Polychlorinated biphenyls (PCBs) present an environmental health hazard of global scale and man-made origin. Their impact on nearly every member of the biota results in a wide range of interacting negative effects. Due to their chemical nature, these recalcitrant toxicants are poised to enter and bioaccumulate in the food web. Recent advances in biodegradation research and molecular biology have shown that natural microorganisms and genetically modified bacterial strains could be used to decontaminate PCB-containing sites. The aim of this review is to summarize the chemistry, environmental fate and toxicological effects of PCBs and to evaluate the currently available technologies for nondisruptive elimination of PCBs from the environment.
"- chlorobiphenyls . Other studies in the literature ( Farrington et al . , 1986 ) have characterized contamination patterns that are dominated by the higher chlorinated PCBs to be the result of ancient and diffuse pollution . The highly chlorinated PCBs are the most resistant congeners , and thus are not as easily altered by biological processes ( Hooper et al . , 1990 ) . There was a quantifiable fraction of deca - chlorinated congeners in the suspended phase , and sediment which is represented only by PCB - 209 , a congener that makes up <1% of the PCBs in the com - mercial Aroclors ( Frame et al . , 1996 ) . The ratio of PCB - 209 to total PCBs was approximately 10% in both suspended water and sedi"
[Show abstract][Hide abstract] ABSTRACT: An on-going study in the Houston Ship Channel (HSC) characterized polychlorinated biphenyl (PCB) levels in sediment, water, and tissue in 2002-2003 and 2008. The observed PCB concentration ranges in all media were higher than those measured in other PCB-impacted water bodies in the world, with the highest concentrations occurring within the industrialized segments. Contrary to polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/PCDF) observations, the PCB concentrations in the dissolved phase were greater than the suspended phase. Possible explanations include passage of colloids, competition for adsorption sites from other hydrophobic contaminants, and continuing current sources. The PCB homologue distributions were similar for suspended water, sediment and tissue with the profile normalized around penta-chlorobiphenyls, while the dissolved phase profile normalized around tri-chlorobiphenyls. PCB-209 was detected in the suspended water phase and in sediment (10%) prompting interest into its sources to the HSC since PCB-209 was present only in rare commercial mixtures and is a byproduct in very few manufacturing processes. Inter-media analyses showed a significant correlation and transfer of PCBs. Dioxin-like PCBs contributed significant toxicity to total equivalent in tissue (33%), while they were insignificant in water (<10%) and sediment (<5%). The PCB concentrations over time showed a significant decrease in suspended water, sediment and tissue, while dissolved water concentrations showed insignificant change. The homolog distribution, however, showed a significant change in dissolved water and fish, a minor change in sediment and insignificant change in suspended water. Furthermore, an analysis for six representative congeners showed that they were accurate in predicting the total PCB concentrations and could be thus used as indicator PCBs.
"Their use was banned when they were identified as suppressors of the immune and reproductive systems. However, due to their chemical and physical properties they persisted in the environment , where they accumulated in food chains and in the fat tissue of animals and humans    . The major source of PCBs in the environment is redistribution due to volatisation from soil and water after disposal of wastes and leakage from electric transformers, resulting in PCB detection from undisturbed regions such as the arctic. "
[Show abstract][Hide abstract] ABSTRACT: Genetic analysis of the location of a mini-Tn5 promoted insertion of the LB400 bph operon in the rhizosphere coloniser Pseudomonas fluorescens F113rifPCB, allowed the development of a specific PCR detection system based on the unique DNA sequence at this insertion site. Real time PCR using both SYBR green chemistry and Fluorescence Resonance Energy Transfer probes allowed the precise identification of the recombinant strain and its quantitative detection in soil microcosms over a (bacteria/g) range of five orders of magnitude. This new assay can detect the genetically modified microorganism from soil in less than 90 min and at levels below the detection limits of standard PCR or cultivable counts on selective media.
"It is estimated that 70% of the world's production of PCBs are still in use or in stock and therefore it is likely that PCB contamination will continue to pose an environmental threat (Sumpter et al. 1997). Indeed, it is recognized that PCBs will remain in the environment over geological time (Hooper et al. 1990). PCBs are globally distributed , and are found predominantly in sediments in the aquatic environment. "
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to evaluate the effect of environmentally realistic egg loadings of the polychlori- nated biphenyl Aroclor 1254 on the subsequent growth and behavioural survival skills of Atlantic croaker Micropogonias undulatus larvae. Adult fish were given a dietary administra- tion of 0 (control) or 0.4 (dosed) mg Aroclor 1254 kg -1 fish d -1 for 2 wk during the final stages of gonadal recrudescence. Fertilised eggs collected from control and dosed adults im- mediately after spawning contained 0 and 0.66 µg Aroclor 1254 g -1 egg, respectively. Growth rate (increase in total length) of dosed larvae was significantly lower than that of control larvae between 2 and 13 d post-hatching, with dosed larvae showing a 4 d delay in attaining the same size as con- trol larvae. Behavioural assays were conducted to evaluate survival skills of larvae on Days 5 (complete yolk absorption), 9 (complete oil globule absorption), and 13 (larva wholly dependent on exogenous food sources) post-hatching. Sur- vival skills examined were potential foraging rate (routine swimming speed and activity) and the response to a startle (transient vibratory stimulus) stimulus. Routine swimming speed and activity were similar for control and dosed larvae. There was a significant dose × age interaction in the responses of the control and dosed larvae to a vibratory stim- ulus. The percentage of control larvae responding to the stimulus, and their average and maximum burst speeds, increased with age. In contrast, no such age-related response was found in the dosed larvae. The results indicate that envi- ronmentally realistic body burdens of Aroclor 1254 transfer to the eggs and larvae, reducing their growth rates and impair- ing their startle responses, possibly making the larvae more susceptible to predation.
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