourt) in south-south Nigeria were analysed for OCPs using a gas chromatograph coupled with a mass selective detector. The results showed that the mean concentration of ∑20 OCPs in the vegetables ranged from 11.6 to 37.7 ng g−1 fresh wt for Vernonia amygdalina, 2.48–37.0 ng g−1 fresh wt for Telfairia occidentalis, 7.63–54.2 ng g−1 fresh wt for Desmodium intortum cv and 27.3–57.3 ng g−1 fresh wt for Talinum triangulare. The concentrations of OCPs were generally lower than their respective Maximum Residue Limits (MRLs). The EDI values of the ∑20 OCPs in the vegetables ranged from 141 to 464 ng kg−1 bw day−1 for children and 26.5–87.0 ng kg−1 bw day−1 for adults. The EDI of ∑Drins, ∑Chlordanes and ∑DDTs for the vegetables were below their respective acceptable EDI values set by FAO/WHO Joint Meeting on Pesticide Residue. The hazard index values for children and adults were generally <1 suggesting that there is no potential non-carcinogenic risk for children and adults consuming the vegetables. The total cancer risk values were above 1 × 10−6 and indicated that children and adults have moderate and low carcinogenic risks respectively from ingestion of these vegetables. The isomeric ratios and principal component analysis result showed that OCPs in these vegetables originated from both historical and recent usage in vegetable cultivation