Varying temporal trends in the levels of six groups of legacy persistent organic pollutants (POPs) in liver of three gadoid species from the North Sea.

From 2005 to 2019, three gadoid species, Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and saithe (Pollachius virens), were sampled approximately every third year in the northeastern part of the North Sea. Liver samples were analyzed to investigate levels and temporal trends of six groups of persistent organic pollutants (POPs): polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and its degradation products, hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), trans-nonachlor (TNC), and polybrominated diphenyl ethers (PBDEs). Some of the highest average concentrations were found in cod, the levels otherwise being similar between the three species and mostly below established threshold values. The levels of all the contaminants except HCB and TNC were higher than previously reported for cod and haddock in the Barents Sea. Significantly decreasing levels were found for Σ7PCBs, ΣDDTs, ΣHCHs and Σ15PBDEs in all three species, and for TNC in haddock and saithe, while there was no significant trend for TNC in cod. HCB levels increased significantly in cod and haddock and showed only a minor decrease in saithe. The observed time trends of legacy POPs demonstrate the persistence of some of the studied pollutants despite efforts to eliminate them from the marine environment.

The deep dive of organohalogen compounds: Bioaccumulation in the top predators of mesopelagic trophic webs, pygmy and dwarf sperm whales, from the Southwestern Atlantic ocean.

Kogia sima and Kogia breviceps are apex predators of mesopelagic trophic webs being far from most anthropogenic threats. However, chemical pollutants and naturally synthesized compounds may travel long distances. This study aimed to use kogiid whales as sentinels of mesopelagic trophic webs in the Southwestern Atlantic Ocean. Persistent organic pollutants (POPs), e.g., polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and metabolites, mirex, hexachlorobenzene (HCB), polybrominated diphenylethers (PBDEs), pentabromoethylbenzene (PBEB) and hexabromobenzene (HBB), and the naturally produced methoxylated BDE (MeO-BDEs) were determined in the blubber of 16 K. sima and 15 K. breviceps. Among the organochlorine compounds, DDTs were the main group found in K. sima and in K. breviceps (1636.6 and 3983.3 ng g-1 lw, respective medians), followed by PCBs (425.9 and 956.1 ng g-1 lw, respectively), mirex (184.1 and 375.6 ng g-1 lw, respectively), and HCB (132.4 and 340.3 ng g-1 lw, respectively). As for the organobromine, the natural MeO-BDEs were predominant (1676.7 and 501.6 ng g-1 lw, respectively), followed by PBDEs (13.6 and 10.3 ng g-1 lw, respectively) and PBEB (2.2 and 2.9 ng g-1 lw, respectively). In general, POPs concentration was higher in K. breviceps than in K. sima. Conversely, MeO-BDEs concentration was higher in K. sima than in K. breviceps. Differences in concentrations in these sympatric odontocetes were attributed to distinct species, sampling sites, and biological parameters and suggest some level of niche segregation. It is noteworthy the long-range reach and bioaccumulation of these synthetic compounds in an unexplored habitat, that present an increasing economic interest.

Fe2O3 micron particles are critical for electron transfer and the distribution of electrochemically active bacteria in soil MFCs.

Fe2O3 plays a complex role in soil electron transfer. A microbial fuel cell (MFC) was constructed to drive the directional transfer of electrons in soil, and the results revealed that Fe2O3 acts first as a capacitor, intercepting and reserving the electrons produced by electrochemically active bacteria (EAB) in the soil, which leads to a decrease in hexachlorobenzene (HCB) removal efficiency with increasing proportions of Fe2O3 dosing (R2 = 0.85). The Fe2O3 then exerted its semiconductor properties in synergy with dissolved Fe2+ as an electron mediator to promote the flow of electrons in the soil. Power generation by the MFC was significantly and positively correlated with the concentration of dissolved Fe2+ (r = 0.51) and the Fe2O3 dosing proportion (r = 0.97). The higher HCB removal efficiency, spatial distribution of intercepted electrons, and abundance of electron transfer metabolic pathways confirmed that Fe2O3 promoted electron-flow fluxes in soil. Additionally, Geobacter sp., (direct electron transfer) and Pseudomonas sp., (indirect electron transfer) were the dominant electrochemically active bacteria in the anode and soil of MFC, respectively. In this study, both dissolved (Fe2+) and solid state (Fe2O3) electron mediators functioned as electron transporters in soil, we propose an internal "electron internet" of soil consisting of points and lines.

