In this review, we address the identification of residual chemical hazards in shellfish collected from the marine environment or in marketed shellfish. Data, assembled on the concentration of contaminants detected, were compared with the appropriate regulatory and food safety standards. Moreover, data on human exposure and body burden levels were evaluated in the context of potential health risks.Shellfish farming is a common industry along European coasts. The primary types of shellfish consumed in France are oysters, mussels, king scallops, winkles,whelks, cockles, clams, and other scallops. Shellfish filter large volumes of water to extract their food and are excellent bioaccumulators. Metals and other pollutants that exist in the marine environment partition into particular organs, according to their individual chemical characteristics. In shellfish, accumulation often occurs in the digestive gland, which plays a role in assimilation, excretion, and detoxification of contaminants. The concentrations of chemical contaminants in bivalve mollusks are known to fluctuate with the seasons.European regulations limit the amount and type of contaminants that can appear in foodstuffs. Current European standards regulate the levels of micro-biological agents, phycotoxins, and some chemical contaminants in food. Since 2006, these regulations have been compiled into the "Hygiene Package." Bivalve mollusks must comply with maximum levels of certain contaminants as follows:lead (1.5 mg kg-1), cadmium (1 mg kg-1), mercury (0.5 mg kg-1), dioxins (4 pg g-1 and dioxins + DL-PCBs 8 pg g-1), and benzo[a]pyrene (10 μp.g kg-1).In this review, we identify the levels of major contaminants that exist in shellfish(collected from the marine environment and/or in marketed shellfish). The follow-ing contaminants are among those that are profiled: Cd, Pb, Hg, As, Ni, Cr, V,Mn, Cu, Zn, Co, Se, Mg, Mo, radionuclides, benzo[a]pyrene, PCBs, dioxins and furans, PAHs, TBT, HCB, dieldrin, DDT, lindane, triazines, PBDE, and chlorinated paraffins.In France, the results of contaminant monitoring have indicated that Cd, but not lead (< 0.26 mg kg-1) or mercury (< 0.003 mg kg-1), has had some non-compliances. Detections for PCBs and dioxins in shellfish were far below the regulatory thresholds in oysters (< 0.6 pg g-l), mussels (< 0.6 pg g-1), and king scallops (< 0.4 pg g-1). The benzo[a]pyrene concentration in marketed mussels and farmed shellfish does not exceed the regulatory threshold. Some monitoring data are available on shellfish flesh contamination for unregulated organic contaminants.Of about 100 existing organo stannic compounds, residues of the mono-, di-, and tributyltin (MBT, DBT, and TBT) and mono-, di-, and triphenyltin (MPT, DPT,and TPT) compounds are the most frequently detected in fishery products. Octyltins are not found in fishery products. Some bivalve mollusks show arsenic levels up to 15.8 mg kg-1. It seems that the levels of arsenic in the environment derive less from bioaccumulation, than from whether the arsenic is in an org...

The aim of the present work was to study the effect of Cd2+ exposure on metallothionein (MT) induction and on the distribution of metals (Cd, Cu, and Zn) in the terrestrial pulmonate Helix aspersa. In particular, the soluble and nonsoluble pools of the accumulated metals and their tissue distribution in uncontaminated and contaminated edible snails were investigated after a two-week exposure to Cd2+. In the soluble cytosolic pool of the midgut gland of H. aspersa, three metal-specific putative MT isoforms were separated following a fractionation protocol with diethylaminoethyl cellulose, size-exclusion chromatography, ultrafiltration, and reversed-phase high-performance liquid chromatography (RP-HPLC). Interestingly, one of the above isoforms seems to bind both Cd and Cu, which may in addition mobilize, after induction by Cd2+, some of the intracellular Cu and, thus, perhaps increase the Cu pool in the cytosolic fraction. The cDNA and its translated amino acid sequence of a Cd2+-binding MT isoform from the snail midgut gland was characterized and attributed to one of the putative MT isoforms obtained by RP-HPLC. The amino acid sequence of this Cd-MT isoform of H. aspersa differed from similar sequences described in other terrestrial pulmonates, such as Helix pomatia or Arianta arbustorum, by only a few amino acids (n = 4 and 8, respectively). That the identified Cd-MT from H. aspersa is inducible by Cd2+ also was shown, chromatographic evidence aside, by a specific polymerase chain reaction protocol on a cDNA basis, which included a noninducible housekeeping gene as a control.

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