Levels of mercury, arsenic, cadmium and lead in Northeast Atlantic mackerel (Scomber scombrus) from northern European waters

Fillets from a total of 1245 Northeast Atlantic mackerel (Scomber scombrus) sampled in different fishing areas of the Northeast Atlantic during 2007-2016 were analysed for mercury, cadmium, arsenic and lead using ICPMS. Mercury levels varied from <0.01 to 0.36 mg/kg wet weight (ww) with a total mean of 0.046 mg/kg ww and were significantly higher in Skagerrak than in the North Sea, the Norwegian Sea and west of Scotland. Cadmium concentrations varied from <0.002 to 0.16 mg/kg ww with a mean value of 0.015 mg/kg ww. Only 0.24 % and 0.16 % of the sampled fish exceeded the EU's maximum levels for cadmium and mercury, respectively. Arsenic levels varied between 0.43 and 6.9 mg/kg ww with a mean value of 2.2 mg/kg ww and showed seasonal variation following variations in fat content. Lead concentrations were low and below the analytical limit of quantification (LOQ) in 97 % of the samples.

Climate change dynamics and mercury temporal trends in Northeast Arctic cod (Gadus morhua) from the Barents Sea ecosystem

The Northeast Arctic cod (Gadus morhua) is the world's northernmost stock of Atlantic cod and is of considerable ecological and economic importance. Northeast Arctic cod are widely distributed in the Barents Sea, an environment that supports a high degree of ecosystem resiliency and food web complexity. Here using 121 years of ocean temperature data (1900-2020), 41 years of sea ice extent information (1979-2020) and 27 years of total mercury (Hg) fillet concentration data (1994-2021, n = 1999, ≥71% Methyl Hg, n = 20) from the Barents Sea ecosystem, we evaluate the effects of climate change dynamics on Hg temporal trends in Northeast Arctic cod. We observed low and consistently stable, Hg concentrations (yearly, least-square means range = 0.022-0.037 mg/kg wet wt.) in length-normalized fish, with a slight decline in the most recent sampling periods despite a significant increase in Barents Sea temperature, and a sharp decline in regional sea ice extent. Overall, our data suggest that recent Arctic amplification of ocean temperature, "Atlantification," and other perturbations of the Barents Sea ecosystem, along with rapidly declining sea ice extent over the last ∼30 years did not translate into major increases or decreases in Hg bioaccumulation in Northeast Arctic cod. Our findings are consistent with similar long-term, temporal assessments of Atlantic cod inhabiting Oslofjord, Norway, and with recent investigations and empirical data for other marine apex predators. This demonstrates that Hg bioaccumulation is highly context specific, and some species may not be as sensitive to current climate change-contaminant interactions as currently thought. Fish Hg bioaccumulation-climate change relationships are highly complex and not uniform, and our data suggest that Hg temporal trends in marine apex predators can vary considerably within and among species, and geographically. Hg bioaccumulation regimes in biota are highly nuanced and likely driven by a suite of other factors such as local diets, sources of Hg, bioenergetics, toxicokinetic processing, and growth and metabolic rates of individuals and taxa, and inputs from anthropogenic activities at varying spatiotemporal scales. Collectively, these findings have important policy implications for global food security, the Minamata Convention on Mercury, and several relevant UN Sustainable Development Goals.

Congener-specific accumulation of persistent organic pollutants in marine fish from the Northeast Atlantic Ocean

Bioaccumulation of persistent organic pollutants (POPs) in marine fish may pose a health risk to human consumers. Using data from ∼8400 individuals of 15 fish species collected in the North-East Atlantic Ocean (NEAO), we assessed concentrations of individual POP congeners, including dioxins, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). POPs analyses were performed with accredited methods using high-resolution gas chromatography/high-resolution mass spectrometry, gas chromatography/tandem mass spectrometry (GC-MS/MS) and GC/MS. The results showed that POPs congener composition profiles were more influenced by fish species than by geography. However, due to long range transport from emissions at lower latitudes, lighter congeners made a larger contribution to the total POPs concentrations in the northernmost areas compared to southern regions. A model was developed to elucidate the relative effects of several factors on POPs concentrations and showed that variation among and within fish species was associated with fat content, fish size, trophic position, and latitude. For the first time, POPs concentrations were shown to increase nonlinearly with fat content, reaching an asymptotic plateau when fat content was > 10%. This study explored detailed POP congener profiles and the factors associated with POPs accumulation in commercially relevant fish harvested from the NEAO.

