Cadmium human exposure

Vahter M (1982) Assessment of human exposure to lead and cadmium through biological monitoring. Natl Swed Inst Environ Med, Stockholm. 

Council Regulation 315/93 lays down Community procedures for establishing maximum limits for contaminants (other than pesticide and veterinary drug residues) in food. The Scientific Committee for Food must be consulted on all questions which may have an effect on public health and this committee carries out the toxicological evaluations which underpin the limits set for contaminants. The scientific data which form the basis of the evaluations are obtained mainly from the scientific literature and from the Member States. Data on human exposure to contaminants, such as nitrates, cadmium, aflatoxins and ochratoxin A, have been collected and collated in projects in the programme on scientific co-operation between the Member States (known as SCOOP). 

Dangerous levels of human exposure from diet have occurred, most notably in Fuchu, in northern Japan where rice was eaten that was contaminated with cadmium derived from an old zinc mine and present in soil and water. Low calcium intake and vitamin D deficiency may also have been factors. The victims suffered from brittle bones, and it became known as itai-itai disease from the Japanese for ouch-ouch (see box). The village of Shipham in Somerset was, similarly, found to have very high levels of cadmium in the soil, which also derived from an old zinc mine. 

The first observations on adverse renal effects of cadmium (Cd) exposure in humans were made by Friberg in the late 1940s [1]. He reported a high prevalence of proteinuria (65% using the nitric acid test and 81% using the trichloroacetic acid test) in Cd-exposed workers. 

The primary routes of potential human exposure to coke oven emissions are inhalation and dermal contact. Occupational exposure to coke oven emissions may occur for those workers in the aluminum, steel, graphite, electrical, and construction industries. Coke oven emissions can have a deleterious effect on human health. Coke oven emissions contain literally several thousand compounds, several of which are known carcinogens and/or cocarcinogens including polycyclic organic matter from coal tar pitch volatiles, jS-naphthylamine, benzene, arsenic, beryllium, cadmium, chromate, lead, nickel subsulfide, nitric oxide, and sulfur dioxide. Most regulatory attention has been paid to coal tar pitch volatiles. 

Thallium is a by-product of iron, cadmium, and zinc refining. It is used in metal alloys, imitation jewelry, optical lenses, artists pigments, semiconductors, ceramics, and X-ray detection devices. It has limited use as a catalyst in organic chemistry. In the past, thallium (chiefly thallium sulfate) was used as a ro-denticide and insecticide. Its use as a rodenticide was outlawed in 1965 due to its severe toxicity (a source of accidental and suicidal human exposures). Medicinally, it has been used as a depilatory and in the treatment of venereal disease, skin fungal infections, and tuberculosis. 

The diet is the major route of human exposure to cadmium. Contamination of foods with cadmium results from its presence in soil and water. Concentrations of cadmium in foods range widely, and the highest average concentrations are found in mollusks, kidneys, livers, cereals, cocoa, and leafy vegetables. A daily intake of about 60 [tg would be required to reach a concentration of 50 mg/kg in the renal cortex of persons 50 years of age, assuming an absorption ratio of 5%. About 10% of the absorbed daily dose is rapidly excreted (WHO, 1989, 2001). 

Jinzu Valley, Japan. One of the most infamous cases of contaminated land and health occurred in Japan and the effects were most prominent immediately after the Second World War. Around the end of the 19th century, soils in the Jinzu River basin, part of the Toyama prefecture, became contaminated with cadmium as a result of activities upstream at the Kamioka mines. The main activity at this mine was the mining and processing of zinc (cadmium is often associated with zinc ores) with the result that wastewater rich in heavy metals was discharged into the Jinzu River. Contaminants from this industry moved down-stream and caused contamination of soils in paddy fields as a result of abstraction of river water into fields in order to cultivate the local rice crop. Under favourable conditions, cadmium can be a fairly mobile heavy metal, particularly in soils with low pH, and increases in soil cadmium can often result in an increase in the uptake of cadmium by plants. This in turn results in an increase in dietary exposure and the consumption of contaminated agricultural crops can be a major pathway of human exposure. 

