Tissue distribution of planar and non-planar chlorobiphenyls, 4,4'-DDE and hexachlorobenzene in sheep and lambs

The bioconcentration and distribution pattern of individual PCB congeners (IUPAC Nos: -54, -80, -155 and -169) and organochlorine pesticides (HCB and 4,4'-DDE) in blood, adipose tissue, liver and brain were examined in sheep two months after administration and in their offspring continuously exposed during the two months lactation period. Analyses were performed by high resolution gas chromatography. The levels of individual organochlorines varied significantly between tissues; the tissue/blood ratio (on a fat basis) varied by two orders of magnitude for individual congeners. The bioconcentration of the toxic planar PCB-169 congener was the highest in the liver and the lowest in the brain of the sheep.     

Microbial dechlorination of polychlorinated biphenyls in anaerobic sewage sludge.

The potential of a chlorophenol (CP)-adapted consortium to dechlorinate polychlorinated biphenyls (PCBs) in sewage sludge was investigated. Results show that dechlorination rates differed significantly depending on sludge source and PCB congener. Higher total solid concentrations in sewage sludge and higher concentrations of chlorine in PCB resulted in slower dechlorination rates. No significant difference was found for 2,3,4,5-CB dechlorination from pH 6.0 to pH 8.0; however, dechlorination did not occur at pH 9.0 during a 41-day incubation period. Results show that at concentrations of 1 to 10 mg/L, the higher the PCB concentration, the faster the dechlorination rate. In addition, dechlorination rates were in the following order: methanogenic conditions > sulfate-reducing conditions > denitrifying conditions. The addition of acetate, lactate, pyruvate, and ferric chloride decreased lag times and enhanced dechlorination; however, the addition of manganese dioxide had an inhibitory effect. Dechlorination rates were also enhanced by the addition of PCB congeners, including 2,3,4-CB, 2,3,4,5-CB and 2,3,4,5,6-CB in mixture. Overall results show that the CP-adapted consortium has the potential to enhance PCB dechlorination. The optimal dechlorination conditions presented in this paper may be used as a reference for feasibility studies of PCB removal from sludge.     

Clearance of PCDD/Fs via the gastrointestinal tract in occupationally exposed persons.

A digestive tract mass balance was performed on six men with high body burdens of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Intake via food was measured by analyzing duplicate portions of the food consumed by the volunteers and excretion via feces was determined by quantitative collection and analysis of the feces. Blood samples were taken to determine the current body burden. The results showed that the quantity of non-metabolized chemical excreted in the feces clearly exceeded the uptake via food for all of the 2,3,7,8-substituted PCDDs and some of the PCDFs, indicating a significant clearance across the gastrointestinal tract. The concentrations of these PCDD/F congeners in blood and feces were highly correlated (r > 0.8), demonstrating that the fecal PCDD/F content was determined by the body burden. The half lives in the test persons due to fecal clearance of non-metabolized chemical were estimated from the excretion rate and the current body burden and ranged between 10 years (Cl8DD) and 33 years (2,3,4,7,8-Cl5DF). These were compared with the overall contaminant half-lives due to all clearance processes which were calculated from the body burden and the decrease in blood concentrations measured over several years. The fecal clearance of non-metabolized PCDD/F contributed on average between 37% (2,3,7,8-Cl4DD) and 90% (Cl8DD) to the total elimination. This indicates that the gastrointestinal pathway plays a decisive role in the clearance of most 2,3,7,8-subsituted PCDD/F congeners.     

Dilemmas facing regulatory and advisory bodies dealing with conflicting results.

Regulatory and advisory bodies have to take into account the possibility that conventional toxicological screening and testing methods may be failing to pick up relevant effects, with the implication that testing may need to go down to much lower exposure levels and use specifically designed studies. In the paper, attention is focused on the problems of understanding endocrine disrupting activity. The shape of the dose-response curve for endocrine disrupters may differ from that normally associated with toxic chemicals (the monotonic sigmoid curve). Thus, prediction of both the nature of the effects of potential endocrine disrupters and the intensity of those effects at different doses may be equally difficult. Endocrine effects are not currently amenable to analysis by a single apical assay. While existing toxicological tests can pick up many end-organ and functional effects that are relevant to endocrine disturbances, they are generally poor at exploring apparently subtle effects such as disturbances of brain endocrine homeostatic mechanisms which may be critical for normal development.     

Biodegradation of coplanar polychlorinated biphenyls by anaerobic microorganisms from estuarine sediments.

