Medical Geology

To a larger degree than most others, North Americans are shielded from the natural environment. Nevertheless, health problems caused by geologic materials and geologic processes do occur in North America. In contrast to the acute health problems caused by the geologic environment in developing countries, in North America these health concerns are more likely to be chronic, caused by long-term, low-level exposures. Among the potential health concerns that have received public health attention are exposure to trace elements such as fluorine, arsenic, and radon; exposure to natural mineral dusts; occupational and community exposures to trace elements; and ingestion of naturally occurring organic compounds in drinking water. This chapter provides North American examples of each of these environmental health problems and suggestions how the earth sciences can be an integral part of multi-disciplinary teams working to mitigate these problems.

High levels of geogenic cadmium (Cd) have been found in some soils of Jamaica, particularly in the central part of the island. The potential health impact on residents who consumed foods grown on these soils was determined. The foods which have shown the greatest affinity for Cd uptake are mainly green leafy vegetables, tubers and root vegetables. Diet studies showed that some residents are at risk of ingesting Cd in excess of the 7 μg/kg body weight PTWI established by the WHO. Cd exposure and proximal tubular dysfunction were measured as urine Cd (U-Cd) and β₂-microglobulin (β₂-MG) in urine, respectively. Mean U-Cd and β₂-MG concentrations of 4.6 μg Cd/g_cr and 290 μg/g_cr confirm that the population is being exposed to elevated Cd levels and there is evidence of very mild tubular proteinuria. The proteinuria detected in the population was related to Cd exposure, evidenced by the relationship between U-Cd and β₂-MG. While positive results were obtained for the identification of Cd-related renal biomarkers in the study population and there was a clear association between U-Cd and β₂-MG, the absolute concentrations obtained were well below critical limits for the onset of acute or chronic renal effects. Women typically ingested less Cd than men but absorbed greater amounts than males in the same cohort groups.

An overview of the occurrence, concentrations, and possible sources of toxic elements released by geogenic processes that may threat the health of millions of people of Mexico, Central America, and the Caribbean is presented. The geology and tectonic characteristics of Mexico and Central America constitute an appropriate environment for the presence of arsenic and fluoride in groundwater of many zones of the area. Health problems linked with As-tainted water consumption have been documented in Mexico and Nicaragua where epidemiological and toxicological studies have been developed. Fluorosis has been recognized mainly in the central and northern part of Mexico and also in Antigua, Puerto Rico, and Trinidad. Specific health effects resulting from exposure to natural dust transported from Africa have been identified in the Caribbean. Radon exposure may also affect the population living in volcanic and active tectonic environments. However, this problem has only been studied by some researchers, mainly in Mexico and Nicaragua. Collaboration among research groups and authorities has been scarce. The review presented here, although not exhaustive, shows the urgency for increasing that collaboration specially to identify polluted areas, sources, and health effects, of the routine collection and analysis of arsenic and fluoride in all potable water sources of the area, and of developing short-term measures to decrease their concentrations to safe levels.

“Earth and Health” or medical geology has been promoted worldwide as one of the fundamental themes of the International Year of Planet Earth (2007–2009). This was in response to relevant achievements noted in this new field of applied science from the time of the IGCP 454 project which led to foundation of the International Medical Geology Association (IMGA) in 2004. In association with international movements, several academic, professional, and student groups in South America began to study medical geology which started with scientific meetings held in Chile, Brazil, and Uruguay in 2002 and 2003. In this chapter, an attempt is made to describe South American scientists’ relevant contributions to various subjects such as arsenic, lead, mercury, and selenium as well as fluorine and environmental problems affecting different parts of the continent. Some societal issues arising from medical geology studies are also highlighted from the point of view of the international risk communication and risk governance debate and the pioneering ethnographic descriptions of geophagy in the Andean and Amazonian countries. Finally, some ongoing medical geology projects in South America are identified as inspiring initiatives that may encourage future educational and research activities in this science field.

