Concentration and distribution of 210Po in the tissues of the scallop Chlamys varia and the mussel Mytilus edulis from the coasts of Charente-Maritime (France)

Characteristics and radiological hazard assessment of 210Po in tilapia (Oreochromis niloticus) in Vietnam

210Po is one of the most toxic natural radionuclides. This isotope's characteristics and radiological hazard assessment have been concerned in different objects. In this study, the 210Po activities were determined in different tilapia organs/parts of 20 sample groups by alpha spectrometry. The 210Po activities in muscle, bone, intestine organs, and stomach contents unevenly distributed with a wide range from 0.5 ± 0.2 to 2.8 ± 0.4 and 1.4 ± 0.2 Bq·kg-1 wet.wt on average, from 0.6 ± 0.3 to 6.3 ± 0.7 and 3.5 ± 0.4 Bq·kg-1 wet.wt on average, from 46.3 ± 2.9 to 263 ± 9.7 and 115 ± 6 Bq·kg-1 wet.wt on average, and 20.9 ± 1.2 to 800 ± 29 and 197 ± 9 Bq·kg-1 wet.wt on average, respectively. The average 210Po activities in different parts of tilapia trend in order of CMuscle < CBone < CIntestine < CStomach contents. Insignificant correlations were observed between 210Po activities in tilapia organs with their total fish mass. The result could depend on feeding types, diet, different nutrient levels, metabolism, and excretion of 210Po in different ages. The concentration ratios (CRs) of tilapia muscle and bone organs were recorded with low values, while it was far greater than the CRs for the intestine organ. Annual committed effective doses contributing from 210Po concentration due to tilapia fish consumption were within the allowable limits for muscle and bone organs, while those values for intestine organs were far higher than the allowable limit value (assuming similar amount consumption of 30 kg·year-1 for each organ). The Erica tool was used to estimate the dose and risk to tilapia from 210Po exposure. Based on the calculated results, it can be seen that there was insignificant concern for tilapia due to ionizing radiation in the study area.

Radiological hazard assessment of 210Po in freshwater mussels (Sinanodonta jourdyi) and golden apple snail (Pomacea canaliculata) in Vietnam

210Po is a significant source of ionizing radiation that people are exposed to through food globally. This paper presents the wide range of accumulation level of 210Po in the organs of two species of shellfish including freshwater mussel (Sinanodonta jourdyi) and golden apple snail (Pomacea canaliculata), common freshwater species in Vietnam. There was a significant correlation between 210Po activity in muscle to their mass and size of freshwater mussels. In contrast, there was no relation between other organs of both species with their mass and size. The annual effective dose due to consumption of freshwater mussels ranged from 68.7 to 291 μSv year-1 with a mean value of 138 μSv year-1 for muscle and from 321 to 4560 μSv year-1 with a mean value of 1422 μSv year-1 for the hepatopancreas. Meanwhile, the AED for golden apple snail was recorded to be higher with values ranging from 105 to 2189 μSv year-1 with mean value of 673 μSv year-1 for muscle and from 468 to 4155 μSv year-1 with a mean value of 2332 μSv year-1 for hepatopancreas. Thus, the consumption of these two types of shellfish is considered relatively safe, but the hepatopancreas gland must be removed before processing.

Variation of 210-polonium in the cephalopod community from the Bay of Biscay, North-East Atlantic

Among natural radionuclides, 210Po is the major contributor to the radiation dose received by marine organisms. In cephalopods, 210Po is concentrated in the digestive gland, which contains over 90% of the whole-body burden of the nuclide. Although previous studies showed that 210Po was taken up independently of 210Pb, its parent nuclide, very little is known about the factors influencing its levels in cephalopods. To the best of our knowledge, no studies investigated 210Po levels in different species at the same time. In the present study, 210Po was analysed in the digestive gland of 62 individuals from 11 species representing a large range of feeding ecologies and habitats, including squids, cuttlefish and octopus species from coastal to deep-oceanic habitats. Among species, the highest activity was measured in Loligo vulgaris (5720 ± 3606 Bq/kg) and the lowest in T. megalops (188 Bq/kg). However, considering the habitats (benthic vs pelagic and neritic vs oceanic), no significant differences appeared. At the species level, no differences between sexes were found so both sexes were plotted together to test the size effect for species with at least 8 individuals (i.e., Eledone cirrhosa, L. vulgaris, L. forbesi and Sepia officinalis). In the first three species, 210Po levels decreased significantly with increasing size or weight but not in S. officinalis. In squid, this could be related to ontogenetic changes in diet from a high proportion of crustaceans (high Po content) in small individuals to fish (low Po content) in larger individuals, while the high dietary plasticity of S. officinalis at all stages of its life cycle could explain the lack of decrease in 210Po with size. In comparison to the few data from the literature, the levels of 210Po concentrations in the cephalopod community of the Bay of Biscay were overall in the same range than those reported in other cephalopods, varying across 4 orders of magnitude. Further studies are needed to understand the mechanism of retention in the cephalopod digestive gland.

A review of natural and anthropogenic radionuclide pollution in marine bivalves

Radionuclide contamination in food is a public health issue. Bivalves are known to accumulate relatively high levels of radionuclides. Despite many relevant reports, this information is poorly organized. Therefore, in this study, we conducted a comprehensive scientific review of radionuclides in marine bivalves. In general, the accumulation of radionuclides in bivalves is highly species and tissue-specific, which may be due to the different biological half-life of radionuclides in different species and tissues. The trophic pathway is the main pathway for the accumulation of most radionuclides in bivalves, with polonium-210 (210Po) and lead-210 (210Pb) potentially selectively accumulating in the digestive glands, while 134Cs and 137Cs selectively accumulating in the adductor muscle and mantle. Some other radionuclides (radium-226 (226Ra) and strontium-90 (90Sr)) are absorbed along with other minerals (e.g. Calcium) and selectively accumulate in bivalve shells. The information in this study can provide an overview of radionuclide contamination in marine bivalves.

Radiological dose and associated risk due to 210Po in commercial inter-tidal bivalves of southwest (Arabian Sea) coast of India

The activity concentration of ²¹⁰Po was determined in edible tissues of commercial bivalves on the southwest coast of India. The ²¹⁰Po activity ranged from 38.3 ± 6.9 Bq kg^-1 to 91.2 ± 18.6 Bq kg^-1. The annual committed effective dose (ACED) and lifetime carcinogenic risk (LCR) were calculated for different age groups to determine the potential health risk associated with bivalve consumption. The average ACED ranged from 81.5 to 194.1 μSv y^-1, with the 10th and 95th percentiles being 68 and 261 μSv y^-1, respectively. Lifelong mortality risk (LMTR) values ranged from 1.2 × 10^-3 to 2.9 × 10^-3, while lifetime morbidity risk (LMBR) values ranged from 1.9 × 10^-6 to 4.9 × 10^-6. The effective dose was found to be within the UNSCEAR limits.

