Toxic equivalency factors for dioxin-like PCBs

Ocean as source or sink for legacy persistent organic pollutants

With the phase-out of legacy persistent organic pollutants (POPs), the ocean's role is evolving, potentially acting as both a reservoir and a source. This study investigates the air-sea fluxes of the first banned POPs, such as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), using literature from Web of Science up to 2023. OCP and PCB concentrations in air and seawater show significant spatiotemporal variability. In air, α-HCH and p,p'-DDE dominate, with concentrations decreasing over time and varying with latitude. In seawater, α-HCH and p,p'-DDTs show higher levels in the Northern Hemisphere and significant temporal decreases. PCB concentrations differ notably between low- and high-chlorinated compounds, with distinct spatial patterns. HCHs exhibit distinct flux patterns, with volatilization in equatorial regions and deposition in higher latitudes. DDTs mainly show deposition trends, except in Southeast Asia where recent increases in volatilization are observed. PCBs generally demonstrate deposition, with regional and seasonal variations. Time significantly impacts fluxes due to changes in human activity and regulations. High-chlorine PCBs are more affected by distance from the sea surface, while temperature increases POPs volatilization.

Dioxin-like polychlorinated biphenyls (dl-PCB) in hydrochars and biochars: Review of recent evidence, pollution levels, critical gaps, formation mechanisms and regulations

Contamination of chars with dioxin-like polychlorinated biphenyls (dl-PCB) significantly limits their use and hinders their deployment in the circular bioeconomy, specifically in applications that may lead to dietary exposure. Here, for the first time, we review the levels of contamination of chars produced from pyrolysis and hydrothermal carbonisation (HTC) with dl-PCB congeners. We conduct a detailed and critical examination of the role played by the processing parameters, such as temperature and residence time, and the reaction mechanisms, to detoxify the biomass under an oxygen-free atmosphere during its valorisation. The PCB-based toxicity of biomass depends mostly on the abundance of dl-PCB in the raw material, and on the dechlorination and other transformation processes that operate during the treatment. The key dechlorination steps make the toxicity of hydrochars pass through a maximum with increasing treatment time, whereas the toxicity of biochars in pyrolysis decreases monotonically. Pyrolysis displays more complex mechanistic pathways of volatilisation, dechlorination, degradation of PCB rings, minor de novo formation of dl-PCB in case of air leaks, and concentrating persistent organic pollutants (POP) in char matrices. In contrast, the mechanisms responsible for the evolution of toxicity in HTC processes comprise the dechlorination, possible chlorine position shift, and biomass densification. The kinetic model developed in this review affords insight into the evolution of the hydrochar toxicity that depends on process temperature and treatment time. The dl-PCB concentrations in treated biomass generally range from 1.06 ng WHO2005-TEQ (kg DM)-1 to 11.7 ng WHO2005-TEQ (kg DM)-1, whereas for biochars produced from contaminated sediments the toxicity varies from 0.00662 ng WHO1998-TEQ (kg DM)-1 to 1.42 ng WHO1998-TEQ (kg DM)-1. DM stands for dry matter, TEQ for toxic equivalency, and WHO1998 means the application of the toxic equivalency factors (TEF) set by the World Health Organization (WHO) in 1998 to calculate the TEQ. Finally, we identify the crucial gaps in the literature, review the regulations governing the use of biomass in feed and in the environment, and provide suggestions for future research. The findings in this article provide both the technical understanding of how to minimise the formation of dl-PCB in the production of chars and suggest modifications to the current guidelines. The latter will increase the consumer's trust in valorised biomass, leading to its wider acceptance in the circular bioeconomy as feed supplements and soil additives.

Dioxins vs. PFAS: Science and Policy Challenges

BACKGROUND

Dioxin-like chemicals are a group of ubiquitous environmental toxicants that received intense attention in the last two decades of the 20th century. Through extensive mechanistic research and validation, the global community has agreed upon a regulatory strategy for these chemicals that centers on their common additive activation of a single receptor. Applying these regulations has led to decreased exposure in most populations studied. As dioxin-like chemicals moved out of the limelight, research and media attention has turned to other concerning contaminants, including per- and polyfluoroalkyl substances (PFAS). During the 20th century, PFAS were also being quietly emitted into the environment, but only in the last 20 years have we realized the serious threat they pose to health. There is active debate about how to appropriately classify and regulate the thousands of known PFAS and finding a solution for these "forever chemicals" is of the utmost urgency.

OBJECTIVES

Here, we compare important features of dioxin-like chemicals and PFAS, including the history, mechanism of action, and effective upstream regulatory strategies, with the objective of gleaning insight from the past to improve strategies for addressing PFAS.

DISCUSSION

The differences between these two chemical classes means that regulatory strategies for dioxin-like chemicals will not be appropriate for PFAS. PFAS exert toxicity by both receptor-based and nonreceptor-based mechanisms, which complicates mixtures evaluation and stymies efforts to develop inexpensive assays that accurately capture toxicity. Furthermore, dioxin-like chemicals were unwanted byproducts, but PFAS are useful and valuable, which has led to intense resistance against efforts to restrict their production. Nonetheless, useful lessons can be drawn from dioxin-like chemicals and applied to PFAS, including eliminating nonessential production of new PFAS and proactive investment in environmental remediation to address their extraordinarily long environmental persistence. https://doi.org/10.1289/EHP14449.

A Comprehensive Evaluation of Dioxins and Furans Occurrence in River Sediments from a Secondary Steel Recycling Craft Village in Northern Vietnam

This first study investigated the presence of dioxins and furans in river sediments around a craft village in Vietnam, focusing on Secondary Steel Recycling. Sediment samples were collected from various locations along the riverbed near the Da Hoi Secondary Steel Recycling village in Bac Ninh province. The analysis was conducted using a HRGC/HRMS-DFS device, detecting a total of 17 dioxin/furan isomers in all samples, with an average total concentration of 288.86 ng/kg d.w. The concentrations of dioxin/furan congeners showed minimal variation among sediment samples, ranging from 253.9 to 344.2 ng/kg d.w. The predominant compounds in the dioxin group were OCDD, while in the furan group, they were 1,2,3,4,6,7,8-HpCDF and OCDF. The chlorine content in the molecule appeared to be closely related to the concentration of dioxins and their percentage distribution. However, the levels of furan isomers did not vary significantly. The distribution of these compounds was not dependent on the flow direction, as they were mainly found in solid waste and are not water-soluble. Although the hepta and octa congeners had high concentrations, when converted to TEQ values, the tetra and penta groups (for dioxins) and the penta and hexa groups (for furans) contributed more to toxicity. Furthermore, the source of dioxins in sediments at Da Hoi does not only originate from steel recycling production activities but also from other combustion sites. The average total toxicity was 10.92 ng TEQ/kg d.w, ranging from 4.99 to 17.88 ng TEQ/kg d.w, which did not exceed the threshold specified in QCVN 43:2017/BTNMT, the National Technical Regulation on Sediment Quality. Nonetheless, these levels are still concerning. The presence of these toxic substances not only impacts aquatic organisms in the sampled water environment but also poses potential health risks to residents living nearby.

Trends in low temperature and non-thermal technologies for the degradation of persistent organic pollutants

The daunting effects of persistent organic pollutants on humans, animals, and the environment cannot be overemphasized. Their fate, persistence, long-range transport, and bioavailability have made them an environmental stressor of concern which has attracted the interest of the research community. Concerted efforts have been made by relevant organizations utilizing legislative laws to ban their production and get rid of them completely for the sake of public health. However, they have remained refractive in different compartments of the environment. Their bioavailability is majorly a function of different anthropogenic activities. Landfilling and incineration are among the earliest classical means of environmental remediation of waste; however, they are not sustainable due to the seepage of contaminants in landfills, the release of toxic gases into the atmosphere and energy requirements during incineration. Other advanced waste destruction technologies have been explored for the degradation of these recalcitrant pollutants; although, some are efficient, but are limited by high amounts of energy consumption, the use of organic solvents and hazardous chemicals, high capital and operational cost, and lack of public trust. Thus, this study has systematically reviewed different contaminant degradation technologies, their efficiency, and feasibility. Finally, based on techno-economic feasibility, non-invasiveness, efficiency, and environmental friendliness; radiation technology can be considered a viable alternative for the environmental remediation of contaminants in all environmental matrices at bench-, pilot-, and industrial-scale.

