The aryl hydrocarbon receptor (AhR) plays an important role in mediating dioxins toxicity. Currently, genes of P450 families are major research interests in studies on AhR-mediated gene alterations caused by dioxins. Genes related to other metabolic pathways or processes may be also responsive to dioxin exposures. Amino acid transporter B0AT1 (encoded by SLC6A19) plays a decisive role in neutral amino acid transport which is present in kidney, intestine and liver. However, effects of dioxins on its expression are still unknown. In the present study, we focused on the effects of dioxin and dioxin-like compounds on SLC6A19 expression in HepG2 cells. We identified SLC6A19 as a novel putative target gene of AhR activation in HepG2 cells. 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) increased the expression of SLC6A19 in time- and concentration-dependent manners. Using AhR antagonist CH223191 and/or siRNA assays, we demonstrated that certain AhR agonists upregulated SLC6A19 expression via AhR, including TCDD, 1,2,3,7,8-pentachlorodibenzo-p-dioxin (1,2,3,7,8-PeCDD), 2,3,4,7,8- pentachlorodibenzofuran (2,3,4,7,8-PeCDF) and PCB126. In addition, the expression of B0AT1 was also significantly induced by TCDD in HepG2 cells. Our study suggested that dioxins might affect the transcription and translation of SLC6A19 in HepG2 cells, which might be a novel putative gene to assess dioxins' toxicity in amino acid transport and metabolism in liver.

Productive coastal and estuarine habitats can be degraded by contaminants including persistent organic pollutants (POPs) such as PCBs, dioxins, and organochlorine insecticides to the extent of official designation as contaminated sites. Top-predatory wildlife may continue to use such sites as the habitat often appears suitable, and thus bioaccumulate POPs and other contaminants with potential consequences on their health and fitness. Victoria and Esquimalt harbours are located on southern Vancouver Island, British Columbia (BC) and are federally designated contaminated sites due mainly to past heavy industrial activities, such as from shipyards and sawmills. We collected scat samples from river otters (Lontra canadensis) throughout an annual cycle, and combined chemical analysis with DNA genotyping to examine whether the harbour areas constituted a contaminant-induced ecological trap for otters. We confirmed spatial habitat use by radio telemetry of a subsample of otters. Fifteen percent of otter scat contained PCB concentrations exceeding levels considered to have adverse effects on the reproduction of mink (Neovison vison), and there were significant positive correlations between concentrations of PCBs and of thyroid (T3) and sex (progesterone) hormones in fecal samples. Radio telemetry data revealed that otters did not show directional movement away from the harbours, indicating their inability to recognize the contaminated site as a degraded habitat. However, analysis and modeling of the DNA genotyping data provided no evidence that the harbour otters formed a sink population and therefore were in an ecological trap. Despite the highly POP-contaminated habitat, river otters did not appear to be adversely impacted at the population level. Our study demonstrates the value of combining chemical and biological technologies with ecological theory to investigate practical conservation problems.

Dietary fish oil used in aquafeed transfers marine pollutants to farmed fish. However, the entire transfer route of marine pollutants in dietary fish oil from ocean to table fish has not been tracked quantitatively. To track the entire transfer route of marine pollutants from wild fish to farmed fish through dietary fish oil and evaluate the related human health risks, we obtained crude and refined fish oils originating from the same batch of wild ocean anchovy and prepared fish oil-containing purified aquafeeds to feed omnivorous lean Nile tilapia and carnivorous fatty yellow catfish for eight weeks. The potential human health risk of consumption of these fish was evaluated. Marine persistent organic pollutants (POPs) were concentrated in fish oil, but were largely removed by the refining process, particularly dioxins and polychlorinated biphenyls (PCBs). The differences in the POP concentrations between crude and refined fish oils were retained in the fillets of the farmed fish. Fillets fat content and fish growth were positively and negatively correlated to the final POPs deposition in fillets, respectively. The retention rates of marine POPs in the final fillets through fish oil-contained aquafeeds were 1.3%–5.2%, and were correlated with the POPs concentrations in feeds and fillets, feed utilization and carcass ratios. The dietary crude fish oil-contained aquafeeds are a higher hazard ratio to consumers. Prohibiting the use of crude fish oil in aquafeed and improving growth and feed efficiency in farmed fish are promising strategies to reduce health risks originating from marine POPs.