Australia and Oceania together make up some of the oldest and youngest geologic formations on the planet, ranging from rocks dating back to 4,400 million years to newly formed volcanic isles in the Pacific. The health issues related to these diverse geological materials range from those derived from exposure to metals and minerals to volcanic emissions including gas and ash, bushfires, dust storms, as well as health threats posed by natural hazards. With the position of a large part of this region within the Ring of Fire, many Australian and Oceanian lives are impacted upon by the forces related to tectonic movement, including earthquakes, tsunamis, and volcanic eruptions. There are also a number of medical geology issues related to the soil in this area. These include geophagy, melioidosis – an infectious disease caused by soil bacteria, and the impacts from ecosystem transformations caused by the disturbance of acid sulfate soils. An example of this is the increase of vector-borne mosquitoes carrying the Ross River virus with the formation of acidic ponds through acid sulfate soil oxidation. The potential adverse health outcomes from disturbing some parts of the land have long been acknowledged by traditional Aboriginal landowners of Australia, who refer to an area particularly rich in uranium and other metals as Sickness Country.

The Middle East region has reported some endemic diseases which are more prominent than in other parts of the world and in some cases have been seen only in this region. This chapter provides information and addresses various cases from all over the Middle East.

The Middle East is well known for its arid and semi-arid environment with frequent and severe dust- and sand storms. This has affected human health in the southern provinces of Iran like the southwestern Khuzestan Province and the southeastern Sistan and Baluchistan Provinces. Health effects of dust storms in Khuzestan Province include asthma in some cities, especially for people with chronic respiratory and cardiovascular diseases. In spite of the fact that dust and sand storms endanger the lives of over 3 million of Khuzestan Province inhabitants, no detailed studies exist on the nature, type, and health effects of wind-blown dust and sand. Also, two main regions in Iraq including Baghdad and Al-Basra are stricken frequently by dust and sand storms, but little attention has been paid to study the health impact of dust and sand storms in Iraq. This section shows health impacts of dust storms in four case studies.

Numerous examples from all over the Middle East are illustrated on element toxicities such as arsenic and fluorine and deficiencies, especially iodine deficiency. This chapter emphasizes health problems resulting from arsenic toxicities in the region and shows cases of the long-existing iodine deficiency disorders in the Middle East.

Several areas from the Middle East face high natural fluoride levels in drinking water. The levels of natural fluoride in drinking water of up to 3 mg l⁻¹ were found in the Negev Desert region in Israel. In some parts of Saudi Arabia like Hail region a strong association is seen between fluoride levels in well water used for drinking and the severity of dental fluorosis. Mecca was also reported to be an area with endemic fluorosis. There are also some cities in Iran where high levels of fluoride in drinking water account for incidence of fluorosis.

The relationship between radon exposure and health effects in the Middle East is also described. Many epidemiological studies have shown a relationship between radon exposure and lung cancer. Case–control studies have also been carried out in Ramsar in northern Iran indicating inverse relationship between residential radon exposure and lung cancer.

Geophagia associated with iron and zinc deficiency, short stature, delayed sexual maturity, hepatosplenomegaly, and delayed bone age is reported from Middle East countries. This includes Shiraz in Iran, parts of Saudi Arabia, and Arab children from Gaza Strip.

The tropical terrains of the Indian subcontinent and the neighbouring regions provide some of the best examples in medical geology where the impact of the geosphere on human health is markedly seen. The life styles of millions of people in these regions are such that there is a very close and intimate association between the rocks, minerals, soils, water and the human population. The case studies described in this chapter, as illustrated from India, Pakistan, Sri Lanka, Bangladesh and Nepal, notably on fluorides, iodine deficiency disorders (IDD), arsenic pollution, selenium-based health issues among others, demonstrate this close geochemical interaction. The problem of contamination of groundwater by arsenic in Bangladesh and West Bengal, termed as one of the world’s largest environmental disasters, as discussed in this chapter typifies the dangers that could threaten countries and extremely large populations, when geochemistry of the environment and the associated medical geology are not properly understood and neglected. The negative impact of such gross neglect will be seen for many years to come and in Bangladesh and West Bengal for many future generations.

A large body of evidence points to significant health effects resulting from our interactions with the physical environment and we continue to recognise connections between geological materials and processes and human and animal disease. In Africa, these relationships have been observed for many years, but only recently have any real attempts been made to formalise their study. Africa is a continent with a diverse geography, characterised by a range of altitudes, a peculiar hydrological network created in part by the formation of the Great Rift Valley on the eastern flank and arid lands typified by the Sahara and the Mega Kalahari. Volcanic activity accompanying rifting and formation of most of the highlands and mountains has released various trace elements, mostly above background levels, into the environment. A unique distribution pattern of these elements has developed in more recent geological times, following pronounced separation due to extreme tropical conditions of weathering, leaching and eluviation. It is therefore possible to delineate large areas of the continent containing element deficiencies or toxicities, which are closely related to the local geology and/or geographical location. In a region where rural communities are still largely dependent on water and food sources that are locally derived, the above setting provides an attractive opportunity for studying the influence of geochemical factors on the distribution of diseases in man and animals. This pursuit constitutes a large part of the study of the rapidly emerging science of “medical geology”.

