Bone, cadmium toxicity

Chronic cadmium toxicity occurs in industrial workers exposed to cadmium fumes. The symptoms are those of nephrotoxicity, bone disease and. to a lesser extent, hepatotoxicity. Renal stone formation may be increased. 

Probably the most notorious case of cadmium toxicity was the disorder known as Itai-Itai disease which occurred in Japan after World War II. This was essentially an osteomalacia associated with serious kidney damage and is discussed in Chapter 6.6.4. Changes in bones associated with cadmium toxicity have been described by Nicaud [44] and a specific effect is proteinuria caused by damage to kidney tubules [45-47]. Acute necrosis of the testes has also been reported [48] at relatively low doses of cadmium, although this effect does not seem to be a feature of chronic cadmium toxicity. Chronic bronchitis, hypertension and cardiovascular disease have also been reported as being associated with cadmium toxicity [49]. 

The most common toxic metals in industrial use are cadmium, chromium, lead, silver, and mercury less commonly used are arsenic, selenium (both metalloids), and barium. Cadmium, a metal commonly used in alloys and myriads of other industrial uses, is fairly mobile in the environment and is responsible for many maladies including renal failure and a degenerative bone disease called "ITA ITA" disease. Chromium, most often found in plating wastes, is also environmentally mobile and is most toxic in the Cr valence state. Lead has been historically used as a component of an antiknock compound in gasoline and, along with chromium (as lead chromate), in paint and pigments. 

Another important storage depot for toxic compounds is the skeleton. In particular, cadmium and lead bind and accumulate in the bone tissue from which they are released very slowly. The half-life of elimination of cadmium is several years, the half-life of lead is several months. 

Zinc and cadmium have an oxidation number of +2 in all their compounds. Zinc is an essential element for human health. It is present in many enzymes and plays a role in the expression of DNA and in growth. Zinc is toxic only in very-high amounts. However, cadmium is a deadly poison that disrupts metabolism by-substituting for other essential metals in the body such as zinc and calcium, leading to soft bones and to kidney and lung disorders. 

Cadmium is nutritionally non-essential, toxic and a ubiquitous environmental pollutant. It is found in leafy vegetables, grains and cereals, and since it is present in substantial amounts in tobacco leaves, cigarette smokers on a packet a day can easily double their cadmium intake. It has a long biological half-life (17-30 years in man), accumulates in liver and kidneys and its toxicity involves principally kidney and bone (Goyer, 1997).While Cd interferes primarily with calcium, it also interacts with zinc and can induce the synthesis of metallothionein. Cadmium bound to metallothionein in liver or kidney is thought to be non-toxic, but cadmium in plasma... 

The human body also absorbs certain elements such as gold and aluminum from food, water, and air that are not useful but are also not dangerous in such tiny amounts. When the body absorbs more toxic elements such as uranium, lead, and cadmium, however, tiny amounts stored in the bones and liver can cause serious harm. 

Cadmium is an environmental and occupational pollutant that is associated with nephrotoxicity (1) and bone toxicity (2) even low concentrations can impair renal function and/or increase bone fragihty. Cadmium is also an adulterant in infant formulas and weaning foods. 

It should be noted that in the majority of the above mentioned studies, metal-induced renal injury was considered as if exposure occurred to only one metal at a time. In reality it is clear that environmental and occupational exposure may involve several metals at the same time and in varying concentrations [34]. It has been shown that with combined exposure various metals may interact with each other and that one metal may alter the potential toxicity of another in either a beneficial or deleterious way. As an example, whilst arsenic has been shown to worsen cadmium-induced nephrotoxicity, data from experimental studies have shown that selenium may protect against the renal effects induced by cadmium [52]. Other studies have shown that the iron status may alter the toxic effects of aluminium at the level of the bone and the parathyroid gland [53,54], whilst in a recent increased lead accumulation was associated with disturbances in the concentration of a number of essential trace elements [55]. 

Osteoporosis is a condition characterized by a loss of bone mass and density that has been causally related to exposure to cadmium, a toxic heavy metal that is widely distributed in the ambient environment. In a Chinese study, a dose-response relationship between cadmium exposure and osteoporosis was demonstrated. M Other studies have demonstrated that... 

Bones are actually living protein networks to which minerals attach themselves. Not aU of the minerals deposited on bones are essential to bone building. There are at least two dozen elements in bones that have no known function in the human body, as well as a handful of nonessential elements, such as boron, strontium, silicon, barium, bismuth, and arsenic (yes, arsenic), that are believed to do some good. Five toxic elements—lead, cadmium, mercury, polonium, and radium—are often found in human bones. As long as they are stabilized in the bones, they do no apparent harm. 

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