Cadmium human studies

ATSDR. 1995. Multisite lead and cadmium exposure study with biological markers incorporated. Atlanta, GA U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry. 

HBM values are derived from toxicologic and human studies and are health based (Jakubowski and Trzcinka-Ochocka 2005). Two types of HBM values exist HBM I, the concentration of an environmental toxin in human biological material below which there is no risk of adverse health effects and HBM II, the concentration above which there is an increased risk of adverse health effects in susceptible individuals in the general population (Jakubowski and Trzcinka-Ochocka 2005). An HBM I value serves as an alert level, and an HBM II value is an action level at which immediate efforts should be made to reduce exposure and further clinical examination should follow (Ewers et al. 1999). HBM values and reference values have been derived for a number of chemicals, including lead, cadmium, mercury, pentachlorophenol (PCP), and arsenic. 

Herber, R.F.M. (1992). The World Health Organization study on health effects of exposure to cadmium morbidity studies. In Nordberg, G.F., Herber, R.F.M., and Alessio, L. (Eds.) Cadmium in the human environment. Toxicity and carcinogenicity. International Agency for Research on Cancer, Lyon. lARC Scientific Publications No. 118 p. 347-358. 

Experimental studies have shown that cadmium can induce metallothionein synthesis in the placenta, particularly in trophoblasts. Metallothionein in the placenta binds the essential trace metals, zinc and copper. The mechanism whereby essential metals are preferentially transported to the fetus and cadmium retained is not known. Experimental studies have shown that exposure of pregnant animals to high levels of cadmium early in pregnancy is teratogenic. Human studies suggest maternal cadmium exposure may reduce fetal birth weight and that this may be an indirect effect of zinc deprivation that occurs with cadmium exposure. 

Cadmium (Cd) anode cells are at present manufactured based on nickel-cadmium, silver-cadmium, and mercury-cadmium couples. Thus wastewater streams from cadmium-based battery industries carry toxic metals cadmium, nickel, silver, and mercury, of which Cd is regarded the most hazardous. It is estimated that globally, manufacturing activities add about 3-10 times more Cd to the atmosphere than from natural resources such as forest fire and volcanic emissions. As a matter of fact, some studies have shown that NiCd batteries contribute almost 80% of cadmium to the environment,4,23 while the atmosphere is contaminated when cadmium is smelted and released as vapor into the atmosphere4 Consequently, terrestrial, aquatic, and atmospheric environments become contaminated with cadmium and remain reservoirs for human cadmium poisoning. 

The information available regarding the association of occupational exposure to lead with increased cancer risk is generally limited in its usefulness because the actual compound(s) of lead, the route(s) of exposure, and level(s) of lead to which the workers were exposed were often not reported. Furthermore, potential for exposure to other chemicals including arsenic, cadmium, and antimony occurred, particularly in lead smelters, and smoking was a possible confounder (Cooper 1976 IARC 1987). These studies, therefore, are not sufficient to determine the carcinogenicity of lead in humans, and the following discussion is restricted to the most comprehensive of these studies. 

An in vitro study demonstrated that cadmium and zinc have an antagonistic effect on the inhibitory effects of lead on human ALAD activity (Davis and Avram 1978). Cadmium was 40-100 times more potent than zinc in activating ALAD. Furthermore, the combined effects of cadmium and lead in tissue resulted in an additively increased risk of mortality related to cardiac failure in humans with significant relation to age in 80% of the cases (Voors et al. 1982). 

Laboratory studies with mice and rats have conclusively demonstrated that the injection of cadmium metal or salts causes malignancies (sarcoma) at the site of injection and testicular tumors. However, the simultaneous administration of zinc is protective against sarcoma and interstitial cell tumor development (USEPA 1980). In rats, no dose-related increases in tumors were found at maximum oral daily doses of 4.4 mg Cd/kg BW (USPHS 1993). Among humans, the available epidemiological evidence is not sufficient to conclude that cadmium is definitely implicated as a carcinogen (USEPA 1980 Nomiyama 1982), although cadmium exposure is associated with lung cancer in humans (Shimada et al. 1998). 