Distribution, annual committed effective dose, and health safety assessment of 210Po in marine biota from Kalpakkam coast, Bay of Bengal

Seafood, intertidal biota, beach sediment, and seawater from Kalpakkam coast, Bay of Bengal were analyzed for ²¹⁰Po to evaluate the internal exposure and other radiological safety aspects. Kalpakkam houses various nuclear power generation facilities on its coast. The activity concentration of ²¹⁰Po was more pronounced in the intertidal organisms. Pelagic planktivorous fishes have the highest activity of the non-technogenic radionuclide, followed by the detrital feeders, benthic planktivores, benthic carnivores, and pelagic carnivore fishes. The affinity of ²¹⁰Po to organic detrital matter and planktonic organisms has led to a higher accumulation of radionuclide in planktivorous fishes. Activity concentration of ²¹⁰Po in seafood ranged between 1.13 ± 0.3 and 96.71 ± 1.6 Bq kg^-1 (Becquerel/kilogram). In seaweeds and gastropods, it ranged from 2.09 ± 0.2 to 8.21 ± 0.6 and from 9.31 ± 0.7 to 21.58 ± 1.2 Bq kg^-1, respectively. The committed effective dose (CED) of ²¹⁰Po in seafood varied from 31.18 to 456.68 μSv yr^-1 (microSievert/year). Radiological hazard parameters, such as activity intake, CED in consumption, of the seafood from this coast are within the acceptable levels prescribed by the International Commission on Radiological Protection and US Environmental Protection Agency.

Natural Polonium-210 in Bivalve Species in Peninsular Malaysia Waters as Recent Pollution Indicator

Po-210 is an alpha rays emitter in U-238 decay series and a natural radionuclide found in the ocean, and bivalve is the best biological indicator compared to the other organisms because of their feeding methods that are filter-feeding and suspension-feeding. They are able to accumulate toxic substances from marine environment in their tissue and researches were conducted in edible tissues of Meretrix meretrix, Perna virid, Glauconome virens, Anadara granosa, Anadara ovalis, Pholas orientalis, Donax sp., Polymesoda bengalensis, Phapia undulata, and Tellina virgate. Result showed Po-210 activity distributions were ranging from 2.61 ± 1.50 to 517.46 ± 56.64 Bq/kg. The lowest value of Po-210 activity recorded in Anadara granosa and the highest value recorded in Donax sp. Small-sized of bivalve species contained higher Po-210 activity than the larger one. Higher Po-210 contents in bivalve obtained from the west coast of Peninsular Malaysia might be closely related to anthropogenic factors from the coastline. This study also found that Donax sp. is able to be a good indicator of environmental pollutants as it accumulates Po-210 in higher concentrations than other bivalve species. Donax sp. can be found in several parts of Malaysia and available in large quantities but it appears to be seasonal. While for seafood safety monitoring, Anadara granosa is capable of becoming a good benchmark for seafood security as it found in most parts of Malaysia. It is not seasonal and a kind of Malaysian favorite seafood.

210Po and 210Pb activity concentrations in Greenlandic seabirds and dose assessment

Naturally occurring radionuclides, in particular, polonium-210 (²¹⁰Po), have a greater contribution than anthropogenic radionuclides to the annual effective dose received by the general public due to consumption of seafood. Knowledge of potential trophic sources and transfer of ²¹⁰Po to seabird species and subsequently to the Greenlandic people is, however, still poor. Here, we assess the transfer of ²¹⁰Po and ²¹⁰Pb to seabirds sampled during autumn and winter 2017 and 2018 in Greenland and provide a dose assessment. The activity concentrations of ²¹⁰Po in muscle and liver, respectively, ranged from 0.2 ± 0.1 Bq kg^-1 w.w. in glaucous gull (Larus hyperboreus) to 21.2 ± 22.6 Bq kg^-1 w.w. in thick-billed murre (Uria lomvia) and from 32.0 ± 9.4 Bq kg^-1 w.w. in common eider (Somateria mollissima) to 40.5 ± 49.0 Bq kg^-1 w.w. in thick-billed murre. ²¹⁰Po was non-uniformly distributed in the body of thick-billed murre. Kidneys and feathers showed higher ²¹⁰Po activity concentrations than heart and bone. The ²¹⁰Po/²¹⁰Pb activity concentration ratios are higher than unity, indicating that ²¹⁰Po is preferentially taken up by seabirds compared to its progenitor ²¹⁰Pb. The derived annual absorbed dose from ²¹⁰Po to the whole body of thick-billed murre was 6.4 × 10² ± 3.0 × 10² μGy. The annual effective dose to the average adult and representative person in Greenland due to ingestion of ²¹⁰Po in seabirds was estimated to 13.0 μSv and 57.0 μSv, respectively. This derived dose is low and poses a slight risk, and risk communication is therefore deemed unnecessary.

Peruvian scallop Argopecten purpuratus: From a key aquaculture species to a promising biondicator species

The present study analyzed the Peruvian scallop Argopecten purpuratus and its food sources for metal and fatty acid concentrations in order to determine spatial and temporal differences. Metals such as copper (Cu), manganese (Mn), and zinc (Zn) in gills and iron (Fe) and Zn in sediments were the most significant explaining factors for spatial differentiations (degree of contamination), while for fatty acids, it was C14:0, C15:0, C16:0 and C18:0 in A. purpuratus' muscle and in its food sources, which explained more temporal differences (El Niño-Southern Oscillation (ENSO) effect). Gills, digestive gland and intestine were the tissues where metal accumulation was the highest in A. purpuratus. Cd in digestive gland was always high, up to ∼250-fold higher than in other tissues, as previously reported in other bioindicator species for metal pollution. Fatty acids were good biomarkers when annual comparisons were performed, while metals when locations were compared. ENSO 2017 played an important role to disentangle A. purpuratus' biological conditions and food sources. A. purpuratus from Paracas locations mostly showed higher metal concentrations in gills and digestive glands, and lower fatty acid concentrations in muscle than those from Sechura and Illescas Reserved Zone.

