Quick and efficient microplastic isolation from fatty fish tissues by surfactant-enhanced alkaline digestion.

For monitoring microplastic contamination in fish tissues, tissue digestion into filterable components prior to microplastic identification and quantification should be quick and efficient, providing satisfying microplastic recoveries of relevant particle sizes. Filtration with a small pore size, necessary to target small particles, is a challenge. Some proposed protocols take several days. To improve this, a combination of surfactants (Tween®-20 and Triton™ X-100) with potassium hydroxide (KOH) and pH neutralization was used. Fish bones were removed in tissue preparation prior to digestion. Recovery down to ca. 60-80 µm worked well for PA-66, PE, PET, PP, PS and PVC. In conclusion, we developed a comparatively swift digestion protocol, enabling filtration of 100 g samples with a pore size of 10 µm, for fish fillets with high (mackerel), intermediate (salmon, plaice) and low (cod) fat contents, fish liver, head kidney and oil samples, within 16-24 h.

Co-occurrence of contaminants in marine fish from the North East Atlantic Ocean: Implications for human risk assessment.

Marine fish from the North East Atlantic Ocean (NEAO) are nutrient rich and considered a valuable economic resource. However, marine fish are also a major dietary source of several contaminants, including persistent organic pollutants (POPs) and heavy metals. Using one of the world's largest seafood datasets (n > 25,000 individuals), comprising 12 commercially important fish species collected during 2006-2019 in the NEAO, we assessed the co-occurrence of elements and POPs, and evaluated potential risks to human consumers. Several positive correlations between concentrations of mercury (Hg), dioxins, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were observed. Concentrations of Hg, dioxins, PCBs and PBDEs increased from North to South and associations between marine sediment contamination, sea temperature, and fish Hg and POPs concentrations were identified using multi-linear regression (MLR) models. In general, Hg concentrations in fillet and liver of fish were positively associated with increases in both sediment contamination and sea temperature. POPs concentrations in both fillet and liver were positively associated with increases in sediment contamination, and only POPs concentrations in the liver of benthopelagic and demersal species were found to be positively correlated with sea temperature. Using a probabilistic approach to estimate human contaminant exposure from seafood, we showed that intake of pelagic species posed the highest risk of dioxins and dioxin-like PCBs (DL-PCBs) exposure, while intake of benthopelagic and demersal species posed the highest risk of Hg exposure. This study can serve as a model to further understand the distribution, co-occurrence, and trends of contaminants in seafood harvested from the NEAO and their potential risks to human consumers.

Congener patterns of polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls as a useful aid to source identification during a contamination incident in the food chain.

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) are still considered among the most important groups of contaminants in the food chain. Self-control by food producers and official control by authorities are important activities that allow contaminant sources to be traced and promote further reduction in food and feed levels. Strict but feasible maximum levels were set by the EU Commission for food and feed to support this strategy, as well as action levels and thresholds. When products exceed these levels, it is important to trace the source of contamination and take measures to remove it. Congener patterns of PCDD/Fs and PCBs differ between sources and are important tools for source identification. Therefore, patterns associated with different sources and incidents relating to various feed matrices and certain agricultural chemicals were collated from published scientific papers, with additional ones available from some laboratories. The collection was evaluated for completeness by presentations at workshops and conferences. Primary sources appear to derive from 5 categories, i) by-products from production of organochlorine chemicals (e.g. PCBs, chlorophenols, chlorinated pesticides, polyvinyl chloride (PVC)), ii) the result of combustion of certain materials and accidental fires, iii) the use of inorganic chlorine, iv) recycling/production of certain minerals, and v) certain naturally occurring clays (ball clay, kaolinite). A decision tree was developed to assist in the identification of the source.

Factors influencing risk assessments of brominated flame-retardants; evidence based on seafood from the North East Atlantic Ocean.