To protect humans and other mammals, proposed air-quality criteria range from 0.01 to less than 1.0 mg/m3 for metallic nickel and slightly soluble nickel compounds, 0.015-0.5 mg/m3 for water soluble nickel compounds, and 0.005 to 0.7 mg/m3 for nickel carbonyl (Table 6.10). Inhalation of nickel subsulfide concentrations (0.11 to 1.8 mg Ni/m3) near the current threshold limit value of 1 mg Ni/m3 can produce detrimental changes in the respiratory tract of rats after only a few days of exposure (Benson et al. 1995). Additional animal studies are recommended to identify minimally effective inhalation exposure levels for the various nickel compounds (USPHS 1993). Continued monitoring of nickel refining, nickel-cadmium battery manufacture, and nickel powder metallurgy installations is recommended because ambient air levels of bioavailable nickel at these... 

An EC study has found that cadmium pigments present no significant threat to human health or the environment, says the International Cadmium Association. In view of the positive life cycle assessment, EC Member States voted earlier this year that there should be no further restrictions on the marketing and use of cadmium pigments in plastics. INTERNATIONAL CADMIUM ASSOCIATION... 

In rat developmental studies, fetal effects including delayed ossification and decreased locomotor activity occurred at doses that also caused maternal toxicity. Cadmium sulfate injected into the lingual vein of female hamsters on day 8 of pregnancy caused a high incidence of resorption and malformed offspring. Acute necrosis of rat testes followed large doses orally or parenterally, but testicular effects have not been reported thus far in humans." ... 

The two clusters differ in their metal-binding properties. Mammalian Cd, Zn metallothionein contains four Cd ions in cluster A and two Cd ions and one Zn ion in cluster B. 1157,1159 Calf liver metallothionein contains three Cu ions in cluster B with Cd-displaceable zinc ions in cluster A.1160 Studies on the binding of zinc and cadmium to human liver metallothionein show that binding occurs first in cooperative fashion to cluster A, followed by cooperative binding to cluster B. Incubation of the 7Cd metallothionein resulted in loss of Cd ions from cluster B initially.1161... 

Mertz DP, Koschnick R, Wilk G, et al. 1968. [Studies on the metabolism of trace elements in humans. I. Serum values for cobalt, nickel, silver, cadmium, chromium, molybdenum, manganese],... 

The results of studies on animals show that cadmium is an extremely toxic metal. Cadmium is poorly excreted by the human body and although only 5-10% of that ingested is absorbed, it does accumulate in the body over time with renal damage being caused by long-term exposure.14 One sign of this damage is proteinuria (the appearance of increased levels of unaltered proteins in the... 

The impact to health has been mostly dependent on the concentration of the candidate metal. Some metals (e.g., mercury, lead, arsenic, cadmium, iron, copper) ultimately find their way into human systems via soil, minerals, and water. Studies have shown the presence of many metals in daily consumable products (e.g., food, fruits, milk, fabric materials, drinking water). Further, heavy metals associated with particle material can be accumulated in areas suitable for sedimentation or particle concentration (e.g., upstream from sills or dams, in estuary sludge clog, etc.). These accumulation areas are creating possible pollution sources, as particles pooled could be resuspended during punctual hydrologic periods (floods, drains). Bioavailability, and therefore toxicity of heavy metals, is strongly bound to the current chemical form. 

Several studies indicate that different methods cause adverse effects to embryonic and fetal tissues and eventually lead to the development of teratogenic effects. Metals are omnipresent in the living environment. A variety of anthropogenic activities (e.g., smelting metallic ore, industrial and metal fabrication, commercial application, burning of fossil fuels) have caused adverse effects to the developing fetus. In fact, notorious elements, such as cadmium, lead, and mercury, have been associated with injury and malformation to the growing embryo and fetus of animals and humans.65... 

Field and laboratory studies were conducted to determine the levels of Cd, Pb, and HCBD in various samples collected from a swamp environment in Louisiana and to assess the toxicities of As, Cd, and Hg to two species of aquatic organisms (bluegills and crawfish) indigenous to this swamp [18]. Cadmium and Pb were present in almost all collected samples. Their concentrations in fish were below the action levels set by EPA for the protection of human health. However, hazardous levels of these two elements were found in samples of crawfish, vegetation, soil, sediment, and water to some extent. Low levels of HCBD were recorded in water and sediment samples. In bioassay studies, Hg was found to be the most toxic metal, while As was the least toxic. Between the two test organisms, blue-gills appeared to be more sensitive than crawfish. Mixtures of Cd with As or Hg resulted in a combined toxic effect which was simply additive. However, a synergistic effect was recorded with the mixtures of As and Hg. 

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