A REVIEW ON 210Po AND 210Pb IN INDIAN SEAFOOD AND DOSE TO CONSUMERS

India is the second largest seafood producer in the world marketing more than 7000 edible species. In this regard, commendable studies have been conducted since the 1970s by different research groups and more data are reported. In this work, all the studies on 210Po and 210Pb measurements in abiotic and biotic components of India have been combined and reviewed. The concentrations of 210Po and 210Pb are estimated by radiochemical separation followed by alpha counting. Grain size, season, Tsunami waves and place of sampling have a decisive bearing on 210Po and 210Pb concentration in abiotic components. Plankton shows a higher Kd factor (104) compared to seaweeds and sea grass (103). Pond ecosystems recorded the highest Kd factor (4·3 × 104) compared to other freshwater and marine ecosystems. Bioaccumulation of 210Po and 210Pb varies with respect to variety of seafood. The committed effective dose (CED) calculated for shellfish species maintained a higher range of 2.5 × 10-2 mSv/y to 9.8 × 10-1 mSv/y and for fish species fluctuated from 3.8 × 10-4 mSv/y to 2.0 × 10-1 mSv/y. The studies conducted so far are scattered, and need to be gathered for future reference and planning (i.e. There is not much information available for Kerala, Karnataka, Maharashtra, Gujarat, Andhra, West Bengal and Odessa coast). Therefore, it is strongly recommended that further and more complete research is undertaken to study the bioaccumulation of 210Po and 210Pb from seafood. Overall, the present review concludes that Indian seafood is radiologically safe.

Mercury and Po-210 in mollusc species in the island of Gökçeada in the north-eastern Aegean Sea: Bioaccumulation and risk assessment for human consumers

Among the radioactive pollutants ²¹⁰Po is the most substantial one in terms of seafood safety due to its efficient accumulation in marine animals and high irradiation of its alpha emission. Mercury is a highly toxic metal for both marine organisms and human beings. Biomagnification of MeHg (methylmercury) through marine food chains has made Hg concern of ecotoxicology and seafood safety. In the current study, the bioaccumulation of ²¹⁰Po and THg (total mercury) were determined in 20 mollusc species, including 8 bivalves, 7 gastropods and 5 cephalopods collected from the island of Gökçeada in the north-eastern Aegean Sea. The highest accumulation of ²¹⁰Po and Hg was seen in bivalves and cephalopods, respectively. Elevated Hg concentrations in all body parts (arms, mantle and viscera) were observed in octopus' species. The results of this study suggests that filter feeder bivalves and gastropods have a capacity to concentrate ²¹⁰Po in their bodies, whereas predator gastropods and cephalopods have a capacity to concentrate Hg in their bodies. 7.0 kg (3.2-14.2) bivalve flesh intake is adequate due to ²¹⁰Po ingestion in the studied region to reach 1 mSv which is the annual committed effective dose. Octopus consumption of 705 g in a week alone is needed to reach Provisional Tolerable Weekly Intake (PTWI) of mercury, 5 μg kg^-1 body weight. Due to very low non-fish seafood consumption in Turkey there is no risk of Hg intake and alpha radiation of ²¹⁰Po above the limit values through mollusc consumption.

Oxidative and interactive challenge of cadmium and ocean acidification on the smooth scallop Flexopecten glaber

Ocean acidification (OA) may affect sensitivity of marine organisms to metal pollution modulating chemical bioavailability, bioaccumulation and biological responsiveness of several cellular pathways. In this study, the smooth scallop Flexopecten glaber was exposed to various combinations of reduced pH (pH/pCO₂ 7.4/∼3000 μatm) and Cd (20 μg/L). The analyses on cadmium uptake were integrated with those of a wide battery of biomarkers including metallothioneins, single antioxidant defenses and total oxyradical scavenging capacity in digestive gland and gills, lysosomal membrane stability and onset of genotoxic damage in haemocytes. Reduced pH slightly increased concentration of Cd in scallop tissues, but no effects were measured in terms of metallothioneins. Induction of some antioxidants by Cd and/or low pH in the digestive gland was not reflected in variations of the total oxyradical scavenging capacity, while the investigated stressors caused a certain inhibition of antioxidants and reduction of the scavenging capacity toward peroxyl radical in the gills. Lysosomal membrane stability and onset of genotoxic damages showed high sensitivity with possible synergistic effects of the investigated factors. The overall results suggest that indirect effects of ocean acidification on metal accumulation and toxicity are tissue-specific and modulate oxidative balance through different mechanisms.

Tracking trace elements into complex coral reef trophic networks

The integration, accumulation and transfer of trace elements across the main tropic levels of many food webs are poorly documented. This is notably the case for the complex trophic webs of coral reef ecosystems. Our results show that in the south-west lagoon of New Caledonia both abiotic (i.e. sediments) and biotic (i.e. primary producers, consumers and predators) compartments are contaminated by trace elements. However, our analyses revealed different contamination patterns from the sources of organic matter to the predators. The trophic levels involved in the sedimentary benthic food web (S-BFW, based on the sedimentary organic matter) and to a lesser extent in the reef benthic food web (R-BFW, based on algal turf) were mainly contaminated by trace elements that originate from mining activities like Ni and associated trace elements (Co, Cr, Fe, and Mn). Trace elements linked to agro-industrial (As, Hg, and Zn) and urban (Ag, Cd, Cu, Pb, Se, and V) activities were also integrated into the S-BFW, but preferentially into the R-BFW, and to a lesser extent into the detrital benthic food web (D-BFW, supplied by sea-grass plants). Most of the trace elements were biodiminished with increasing trophic levels along food webs. However, a marked biomagnification was observed for Hg, and suspected for Se and Zn. These results provide important baseline information to better interpret trace element contamination in the different organisms and trophic levels in a highly diversified coral reef lagoon.

210Po in the marine biota of Korean coastal waters and the effective dose from seafood consumption

The activity concentrations of ²¹⁰Po were determined in plankton and selected species of macroalgae, crustaceans, molluscs, and fish from Korean coastal waters to understand ²¹⁰Po distribution in these trophic levels and to assess the effective dose of ²¹⁰Po from seafood ingested by the average Korean. The activity concentration of ²¹⁰Po in macroalgae, mixed plankton, anchovy (whole body), abalone muscle, and abalone viscera was 0.97-1.43, 32-137, 59-392, 2.93 ± 0.86, and 1495 ± 484 Bq kg^-1 (w.w.), respectively. Polonium-210 concentration in the whole flesh of mussel and oyster were 47.8 ± 5.9 and 45.3 ± 7.1 Bq kg^-1 (w.w.), respectively. Polonium-210 concentration in the muscle of the five tested species of fish other than anchovy ranged from 0.51 to 5.56 Bq kg^-1 (w.w.), with the lowest amount in a demersal species. In fish, ²¹⁰Po activity concentration was as much as three orders of magnitude higher in viscera than in muscle. The average annual effective ²¹⁰Po dose per average Korean adult, who consumes 42.8 kg of seafood a year (excluding anchovy), was estimated to be 94 μSv y^-1, with 42-71% of this attributed to shellfish. Further studies are required to assess the dose of ²¹⁰Po from anchovy owing to its high activity concentration and the manner in which anchovy is consumed.