Sampling of Atlantic salmon using the Norwegian Quality cut (NQC) vs. Whole fillet; differences in contaminant and nutrient contents

Risk- benefit assessments of seafood require high-quality food composition data. In accordance with EU regulations, Atlantic salmon (Salmo salar) has conventionally been sampled using the Norwegian Quality Cut (NQC), a sub-cut of the middle section of the fish, in Norwegian surveillance programs. By comparing the contents of nutrients and contaminants in 34 samples of farmed Atlantic salmon, we aimed to evaluate the representativeness of the NQC compared with the whole fillet. Of the 129 analytes evaluated, eight single analytes, in addition to 25 different fatty acids, showed significant differences between the cuts. Significant differences were evident for total fat, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and sum PCB-6, but not for the sum of dioxins and dioxin-like PCBs. We further suggest that the NQC may still be used in large-scale sampling of Atlantic salmon, and that the whole fillet would be preferable when analysing the content of nutrients.

Temperature Dependent Depuration of Norovirus GII and Tulane Virus from Oysters (Crassostrea gigas)

Raw oysters are considered a culinary delicacy but are frequently the culprit in food-borne norovirus (NoV) infections. As commercial depuration procedures are currently unable to efficiently eliminate NoV from oysters, an optimisation of the process should be considered. This study addresses the ability of elevated water temperatures to enhance the elimination of NoV and Tulane virus (TuV) from Pacific oysters (Crassostrea gigas). Both viruses were experimentally bioaccumulated in oysters, which were thereafter depurated at 12 °C and 17 °C for 4 weeks. Infectious TuV and viral RNA were monitored weekly for 28 days by TCID₅₀ and (PMAxx-) RT-qPCR, respectively. TuV RNA was more persistent than NoV and decreased by < 0.5 log₁₀ after 14 days, while NoV reductions were already > 1.0 log₁₀ at this time. For RT-qPCR there was no detectable benefit of elevated water temperatures or PMAxx for either virus (p > 0.05). TuV TCID₅₀ decreased steadily, and reductions were significantly different between the two temperatures (p < 0.001). This was most evident on days 14 and 21 when reductions at 17 °C were 1.3-1.7 log₁₀ higher than at 12 °C. After 3 weeks, reductions > 3.0 log₁₀ were observed at 17 °C, while at 12 °C reductions did not exceed 1.9 log₁₀. The length of depuration also had an influence on virus numbers. TuV reductions increased from < 1.0 log₁₀ after seven days to > 4.0 log₁₀ after 4 weeks. This implies that an extension of the depuration period to more than seven days, possibly in combination with elevated water temperatures, may be beneficial for the inactivation and removal of viral pathogens.

Iodine Bioavailability and Accumulation of Arsenic and Cadmium in Rats Fed Sugar Kelp (Saccharina latissima)