Reevaluation of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Equivalency Factors for Dioxin-Like Polychlorinated Dibenzo-p-Dioxins, Polychlorinated Dibenzofurans, and Polychlorinated Biphenyls for Fishes

An expert meeting was organized by the World Health Organization (WHO) in 1997 to streamline assessments of risk posed by mixtures of dioxin-like chemicals (DLCs) through development of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) equivalency factors (TEFs) for mammals, birds, and fishes. No reevaluation has been performed for fish TEFs. Therefore, the objective of the present study was to reevaluate the TEFs for fishes based on an updated database of relative potencies (RePs) for DLCs. Selection criteria consistent with the WHO meeting resulted in 53 RePs across 14 species of fish ultimately being considered. Of these RePs, 70% were not available at the time of the WHO meeting. These RePs were used to develop updated TEFs for fishes based on a similar decision process as used at the WHO meeting. The updated TEF for 16 DLCs was greater than the WHO TEF, but only four differed by more than an order of magnitude. Measured concentrations of DLCs in four environmental samples were used to compare 2,3,7,8-TCDD equivalents (TEQs) calculated using the WHO TEFs relative to the updated TEFs. The TEQs for none of these environmental samples differed by more than an order of magnitude. Therefore, present knowledge supports that the WHO TEFs are suitable potency estimates for fishes. However, the updated TEFs pull from a larger database with a greater breadth of data and as a result offer greater confidence relative to the WHO TEFs. Risk assessors will have different criteria in the selection of TEFs, and the updated TEFs are not meant to immediately replace the formal WHO TEFs; but those who value a larger database and increased confidence in TEQs could consider using the updated TEFs. Environ Toxicol Chem 2023;42:2215-2228. © 2023 Wiley Periodicals LLC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Internal relative potency factors based on immunotoxicity for the risk assessment of mixtures of per- and polyfluoroalkyl substances (PFAS) in human biomonitoring

Relative potency factors (RPFs) for per- and polyfluoroalkyl substances (PFAS) have previously been derived based on liver effects in rodents for the purpose of performing mixture risk assessment with primary input from biomonitoring studies. However, in 2020, EFSA established a tolerable weekly intake for four PFAS assuming equal toxic potency for immune suppressive effects in humans. In this study we explored the possibility of deriving RPFs for immune suppressive effects using available data in rodents and humans. Lymphoid organ weights, differential blood cell counts, and clinical chemistry from 28-day studies in male rats from the National Toxicology Program (NTP) were combined with modeled serum PFAS concentrations to derive internal RPFs by applying dose-response modelling. Identified functional studies used diverse protocols and were not suitable for derivation of RPFs but were used to support immunotoxicity of PFAS in a qualitative manner. Furthermore, a novel approach was used to estimate internal RPFs based on epidemiological data by dose-response curve fitting optimization, looking at serum antibody concentrations and key cell populations from the National Health and Nutrition Examination Survey (NHANES). Internal RPFs were successfully derived for PFAS based on rat thymus weight, spleen weight, and globulin concentration. The available dose-response information for blood cell counts did not show a significant trend. Immunotoxic potency in serum was determined in the order PFDA > PFNA > PFHxA > PFOS > PFBS > PFOA > PFHxS. The epidemiological data showed inverse associations for the sum of PFOA, PFNA, PFHxS, and PFOS with serum antibody concentrations to mumps and rubella, but the data did not allow for deduction of reliable internal RPF estimates. The internal RPFs for PFAS based on decreased rat lymphoid organ weights are similar to those previously established for increased rat liver weight, strengthening the confidence in the overall applicability of these RPFs.

Organochlorine contaminants in Rio skate (Rioraja agassizii), an endangered batoid species, from southeastern coast of Brazil

A global movement towards decreases in elasmobranch overfishing has been noted in the last decades. However, discussion concerning the effects of POP contamination on the health and survival of these organisms is still recent. These compounds can affect the immune and endocrine systems of both sharks and batoids, impairing reproduction and impacting species recruitment, acting synergistically alongside overfishing effects. In this context, this study investigated the concentration of organochlorine compounds in liver of 29 individuals of Rioraja agassizii, a commercially exploited skate classified as Vulnerable by IUCN and as Endangered in Brazil. Contaminant concentrations were higher in adults compared to juveniles. Distinct contamination profiles were observed, suggesting different groups within the investigated population and revealing contaminants as a potential tool to assess population ecology. PCB levels were considered a concern as they resemble concentrations in ecosystems from the northern hemisphere, where deleterious effects on elasmobranchs have been observed.

Assessment of Pesticide, Dioxin-like Polychlorinated Biphenyl, and Polycyclic Aromatic Hydrocarbon Existence around Galindez Island, and Comparison with the Organic Pollution Bibliography of the Antarctic Peninsula

Sediment, notothenioid fish, and moss samples were collected from the vicinity of Galindez Island, Antarctic Peninsula during the austral autumn of 2016 and 2017. Pesticide, Polycyclic Aromatic Hydrocarbon (PAH), and dioxin-like Polychlorinated Biphenyl (dl-PCB) concentrations were measured using High-Resolution Gas and Liquid Chromatography. Pollutant concentrations were below detection limits in sediment and moss samples. However, pesticides, PAH, and dl-PCB congeners were detected in the muscle tissue of fishes. Pesticide concentrations varied between 0.46 and 12.2 ng/g-dw, and Mecarbam was the dominant compound. Kresoxim-methyl, Mecarbam, Procymidone, Pyridaben, and Quinoxyfen were reported in the muscle tissue of the fishes, for the first time from the Antarctic. PCB-118, PCB-105, and PCB-156 were dominant dl-PCBs. The ∑12-dl-PCB concentration was 160,929 pg/g-dw, and WHO-TEQ-total dl-PCB was 8.30 pg/g-dw in Trematomus bernachii, over the consumable limit in fishes according to the European Commission. The PCB-126 concentration was 36 pg/g-dw in the muscle tissue of fish, the first reported from the Antarctic. Phenanthrene was the dominant PAH congener. The ∑16-PAH concentration was 22.5 ng/g-dw. PAH sources were local and petrogenic in the fishes, likely after long-term bioaccumulation. The flow rate is rather low around Galindez Island; accordingly, contaminant removal takes time and may demonstrate long-lasting effects including bioaccumulation in the marine food web.

Dose-dependent toxicological effects in rats following a 90-day dietary exposure to PCB-156 include retinoid disruption

The toxicity of PCB-156 (2,3,3',4,4',5-hexachlorobiphenyl) was investigated in rats following subchronic dietary exposure. Groups of 10 male and female Sprague-Dawley rats were administered PCB-156 in the diet at 0, 0.01, 0.1, 1 or 10 ppm for 90 days. Dose-dependent increases were detected for the liver, lung and kidney weights, as well as for the liver EROD, PROD and UDPGT enzyme activities and liver uroporphyrin concentration. Dose-dependent decreases were observed in final body weight, body weight gain, and thymus weight. Apolar retinoid concentrations were decreased in the liver and lungs and increased in the kidneys. Histopathological examination of the liver, thyroid, and thymus showed mild to moderate dose-related changes. A LOAEL of 0.01 ppm was established, based on reduced apolar liver retinoid concentration. Benchmark dose-modelling corroborated the sensitivity of liver retinoid endpoints. The lower confidence limits (BMDL) for a 5% decrease in apolar liver retinoid concentrations were 0.0009 and 0.0007 ppm, respectively, in males and females, corresponding to a daily dose of 0.06 μg PCB-156 per kg body weight. Organizing dose-response data for the individual hepatic endpoints along the PCB-156 dosing scale revealed a sequence of events compatible with a causal link between depletion of apolar retinoids and the other liver biochemistry and pathology findings. Taken together, data suggest that the retinoid endpoints should be further evaluated for a causal relationship to PCB-induced liver toxicity and that retinoid system endpoints are identified and characterized to support health risk assessment in the emerging research fields of endocrine disruption and mixture toxicology.