Two-Compartment Kinetic Modeling of Radiocesium Accumulation in Marine Bivalves under Hypothetical Exposure Regimes

Interpreting the variable concentrations of (137)Cs in the field biological samples requires mechanistic understanding of both environmental and biological behavior of (137)Cs. In this study, we used a two-compartment model to estimate and compare the (137)Cs biokinetics in three species of subtropical marine bivalves. Significant interspecific difference of (137)Cs biokinetics was observed among oysters, mussels, and scallops. There was considerable (137)Cs assimilation from phytoplankton in the bivalves, but the calculated trophic transfer factors were generally between 0.04 and 0.4. We demonstrated a major efflux of radiocesium in the scallops (with a rate constant of 0.207 d(-1)), whereas the efflux was comparable between oysters and mussels (0.035-0.038 d(-1)). A two-compartment kinetic model was developed to simulate the (137)Cs accumulation in the three bivalves under four hypothetical exposure regimes. We showed that the bivalves respond differently to the exposure regimes in terms of time to reach equilibrium, equilibrium concentration, and maximum concentration. Bivalves suffering more frequent intermittent exposure may have higher maximum concentrations than those receiving less frequent exposure. The interspecific difference of (137)Cs accumulation in bivalves has important implications for biomonitoring and implementing management techniques. This study represents one of the first attempts to combine both dissolved and dietary pathways to give a realistic simulation of (137)Cs accumulation in marine bivalves under dynamic exposure regimes.

Delineation of ¹³⁴Cs uptake pathways (seawater and food) in the variegated scallop Mimachlamys varia

Among bivalves, scallops have been shown to be good bioindicator species for radionuclide monitoring. The present paper looked at the Cs bioaccumulation capacities of the variegated scallop Mimachlamys varia exposed separately via seawater and food under laboratory conditions. Results were compared with data previously obtained for the king scallop Pecten maximus, the only Pectinid species for which Cs accumulation has been studied in laboratory. Results indicated that M. varia has higher uptake capacity (CF: 1.86 ± 0.08) but lower absorption efficiency (A0l: 33 ± 5%) than P. maximus when exposed to waterborne Cs (CF of P. maximus: 0.94 ± 0.05 and A0l: 45 ± 3%). When scallops were fed radiolabeled phytoplankton, the assimilation efficiency of Cs was similar for the two species (AE: 24 ± 3% for M. varia and 28 ± 4% for P. maximus). Interspecific differences in terms of accumulation and retention, can be explained by physiological factors (including size of individuals) and/or difference in storage mechanisms. Indeed, organotropism differed between the two scallop species, suggesting the occurrence of specific redistribution mechanisms towards the tissues involved in Cs storage, excretion and detoxification. Finally, the present study examined the relative contribution of the different exposure pathways (seawater and food) to global (134)Cs bioaccumulation for M. varia. Results showed that food constitutes the main accumulation pathway, contributing for 77% of the global (134)Cs bioaccumulation.

In situ evaluation of oxidative stress and immunological parameters as ecotoxicological biomarkers in a novel sentinel species (Mimachlamys varia)

Although the variegated scallop Mimachlamys varia seems to be a suitable sentinel species for contaminant monitoring, no study has identified biomarkers in this species. In order to fill this gap, this study conducted an in situ biomarker approach. M. varia were collected in contaminated and uncontaminated areas and responsiveness of oxidative stress and immunological biomarkers was evaluated in the digestive gland. In parallel, 14 trace element concentrations were evaluated in the same organ. Superoxide dismutase activity and malondialdehyde content responded efficiently to in situ contamination when a certain degree of contamination was reached. Laccase-type phenoloxidase showed a high sensitivity but saturation of the response was highlighted for the highest contaminations. Additionally, correlations were found between biomarkers and trace element concentrations. Taken together, results showed that biomarker approach conducted in the digestive gland of M. varia represents a sensitive analytical tool to highlight ecotoxicological issues in coastal marine ecosystems.

Biomarkers of environmental stress in gills of ribbed mussel Aulacomya atra atra (Nuevo Gulf, Northern Patagonia)

In this study, we assessed in gills of native ribbed mussels Aulacomya atra atra from three sites within Nuevo Gulf (Northern Patagonia) several biomarkers such as reactive oxygen species (ROS), lipid radicals (LR), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and metallothionein (MT). Furthermore, concentrations of main trace metals (Fe, Al, Zn, Cu, Cd and Pb) were quantified in mussel tissue. Results showed significant induction of SOD, GST, MT and MDA, as well as, higher concentration of Fe, Al and Cd in winter than in summer. The high MDA content measured in mussels from Folías Wreck seemed to be caused by the very high levels of Fe that would come from the corrosion of the vessel. Mussels from the control site Punta Cuevas presented the lowest levels of Cd and the highest of Al in winter. Despite positive correlations were found between Al and GST and MT, no spatial differentiation was detected in those biomarkers. On the other hand, MT was only related to Al been most likely influenced by environmental variables than by the trace metals. It has to be highlighted that the relationship detected among water temperature, nutrients and antioxidant responses in gills is probably related to the fact that this tissue is in direct contact with water and it is sensitive to its fluctuations. Taking into account that mussel gill is a tissue actively proliferating and the first target of contaminants present in water, so that changes in its antioxidant system can provide an earlier warning signal than in other tissues.

