Cadmium critical concentration

Kjellstrom T. Critical organs, critical concentrations, and whole body dose-response relationships, in Cadmium and health a toxicological and epidemiological appraisal. Volume II effects and response. Friberg L, Elinder C-G, Kjellstrom T, Nordberg GF (editors). CRC Press, Boca Raton, Florida 1986 p. 231-246. 

Daily intake of Cd from food is estimated at 35 to 90 /xg. When dietary exposure reaches critical concentrations, estimated to be about 250 to 300 /ug/d, toxicity symptoms are manifested. Cadmium intakes of the Japanese farmers suffering from the widely known "itai-itai" disease were reported to be from 600 to 1000 /xg/d. The disease was caused by ingestion of rice highly contaminated with Cd. The rice paddies received water discharged from upstream Zn mines. Many of the victims died as a result of the disease. 

Ellis, K.J. eta ., Critical Concentrations of Cadmium in Human Renal Cortex Dose Effect Studies to Cadmium Smelter Workers. J. Toxicol. Environ. Health 7 691-703, 1981. (76)... 

Koropatnick J, Leibbrandt M, Cherian MG (1989) Organ-specific metallothionein induction in mice by x-irradiation. Radiat Res 119 356-365 Lehman-McKeeman LD, Kershaw WC, Klaassen CD (1991) Species differences in metallothionein regulation a comparison of the induction of isometallothioneins in rats and mice. In Klaassen CD, Suzuki KT (eds) Metallothionein in biology and medicine, CRC, Boca Raton, pp 121-132 Lui EMK (1987) Metabolism of copper and zinc in the liver and bone of perinatal guinea pig. Comp Biochem Physiol 86 173-183 Maitani T, Cuppage FE, Klaassen CD (1988) Nephrotoxicity of intravenously injected cadmium-metallothionein critical concentration and tolerance. Fund Appl Toxicol 10 98-108... 

Maitani T, Cuppage FE, Klaassen CD (1988) Nephrotoxicity of intravenously injected cadmium-metallothionein critical concentration and tolerance. Fund Appl Toxicol 10 98-108... 

After the critical concentration the conductance of the anion is observed to drop very sharply to zero and to pass into negative values. This is the same type of transport number behaviour as that shown by cadmium iodide (Chapter 2) and indicates that the anions are preferentially transported to the cathode rather than to the anode. It is evident that ion association between anions and positively charged micelles is the cause. Hartley calculated that in cetylpyridinium bromide about 53 bromide ions are associated with each micelle of 68 cationic species to give a net charge of +15. 

Criticality Precautions. The presence of a critical mass of Pu ia a container can result ia a fission chain reaction. Lethal amounts of gamma and neutron radiation are emitted, and a large amount of heat is produced. The assembly can simmer near critical or can make repeated critical excursions. The generation of heat results eventually ia an explosion which destroys the assembly. The quantity of Pu required for a critical mass depends on several factors the form and concentration of the Pu, the geometry of the system, the presence of moderators (water, hydrogen-rich compounds such as polyethylene, cadmium, etc), the proximity of neutron reflectors, the presence of nuclear poisons, and the potential iateraction with neighboring fissile systems (188). As Httle as 509 g of Pu(N02)4 solution at a concentration Pu of 33 g/L ia a spherical container, reflected by an infinite amount of water, is a critical mass (189,190). Evaluation of criticaUty controls is available (32,190). 

Analysis of zinc solutions at the purification stage before electrolysis is critical and several metals present in low concentrations are monitored carefully. Methods vary from plant to plant but are highly specific and usually capable of detecting 0.1 ppm or less. Colorimetric process-control methods are used for cobalt, antimony, and germanium, turbidimetric methods for cadmium and copper. Alternatively, cadmium, cobalt, and copper are determined polarographicaHy, arsenic and antimony by a modified Gutzeit test, and nickel with a dimethylglyoxime spot test. 

Fig. 9-22 a and b). They can be found in the immediate vicinity of the emission source. In a small area (see Tab. 9-10) the concentrations of cadmium exceed the index value of the category B of the Dutch hst [1988] (Tab. 9-11) which implies a need for more detailed investigation. By means of the kriging estimation the critical polluted area can be well assessed. The locations of the concentration maxima enable conclusions to be drawn about the source of emission. The blast furnace works in the north of the Maxhiitte proves to be the main source of iron and cadmium. This also corresponds to the impact of particulate emissions in the territory investigated (see also Fig. 9-19). 

A critical minimum stress exists, below which delayed cracking will not take place. The critical stress decreases with increase in hydrogen concentration. These effects are shown in Figure 6.61 for SAE 4340 steel (0.4% C) charged with hydrogen by cathodic polarization in sulfuric acid, then cadmium plated to help retain hydrogen, and finally... 

Metallothioneins (MTs) are a superfamily of low-molecular-weight (<7000-dalton) intracellular metal-binding proteins, which, in many species, play a critical role in (a) the detoxification of nonessential metals such as Cd2+ and Hg2+ and (b) the regulation of intracellular concentrations of essential metals such as Zn2+ and Cu+. In 1957, Kagi and Vallee first purified and characterized MT as a cadmium-binding protein in equine kidney. 

Checking a method for ruggedness will highlight the main parameters that need to be carefully controlled. For example, in the determination of cadmium release from ceramic ware, acid is added to the item of ceramic ware and left for 24 hours. During this period, the time, temperature and acid concentration will determine the amount of metal leached. Experiments show that temperature is a key parameter (results change by ca. 5% per °C) and it needs to be strictly controlled, e.g. to within +1 °C. Time is far less critical (result changes by ca. 0.3% per hour) and therefore needs to be less strictly controlled, e.g. 0.5 hour. 

A procedure Ls developed to determine the upper critical level of the concentration of heavy metals in plants and solids. Experimentally it has been sliown that the soil type affects the upper critical (phytotoxic) level of zinc (Zn) and cadmium (Cd) for maize and spinach. 

This development is due to various factors, such as high water flow in "wet years" and the effects of the economic crisis, particularly at the end of the 1970 s. However, a significant portion of the reduction should be affected by improvement of wastewater treatment and by the partial replacement of metals in critical applications. It is indicated from these data, that the major decrease for cadmium occurred in the dissolved phases, whereas - until 1979 - the reduction of mercury concentrations mainly took place in the solid phases. This is an indication that equilibria between solid and aqueous phases have not completely established, and clearly shows the difficulties involved in the modeling such processes (see review by Honeyman Santschi, 1988). 

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