Extraction of Chlorobenzenes and PCBs from Water by ZnO Nanoparticles

Metal oxide nanoparticles have great potential for selective adsorption and catalytic degradation of contaminants from aqueous solutions. In this study, we employ mass spectrometry and molecular dynamics simulations to better understand the chemical and physical mechanisms determining the affinity of chlorobenzenes and polychlorinated biphenyls (PCBs) for zinc oxide nanoparticles (ZnO NPs). The experiments and simulations both demonstrate that the adsorption coefficients for chlorobenzenes increase steadily with the number of chlorine atoms, while, for PCBs, the relation is more complex. The simulations link this complexity to chlorine atoms at ortho positions hindering coplanar conformations. For a given number of chlorine atoms, the simulations predict decreasing adsorption affinity with increasing numbers of ortho substitutions. Consequently, the simulations predict that some of the highest adsorption affinities for ZnO NPs are exhibited by dioxin-like PCBs, suggesting the possibility of selective sequestration of these most acutely toxic PCBs. Remarkably, the experiments show that the PCB adsorption coefficients of ZnO NPs with diameters ≤ 80 nm exceed those of a soil sample by 5–7 orders of magnitude, meaning that a single gram of ZnO NPs could sequester low levels of PCB contamination from as much as a ton of soil.

Persistent organic pollutants (POPs) in fish species from different lakes of the lesser Himalayan region (LHR), Pakistan: The influence of proximal sources in distribution of POPs

Fish dwelling in remote mountain water systems are sensitive to long term exposure of POPs and can be used as an important bioindicator of POPs pollution in fragile mountain ecosystems. Current study aimed to investigate the concentrations and patterns of organic pollutants in fish tissues from different lakes of the Lesser Himalayan Region (LHR). OCPs, PCBs, PBDEs were analyzed in four common edible fish species of the LHR: Oncorhynchus mykiss, Labeo rohita, Hypophthalmichthys molitrix and Orechromis aureus. The fish were collected from lakes with different types of catchment areas (glacial, non-glacial mountain region and urban region) and extent of anthropogenic influence. The levels OCPs, PCBs and PBDEs analyzed in the selected fish species were in range of 0.21-587, 6.4-138 and 1.2-14 ng g^-1 lw, respectively. The ∑DDTs, higher chlorinated PCBs, tetra- and penta-BDEs were more prevalent in urban and remote lakes whereas pp'-DDE, lower chlorinated PCBs and BDE-47 and -99 were predominant in fish species from glacial lakes. ∑DDTs, ∑PCBs and ∑PBDEs showed statistically significant differences (p < 0.05) among species, trophic guilds (carnivore, herbivore and omnivore) and feeding regimes (surface, bottom and column feeder) and ∑HCH showed a significant difference only among trophic guilds. The stable isotope values of δ ¹⁵N and δ¹³C differed significantly among species for ∑HCH, ∑PCBs, ∑PBDEs (p < 0.05) and ∑DDT (p < 0.01). The range of δ¹³C values (-34 to -19‰) indicated the importance of littoral and pelagic sources of dietary carbon. Trophic position and dietary proxies were identified as important variables for explaining the variability of the studied compounds. Kohonen self-organizing maps (SOM) showed that in addition to trophic position and other physiological characteristics of fish, that the type of lakes and proximal sources of POPs were the most important predictors for distribution of organic contaminants in fish samples from LHR.

Levels of dioxins and dioxin-like polychlorinated biphenyls in seawater from the Hornsund fjord (SW Svalbard)

Knowledge of contaminant distribution is important, particularly in the vulnerable first results about the occurrence of seventeen polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans and twelve dioxin-like polychlorinated biphenyls in arctic fjord seawater are reported. The contaminants were measured in 10 samples of suspended particulate matter collected in Hornsund (Svalbard). The ∑PCDD/F and ∑dl-PCB concentrations ranged from 0.066 to 231.47 pg/L and from 2.43 to 46.43 pg/L respectively. In terms of total PCDD/Fs, in general highly chlorinated PCDFs constituted the most significant fraction. Among dl-PCB compounds, PCB118 was the dominant congener. The toxicity equivalent for the samples ranged from 0.0008 to 1.90 pg I-TEQ/L for ∑PCDD/Fs, while for ∑dl-PCB it ranged from 0.0002 to 0.024 pg WHO₀₅-TEQ/L. High concentrations of dioxins and dl-PCBs in some samples indicated that those contaminants could pose a threat to marine biota.

Tissue contaminants and wild fish health in the St. Clair River Area of Concern - Part 2: Spatial trends and temporal declines in organics

We explored tissue concentrations of polychlorinated biphenyls (PCBs), chlorinated pesticides, and relevant organochlorines and fish health in the following adult wild fish in the St. Clair River Area of Concern (Ontario, Canada): shorthead redhorse (Moxostoma macrolepidotum), yellow perch (Perca flavescens), and emerald shiner (Notropis atherinoides). We collected adult fish from sites within the river's industrial zone (Stag Island), a downstream site adjacent to Walpole Island (Chenal Écarte), and an upstream reference site in Lake Huron in 2002/2003 and 2014. We tested for trends in tissue concentrations of organic contaminants across sites and over time; we assessed the potential effects of contaminants on morphological indicators of fish health across sites by year. Over the 12-year period, the tissue concentrations of most PCBs declined at the river sites, except for some non-legacy PCBs (PCB11 and 185), which increased in yellow perch at Stag Island, a new observation for fish in the St. Clair River AOC. There was little difference between the concentrations of calculated toxic equivalents (TEQs) of the Lake Huron and the St. Clair River fish in 2014, except for emerald shiners from Stag Island which had elevated ΣPCB and TEQs. Each fish species at all sites exceeded the Canadian tissue residue guideline for PCBs for the protection of mammalian wildlife consumers of aquatic biota, but fish-derived TEQs indicated little potential health risk to fish. Over time, hexachlorobutadiene and hexachlorobenzene concentrations increased in some fish at Stag Island by about 8- and 4-fold, respectively, whereas they decreased at other sampling locations. Principal Component Analysis followed by Linear Discriminant Analysis of the 2014 SHRH data suggested that although the fish separated by site, tissue concentrations of PCB and organochlorine contaminants did not have consistent relationships to the morphological health indicators, including egg production in females, which implied the absence of causative relationships.

Alternative Approaches and Tests in Ecotoxicology: A Review of the Present Position and the Prospects for Change, Taking into Account ECVAM's Duties, Topic Selection and Test Criteria

The objectives of this review are to summarise the present position concerning the use of vertebrates in ecotoxicity testing, giving particular attention to tests that cause suffering, and to discuss in some detail, alternatives to them, and the prospects for change. The report has been written with the objectives of the European Centre for the Validation of Alternative Methods (ECVAM) in mind, and some recommendations for action have been made at the end of the discussion section. The first section of the review describes the present requirements within the European Union for the ecotoxicity testing of industrial chemicals in general, and for pesticides in particular, and the very limited documentation of the tests that are actually carried out. The next four sections describe the many different assays and systems used to evaluate the harmful effects of chemicals on free-living organisms and natural populations, and the extent to which they might be suitable alternatives to vertebrate toxicity tests that cause suffering. Attention is drawn to certain assays and strategies that can already be used as satisfactory alternatives, and thus provide the basis for short-term change. Included here are nondestructive assays on vertebrates which are available for certain types of chemicals, and which provide a direct and relatively uncomplicated approach to the problem. Other approaches are described which still require development, but hold considerable promise in the longer term. The growth of knowledge in the broad field of biochemical toxicology and the development of related technologies should lead to the development of better and more-sophisticated alternatives in the future. In vitro assays employing vertebrate cell systems are of particular interest here. The last section of the review deals with conclusions and recommendations. The recommendations are made with a view to the activities and responsibilities of ECVAM.

