This 2010 book, edited by Olle Selinus, Robert B. Finkelman, Jose A. Centeno is part part of a series that will be a legacy to the International Year of Planet Earth, focuses on earth and health, or, as this subject is commonly referred to, medical geology. Medical geology is the science dealing with the relationship between natural geological factors and health in man and animals. It does not deal with pure anthropogenic factors. There is, however, a gray zone. The arsenic catastrophe in Bangladesh is caused by geology factors (naturally occurring arsenic in the groundwater); however, the health problem was triggered by constructing millions of water wells to bring this water to the surface.
Mining also brings ores and minerals from depth to the surface environment. Unfortunately, there are often serious health consequences caused by oxidation of the ores, liberation of the minerals, etc. Organic pollutants are generally not an issue for medical geology because they are usually anthropogenic; however, there are serious health problems when these compounds are transported by groundwater and deposited in soils. Geoscientists and the information they generate can have important roles to play even in these ‘gray zones.’
Medical geology is a rapidly expanding field concerned with the relationship between natural geological factors and human and animal health, including understanding the influence of environmental factors on the geographical distribution of health problems. Medical geology brings together geoscientists and medical/public health researchers to address health problems caused or exacerbated by geological materials; ultimately, it is only with multidisciplinary collaborations that interventions can be devised to reduce morbidity and mortality from such problems. Medical geology also deals with the many health benefits of geologic materials and processes.
Rocks are composed of the chemical elements found on the earth. Many elements in the right quantities are essential for plant, animal, and human health. Most of these elements enter the human body via food and water in the diet and through the air that we breathe. Through weathering processes, rocks break down to form soils on which crops and animals that constitute the food supply are raised. Drinking water from groundwater moves through rocks and soils as part of the hydrological cycle. Much of the natural dust and some of the gases present in the atmosphere are the result of geological processes.
Elements that are essential for our well-being and non-elements, some potentially toxic, exist side-by-side in bedrock or soils and may become a direct risk
for human and animal health if present in low quantities (deficiency) or if present in excessive quantities (toxicity). The inability of the environment to provide the correct chemical balance can lead to serious health problems. The links between environment and health are particularly important for subsistence populations that are heavily dependent on the local environment for their food supply. Trace element deficiencies in crops and animals are commonplace over large areas of the world and mineral supplementation programs are widely practiced in agriculture.
Infectious diseases in humans are also dramatically affected by the geological environment, albeit indirectly. Geological forces shape the environments in which microbes thrive, sometimes creating opportunities for the emergence of infectious diseases as major public health problems. Because of the emergence of these health problems, there has been a growing awareness of the interaction between the natural environment and animal and human health for the past several decades – medical geology. More and more people in developed and developing countries are becoming aware of the potential health impacts caused by geologic processes along with human activities of all kinds that redistribute elements and minerals from sites where they are harmless to places where they adversely impact animal and human health.
Medical geology issues transcend political boundaries, and many issues are found in countries around the globe putting at risk the health of billions of people. A few examples will be mentioned here.
Arsenic in drinking water is one example of international concern. Millions of people in Bangladesh and West Bengal, India, suffer from exposure to high arsenic levels in drinking water. Also millions of people in many countries on other continents are suffering from arsenic exposure or are at risk of arsenic poisoning, a potentially fatal health problem.
High fluorine content in drinking water is another medical geology issue causing problems with teeth and limbs all over the world. Fluorides are ubiquitous in nature and are present in rocks, soil, water, plants, foods, and even air. Excessive ingestion of fluoride through water, food, or dust causes acute toxicity or a debilitating disease called ‘fluorosis.’ Chronic fluoride poisoning is more common and can affect animals as well as humans. Excessive intake during pre-eruptive stage of teeth leads to dental fluorosis and further continued ingestion over years and decades causes bony or
skeletal fluorosis.
Iodine deficiency resulting in health problems, such as goiter, affects many millions of people and is a consequence of the local geology, deficiency of the element iodine in bedrock and soils and thus a deficiency of iodine in the diet.
Selenium is an essential trace element. However, selenium deficiency (due to soils low in selenium) has been shown to cause severe physiological impairment and organ damage. Several areas in the world have been demonstrated to have soils deficient in selenium. Selenium deficiency is particularly prevalent in China.
Geology is the most important factor controlling the source and distribution of radon. Relatively high levels of radon emissions are associated with particular types of bedrock and unconsolidated deposits, for example, some, but not all, granites, phosphatic rocks, and shales rich in organic materials. Inhalation of radon was a severe occupational hazard for uranium miners, commonly resulting in fatal lung cancer.
Balkan endemic nephropathy (BEN), an irreversible kidney disease associated with renal pelvic cancer, was thought to be confined to several rural regions of the Balkans, but recently it has been discovered in other parts of the world by medical geology scientists.
Atmospheric dust is a global phenomenon. Dust storms from Africa regularly reach the European Alps and the Western Hemisphere. Asian dust can reach
California in less than a week, some of the dust ultimately crossing the Atlantic and reaching Europe. The ways in which mineral dust impacts upon life and health are wide ranging. These include changes in the planet’s radiative balance, transport of disease bacteria to densely populated regions, dumping of wind-blown sediment on pristine coral reefs, general reduction of air quality, provision of essential nutrients to tropical rainforests, and transport of toxic substances. Mobilization of dust is both a natural and an anthropogenically triggered process.
This book will cover all these aspects and many more, on a global and regional scale. Many specialists from all around the globe have contributed with their expertise. The book gives many examples of environmental health issues from different continents and also an overview of what is going on now in the field of medical geology. A truly international book like this also reflects the different scientific cultures from all around the world with different terminologies and different ways of thinking. The readers must bear this in mind when reading the book.
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