Sediments from a waste pit in Houston Ship Channel (HSC) were characterized using a number of molecular markers of natural organic matter fractions (e.g., pyrogenic carbon residues, PAHs, lignins), in addition to dioxins, in order to test the hypothesis that the dispersal and mobility of dioxins from the waste pit in the San Jacinto River is minimal. Station SG-6, sampled at the site of the submerged waste pit, had the highest dioxin/furan concentrations reported for the Houston Ship Channel/Galveston Bay (HSC/GB) system (10,000–46,000 pg/g), which translated into some of the highest reported World Health Organization Toxic Equivalents (TEQs: 2000–11,000 pg/g) in HSC sediments. Using a multi-tracer approach, this study confirmed our hypothesis that sludges from chlorinated pulps are a very likely source of dioxins/furans to this pit. However, this material also contained large quantities of additional hydrophobic organic contaminants (PAHs) and pyrogenic markers (soot-BC, levoglucosan), pointing to the co-occurrence of petroleum hydrocarbons and combustion byproducts. Comparison of dioxin/furan signatures in the waste pit with those from sediments of the HSC and a control site suggests that the remobilization of contaminated particles did not occur beyond the close vicinity of the pit itself. The dioxins/furans in sediments outside the waste pit within the HSC are rather from other diffuse inputs, entering the sedimentary environment through the air and water, and which are comprised of a mixture of industrial and municipal sources. Fingerprinting of waste pit dioxins indicates that their composition is typical of pulp and paper sources. Measured pore water concentrations were 1 order of magnitude lower than estimated values, calculated from a multiphase sorption model, indicating low mobility of dioxins within the waste pit. This is likely accomplished by co-occurring and strong sorbing pyrogenic and petrogenic residues in the waste pit, which tend to keep dioxins strongly sorbed to particles.

The Gulf of Follonica (Italy) is impacted by the chemical pollution from ancient mining activity and present industrial processes. This study was aimed to determine the bioavailability of dioxin-like compounds (DLCs) in coastal marine environment and to assess the genotoxic potential of waste waters entering the sea from an industrial canal. Moderately high levels of DCLs compounds (∑PCDDs+PCDFs 2.18–29.00pg/g dry wt) were detected in Mytilus galloprovincialis transplanted near the waste waters canal and their corresponding Toxic Equivalents (TEQs) calculated. In situ exposed mussels did not show any genotoxic effect (by Comet and Micronucleus assay). Otherwise, laboratory exposure to canal waters exhibited a reduced genomic template stability (by RAPD-PCR assay) but not DNA or chromosomal damage. Our data reveal the need to focus on the levels and distribution of DLCs in edible species from the study area considering their potential transfer to humans through the consumption of sea food.

A mixture of polyethylene (PE), polyethylene-terephtalate (PET), polypropylene (PP) and Nylon was submerged in marine water during 12 moths. The chlorine content of these plastics was measured through the passing time. Thermobalance was used to look for differences in the thermal decomposition of the plastics during in that time interval. Degradation of PET, PP and Nylon produced changes in the weight loss curve, but behaviour of PE is confusing. Pyrolysis and combustion at 850 °C was finally performed to get knowledge of the possible differences in the emission of main gases, volatiles and semivolatiles including polycyclic aromatic hydrocarbons (PAHs), polychlorinated benzenes (ClBzs), polychlorinated phenols (ClPhs), polybrominated phenols (BrPhs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Results show that the emission of chlorinated species is somewhat not affected by the chlorine content of the plastics mix. The production of PCBs and PCDD/Fs was very low, under 4 pg WHO-TEQ/g.

