Title: Environmental Effects of Cadmium in Freshwater. A Bibliography
Authors: WALLEN J.WIGHTMAN A.s.PENNING Willem
Citation: Freshwater Biological Association no. 23
Publication Year: 1984
JRC Publication N°: JRC4016
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC4016
Type: Articles in Journals
Abstract: CADMIUM HAS WIDESPREAD USE IN INDUSTRIAL PRODUCTS, INCLUDING BATTERIES, PIGMENTS, PLASTIC STABILIZERS, ELECTROPLATING MATERIAL AND ALLOYS. THE MANUFACTURING PROCESSES RESULT IN ITS DISCHARGE TO THE ENVIRONMENT VIA THE AIR AND AQUATIC SYSTEMS, CAUSING CONCERN FOR THE POTENTIAL IM- PACT ON ECOSYSTEMS AND HUMAN HEALTH. ONCE RELEASED INTO THE AQUATIC ENVIRONMENT, CADMIUM EXISTS IN EITHER THE DISSOLVED OR THE PARTICULATE FORM (I.E. ADSORBED ON SOLID SURFACES, INCORPORATED INTO ORGANISMS, CHEMICALLY BOUND TO ORGANIC MATTER OR AS A SOLID PRECIPITATE). THE DEGREE OF CONTAMINATION IS REFLECTED IN AN INCREASED LEVEL OF THE METAL IN THE SOLID COMPONENT OF SEDIMENT- WATER SYSTEMS. THE EXACT FORM, AS IONS, COMPLEXES OR CHELATES, COLLOIDS OR ADSORBED TO ORGANIC AND INORGANIC SUBSTRATES, DICTATES NOT ONLY ITS TOXICITY, BUT ALSO ITS AVAILABILITY TO AN UPTAKE BY AQUATIC BIOTA. AQUATIC SYSTEMS ARE PARTICULARLY SENSITIVE TO THE INFLUENCE OF POLLU- TANTS, MAINLY DUE TO THE STRUCTURE OF THEIR FOOD CHAINS. COMPARED TO TERRESTRIAL SYSTEMS, A RELATIVELY SMALL BIOMASS OCCUPIES A COMPLEX NETWORK OF TROPHIC LEVELS. PARTITIONING OF CADMIUM BETWEEN THE VARIOUS COMPARTMENTS OF THE FOOD WEB INCREASES THE LIKELIHOOD OF BIOACCUMULATION BY SOME ORGANISMS. IT MAY ENTER THROUGH TRANSLOCATION FROM THE SUB- STRATE BY ROOTS OF MACROPHYTES OR AT A HIGHER TROPHIC LEVEL THROUGH UP- TAKE IN FOOD, DIRECT ABSORPTION FROM THE WATER OR BY INGESTION OF PAR- TICULATE MATERIAL DURING SUCH PROCESSES AS FILTER-FEEDING. ONCE IT IS ABSORBED, THE PHYSIOLOGICAL EFFECTS ARE MODIFIED NOT ONLY BY EXTERNAL CONDITIONS, BUT ALSO BY THE SUSCEPTIBILITY OF THE SPECIES CONCERNED. THE LIFE-STAGE OF THE ORGANISM, ITS GENETIC HISTORY, ITS ABILITY TO TOLERATE INCREASED TISSUE LEVELS OR TO METABOLIZE AND EXCRETE THE METAL EFFICIENTLY, ALL CONTRIBUTE TO A WIDE VARIATION IN THE LETHAL AND SUB- LETHAL EFFECTS WHICH EXPOSURE TO CADMIUM MAY INDUCE. THE ABILITY OF ORGANISMS TO ACCUMULATE HEAVY METALS ALSO HAS PRACTICAL APPLICATION. BY MONITORING INCREASED BIOLOGICAL LEVELS IN SELECTED "INDICATOR SPECIES", THESE MAY BE USED AS SENSITIVE INDICES OF THE DEGREE OF CONTAMINATION IN A POLLUTED ECOSYSTEM AND THE FLUCTUATIONS TO WHICH IT MAY BE SUBJECTED. LIFE-CYCLE TOXICITY TESTS MAY ALSO HAVE PREDICTIVE VALUE IN SETTING SAFE LIMITS FOR EFFLUENT RELEASED INTO THE ENVIRONMENT. THE INTERACTION OF SEVERAL POLLUTANTS IS ALSO OF GREAT IMPORTANCE IN ASSESSING THEIR BIOLOGICAL IMPACT. SIMULTANEOUS EXPOSURE TO DIFFERENT METALS AND NATURAL SOURCES OF STRESS MAY HAVE SEVERE EFFECTS ON THE BIOTA. CADMIUM IS NORMALLY FOUND IN ASSOCIATION WITH OTHER HEAVY METALS, NOTABLY ZINC, AND THE PHENOMENA OF ANTAGONISM AND SYNERGISM MODIFY THE TOXICITY OF THE ELEMENTS PRESENT. THE DISPLACEMENT OF ZINC BY CADMIUM IN ENZYME SYSTEMS MAY RESULT IN THE DISTRUPTION OF NORMAL METABOLISM. SOME ORGANISMS REDUCE THIS EFFECT BY THE INDUCTION OF METALLOTHIONEINS CYTOPLASM.
JRC Institute:Joint Research Centre Historical Collection

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