Investigation of obesogenic effects of hexachlorobenzene, DDT and DDE in male rats.

Obesity has become a very important public health problem and is increasing globally. Genetics, individual and environmental factors play roles in the etiology of this complex disorder. Recently, several environmental pollutants have been suggested to have obesogenic activities. Peroxisome proliferator activating receptor gamma (PPARγ), uncoupling protein-1 (UCP1) and their expression in white adipose tissue (WAT) and brown adipose tissue (BAT) play key roles in adipogenesis. UCP3 and irisin were reported to play roles in non-shivering thermogenesis. Our primary aim was to investigate obesogenic effects of hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) in rats. In addition, thermoregulatory effects of HCB, DDT and DDE were also investigated by analyzing the levels of Ucp3 and irisin. Thirty-two adult male Sprague-Dawley rats were randomly divided into four groups as control, HCB, DDT and DDE. Animals were administered with organochlorine pesticides (OCPs; 5 mg/kg bw) by oral gavage every other day for five weeks. At the end of the experimental period, the animals were sacrificed, BAT and WAT samples were collected to analyze Pparγ, Ucp1 and Ucp3 levels. Moreover, skeletal muscle samples were collected to examine Ucp3 and irisin levels. Serum glucose, cholesterol and triglyceride levels were also determined. Body weight and core temperature of the animals were not significantly affected by any of the OCP administration. Serum glucose, cholesterol and triglyceride levels were similar among the experimental groups. Pparγ expression was significantly elevated by HCB administration only in WAT (p < 0.05). On the other hand, both Pparγ and Ucp1 expressions were diminished in WAT and BAT (p < 0.01) by DDT treatment, while in WAT, DDE significantly decreased Pparγ expression without altering its expression in BAT (p < 0.001). Ucp3 and irisin levels in skeletal muscle were not altered. Our findings show that both DDT and DDE reduce the browning of WAT by suppressing white adipocytes and thus may have obesogenic activity in male rats without altering thermoregulation. In addition, HCB, DDT and DDE-induced alterations in expression of Pparγ and Ucp1 in WAT implicates differential regulation of adipogenic processes.

Manganese mitigates against hepatorenal oxidative stress, inflammation and caspase-3 activation in rats exposed to hexachlorobenzene.

The present study investigated the individual and collective effect of organochlorinated fungicide hexachlorobenzene (HCB) and manganese (Mn), a metal, on the hepatorenal function in adult rats. Rats were divided into four groups of rats comprising of control, HCB alone (15 mg/kg), Mn alone (10 mg/kg) and co-exposure group that were orally treated for 25 consecutive days. After sacrifice, hepatorenal damage and antioxidant status markers, myeloperoxidase (MPO) activity, levels of nitric oxide, total antioxidant capacity (TAC), total oxidative stress (TOS) and lipid peroxidation (LPO) were analyzed spectrophotometrically. Levels of tumor necrosis factor alpha (TNF-α), interleukin-1 ß (IL-1ß) and caspase-3 activity were assessed using ELISA. Results revealed that the HCB administration significantly (p < 0.05) increased the biomarkers of hepatorenal toxicity, decreased the antioxidant status and TAC, raised the levels of TOS and LPO as well as increased the levels of TNF-α, IL-1ß and caspase-3 activity. Rats co-exposed to HCB and Mn showed decreased biomarkers of hepatorenal damage, increased antioxidant status and TAC with simultaneous reduction in the levels of TOS and LPO significantly (p < 0.05). Furthermore, the increased levels of TNF-α, IL-1ß and caspase-3 activity were significantly (p < 0.05) reduced in the liver and kidney of rats' co-expose to HCB and Mn. Histological examination showed that damages induced by HCB were assuaged in rats co-treated with HCB and Mn. In conclusion, the results demonstrated that co-treatment of HCB and Mn in rats' alleviated HCB-induced oxidative stress, inflammation and caspase-3 activation in the liver and kidney of the rats.

