Metals In Shellfish Research Articles

Potential risk assessment of heavy metals by consuming shellfish collected from Xiamen, China

Concentrations of Hg, Pb, Cd, and Cr in 240 shellfish including oyster, short-necked clam, razor clam, and mud clam collected from six administrative regions in Xiamen of China were measured. The daily intakes of heavy metals through the consumption of shellfish were estimated based on both of the metal concentrations in shellfish and the consuming amounts of shellfish. In addition, the target hazard quotients (THQ) were used to evaluate the potential risk of heavy metals in shellfish on human body. Results showed that the concentrations of heavy metals in shellfish ranged at the following sequence: Cr > Cd > Pb > Hg. The concentrations of Hg and Pb in most samples were below the limits (0.3 mg kg(-1) for Hg and 0.5 mg kg(-1) for Pb) of national standard (GB 18406.4-2001) set in China. About 57 % of samples were found to contain more than 0.1 mg kg(-1) of Cd, in which the highest level was found in oyster from Xiangan with a value of 1.21 mg kg(-1). The average concentrations of Cd in oyster and mud clam samples were 0.338 and 0.369 mg kg(-1), respectively, which were significantly higher (p < 0.05) than those in the samples of short-necked clam and razor clam. The highest concentration of Cr was found to present in short-necked clam from Jimei with a value of 10.4 mg kg(-1), but a mean value of 1.95 mg kg(-1) in all the shellfish was observed, and no significant difference was found among the different sampling regions. The calculated daily intakes of Hg, Pb, Cd, and Cr through consuming the shellfish were 0.005, 0.122, 0.137, and 1.20 μg kg(-1) day(-1), respectively, which accounted for 2.19, 3.42, 13.7, and 40.1 % of the corresponding tolerable limits suggested by the Joint FAO/WHO Expert Committee on Food Additives. The THQ values of the four metals were far below 1 for most samples, except for those of Cd and Cr in the four shellfish species with the mean values of 0.132 and 0.385, respectively. The highest THQ values of Cd were observed in the species of oyster (0.719) and mud clam (0.568). But the high THQ values of Cr observed in all the four species were derived from the applied reference dose (RfD) data of Cr(VI) due to the unavailable RfD value of total Cr. The results indicate that the intakes of heavy metals by consuming shellfish collected from Xiamen of China do not present an appreciable hazard risk on human health, but attention should be paid to consuming those with relatively high THQ values, such as oyster, mud clam, and short-necked clam.

Determination of Some Heavy Metals in Shellfish

Determination of Some Heavy Metals in Shellfish

Metals in molluscs and algae: A north–south Tyrrhenian Sea baseline

We develop a 800 km long relative baseline of metal pollution for the Tyrrhenian Sea, from the north of Naples to south of Sicily (Italy), based on spatio-temporal (1997–2004) concentrations of trace metals in marine organisms and on the bioaccumulative properties of those organisms. The study concerns sites in the gulf of Gaeta-Formia, near Naples, and three islands north, west, and south of Sicily: Ustica, Favignana and Linosa. The five metals are: cadmium, chromium, copper, lead, and zinc; the species include: Monodonta turbinata ( n = 161), Patella caerulea ( n = 244) and the algae Padina pavonica ( n = 84). We use Johnson's (1949) [15] probabilistic method to determine the type of distribution that accounts for our data. It is a system of frequency curves that represents the transformation of the standard normal curves. We find an N–S pollution gradient in molluscs considered: the lowest metal pollution occurs around the Sicilian islands. Our method can accurately characterize marine pollution by contributing to: policy-making, coastal resources management, the assessments of environmental damages from marine accidents and other events. The method here presented is a useful tool for pollution comparisons purposes among ecosystems (i.e., risk monitoring) and it is an ideal starting point for its application on a global scale.

PIXE analysis of biological bodies in Uranouchi bay

We have investigated shellfish called Japanese littleneck clam ( Ruditapes philippinarum) which were collected from Uranouchi bay (Kochi, Japan) for analysis of elemental concentration by Particle Induced X-ray Emission (PIXE). A 4 MeV He ++ ion beam was used to analyze shellfish in the ion beam laboratory of Kochi University of Technology (Japan). In the present study, shellfish have been chosen as a representative of the biological bodies in the Uranouchi bay. The concentration of heavy metals in shellfish has been quantified and the results are compared with those obtained by analyzing Market shellfish. Analyzing shellfish collected from three different places in the bay Cu, Zn, Br, Sr and Zr are detected as heavy metals. Our results suggest that in comparison with Market shellfish the Uranouchi bay shellfish contain more heavy metals.

