Tissue distribution and excretion of hexabromobenzene (HBB) and hexachlorobenzene (HCB) administered to rats

Tissue distribution and excretion of hexabromobenzene (HBB) and hexachlorobenzene (HCB) were studied in Wister male rats, after oral administration of these chemicals.There was no difference in the amount of two chemicals excreted in feces for seven days. Their absorption rates through intestine were the same. HBB and HCB also were excreted in urine, but their amounts were very low. Therefore, both chemicals seem to be mainly excreted via feces. HBB and HCB were found to be transported rapidly to all tissues, but the concentrations of HCB were higher than those of HBB in all tissues, indicating the rapid metabolism of HBB. This might be due to the lower bonding energy between bromine and carbon atoms (C₆H₆-Br: 71kcal/mol) compared to that of chlorine and carbon atoms (C₆H₆Cl: 86kcal/mol). The half-lives were 0.7 (phase I) and 48 days (phase II) for HBB and 20 days for HCB in whole body. It is noteworthy that the half-life of HBB at phase II is longer than that of HCB.     

Effect of squalane on hexachlorobenzene (HCB) concentrations in tissues of mice

Abstract

Female mice were given 100 mg HCB/kg body weight i.p. and fed diets containing 0, 2.5, 5.0, and 7.5% of squalane. After 3 weeks samples of livar, blood and abdominal fat ware analysed for HCB as well as for squalane. HCB concentrations were significantly lowered as comoared to controls in all tissues and at all dietary concentrations of squalane to a maximum of about 36% in fat, 44% in liver and 47% in blood. The effect of squalane upon HCB concentrations was strongly dose depedent in abdominal fat. In contrast, no significant differences were seen with liver and blood between animals fed 5.0 or 7.5% of squalane. Squalane was detected in considerable amounts in the livers (50–100 ppm) but r.ct in abdominal fat (<1 ppm) of mice fed squalane.     

Sulphur-containing metabolites of the fungicides pentachloronitrobenzene (PCNB) and hexachlorobenzene (HCB) I. Syntheses

Syntheses of sulphur-containing metabolites of the fungicides pentachloronitrobenzene and hexachlorobenzene are described.     

Sulphur-containing metabolites of the fungicides pentachloronitrobenzene (PCNB) and hexachlorobenzene (HCB) II. Mass spectra

Mass spectrometric data of synthesized sulphur-containing derivatives of the fungicides pentachloronitrobenzene (PCNB) and hexachlorobenzene (HCB), such as thiophenols, thioanisoles, disulphides, pentachlorophenylmethylsulphoxide, pentachlorophenylmethylsulphone, and acetylcysteine-conjugates, as well as non sulphur-containing derivatives, such as phenols, pentachloroanisole, and chlorinated benzenes are reported.     

Genotoxicity of the organochlorine pesticides 1,1-dichloro-2,2- bis(p-chlorophenyl)ethylene (DDE) and hexachlorobenzene (HCB) in cultured human lymphocytes

The possible genotoxic potential of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), which is a metabolite of dichlorobiphenyltrichloroetane (DDT), and hexachlorobenzene (HCB), which are organochlorine pesticides have been evaluated in vitro by using human lymphocytes as test system. Genetic damage was determined by scoring the frequency of micronuclei (MN) in primary lymphocyte cultures obtained from different donors. The results indicated that, under the experimental conditions used, the DDT metabolite DDE was able to induce significant increases in the frequency of micronucleated cells, which indicate a certain clastogenic and/or aneugenic potential. DDE was tested in the range of 10-80 mM, but the only concentration producing a significant genotoxic effect was 80 mM. On the other hand, HCB was unable to induce a significant increase in the MN frequency in the range of concentrations assayed, from 0.005 to 0.1mM. The selected concentrations of DDE and HCB were chosen according to their toxicity in cell blood cultures; higher concentrations reduced significantly cell proliferation and produced a low frequency of binucleated cells. In conclusion, the results indicate that a genotoxic risk is associated with the exposure to DDE at concentrations 80 mM and above.     

Emission profiles of polychlorinated dibenzodioxins, polychlorinated dibenzofurans (PCDD/Fs), dioxin-like PCBs and hexachlorobenzene (HCB) from secondary metallurgy industries in Portugal