Suboptimal iodine status is a prominent public health issue in several European coun-tries. Brown algae have a high iodine content that, upon intake, may exceed the recommended dietary intake level, but iodine bioavailability has been reported to be lower than from potassium iodide (KI) and highly depends on algae species. Further, potential negative effects from other components in algae, such as cadmium (Cd) and arsenic (As), have also been addressed. In this study, we observed a lower bioavailability of iodine from farmed sugar kelp (Saccharina latissima) than from KI in female Wistar IGS rats. Urinary iodine excretion was 94-95% in rats fed KI and 73-81% in rats fed sugar kelp, followed by increased faecal iodine levels in rats fed sugar kelp. No effects on body weight, feed efficiency, or plasma markers for liver or kidney damage were detected. The highest dose of iodine reduced plasma free thyroxine (fT4) and total T4 levels, but no significant effects on circulating levels of thyroid-stimulating hormone (TSH) and free triiodo-thyronine (fT3) were detected. Faeces and urine measurements indicate that 60-80% of total As and 93% of Cd ingested were excreted in rats fed 0.5 and 5% kelp. Liver metabolomic profiling demonstrates that a high inclusion of sugar kelp in the diet for 13 weeks of feeding modulates metabolites with potential antioxidant activity and phytosterols.

Rapid temporal decline of mercury in Greenland halibut (Reinhardtius hippoglossoides)

Mercury (Hg) pollution in the ocean is an issue of global concern, however bioaccumulation regimes of this ubiquitous pollutant in marine apex predators have important knowledge gaps. Our fish length and stable isotope (δ¹⁵N and δ¹³C) normalized data of Greenland halibut (GH) (Reinhardtius hippoglossoides) showed that Hg bioaccumulation in fillet tissue decreased by ~35-50 %, over a ten-year period from 2006 to 2015 (n = 7 individual sampling years). Hg was predominantly in the methylmercury form (>77 %). Results from a Bayesian information theoretic model showed that GH Hg concentrations decreased with time and its associated declines in Hg air emissions, estimated trophic position, and a potentially lower degree of demersal prey use as indicated by temporal trend shifts in nitrogen (δ¹⁵N) and carbon (δ¹³C) stable isotope values. GH trophic shifts accounted for about one third of the observed temporal reduction in Hg. Our study demonstrates the importance of simultaneously considering Hg emissions, food web dynamics and trophic shifts as important drivers of Hg bioaccumulation in a marine, deep water fish species and highlights the effectiveness of Hg regulations on ocean apex predator Hg concentrations and overall seafood safety.

Levels of omega 3 fatty acids, vitamin D, dioxins and dioxin-like PCBs in oily fish; a new perspective on the reporting of nutrient and contaminant data for risk-benefit assessments of oily seafood

Oily seafood is an important food source which contains several key nutrients beneficial for human health. On the other hand, oily seafood also contains persistent organic pollutants (POPs), including the dioxin-like compounds (DLCs) polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and dioxin-like-polychlorinated biphenyls (dl-PCBs), potentially detrimental to human health. For a comprehensive comparison of the beneficial and potentially adverse health effects of seafood consumption, risk-benefit analyses are necessary. Risk-benefit analyses require reliable quantitative data and sound knowledge of uncertainties and potential biases. Our dataset comprised more than 4000 analyses of DLCs and more than 1000 analyses each of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and vitamin D in the three most important Norwegian commercial oily seafood species: Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus) and farmed Atlantic salmon (Salmo salar). The levels of several DLC congeners were below the limit of quantification (LOQ), making estimation of true levels challenging. We demonstrate that the use of upper bound substitution of censored data will overestimate, while lower bound substitution will underestimate the actual levels of DLCs. Therefore, we implement an alternative robust statistical method by combining Maximum Likelihood Estimation, Regression on Order Statistics and Kaplan-Meier analyses, which is better suited for providing estimations of levels of these contaminants in seafood. Moreover, we illustrate the impact of the toxic equivalency factor (TEF) system on estimation of the sums of DLCs by comparing the TEF system to an alternative system of relative effect potency (REP) factors (Consensus Toxicity Factors). The levels of nutrients and contaminants were related to adequate intake (AI) and tolerable weekly intake (TWI), respectively. We used AI and the TWI values established by the European Food Safety Authority (EFSA). The benefit and the risk were further viewed in the context of the Norwegian average intake of oily fish, and the Norwegian governmental official dietary recommendations of oily fish. Our results showed that both benefit and risk are met at the levels found of nutrients and DLCs in oily seafood. The comprehensive quantitative data presented here will be a key for future risk-benefit assessment of oily fish consumption. Together, our results underline that a refined formalized integrative risk-benefit assessment of oily fish in the diet is warranted, and that the data and methodology presented in this study are highly relevant for future integrated and multidisciplinary assessment of both risks and benefits of seafood consumption for human health.