Dioxins have global concerns because of the bioaccumulation tendency and persistency in the environment. Water, seabream Pagrus auratus and seabass Dicentrarchus labrax samples were collected from Abu Qir, Alexandria to evaluate the concentration of dioxin. Fourier Transform Infrared Spectrometer (FTIR) and molecular modeling was applied for elucidating the molecular structure of fish samples. Furthermore, HPLC with UV detection was used to determine the concentration of dioxins (2,8-dichloro dibenzo-p-dioxin). RT-PCR assay was conducted to verify the expression of some immune genes in the fish species as a result of water pollution. The average detected concentrations varied from 0.2 to 1.3μg/l. Gene expression revealed that MHC class 1 and C3 were highly upregulated in liver and muscle of seabass and seabream while T2BP was highly regulated in seabass liver and seabream muscle and seabass muscle for transferrin, FTIR and molecular modeling indicate that dioxin finds its way to fish protein.

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are ubiquitous and highly toxic emerging endocrine disruptors found in surface and subsurface soils and clay deposits. Seriously, they could be easily transformed to the more toxic dioxins (PBDD/Fs) in photochemical processes and incineration, but the spontaneous formation of PBDD/Fs has rarely been reported. This study focused on the formation of 1,3,8-tribromodibenzo-p-dioxin (1,3,8-TrBDD) and 2,4,6,8-tetrabromodibenzofuran (2,4,6,8-TeBDF) from 2′-OH-BDE-68 and 2,2′-diOH-BB-80 under the oxidization of iron and manganese oxides (goethite and MnOₓ). Approximately 0.09 μmol/kg (2.33%) and 0.17 μmol/kg (4.15%) were transformed to 1,3,8-TrBDD and 2,4,6,8-TeBDF by goethite in 8 days and a higher conversion 0.15 μmol/kg (3.77%) and 0.23 μmol/kg (5.74%) were observed for MnOₓ in 4 days. However, the formation of PBDD/Fs, probably proceeding via Smiles rearrangements and bromine elimination processes, was greatly inhibited by the presence of water. Transformation of OH-PBDEs by goethite and MnOₓ was accompanied by release of Fe and Mn ions and the possible pathways for the formation of reaction products were proposed. In view of the ubiquity of OH-PBDEs and metal oxides in the environment, oxidation of OH-PBDEs mediated by goethite and MnOₓ is likely an abiotic route for the formation of PBDD/Fs.

In what has become known as the Yusho incident, thousands of people in western Japan were poisoned by the accidental ingestion of rice bran oil contaminated with polychlorinated biphenyls (PCBs) and various dioxins and dioxin-like compounds. In this study, we investigated the accumulation patterns of 69 PCB congeners in the blood of Yusho patients in comparison with those of non-exposed controls. The blood samples were collected at medical check-ups in 2004 and 2005. To compare the patterns of PCB congeners, we calculated the concentration ratio of each congener relative to the 2,2′,4,4′,5,5′-hexaCB (CB153) concentration. The concentration ratios of tetra- and penta-chlorinated congeners in the blood of Yusho patients were significantly lower than those of controls. To examine the cytochrome P450 (CYP)-dependent metabolic potential of the 2,3′,4,4′5-pentaCB (CB118), CB153, and 2,3,3′,4,4′5-hexaCB (CB156) congeners, we conducted PCB-CYP (CYP1A1, CYP1A2, CYP2A6, and CYP2B6) docking simulation by in silico analysis. The docking models showed that human CYP1A1, CYP2A6, and CYP2B6 isozymes have the potential to metabolize CB118 and CB153. On the other hand, it was inferred that CB156 is difficult to be metabolized by these four CYP isozymes. These results indicate that CYP1 and CYP2 isozymes may be involved in the characteristic accumulation patterns of PCB congeners in the blood of Yusho patients.

The destruction of persistent organic pollutants(POPs) is a large challenge in particular in developing and emerging economies.