Heavy Metal Monitoring Using Bivalved Shellfish from Zhejiang Coastal Waters, East China Sea

The interest of culturing bivalved shellfish (including mussels, clams, oysters etc.), has increased in recent years, but the consumption has been hampered both by high levels of heavy metals and toxic algae. The levels of heavy metals (Hg, Cd, Pb, Zn, Cu and As) were determined in soft tissues of different shellfish from Zhejiang coastal waters, East China Sea. The average concentrations of the heavy metals analyzed exhibited the following decreasing order: Zn > Cu > As > Cd > Pb > Hg. Comparison of heavy metals concentrations among species indicated that Bivalves clearly have significant potential as useful bioindicators; however, the results indicated that no one species is universally suitable, as is true of any organism used in these studies. The distribution of the metals was also investigated along the Zhejiang coast, which the results showed the mean concentration of Hg and Cd detected did not vary greatly and presented a similar spatial pattern at different sampling stations, the concentrations of Zn and Pb were highly variable at different sampling sites. The amounts of heavy metals in soft tissue of shellfish were also compared with those from the related species from other seas in China and world marine waters. The results suggested that the coastal area might be considered relatively unpolluted with heavy metals and the concentrations of metals in shellfish also below the seafood safety limits for human consumption.

Heavy metals in molluscs from the Basque Coast (Northern Spain): results from an 11-year monitoring programme

Heavy metals in molluscs from the Basque Coast (Northern Spain): results from an 11-year monitoring programme

Cellular and subcellular distribution of metals in molluscs.

The cellular processes involved in metal metabolism in molluscs are reviewed, with emphasis on the contribution of microscopy (AMG, ARG, EPMA, and SIMS) to both basic research of metal cell biology and applied environmental research. In molluscs, metal uptake may occur by facilitated diffusion, active transport, or endocytosis, and can be enhanced by MT synthesis or formation of mineralized granules. In aquatic molluscs, gills constitute a key interface for dissolved metal uptake, where metals are bound to MT, incorporated into lysosomes, and released basally towards the blood plasma and circulating hemocytes. However, particulate metal uptake is mainly achieved via the digestive tract by endocytosis; further metals are transferred first to lysosomes and then to residual bodies, especially in the digestive cells of the digestive gland. Additionally, metals can be accumulated selectively in specific cell types. As ligands pools differ from cell to cell, different metals may be retained in different cell types. Class "a" metals are localized in cells with granules composed of carbonate, oxalate, phosphate, and sulfate (oxygen donors), whereas "b" metals are associated with those cell types rich in sulfur and nitrogen ligands (sulfur donors). In molluscs, oxygen donors occur in connective tissue calcium cells and basophilic cells, whereas sulfur donors are present in digestive cells, podocytes, nephrocytes, and rhogocytes. Hemocytes, which constitute the most relevant system for metal transport between tissues, move around the body and may penetrate tissues and remove metals from the inner medium to be accumulated in lysosomes as nondigested products. Rhogocytes also participate in metal mobilization, accumulation, and release. The assessment of metal levels in target cells of sentinel molluscs by microscopic techniques provides an early-warning measure, with promising applications as an exposure biomarker for environmental monitoring programs.

Distribution and relationships of selected trace metals in molluscs and associated sediments from the Gulf of Aden, Yemen

Concentrations of Cd, Pb, Zn, Cu, Ni, Co, Cr, Mn and Fe in the soft tissue of Turbo coronatus, Acanthopleura haddoni, Ostrea cucullata and Pitar sp., as well as in associated surface sediments (bulk and bioavailable metal concentrations) from the Gulf of Aden, Yemen, were determined by atomic absorption spectrophotometry method. Large differences between size-classes of molluscs in metal concentrations were recorded. Significant spatial differences in metal concentrations in both the soft tissue of the molluscs and associated sediments studied were mostly identified. Statistically significant correlations (p<0.01) between concentrations of selected metals were observed. A slope of the linear regression is significantly higher than unity for Fe (9.91) and Cd (3.45) in A. haddoni and for Ni (4.15) in T. coronatus, suggesting that the bioavailability of these metals is disproportionally increased with a degree of enrichment of the sediments in Fe, Cd and Ni, respectively. A slope constant approximating to unity (1.14) for Cu in A. haddoni relative to its concentration in sediment extract implies that bioavailability of this metal proportionally increased with growing concentrations of its labile forms in the associated sediment. The degree of contamination of Gulf of Aden waters by the metals studied is discussed and the potential ability of molluscs, especially A. haddoni and T. coronatus, as biomonitors of metallic pollutants is postulated.

Heavy Metal Concentrations in Water, Sediments and Mollusc Tissues

The highest concentrations of heavy metals (Cu, Pb, Zn, Mn, Co, Ni, Cd, and Cr) were found in water, sediment and molluscs of the Malkų Bay and the Smeltelė River. It was determined that after dredging the toxic sediment there was a noticeable decrease of heavy metals in sediment and molluscs from the Malkų Bay. However, low concentrations of heavy metals were found in the Vilhelmo Channel near Klaipėda waterworks. In the same channel near Dreverna the concentrations of heavy metals were much higher and that was associated with the presence of silt in the sediment. This study shows that bioaccumulation of heavy metals in mollusc tissues is dependent not only on their concentration in water but on many other factors as well.

