Preliminary study on brominated dioxins/furans and hydroxylated/methoxylated PBDEs in Baltic cod (Gadus morhua) liver. Comparison to the levels of analogue chlorinated co-occurring pollutants

PCDD/Fs and PCBs in Baltic fish - Recent data, risk for consumers

This study determines the levels of PCDD/Fs and PCBs in Baltic fish caught in ICES areas 24, 25, and 26, and the related risk for fish consumers in relation to the newly established Tolerable Weekly Intake dose (TWI) (2 pg WHO-TEQ kg -^-1 body weight). The total PCDD/F/DL-PCBs toxic equivalents in the fish muscle ranged from 0.12 to 10.34 pg WHO-TEQ g - ^-1 wet weight. Salmon muscles contained the highest average concentration and cod the lowest, below 0.5 pg WHO-TEQ g - ^-1 wet weight of total TEQ. The average intake of PCDD/F/DL-PCBs (portion of fish 200 g) was 91-2420% of the TWI for children, and 30-799% of the TWI for adults. It appears that despite the decreased levels of PCDD/F and PCBs in Baltic fish, in relation to the newly established TWI dose, this decrease is not enough to make the Baltic fish safe for frequent consumers.

Polybrominated dibenzo-p-dioxins and furans (PBDD/Fs): Contamination in food, humans and dietary exposure

Polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) have been recognised as environmental pollutants for decades but their occurrence in food has only recently been reported. They elicit the same type of toxic response as analogous polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) with similar potencies and effects, and share similar origins - inadvertent production during combustion and occurrence as by-products in industrial chemicals. Surprisingly, PBDD/Fs have received considerably less attention than PCDD/Fs, perhaps because determination requires a higher degree of analytical competence, a result of the higher adsorptivity and lability associated with carbon-bromine bonding. For most populations, the principal exposure pathway is dietary intake. The PBDD/F toxicity arising from occurrence in foods has often been expressed as toxic equivalents (TEQs) using the same scheme developed for PCDD/Fs. This approach is convenient, but resulting TEQ estimates are more uncertain, given the known differences in response for some analogous congeners and also the different patterns of PBDD/F occurrence confirmed by the newer data. Further studies to consolidate potency factors would help to refine TEQ estimates. Characteristically, most foods and human tissues show more frequent and higher PBDF concentrations relative to PBDDs, reflecting major source patterns. Occurrence in food ranges from <0.01 to several thousand pg/g (or up to 0.3 pg TEQ/g whole weight) which is comparable to PCDD/F occurrence (ΣPBDD/F TEQs are underestimated as not all relevant congeners are included). Plant based foods show higher PBDD/F: PCDD/F TEQ ratios. Reported PBDD/F dietary intakes suggest that some population groups, particularly young children, may exceed the revised tolerable weekly intake for dioxin-like contaminants (2 pg TEQ/kg bw/week), even for mean consumption estimated with lower bound data. It is evident that the omission of PBDD/Fs from the TEQ scheme results in a significant underestimation of the cumulative toxicity and associated risk arising from this mode of action.

Polybrominated dibenzo-p-dioxins (PBDDs) and - dibenzofurans (PBDFs) in cod (Gadus morhua) liver-derived products from 1972 to 2017

Literature data on the occurrence and prevalence of polybrominated dibenzo-p-dioxins (PBDDs) and polybrominated dibenzofurans (PBDFs) in foods including seafood are scarce. In this study, a number of cod-derived products including medicinal grade cod liver oils sourced from Northern Atlantic waters (Iceland, Norway) and the Baltic Sea (Poland) during 1972-2001 and canned cod liver sourced from the Baltic Sea in 2017, showed detectable levels of PBDFs: such as 2,3,8-TrBDF at 0.57 to 5.249 pg g^-1 fat and 1,2,3,4,6,7,8-HpBDF at <0.018 to 0.302 pg g^-1 fat. PBDDs were not detected in the cod liver oils. Canned cod liver products showed low levels of 2,3,7,8-TeBDD in the range <0.017 to 0.022 pg g^-1 whole weight and 1,2,3,7,8-PeBDD at <0.03 to 0.039 pg g^-1 whole weight. These concentrations were computed to yield upper bound toxic equivalences (TEQs) of 0.14 to 0.17 pg g^-1 for the oils and 0.12 to 0.25 pg g^-1 for the canned products (0.08 pg g^-1 ww for both products). The resulting supplementary and dietary intakes are low (0.02 to 0.11 pg kg^-1 bm day^-1 for the oils and 0.07 to 0.17 pg kg^-1 bm week^-1 for the canned livers) in comparison to the recently expressed tolerable weekly intake of 2 pg kg^-1 bm week^-1. However, the intakes are underestimates, as due to a lack of analytical standards not all PBDD/F TEQ contributing congeners could be included. The PBDD/F TEQ contributes to the cumulative toxicity arising from other contaminants such as chlorinated dioxins and polychlorinated biphenyls.