This paper reports, for the first time, a study of dioxin emissions from 10 siderurgies and metallurgies, secondary copper, aluminum and lead metallurgies, in Portugal. The study reports the emission factors and total emission amounts of PCDD/Fs, dioxin-like PCBs and hexachlorobenzene (HCB). The congener patterns were characterized and are discussed. The results showed that the total amount of PCDFs is higher than PCDDs in flue gas of each industrial unit. The toxic equivalent emission factors of pollutants emitted are 3098-3338 ngI-TEQt(-1) for PCDD/Fs and 597-659 ng I-TEQt(-1) for dioxin-like PCBs in siderurgies production (total estimated emission amounts released to atmosphere of 3.9-4.5 g I-TEQyr(-1)), 50-152 ng I-TEQt(-1) for PCDD/Fs and 24-121 ng I-TEQt(-1) for dioxin-like PCBs in ferrous foundries production (total estimated emission amounts released to atmosphere of 0.0010-0.0016 g I-TEQyr(-1)) and 5.8-5715 ng I-TEQt(-1) for PCDD/Fs and 0.49-259 ng I-TEQt(-1) for dioxin-like PCBs in non-ferrous foundries production (total estimated emission amounts released to atmosphere of 0.00014-0.12 g I-TEQyr(-1)). The HCB emission from siderurgies production is 0.94-3.2 mg t(-1) (total estimated emission amounts released 0.94-3.8 g yr(-1)), being much smaller, residual, in the emissions of the other types of plants (0.0012-0.026 mg t(-1) production and total estimated emission amounts released to atmosphere of 0.013-1.7 mg yr(-1)).     

Acute oral toxicity as LD50 (mg/kg) of propargyl alcohol to male and female rats

Dosages of propargyl alcohol ranging from 0 to 400 mg/kg in 0.5 ml aqueous solutions were administered by gavage to young adult male and female rats of the Sprague-Dawley strain weighing from 180 to 200 g. The treated animals were held 48 hrs at 24 degrees C with food and water ad libitum, after which the dead rats were counted. The oral LD50 was calculated by the probit method (Finney, 1971) as 110 (100-120) mg/kg for male rats and 55 (50-60) mg/kg for female rats.     

N-acetyl-S-(pentachlorophenyl)cysteine,a new urinary metabolite of hexachlorobenzene

The present paper describes the isolation and identification of a new metabolite of hexachlorobenzene (HCB), which is N-acetyl-S-(pentachlorophenyl)cysteine (PCC), frequently named pentachlorophenylmercapturic acid or 2-acetamido-3-(pentachlorophenylmercapto)propionic acid. PCC has been detected in and identified from rat urine. The syntheses of PCC and the isomeric tetrachlorophenylmercapturic acids (TCC) are described in the following paper.     

Synergic effect of calcium oxide and iron (III) oxide on the dechlorination of hexachlorobenzene

Dechlorination of hexachlorobenzene (HCB) was achieved by a mixture of commercial CaO and alpha-Fe2O3 (CaO/alpha-Fe2O3) in closed systems at temperatures of 300 degrees C and 350 degrees C, which exhibited a synergic effect compared to CaO or alpha-Fe2O3 alone, and the dechlorination efficiency was dramatically enhanced. When CaO and alpha-Fe2O3 coexisted, HCB was dechlorinated by about 98% after 0.5 h reaction at 300 degrees C. All TeCB-, TrCB-, and DCB-isomers were detected, showing the presence of more than one dechlorination pathway. The pathway to form 1,2,4-TrCB must be a major pathway because the greatest amount of 1,2,4-TrCB was detected. There existed discrepancy of the material balance between the starting and dechlorinated materials. It implies that besides dechlorination other decomposition processes may be present. The mechanism of synergic effect of calcium and iron oxides was investigated.     

Influence of the chemical structure on mobility of PCB congeners in female and male sardine (Sardina pilchardus) from Portuguese coast

Concentrations of 30 polychlorinated biphenyl congeners (CBs) were determined in muscle, liver and gonad tissues of female and male sardines (Sardina pilchardus) collected in February-May 2000 and September-January 2001 from purse seine vessels operating around Peniche, Portugal. The determined CBs were aggregated in four groups (I, II, III and IV), according to similarities of their chemical structures. Muscle and liver of males contained significantly higher concentrations of groups I and II than females during the final period of spawning (February-April). A less contrast was observed for the groups III and IV. This seasonal fluctuation associated with the spawning indicates that female sardines regulate the excess of CBs sequestrated during fatten period. On the contrary, levels of groups I and II were higher in males than in females indicating slower mobility of these compounds as lipids were consumed during the final period of spawning. The deficient regulation of those CBs in muscle of male sardines can not be attributed to selective transfer to gonads and subsequent excretion. Although the full explanation was not found for the different mobility of PCBs with the gender, the results provide evidence of slower elimination of group I and II congeners in male sardines.     