Potential human health risk by metal(loid)s, 234,238U and 210Po due to consumption of fish from the "Luis L. Leon" Reservoir (Northern México)

Concentrations of As, Cu, Fe, Hg, Pb and Zn and activity concentrations from 234,238U and 210Po in water, fillet, liver and gills were determined in three stocked fish species from the Luis L. Leon reservoir, located in Northern Mexico. The considered species were Lepomis cyanellus, Cyprinus carpio and Ictalurus furcatus. 238U and 234U activity concentration (AC) in fillet samples showed values of 0.007-0.014 and 0.01-0.02 Bq∙kg-1 wet weight (ww), respectively. Liver samples for L. cyanellus, C. carpio and I. furcatus present 210Po AC of 1.16-3.26, 0.70-1.13 and 0.93-1.37 Bq∙kg-1 ww. Arsenic, mercury and lead concentration intervals in fillet samples were 0.13-0.39, 0.005-0.126 and 0.009-0.08 mg∙kg-1 ww, respectively, while in gill samples they were 0.11-0.43, 0.002-0.039 and 0.02-0.26 mg∙kg-1 ww. The elemental Bioaccumulation Factor (BAF) for fish tissues with respect to their concentrations in water was determined. L. cyanellus showed the highest BAF values for As and total U, being BAFAs = 37 and 40 L∙kg-1 in fillet and gills, respectively, and BAFU total = 1.5 L∙kg-1 in fillet. I. furcatus showed the highest BAF values for Hg and Pb, being BAFHg = 40 and 13 L∙kg-1 in fillet and gills, and BAFPb = 6.5 and 22 L∙kg-1 in fillet and gills, respectively. Some metal(loid) concentrations are slightly higher than European regulations for fish fillets. The difference in concentrations of metal(loid)s in fillet among the studied species is probably due to their differences in diet and habitat.

Seasonal and spatial variations of 210Po and 210Pb activity concentrations in Mytilus galloprovincialis from Croatian coast of the Adriatic Sea

Results of 2 years monitoring of (210)Po and (210)Pb activity concentrations in soft tissue of the species Mytilus galloprovincialis from Croatian part of the Adriatic coast are presented. The samples were collected at thirteen coastal stations (some of which are also a part of the Mediterranean Mussel Watch Project) in spring and autumn of 2010 and 2011. The collected mussels were ranging between 4 cm and 6 cm in shell length. After sample pre-treatment lead and polonium were radiochemically separated on Sr resin. (210)Po was determined by alpha-particle spectrometry and (210)Pb was determined, via (210)Bi, by a low-level gas proportional counter. The results of (210)Po activity concentrations were found to vary between (104±11) and (1421±81) Bq kg(-1) dry weight while (210)Pb activity concentrations were much lower and in range (8.2±5.3)-(94.1±29.8) Bq kg(-1) dry weight. Higher (210)Po and (210)Pb activity concentrations were determined in spring period. The inter-site differences seen in their activity concentrations can be due to natural background levels of sites. The (210)Po/(210)Pb activity concentration ratios in all cases exceeded unity for all mussel samples and ranged between 4.0 and 47.9.

Characterization of ²⁴¹ Am and ¹³⁴Cs bioaccumulation in the king scallop Pecten maximus: investigation via three exposure pathways

In order to understand the bioaccumulation of (241)Am and (134)Cs in scallops living in sediments, the uptake and depuration kinetics of these two elements were investigated in the king scallop Pecten maximus exposed via seawater, food, or sediment under laboratory conditions. Generally, (241)Am accumulation was higher and its retention was stronger than (134)Cs. This was especially obvious when considering whole animals exposed through seawater with whole-body concentration factors (CF(7d)) of 62 vs. 1, absorption efficiencies (A(0l)) of 78 vs. 45 for seawater and biological half-lives (T(b½l)) of 892 d vs. 22 d for (241)Am and (134)Cs, respectively. In contrast, following a single feeding with radiolabelled phytoplankton, the assimilation efficiency (AE) and T(b½l) of (134)Cs were higher than those of (241)Am (AE: 28% vs. 20%; T(b½l): 14 d vs. 9 d). Among scallop tissues, the shells always contained the higher proportion of the total body burden of (241)Am whatever the exposure pathway. In contrast, the whole soft parts presented the major fraction of whole-body burden of (134)Cs, which was generally associated with muscular tissues. Our results showed that the two radionuclides have contrasting behaviors in scallops, in relation to their physico-chemical properties.

210Po in the marine environment with emphasis on its behaviour within the biosphere

The distribution and behaviour of the natural-series alpha-emitter polonium-210 in the marine environment has been under study for many years primarily due to its enhanced bioaccumulation, its strong affinity for binding with certain internal tissues, and its importance as a contributor to the natural radiation dose received by marine biota as well as humans consuming seafoods. Results from studies spanning nearly 5 decades show that (210)Po concentrations in organisms vary widely among the different phylogenic groups as well as between the different tissues of a given species. Such variation results in (210)Po concentration factors ranging from approximately 10(3) to over 10(6) depending upon the organism or tissue considered. (210)Po/(210)Pb ratios in marine species are generally greater than unity and tend to increase up the food chain indicating that (210)Po is preferentially taken up by organisms compared to its progenitor (210)Pb. The effective transfer of (210)Po up the food chain is primarily due to the high degree of assimilation of the radionuclide from ingested food and its subsequent strong retention in the organisms. In some cases this mechanism may lead to an apparent biomagnification of (210)Po at the higher trophic level. Various pelagic species release (210)Po and (210)Pb packaged in organic biodetrital particles that sink and remove these radionuclides from the upper water column, a biogeochemical process which, coupled with scavenging rates of this radionuclide pair, is being examined as a possible proxy for estimating downward organic carbon fluxes in the sea. Data related to preferential bioaccumulation in various organisms, their tissues, resultant radiation doses to these species, and the processes by which (210)Po is transferred and recycled through the food web are discussed. In addition, the main gaps in our present knowledge and proposed areas for future studies on the biogeochemical behaviour of (210)Po and its use as a tracer of oceanographic processes are highlighted in this review.

Polonium (210Po) and lead (210Pb) in marine organisms and their transfer in marine food chains

The determination of (210)Po and (210)Pb was performed in marine organisms from the seashore to abyssal depths, encompassing a plethora of species from the microscopic plankton to the sperm whale. Concentrations of those radionuclides ranged from low values of about 5 × 10(-1) Bq kg(-1) (wet wt.) in jellyfish, to very high values of about of 3 × 10(4) Bq kg(-1) (wet wt.) in the gut walls of sardines, with a common pattern of (210)Po > (210)Pb.These radionuclides are primarily absorbed from water and concentrated by phyto- and microzooplankton, and then are transferred to the next trophic level along marine food chains. Investigation in epipelagic, mesopelagic, bathypelagic and abyssobenthic organisms revealed that (210)Po is transferred in the marine food webs with transfer factors ranging from 0.1 to 0.7, and numerically similar to those of the energy transfer in the marine food chains. As (210)Po preferentially binds to amino acids and proteins, its transfer in food chains likely traces protein transfer and, thus, (210)Po transfer factors are similar to ecotrophic coefficients. (210)Pb is transferred less efficiently in marine food chains and this contributes to increased (210)Po:(210)Pb activity ratios in some trophic levels.