Hexachlorobenzene Monooxygenase Substrate Selectivity and Catalysis: Structural and Biochemical Insights.

Hexachlorobenzene (HCB), as one of the persistent organic pollutants (POPs) and a possible human carcinogen, is especially resistant to biodegradation. In this study, HcbA1A3, a distinct flavin-N5-peroxide-utilizing enzyme and the sole known naturally occurring aerobic HCB dechlorinase, was biochemically characterized. Its apparent preference for HCB in binding affinity revealed that HcbA1 could oxidize only HCB rather than less-chlorinated benzenes such as pentachlorobenzene and tetrachlorobenzenes. In addition, the crystal structure of HcbA1 and its complex with flavin mononucleotide (FMN) were resolved, revealing HcbA1 to be a new member of the bacterial luciferase-like family. A much smaller substrate-binding pocket of HcbA1 than is seen with its close homologues suggests a requirement of limited space for catalysis. In the active center, Tyr362 and Asp315 are necessary in maintaining the normal conformation of HcbA1, while Arg311, Arg314, Phe10, Val59, and Met12 are pivotal for the substrate affinity. They are supposed to place HCB at a productive orientation through multiple interactions. His17, with its close contact with the site of oxidation of HCB, probably fixes the target chlorine atom and stabilizes reaction intermediates. The enzymatic characteristics and crystal structures reported here provide new insights into the substrate specificity and catalytic mechanism of HcbA1, which paves the way for its rational engineering and application in the bioremediation of HCB-polluted environments.IMPORTANCE As an endocrine disrupter and possible carcinogen to human beings, hexachlorobenzene (HCB) is especially resistant to biodegradation, largely due to difficulty in its dechlorination. The lack of knowledge of HCB dechlorinases limits their application in bioremediation. Recently, an HCB monooxygenase, HcbA1A3, representing the only naturally occurring aerobic HCB dechlorinase known so far, was reported. Here, we report its biochemical and structural characterization, providing new insights into its substrate selectivity and catalytic mechanism. This research also increases our understanding of HCB dechlorinases and flavin-N5-peroxide-utilizing enzymes.

Angiogenesis signaling in breast cancer models is induced by hexachlorobenzene and chlorpyrifos, pesticide ligands of the aryl hydrocarbon receptor.

Breast cancer incidence is increasing globally and pesticides exposure may impact risk of developing this disease. Hexachlorobenzene (HCB) and chlorpyrifos (CPF) act as endocrine disruptors, inducing proliferation in breast cancer cells. Vascular endothelial growth factor-A (VEGF-A), cyclooxygenase-2 (COX-2) and nitric oxide (NO) are associated with angiogenesis. Our aim was to evaluate HCB and CPF action, both weak aryl hydrocarbon receptor (AhR) ligands, on angiogenesis in breast cancer models. We used: (1) in vivo xenograft model with MCF-7 cells, (2) in vitro breast cancer model with MCF-7, and (3) in vitro neovasculogenesis model with endothelial cells exposed to conditioned medium from MCF-7. Results show that HCB (3 mg/kg) and CPF (0.1 mg/kg) stimulated vascular density in the in vivo model. HCB and CPF low doses enhanced VEGF-A and COX-2 expression, accompanied by increased levels of nitric oxide synthases (NOS), and NO release in MCF-7. HCB and CPF high doses intensified VEGF-A and COX-2 levels but rendered different effects on NOS, however, both pesticides reduced NO production. Moreover, our data indicate that HCB and CPF-induced VEGF-A expression is mediated by estrogen receptor and NO, while the increase in COX-2 is through AhR and NO pathways in MCF-7. In conclusion, we demonstrate that HCB and CPF environmental concentrations stimulate angiogenic switch in vivo. Besides, pesticides induce VEGF-A and COX-2 expression, as well as NO production in MCF-7, promoting tubulogenesis in endothelial cells. These findings show that pesticide exposure could stimulate angiogenesis, a process that has been demonstrated to contribute to breast cancer progression.