Brominated flame-retardants (BFRs) such as polybrominated diphenyl ethers (PBDE) and hexabromocyclododecane (HBCD) are considered hazardous to human health. Due to their persistence, they are still present in the environment and in biota and seafood is major contributor of BFRs to human exposure. Here, we used data from >9700 samples of wild and farmed fish, fish feed and fish feed ingredients collected from the North Atlantic between 2006 and 2016 aiming to investigate factors influencing the risk assessments of BFRs. Due to most representative number of analyses, PBDEs were the main focus of investigation. Mean ∑PBDE in fillet samples ranged from below quantification in Atlantic cod fillet to 2.0 µg kg-1 in Atlantic halibut. The main congener contributing to the ∑PBDE in all species was BDE 47. Factors affecting the level of BFR in seafood were multifaceted, and the levels were within species mainly determined by fish age, geographical origin and time of sampling. BDE 47, 99, 153 and HBCD were selected for margin of exposure (MOE) evaluation. When other sources of BFR than seafood were excluded, our risk assessment showed low risk at the current dietary intake of seafood. However, the dietary intake of BDE 99 may be of concern for toddlers when all sources are considered. The choice of fish species, dietary studies, choice of statistics, as well as exposure from other sources than seafood, were all factors that influenced the final MOE of BFRs. We propose the use of regression on order statistics as a tool for risk assessment, to illustrate means and spreads in large surveillance datasets to avoid the issue of measurements below the limit of quantification. A harmonized, updated evaluation of the risk associated with exposure to BFRs from diet, air and dust is warranted, where the fish species most commonly consumed also is taken into consideration.

Modelling scenarios on feed-to-fillet transfer of dioxins and dioxin-like PCBs in future feeds to farmed Atlantic salmon (Salmo salar).

The salmon feed composition has changed the last decade with a replacement of traditionally use of fish oil and fishmeal diets with vegetable ingredients and the use decontaminated fish oils, causing reduced concentrations of dioxins and dioxin-like PCBs in farmed Norwegian Atlantic salmon. The development of novel salmon feeds has prompted the need for prediction on dioxins and dl-PCB concentrations in future farmed salmon. Prediction on fillet dioxins and dl-PCB concentrations from different feed composition scenarios are made using a simple one-compartmental transfer model based on earlier established dioxin and dl-PCB congener specific uptake and elimination kinetics rates. The model is validated with two independent feeding trials, with a significant linear correlation (r(2) = 0.96, y = 1.0x, p < 0.0001, n = 116) between observed and predicted values. Model fillet predictions are made for the following four scenarios; (1) general feed composition of 1999, (2) feed composition of 2013, (3) future feed composition with high fish oil and meal replacement, (4) future feed composition with high fish oil and meal replacement and decontaminated fish oil. Model predictions of fillet dioxin and dl-PCB concentrations from 1999 (1.05 ng WHO2005-TEQs kg(-1)ww) and 2013 (0.57 ng WHO2005-TEQs kg(-1)ww) are in line with the data observed in national surveillance programs of those years (1.1 and 0.52 ng WHO2005-TEQs kg(-1)ww, respectively). Future use of high replacement and decontaminated oils feeds gave predicted fillet concentrations of 0.27 ng WHO2005-TEQs kg(-1)ww, which is near the limit of quantification.

Contaminant levels in Norwegian farmed Atlantic salmon (Salmo salar) in the 13-year period from 1999 to 2011.

BACKGROUND: Environmental pollutants such as dioxins and PCBs, heavy metals, and organochlorine pesticides are a global threat to food safety. In particular, the aquatic biota can bioaccumulate many of these contaminants potentially making seafood of concern for chronic exposure to humans. OBJECTIVES: The main objective was to evaluate trends of contaminant levels in Norwegian farmed Atlantic salmon in light of the derived tolerable intakes. METHODS: Through an EU-instigated surveillance programme, the Norwegian Food Safety Authority (NFSA) has between 1999 and 2011 collected more than 2300 samples of Norwegian farmed Atlantic salmon (Salmo salar) for contaminant analyses. The fillets of these fish were homogenised and analysed for dioxins, PCBs, heavy metals and organochlorine pesticides. RESULTS: The levels of the contaminants mercury, arsenic, dioxins, dioxin-like PCBs and DDT in Norwegian farmed salmon fillet have decreased during our period of analyses. The levels of cadmium, lead and several organochlorine pesticides were too close to the limit of quantification to calculate time trends. For PCB6 and quantifiable amounts of pesticides, except DDT, stable levels were observed. CONCLUSION: The contaminant levels in Norwegian farmed salmon have generally decreased between 1999 and 2011. Excluding other dietary sources, the levels of dioxins and dioxin-like PCBs in 2011 allowed consumption of up to 1.3kg salmon per week to reach the tolerable weekly intake. The group of contaminants which was the limiting factor for safe consumption of Norwegian farmed salmon, based on currently established TWI values, is the sum of dioxins and dioxin-like PCBs.

