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 Asia show some people with thick necks, and other who appear to be retarded. Indeed, geochemical data coupled with epidemiological studies have shown that insufficient iodine in the diet, especially in early childhood and during development, causes goiter and cretinism. (The addition of iodized salt or iodine-enhanced cooking oil to food can ease this shortfall. There are, however, populations at risk in midcontinent China and in Sri Lanka in spite of the identification of the symptoms, the geological association, and the relative simplicity of correcting the deficit.)

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 Minimata, Japan, where industrial mercury compounds were discharged into Minimata Bay and taken up by fish that were eventually eaten by humans. The resulting poisoning and deaths in Japan became a major concern, and alerted investigators to look for mercury in other environments.

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 Bangladesh were diagnosed in the 1980s and confirmed in the 1990s as being related to intake of elevated amounts of arsenic. The arsenic was present in water, used for domestic purposes and irrigation, from shallow wells that had been dug increasingly since the 1970s. The people not only drank the arsenic-contaminated water but also grew their vegetables and fed their animals with plants containing it. The ingestion of high levels of arsenic over many months and years led to dermatologic lesions and death, symptoms which continue to this day. This human disaster began rather innocently with the wish to provide the population with pure (microorganism-free) ground water rather than contaminated surface water (from cisterns), but the arsenic level of the wells was not tested. With hindsight it can be said that integration of hydrological information for this basin environment should have been obtained before the wells were dug.

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.

زمین شناسی پزشکی(دارویی)-زمین شناسی پزشکی(دارویی)-زمین شناسی پزشکی(دارویی).د