AhR ligands reactivate LINE-1 retrotransposon in triple-negative breast cancer cells MDA-MB-231 and non-tumorigenic mammary epithelial cells NMuMG.

Breast cancer is the most common cancer type in females worldwide. Environmental exposure to pesticides affecting hormonal homeostasis does not necessarily induce DNA mutations but may influence gene expression by disturbances in epigenetic regulation. Expression of long interspersed nuclear element-1 (LINE-1) has been associated with tumorigenesis in several cancers. In nearly all somatic cells, LINE-1 is silenced by DNA methylation in the 5́'UTR and reactivated during disease initiation and/or progression. Strong ligands of aryl hydrocarbon receptor (AhR) activate LINE-1 through the transforming growth factor-ß1 (TGF-ß1)/Smad pathway. Hexachlorobenzene (HCB) and chlorpyrifos (CPF), both weak AhR ligands, promote cell proliferation and migration in breast cancer cells, as well as tumor growth in rat models. In this context, our aim was to examine the effect of these pesticides on LINE-1 expression and ORF1p localization in the triple-negative breast cancer cell line MDA-MB-231 and the non-tumorigenic epithelial breast cell line NMuMG, and to evaluate the role of TGF-ß1 and AhR pathways. Results show that 0.5 µM CPF and 0.005 µM HCB increased LINE-1 mRNA expression through Smad and AhR signaling in MDA-MB-231. In addition, the methylation of the first sites in 5́'UTR of LINE-1 was reduced by pesticide exposure, although the farther sites remained unaffected. Pesticides modulated ORF1p localization in MDA-MB-231: 0.005 µM HCB and 50 µM CPF increased nuclear translocation, while both induced cytoplasmic retention at 0.5 and 5 µM. Moreover, both stimulated double-strand breaks, enhancing H2AX phosphorylation, coincidentally with ORF1p nuclear localization. In NMuMG similar results were observed, since they heighten LINE-1 mRNA levels. CPF effect was through AhR and TGF-ß1 signaling, whereas HCB action depends only of AhR. In addition, both pesticides increase ORF1p expression and nuclear localization. Our results provide experimental evidence that HCB and CPF exposure modify LINE-1 methylation levels and induce LINE-1 reactivation, suggesting that epigenetic mechanisms could contribute to pesticide-induced breast cancer progression.

Bioconcentration factors for hydrocarbons and petrochemicals: Understanding processes, uncertainty and predictive model performance.

Fish bioconcentration factors (BCFs) are often used to assess substance-specific bioaccumulation. However, reliable BCF data are limited given the practical challenges of conducting such tests. The objectives of this paper are to describe nine rainbow trout studies performed in our lab using tailored dosing and test designs for obtaining empirical BCFs for 21 test substances; gain insights into the structural features and processes determining the magnitude and uncertainty in observed BCFs; and assess performance of six quantitative structure property relationships (QSPRs) for correctly categorizing bioaccumulation given current regulatory triggers. Resulting mean steady-state BCFs, adjusted to a 5% lipid content, ranged from 12 Lkg-1 for isodecanol to 15,448 Lkg-1 for hexachlorobenzene which served as a positive control. BCFs for hydrocarbons depended on aromatic and saturated ring configurations and position. Uptake clearances appeared to be modulated by gill metabolism and substance bioavailability, while elimination rates were likely influenced by somatic biotransformation. Current approaches for quantifying uncertainty in experimental BCFs, which take into account only variability in measured fish concentrations, were found to underestimate the true uncertainty in this endpoint with important implications for decision-making. The Vega (KNN/Read-Across) QSPR and Arnot-Gobas model yielded the best model performance when compared to measured BCFs generated in this study.

