J. Xenobiot., Volume 3, Issue 1 (December 2013) – 8 articles

Our recent history shows that degradation of aquatic ecosystems essentially stems from industrialization, urbanization and increasing human populations. After a first industrial boom in the late 19th century, contamination pressures on receiving waters now appear to be continual because of expanding economies and technologies developing at the planetary scale. Given the diversity of issues, problems and challenges facing water quality today because of complex waste and chemical discharges into waterways, aquatic ecotoxicology has blossomed with time into a more mature discipline of the environmental sciences. Its two fundamental pillars, bioassays and biomarkers, have become essential tools that allow the determination of numerous and versatile effects measurements. Herein, we demonstrate some of the ways in which these tools have been applied and how they have evolved over the past decades to appraise the ecotoxicity of contaminants impacting aquatic systems. Examples discussed are largely reflective of work conducted in the Environment Canada (EC) laboratories (Saint-Lawrence Centre, Montréal, Canada). Success stories include improvement of industrial effluent quality contributing to beluga whale population recovery in the Saint-Lawrence River, biomarker field studies conducted with endemic and caged bivalves to more fully comprehend urban effluent adverse effects, and increased discernment on the hazard potential posed by emerging classes of chemicals. Ecotoxicology continues to be confronted with diverse issues and needs related to a myriad of chemical contaminants released to aquatic environments worldwide. To cope with these, ecotoxicology will have to bank on new tools (e.g., toxicogenomics, bio-informatics, modeling) and become more interdisciplinary by taking into account knowledge provided by other disciplines (e.g., ecology, chemistry, climatology, microbiology) in order to more fully understand and adequately interpret hazard. This will be paramount to supply regulators and legislators with the sound and scientifically valid information needed in order to mitigate environmental degradation. Full article

People are encouraged to consume more fresh vegetables due to the high nutritional value and fibre contents in vegetables. At the same time, due to pesticidal residue in vegetables, vegetable consumption is considered as an important route of pesticides uptake by human beings. Pesticides, particularly organochlorines such as Aldrin, heptachlor and isomers of dichlorodiphe - nyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) are a major concern because of their persistence, bioaccumulation, toxicity, and long-range environmental transport ability. Hence information on such toxic contaminants in vegetables is very essential, due to human health concern. In order to assess the potential health risks associated with vegetable consumption due to pesticidal residues of DDT and HCH, sixty four samples of commonly available vegetables were collected from a local market in West Bengal, India and analysed for DDT and HCH. In this study, estimated average daily intake of HCHs and DDTs through vegetables was ranged between 5.0x10^–8–9.1x10^–6 mg kg^–1 day^–1 with an average value of 2.0x10^–6 mg kg^–1 day^–1. Human health risk was assessed in terms of incremental lifetime cancer risk and health hazard index was between 1.7x10^–8–8.8x10^–6 and 1.5x10^–7– 1.7x10^–2, respectively. Generated results were compared with maximum residual levels and reference values, were within acceptable limits and suggested no health risk to the human populations. Therefore, an extensive study on vegetables with the inclusion of other persistent organic pollutants and toxic metals should be carried out to know the overall scenario of contamination of vegetables. Full article

When oil spill occurs, it poses serious toxic hazards to all forms of life. Mixed culture of Burkholderia cepacia and Corynebacterium sp isolated from refinery sludge using selective enrichment technique was used for bioremediation of refinery wastewater in a laboratoryscale bioreactor. Physicochemical parameters of both raw and treated water were as determined and compared with Federal Environ - mental Protection Agency (FEPA-limit, Abuja, Nigeria) to asses the efficiency of the bioremediation process. Each of the bacterium was screened for the presence of plasmid DNA and for the involvement or otherwise of plasmid in the bioremediation of wastewater. The immobilised cells showed percentage decrease in chemical oxygen demand (97%), biochemical oxygen demand (94%), phenol (98%), total petroleum hydrocarbon (79%), oil and grease (90%) of the refinery waste water after 20 days of treatment while their transconjugants showed the multiplicative effect by achieving the same percentage after 10 days of treatment. Therefore, the findings revealed that bioaugmentation of wastewater using transmissible catabolic plasmid will enhance efficiency of the bioremediation by spreading the plasmid among indigenous microbial community either through horizontal gene transfer or transformation. Full article

Sammulfar (arsenic trioxide) is a notorious poison and has extensively been studied for its toxicity. It is in use for various purposes for centuries and is used even today as a therapeutic agent in the form of kushta (calx) in traditional systems of medicine, particularly Unani medicine, but without apparent safety data. The present study, therefore, was conducted to produce data for prolong use of calx of arsenic trioxide. The calx (test drug) was prepared by the method described in National Formulary of Unani Medicine. The study was carried in healthy Wistar rats of either sex; weighing 150-250 g; 2-3 months of age, in a dose dependent manner, following the methods of Gupta et al. (2002), Ghosh (2008) and Klaassan (2008). The animals were divided into four groups of 10 animals each. Group I served as control, where as group II, III and IV were used for three dose levels of the test drug i.e. low (8.75 mg^–1 kg), medium (17.50 mg^–1 kg) and higher (26.25 mg^–1 kg). Standard parameters usually applied for chronic toxicity studies were considered. The study revealed dose dependent toxicity. Usual signs of chronic toxicity were observed during the study. Low dose of Kushta Sammulfar (KSF) did not produce remarkable toxic effects. Mild to moderate toxicity was seen in KSF-II and KSF-III. Full article