Trace metals concentrations in marine organisms from the coastal areas of Bahrain, Arabian Gulf

A total of 162 fish and shellfish samples representing important species have been collected from different coastal areas of Bahrain in the Arabian Gulf, and analyzed for lead, cadmium, mercury, and arsenic using electrothermal atomic absorption spectrophotometric method. The dverall mean levels for Pb, Cd, Hg and As in fish samples were 0.132, 0.032, 0.084 and 1.7 µg g−1 wet weight, respectively, whereas for shellfish they were 0.149, 0.045, 0.042 and 3.61 µg g−1 wet weight. These values indicate higher levels of metals in shellfish when compared with fish, except for mercury, and reveal that generally the levels of metals in these organisms are lower than existing guidelines, except for arsenic.

Metals in molluscs and associated bottom sediments of the southern baltic

The concentration of Zn, Cu, Pb, Cd, Ni, Co, Ag, Mn, Fe, Ca, Mg, K and Na in molluscsMacoma balthica, Mya arenaria, Cardium glaucum, Mytilus edulis andAstarte borealis from the southern Baltic was determined. The surface sediments and ferromanganese concretions associated with the molluscs were also analysed for concentration of these metals. Species- and regiondependent differences in the metal levels of the organisms were observed. The properties of molluscs analysed which have a tendency toward elevated biological tolerance of selected trace metals were specified. The interelement relationship between metal concentrations in the soft tissue and the shell was estimated and was discussed.

Accumulation of cadmium and copper by the terrestrial snail Arianta arbustorum L.: kinetics and budgets.

Specimens of the terrestrial gastropod Arianta arbustorum were fed on cadmium- or copper-enriched agar plates with the aim of performing an input/output analysis and of studying the distribution of these metals in several organs of the snails. After a feeding period of 20 days about 45% of cadmium were lost. 36% accumulated in the hepatopancreas, where a cadmium concentration of more than 500 μg/g was measured. The efficiency of cadmium assimilation decreased from about 90% at the beginning to about 55% after 20 days. Copper was distributed more evenly than cadmium, but the main site of copper storage seemed to be the foot/mantle tissues, where 49% of the ingested copper were found. The efficiency of copper assimilation always exceeded 95%. The patterns of distribution and assimilation of copper and cadmium are discussed in relation to differences in the cytological and biochemical detoxification mechanisms which exist for these metals in molluscs.

Determination of heavy metals in shellfish by flame atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry

Shellfish samples (clams, oysters and mussels) were analysed for Pb, Cd, Cu, Cr, Zn and Ni by flame atomic absorption spectrometry (FAAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) following wet-ash digestion. Split samples were taken for both FAAS and ICP-AES analysis. Vanadium was used as the internal standard for ICP-AES whereas 1.25% NaCl was added to the FAAS standards to correct for the high salt background associated with shellfish.The methods were compared for statistical significance using regression analysis, the F-test and Student's t-test. Precision and accuracy were determined by replicate analyses, recovery of added heavy metals and National Bureau of Standards (NBS) reference materials. Results obtained from regression analysis for the coefficient of determination or “goodness of fit” were all above the acceptable 0.80 level. The t-test showed that the methods were statistically similar for all metals tested at the 95% confidence level. Average percentage recoveries ranged from 80.2 to 100.7%. Heavy metals were added at approximate expected levels normally found in the shellfish.Accuracy, based on heavy metal levels determined by FAAS and ICP-AES versus certified values for NBS reference materials, varied with the individual reference materials tested. The over-all data obtained indicated that FAAS and ICP-AES showed good agreement for the determination of the heavy metals tested, ICP-AES providing a drastic reduction in analysis time following initial sample work-up.

On the metabolic requirements for copper and zinc in molluscs and crustaceans

Abstract Theoretical estimates have been made of the minimum metabolic requirements of copper and zinc in molluscs and crustaceans. Enzymatic requirements of both groups are estimated to be 26·3 μg Cu g −1 dry weight and 34·5 μg Zn g −1 dry weight. The possession of haemocyanin as a respiratory pigment adds a further non-enzymatic metabolic requirement of 125·0 and 57·4 μg Cu g −1 dry weight to certain gastropod molluscs and to some crustaceans such as decapods. It is argued that metabolically functional copper and zinc often make up significant proportions of the total content of these metals in molluscs and crustaceans from non-polluted environments, especially the open ocean.

Heavy metals in shellfish from Scottish waters

The concentration of four heavy metals (copper, zinc, cadmium and lead) has been measured in a number of shellfish collected from coastal areas of Scotland. For three shellfish (lobster, crab and scallops) details are given of the distribution of these trace metals within the individual body. The data collected permits only limited conclusions to be made regarding geographical variation.