Effects of migration and reproduction on the variation in persistent organic pollutant levels in Kentish Plovers from Cangzhou Wetland, China.

Migratory Birds have been considered biovectors of persistent organic pollutants (POPs) from sources to remote areas. In the present study, Kentish Plovers (Charadrius alexandrines) were collected in different periods, including immigration, breeding and emigration, to investigate the effects of migration and reproduction on POP variations in this bird species. Significant differences were found for dichlorodiphenyltrichloroethane (DDT) and hexachlorobenzene (HCB) concentrations in muscles between the immigration and emigration periods (p < 0.01 and p < 0.001, respectively), which could be attributed to the higher pesticide residues in the wintering grounds of plovers. Female plovers could excrete about 20.8-42.7% of POP load into eggs. Nevertheless, the POP levels didn't exhibit great reduction during the breeding period compared with other seasons, which suggested that the breeding status had little impact on POP levels in female plovers. The estimated mean transport masses of POPs driven by plover migration were at the milligram level (range: 0.02-7.05 mg), suggesting that the migration of plovers had limited impacts on the redistributions of POPs along their migratory routes.

Hexachlorobenzene Catabolism Involves a Nucleophilic Aromatic Substitution and Flavin-N5-Oxide Formation.

HcbA1 is a unique flavoenzyme that catalyzes the first step in the bacterial hexachlorobenzene catabolic pathway. Here we report in vitro reconstitution of the HcbA1-catalyzed reaction. Detailed mechanistic studies provide evidence for nucleophilic aromatic substitution and flavin-N5-oxide formation.

An evaluation of the levels of organochlorine compounds (OCPs and PCBs) in cultured freshwater and wild sea fish eggs as an exposure biomarker for environmental contamination.

In this study, the eggs of 30 wild Black Sea whiting (Merlangius merlangus euxinus, Nordmann, 1840) and 30 farmed freshwater rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) collected from Samsun Province in Turkey were analyzed to determine the level of contamination by nine organochlorine pesticides (OCPs), namely α-hexachlorocyclohexane (α-HCH), ß-HCH, γ-HCH (lindane), hexachlorobenzene (HCB), aldrin, 2,4'-dichlorodiphenyltrichloroethane (DDT), 4,4'-DDT, 2,4'-dichlorodiphenyldichloroethylene (DDE), 4,4'-DDE, and 15 polychlorinated biphenyls (PCBs) (PCB-28, -70, -74, -81, -99, -101, -118, -138, -153, -156, -170, -180, -183, -187, and -208), and their potential use as biomarkers to monitor levels of environmental contamination. OCPs and PCBs in the fat of fish eggs were extracted cryogenically and their concentrations were determined with a gas chromatography-electron capture detector (GC-ECD). The whiting eggs showed high OCP and PCB levels compared to the rainbow trout eggs. The median ∑ DDT values for whiting and rainbow trout eggs were 1601.62 ng g-1 fat (range 824.87-5049.81) and 406.49 ng g-1 fat (range 199.88-588.82); median ∑Indicator PCBs were 1264.24 ng g-1 fat (range 520.05-6140.32) and 82.11 ng g-1 fat (range 2.85-215.97); and median ∑ HCHs were 155.66 ng g-1 fat (range 35.45-330.40) and 13.48 ng g-1 fat (range 4.44-66.44), respectively. In the whiting eggs, the ∑Indicator PCB level was above the maximum residue limit (MRL) of 200 ng g-1 fat stated in the European Commission Regulation (EC) and Turkish Food Codex (TFC). In addition, there was a significant difference between the contamination levels of the eggs of the two species. In conclusion, it appears that fish eggs can serve as a valuable biomarker for the level of contamination of persistent organochlorine contaminants in different aquatic environments.

