زمین شناسی پزشکی(دارویی)
Medical geology
Medical geology, an emerging field
of cooperative research, focuses on the interactions between earth materials and
processes with human and animal health. It links geologists and other earth
scientists with plant and animal biologists, as well as medical, dental, and
veterinary specialists, to resolve local and global health issues.
The basis of medical geology is that
individuals and populations are products of their environment, and their
well-being depends on the intimate impact of their physical and chemical
surroundings. For example, the sources of some diseases, as well as some
beneficial relationships, can be identified by combining information from
environmental geochemistry (the study of the distribution of elements, gases,
and mineral materials in specific geologic/geographic areas) with medical or
dental abnormalities. The combination of such disparate areas of science and
expertise can provide more precise diagnosis of some human disorders and
possibly uncover mechanisms for their treatment. The goal of researchers in this
field is to identify the environmental causes of disease to alleviate human
suffering. For example, Earth scientists with sensitive detection techniques are
engaged in preparing maps on which they can plot the worldwide distribution of
the many elements in soils, water, and plants. As a result, geoscientists,
medical practitioners, and government personnel can now identify potentially
hazardous habitats in a variety of environments.
Nutrition (essential
elements)
The human body regularly requires
over 30 elements in addition to water. Carbon, nitrogen, oxygen, and sulfur are
the basic elements of all the molecules that make up our soft tissues and
organs. Calcium and phosphorus are elements essential to the formation of the
mineral portion of the human skeleton, while sodium, potassium, and magnesium
are necessary for maintaining the chemical balances in the fluids and cells
required for bodily functions. Of the remaining elements, most, such as zinc,
have special roles in the cascade of biochemical processes that take place every
moment of our lives. The source of these elements are the food and fluids we
ingest, which come to us via the agricultural products that grow on the soils
produced by the weathering of rocks. If there are appropriate amounts of all the
elements in the plants, animals, and humans, they have come from the ultimate
source, the geoenvironment, modulated by their bioavailability up the food
chain. There are places, especially in poor countries, where the inhabitants are
not able to obtain the necessary nutrients due to deficiencies in their soil.
A well-known example of the
connection of health and the geological environment involves the element iodine.
Iodine is concentrated and bioavailable in the ocean, and the fish and plants
that live there are good sources of the element. Low iodine concentrations are
typical of mountainous terranes that often contain a complex of igneous and
metamorphic rocks. The minerals typical of these rocks may contain small amounts
of iodine, but the element is usually not readily available (that is, is not
chemically removed from the rock very easily). The soils generated from these
rocks, where the inhabitants grow their grains, are therefore depleted of
iodine. There is an early historical record of disease related to such iodine
deficiency. Chinese screens depicting daily life in the central mountainous
portions of continental
Hazards
The transport and distribution of
earth materials and the geologic processes that control them characterize much
geologic research. Such research can shed light on how medical hazards can be
spread by normal geologic processes.
Airborne
hazards
Noxious gases generated by volcanic
eruptions are airborne hazards obviously related to a normal geologic process.
To mitigate the immediate health impact of volcanic gases, seismic detectors can
be installed in susceptible areas throughout the globe to allow evacuation of
communities when necessary. However, in addition to the immediate gas explosion,
volcanoes generate particles of mineral materials that may become globally
distributed, staying in suspension in the atmosphere for years with possible
health effects that may not be immediate or obvious.
Mineral dusts such as the silica
dusts or loess (sand) generated in arid areas can be significant hazards. In the
past, the problem of blowing sand has had no obvious solution, other than moving
the population. Although there is little opportunity for altering weather
patterns or providing a physical diversion for blowing sand, advances in
technology may succeed in detecting the wind speed that permits fine particles
to become airborne. Plotting the normal track of particle movement and
monitoring changes in areas with airborne particulates could avert future health
problems.
The naturally occurring and
industrially important asbestos minerals pose another potential airborne hazard.
Disease related to asbestos inhalation, usually originating in occupational
settings, may not arise until tens of years after exposure. Because of the
susceptibility of lung disease arising from asbestos exposure, the use of
asbestos has been outlawed and its removal mandated.
In regions of China with
fluoride-rich coal deposits, the indoor burning of this coal for heating,
cooking, and food drying without adequate ventilation has resulted in a high
rate of dental fluorosis among the residents (see illus.). Dental fluorosis, the
observable effect of overexposure to fluoride in childhood when the teeth were
developing, is characterized by discolored (brown-black) or chalky-white teeth.
It is irreversible and no treatment exists.
Waterborne
hazards
The addition of manufactured
chemicals such as phthalates (estrogen disruptors) consumed by individuals and
discharged from sewage treatment plants has caused abnormal shapes and other
unwanted characteristics in the fish in some estuaries. Endocrine disruptors are
newly created chemicals that also make their way into waterways and should be
considered as potential hazards. A classic case of waterborne poison occurred in
1956 in
Many health hazards occur over a
period during which there are few, if any, overt expressions of disease. For
example, skin lesions in a population in
The importance of testing and monitoring water supplies coupled with the coordination of medical and governmental personnel will undoubtedly become much more regularized in the future as a result of the arsenic problem in Bangladesh. We are becoming more appreciative of the dependence of humans on their environment, and have identified a few of the environmental factors that are hazardous to health. Such coordination may also have financial benefits. The methods available for treatment of overexposure to arsenic, especially for large populations, are expensive; the possibility of locating alternative potable water sources through subsurface geological mapping of the aquifer may prove economically preferable in the long term when the health costs are factored in.
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A. G. Darnley et al., A Global Geochemical Database for Environmental and Resource Management: Recommendations for International Geochemical Mapping, Earth Sci. Rep. 19, UNESCO, Paris, 1995
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R. B. Finkelman, H. E. Belkin, and B. Zheng, Health impacts of domestic coal use in China, Proc. Nat. Acad. Sci. USA, 96:3427–3431, 1999
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J. P. Gratton, The toxicology of volcanic gases, their historical impact and their potential role in contempory European environments, in J. Rose (ed.), Environmental Toxicology, pp. 109–120, Gordon Breach, Amsterdam, 1998
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B. S. Hetzel, The Story of Iodine Deficiency, Oxford University Press, Oxford, 1989
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J. Lag, Geomedicine, CRC Press, Boca Raton, FL, 1990
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H. C. W. Skinner, In praise of phosphates or why vertebrates chose apatite to mineralize their skeletal elements, Int. Geol. Rev., 42:232–240, 2000
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H. C. W. Skinner, M. Ross, and C. Frondel, Asbestos and Other Fibrous Materials: Mineralogy, Crystal Chemistry and Health Effects, Oxford University Press, New York, 1988
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