University Of Tasmania
whole_GillPeterFrancis1977_thesis.pdf (16.53 MB)

The health of workers exposed to cadmium.

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posted on 2023-05-26, 23:50 authored by Gill, Peter Francis
Cadmium has been described as being toxic in all living species. At no level of intake does it appear to have a useful biological function. Although it was not recognised until 1817 as a separate element man has been polluting his environment with it for centuries - from the time the early Greek metallurgist began working with \bronzes\". Widely distributed in the earths crust in low concentrations it remains \"locked in\" unless other more important resources are extracted and refined. Erosion and weathering of the earths crust contributes little to the level of environmental cadmium. In nature it is closely associated with zinc. It is also found in many other polymetallic ores particularly those containing copper and lead. Fossil fuels coal and oil as well as phosphate rock also contain significant quantities of cadmium. When mankind refines and utilises and purifies these materials cadmium is released. It is a relatively unimportant resource a by-product of far more important resources. Whether needed or not it is being separated and recovered in greater quantities annually. Many uses have been found to make it marketable. Little recycling of the end product occurs. Consequently an increasing quantity of \"free\" cadmium is available for contamination of the environment. Water air food chains foodstuffs are providing an increasing load to all living things. It has been claimed it poses a threat to all life on earth. Almost 150 years passed from the time cadmium was recognised to the time it was generally accepted as a dangerous substance. 19th century industry provided many examples of its acute toxicity but it was the mid twentieth century before it was established that the metal could accumulate in the body over many years and ultimately reach a concentration which interfered with the function of the host cell. Those most at risk are those who handle the material in their occupation. But heavy pollution of some Japanese waterways has resulted in death and chronic disability to the population living along the shores. Chronic obstructive airways disease and renal tubular disease are common in those whose working conditions expose them to high concentrations. Anaemia bone disease general malaise have also been found. Animal experimentation has shown that cadmium though poorly absorbed can enter the body via the skin lungs and alimentary canal. Its entry stimulates the formation of a special protein Metallothionein which acts both as a carrier and a receptacle. Cells of many tissues take up cadmium - in particular the liver kidney pancreas gonads salivary and intestinal glands. Because of its environmental ubiquity and its slow excretion - mainly via the kidney lifelong accumulation occurs. How much can the body accumulate before signs of toxicity appear? Just how toxic is it to various organs? I have compared the health of 34 workers at the Electrolytic Zinc Company of Australasia Risdon Tasmania who have spent many years working in a moderately contaminated atmosphere with fellow workers exposed only to environmental cadmium. I restricted my investigation to the clinical field and avoided invasive investigational procedures.. I found no evidence of any serious ill health specific to the exposed group. In particular this group did not manifest any of the disabilities found in similar surveys by others. My group of workers were different in that they were working in levels well below accepted tolerable levels. This group therefore could be used as representatives of a middle group between those environmentally at risk and those seriously at risk because of heavy occupational exposure. I found cadmium did cause chronic pulmonary symptoms even in these low concentrations but without objective pulmonary disease. Some of those with the longest exposure and presumably the largest body burden did show evidence of altered haemoglobin and protein synthesis without obvious clinical manifestations. I found no evidence of any of the conditions - hypertension malignancy endocrine disorders speculatively linked to cadmium by epidemiologists using results of animal studies on environmental studies and disease patterns. Though definitely toxic to cells cadmium can be tolerated up to a certain body burden for a \"no effect\". I was not able to establish this burden but the study may provide areas for further research into this very important question."


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Copyright 1976 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s). Thesis (M.D.)--University of Tasmania, 1977. References: l. 224-229

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