The effect of redox capacity of humic acids on hexachlorobenzene dechlorination during the anaerobic digestion process.

Hexachlorobenzene (HCB) dechlorination affected by humic acids (HA) was evaluated in terms of HA redox capacity, HA concentrations, and microbial community, as well as the correlation between HA redox capacity values and HCB concentrations. With addition of HA in the initial stage, redox capacity values increased by 2.19 meq/L (80 mg/L of HA addition, HA80), 2.51 meq/L (120 mg/L of HA addition, HA120), and 3.64 meq/L (200 mg/L of HA addition, HA200), respectively. The addition of HA could prominently enhance the HCB degradation rate. However, the concentration and the redox capacity of HA decreased during the anaerobic digestion process. Illumina MiSeq sequencing showed that microbial community affected by HA. Bacillus, Comamonas, and Pseudomonas were the predominant genera during the HCB dechlorination treatment. Moreover, Bacillus and Pseudomonas can improve HA electron transfer capability and promote the dechlorination of HCB.

First assessment of persistent organic pollutant contamination in blubber of Chilean blue whales from Isla de Chiloé, southern Chile.

Persistent organic pollutants (POPs) were assessed for the first time in blue whales from the South Pacific Ocean. Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB) and dichlorodiphenyltrichloroethane and its main metabolites (DDTs), were determined in 40 blubber samples from 36 free-ranging individuals and one stranded, dead animal along the coast of southern Chile between 2011 and 2013. PCBs were the most abundant pollutants (2.97-975 ng/g l.w.), followed by DDTs (3.50-537 ng/g l.w.), HCB (nd-77.5 ng/g l.w.) and PBDEs (nd-33.4 ng/g l.w). There was evidence of differences between sexes, with lower loads in females potentially due to pollutants passing to calves. POP concentrations were higher in specimens sampled in 2013; yet, between-year differences were only statistically significant for HCB and PBDEs. Lower chlorinated (penta > tetra > tri) and brominated (tetra > tri) congeners were the most prevalent among PCBs and PBDEs, respectively, mostly in agreement with findings previously reported in blue and other baleen whales. The present study provides evidence of lower levels of contamination by POPs in eastern South Pacific blue whales in comparison to those reported for the Northern Hemisphere.

Bioaccumulation and human health risks of OCPs and PCBs in freshwater products of Northeast China.

The levels and spatial distribution of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in freshwater products from Northeast China were investigated by gas chromatography coupled to isotope dilution high-resolution mass spectrometry. All samples were on-spot sampled from main production regions of freshwater products in Northeast China, and these samples were used to systematically assess the potential health risks of OCPs and PCBs associated with consumption of these fishery products. Dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexane (HCHs), hexachlorobenzene (HCB) and PCBs were the major pollutants with 100% detection rates, and their levels ranged from 0.086 to 58, 0.038-3.3, 0.093-4.5 and 0.032-1.4 ng g-1 wet weight, respectively. The estimated dietary intakes of these contaminants were all below their corresponding acceptable daily intakes. Significant regional differences in the levels of OCPs and PCBs (P ≦ 0.001) were found in samples from Liaoning and Inner Mongolia. The results showed that the concentrations of targeted contaminants in aquatic products had species-specific characteristics, and the levels of targeted pollutants in Oncorhynchus mykiss and Eriocheir sienesis were significantly higher than those in other aquatic product species. Advisories on ten species of aquatic products suggested that consumption of Eriocheir sinensis, Oncorhynchus mykiss and Cyprinus carpio at a rate exceeding 15 meals per month would pose a cancer risk. A health risk assessment indicated that exposure to these pollutants through freshwater products consumption would cause a non-ignorable potential carcinogenic risk to humans.

Excretion kinetics of three dominant organochlorine compounds in human milk within the first 6 months postpartum.