Assessment of PCDD/Fs, dioxin-like PCBs and PBDEs in Mediterranean striped dolphins

Bio-accumulation of high levels of persistent organic pollutants represent a serious conservation concern for Mediterranean marine odontocetes. In this study, blubber samples from 10 striped dolphins (Stenella coeruleoalba) stranded along the Italian coasts during 2015-2016 were analyzed. All specimens showed dl-PCBs > PBDEs ≫ PCDD/Fs. Median concentrations were 1820 ng/g l.w., 456 ng/g l.w. and 23.9 pg/g l.w., respectively. dl-PCBs accounted for 93.3% of total TEQs. PBDE concentrations suggest that the Mediterranean basin may be considered a hotspot for organobromine compounds. OCDD did not represent the greatest contributor to PCDD/Fs profile, most likely due to a change in dioxin environmental sources in the last two-three decades. Despite international regulations, the present study emphasized that POP exposure levels in Mediterranean striped dolphins have not declined significantly in recent years. Toxicological and risk assessment studies on this sentinel species may provide an early indication of potential adverse health effects on Mediterranean ecosystems.

Tissue distribution and characterization of feline cytochrome P450 genes related to polychlorinated biphenyl exposure

Cats have been known to be extremely sensitive to chemical exposures. To understand these model species' sensitivity to chemicals and their toxicities, the expression profiles of xenobiotic-metabolizing enzymes should be studied. Unfortunately, the characterization of cytochrome P450 (CYP), the dominant enzyme in phase I metabolism, in cats has not extensively been studied. Polychlorinated biphenyls (PCBs) are known as CYP inducers in animals, but the information regarding the PCB-induced CYP expression in cats is limited. Therefore, in the present study, we aimed to elucidate the mRNA expression of the CYP1-CYP3 families in the cat tissues and to investigate the CYP mRNA expression related to PCB exposure. In cats, the greatest abundance of CYP1-CYP3 (CYP1A2, CYP2A13, CYP2C41, CYP2D6, CYP2E1, CYP2E2, CYP2F2, CYP2F5, CYP2J2, CYP2U1, and CYP3A132) was expressed in the liver, but some extrahepatic isozymes were found in the kidney (CYP1A1), heart (CYP1B1), lung (CYP2B11 and CYP2S1) and small intestine (CYP3A131). In cats, CYP1A1, CYP1A2 and CYP1B1 were significantly upregulated in the liver as well as in several tissues exposed to PCBs, indicating that these CYPs were distinctly induced by PCBs. The strong correlations between 3,3',4,4'-tetrachlorobiphenyl (CB77) and CYP1A1 and CYP1B1 mRNA expressions were noted, demonstrating that CB77 could be a potent CYP1 inducer. In addition, these CYP isoforms could play an essential role in the PCBs biotransformation, particularly 3-4 Cl-PCBs, because a high hydroxylated metabolite level of 3-4 Cl-OH-PCBs was observed in the liver.

Kinetic and mechanistic insight into the OH-initiated atmospheric oxidation of 2,3,7,8-tetrachlorodibenzo-p-dioxin via OH-addition and hydrogen abstraction pathways: A theoretical investigation

The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic polychlorinated dibenzo-p-dioxin. The OH-initiated oxidation of TCDD has been studied using the density functional, canonical transition state, and canonical Rice-Ramsperger-Kassel-Marcus theories. The kinetic data were corrected for quantum tunneling by the Wigner and Eckart models. All OH addition and hydrogen atom abstraction channels were thermodynamically exergonic. The kinetic and thermodynamic data analysis at the reliable level MPWB1K/MG3S//M06-2X/MG3S indicate that the addition of OH to the carbon atom adjacent to the oxygen atom in dioxin ring leads to the formation of predominant adduct. The calculated bimolecular rate constant for the formation of predominant adduct was ~5.97-6.75 × 10^-13 cm³ molecule^-1 s^-1, its branching ratio was ~0.955, and the overall rate constant for the OH-initiated oxidation of TCDD was ~6.25-7.08 × 10^-13 cm³ molecule^-1 s^-1. The atmospheric lifetime of TCDD determined by OH was ~8.17-9.26 days indicating the TCDD can be categorized as medium lifetime organic pollutant.

Protective effects of genistein on cytochrome P-450 and vitellogenin expression in liver of zebrafish after PCB-126 exposure

The objective of the research is to study the action of Vitellogenin and P-4501A1 following coexposure at different times to genistein and PCB-126 using zebrafish as a model system. Polychlorinated biphenyls are ubiquitous substances in environment. The genistein is a phytoestrogen extracted from soybeans and it's contained in food for humans and animals. For this study, 200 adult zebrafish were used. Our findings show a marked immunoreactivity of Vtg at 12h in liver than the control with only PCB-126. Regarding effects of PCB-126 on Vtg after pretreatment with genistein in fishes, the immunohistochemistry results show a minor increase at 12h. After 24h the immunoreactivity is lower than 12h and then slightly increased at 72h with only PCB-126 and PCB-126 and genistein together. CYP1A1 progressively increases from 12h to 72h in all groups with minor immunoreactivity when we treated fish with genistein and PCB-126. We show a reduction in the estrogenic effect when the fishes were treated with genistein and PCB-126 together at 12h than the group treated with only PCB-126. Moreover, low concentrations of genistein decrease the marked P450 expression induced by PCB-126. This shows that genistein decreases the expression of P450 target genes mediated by AhR.

Monitoring polychlorinated dibenzo-p-dioxins/dibenzofurans and dioxin-like polychlorinated biphenyls in Africa since the implementation of the Stockholm Convention-an overview

Polychlorinated dibenzo-p-dioxin (PCDDs), polychlorinated dibenzofurans (PCDF), and dioxin-like polychlorinated biphenyl (dl-PCB) are groups of toxic compounds released into the environment as unintentional by-products of combustion. They persist, bioaccumulate through the food chain, and cause adverse health effects. This review attempts to collate available information on the release of PCDD/Fs and dl-PCBs and other critical data relevant to their monitoring in Africa during the existence of the Stockholm Convention (SC). Much as the implementation of the SC may be lagging, literature showed that there has been encouraging efforts that have been made with respect to PCDDs/Fs and dl-PCBs monitoring in Africa. Results from a global monitoring study showed that PCDD/Fs released to air in Africa stood at 18-532 fg WHO₉₈ TEQ/M³ while dl-PCBs were 7-278 fg WHO₉₈ TEQ/m³. In human milk, the total concentration of PCDD/Fs, i.e., WHO 2005 TEQ LB has been reported to range from 0.5 ng/g fat to 12 ng/g fat. Fourteen laboratories in Africa participated in inter-laboratory assessments of persistent organic pollutants (POPs) with two specifically for PCDD/Fs analysis. This shows that some efforts are being made to boost capacity in Africa. Levels of PCDDs/Fs and dl-PCBs in clay consumed by pregnant women have been reported in Cameroon, Democratic Republic of Congo (DRC), Nigeria, Zimbabwe, Ĉote d'Ivoire, and Uganda with a maximum concentration of 103 pg TEQ/g. This finding was very significant since women are the most impacted through exposure to POPs, a fact that is acknowledged by the SC.

