Shellfish metals

Textile dyes were, until the nineteenth century invention of aniline dyes, derived from biological sources plants or animals, eg, insects or, as in the case of the highly prized classical dyestuff Tyrian purple, a shellfish. Some of these natural dyes are so-caUed vat dyes, eg, indigo and Tyrian purple, in which a chemical modification after binding to the fiber results in the intended color. Some others are direct dyes, eg, walnut sheU and safflower, that can be apphed directly to the fiber. The majority, however, are mordant dyes a metal salt precipitated onto the fiber facUitates the binding of the dyestuff Aluminum, iron, and tin salts ate the most common historical mordants. The color of the dyed textile depends on the mordant used for example, cochineal is crimson when mordanted with aluminum, purple with iron, and scarlet with tin (see Dyes AND DYE INTERMEDIATES). 

Citric acid is used in carbonated beverages to provide tartness, modify and enhance flavors, and chelate trace metals. It is often added to jams and jellies to control pH and provide tartness. It is used in cured and freeze-dried meat products to protect the amino acids (qv) and improve water retention. Bakers use it to improve the flavor of fmit fillings in baked goods. Because citric acid is a good chelator for trace metals, it is used as an antioxidant synergist in fats and oils, and as a preservative in frozen fish and shellfish (7) (see Antioxidaisits). 

Fish and Shellfish. Sardines in oil and also in tomato sauce and mustard sauce are packed commercially in enameled aluminum cans. However, tomato and mustard sauces are corrosive products that can attack metal containers. Sardines prepared in these sauces should not exceed 3.0% total acidity, expressed as acetic acid. Otherwise, the presently used interior can enamels will not protect the food sufficiently to prevent chemical reactions with the metal. 

Valuable contributions were made by two Canadian agencies, particularly by the National Research Council Canada (NRCC) who, from about 1976, provided marine and marine biological CRMs certified for metals, metal species and organic constituents (Berman 1984 Willie 1997). More recently their Halifax laboratories have issued a highly respected range of CRMs for the determination of shellfish toxins. Another Canadian producer, the National Water Research Institute (NWRI) specialized in marine (water and sedimentary) CRMs, and from the late 1980 s their matrix materials certified also for organic compounds (Chau et al. 1979 Lee and Chau 1987). 

The Ebro catchment is the largest river basin in Spain. It covers an area of 85,362 km2 (http //www.chebro.es) and receives the potential influence of three million people. It suffers a considerable ecological impact from different industrial activities located predominantly in the last third of its course. These activities result on the release to the Ebro River and to some of its tributaries of Tm quantities of chlorinated organic compounds, PBDE and other brominated flame retardants, mercury, and other metals. In addition, intensive agricultural practices, mainly concentrated in the last 30 km of the river course and in its Delta, imply the use of large quantity of pesticides and fertilizers. In this paper, we review physiological effects of these pollutants in resident fish and shellfish populations and provide a general picture of the health status of the low course of the Ebro River. 

Kopfler, F.C. and J. Mayer. 1967. Studies of trace metals in shellfish. Pages 67-80 in Proc. Gulf South Atlantic States Shellfish Sanit. Res. Conf. 

Shuster, C.N., Jr. and B.H. Pringle. 1969. Trace metal accumulation by the American Oyster, Crassostrea virginica. 1968 Proc. Nat. Shellfish. Assoc. 59 91-103. 

Topping, G. 1973. Heavy metals in shellfish from Scottish waters. Aquaculture 1 379-384. 

Palmer, J.B. and G.M. Rand. 1977. Trace metal concentrations in two shellfish species of commercial importance. Bull. Environ. Contam. Toxicol. 18 512-520. 

Berrow, S.D. 1991. Heavy metals in sediments and shellfish from Cork Harbour, Ireland. Mar. Pollut. Bull. 22 467-469. 

The actual analysis of the samples started with a qualitative survey to identify the principal metals present. ICP-AES was selected as being most suitable for this because it provided a permanent record, a multi-element analysis, and good sensitivity. Solutions of the shellfish tissue were prepared for analysis by wet oxidation, and the sediments were digested with 40% v/v... 

Outline analysis of shellfish for heavy metal pollutants. 

A team of more than 40 scientists assembled at the National Research Council of Canada to solve what came to be called the amnesic shellfish poisoning mystery. Scientists had already tested for bacteria, heavy metals, and pesticides that they knew could cause sickness, but none of these were the cause.The mussel samples were a mixture of thousands of different chemical compounds, and scientists didn t even know what many of them were. How can you separate out an unknown when you don t know what you re looking for or what its properties are ... 

Trace metals Zinc Red meats, shellfish, wholegrain cereals Involved in many metabolic reactions stabilisation of structure RNA, DNA and ribosomes Binding of some transcription factors to DNA Stabilisation of insulin complex in storage granules... 

Cadmium (Cd) Lung, emphysema, kidney, calcium metabolism, possible lung carcinogen Shellfish, cigarette smoke, taken up by plants, metal alloy - welding... 

Cadmium is a widely distributed metal used in manufacturing and is present in a number of consumer products. Dietary exposure to cadmium is possible from shellfish and plants grown on cadmium-contaminated soils. Absorption is increased when associated with low levels of iron or calcium in the diet. Some plants, such as tobacco, can concentrate cadmium from even low levels in the soil. The lung readily absorbs cadmium, thus cigarette smokers have elevated cadmium exposure. Cadmium is also used as a metal alloy, in paint, and in batteries (Ni-Cad, nickel-cadmium). Workplace exposure can occur in welding and battery manufacture. 

Researchers claim that the engineered chitosan beads appear to adsorb selected heavy metals as efficiently as the best commercial processes now being used. They also believe that future research will enable recycling of the metals and reuse of the chitosan. The process also provides an economic use of tons of crab sheUs (the source of chitosan) that are currently disposed of as trash by the shellfish producing industry. 

Chitosan Chitosan has a molecular structure similar to cellulose. This material is produced from chitin, which is widely found in the exoskeleton of shellfish and crustaceans. Chitin is the second most abundant natural biopolymer after cellulose. Chitosan is a good adsorbent for all heavy metals. It has been estimated that chitosan can be produced from shellfish and crustaceans at a market price of 15.43 /kg. 

Breathing contaminated workplace air, battery manufacturing, metal soldering or welding, eating food such as shellfish, liver, and kidney meats, and breathing cadmium in cigarette smoke are easy ways for cadmium to enter the body.49,50... 

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