Iodine and Mercury Content in Raw, Boiled, Pan-Fried, and Oven-Baked Atlantic Cod (Gadus morhua)

There is a lack of scientific evidence regarding the stability of iodine and mercury during cooking and processing of seafood. In this study, the iodine and mercury content were determined after thawing frozen fillets of Atlantic cod (Cadus morhua), and further in raw compared to boiled, pan-fried, and oven baked fillets. Iodine was determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and mercury by atomic absorption spectrophotometry with Direct Mercury Analyzer (DMA-80). Thawing of the cod resulted on average in a 12% loss of iodine to the thawing water. Boiling significantly decreased the total content of iodine per slice of cod fillet corresponding to the concentration of iodine found in the boiling water. Pan-frying and oven-baking did not cause any significant changes of the total iodine content per slice of cod fillet, although iodine content per 100 g increased due to weight reduction of the cod slices from evaporation of water during preparation. For mercury, we found minimal changes of the different cooking methods. In summary, the findings in our study show that boiling had the greatest effect on the iodine content in the cod fillets. Type of cooking method should be specified in food composition databases as this in turn may influence estimation of iodine intake.

Undesirables in Mesopelagic Species and Implications for Food and Feed Safety-Insights from Norwegian Fjords

The increase in the global population demands more biomass from the ocean as future food and feed, and the mesopelagic species might contribute significantly. In the present study, we evaluated the food and feed safety of six of the most abundant mesopelagic species in Norwegian fjords. Trace elements (i.e., arsenic, cadmium, mercury, and lead), organic pollutants (i.e., dioxins, furans, dioxin-like polychlorinated biphenyls, and polybrominated flame-retardants), and potentially problematic lipid compounds (i.e., wax esters and erucic acid) were analyzed and compared to existing food and feed maximum levels and intake recommendations. Furthermore, contaminant loads in processed mesopelagic biomass (protein, oil, and fish meal) was estimated using worst-case scenarios to identify possible food and feed safety issues. While most undesirables were low considering European food legislation, we identified a few potential food safety issues regarding high levels of fluoride in Northern krill, wax esters in glacier lanternfish, and long-chain monounsaturated fatty acids in silvery lightfish. Our estimates in processed biomass indicated high levels of undesirable trace elements in the protein fraction, frequently exceeding the maximum levels for feed ingredients. However, in fish meal, almost no exceedances were seen. In the oil fraction, dioxins and furans were above the maximum levels, given for food and feed ingredients. The present study is crucial to enable an evaluation of the value of these species; however, more data is needed before proceeding with large-scale harvesting of mesopelagic biomass.

Cadmium in brown crab Cancer pagurus. Effects of location, season, cooking and multiple physiological factors and consequences for food safety

Brown crab Cancer pagurus is appreciated as seafood in several European countries. However, cadmium levels in crabs can be elevated and their consumption may pose a hazard for human health. To assess if cadmium poses a threat to food safety in Norway, crabs were sampled at two different locations along the Norwegian coast: one in the South of Norway and one in the North of Norway. Cadmium levels were determined in different tissues (claw meat, hepatopancreas and inner meat). To highlight specific risk factors for cadmium, the concentration of cadmium was related to different exogenous (location, cooking and season) and physiological (size, sex, moulting stage, gonad maturation stage, condition) factors. The results confirmed previous findings of much higher cadmium levels in brown crab sampled in the North of Norway compared to the South. Cooking of crabs further led to higher concentrations in claw meat. The effect of season on cadmium levels was different in the North and South and no clear patterns could be identified, probably due to a high inter-individual variation in cadmium levels. Size showed a correlation with the total amount of cadmium for crabs in the North indicating an accumulation of cadmium over time; together with a slower growth, this may lead to the higher cadmium levels, observed in the crabs from Northern Norway. The risk connected to cadmium exposure when consuming brown crab mainly depends on the consumption pattern, the parts of the crab consumed and the origin of the crab. Regardless of origin, the consumption of claw meat does not display a consumer health risk. However, the consumption of meals consisting of inner meat only and inner meat of brown crab from Northern Norway may pose a health risk.