Monitoring human food and the evaluation of daily dietary intake of toxic metals is a part of international efforts to assess the integral human exposure to various pollutants. The greatest attention is presently paid to lead, cadmium and mercury. They are released continuously into the environment, and tho efore, reflect increasing levels in human food. 

Vahter, M., and Slorach, S., Exposure Monitoring of Lead and Cadmium. An international pilot study within the WHOlUNEP Human Exposure Assessment Location (HEAL) Programme. Technical Report. Global Environment Monitoring System. WHO and UNEP, Nairobi, 1990, pp. 1-82. 

Vahter, M., (Ed.), Assessment of Human Exposure to Lead and Cadmium through Biological Monitoring, Global Environmental Monitoring System (GEMS), National Swedish Institute of Environmental Medicine and Karolinska Institute, Stockholm, 1982, pp. 1-136. 

Hutton M (1982) Cadmium in the European Community a prospective assessment of sources, human exposure and environmental impact. Monitoring and Assessment Research Centre, Chelsea College, University of London, London, UK MARC Report No. 26. 

Vahter M and Sloragh S (1991) Exposure monitoring of lead and cadmium. An international pilot study within the UNEP/WHO human exposure assessment location (HEAL) project. Technical Report, WHO, Nairobi, 82 pp. 

Vahter, M. and Friberg, L. (1988) Quality control in integrated human exposure monitoring of lead and cadmium, Fresenius J. Anal. Chem. 332, 726. 

In general, the information about the environmental pollution and human exposure to cadmium in the Central European countries is very limited. 

Human exposure to high concentrations of cadmium are rare and current concern centers around the chronic toxicity caused by long-term exposure to low levels of the metal. Bone disorders are one manifestation of chronic cadmium exposure. Cadmium is present in all tissues of adults, with the most significant amounts found in the liver and kidney, and the concentrations tend to increase with age. The WHO regards a tolerable daily intake of cadmium to be 70pgd for an adult of 70 kg. 

Metals Induce Cancer When Administered to Experimental Animals. Again, the reader is referred to many recent comprehensive reviews which discuss the evidence that certain metals cause cancer in experimental animals (9,10,J1). The most credible data implicates cadmium, chromium, co 6 a TT, and nickel as carcinogens in experimental animals. It should be noted that while arsenic has been shown to be responsible for the induction of human cancer, attempts to induce cancer in experimental animals with arsenic and its compounds have not been successful. In contrast, while cobalt induced cancer in experimental animals, numerous epidemiological studies have failed to show a correlation between excessive human exposure to cobalt and the induction of human neoplasia. One of the most studied metal carcinogens are the nickel compounds, of which crystalline Ni3 2 appears to be the most potent (1,2,12). Ni3 2 has been shown to induce cancer at... 

Figure 1 Relative importance of the various cadmium sources to human exposure.

Chronic experiments using combined exposures to multiple carcinogenic metals, such as would occur most frequently in human exposures (Waalkes and Oberdorster 1990), have not been carried out with cadmium. However, cadmium can both enhance and antagonize the carcinogenic effects of several organic carcinogens (Harrison and Heath 1986 Kurokawa et al. 1985 Wade et al. 1987 Waalkes et al. 1991c). The incidence of diethyl-... 

Human exposure mainly arises from combustion of fuels, plants, and waste, and consumption of adventitious cadmium present in food and water [83]. Humans and animals breathe cadmium-containing particles (mainly the oxide) and ingest cadmium complexes with their food and drinks. Cigarette smoking is a major route of uptake, whereas skin contact is not widespread owing to the natural dilution of cadmium, except for occupational settings. Dietary cadmium is more concentrated in some food items such as shellfish, offal, grains, and seeds. Some crops, such as rice, soybeans, or wheat, are more likely to accumulate cadmium firom polluted soils than others. 

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