Cadmium biological half-life

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... 

On the basis of chemical profile, Wood (38) predicted that arsenic, selenium, and tellurium will be methylated in the environment, and lead, cadmium, and zinc will not. Elemental concentration in the aquatic food chain has been reported for As (39), Hg (40), Cd (41), Pb (42), and Cu (43). The biological half-life of methylmercury in fish, for example, is one to two years (44). Pillay et al. (40) implicated heavy coal burning in the mercurial contamination of plankton and fish populations of Lake Erie. Other metals, notably cadmium, have been shown to be incorporated into the grazing grasses surrounding a coal burning source (27). Trace element contamination, therefore, can enter the food chain at various points. Disposal of solid wastes in the form of ash and slag is yet another environmental consideration (45). 

Cadmium is a cumulative toxicant with a biologic half-life of up to 30 years in humans. More than 70% of the cadmium in the blood is bound to red blood cells accumulation occurs mainly in the kidney and the liver, where cadmium is bound to metallothionein. In humans the critical target organ after long-term exposure to cadmium is the kidney, with the first detectable symptom of kidney toxicity being an increased excretion of specific proteins. 

Cadmium has a long biological half-life, 10 to 12 years in humans thus low-level chronic exposure will eventually result in accumulation to toxic concentrations. 

Cadmium is a highly cumulative poison with a biologic half-life estimated at about 20 to 30 years in humans. About half of the body burden of cadmium is found in the liver and kidneys. The total body burden reaches a plateau in humans around age 50. Cigarette smoke is a source of cadmium, and the body burden of cadmium is about 1.5 to 2 times greater in smokers than in nonsmokers of the same age. 

Cadmium is a silver-white metal with an atomic weight of 112.4 and a low melting point of 321 °C. It is malleable and can be rolled out into sheets. The metal unites with the majority of the heavy metals to form alloys. It is readily oxidized to the +2 oxidation state, giving the colorless Cd2+ ion. Cadmium persists in the environment its biological half-life is 10 to 25 years. 

Cadmium is accumulated extraordinarily strongly in the human body. In newborn infants, the total cadmium amount is usually approximately 1 pg and by the 50th year of life the total amounts may be as high as 20 to 30 mg. In man, the value of the cadmium biological half-hfe ranges between 10 and 30 years. The kidneys, liver, lung and testes are the critical organs... 

The main routes for cadmium to enter an organism are through the respiratory and digestive tracts. Cadmium is a cumulative poison 5-6% of the total cadmium intake through the digestive tract is absorbed while the rest is eliminated in faeces. About 90% of resorbed cadmium is bound to particular proteins (metallothionein) and deposited in liver, kidneys, bones and spleen (Lehman and Poisner, 1984). Excretion of cadmium is a very slow process and amounts to 0.01% of daily body deposit, and its biological half-life is 10-30 years. 

Absorption of increased with increased selenium levels in the meal, particularly in rats fed intrinsically labeled lettuce leaves. Neither the source of Cd nor the selenium level in the meal affected the biological half-life of ° Cd. The biological half-life of cadmium is extremely long, and there is no known way to reverse the damage due to this element. 

Cadmium is a highly cumulative toxin with a biological half-life exceeding 10 years in man. It accumulates in the organism with age, particularly in the liver and in the kidneys, which contain about 50% of the amount stored in the organism (Friberg et al. 1979). 

The excretion of cadmium via the urine and feces is very low in normal human beings and the biological half-life is probably between 10 and 30 yr for the total body. ... 

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