Paraquat (PQ) is one of the most used herbicide globally; applied around trees in orchards and between crop rows to control broad-leaved and grassy weeds. Its oxidation results in the formation of superoxides which causes damage to cellular components. In this study, we determined the antioxidant effect vitamin C has on hemograms [hemoglobin (Hb), packed cell volume (PCV) and total white blood cells count] of rats under these toxic insults. The animals grouped (A-D), comprising subgroups without vitamin C (A₁, B₁, C₁, D₁) and subgroups on vitamin C (A₂, B₂, C₂, D₂), received different sub-lethal doses of PQ administered intraperitoneally monthly to the animals over a period of three months. The Hb values obtained were significantly reduced (P≤0.05) at month 1 and (P≤0.001) at months 2 and 3. These changes became more pronounced with increased dose and time. Vitamin C treated subgroups (B₂, C₂ and D₂) had better Hb values than those without it (B₁, C₁ and D₁) but the values were still significantly low when compared to the control subgroups (A₁ and A₂). This same trend was observed in the PCV results obtained. The Control subgroups showed that vitamin C treated subgroup (A₂) had a more improved hemogram values than subgroup on water only (A₁), but they were all higher than that of the test subgroups. These PQ induced anaemia were ameliorated by the subsequent administration of vitamin C, and continuous treatment with vitamin C restored the health status of the animals so treated. Full article

Paraquat (PQ) is a bipyridylium herbicide; applied around trees in orchards and between crop rows to control broad-leaved and grassy weeds. Its oxidation results in the formation of superoxides which causes damage to cellular components. In this study, we determined the antioxidant effect vitamin C has on the liver enzymes [aspartate aminotransferase (SGOT), alanine aminotranferease (SGPT), alkaline phosphatase (ALP), and gamma-glutamyltransferase (GGT)] of rats under this toxic insult. Male rats in groups (A, B, C and D) were intraperitoneally injected with different sublethal increasing doses (0, 0.02, 0.04 and 0.06 g/kg body weigh) of PQ respectively on monthly basis. Subsequently, the subgroups (A₂, B₂, C₂ and D₂) were given orally, 200 mg/L vitamin C, while the subgroups A₁, B₁, C₁, and D₁, received only water. Four animals per subgroup were decapitated on monthly basis and blood samples taken for enzyme assay. The parameters studied were - SGOT, SGPT, ALP and GGT - liver enzymes. The dose and time dependent PQ toxicity effect resulted in highly elevated Liver enzymes activities. The subgroups on vitamin C had significantly lower enzyme activities when compared to the same subgroups on only PQ insult. But the values were high when compared to the control subgroups (A₁ and A₂). These results were indication that vitamin C when given at moderate doses and maintained for a longer period could be a life saving adjunct to toxic insult. Full article

Citrobacter freundii A1 isolated from a sewage treatment facility was demonstrated to be able to effectively decolorize azo dyes as pure and mixed culture. This study reports on the investigation on the enzymatic systems involved. An assay performed suggested the possible involvement of flavin reductase (Fre) as an azo reductase. A heterologouslyexpressed recombinant Fre from C. freundii A1 was used to investigate its involvement in the azo reduction process. Three model dyes were used, namely Acid Red 27 (AR27), Direct Blue 15 (DB15) and Reactive Black 5 (RB5). AR27 was found to be reduced the fastest by Fre, followed by RB5, and lastly DB15. Redox mediators nicotinamide adenine dinucleotide (NADH) and riboflavin enhance the reduction, suggesting the redox activity of the enzyme. The rate and extent of reduction of the model dyes correlate well with the reduction potentials (E_p). The data presented here strongly suggest that Fre is one of the enzymes responsible for azo reduction in C. freundii A1, acting via an oxidation-reduction reaction. Full article

This study deals with the distribution of dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs) in urban soils, their possible sources and probabilistic human and environmental health risk. The average concentrations of total HCHs and total DDTs in the soils were in the range of 0.56-8.52 mg kg^–1 and 0.54-37.42 mg kg^–1, respectively, which were lower than guideline limits. The compositional analysis of HCH isomers reflects contaminations from recent usage. However, isomeric ratios between DDT, DDE and DDD, indicate anaerobic degradation of DDT and contaminations from aged DDT. Human and environmental health risk assessment was carried out by the estimation of lifetime average daily dose (LADD), incremental life time cancer risk (ILCR) and non carcinogenic health hazard quotient (HQ). LADD of total pesticides (HCH and DDT) for human adults and children was ranged between 3.3x10^–9-6.6x10^–8 mg kg^–1d^–1 and 1.7x10^–8-3.4x10^–7 mg kg^–1 d^–1, respectively. The cumulative ILCR for adults and children was ranged from 5.1x10^–9 to 4.6x10^–8 and 2.6x10^–8 to 2.4x10^–7, respectively. The HQ was ranged between 1.8x10^–6- 1.4x10^–4 and 9.5x10^–6-7.2x10^–4, respectively for adults and children. These estimated ILCR and HQ were within the safe acceptable limits, indicating negligible risk to the residents of the study area. Full article