Effects of geography and species variation on selenium and mercury molar ratios in Northeast Atlantic marine fish communities

Methylmercury (MeHg) is a potent neurotoxin that bioaccumulates in seafood. Co-occurrence of selenium (Se) may affect the bioavailability and toxicity of MeHg in organisms. Here we report the concentrations of total mercury (Hg) and Se in 17 teleost fish species (n = 8459) sampled during 2006-2015 from the North East Atlantic Ocean (NEAO) and evaluate species variation and effects of geography. Mean Hg concentration ranged from 0.04 mg kg^-1 ww in Atlantic mackerel (Scomber scombrus) and blue whiting (Micromesistius poutassou) to 0.72 mg kg^-1 ww in blue ling (Molva dypterygia). Se concentrations were less variable and ranged from 0.27 mg kg^-1 ww in Atlantic cod (Gadus morhua) to 0.56 mg kg^-1 ww in redfish (Sebastes spp.). The mean Se:Hg molar ratio ranged from 1.9 in blue ling to 43.3 in mackerel. Pelagic species had the lowest Hg concentrations and the highest Se:Hg ratios, whereas demersal species had the highest Hg concentrations and the lowest Se:Hg ratios. Se and Hg concentrations were positively correlated in 13 of the 17 species. Hg concentrations increased from the North to South in contrast to the Se:Hg molar ratio which exhibited the opposite trend. Fish from fjord and coastal areas had higher concentrations of Hg and lower Se:Hg molar ratios compared to fish sampled offshore. All species had average Se:Hg molar ratios >1 and Hg concentrations were largely below the EU maximum level of 0.5 mg kg^-1 ww with few exceptions including the deep water species tusk (Brosme brosme) and blue ling sampled from fjord and coastal habitats. Our results show that two fillet servings of tusk, blue ling or Atlantic halibut (Hippoglossus hippoglossus) exceeded the tolerable weekly intake of MeHg although the surplus Se may possibly ameliorate the toxic effects of MeHg. However, some individuals with selenium deficiencies may exhibit greater sensitivity to MeHg.

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.

Tracing simultaneous cadmium accumulation from different uptake routes in brown crab Cancer pagurus by the use of stable isotopes

High concentrations of cadmium in brown crab are an issue of food safety, and large variations between different areas have been found. To investigate the relative importance of dietary and aqueous uptake regarding the overall accumulation in brown crab, we used stable isotopes to trace the uptake from both routes simultaneously in the same animals. We demonstrated that the analytical challenges regarding background concentrations of natural isotope distribution and polyatomic interferences in the different matrices can be overcome with an appropriate analytical setup and modern mathematical corrections using a computer software. Cadmium was accumulated via both routes and was found in all measured organs at the end of the exposure phase. The obtained data were used to establish accumulation curves for both uptake routes and estimate accumulation parameters for hepatopancreas, as the most important organ in crab regarding total cadmium body burden. Using the estimated parameters in combination with naturally relevant cadmium concentrations in seawater and diet in a model, allowed us to predict the relative importance of the aqueous and dietary uptake route to the total hepatopancreas burden. According to the prediction, the dietary route is the main route of uptake in brown crab with a minimum of 98% of the accumulated cadmium in hepatopancreas originating from diet. Future studies addressing the source and accumulation of cadmium in crab should therefore focus on the uptake from feed and factors connected to foraging.

