Heavy metal toxicity - metabolism, absorption, distribution, excretion and mechanism of toxicity for each of the metals
Languages of publication
The main threats to human health from heavy metals are associated with exposure to lead, cadmium, mercury and arsenic. These metals have been extensively studied and their effects on human health regularly reviewed by international bodies such as the WHO. Heavy metals have been used by humans for thousands of years. Although several adverse health effects of heavy metals have been known for a long time, exposure to heavy metals continues, and is even increasing in some parts of the world, in particular, in less developed countries. However, over the last 100 years, emissions have declined in most developed countries. Cadmium compounds, the exception, are currently mainly used in re-chargeable nickel-cadmium batteries. Cadmium emissions have increased dramatically during the 20th century, one reason being that cadmium-containing products are rarely re-cycled, but often dumped together with household waste. Cigarette smoking is a major source of cadmium exposure. In non-smokers, food is the most important source of cadmium exposure. Recent data indicate that adverse health effects of cadmium exposure may occur at lower exposure levels than previously anticipated, primarily in the form of kidney damage, but possibly also in bone effects and fractures. Many individuals in Europe already exceed the recommended exposure levels and the margin is very narrow for large groups. Therefore, measures should be taken to reduce cadmium exposure in the general population in order to minimize the risk of adverse health effects. The general population is primarily exposed to mercury via food, fish being a major source of methyl mercury exposure, as is dental amalgam. The general population, however, does not face a significant health risk from methyl mercury, although certain groups with high fish consumption may attain blood levels associated with a low risk of neurological damage to adults. Since there is a risk to the fetus in particular, pregnant women should avoid a high intake of certain fish, such as shark, swordfish and tuna; fish (such as pike, walleye and bass) taken from polluted fresh waters should especially be avoided. There has been a debate on the safety of dental amalgams and claims have been made that mercury from amalgam may cause a variety of diseases. However, there are no studies so far that have been able to show any associations between amalgam fillings and ill health. The general population is exposed to lead from air and food in roughly equal proportions. During the last century, lead emissions to ambient air caused considerable pollution, mainly due to lead emissions from petrol. Children are particularly susceptible to lead exposure due to high gastrointestinal uptake and the permeable blood-brain barrier. Blood levels in children should be reduced below the levels so far considered acceptable as recent data indicates that lead may hold neurotoxic effects at lower levels of exposure than previously anticipated. Although lead in petrol has dramatically decreased over the last decades, thereby reducing environmental exposure, phasing out any remaining uses of lead additives in motor fuels should be encouraged. The use of lead-based paints should also be abandoned, and lead should not be used in food containers. In particular, the public should be aware of glazed food containers, which may leach lead into food. Exposure to arsenic is mainly via intake of food and drinking water, food being the most important source in most populations. Long-term exposure to arsenic in drinking water is mainly related to increased risks of skin cancer, but also enhanced risk of some other cancers, as well as other skin lesions such as hyperkeratosis and pigmentation changes. Occupational exposure to arsenic, primarily by inhalation, is causally associated with lung cancer. Clear exposure-response relationships and high risks have been observed.
-  P. Atkins and L. Jones. Chemistry—Molecules, Matter and Change, 3rd ed., W. H. Freeman, New York (1997).
-  K. F. Heuman. Chem. Eng. News, May 2, 1902/2 (1955).
-  B. E. Davies. Hydrobiologia, 49, 213 (1987).
-  J. J. R. Frausto da Silva and R. J. P. Williams. Struct. Bonding 29, 67 (1976).
-  C. D. Foy, R. L. Chaney, M. C. White. Ann. Rev. Plant Physiol. 29, 511 (1978).
-  R. J. Puddephatt. The Periodic Table of the Elements, Oxford University Press, Oxford (1972).
-  N. Lewis. Valence and the Structure of Molecules, The Chemical Catalogue Company, New York (1923).
-  S. Ahrland, J. Chatt, N. R. Davies. Q. Rev. Chem. Soc. 12, 265 (1958).
-  R. G. Pearson. J. Chem. Educ. 45, 581 (1968).
-  R. G. Pearson. J. Chem. Educ. 45, 643 (1968).
-  R. G. Pearson. Surv. Prog. Chem. 5, 1-52 (1969).
-  Faure. Principles and Applications of Inorganic Geochemistry, Macmillan, New York (1991).
-  E. Huheey. Inorganic Chemistry: Principles of Structure and Reactivity, Harper & Row, New York (1975).
-  G. Klopman. Generalized perturbation theory of chemical reactivity, in Chemical Reactivity and Reaction Paths, G. Klopman (Ed.), Wiley, New York (1974).
-  G. Klopman. Environ. Health Perspect. 61, 269 (1985).
-  J. R. Frausto da Silva and R. J. P. Williams. The Biological Chemistry of the Elements: The Inorganic Chemistry of Life, Oxford University Press, Oxford (1993).