Comparisons of analytical chemistry and biological activities of extracts from North Pacific gyre plastics with UV-treated and untreated plastics using in vitro and in vivo models

Plastic debris is an emerging worldwide threat to marine biota. Marine species may face unique challenges in low-flow estuarine systems with a high abundance of "macro-sized" (>4.75 mm) plastic due to the leaching of constituents and adsorbed contaminants. To simulate this leaching process, plastic samples recovered from the North Pacific Gyre along with corresponding UV-irradiated virgin plastic and non-irradiated virgin plastic counterparts were incubated in saltwater for 30 days at ambient temperatures ranging from 17 to 25 °C. Following solid-phase extraction, water samples were fractionated with sequential methanol elution from 10 to 100% and evaluated using in vitro assays assessing estrogen receptor (ER) and aryl hydrocarbon receptor (AhR) activities. In vivo responses (vitellogenin [vtg] and cytochrome p450 1A [cyp1a] mRNA) were measured following 5-day exposures in Japanese medaka (Oryzias latipes) larvae (3 days post hatch). Estrogenic plasticizers, co-planar PCBs and PAHs were quantified in the extracts using targeted GC-MS/MS and UPLC-MS/MS. In vitro estrogenicity showed highest activity in the 70% methanol fraction for all plastic leachate exposures. Whole extract in vitro estradiol equivalent (EEQ) values were 4.34 ± 2.65, 8.79 ± 2.09 and 13.78 ± 3.64 ng/L, for virgin plastic, UV-irradiated virgin plastic and North Pacific Gyre-recovered plastic, respectively (mean ± SD). Significant vtg induction was observed in medaka larvae exposed to leachate extracts from North Pacific Gyre-recovered plastic and UV-irradiated virgin plastic (9.9-fold, p = 0.039 and 10.1-fold, p = 0.042, respectively). Chemically-determined EEQ values were also localized in the 70% methanol fraction. Whole leachate extract chemical EEQ values were 0.33 ± 0.07, 1.64 ± 0.62 and 11.4 ± 2.13 ng/L, for virgin plastic, UV-irradiated virgin plastic and North Pacific Gyre-recovered plastic, respectively. In-vitro AhR activity was highest in the 70% methanol elution with greater activity in North Pacific Gyre-recovered plastic than in virgin plastic and UV-irradiated virgin plastic (toxic equivalency [TEQ] = 1.06 ± 0.54, 0.38 ± 0.07 and 0.71 ± 0.47 ng/L, respectively). CYP1A mRNA was significantly induced in larval medaka exposed to North Pacific Gyre-recovered plastic leachates (17.8-fold, p = 0.02) while exposure to virgin plastic and UV-irradiated virgin plastic leachates caused no significant change. Chemically-determined TEQ analysis for AhR indicated highest activity in the 90% methanol fraction for all leachates, with whole extract in vitro TEQs being 1.47 ± 0.87, 0.03 ± 0.05 and 0.42 ± 0.38 ng/L for North Pacific Gyre-recovered plastic, virgin plastic and UV-irradiated virgin plastic, respectively. These results indicate that weathering and UV radiation release estrogenic plasticizers and demonstrate the ability for plastics to transport adsorbed persistent organic pollutants at eco-toxicologically relevant concentrations.

Risk for animal and human health related to the presence of dioxins and dioxin-like PCBs in feed and food

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of dioxins (PCDD/Fs) and DL-PCBs in feed and food. The data from experimental animal and epidemiological studies were reviewed and it was decided to base the human risk assessment on effects observed in humans and to use animal data as supportive evidence. The critical effect was on semen quality, following pre- and postnatal exposure. The critical study showed a NOAEL of 7.0 pg WHO2005-TEQ/g fat in blood sampled at age 9 years based on PCDD/F-TEQs. No association was observed when including DL-PCB-TEQs. Using toxicokinetic modelling and taking into account the exposure from breastfeeding and a twofold higher intake during childhood, it was estimated that daily exposure in adolescents and adults should be below 0.25 pg TEQ/kg bw/day. The CONTAM Panel established a TWI of 2 pg TEQ/kg bw/week. With occurrence and consumption data from European countries, the mean and P95 intake of total TEQ by Adolescents, Adults, Elderly and Very Elderly varied between, respectively, 2.1 to 10.5, and 5.3 to 30.4 pg TEQ/kg bw/week, implying a considerable exceedance of the TWI. Toddlers and Other Children showed a higher exposure than older age groups, but this was accounted for when deriving the TWI. Exposure to PCDD/F-TEQ only was on average 2.4- and 2.7-fold lower for mean and P95 exposure than for total TEQ. PCDD/Fs and DL-PCBs are transferred to milk and eggs, and accumulate in fatty tissues and liver. Transfer rates and bioconcentration factors were identified for various species. The CONTAM Panel was not able to identify reference values in most farm and companion animals with the exception of NOAELs for mink, chicken and some fish species. The estimated exposure from feed for these species does not imply a risk.

First report of bioaccumulation and bioconcentration of aliphatic hydrocarbons (AHs) and persistent organic pollutants (PAHs, PCBs and PCNs) and their effects on alcyonacea and scleractinian corals and their endosymbiotic algae from the Persian Gulf, Iran: Inter and intra-species differences

The coral reefs of the Persian Gulf are the most diverse systems of life in the marine environment of the Middle East. Unfortunately, they are highly threatened by local and global stressors, particularly oil pollutants. This is the first quantitative and qualitative study aimed at assessing the concentration and sources of n-alkanes and POPs (PAHs, PCBs and PCNs) in coral tissues, symbiotic algae (zooxanthellae), reef sediments and seawaters in coral reefs of Lark and Kharg in the Persian Gulf, Iran. This work was conducted on eight species of six genera and three families of hard corals and one family of soft coral. A significant variation in the concentration of ∑30n-alkanes and POPs (∑40PAHs, ∑22PCBs and 20PCNs) was found in the decreasing order: zooxanthellae > coral tissue > skeleton > reef sediment > seawater. The bioaccumulation of these compounds was 2-times higher in ahermatypic than in hermatypic corals, among which significant variations were observed in both sites. In Kharg, Porites lutea had the highest mean concentration of ∑30n-alkanes and ∑40PAHs in soft tissue, whereas the lowest values were in Platygyra daedalea. A contrasting trend was documented for ∑22PCBs and 20PCNs, with the highest level reported in soft tissue of P. daedalea and the lowest in P. lutea at Kharg. Compositional pattern of AHs and PAHs demonstrated the predominance of LMW-PAHs and n-alkanes. In skeleton and reef sediments, tetra, penta and tri-CBs were the most abundant PCBs congeners followed by di-CB > hexa-CB > hepta-CB > octa-CB,whiletri-CB > di-CB > tetra-CB > penta-CB > hexa-CB > hepta-CB > octa-CB was observed for soft tissue, zooxanthellae and seawater. The results of RAD test indicated significantly negative correlation between total concentration of these compounds with zooxanthellae density, the chlorophyll-a and C₂ in corals at both reefs. This is the first report on levels, health assessment and source apportionments of POPs in zooxanthellae and a first step in the implementation of specific coral reef management measures.

In vivo effects of PCB-126 and genistein on vitellogenin expression in zebrafish

In this study, the vitellogenin (Vtg) modulation by genistein and polychlorinated biphenyl-126 (PCB-126) exposure in zebrafishes has been investigated. Both PCB-126 and genistein have been identified as aquatic pollutants and can further increase estrogenicity of waterways. Vtg is egg yolk precursor protein release by the hepatocytes during vitellogenesis. This process occurs normally in the hepatocytes in response to the activation with the estrogens such as 17-β-estradiol. Our immunohistochemical findings showed a Vtg expression that increases at 12 h and at 72 h in the liver of treated fishes with both PCB-126 and genistein, individually and in combination. Furthermore, for the first time, also hepatic stellate cells (HSC) in the liver parenchyma were strongly positive for vitellogenin.

Polychlorinated Biphenyls in Brackish Water Fish in the River Niger, Nigeria

BACKGROUND

Anthropogenic polychlorinated biphenyls (PCBs) in aquatic environments poses human and ecological health risks in Nigeria.

OBJECTIVES

This study determined the concentrations of PCBs in brackish water fish in the River Niger to assess the contamination status of fish consumed by the local population.

METHODS

The sampled fish species included Drepane africana, Mochokus niloticus, Chrysichthys nigrodigitatus, Pristipoma jubelini, Vomer septapinis, Pseudotolithus senegalensis, Mugil cephalus, Pseudotolithus elongatus, Sphyraena piscatorum and Lutjanus goreensis, purchased from landing sites. Six fish from each species were sampled, for a total of 60 samples. Twenty-seven (27) PCB congeners, #8, #18 #28, #44, #52, #60, #77, #81, #101, #105, #114, #118, #123, #126, #128, #138, #153, #156, #157, #167, #169, #170, #180, #185, #189, #195, and #206 were screened in the fish samples using standard methods. The PCBs were identified and quantified using gas chromatography (GC) (Hewlett Packard GC 5890 series 11 with electron capture detector). Confirmation was performed using Shimadzu GCMS QP2010.