Increase of 210Po levels in human semen fluid after mussel ingestion

Polonium-210 ((210)Po) radioactive concentrations were determined in human semen fluid of vasectomized non-smoker volunteers. The (210)Po levels ranged from 0.10 to 0.39 mBq g(-1) (mean: 0.23 ± 0.08 mBq g(-1)). This value decreased to 0.10 ± 0.02 mBq g(-1) (range from 0.07 to 0.13 mBq g(-1)) after two weeks of a controlled diet, excluding fish and seafood. Then, volunteers ate during a single meal 200 g of the cooked mussel Perna perna L., and (210)Po levels were determined again, during ten days, in semen fluid samples collected every morning. Volunteers continued with the controlled diet and maintained sexual abstinence through the period of the experiment. A 300% increase of (210)Po level was observed the day following mussel consumption, with a later reduction, such that the level returned to near baseline by day 4.

Spatial and temporal variability of ²¹⁰Po and ²¹⁰Pb in mussels (Mytilus galloprovincialis) at the Turkish coast of the Aegean Sea

In this study, the activity concentrations of ²¹⁰Po and ²¹⁰Pb were determined in mussel samples (Mytilus galloprovincialis) collected from the Turkish coast of the Aegean Sea. The samples were collected seasonally for a period of two years (2004-2006) at six coastal stations (Çanakkale, Dikili, Foça, Çeşme, Didim, Bodrum). Mussels were separated into several groups according to their size (1-4,4-6,>6 cm). The results showed that ²¹⁰Po concentrations in mussels varied between 53±4 and 1960±60 Bq kg(-1)dw. The highest activity ²¹⁰Po concentrations were determined in winter samples of mussels with a shell length of 4-6 cm from Didim. In general, it was observed that the ²¹⁰Pb concentration levels in mussels were lower than ²¹⁰Po concentrations. The ²¹⁰Po/²¹⁰Pb activity concentration ratios exceeded unity for all mussel samples and averaged 26.0. The inter-site differences seen in ²¹⁰Po concentrations can be due to both the natural background levels of sites and industrial activities.

Tissue distribution of 210Po and 210Pb in select marine species of the coast of Kudankulam, southern coast of Gulf of Mannar, India

Activities of 210Po and 210Pb in various tissues of four species of decapod crabs and two species of cephalopod mollusks (cuttlefishes) of Kudankulam coast were studied. A non-uniform distribution of these radionuclides was observed between the organs. Of all the tissues, 210Po and 210Pb were found accumulated more in the hepatopancreas and intestine of crabs and in the digestive gland, shell gland, and intestine of cephalopods. Among crabs, Charybdis lucifera registered a little higher 210Po and 210Pb activities. The cephalopod species Loligo duvauceli displayed higher 210Po and 210Pb in some organs when compared to Sepia pharaonis. The muscle of all the species registered lower activity. In cephalopods, the activity ratio of 210Po/210Pb fell within the range of 1-2 for most of the organs, and in crab tissues, it varied from 1.7 to 31.4. The biological concentration factor for organs of cephalopods ranged from 1.2×10(3) to 4.3×10(5) for 210Po and 4.8×10(2) to 8.4×10(4) for 210Pb and for organs of crabs it varied between 2.0×10(4) and 1.9×10(6) for 210Po and 9.2×10(2) and 2.4×10(4) for 210Pb. The study revealed that the organs associated with digestion and metabolism displayed a higher activity concentration than the other tissues. A significant variation in the accumulation of 210Po and 210Pb was noted between species (P<0.05). The activity levels recorded are in agreement with values recorded in related organisms in other parts of the world. The data generated will act as a reference database for these organisms of this coast in which a nuclear power station is under construction.

Biomonitoring ²¹°Po and ²¹°Pb in marine brachyuran crabs collected along the coast of Kudankulam, Gulf of Mannar (GOM), India

Activities of ²¹⁰Po and ²¹⁰Pb in whole-body and in various tissues of brachyuran crabs collected along the Kudankulam coast were studied. A non-uniform distribution of these radionuclides was observed between the various tissues. Of all the tissues, ²¹⁰Po and ²¹⁰Pb were found to accumulate more in the hepatopancreas and intestine. Among the crabs studied, Charybdis lucifera registered higher ²¹⁰Po and ²¹⁰Pb activity. Muscle tissue in all the species registered lower activity. The ²¹⁰Po/²¹⁰Pb activity ratio was found to be greater than unity. The biological concentration factor for organs varied between ~ 10⁴ and 10⁶ for ²¹⁰Po and ~10² and 10⁴ for ²¹⁰Pb. A significant variation in the accumulation of ²¹⁰Po and ²¹⁰Pb was noted between species and between seasons (p < 0.05). The mean whole-body internal dose ranged from 1.42 to 6.86 μGy h⁻¹ for ²¹⁰Po and from 3.0 × 10⁻³ to 8.0 × 10⁻³ μGy h⁻¹ for ²¹⁰Pb. The external dose for ²¹⁰Po and ²¹⁰Pb was 2.41 × 10⁻⁶ to 5.76 × 10⁻⁶ μGy h⁻¹ and 4.14 × 10⁻⁵ to 8.26 × 10⁻⁵ μGy h⁻¹, respectively. The activity levels recorded are in agreement with values recorded in related organisms in other parts of the world. The total committed effective dose due to the intake of both radionuclides ranged from 80.3 to 871.7 μSv y⁻¹. The median dose calculated due to ²¹⁰Po and ²¹⁰Pb in certain crabs in Kudankulam is less and would not pose any significant radiological impact on health or a cancer risk to the public, and the seafood is considered safe for human consumption.

Natural radionuclides in seafood from the central Adriatic Sea (Italy)

Activity concentrations of ²¹⁰Po, ²¹⁰Pb, and ⁴⁰K were measured in different samples of marine organisms from the central Adriatic Sea. The marine organisms were purchased from the local consumer market during all four seasons of the year to evaluate the spatial and temporal distribution of the natural radioactivity. The concentration trend is the following: ⁴⁰K > ²¹⁰Po > ²¹⁰Pb. ⁴⁰K concentration ranged between 54.9 and 235.9 Bq kg⁻¹ fresh weight, and the arithmetic mean of Pb concentration for all samples is <0.7 Bq kg⁻¹ fresh weight. Po activity concentration ranged between 0.3 and 44.6 Bq kg⁻¹ fresh weight; its arithmetic mean was 5.7 ± 7.2 Bq kg⁻¹ fresh weight. Among the pelagic species, anchovy displayed the highest polonium concentration. The data obtained depend upon the type of marine organism and the period of sampling. Committed effective dose due to ²¹⁰Po ingestion from marine food for individuals in the two different population groups was calculated to be 95.9 and 466.4 μSv y⁻¹, respectively.