Simultaneous quantitative determination of the synthetic antioxidant ethoxyquin and its major metabolite in Atlantic salmon (Salmo salar, L), ethoxyquin dimer, by reversed-phase high-performance liquid chromatography with fluorescence detection.

A method for simultaneous quantitative determination of ethoxyquin (EQ) and its major metabolite in Atlantic salmon tissues, ethoxyquin dimer (EQ dimer), has been developed. The separation was achieved on tandem coupled phenyl-hexyl and C18 columns by 2-phase gradient elution with acetonitrile-ascorbic acid-acetic acid-diethyl amine organized in a 23.5 min sequence. Compounds were extracted with hexane from samples saponified in ethanol-NaOH and protected from air- and light-mediated oxidation by addition of saturated ethylenediaminetetraacetic acid, ascorbic acid, and pyrogallol. The identity of peaks was confirmed by spiking samples with standards verified by proton nuclear magnetic resonance spectrometry, mass spectrometry, and high-performance liquid chromatography. The detection limit (at 358/433 nm) of matrix-spiked EQ was 0.02 and 0.06 microg/L for EQ dimer, with 0.5 g sample weighed and resuspension in 0.5 mL hexane. Linearity was in the range of 0.2-175 microg/L for EQ and 0.3-5100 microg/L for EQ dimer. Two more ubiquitous compounds were identified as de-ethylated EQ and quinone imine. Totally, 14 peaks sharing spectral properties of EQ were separated in a single run, including a major peak present in all muscle samples, termed unknown metabolite of EQ (UMEQ). The concentrations of EQ, EQ dimer, and de-ethylated EQ, as well as concentrations of UMEQ (in arbitrary units), in the muscle were correlated to the amount of EQ fed to the salmon, thus indicating their possible metabolic origin. The pattern of 14 peaks in the muscle showed high specificity and could be used to discriminate between wild salmon and salmon fed EQ-supplemented feed. This method will be a useful tool for studying EQ metabolism and kinetics, and for the routine surveillance of residual levels of dietary EQ in farmed Atlantic salmon.

An automated extraction approach for isolation of 24 polyaromatic hydrocarbons (PAHs) from various marine matrixes.

An efficient and selective analytical method for determination and quantification of 24 various polyaromatic hydrocarbons (PAHs) in blue mussel (Mytilus edulis), salmon fillet (Salmo salar), fish oil and fish feed has been developed. The samples were extracted by means of accelerated solvent extraction (ASE) technique followed by a purification step with gel permeation chromatography (GPC). Identification and quantification were performed by using GC/MS. The novel combination of silica and alumina in the extraction step furnishes highly purified analytes for the most of the 24 PAHs investigated, and thus a fast and selective analytical method is developed. A small limitation with the method concerns the quantification of acenaphthene (Ace), fluorene (Fl), pyrene (Py) and benzo[a]anthracene (BaA), as the found values for these compounds do not match the certified values (SRM 2977, mussel tissue). Chrysene (Chr) and triphenylene (Tph) give unresolved peaks. The limits of detection (LOD) and limits of quantification (LOQ) found for benzo[a]pyrene (BaP) were 1.7 and 0.44 pg/g (LOD), and 5.8 and 1.5 pg/g (LOQ) for salmon fillet and blue mussel, respectively. This is in a very good accordance with respect to the European Community legislation for official control of BaP levels in foodstuff. The method may be used for qualitative identification of petroleum compounds in marine matrixes.