Cadmium in the shore crab Carcinus maenas along the Norwegian coast: geographical and seasonal variation and correlation to physiological parameters

Previously, high concentrations of cadmium have been found in the hepatopancreas of the edible or brown crab (Cancer pagurus) sampled from positions north of about 67° N, compared to regions further south along the Norwegian coast, with no clear understanding why. In order to study a similar organism in the same ecosystem, the present study analyzed 210 shore crabs (Carcinus maenas) from four different locations along the Norwegian coast, two in the North and two in the South. The physiological variables size, sex, molting stage, hepatosomatic index, carapace color, and gonad maturation were registered, in attempt to explain the high inter-individual variation in cadmium levels in hepatopancreas. In contrast to the brown crabs, the shore crabs showed no clear geographical differences in cadmium concentrations. This indicates physiological differences between the two crab species. No clear and consistent correlations were found between cadmium levels and physiological parameters, except for sex, where cadmium concentration in hepatopancreas was twice as high in males compared to females. The cadmium levels also varied with season, with approximately 40 and 60% lower cadmium concentration in April than August for male and female shore crabs, respectively. None of the analyzed cadmium concentrations in muscle meat from claws exceeded EUs food safety limit, and low cadmium levels in soup prepared from shore crabs clearly indicated that this dish is not problematic regarding food safety.

An Outbreak of Norovirus Infection from Shellfish Soup Due to Unforeseen Insufficient Heating During Preparation

Norovirus causes large outbreaks involving all age groups and are considered the most common cause of infectious foodborne diseases worldwide. The aim of this study was to describe a norovirus outbreak connected to insufficient heat treatment during preparation of a shellfish soup in serving portions, during a company Christmas celebration in Norway, December 2013. A questionnaire sent to the employees, showed that 67 % (n = 43) of the celebration participants, reported gastrointestinal symptoms including stomach pain, vomiting, diarrhoea and light fever in the period between 24 and 48 h post celebration. Several dishes were served, including shellfish soup made with carpet shell clams (Tapes rhomboides) in porcelain cups. Consuming this soup, was the only significant risk factor for infection. Norovirus GI and GII were detected in the remaining raw shellfish. To mimic the time and temperature obtained during bivalve soup preparation, raw chopped shellfish tissue and raw cepa onion were added in porcelain cups tempered to 20 °C. To each of these cups, boiling soup base was added. The temperature in the shellfish tissue was continuously recorded, and showed a maximum of 49 °C in the period between 3 and 7 min after adding the boiling soup base. After 1 h the temperature was 30 °C. This time and temperature combination was obviously not sufficient for inactivation of norovirus present in the shellfish tissue. In conclusion, the heat-absorbing capacity of cold ingredients, utensils and table wear porcelain should not be underestimated during food production. Consumers who want to avoid eating raw shellfish, should not assume that the shellfish tissue in preparation as described in our study is adequately heat treated.

A baseline study of metals in herring (Clupea harengus) from the Norwegian Sea, with focus on mercury, cadmium, arsenic and lead

The Norwegian spring spawning (NSS) herring is an ecologically and economically important fish population in the Norwegian Sea. It was the first of several Norwegian fish stocks subject to a baseline study designed to give a comprehensive account of the levels of contaminants in a fish species from most of its area of distribution and during different seasons. During 2006 and 2007, 800 individual herring were sampled in their feeding areas in the Norwegian Sea in spring and autumn and at their spawning grounds off the coast of Norway during late winter. Metals including Hg, Cd, As and Pb were determined in muscle samples of individual herring, and mean concentrations±sd (mg kg(-1) ww) were: Hg: 0.04±0.03, Cd: 0.010±0.006, As: 2.2±0.6 and Pb: <0.01-0.10. Apart from one sample, no individual herring exceeded the EU's maximum level for any of these elements, as has been seen also in previous monitoring. Hg and Cd concentration increased with increasing fish age and As concentration varied seasonally, possibly due to uptake during feeding (summer), elimination during starvation (winter) and up-concentration during spawning (spring).