Factors affecting 210Po and 210Pb activity concentrations in mussels and implications for environmental bio-monitoring programmes

The activity of (210)Po and (210)Pb was determined in mussels of the same size (3.5-4.0 cm shell length) sampled monthly over a 17-month period at the Atlantic coast of Portugal. Average radionuclide concentration values in mussels were 759±277 Bq kg(-1) for (210)Po (range 460-1470 Bq kg(-1) dry weight), and 45±19 Bq kg(-1) for (210)Pb (range 23-96 Bq kg(-1) dry weight). Environmental parameters and mussel biometric parameters were monitored during the same period. Although there was no seasonal variation of radionuclide concentrations in sea water during the study period, the concentration of radionuclide activity in mussels varied seasonally displaying peaks of high concentrations in winter and low concentrations in summer. Analysis of radionuclide data in relation to the physiological Condition Index of mussels revealed that (210)Po and (210)Pb activities in the mussel (average activity per individual) remained nearly constant during the investigation period, while mussel body weight fluctuated due to fat storage/expenditure in the soft tissues. Similar variation of radionuclide concentrations was observed in mussels transplanted from the sea coast into the Tejo Estuary. However, under estuarine environmental conditions and with higher food availability throughout the year, transplanted mussel Condition Index was higher than in coastal mussels and average radionuclide concentrations were 210±75 Bq kg(-1) (dry weight) for (210)Po and 10±4 Bq kg(-1) (dry weight) for (210)Pb, therefore lower than in coastal mussels with similar shell length. It is concluded that the apparent seasonal fluctuation and inter-site difference of radionuclide concentrations were mostly caused by mussel body weight fluctuation and not by radionuclide body burden fluctuation. This interpretation can be extended to the apparent seasonal fluctuation in concentrations of lipophilic and lipophobic contaminants in mussels, and provides an explanation for occasional high concentrations of (210)Po and man-made contaminants measured in mussels far from pollution sources.

(210)Po and (210)Pb in the tissues of the deep-sea hydrothermal vent mussel Bathymodiolus azoricus from the Menez Gwen field (Mid-Atlantic Ridge)

The hydrothermal deep-sea vent fauna is naturally exposed to a highly specific environment enriched in potentially toxic species such as sulfides, metals and natural radionuclides due to the convective seawater circulation inside the oceanic crust and its interaction with basaltic or ultramafic host rocks. However, data on radionuclides in biota from such environment are very limited. An investigation was carried out on tissue partitioning of (210)Po and (210)Pb, two natural radionuclides within the (238)U decay chain, in Bathymodiolus azoricus specimens from the Mid-Atlantic Ridge (Menez Gwen field). These two elements showed different distributions with high (210)Pb levels in gills and high (210)Po levels in both gills and especially in the remaining parts of the body tissue (including the digestive gland). Various factors that may explain such partitioning are discussed. However, (210)Po levels encountered in B. azoricus were not exceptionally high, leading to weighted internal dose rate in the range 3 to 4 μGy h⁻¹. These levels are slightly higher than levels characterizing coastal mussels (~1 μGy h⁻¹).

210Po concentration in Perna perna mussels: looking for radiation effects

Twenty ropes with 400 Perna perna mussels seeds (3 cm shell size) were set-up on floating structures at Cabo Frio Island, Arraial do Cabo, approximately 100 km northeast of Rio de Janeiro city. A rope was taken out on a monthly basis, and the shell sizes of 100 seeds were measured. The haemolymph of 10 male and 10 female individuals was taken, and the same individuals were separated for 210Po/210Pb determination. After one year of monthly sampling, no clear correlation was observed between the 210Po concentration, mussel's age and weight. A mean 210Po concentration of 155 Bq kg(-1) wet weight basis, was obtained, which is comparable with data reported in the literature. The radiation dose did not have any observable effect on the micronuclei frequency and DNA breaks in the mussels. This was probably due to the low dose rate, 0.02 mGy d(-1), in comparison with the suggested potential dose limit of 10 mGy d(-1).

Distribution patterns of chalcogens (S, Se, Te, and 210Po) in various tissues of a squid, Todarodes pacificus

In order to elucidate the relationship between the chemically similar chalcogen elements S, Se, Te, and 210Po in marine invertebrates, we conducted a comparative study of the distribution patterns of these elements in a squid, Todarodes pacificus. Elemental concentrations of the four chalcogens were determined in (mantle) muscle, gill, stomach, and hepatopancreas tissues. No relationship between chalcogen concentrations and morphological parameters (mantle length, body weight, and sex) was evident. Gills showed slightly elevated levels of Se and 210Po, which may indicate absorption and uptake of these elements over the gill surface. All four chalcogens have their highest concentrations in the hepatopancreas and the lowest concentrations in the muscle tissue. However, concentration differences between tissues, revealed by (1) bioaccumulation values based on reference seawater values and (2) internal relative enrichment factors (IREF) based on enrichment of hepatopancreas compared to muscle tissue, were least pronounced for S, most distinct for 210Po, and moderate for Se and Te. Furthermore, no significant correlation for Se, Te, and 210Po with S within tissue concentrations, and only a slightly negative correlation between S and 210Po in the squid muscle and hepatopancreas tissues were found, which indicates either an antagonistic effect between, or a disconnection of the two elements through metabolic processing. Overall, the distribution patterns of Se and Te resemble those of essential trace elements, such as Zn and Cu, whereas 210Po is partitioned in a manner similar to toxic heavy metals, such as Cd and Ag.

Natural radioactivity in the mussel Mytilus galloprovincialis derived from the central Adriatic Sea (Italy)

The aim of this study was to determine background levels of natural radionuclides such as uranium isotopes, (210)Pb, (210)Po, and (40)K in mussels Mytilus galloprovincialis, collected in the central Adriatic Sea along the Marche region as a mechanism to establish a biomonitoring model for human radiation exposure resulting from ingestion of this species. This mussel is an invasive warm-water species largely consumed by the local population and also exported to different countries. Among natural radionuclides, alpha emitters are considered responsible for a significant proportion of the radiation exposure of humans to background radiation, particularly through food consumption. The sampling was conducted in different seasons of the year in order to evaluate the spatial and temporal distribution of the natural radioactivity. Data was also compared to previous findings to corroborate our findings. The mean of activity concentration found was 2.34 +/- 0.61 and 149 +/- 58 Bq/kg dry for total uranium and (210)Po, respectively. In mussels the concentration trend of the studied radionuclides was (40)K > (210)Po >> (210)Pb > uranium isotopes. The mean individual dose due to ingestion of mussels for (210)Po was in the range 1.65 yen 10(-2) to 9.20 yen 10(-2) mSv yr(-1). The dose derived from uranium isotopes, (40)K, and (210)Pb was negligible. Data show that mussels may be considered a reliable species model for human biomonitoring for radiation exposure.