Metabolism, tissue disposition, and excretion of 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) in male Sprague-Dawley rats

A single oral dose of [14C] 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) was administered to conventional and bile-duct cannulated male Sprague-Dawley rats. Tissue disposition, excretion and metabolism was determined. BTBPE is a low-volume brominated flame retardant used in resins or plastics, and toxicity data in peer-reviewed journals is extremely limited. BTBPE was fairly insoluble in lipophilic solutions, which made dose preparation difficult. The great majority of 14C (>94%) was excreted in the feces of both groups of rats at 72 h, and tissue retention was minimal. Lipophilic tissues contained the highest concentrations of BTBPE, e.g. thymus, adipose tissue, adrenals, lung, and skin. Metabolites were excreted in the urine, bile and feces, but at a very low level. Fecal metabolites were characterized as monohydroxylated, monohydroxylated with debromination, dihydroxylated/debrominated on a single aromatic ring, monohydroxylated on each aromatic ring with accompanying debromination, and cleavage on either side of the ether linkage to yield tribromophenol and tribromophenoxyethanol. Despite a limited quantity of stable metabolites extractable in the feces, non-extractable 14C levels were relatively high (39% of the 0-24 h fecal 14C), which suggested that BTBPE could be metabolically activated in the rat and covalently bound to fecal proteins and/or lipids. It was concluded that limited absorption and metabolism of BTBPE would occur by ingestion in mammals.     

Combined effects of mercury and hexachlorobenzene in the rat

Abstract

The objective of the present study was to assess the potential interactive effects of two Great Lakes chemical contaminants, hexachlorobenzene (HCB) and mercury (HgCl₂). Groups of 10 female Sprague‐Dawley rats were administered by gavage single doses of HCB (400, 600 mg/kg b.w. in corn oil), HgCl₂ (10.0, 12.5 mg/kg b.w. aqueous) or combinations of both followed by observation for clinical signs of toxicity for 14 days. Five animals from treatment groups died before the termination of the study; one animal each in 600 mg HCB, 400 mg HCB + 10 mg HgCl₂, and 600 mg HCB + 10 mg HgCl₂, and two animals in 600 mg HCB + 12.5 mg HgCl₂. The surviving animals were necropsied at the termination of the study, and hematological, clinical chemistry, histopathological and tissue residue analyses were performed. Relative liver weights were increased in both low and high dose groups of HCB but not in animals treated with HgCl₂ alone. Co‐administration of HgCl₂ did not alter the HCB effects on the liver weight of the animals. Serum cholesterol levels were increased in all the groups receiving HCB but not HgCl₂. No interactive effects on other serum parameters were seen in animals administered with both chemicals. Mild to moderate morphological changes occurred in the liver, thyroid, thymus, ovary and bone marrow of rats exposed to HCB or HCB + HgCl₂, and in the kidney of HgCl₂ or HgCl₂ + HCB treated animals. More severe histological changes occurred in the groups receiving both chemicals. The histological effects appeared to be additive. It was concluded that co‐administration with HCB and HgCl₂ resulted in additive effects in some of the endpoints measured but no synergism or antagonism was observed.     

CO(2)-H(2)-dependent anaerobic biotransformation of phthalic acid isomers in sediment slurries

This paper investigates the anaerobic biotransformation of three isomers of phthalic acid and benzoic acid in sediment slurries under four different atmospheres [N(2), N(2)/H(2) (19:1, v/v), CO(2), and CO(2)/H(2) (4:1, v/v)]. Significant differences were observed in lag periods and biotransformation rates among the phthalic acid isomers and under the different atmospheres. In most cases, the relative biotransformation rates of the three isomers of phthalic acid were ortho-phthalic acid>isophthalic acid>terephthalic acid. Benzoate was transformed faster than any isomer of phthalic acid. Since biotransformation of phthalic acid isomers in sediment slurries was enhanced by high initial levels of H(2) and CO(2) in the headspace, we propose a pathway for phthalic acid biodegradation in which the initial transformation to benzoate is CO(2)-H(2) dependent. Acetogenic bacteria were investigated for their possible involvement in this transformation reaction, but when MPN counts were used to compare the growth dynamics of acetogenic bacteria with the time course of the terephthalic acid transformation under N(2)/H(2) (19:1, v/v) and CO(2)/H(2) (4:1, v/v) atmospheres, the results were inconclusive.     

Effects of aging and sediment composition on hexachlorobenzene desorption resistance compared to oral bioavailability in rats

Studies were conducted to assess the effects of black carbon, clay type and aging (1-1.5yr) on desorption and bioavailability of hexachlorobenzene (HCB) in spiked artificial sediments. Tenax (a super sorbent)-mediated desorption was used to examine the effects of these parameters on the physicochemical availability of HCB. The Tenax-mediated desorption of HCB from the four aged artificial sediments exhibited biphasic kinetics. The fast desorbing fractions ranged from 64.8% to 22.3%, showing reductions of 4.0-18.9% compared with freshly-spiked sediments. Statistical analysis on the fast desorbing fractions showed that all three treatment effects (i.e., montmorillonite clay, black carbon content, and aging) were significant. Two sediments with higher black carbon content exhibited much greater aging effects (i.e., greater reduction in fast desorbing fraction) than the other two sediments without the addition of black carbon. For both freshly-spiked and aged sediments, the desorption resistant sediment-bound HCB (i.e., slow desorbing fraction) correlated reasonably well to previously reported rat fecal elimination of HCB, which is a measure of the non-bioavailable fraction of sediment-bound HCB. A similar correlation was also observed between fast desorbing fraction and previously reported accumulation of HCB in the rat body (carcass+skin). These observations suggest that physicochemical availability, as defined by the desorption of HCB from sediments, provides a reasonable prediction of the oral bioavailability of sediment-bound HCB to rats. These results showed that montmorillonite clay, black carbon and aging reduced physicochemical availability and ultimately bioavailability of sediment-bound HCB.     