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.

A baseline study on levels of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, non-ortho and mono-ortho PCBs, non-dioxin-like PCBs and polybrominated diphenyl ethers in Northeast Arctic cod (Gadus morhua) from different parts of the Barents Sea

This study is one of several baseline studies on commercially important Norwegian wild fish species that will provide information concerning metals and persistent organic pollutants (POPs) and food safety. The cod liver is a traditional food product in Norway and a potential source for POPs in the diet. The concentrations of dioxins and furans (PCDD/Fs), dioxin-like PCBs (DL-PCBs), non-dioxin-like PCBs (NDL-PCBs, PCB6) and polybrominated flame retardants (PBDEs) were determined in the liver of 784 individual Northeast Arctic cod caught at 32 positions in the Barents Sea in the period from 2009-2010. In addition, muscle samples from 30 individual cod were analysed for the same substances. The mean concentration of the sum of PCDD/Fs and DL-PCBs for all samples was 14.2 ng TEQ who-2005/kg ww with a variation between 1.0 and 151 ng TEQ/kg ww. The concentrations of POPs in the fillet samples were very low.

A baseline study of metals in cod (Gadus morhua) from the North Sea and coastal Norwegian waters, with focus on mercury, arsenic, cadmium and lead

This study is one of several baseline studies that will provide basic and reliable information about the content of undesirable substances in important species of fish caught in Norwegian waters. Concentrations of metals in the muscle and livers of 516 cod caught at 22 positions in the North Sea were analysed. An additional 687 cod were caught from 13 fjords and coastal areas along the coast of Norway. Three out of 1203 samples of muscle exceeded the maximum limit of 0.5 mg Hg kg(-1) wet weight set by the EU for foodstuffs. The mercury concentration in cod muscle was higher and the cadmium concentration in the liver was lower in the North Sea and coastal areas in the southern part of Norway than in the Barents Sea and coastal areas in the northern part of Norway. These differences are perhaps caused by differences in the cod diet.

A baseline study of levels of mercury, arsenic, cadmium and lead in Northeast Arctic cod (Gadus morhua) from different parts of the Barents Sea

This study is one of several baseline studies that will provide basic and reliable information about the content of undesirable substances in important species of fish caught in Norwegian waters. Concentrations of metals in the muscle and liver of more than 800 Northeast Arctic cod caught at 32 sites in the Barents Sea are reported. The highest concentration of both mercury in the muscle and cadmium in the liver was found in cod caught in the western part of the Barents Sea, while the highest concentration of total arsenic was found in cod from the eastern part. The arsenic concentrations varied greatly among individual fish, ranging from 0.3 to 170 mg kg(-1) wet weight in the muscle. Such high levels of total arsenic have never previously been reported in any fish, and the primary factor for these high concentrations is likely to be the shrimp in the cod diet.

Organ distribution and food safety aspects of cadmium and lead in great scallops, Pecten maximus L., and Horse Mussels, Modiolus modiolus L., from Norwegian waters

The purpose of the study was to determine the levels and organ distribution of the potentially harmful inorganic elements cadmium and lead in great scallops and horse mussels from unpolluted Norwegian waters. The scallops far exceeded the EU-limit for cadmium in bivalves when all soft tissues were analysed. When only muscle and gonad were included, however, the level of cadmium was acceptable, because cadmium accumulated in the digestive gland with a mean of 52 mg/kg ww (wet weight). In horse mussel, lead was the most problematic element and the concentration varied from 1.4 to 6.6 mg/kg ww with a mean of 3.7 mg/kg ww, exceeding the EU limit of 1.5 mg Pb/kg. The highest concentration of lead was found in the kidney with an average of 120 mg/kg ww and with a maximum value of 240 mg/kg ww. The kidney tissue accounted for approximately 94% of the lead burden in the horse mussel. In order to consume these bivalves, only muscle and gonad of great scallops should be used for consumption and the kidney of horse mussel should be removed prior to consumption.