Levels and temporal trends of persistent organic pollutants (POPs) in Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) from the southern Barents Sea

Liver samples of two gadoid species, Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus), sampled in the southern Barents Sea in the period 1992-2015, were studied for the levels of six types of persistent organic pollutants (POPs): polychlorinated biphenyls (PCBs), chlorinated organic pesticides (DDTs, hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), trans-nonachlor (TNC)), and polybrominated diphenyl ethers (PBDEs). Higher average levels were found in cod than in haddock. Sampling approximately every third year allowed studies of temporal trends for all the compound groups except PBDEs. Time series are reported for 1992-2015 for Atlantic cod and for 1998-2015 for haddock. Decreasing temporal trends have been modeled in cod for the analyzed POPs for this time period. The decrease seems to be slowing down in the later years. HCB levels showed least decrease with time among all the contaminants, with the poorest fit to the proposed model. Similar time trends were found in haddock, but the decrease is less apparent due to shorter time series. The observed time trends of legacy POPs document the effectiveness of efforts during the 1990s to reduce the levels of these contaminants in the marine environment but question the possibility to eliminate them altogether from the marine environment in the foreseeable future.

Endocrine disrupting potency of organic pollutant mixtures isolated from commercial fish oil evaluated in yeast-based bioassays

The aim of this work was to evaluate the activity of xenobiotic mixtures containing persistent organic pollutants isolated from commercial fish oil samples against sex hormone receptors, including estrogen and androgen. The applied bioassay was based on transgenic yeast strains. The mixtures were extracted from the samples using the semi-permeable membrane dialysis technique and analyzed with gas chromatography/ion trap mass spectrometry. It turned out that mixtures of chemicals isolated from fish oil may interact with human steroid sex hormone receptors in various ways: the tested samples showed both estrogenic and anti-androgenic activity. Calculated 17β-estradiol equivalents for the tested samples ranged between 0.003 and 0.073 pg g-1 (fat). Anti-androgenic activity expressed as the flutamide equivalent concentration was in the 18.58-216.21 ng g-1 (fat) range. Polychlorinated biphenyls and various DDT metabolites were the main fish oil pollutants influencing the receptors. Additivity and/or synergy between chemicals was observed in the ER/AR mediated response.

Optimized yeast-based in vitro bioassay for determination of estrogenic and androgenic activity of hydroxylated / methoxylated metabolites of BDEs / CBs and related lipophilic organic pollutants

Persistent organic pollutants (POPs) are known to show endocrine disrupting (ED) activity, including interactions with hormone receptors. The aim of this work was to develop a bioassay applicable for evaluation of ED potency of highly lipophilic metabolites of POPs. To that end, a yeast-based bio-assay protocol was used. Estrogenic / androgenic activity of some native brominated biphenyl ethers (BDEs) / chlorinated biphenyls (CBs), and their hydroxylated / methoxylated metabolites was assessed. Since data (including potency compared to reference native hormones) obtained using different protocols vary, the possibility that yeast transforms POPs into some more potent compounds was first checked; it seems that no such transformation is important from the test applicability standpoint. The developed method was sensitive with EC50 values 6.5*10^-11 M and 4.5*10^-9 M calculated for E2 and DHT, respectively. Both CBs and BDEs show weak estrogenic activity negatively correlated with the degree of their halogenation, but their metabolites are significantly more potent xenohormones. 4-OH-2,2',4',6'-TeCB was the most potent estrogen receptor (ER) agonist among all tested compounds; its activity was only 1,000 times lower than that of native E2.

Temporal trends of PBDD/Fs, PCDD/Fs, PBDEs and PCBs in ringed seals from the Baltic Sea (Pusa hispida botnica) between 1974 and 2015

Temporal trends in exposure to persistent organic pollutants (POPs) were assessed in 22 pooled samples gathered from 69 individuals of Baltic ringed seal (Pusa hispida botnica) from 1974 to 2015. Samples were analysed for polybrominated dibenzo-p-dioxins and furans (PBDD/Fs), polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs). No previous study has reported on the occurrence of PBDD/Fs in marine mammals in the Baltic Sea. Concentrations of pollutants in Baltic ringed seal, a marine mammal and top predator, can be used as an indicator of pollutants concentrations in the Baltic region. Visual inspection of data did not show any temporal trends for PBDD/Fs, while the PCDD/Fs and PCBs showed decreasing concentrations between 1974 and 2015. PBDEs increased until the end of the 1990s and then decreased until the end of the period. ∑PBDD/Fs ranged from 0.5-52.3pg/g lipid weight (l.w.) (0.08-4.8pgTEQ/g l.w.), with 1,2,3,4,6,7,8-HpBDF contributing on average 61% to ∑PBDD/Fs. ∑PCDD/Fs ranged from 103 to 1480pg/g l.w. (39-784pgTEQ/g l.w.), with 1,2,3,6,7,8-HxCDD, 1,2,3,7,8-PeCDD and 2,3,4,7,8-PeCDF showing the highest average concentrations. PBDD/F toxic equivalents (TEQ) contributed on average 1.1% to the total (PBDD/F+PCDD/F) TEQ. The ∑PBDEs concentration range was 18.7-503ng/g l.w., with BDE #47 the predominant congener. The concentration range for ∑PCBs was 2.8-40.1μg/g l.w., with #138 and #153 the most abundant congeners. Visual inspection of the data showed decreasing concentrations for all compound groups except PBDD/Fs. A slight increase in the PBDD/Fs concentrations was observed from 2004 onwards. This observation needs to be investigated further.

Occurrence of polybrominated dibenzo-p-dioxins, dibenzofurans (PBDD/Fs) and polybrominated diphenyl ethers (PBDEs) in pilot whales (Globicephala melas) caught around the Faroe Islands

Blubber from Faroese pilot whales (Globicephala melas) was analysed for brominated dioxins PBDD/Fs, with a subset also analysed for chlorinated dioxins, PCDD/Fs. The studied individuals were restricted to juvenile male whales sampled in the Faroe Islands during the period 1997-2013. Among the PBDD/Fs, the furans were predominant, although the relative abundance of various congeners differed between samples. Furans accounted for, on average, 79% of the ∑PBDD/Fs in the samples, with 1,2,3,4,6,7,8-HpBDF the most abundant congener, found in half of the analysed pilot whales. The concentration range for ∑PBDD/Fs among the samples was 0.080-71 pg/g l.w. (lipid weight), and the sum of toxic equivalents ranged from 0.0039 to 4.7 pg TEQ/g l.w. No relationship was found between PBDD/Fs and PCDD/Fs. In addition, 20 pilot whale samples from the period 2010-2013 were analysed for PBDEs. Several PBDE congeners were found in all of the sampled pilot whales, and at noticeably higher levels than PBDD/Fs and PCDD/Fs. The ∑PBDEs ranged from 140 to 1900 ng/g l.w., with BDE #47 the most abundant congener detected in the samples. Results from the present study were then compared with data from previous studies on pilot wales to investigate temporal trends between 1986 and 2013. The comparison indicated that PBDE concentrations in juvenile males have decreased from 1996 to the latest observations in 2013. No relationship between the concentration levels of PBDD/Fs and PBDEs in the sampled pilot whales could be identified, which indicates possible differences in the metabolism of, or exposure to, PBDEs and PBDD/Fs.

Uptake and biotransformation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) in four marine microalgae species

Hydroxylated- and methoxylated- polybrominated diphenyl ethers (OH-PBDEs and MeO-PBDEs) are more toxic than PBDEs and occur widely in the marine environment, and yet their origins remain controversial. In this study, four species of microalgae (Isochrysis galbana, Prorocentrum minimum, Skeletonema grethae and Thalassiosira pseudonana) were exposed to BDE-47, which is synthetic and is the predominant congener of PBDEs in the environment. By chemical analysis after incubation of 2 to 6 days, the efficiency of uptake of BDE-47 and, more importantly, the potential of undergoing biotransformation to form OH-PBDEs and MeO-PBDEs by the microalgae were investigated. Growth rates of these axenic microalgae were not affected upon exposure to environmentally relevant concentrations (0.2–20 μg BDE-47 L⁻¹), and accumulation ranged from 0.772 ± 0.092 μg BDE-47 g⁻¹ lipid to 215 ± 54 μg BDE-47 g⁻¹ lipid within 2 days. Debromination of BDE-47 and formation of BDE-28 occurred in all microalgae species (0.01 to 0.87%), but biotransformation to OH-PBDEs was only found in I. galbana upon exposure to extremely high concentration. The results of this study showed that biotransformation of microalgae species is unlikely an explanation for the OH-PBDEs and MeO-PBDEs found in the marine environment.