Breastfeeding is a specific and important way for women to eliminate harmful substances accumulated in body. Hexachlorobenzene (HCB), ß-hexachlorocyclohexane (ß-HCH), and 2,2-bis(p-chlorophenyl)-1,1-dichloroethene (p,p'-DDE) are dominant organochlorine compounds(OCCs) and persistent organic pollutants (POPs) accumulated in human being. Although a 6-month breastfeeding was suggested by the World Health Organization (WHO), the excretion characteristics of OCCs in human milk during the first 6-month lactation remain controversial. The main purpose of this study was to continuously monitor the three dominant OCC concentrations and reveal their elimination characteristic in human milk within the first 6-month lactation. To do that, with one sample per month, during their first 6-month lactation, human milk samples were continuously collected from 40 mothers after their first birth. The result showed that the concentrations of the three OCCs in human milk during the lactation continuously decreased from 51.7 to 39.9 µg/kg milk lipids for HCB, from 136.5 to 84.8 µg/kg milk lipids for ß-HCH, and from 307.3 to 192 µg/kg milk lipids, respectively. The excretion kinetics of each compound in milk lipids fitted zero-order kinetics during the 6-month lactation. The excretion rate of the three OCCs was approximately 3% per month for HCB and 7% per month for the other two compounds during the lactation, with tdec 1/2 of 13 months for HCB, 7.5 months for ß-HCH, and 8 months for p,p'-DDE. The excretion rate of the target compounds depended on initial deposited levels, compound properties, and exposure or input source.

Vitamin D3 supplementation attenuates the early stage of mouse hepatocarcinogenesis promoted by hexachlorobenzene fungicide.

Hexachlorobezene (HCB), a fungicide widely distributed in the environment, promotes the development of hepatocellular preneoplastic lesions (PNL) and tumors in rodents. In contrast, vitamin D3 (VD3) supplementation presents a potential role for the prevention/treatment of chronic liver diseases. Thus, we investigated whether VD3 supplementation attenuates the early stage of HCB-promoted hepatocarcinogenesis. Female Balb/C mice were injected a single dose of diethylnitrosamine (DEN, 50 mg/kg) at postnatal day 15. From day 40 onwards, mice were fed with a standard diet containing 0.02% HCB alone or supplemented with VD3 (10,000 or 20,000 IU/Kg diet) for 20 weeks. Untreated mice were fed just standard diet. After this period, mice were euthanized and liver and serum samples were collected. Compared to the untreated group, DEN/HCB treatment decreased total hepatic glutathione levels and glutathione peroxidase (GSH-Px) activity while increased lipid peroxidation, p65 protein expression, cell proliferation/apoptosis and the PNL development. In contrast, dietary VD3 supplementation enhanced vitamin D receptor (VDR) protein expression, total glutathione levels and GSH-Px activity while diminished lipid hydroperoxide levels. Also, VD3 supplementation decreased p65 protein expression, hepatocyte proliferation, the size and the liver area occupied by PNL. Therefore, our findings indicate that VD3 supplementation attenuates the early stage of HCB-promoted hepatocarcinogenesis.

Organohalogenated contaminants in plasma and eggs of rockhopper penguins: Does vitellogenin affect maternal transfer?