-  Veith, J. A. and G. Sposito. 1977. On the use of the Langmuir equation in the interpretation of adsorption phenomena. Soil Sci. Soc. Am. J. 41: 697-702.
-  Woolson, E. A. 1977. Fate of arsenicals in different environmental substrate. Environ. Health Perpect. 19: 7381.
-  Woolson, E. A. 1977. Generation of allsylarsines from soil. Weed Sci. 25: 412416.
-  Woolson, E. A., J. H. Axley and P. C. Kearney. 1971. The chemistry and phytotoxicity of arsenic in soils. I contaminated field soils. Soil Sci. Soc. Am. Proc. 35: 938943.
-  Zachara, J. M., D. C. Girvin, R. L. Schmidt and C. T. Resch. 1987. Chromate adsorption on amorphous iron oxyhydroxide in presence of major ground water ions. Environ. Sci. Technol. 21: 589-594.
-  Zarchara, J. M., C. C. Ainsworth, C. E. Cowan and C. T. Resch. 1989. Adsorption of chromate by subsurface soil horizons. Soil Sci. Soc. Am. J. 53: 418-428.
-  Zarchara, J. M., C. E. Cowan, R. L. Schmidt and C. C. Ainsworth. 1988. Chromate adsorption on kaolinite. Clays Clay Miner. 36: 317-326.
-  Zasoski, R. J. and R. G. Burau. 1988. Sorption and sorptive interaction of cadmium and zinc on hydrous manganese oxide. Soil Sci. Soc. Am. J. 52: 81-87.
-  McBride, M. B. 1980. Chemisorption of Cd2+ on calcite surfaces. Soil Sci. Soc. Am. J. 44: 26-28.
-  McBride, M. B. 1982. Hydrolysis and dehydration reactions of exchangeable Cu2+ on hectorite. Clays Clay Miner. 30: 200-206.
-  McBride, M. B. 1985. Sorption of copper(II) on aluminum hydroxide as affected by phosphate. Soil Sci. Soc. Am. J. 49: 843-846.
-  McBride, M. B. and J. J. Blasiak. 1979. Zinc and copper solubility as a function of pH in an acidic soil. Soil Sci. Soc. Am. J. 43: 866-870.
-  McBride, M. B. and D. R. Bouldin. 1984. Long-term reactions of copper(II) in a contaminated calcareous soil. Soil Sci. Soc. Am. J. 48: 56059.
-  McLaren, R. G. and D. V. Crawford. 1973. Studies on soil copper: II. the specific adsorption of copper by soils. J. Soil Sci. 24: 443-452.
-  McNeal, J. M. and L. S. Balistrieri. 1989. Geochemistry and occurrence of selenium: an overview. In L. W. Jacobs (Ed.). Selenium in agriculture and the environment. American Society of Agronomy. Madison, WI.
-  Miller, W. P., D. C. Martens and L. W. Zelazny. 1986. Effect of sequence in extraction of trace metals from soils. Soil Sci. Soc. Am. J. 50:598-601.
-  Harter, R. D. 1979. Adsorption of copper and lead by Ap and B2 horizons of several northeastern United States soils. Soil Sci. Soc. Am. J. 43: 679-683.
-  Harter, R. D. 1983. Effect soil pH on adsorption of lead, copper, zinc, and nickel. Soil Sci. Soc. Am. J. 47: 47-51.
-  Harter, R. D. 1984. Curve-fit errors in Langmuir adsorption maxima. Soil Sci. Soc. Am. J. 48:749-752.
-  Harter, R. D. and D. E. Baker. 1977. Application and misapplication of the Langmuir equation to soil adsorption phenomena. Soil Sci. Soc. Am. J. 41:10771080.
-  Harter, R. D. and R. G. Lehmann. 1983. Use of kinetics for the study of exchange reactions in soils. Soil Sci. Soc. Am. J. 47:666-669.
-  Harter, R. D. and G. Smith. 1981. Langmuir equation and alternative methods of studying "adsorption" reactions in soils. In R. H. Dowdy, J. A. Ryan, V. V. Volk, and D. E. Baker (Eds.). Chemistry in the soil environment. American Society of Agronomy. Madison, WI.
-  Hendrickson, L. L. and R. B. Corey. 1981. Effect of equilibrium metal concentration on apparent selectivity coefficients of soil complexes. Soil Sci. 131: 163-171.
-  Hickey, M. G. and J. A. Kittrick. 1984. Chemical partitioning of cadmium, copper, nickel, and zinc in soils and sediments containing high levels of heavy metals. J. Environ. Qual. 13: 372-376.
-  Hingston, F. J., A. M. Posner, and J. P. Quick. 1971. Competitive adsorption of negatively charged ligands on oxide surfaces. Faraday Soc. 52: 334-342.
Publication order reference