RESULTS

The sum of the National Oceanic and Atmospheric Administration Agency (ΣNOAA) PCBs occurred at the highest concentration of 1830.0±484.0 μg/kg detected in Vomer septapinis, and the lowest in Pseudotolithus senegalensis, with a mean concentration of 795±169.3 μg/kg. The concentration of dioxin-like (DL) PCBs was highest in Pristipoma jubelini (992.0±88.6 μg/kg) and lowest (285.6±81.5 μg/kg) in Drepane africana. The highest mean concentration (418.±177.6 μg/kg) of International Council for the Exploration of the Seas-7 (ICES-7) PCBs was observed in Vomer septapinis. The heavier ICES-7 congeners PCB-138, PCB-153, and PCB-180 occurred at higher concentrations compared to the lighter molecular weight ICES-7: PCB-28, PCB-52, and PCB-101. The European Union (EU) marker PCB limit of 335 μg/kg was exceeded in all the brackish water fishes with the exception of Mochokus niloticus, Pristipoma jubelini and Pseudotolithus senegalensis.

DISCUSSION

The total level of PCBs in the brackish fish samples was relatively high at >1000 μg/kg (above the World Health Organization (WHO) and Food and Agriculture Organization of the United Nations (FAO) guideline of 1000 μg/kg fresh weight). The EU guideline value for fish (220 μg/kg fresh weight) was exceeded in about 80% of the brackish fish samples studied.

CONCLUSIONS

Consumption of fish from the River Niger may expose humans to polychlorinated biphenyls. In addition, since contamination of the fish samples is an indication of river contamination, river water quality is of great concern and there is a need for additional PCB data on water quality to be distributed to the community, followed by mitigation measures.

COMPETING INTERESTS

The authors declare no competing financial interests.

Polychlorinated biphenyls and its potential role in endometriosis

With the progress of global industrialization and environmental deterioration, the relationship between human health and the living environment has become an increasing focus of attention. Polychlorinated biphenyls (PCBs, including dioxin-like polychlorinated biphenyls and non-dioxin-like polychlorinated biphenyls), as part of the organic chlorine contaminants, have been suspected as playing a role in the etiopathogenesis of endometriosis. Several population-based studies have proposed that exposure to PCBs may increase the risk of developing endometriosis, while some epidemiological studies have failed to find any association between PCBs and endometriosis. The purpose of this review is to discuss the potential pathophysiological relationship between endometriosis and PCBs with a focus on both dioxin-like polychlorinated biphenyls and non-dioxin-like polychlorinated biphenyls.

Wood smoke exposure of Portuguese wildland firefighters: DNA and oxidative damage evaluation

Portugal is among the European Union countries most devastated by forest fires each year. In the last three decades, more than 3.8 million hectares of forest were burned. Wildland firefighters are exposed to a variety of hazards, including many toxic combustion products that may lead to deleterious health effects. Epidemiological studies showed a positive association between firefighting and several chronic diseases, including cancer. Results from biomonitoring studies in firefighters, particularly concerning genotoxicity evaluation, constitute a valuable tool for investigating important occupational hazards. Thus, the aim of this study was to assess genotoxicity in a group of wildland firefighters using the comet assay for DNA damage and oxidative stress. Both parameters were increased in firefighters compared to controls, but significance was only found for basal DNA damage. No significant influence was found regarding major confounding variables on the genotoxic endpoints studied, with the exception of age. Data obtained provide preliminary information on human health effects of wildland firefighting exposure at genetic and molecular levels. These findings may also provide new important data to serve as public awareness to the potential adverse health risks involving wildland firefighting. Implementation of security and hygiene measures in this sector as well as good practices campaigns may be crucial to decrease risk.

Dioxin-like pcb emissions from cement kilns during the use of alternative fuels

The substitution of combustion fuels in cement plants is increasing throughout many countries, and its individual performance is constantly assessed against strict regulatory standards. For cement plants within Australia, normal operations remain to use petroleum coal as the dominate energy source at the precalciner, avoiding the opportunity to reduce carbon-based resources and pollutant emissions (such as carbon dioxide, oxides of nitrogen, persistent organic pollutants) whilst providing the necessary energy needs through resource recovery. This paper presents stack emission monitoring of health-critical dl-PCB (dioxin-like polychlorinated biphenyl) congeners during the substitution of alternative fuels at ten Australian cement plants, and to distinguish statistical similarities between other key pollutants (such as polychlorinated dibenzo-p-dioxins and furans (PCDD-F) and hydrogen halogens) and amongst the fuels used. Sampling of plant emissions was performed during normal operations (as baseline trials) and with the varied substitution rates of waste oil, solvents, chipped wood, refuge waste, carbon dust, shredded tyres and black sand (as experimental trials). The extraction of field and analytical data during these trials allowed for determining the total and individual unit mass of dl-PCB and PCDD-F isomers, standardised to 10% O₂ and to World Health Organization (2005) toxicity equivalence (TEQ) values. The findings showed waste co-incineration during cement operations does reduce health-critical congeners of dioxins and dl-PCBs whilst providing the necessary energy and calcination needs. Experimental trials showed all dl-PCBs and PCB TEQ are below the internationally regulated Stockholm Convention article of 10pg TEQ/Nm³. In several cases, an increased rate of substituted fuel also identified a consistent reduction to baseline dl-PCBs. The distribution of toxic isomers (TCDD-F and PeCDD-F) were shown to be predominate during waste oil, wood chips, and solvent trials. Whereas the use of TDFs consistently showed a lower toxicity contribution. The distribution of dl-PCBs toxic congeners showed PCB-126 (3,3',4,4',5-Pentachlorobiphenyl) to be greatly present during the co-incineration of waste oil, wood chips, solvents and TDF trials. Principle component analysis identified a statistical predominance from the 1,2,3,7,8-PeCDF (Pentachlorodibenzofuran) and 1,2,3,4,7,8-HxCDF (Hexachlorodibenzofuran) congeners, while dl-PCBs TEQs had similar correlation amongst combustion fuels with major contributions being from the PCB-126 and PCB-169 (3,3',4,4',5,5'-Hexachlorobiphenyl) congeners.

Bioaccumulation of metals and PCBs in Raja clavata

The goal of this study was to assess stable isotopes profiles, metals concentration and PCBs in Raja clavata muscle and liver, according to sex and size, and to elucidate its suitability as a Mid-Atlantic biomonitor. The results reflected bioaccumulation and suggested biomagnification processes for As and Hg in muscle tissue. Cd, Cu and Zn were detected in high amounts in liver, Cr, Mn and Rb were relatively stable and low, Pb was not detected and Sr was present in muscle at high levels, decreasing with length. Hg and Se were strongly correlated, suggesting a mitigation role. Both tissues presented low concentrations of PCBs, especially the dioxin-like congeners, although always higher in liver and not correlated with size. None of these contaminants exceed EU legislated limits. However, they need to be monitored given study area's location, volcanic nature and the expected increase of anthropogenic activity related to future prospective mining activities and the establishment of the Transatlantic Trade and Investment Partnership (TTIP) between Europe and the USA.

Comparison of the co-gasification of sewage sludge and food wastes and cost-benefit analysis of gasification- and incineration-based waste treatment schemes

The compositions of food wastes and their co-gasification producer gas were compared with the existing data of sewage sludge. Results showed that food wastes are more favorable than sewage sludge for co-gasification based on residue generation and energy output. Two decentralized gasification-based schemes were proposed to dispose of the sewage sludge and food wastes in Singapore. Monte Carlo simulation-based cost-benefit analysis was conducted to compare the proposed schemes with the existing incineration-based scheme. It was found that the gasification-based schemes are financially superior to the incineration-based scheme based on the data of net present value (NPV), benefit-cost ratio (BCR), and internal rate of return (IRR). Sensitivity analysis was conducted to suggest effective measures to improve the economics of the schemes.

