Cadmium local contamination

Soil plays an integral part in our lives and is inherently linked to public health. For example, many of the essential trace elements which we require in our diet to remain healthy are derived from soils and parent rock material, and low concentrations or the unavailability of these elements in soil can cause dietary deficiencies. Soils can also be contaminated with a range of potentially hazardous substances (both chemical and biological) which, if present at sufficiently elevated levels, can present a potential public health problem. For example, soils may contain elevated levels of heavy metals such as cadmium and lead which can have measurable and often severe effects on local populations. The soils of Cappadocia in central Turkey are naturally rich in fibrous asbestos-like minerals that are thought to be the cause of a rare cancer in local communities1 while exposure to the bacterium Clostridium tetani in soils can cause tetanus. Despite such examples, the effects of contaminated land have, until recently, been relatively ignored and, even today, our understanding of the mechanisms and level of risk associated with contaminated land is poor in relation to air and water. 

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. 

This is what happened in the Jinzu River basin as locally grown rice became contaminated with cadmium. Dietary exposure was high as rice was the staple diet of most local people and as a result of chronic exposure to cadmium in the diet many began to suffer bone disease and abnormalities of calcium metabolism and kidney problems, a condition that known locally as itai-itai disease (literally translated as ouch ouch ).38 This disease became most apparent during and immediately after the Second World War with elderly women, particularly women who had given birth to several children, most affected. During this period, food was scarce and the diets of local people became extremely heavily dependent on rice. In addition, the scarcity of food meant that the diet of many people was also deficient in calcium, vitamin D and protein. These factors exacerbated the toxicity of cadmium, and in a relatively small area over two hundred elderly women were severely affected, many of whom eventually died as a result of this condition. It has since been estimated that people in the Jinzu River basin had a... 

Ryan JA, Zhang P, Hesterberg DA, Chou J, Sayers DE (2001) Formation of chloropyromorphite in lead-contaminated soil amended with hydroxyapatite. Environ Sci Technol 35 3798-3803 Sadoc A, Lagarde P, Vlaic G (1985) EXAFS evidence for local order in aqueous solutions of cadmium bromide. JPhys C 18 23-31... 

A proportion of the atmospheric content of trace elements produced in urban areas must be deposited in areas downwind, so that there must also be a general background of contamination at a much lower level in soils in rural areas in industrialised and densely- populated countries. Some fallout can also be expected in nearby seas of even in other countries beyond, and Tyler [167] states that the high concentrations of cadmium and lead in the moss carpets of southern Norway and south-western Sweden, reflect an atmospheric deposition ofithese elements transported from remote sources, probably from continental Europe and the UK. Fallout from atmospheric pollution into the sea is unlikely to produce high local concentrations of any potentially toxic element. Dispersion of trace elements in the environment by this particular route is more efficient than by any other and no pollution problems have been reported as having arisen in this way. 

The striking effects of cadmium toxicity in Japan arising from increased uptake of cadmium in locally-consumed rice grown in paddy fields irrigated with cadmium-contaminated river water have already been mentioned. The disorder involved was essentially an osteomalacia, associated with kidney damage and proteinuria, affecting villagers who were dependent on the rice crop as a main source of food. 

An increased risk of osteoporosis correlates with the cadmium burden in different populations, especially for post-menopausal women. Cadmium exposure decreases bone mineral density and thus increases the risk for fractures. These effects on the bones are related to kidney malfunction and poor calcium reabsorption in the nephron, as witnessed by (hyper)calciuria. The consequences of cadmium exposure on the human skeleton were particularly obvious for Japanese living along the Jinzu river basin in the 20th century. Water and rice contaminated by cadmium as a result of zinc-mining activities upstream afflicted the local people with the Itai-Itai disease, a particularly acute and painful form of osteomalacia [44]. 

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