Effects of hexachlorobenzene on antioxidant status of liver and brain of common carp (Cyprinus carpio)

Hexachlorobenzene (HCB)-induced oxidative damages have been published in rats while the effects have not yet been reported in fishes. Juvenile common carps (Cyprinus carpio) were exposed to waterborne HCB from 2 to 200 microg l-1 for 5, 10 or 20 days. Liver and brain were analyzed for various parameters of oxidative stress. There were no significant changes of glutathione (GSH) content and superoxide dismutase (SOD) activity in liver after 5 or 10 days exposure, whereas obvious drops were observed at higher concentrations after 20 days exposure. Significant decreases of GSH content and SOD activity in brain were found during all the exposure days. In brain, HCB also significantly elevated the contents of reactive oxygen species (ROS), thiobarbituric acid- reactive substances (TBARS, as an indicator of lipid peroxidation products), glutathione disulfide (GSSG), and activities of nitric oxide synthase (NOS), glutathione peroxidase (GPx), and glutathione reductase (GR), and inhibited activities of acetylcholinesterase (AchE) and glutathione S-transferase (GST). The results clearly demonstrated that environmentally possible level of HCB could result in oxidative stress in fish and brain was a sensitive target organ of HCB toxicity.     

Bioaccumulation, depuration and biotransformation of 4,4'-dibromodiphenyl ether in crucian carp (Carassius auratus)

Polybrominated diphenyl ethers (PBDEs) are extensively used as a class of flame retardants and have become ubiquitous environmental pollutants. Significant biotransformation of some PBDEs via reductive debromination has been observed. However, little is known about the fate of lower brominated BDEs in fish. In this study, the tissue distribution, excretion, depuration and biotransformation of 4,4′-dibromodiphenyl ether (BDE 15) were investigated in crucian carp (Carassius auratus) which were exposed to spiked water solution at different concentrations for 50 d, followed by a 14-d depuration period. Bioaccumulation parameters were calculated and the results showed that BDE 15 was mainly concentrated in the gill and liver. In particular, five biotransformation products of BDE 15 in carp were identified using GC-MS/MS. Besides two debrominated metabolites, three of the metabolites were mono-OH-BDE 15, diOH-BDE 15 and bromophenol. Our results unequivocally suggested that BDE 15 oxidation did occur via the formation of hydroxylated (OH-) metabolites in crucian carp exposed in vivo. These findings will be useful for determination of the metabolic pathways of PBDEs in freshwater fish, especially about their oxidation metabolism.     

Comparision of the waterborne and dietary routes of exposure on the effects of Benzo(a)pyrene on biotransformation pathways in Nile tilapia (Oreochromis niloticus)

BaP is one of the most studied PAH, due to its ubiquitous presence in aquatic environments and toxicity to aquatic organisms. The main goal of this study was to assess BaP effects in Nile Tilapia after waterborne and dietary exposures, through the evaluation of EROD and GST activities in liver, gills and intestine, and BaP metabolites in bile; and also to evaluate the usefulness of these commonly used biomarkers after two different routes of exposure. Waterborne exposure to BaP led to a significant induction of EROD in all tissues analyzed (644%, 1640% and 2880% in relation to solvent in liver, gill and intestine respectively) while in dietary exposures EROD was induced only in intestine (3143%) after exposure to high BaP concentrations. GST activities with CDNB were slightly induced in liver (40%) and in gill (66%) after water exposure to BaP, and in intestine after dietary exposure to low BaP concentrations (182%). BaP metabolites in bile increased after both exposure routes, and were highly correlated with EROD activity after water exposure. In summary, this work has shown that the effects of BaP on biotransformation pathways depend on the route of exposure. Moreover, barrier tissues like gills and intestine also have an important role in the first-pass metabolism of BaP, reducing the amount of parent compound that reaches the liver to be metabolized. For that reason, EROD activity as a biomarker of exposure should also be applied in extrahepatic organs, like gills and intestine, in monitoring studies. Biliary BaP type metabolites are good reflectors of contamination levels under both exposure routes, while GST activity with CDNB as substrate, as a phase II enzyme, does not seem a reliable biomarker of exposure to BaP regardless the route of exposure.