Metals and PCB levels in some edible marine organisms from the Ionian Sea: dietary intake evaluation and risk for consumers

Concentrations of some metals (Cd, Cu, As, Hg, Pb) and polychlorinated biphenyls (PCBs) were investigated in edible marine organisms from different trophic levels and feeding behaviour like bivalve molluscs (Mytilus galloprovincialis and Chlamys glabra), gastropod molluscs (Hexaplex trunculus) and some commercial species of fish (Trachurus trachurus, Boops boops, Sarpa salpa and Gobius niger). These species were collected in the first inlet of the Mar Piccolo of Taranto (Ionian Sea, Southern Italy), classified as 'Site of National Interest' established by National Law 426 (1998) and included in the 'National Environmental Remediation and Restoration Projects'. The aim of this work was to investigate contamination levels and public health risks, associated with consuming seafood harvested from these areas. Moreover, in this study, was also estimated the weekly intake in children and adults, both for metals and PCBs. In comparison with the permissible limits set by EC Regulations, Cd and Pb levels were over the limit in the H. trunculus (in all sampling stations) and in the fish T. trachurus respectively. PCBs were over the legal limit in all sampled species with the exception of M. galloprovincialis (station 1), C. glabra and the herbivorous fish S. salpa. In the fish T. trachurus, for example, the concentration of six target PCBs was about five times higher than the EC limit. The estimated intakes of those trace elements included in this study through seafood consumption by the population exceed the provisional tolerable weekly intake recommended by the Joint FAO/WHO Expert Committee on Food Additives for Cd and Hg in the H. trunculus and T. trachurus, especially in children. Moreover, hazard quotience (HQ) for Hg and Cd was >1 in the children for T. trachurus and H. trunculus consumption. As regard non-dioxin-like PCB (NDL-PCB), the estimated intake were always above the 'provisional guidance value' (70 ng/kg body weight) Arnich et al. (Regul Toxicol Pharm 54: 287-2, 2009) for all sampled organism. Thus, health risks due to the dietary Hg, Cd and PCBs intake, especially for children, cannot be excluded. Therefore, an extended remediation programme is necessary to safeguard marine ecosystem, human health and, not less important, the economic activities, in the Taranto marine area.

Evaluation of relative effect potencies (REPs) for dioxin-like compounds to derive systemic or human-specific TEFs to improve human risk assessment

Toxic equivalency factors (TEFs) are generally applied for estimating human risk of dioxins and dioxin-like compounds using systemic (e.g., blood) levels, even though these TEFs are established based on intake doses in rodent studies. This review shows that systemic relative effect potencies (REPs) can deviate substantially from intake REPs, but are similar to in vitro-derived REPs. Interestingly, the in vitro REPs for 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) and 2,3,4,7,8-pentachlorodibenzofuran (4-PeCDF) are up to one order of magnitude higher than their in vivo REPs and WHO-TEFs, based on oral intake. In addition, clear species-differences in in vitro REPs were apparent for some congeners. Especially the human-derived REP for polychlorinated biphenyl 126 is one to two orders of magnitude lower than rodent REPs and its current WHO-TEF. Next, suggested adapted systemic or human-specific TEFs for these congeners were applied to calculate changes in systemic TEQ concentrations in studies from the USA, Germany and Japan and compared with either the JECFA TDI or USEPA RfD of TCDD. Overall, the effect of such TEF changes for these three congeners on total TEQ roughly balances each other out in the general population. However, results may be different for situations in which a specific group of congeners dominates. For those congeners that show a distinct deviation between either intake and systemic REPs or between rodent- and human-based in vitro REPs, we propose that especially REPs derived from human-based in vitro models are weighted more heavily in establishing systemic or human-specific TEF values to improve human health risk assessment.

Effect-directed analysis supporting monitoring of aquatic environments--An in-depth overview

Aquatic environments are often contaminated with complex mixtures of chemicals that may pose a risk to ecosystems and human health. This contamination cannot be addressed with target analysis alone but tools are required to reduce this complexity and identify those chemicals that might cause adverse effects. Effect-directed analysis (EDA) is designed to meet this challenge and faces increasing interest in water and sediment quality monitoring. Thus, the present paper summarizes current experience with the EDA approach and the tools required, and provides practical advice on their application. The paper highlights the need for proper problem formulation and gives general advice for study design. As the EDA approach is directed by toxicity, basic principles for the selection of bioassays are given as well as a comprehensive compilation of appropriate assays, including their strengths and weaknesses. A specific focus is given to strategies for sampling, extraction and bioassay dosing since they strongly impact prioritization of toxicants in EDA. Reduction of sample complexity mainly relies on fractionation procedures, which are discussed in this paper, including quality assurance and quality control. Automated combinations of fractionation, biotesting and chemical analysis using so-called hyphenated tools can enhance the throughput and might reduce the risk of artifacts in laboratory work. The key to determining the chemical structures causing effects is analytical toxicant identification. The latest approaches, tools, software and databases for target-, suspect and non-target screening as well as unknown identification are discussed together with analytical and toxicological confirmation approaches. A better understanding of optimal use and combination of EDA tools will help to design efficient and successful toxicant identification studies in the context of quality monitoring in multiply stressed environments.

Toxicokinetics of chiral polychlorinated biphenyls across different species--a review

Nineteen polychlorinated biphenyls (chiral or C-PCBs) exist as two stable rotational isomers (atropisomers) that are non-superimposable mirror images of each other. C-PCBs are released into the environment as racemic (i.e., equal) mixtures of both atropisomers and undergo atropisomeric enrichment due to biological, but not abiotic, processes. In particular, toxicokinetic studies provide important initial insights into atropselective processes involved in the disposition (i.e., absorption, distribution, biotransformation, and excretion) of C-PCBs. The toxicokinetic of C-PCBs is highly congener and species dependent. In particular, at lower trophic levels, abiotic processes play a predominant role in C-PCB toxicokinetics. Biotransformation plays an important role in the elimination of C-PCBs in mammals. The elimination of C-PCB follows the approximate order mammals > birds > amphibians > fish, mostly due to a corresponding decrease in metabolic capacity. A few studies have shown differences in the toxicokinetics of C-PCB atropisomers; however, more work is needed to understand the toxicokinetics of C-PCBs and the underlying biological processes. Such studies will not only contribute to our understanding of the fate of C-PCBs in aquatic and terrestrial food webs but also facilitate our understanding of human exposures to C-PCBs.

Lack of data drives uncertainty in PCB health risk assessments

Health risk assessments generally involve many extrapolations: for example, from animals to humans or from high doses to lower doses. Health risk assessments for PCBs involve all the usual uncertainties, plus additional uncertainties due to the nature of PCBs as a dynamic, complex mixture. Environmental processes alter PCB mixtures after release into the environment, so that people are exposed to mixtures that might not resemble the mixtures where there are toxicity data. This paper discusses the evolution of understanding in assessments of the cancer and noncancer effects of PCBs. It identifies where a lack of data in the past contributed to significant uncertainty and where new data subsequently altered the prevailing understanding of the toxicity of PCB mixtures, either qualitatively or quantitatively. Finally, the paper identifies some uncertainties remaining for current PCB health assessments, particularly those that result from a lack of data on exposure through nursing or on effects from inhalation of PCBs.

State of the art and advances in the impact assessment of dioxins and dioxin-like compounds

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) are toxic and persistent organic pollutants that are able to enter the food chain, accumulate in the fat tissues of animals, and consequently pose a serious risk for human health. Consolidated tools for exposure assessment have been implemented during the last decades and widely used, both in the environmental monitoring and in modeling activities. Although the emissive trend and the concentrations in the environment have gradually decreased during the last 20 years, some situations are still underrated and not adequately controlled by the environmental legislation. On the other hand, a complete monitoring of all the pathways of exposure to PCDD/Fs and PCBs is technically and economically unfeasible. Therefore, this paper aims at providing an overview of the traditional approaches used to assess the impacts of PCDD/Fs and PCBs and presenting the novelties introduced during the last years. After an initial characterization of their toxicity and their effects on health, this paper focuses on activities and situations that can result in critical releases of PCDD/Fs and PCBs into the atmosphere and that can represent a hidden threat for the population. In the final part, this study presents the current methodologies for exposure assessment, summarizes the food chain models in a unified way, and puts the light on new methods that can help environmental scientists, risk assessors, and decision makers to estimate the risk related to exposure to PCDD/Fs in different contexts.