Although many studies have investigated organohalogenated contaminants (OHCs) in yolk, little is known about the mechanisms and timing of transfer of OHCs from the female to the egg. Vitellogenin, a yolk precursor, has been suggested to play a role in this transport. We here report for the first time the temporal changes in OHC and an index of vitellogenin concentrations in female plasma from the pre-laying period to clutch completion in free-living birds: the southern rockhopper penguin (Eudyptes chrysocome chrysocome) breeding in the Falkland/Malvinas Islands. In addition, OHC concentrations in the corresponding clutches were analysed. OHC concentrations in female plasma and in the yolk of both the first (A-) and the second (B-)eggs followed a similar pattern, with hexachlorobenzene (HCB) > Σpolychlorinated biphenyls (PCBs) > Σdichlorodiphenyltrichloroethanes (DDTs) > Σmethoxylated polybrominated diphenyl ethers (MeO-PBDEs) > Σchlordanes (CHLs) > Σpolybrominated diphenyl ethers (PBDEs) ≈ Σhexachlorocyclohexanes (HCHs). The higher concentrations of MeO-PBDEs compared to PBDEs indicate a diet containing naturally-produced MeO-PBDEs. All OHC compounds except for PBDEs increased from the pre-laying period to A-egg laying and subsequently declined from A-egg laying to B-egg laying, and female plasma vitellogenin showed the same pattern. For ΣPCBs and ΣMeO-PBDEs, we found positive correlations between female plasma during A-egg laying and both eggs, and for HCB between female plasma and A-eggs only. During pre-laying, only ΣMeO-PBDEs correlated between both eggs and female plasma, and no correlations between OHC concentrations in eggs and female plasma were found during B-egg laying, highlighting that maternal transfer of OHCs is time- and compound-specific. Finally, female vitellogenin concentrations did not significantly correlate with any OHC compounds in either female plasma or eggs, and our results therefore did not confirm the suggested role of vitellogenin in the maternal transfer of OHC molecules into their eggs.

An approach to biodegradation of chlorobenzenes: combination of Typha angustifolia and bacterial effects on hexachlorobenzene degradation in water.

Although rhizoremediation is an effective approach to remove organic pollutants from the environment, little is known about the mechanism of hexachlorobenzene (HCB) biodegradation in water. In this study, we used Typha angustifolia (T. angustifolia) grown in sterile Hoagland nutrient solution to determine the rhizosphere effects on the ability of bacteria in water to reduce HCB levels. The results revealed that T. angustifolia could facilitate HCB degradation and that the initial HCB concentration was the major factor responsible for HCB degradation in nutrient solution. Furthermore, HCB biodegradation in low-HCB nutrient solution with T. angustifolia fitted the first-order kinetics, owing to the high concentration of total organic carbon, low HCB toxicity, and unique bacterial community in the T. angustifolia rhizosphere. Denaturing gradient gel electrophoresis indicated that the rhizosphere effects and different dosages of HCB have significant effects on the bacterial communities by repressing and favoring certain populations. The most successful bacteria to adapt to HCB contamination was Bacillus sp., while the dominant bacterial phyla in HCB-polluted water were Proteobacteria and Firmicutes.

Bioaccumulation of hexachlorobenzene in the terrestrial isopod Porcellio scaber.

A test system to investigate the biomagnification of organic chemicals in the terrestrial isopod Porcellio scaber was developed and validated. Adult isopods were fed on alder leaf powder (Alnus glutinosa) spiked with [14 C]hexachlorobenzene (HCB). Test animals, sampled regularly during the uptake (16 d) and depuration phases (16 d), were analyzed, and the kinetics of tissue concentrations were determined. Uptake (k1 ) and depuration rates (k2 ) were calculated to estimate kinetic biomagnification factors (BMFs). In addition, the effect of coprophagy on the uptake and accumulation of HCB as well as the tissue distribution of HCB in P. scaber was investigated. The test system was shown to be suitable for investigations into the terrestrial bioaccumulation of chemicals. Coprophagy had no effect on the bioaccumulation of HCB in P. scaber. The hepatopancreas was identified as the main target tissue for HCB accumulation. The low BMF of 0.057 resulted from an assimilation efficiency (α) of 31.42%, a low uptake rate k1 (0.009 d-1 ), and a high depuration rate k2 (0.164 d-1 ). The results indicate that the terrestrial bioaccumulation of organic chemicals in P. scaber might not represent a worst-case scenario for biomagnification, limiting the value of the test system for the regulatory assessment of organic chemicals. Environ Toxicol Chem 2016;35:2867-2873. © 2016 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC.