Persistence of PFOA Pollution at a PTFE Production Site and Occurrence of Replacement PFASs in English Freshwaters Revealed by Sentinel Species, the Eurasian Otter (Lutra lutra).

Concentrations of 33 PFASs were determined in 20 Eurasian otters, sampled 2015-2019, along a transect away from a factory, which used PFOA in PTFE manufacture. Despite cessation of usage in 2012, PFOA concentrations remained high near the factory (>298 µg/kg ww <20 km from factory) and declined with increasing distance (<57 µg/kg ww >150 km away). Long-chain legacy PFASs dominated the Σ33PFAS profile, particularly PFOS, PFOA, PFDA, and PFNA. Replacement compounds, PFECHS, F-53B, PFBSA, PFBS, PFHpA, and 8:2 FTS, were detected in ≥19 otters, this being the first report of PFBSA and PFECHS in the species. Concentrations of replacement PFASs were generally lower than legacy compounds (max: 70.3 µg/kg ww and 4,640 µg/kg ww, respectively). Our study underscores the utility of otters as sentinels for evaluating mitigation success and highlights the value of continued monitoring to provide insights into the longevity of spatial associations with historic sources. Lower concentrations of replacement, than legacy, PFASs likely reflect their lower bioaccumulation potential, and more recent introduction. Continued PFAS use will inevitably lead to increased environmental and human exposure if not controlled. Further research is needed on fate, toxicity, and bioaccumulation of replacement compounds.

Spatiotemporal Trends Spanning Three Decades Show Toxic Levels of Chemical Contaminants in Marine Mammals.

Despite their ban and restriction under the 2001 Stockholm Convention, persistent organic pollutants (POPs) are still widespread and pervasive in the environment. Releases of these toxic and bioaccumulative chemicals are ongoing, and their contribution to population declines of marine mammals is of global concern. To safeguard their survival, it is of paramount importance to understand the effectiveness of mitigation measures. Using one of the world's largest marine mammals strandings data sets, we combine published and unpublished data to examine pollutant concentrations in 11 species that stranded along the coast of Great Britain to quantify spatiotemporal trends over three decades and identify species and regions where pollutants pose the greatest threat. We find that although levels of pollutants have decreased overall, there is significant spatial and taxonomic heterogeneity such that pollutants remain a threat to biodiversity in several species and regions. Of individuals sampled within the most recent five years (2014-2018), 48% of individuals exhibited a concentration known to exceed toxic thresholds. Notably, pollutant concentrations are highest in long-lived, apex odontocetes (e.g., killer whales (Orcinus orca), bottlenose dolphins (Tursiops truncatus), and white-beaked dolphins (Lagenorhynchus albirostris)) and were significantly higher in animals that stranded on more industrialized coastlines. At the present concentrations, POPs are likely to be significantly impacting marine mammal health. We conclude that more effective international elimination and mitigation strategies are urgently needed to address this critical issue for the global ocean health.

Evaluation of a marine mammal status and trends contaminants indicator for European waters.

Marine mammals are vulnerable to the bioaccumulation, biomagnification and lactational transfer of specific types of pollutants, such as industrial polychlorinated biphenyls (PCBs), due to their long-life spans, feeding at a high trophic level and unique fat stores that can serve as depots for these lipophilic contaminants. Currently, European countries are developing indicators for monitoring pollutants in the marine environment and assessing the state of biodiversity, requirements under both Regional Seas Conventions and European legislation. As sentinel species for marine ecosystem and human health, marine mammals can be employed to assess bioaccumulated contaminants otherwise below current analytical detection limits in water and lower trophic level marine biota. To aid the development of Regional Seas marine mammal contaminants indicators, as well as Member States obligations under descriptor 8 of the EU Marine Strategy Framework Directive, the current study aims to further develop appropriate methodological standards using data collected by the established UK marine mammal pollutant monitoring programme (1990 to 2017) to assess the trends and status of PCBs in harbour porpoises. Within this case study, temporal trends of PCB blubber concentration in juvenile harbour porpoises were analysed using multiple linear regression models and toxicity thresholds for the onset of physiological (reproductive and immunological) endpoints were applied to all sex-maturity groups. Mean PCB blubber concentrations were observed to decline in all harbour porpoise Assessment Units and OSPAR Assessment Areas in UK waters. However, a high proportion of animals were exposed to concentrations deemed to be a toxicological threat, though the relative proportion declined in most Assessment Units/Areas over the last 10 years of the assessment. Recommendations were made for improving the quality of the assessment going forward, including detailing monitoring requirements for the successful implementation of such an indicator.

Anthropogenic Drivers of Variation in Concentrations of Perfluoroalkyl Substances in Otters (Lutra lutra) from England and Wales.

Per- and polyfluoroalkyl substances (PFASs) are ubiquitous environmental contaminants that have been linked to adverse health effects in wildlife and humans. Here, we report the presence of PFASs in Eurasian otters (Lutra lutra) in England and Wales and their association with anthropogenic sources. The following 15 compounds were analyzed: 10 perfluoroalkyl carboxylic acids (PFCAs), 4 perfluoroalkyl sulfonic acids (PFSAs), and perfluorooctane sulfonamide, in livers of 50 otters which died between 2007 and 2009. PFASs were detected in all otters analyzed, with 12/15 compounds detected in ≥80% of otters. Perfluorooctane sulfonate (PFOS) accounted for 75% of the ΣPFAS profile, with a maximum concentration of 6800 µg/kg wet weight (ww). Long-chain (≥C8) PFCAs accounted for 99.9% of the ΣPFCA profile, with perfluorodecanoic acid and perfluorononanoic acid having the highest maxima (369 µg/kg ww and 170 µg/kg ww, respectively). Perfluorooctanoic acid (PFOA) concentrations were negatively associated with the distance from a factory that used PFOA in polytetrafluoroethylene manufacture. Most PFAS concentrations in otters were positively associated with load entering wastewater treatment works (WWTW) and with arable land, suggesting that WWTW effluent and sewage sludge-amended soils are significant pathways of PFASs into freshwaters. Our results reveal the widespread pollution of British freshwaters with PFASs and demonstrate the utility of otters as effective sentinels for spatial variation in PFAS concentrations.

Decabromodiphenylether trends in the European environment: Bird eggs, sewage sludge and surficial sediments.

Concern on relatively high levels and the potential bioaccumulation of decabromodiphenylether (BDE209) has led to a European 8-year monitoring program on trends in BDE209 concentrations in birds, sewage sludge and sediments from seven countries. BDE209 was analysed in four environmental matrices: sparrowhawk eggs (UK), glaucous gull eggs (Bear Island, Norway), sewage sludge (UK, Ireland and the Netherlands) and sediment (France, Germany, the Netherlands, UK and Ireland). BDE209 was detected in most of the glaucous gull and sparrow hawk eggs but neither increasing nor decreasing trends in these BDE209 levels were observed. An indication for debromination of BDE209 in sparrowhawk eggs was found. BDE209 concentrations in sediments ranged from very low ng/g (88 ng/g on an organic carbon (OC) basis) concentrations, in the rivers Elbe, Ems, Seine and the Outer Humber, to high µg/g (120 µg/g OC), in the Western Scheldt, Liverpool Bay and River Mersey. Apart from decreasing values in the Western Scheldt sediment no further decreases in BDE209 concentrations were observed over time, neither in sediment nor in sewage sludge showing that the voluntary emissions control program of the bromine industry only had a local effect. In contrast to the sewage sludge samples from the Netherlands (mean 355 ng/g dry weight (dw) or 1026 ng/g OC), the BDE209 concentrations in the UK increased at all sites from 2006 to 2011 (8092 ng/g dw or 22,367 ng/g OC). The BDE209 levels in several UK sediments and sewage sludge were still very high at the end of the program in 2012, most likely caused by frequent use of BDE209 in the textile industry. This may be indicative of the persistence of BDE209 and the limited degradation into lower brominated congeners in sediment, although it cannot be excluded that ongoing BDE209 emissions have played a role as well.

Polychlorinated biphenyls are associated with reduced testes weights in harbour porpoises (Phocoena phocoena).

Polychlorinated biphenyls (PCBs) are highly toxic and persistent aquatic pollutants that are known to bioaccumulate in a variety of marine mammals. They have been associated with reduced recruitment rates and population declines in multiple species. Evidence to date documents effects of PCB exposures on female reproduction, but few studies have investigated whether PCB exposure impacts male fertility. Using blubber tissue samples of 99 adult and 168 juvenile UK-stranded harbour porpoises (Phocoena phocoena) collected between 1991 and 2017, here we show that PCBs exposures are associated with reduced testes weights in adults with good body condition. In animals with poor body condition, however, the impact of PCBs on testes weights was reduced, conceivably due to testes weights being limited by nutritional stress. This is the first study to investigate the relationship between PCB contaminant burden and testes weights in cetaceans and represents a substantial advance in our understanding of the relationship between PCB exposures and male reproductive biology in cetaceans. As testes weight is a strong indicator of male fertility in seasonally breeding mammals, we suggest the inclusion of such effects in population level impact assessments involving PCB exposures. Given the re-emergent PCB threat our findings are globally significant, with potentially serious implications for long-lived mammals. We show that more effective PCB controls could have a substantial impact on the reproductive health of coastal cetacean species and that management actions may need to be escalated to ensure adequate protection of the most vulnerable cetacean populations.

Persistent contaminants in adipose fins of returning adult salmonids to the river Tees (UK).

We report on concentrations of polybrominated diphenylethers (PBDEs), polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p'-DDE) and hexachlorobenzene (HCB) measured in the adipose fins of returning adult Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) to the river Tees in the Northeast of England. Overall, higher concentrations of these contaminants were found in sea trout samples, where detected congeners reflected the more widely used commercial formulations, in particular for the PBDEs. Our results suggest that these fish could be bioaccumulating persistent organic pollutants via diet during their migratory routes (North Sea and the Norwegian Sea) and, in addition, some level of re-mobilisation of these compounds could still be occurring in the UK eastern coastal areas. The use of adipose fin of returning salmonids could be further developed as a non-lethal approach to assess whether persistent contaminants are being accumulated during the juvenile to adult phase of salmonids originating from UK rivers.

Levels of Polychlorinated Biphenyls Are Still Associated with Toxic Effects in Harbor Porpoises (Phocoena phocoena) Despite Having Fallen below Proposed Toxicity Thresholds.

Polychlorinated biphenyls (PCBs) are toxic, persistent, and lipophilic chemical compounds that accumulate to high levels in harbor porpoises (Phocoena phocoena) and other cetaceans. It is important to monitor PCBs in wildlife, particularly in highly exposed populations to understand if concentrations are declining and how levels relate to toxicological thresholds and indices of health like infectious disease mortality. Here we show, using generalized additive models and tissue samples of 814 U.K.-stranded harbor porpoises collected between 1990 and 2017, that mean blubber PCB concentrations have fallen below the proposed thresholds for toxic effects. However, we found they are still associated with increased rates of infectious disease mortality such that an increase in PCB blubber concentrations of 1 mg kg-1 lipid corresponds with a 5% increase in risk of infectious disease mortality. Moreover, rates of decline and levels varied geographically, and the overall rate of decline is slow in comparison to other pollutants. We believe this is evidence of long-term preservation in the population and continued environmental contamination from diffuse sources. Our findings have serious implications for the management of PCB contamination in the U.K. and reinforce the need to prevent PCBs entering the marine environment to ensure that levels continue to decline.

Juvenile harbor porpoises in the UK are exposed to a more neurotoxic mixture of polychlorinated biphenyls than adults.

Polychlorinated biphenyls (PCBs) are a group of 209 persistent and bio-accumulative toxic pollutants present as complex mixtures in human and animal tissues. Harbor porpoises accumulate some of the highest levels of PCBs because they are long-lived mammals that feed at a high trophic level. Studies typically use the sum of a suite of individual chlorobiphenyl congeners (CBs) to investigate PCBs in wildlife. However, toxic effects and thresholds of CB congeners differ, therefore population health risks of exposure may be under or over-estimated dependent on the congener profiles present. In this study, we found congener profiles varied with age, sex and location, particularly between adult females and juveniles. We found that adult females had the highest proportions of octa-chlorinated congeners whilst juveniles had the highest proportions of tri- and tetra-chlorinated congeners. This is likely to be a consequence of pollutant offloading between mothers and calves during lactation. Analysis of the individual congener toxicities found that juveniles were exposed to a more neurotoxic CB mixture at a time when they were most vulnerable to its effects. These findings are an important contribution towards our understanding of variation in congener profiles and the potential effects and threats of PCB exposure in cetaceans.

Linking organochlorine contaminants with demographic parameters in free-ranging common bottlenose dolphins from the northern Adriatic Sea.

Marine top predators, including marine mammals, are known to bio-accumulate persistent pollutants such as polychlorinated biphenyls (PCBs), a serious conservation concern for these species. Although PCBs declined in European seas since the 1970s-1980s ban, considerable levels still persist in European and Mediterranean waters. In cetaceans, stranded animals are a valuable source of samples for pollutant studies, but may introduce both known and unknown biases. Biopsy samples from live, free-ranging cetaceans offer a better alternative for evaluating toxicological burdens of populations, especially when linked to known histories of identified individuals. We evaluated PCB and other organochlorine contaminants in free-ranging common bottlenose dolphins (Tursiops truncatus) from the Gulf of Trieste (northern Adriatic Sea), one of the most human-impacted areas in the Mediterranean Sea. Biopsies were collected from 32 male and female dolphins during 2011-2017. All animals were photo-identified and are part of a well-known population of about 150 individuals monitored since 2002. We tested for the effects of sex, parity and social group membership on contaminant concentrations. Males had significantly higher organochlorine concentrations than females, suggesting offloading from reproducing females to their offspring via gestation and/or lactation. Furthermore, nulliparous females had substantially higher concentrations than parous ones, providing further support for maternal offloading of contaminants. Overall, 87.5% of dolphins had PCB concentrations above the toxicity threshold for physiological effects in experimental marine mammal studies (9 mg/kg lw), while 65.6% had concentrations above the highest threshold published for marine mammals based on reproductive impairment in ringed seals (41 mg/kg lw). The potential population-level effects of such high contaminant levels are of concern particularly in combination with other known or suspected threats to this population. We demonstrate the utility of combining contaminant data with demographic parameters such as sex, reproductive output, etc., resulting from long-term studies.

Predicting global killer whale population collapse from PCB pollution.

Killer whales (Orcinus orca) are among the most highly polychlorinated biphenyl (PCB)-contaminated mammals in the world, raising concern about the health consequences of current PCB exposures. Using an individual-based model framework and globally available data on PCB concentrations in killer whale tissues, we show that PCB-mediated effects on reproduction and immune function threaten the long-term viability of >50% of the world's killer whale populations. PCB-mediated effects over the coming 100 years predicted that killer whale populations near industrialized regions, and those feeding at high trophic levels regardless of location, are at high risk of population collapse. Despite a near-global ban of PCBs more than 30 years ago, the world's killer whales illustrate the troubling persistence of this chemical class.

Inter-individual differences in contamination profiles as tracer of social group association in stranded sperm whales.

Ecological and physiological factors lead to different contamination patterns in individual marine mammals. The objective of the present study was to assess whether variations in contamination profiles are indicative of social structures of young male sperm whales as they might reflect a variation in feeding preferences and/or in utilized feeding grounds. We used a total of 61 variables associated with organic compounds and trace element concentrations measured in muscle, liver, kidney and blubber gained from 24 sperm whales that stranded in the North Sea in January and February 2016. Combining contaminant and genetic data, there is evidence for at least two cohorts with different origin among these stranded sperm whales; one from the Canary Island region and one from the northern part of the Atlantic. While genetic data unravel relatedness and kinship, contamination data integrate over areas, where animals occured during their lifetime. Especially in long-lived animals with a large migratory potential, as sperm whales, contamination data may carry highly relevant information about aggregation through time and space.

Spatial and temporal analysis of the risks posed by polychlorinated biphenyl and metal contaminants in dab (Limanda limanda) collected from waters around England and Wales.

The metals cadmium, mercury and lead, and the ICES7 CB levels were analysed in the common dab Limanda limanda to investigate whether concentrations of these determinants are at levels above established OSPAR assessment criteria around England and Wales. The results indicate that CB118 is above the OSPAR derived EAC at 22 out of 29 sampled stations, with 15 showing significant reductions. Cadmium is increasing significantly at six stations with two sites in the North Sea breaching corresponding OSPAR EAC. Mean results for all other PCBs and metals stayed below the EAC thresholds, with Hg concentrations even falling below BAC levels at South Eddystone located in the western English Channel. This study shows that PCBs banned over 20years ago are still found at concentrations in fish liver tissues which may pose a health risk to both the individual fish and their predators.

PCB pollution continues to impact populations of orcas and other dolphins in European waters.

Organochlorine (OC) pesticides and the more persistent polychlorinated biphenyls (PCBs) have well-established dose-dependent toxicities to birds, fish and mammals in experimental studies, but the actual impact of OC pollutants on European marine top predators remains unknown. Here we show that several cetacean species have very high mean blubber PCB concentrations likely to cause population declines and suppress population recovery. In a large pan-European meta-analysis of stranded (n = 929) or biopsied (n = 152) cetaceans, three out of four species:- striped dolphins (SDs), bottlenose dolphins (BNDs) and killer whales (KWs) had mean PCB levels that markedly exceeded all known marine mammal PCB toxicity thresholds. Some locations (e.g. western Mediterranean Sea, south-west Iberian Peninsula) are global PCB "hotspots" for marine mammals. Blubber PCB concentrations initially declined following a mid-1980s EU ban, but have since stabilised in UK harbour porpoises and SDs in the western Mediterranean Sea. Some small or declining populations of BNDs and KWs in the NE Atlantic were associated with low recruitment, consistent with PCB-induced reproductive toxicity. Despite regulations and mitigation measures to reduce PCB pollution, their biomagnification in marine food webs continues to cause severe impacts among cetacean top predators in European seas.

Hexabromocyclododecanes, polybrominated diphenyl ethers, and polychlorinated biphenyls in radiometrically dated sediment cores from English lakes, ~1950-present.

This paper reports input fluxes between ~1950 and present, of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecanes (HBCDs) in radiometrically-dated sediment cores from 7 English lakes. Fluxes of PCBs at all but one location prone to significant sediment resuspension peaked in the late-1960s/early-1990s, before declining thereafter. Input fluxes of HBCDs at all sites increased from first emergence in the mid-1960s. Thereafter, fluxes peaked in the late-1980s/early-2000s, before declining through to the present, except at the most urban site where HBCD fluxes are still increasing. Trends of PBDEs predominant in the Penta-BDE and Octa-BDE formulations vary between sites. While at some locations, fluxes peaked in the late-1990s/early-2000s; at others, fluxes are still increasing. This suggests the full impact of EU restrictions on these formulations has yet to be felt. Fluxes of BDE-209 have yet to peak at all except one location, suggesting little discernible environmental response to recent EU restrictions on the Deca-BDE product. Strikingly, fluxes of BDE-209 in the most recent core slices either exceed or approach peak fluxes of ΣPCBs, implying substantial UK use of Deca-BDE. Excepting HBCDs, inventories of our target contaminants correlated significantly with local population density, implying substantial urban sources.

Reproductive Failure in UK Harbour Porpoises Phocoena phocoena: Legacy of Pollutant Exposure?

Reproductive failure in mammals due to exposure to polychlorinated biphenyls (PCBs) can occur either through endocrine disrupting effects or via immunosuppression and increased disease risk. To investigate further, full necropsies and determination of summed 25 polychlorinated biphenyls congeners (∑PCBs lipid weight) in blubber were undertaken on 329 UK-stranded female harbour porpoises (1990-2012). In sexually mature females, 25/127 (19.7%) showed direct evidence of reproductive failure (foetal death, aborting, dystocia or stillbirth). A further 21/127 (16.5%) had infections of the reproductive tract or tumours of reproductive tract tissues that could contribute to reproductive failure. Resting mature females (non-lactating or non-pregnant) had significantly higher mean ∑PCBs (18.5 mg/kg) than both lactating (7.5 mg/kg) and pregnant females (6 mg/kg), though not significantly different to sexually immature females (14.0 mg/kg). Using multinomial logistic regression models ΣPCBs was found to be a significant predictor of mature female reproductive status, adjusting for the effects of confounding variables. Resting females were more likely to have a higher PCB burden. Health status (proxied by "trauma" or "infectious disease" causes of death) was also a significant predictor, with lactating females (i.e. who successfully reproduced) more likely to be in good health status compared to other individuals. Based on contaminant profiles (>11 mg/kg lipid), at least 29/60 (48%) of resting females had not offloaded their pollutant burden via gestation and primarily lactation. Where data were available, these non-offloading females were previously gravid, which suggests foetal or newborn mortality. Furthermore, a lower pregnancy rate of 50% was estimated for "healthy" females that died of traumatic causes of death, compared to other populations. Whether or not PCBs are part of an underlying mechanism, we used individual PCB burdens to show further evidence of reproductive failure in the North-east Atlantic harbour porpoise population, results that should inform conservation management.

Fingerprint analysis of brominated flame retardants and Dechloranes in North Sea sediments.

53 brominated and chlorinated flame retardants were investigated in sediment samples from the German rivers Elbe and Weser, the German Bight, Jadebusen, East Frisian Coast as well as the UK East coast. The aim of the presented study was to investigate the prevalence of different halogenated flame retardant groups as contaminants in North Sea sediments, identify determining factors for the distribution and levels as well as to identify area specific fingerprints that could help identify sources. In order to do that a fast and effective ASE extraction method with an on-line clean-up was developed as well as a GC-EI-MSMS and LC-ESI-MSMS method to analyse PBDEs, MeOBDEs, alternate BFRs, Dechloranes as well as TBBPA and HBCDD. A fingerprinting method was adopted to identify representative area-specific patterns based on detection frequency as well as concentrations of individual compounds. Concentrations in general were low, with<1 ng g(-1) dw for most compounds. Exceptions were the comparably high concentrations of BDE-209 with up to 7 ng g(-1) dw in selected samples and TBBPA in UK samples with 2.7±1.5 ng g(-1) dw. Apart from BDE-209 and TBBPA, alternate BFRs and Dechloranes were predominant in all analysed samples, displaying the increasing relevance of these compounds as environmental contaminants.

Organophosphorus flame retardants (PFRs) and plasticisers in harbour porpoises (Phocoena phocoena) stranded or bycaught in the UK during 2012.

A suite of twenty organophosphorus flame retardant compounds have been determined in blubber and liver tissue of twenty harbour porpoises stranded or bycaught in the UK during 2012 in order to establish current levels of contamination. Fourteen of the twenty compounds were below the limits of quantification in all samples. Six could be quantified at maximum concentrations (in blubber) between 6.7 and 246µgkg(-1) wet weight. These levels do not suggest a high level of concern regarding potential impacts and do not indicate that routine monitoring in UK porpoises is warranted at this time.

Organohalogen contaminants and trace metals in North-East Atlantic porbeagle shark (Lamna nasus).

The North-East Atlantic porbeagle (Lamna nasus) population has declined dramatically over the last few decades and is currently classified as 'Critically Endangered'. As long-lived, apex predators, they may be vulnerable to bioaccumulation of contaminants. In this study organohalogen compounds and trace elements were analysed in 12 specimens caught as incidental bycatch in commercial gillnet fisheries in the Celtic Sea in 2011. Levels of organohalogen contaminants were low or undetectable (summed CB and BDE concentrations 0.04-0.85 mg kg(-1)wet weight). A notably high Cd concentration (7.2 mg kg(-1)wet weight) was observed in one mature male, whereas the range observed in the other samples was much lower (0.04-0.26 mg kg(-1)wet weight). Hg and Pb concentrations were detected only in single animals, at 0.34 and 0.08 mg kg(-1)wet weight, respectively. These contaminant levels were low in comparison to other published studies for shark species.

Alternative flame retardants, Dechlorane Plus and BDEs in the blubber of harbour porpoises (Phocoena phocoena) stranded or bycaught in the UK during 2008.

Thirty alternative flame retardant compounds and a suite of 17 brominated diphenyl ether (BDE) congeners were determined in the blubber of 21 harbour porpoises stranded or bycaught around UK coasts during 2008 using GC-MS/MS. Of the 30 compounds, 19 were not detected. Of the remaining 11 compounds, some fell below the lowest calibration level and so were recorded as less than values, but were certainly present in the blubber samples (examples include tetrabromo-p-xylene (TBX), tetrabromo-o-chlorotoluene (TBCT) and 2,3-dibromopropyl-2,4,6-tribromophenyl ether (TBP-DBPE). Concentrations were low, the highest concentration being only 35µgkg(-1) wet weight. This contrasted with those of the BDEs, summed concentrations which ranged from 54.6 to 913µgkg(-1) wet weight, although levels in porpoise blubber have been declining since 1998. Both Dechlorane Plus (DDC-CO) isomers were detected in some samples, suggesting either that this product has been used in the UK or that its presence may result from atmospheric transport from source regions. BDE183, a marker for the octa-mix PBDE product, was found at low concentrations (0.63 to 1.7µgkg(-1) wet weight) and the four nona- and deca-BDE congeners were not detected in any sample.