Variations of 210Po and 210Pb in various marine organisms from Western English Channel: contribution of 210Po to the radiation dose

Measurements of (210)Po were carried out in various marine matrices (mussels, oysters, seaweed, fish, and abalones) and in seawater at several points along the French coast, over a period of 2 years (2003-2005). These measurements contribute to a better knowledge of this element, since few recent data exist for the French coast. Marked seasonal variations have been revealed in some species and there are differences according to the way of life of these species. Activities in mussels (Mytilus edulis) and oysters (Crassostrea gigas) are similar and varying between 90 and 600 Bq kg(-1) (d.w.). Activities in macroalgae (Fucus serratus) are lowest, between 4 and 16 Bq kg(-1) (d.w.). In oyster, abalone (Haliotis tuberculata) and fish (Solea solea, Sparus sp.), the strongest activities are measured in the digestive glands, the gills and the gonads. (210)Po/(210)Pb ratios in all cases have values of more than one for all species. From a significant number of measurements, CFs were calculated for seaweed (between 4.6 x 10(3) and 5.0 x 10(3)) and for molluscs, with highest CFs (>10(5)) found for the digestive gland and gills of the oysters, the digestive gland of the abalones and the liver of fish. Finally, the activities measured have made it possible to estimate the internal dose from chronic exposure due to (210)Po received by the marine organisms (0.05 microGh(-1) for macroalgae, between 0.70 and 1.5 microGh(-1) for mussels and oyster), and the contribution of seafood to the dose received by humans (46-129 microSvy(-1)).

Evaluation of the variegated scallop Chlamys varia as a biomonitor of temporal trends of Cd, Cu, and Zn in the field

This study assesses the potential of the scallop Chlamys varia as a biomonitor of metal contamination in the field. Cd, Cu, and Zn concentrations were determined in the soft tissues and organs of individuals from the French Atlantic coast sampled over a 1 year period and covering a wide range of size. All metals were selectively distributed among the different body compartments considered, and their concentrations were influenced by the size of the specimens or the sampling-season. The present work shows the importance of considering the body compartment, the sampling period and the size in studies aiming at using this scallop as a biomonitor species. Among tissues, the digestive gland and kidneys exhibited the highest metal concentrations whatever the season or the size. The digestive gland contained 65 and 48% of the whole Cd and Cu body burdens, respectively, and kidneys accounted for 85% of the Zn load. Those tissues are therefore particularly recommended for use in biomonitoring programs.

Subcellular and body distributions of 17 trace elements in the variegated scallop Chlamys varia from the French coast of the Bay of Biscay

Seventeen elements were analysed in the organs and tissues of the variegated scallop Chlamys varia, from the Atlantic coast of France. Concentration levels were determined in scallops of different sizes sampled in contaminated (La Rochelle Bay) and clean (Re Island) sites. Greater concentrations of Ag, Al, Ce, Cr, La, Mo, Nd, Ti, and V were found in the digestive gland while As, Cd, Co, Cu, Mn, Ni, Pb, and Zn were the highest in the kidneys. In the digestive gland, most of the metals were found in the insoluble fraction while As, Co, Cd, Mo, Ni, and V appeared to be mostly bound to soluble compounds. Among tissues, the adductor muscle always displayed the lowest trace element concentrations. According to size, Ag and Cd showed significantly higher concentrations in larger individuals, while Co and Zn were higher in the smallest ones. According to the sampling area, most of the metals, Ag, Al, Ce, Co, Cu, La, Mn, Nd, Pb, and Zn, showed significantly higher concentrations in La Rochelle Bay compared to the Re Island, reflecting differing inputs from industrial, domestic and harbour activities. However, Cr, Mo, Ni, Ti, and V concentrations did not display significant differences between sites and As and Cd were significantly higher at the Re Island. This study highlighted the ability of the variegated scallop C. varia to concentrate numerous trace elements to high levels, even those reported as poorly bioavailable for marine biota, such as rare earth elements.

Interspecific and geographical variations of trace element concentrations in Pectinidae from European waters

Cd, Cu and Zn were analysed in the organs and tissues of the three scallop species from the Bay of Biscay, the variegated Chlamys varia L., the queen scallop Aequipecten opercularis L. and the common scallop Pecten maximus L. for interspecific comparisons. In P. maximus the greatest concentrations of Cd and Cu were found in the digestive gland, whereas the two other species showed similar levels of Cd between digestive gland and kidneys and higher renal Cu concentrations. However, the digestive gland of all Pectinidae species contained from 75% to 93% and 52% to 74% of the total body burdens of Cd and Cu, respectively. Whatever the species, kidneys displayed the highest Zn concentrations, which therefore contained from 53% to 97% of the total body burden of this metal. Also using reported results, ratios between the concentrations in the digestive gland and that in the kidneys discriminated two groups of Pectinidae: (1) the Pecten group (P. maximus, P. jacobeus and Adamussium colbecki) with a Cd ratio > or = 4, a Cu ratio > or = 1 and a Zn ratio > 20x10(-3); (2) the Chlamys group with a Cd ratio < or = 1, a Cu ratio < or = 1 and a Zn ratio < or = 6x10(-3). However, no differences in the detoxification processes in the digestive gland were found between groups in this study. 72-80% of the total Cd was found to be soluble, probably bound to metalloproteins such as metallothioneins, while Cu and Zn were mainly found associated to the insoluble fraction of the digestive gland cells whatever the species. Queen scallops from the Faroe Islands were also considered to examine variations of the metal concentrations due to the geographical origin. In this northern area, queen scallops displayed Cd concentrations 2, 4 and 6 times higher in kidneys, muscle and digestive gland, respectively, compared to those from the Bay of Biscay. Consequently, the Cd concentrations in the whole soft parts of the queen scallops were more than 6 times higher in the Faroe Islands than in the Bay of Biscay. In contrast to Cd, both Cu and Zn concentrations in the whole soft parts were 2 times lower in the Faroe Islands, suggesting lower bioavailability of these essential elements.