Toxic Metals- TOXICITY OF HEAVY METALS:
Toxic Metals such as Ag , Cd , Cr , Cu , Hg , Mn , Mo , Ni , Pb , Sb , Tl , U , V and Zn tend to be relatively strongly adsorbed by soil constituents. Their mobility and bioavailability depend on the soil conditions. But some metals such as Cd and Zn which tend to be less strongly sorbet than Pb and Cu .
It can be leached down soil profiles. Especially under acid conditions. Industrial contaminated land often contains a suite of heavy metal contaminants present in high concentration.
Mines, smelters, foundries, paint factories, and scrap yards are likely to have been heavily contaminate. But examples of less obvious non-point sources of heavy metals are:
Sewage sludge disposal to land (range of metals), Pb in shotgun pellets. It Used for game bird and clay pigeon shooting, and Cd in phosphatic fertilizers.
Sources of toxic metals:
We are subjected to toxic metals in:
1. Our foods
2. As contaminants of air and water we use.
3. In the residues from the burning of fossil fuels.
4. From many manufacturing processes or products.
Some of the metals found predominantly as particulate matter in polluted atmospheres. They are known to be hazardous to human health.
All these are so all called “heavy metals” except for beryllium. Lead is the toxic metal of greatest concern in the urban environment. Because being present at a toxic level comes closest. Mercury is in second place
Others include beryllium , cadmium , chromium , vanadium , nickel and arsenic ( a metalloid ).
Due to its toxicity, volatility and versatility, ambient mercury is of concern. Particulate matter is contaminated with some ambient mercury. As toxic elemental mercury from coal combustion and volcanoes, much of the mercury entering the atmosphere does.
With the reduction of lead fuels. Atmospheric lead is less troubling than before. Leaded gasoline containing tetra ethyl lead was the predominant automotive fuel. Particulate lead halides were emitted in large quantities.
This occurs through the action of dichloroethane and dibromoethane added. As halogenated scavengers to prevent lead oxides from accumulating in engines. The lead halides formed are volatile enough to exit through the exhaust system. But condense in the air to form particles.
Beryllium is used to design specialized alloys used in electrical equipment, electronic equipment, space gear, and parts of the nuclear reactor, so that the production of beryllium is by no means equivalent to that of other toxic metals. Such as lead or mercury.
Nevertheless, the use of beryllium may increase in the future due to its “high-tech” applications.
The toxicity of beryllium and beryllium compounds became widely recognize. Because It has the lowest allowable limit in the atmosphere of all the elements. One of the main results of the recognition of beryllium toxicity hazards was the elimination of this element from phosphors ( coatings which produce visible light from ultraviolet light ) in fluorescent lamps.
General Statement of the Problems of Metal Toxicity:
Toxicity may result from acute and overwhelming exposure or it may be the result of a long or chronic exposure to low levels of a given toxic ant, and the mechanism of action may be quite different.
Toxicity is the unhealthful response of an organism to given toxic-ant, In this case a metal under definable conditions. Such as by a specified route of ingestion, in a given chemical form. At a definite dose and for a given time interval.