Editorial—Introducing a special theme issue on medical geology

Medical Geology—Impacts of the natural environment on human health

In the last few decades, there has been a growing awareness that some natural environmental changes occur on a scale that affects global ecologies: atmospheric, hydrogeological, and food production systems worldwide have been transformed in ways that sometimes leads to the emergence (and/or re-emergence) of health problems in humans and animals. Although it has been recognized that natural geological factors play key roles in a range of environmental health issues that impact the health and well-being of billions of people worldwide (Fig. 1), there is a general lack of understanding of the importance of these factors on human and animal health among the general public, the biomedical/public health community and the geosciences/environmental community. Medical geology—the science that deals with the impacts of natural geologic materials and processes on animal and human health¹—attempts to bridge this gap by increasing the awareness of these issues between the geoscientist, environmental and biomedical communities, and by stimulating increased research collaboration among these disciplines. Medical geologists are a group of scientists that are primarily interested in outbreaks of disease in which the characteristics of the local geological constituents contribute to the occurrence of various disease states. For the most part, diseases of interest have often included the effects of deficiency or toxicity of a variety of metallic elements on various systemic organs. Scientists have studied the long-term effects of exposure to oncogenic elements, the most prominent example being arsenic.

Fig. 1 Range of health issues associated with natural geological materials and processes. Trace elements play an essential role in the normal metabolism and physiological functions of animals and humans. The association between geologic materials and trace element deficiency is well documented for elements such as iodine (iodine deficiency disorders) and selenium, while excess exposure to trace and toxic elements such as arsenic, fluorine and mercury have also being documented. Exposure to natural dust (including volcanic emissions and mining) can cause a wide range of respiratory problems and organ related damage such as black-lung disease and silicosis. (Courtesy of Robert B. Finkelman, Olle Selinus and Jose A. Centeno).

Thus, medical geology may be considered as a complementary discipline to the established field of environmental health focusing on how the natural environment impacts health. These impacts, both deleterious and beneficial, have been known for millennia but it is just in the last decade that scientists interested in these phenomena have begun to organize local, regional and global collaborations in this emerging discipline of medical geology.

Medical geologists are scientists (geoscientists, biomedical/public health scientists, chemists, toxicologists, epidemiologists, hydrologists, geographers, etc.) who generally collaborate on a wide range of environmental health problems seeking causes and solutions (Fig. 2). Among these problems are the health impacts of geogenic (natural) dusts, naturally occurring elements in surface water, ground water and soil, geologic processes such as volcanoes, erosions, earthquakes, tsunamis, etc., occupational exposure to natural materials and natural radiation. Many medical geology studies have been focused on the health impacts of dust from various origins. Dust particles are a widely dispersed component of the Earth's atmosphere, often forming extensive plumes that derive from volcanoes, dust storms, long-range transport episodes of desert dust (the so called intercontinental dust; Fig. 3), and displacement through natural processes such as landslide and earthquakes. These phenomena occur on all major continents, including mobilization of Saharan dust to southern Europe and the Americas (Fig. 3).

Fig. 2 As a multidisciplinary field, medical geology requires the interaction among geosciences, medicine, and geography to characterize the sources of natural environmental contaminants and their impact on human and animal health.

Fig. 3 This satellite image shows a dust cloud from North Africa moving across the Atlantic Ocean, over northern South America and then over the Caribbean and the southern U.S. These dust storms occur several times a year resulting in increased incidence of asthma and allergies in the Caribbean region. There is growing evidence that this type of dust may also be able to mobilize a wide range of pathogens and microorganisms affecting human and animal health. (Courtesy of U.S. NASA.)

Medical geologists study the source, occurrence, distribution, concentration, chemistry, crystallinity and morphology of minerals (such as asbestos, erionite, silica, pyrite) that may cause health problems. Medical geologists try to determine the sources, transport and fate of potentially harmful trace elements such as arsenic, fluorine, selenium, copper and other metals. They try to determine the pathways of exposure and produce maps that illustrate local, regional and/or global geologic and geochemical factors and their relationship to existing or potential health problems. A good example of collaborative research on medical geology is the arsenic issue in Bangladesh and West Bengal, India. In this region, medical geologists are working together to determine the source of the high arsenic levels in well water that put at risk the health of up to 100 million people in this region.

On its 10^th Anniversary, the Journal of Environmental Monitoring (JEM) marks an important step in the growth and maturation of medical geology. The two reviews in this theme issue of JEM by Jardine et al. on the study of mosquito-borne disease as an environmental monitoring tool in tropical ecosystems; and by Harper on asbestos, respectively, are only two of many articles which the journal is anticipating publishing. The publication of these manuscripts in JEM is a further demonstration that medical geology is taking strong root in the international arena and that biomedical/health professionals and geoscientists will soon be demonstrating its value to the global society. On behalf of the International Medical Geology Association and its worldwide membership, I would like to congratulate JEM for its vision and interest in the field of Medical Geology, and wish it many more years of success in continuing to publish outstanding work.

References

1. Essentials of Medical Geology—Impacts of the Natural Environment on Public Health, ed. O. Sellinus, B. Alloway, J. A. Centeno, R. B. Finkelman, R. Fuge, U. Lindh and P. Smedley, Elsevier, New York, 2005, 812 pp.

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