Non-dioxin-like and dioxin-like polychlorinated biphenyls in butter sampled from the Polish retail market

The aim was to investigate levels of polychlorinated biphenyls (PCBs) in butter available on the Polish retail market. A gas chromatography-based method was developed for the purpose of this study. An ion-trap mass spectrometer was used as a detection system with high-resolution chromatography. Recoveries of individual PCBs from spiked samples varied from 58% to 105% with a recovery relative standard deviation in the range 3-16%. Levels of eight non-dioxin-like and twelve dioxin-like congeners were determined. Toxic equivalent factors (TEQs) were calculated using World Health Organization (WHO) TEQs. The average concentration of the sum of six PCBs (28, 52, 101, 138, 153, and 180) was found to be 1561±728 pg g(-1) (fat) and the upper-bound concentrations of dioxin-like congeners were (1 standard deviation uncertainty) 0.441±0.384 pg PCB-TEQ g(-1) (fat).

Uptake of PCBs contained in marine sediments by the green macroalga Ulva rigida

The uptake of PCBs contained in marine sediments by the green macroalga Ulva rigida was investigated in both laboratory and field experiments. Under laboratory conditions, total PCBs (tPCBs) uptake was significantly greater in live vs dead plants. The concentration of tPCB taken up in live plants was greatest in the first 24h (1580 μg kg(-1) dry weight), and then increased at a lower rate from day 2 to 14. Dead plants had a significantly lower tPCB concentration after 24h (609 μg kg(-1) dry weight) and lower uptake rate through day 14. Lesser chlorinated PCB congeners (below 123) made up the majority of PCBs taken up. Congener composition in both laboratory and field experiments was correlated to congener logKow value and sediment content. Field experiments showed that Ulva plants could concentrate PCBs to 3.9 mg kg(-1) in 24h. Thus, U. rigida is capable of removing PCBs in sediments at a rapid rate.

Efficacy of carbonaceous materials for sorbing polychlorinated biphenyls from aqueous solution

Interest in incorporating nanomaterials into water treatment technologies is steadily growing, driving the necessity to understand the interaction of these new materials with specific water contaminants. In the present study, five different carbonaceous materials: activated carbon (AC), charcoal (BC), carbon nanotubes (CNT), graphene (GE), and graphene oxide (GO) were investigated as sorbent materials for 11 polychlorinated biphenyl (PCB) congeners in aqueous concentrations in the pg-μg/L range. Sorbent-water distribution coefficients (Ks) calculated in aqueous concentrations of ng/L show that AC is superior to GE, GO, CNT, and BC for the 11 PCB congeners investigated by an average of 1.1, 1.1, 1.3, and 2.5 orders of magnitude, respectively. Additionally, maximum capacity and sorption affinity parameters from the Langmuir, Freundlich, and Polanyi-Dubinin-Manes (PDM) models show a similar result. Interestingly, however, the effect of molecular planarity has greater impact on PCB sorption to the nanomaterials, such that the planar congeners form stronger bonds with CNT, GE, and GO compared to AC and BC. This work demonstrated superior PCB sorption by AC as compared with the nanomaterials examined such that substantial post production modifications would be necessary for the nanomaterials to out-perform AC.

In vitro bioassays for detecting dioxin-like activity--application potentials and limits of detection, a review

Use of in vitro assays as screening tool to characterize contamination of a variety of environmental matrices has become an increasingly popular and powerful toolbox in the field of environmental toxicology. While bioassays cannot entirely substitute analytical methods such as gas chromatography-mass spectrometry (GC-MS), the increasing improvement of cell lines and standardization of bioassay procedures enhance their utility as bioanalytical pre-screening tests prior to more targeted chemical analytical investigations. Dioxin-receptor-based assays provide a holistic characterization of exposure to dioxin-like compounds (DLCs) by integrating their overall toxic potential, including potentials of unknown DLCs not detectable via e.g. GC-MS. Hence, they provide important additional information with respect to environmental risk assessment of DLCs. This review summarizes different in vitro bioassay applications for detection of DLCs and considers the comparability of bioassay and chemical analytically derived toxicity equivalents (TEQs) of different approaches and various matrices. These range from complex samples such as sediments through single reference to compound mixtures. A summary of bioassay derived detection limits (LODs) showed a number of current bioassays to be equally sensitive as chemical methodologies, but moreover revealed that most of the bioanalytical studies conducted to date did not report their LODs, which represents a limitation with regard to low potency samples.

Polychlorinated dioxins, furans (PCDD/Fs), and polychlorinated biphenyls (PCBs) and their trends in Canadian human milk from 1992 to 2005

More than 300 samples of human milk were collected from individuals residing in various regions across Canada in the years 1992 to 2005. The milks were taken from the main populated areas east to west in southern Canada as well as from the region of Nunavik in northern Quebec and analysed for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs). The concentrations, expressed in ng kg(-1) milk lipid, show an overall decrease of virtually all compounds examined including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), World Health Organization 2005 toxic equivalents (WHO2005-TEQ) PCDD/PCDFs, WHO2005-TEQ dioxin-like PCBs (dl-PCBs), and total PCBs. Median values of 2,3,7,8-TCDD changed from about 1.5 ng kg(-1) milk lipid in 1992 to 0.8 ng kg(-1) in 2005 while the median WHO2005-TEQ PCDD/F fell from about 14-7 ng kg(-1) milk lipid in the same period. The concentrations of PCDD/Fs and PCBs in samples from Nunavik, which is in Arctic Quebec, were higher than those observed in milk from southern Quebec although this difference was not large. Over two time periods, milk samples from Hamilton, Ontario showed slightly higher levels of PCBs than Austin, Texas, USA--a North American city of similar size and development but with more than twice the PBDE exposure. When compared with earlier human milk data going back to the early 1980s, this large data set shows a steady decline of human exposure to POPs in Canada by a factor of about four times.

Polychlorinated dioxins, furans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs) and indicator PCBs (ind-PCBs) in egg and egg products in Turkey

The aim of the study is to determine concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyls (dl-PCBs) and indicator PCBs (ind-PCBs) in eggs from cage hens without soil contact, pasteurized egg samples and imported egg yolk powder samples in Turkey. Concentrations of PCDD/Fs, PCDD/Fs and dl-PCBs, and ind-PCBs in eggs and pasteurized egg samples are in the range of 0.247-1.527 pg WHO-TEQ(2005)g(-1) fat, 0.282-1.762 pg WHO-TEQ(2005)g(-1) fat and 202-1,235 pg g(-1) fat, respectively. For egg yolk powder samples, concentrations of PCDD/Fs, PCDD/Fs and dl-PCBs, and ind-PCBs are in the range of 0.122-0.494 pg WHO-TEQ(2005)g(-1) fat, 0.214-0.640 pg WHO-TEQ(2005)g(-1) fat and 217-1,498 pg g(-1) fat, respectively. All results for PCDD/Fs, PCDD/Fs and dl-PCBs, and ind-PCBs are below the values of 2.5 pg WHO-TEQ(2005)g(-1) fat, 5.0 pg WHO-TEQ(2005)g(-1) fat and 40 ng g(-1) fat imposed in Turkish Regulation for eggs and egg products, respectively. In all samples 2,3,4,7,8-PeCDF, 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD and PCB126 are the most prominent congeners. Mean estimated daily exposure to PCDD/Fs and dl-PCBs for Turkish population from egg is 0.011 pg WHO-TEQ(2005)d(-1)kg body weight (bw)(-1). Although the exposure levels are below the TDI of 2 pg WHO-TEQ(1998)kg bw(-1), the results were based only on consumption of egg. In order to estimate total dietary intake for Turkish population, various food items should be investigated.