In this study, we investigated the biodegradability of biphenyl and 5 congeners (one non-planar and four coplanar) of polychlorinated biphenyl (PCB). Biphenyl, the non-planar congener 2,3',4',5-tetrachlorobiphenyl (25-34 CB), and the four coplanar congeners 3,3',4,4'-tetrachlorobiphenyl (34-34 CB), 3,4,4',5-tetrachlorobiphenyl (345-4 CB), 3,3',4,4',5-pentachlorobiphenyl (345-34 CB), and 3,3',4,4',5,5'-hexachlorobiphenyl (345-345 CB) were amended at a concentration of 10 mg/L into anoxic sediment slurries collected from the estuaries of the Tansui River and the Erjen River. During 2 years' incubation under sulfidogenic conditions, biphenyl was persistent, while all other chlorinated congeners, except for 345-345 CB, were dechlorinated with or without a lag period in sediment slurries collected from both rivers. Dechlorination of coplanar and non-planar congeners began with para chlorine removal. All para chlorines from the mono-, di-, and trichlorobiphenyl groups could be removed by sediment slurries from both rivers. Microbial communities in sediment from the Erjen River additionally fostered meta-dechlorination activity, but only after removal of all the para chlorines. Addition of Tween 20 (0.05%, v/v) into sediment slurries from the Tansui River did not enhance dechlorination rates or extents, but the addition of toluene- or 3-chlorobenzoate-adapted sediments enhanced dechlorination of 34-34 CB and 345-4 CB.     

Degradation pathways of PCBs upon UV irradiation in hexane.

The photodegradations of eight individual PCB congeners (5, 31, 52, 77, 87, 126, 138, 169) in hexane have been investigated employing a mercury lamp. All degradation reactions of the above mentioned PCB congeners are of the pseudo first order. The principal products of PCB decomposition are the less chlorinated biphenyls, and no PCB-solvent adducts are found. Symmetrical and coplanar PCB congeners show lower photoreactivities. The reactivities of the chlorine atoms at various positions of PCB rings are generally in the order: ortho > meta > para. Photodechlorinations occur mainly on the more substituted rings, when the numbers of chlorine atoms on the two phenyl rings are unequal. During photodegradation, some coplanar PCB congeners are formed, which make the TEQ of solutions to decrease slowly or even to increase.     

PCDDs, PCDFs, PCBs and HCB in marine and estuarine sediments from Queensland, Australia.

Concentrations of 2,3,7,8-chlorine substituted PCDDs, PCDFs, selected PCB congeners and HCB were determined in sediment samples collected from sites along the east coast of Queensland in northern Australia. PCDDs were detectable in all sediment samples while PCDFs, PCBs and HCB were mainly found in sediment samples collected from sites in the Brisbane metropolitan area. The results provide evidence that an unidentified source for higher chlorinated PCDDs exists along the Queensland coast.     

Synergistic effects of combination of photolysis and ozonation on destruction of chlorophenols in water.

Synergistic effects including TOC elimination, ozone consumption and microtoxicity reduction for combination of photolysis and ozonation compared to those of direct photolysis and ozonation alone on destruction of chlorophenols including 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol were studied. It was found that the synergistic effects of combination of photolysis and ozonation increased obviously with increasing initial pH of solution to basic pH levels. Results showed that the synergistic effects of photolytic ozonation under the conditions imposed was notable with mineralization rate enlarging more than 100%, oxidation index (OI) decreasing 50%, and microtoxicity being reduced by 30%, indicating that the potentialities of photolytic ozonation compared to direct photolysis and ozonation alone was remarkable for treatment of industrial wastewater containing chlorophenols.     

Short-chain fatty acids affect cell-association and invasion of HEp-2 cells by Salmonella typhimurium

This study demonstrates that the growth of S. typhimurium in Luria Bertani broth supplemented with acetate, propionate, butyrate, or a mixture of the three SCFA, affected cell-association and the ability to invade cultured HEp-2 cells. Cell-association and invasion was determined after growth for 4 h of growth in the presence of the SCFA at pH 6 and 7. The results suggest that the growth rate of the culture may have affected cell-association and invasion since accompanying the significant decrease in growth rate in the presence of SCFA at pH 6 was a decrease in cell-association and invasion. However, the results also suggest that the individual SCFA may play a role in modulating cell-association and the invasion phenotype and the regulation of cell-association and invasion by the SCFA was dependent on the concentration and the pH of the medium. Although the growth rates were similar for S. typhimurium in the SCFA mixture, butyrate (100 mM) and propionate (50 mM) at pH 6, differences in cell-association and invasion were observed among these cultures. Also, at pH 7, differences were observed among the SCFA treatments even though the growth rates were similar.     

Interpretation of analytical data on n-alkanes and polynuclear aromatic hydrocarbons in Arbacia lixula from the coasts of Tenerife (Canary Islands, Spain) by multivariate data analysis

The hydrocarbons contents (n-alkanes, polycyclic aromatic hydrocarbons) were determined in the sea urchin Arbacia lixula. Multivariate data analysis as principal component analysis, factor analysis and, cluster analysis were applied to elucidate sources of pollution. PCA and FA were performed to establish the relationships between variables (hydrocarbons), samples (sea urchin) and sources of pollution.