According to this definition, the influence of the indoor environment, for example in factories and offices, thus falls outside the scope of medical geology and comes within the area of occupational medicine. To attain completeness in the present review, however, industrially derived exposure to known toxic elements (originating from mining or ore processing, such as are contained in mineral dust, for instance) is also briefly considered. Of the elements for which there are proven or suspected direct causal relationships with man’s health, significant data exist for fluorine, iodine, silicon, arsenic and certain trace metals (both micronutrients and potentially harmful elements). The reader is presented with a summary of available information including current hypotheses and an illustration of why improved understanding of these relationships, based on interdisciplinary studies, would lead to better diagnoses and therapy.

Systematic and regular epidemiological studies on endemic diseases and the natural environment in Russia and NIS are scarce and sporadic. However, there have been some studies of the links between health of the population and the geological background. Information on fluorine, iodine, arsenic, selenium, and other elements’ behavior in natural environment and their effect on human health is presented in this chapter and is the first attempt to synthesize the interdisciplinary knowledge on some geological factors which affect human health in Russia and NIS. Also anthropogenic factors are mentioned, however, of geological origin.

Currently, the most important areas of the study in the field of Medical Geology in Russia – NIS are This chapter, written by leading experts of Russia and NIS, will be of interest to a wide audience of geologists, geochemists, physicians, as well as historians.

Medical geology or earth and health has a long history in Europe. Also the newer development of medical geology has a firm base in Europe. Health problems associated with geologic material and geologic processes occur quite frequently in Europe. The problems associated with the geologic environment in Europe are generally chronic, caused by long-term, low-level exposures. Examples are exposure to trace elements such as fluorine, arsenic, radon, mineral dust and naturally occurring organic compounds in drinking water. The chapter provides the history of medical geology in Europe, many examples of these environmental health problems and a look into the future.

The impact of the natural environment on human health has been a subject of study in China for at least 5,000 years. China’s varied geology and geography and its large population living off the land have resulted in the presence of virtually every known environmental health problem and some of the most serious medical geology problems. Fluorosis in China has been caused by drinking fluoride-rich waters, burning coal briquettes using fluorine-rich clay binders, and eating high-fluorine salt. Iodine deficiency disorders such as goiter and cretinism were common in central China but the introduction of iodized salt has greatly reduced these health problems. Arsenic poisoning has been widespread in China, mainly caused by drinking arsenic-rich groundwater but burning arsenic-rich coals and metal mining have also contributed to this problem. Selenium deficiency that is believed to be a causative factor in Keshan disease and Kashin-Beck disease was widespread in a zone from northeast China to Tibet. Human selenosis, thallium poisoning, and various respiratory problems caused by exposure to minerals have also been reported from China.

The relationship between medical treatment and geology in Japan has an old history. However, the distribution of man-made strata deserves special mentioning in the geology of the Japanese Archipelago. The population density of Japan is high, and the man-made strata abruptly increased due to consequences of high economic growth, mass production, and mass consumption. Therefore this chapter describes the background and the different methods used in solving environmental problems linked to man-made pollution, the geological environment, and health in Japan.

Geo-pollution in Japan is an anthropogenic subterranean pollution. The geo-pollution does not mean “chemical hazards” caused by geological factors, that is, the distribution of natural elements and constituents and processes. Pollutants from geo-pollution sites are often harmful for health. Therefore geo-pollution is an integrated part of medical geology, studying the effects of our natural environment including the anthropogenic impact and processes in the natural environment.

The large volume and areal extent of metallurgical processing wastes in the Lavrion urban area, and their subsequent movement by aerial and fluvial processes, as well as by human activities resulted in the contamination of overburden materials, including residual and alluvial soil. The bioaccessibility of contaminants, such as Pb and As, is verified by the high concentrations of Pb in blood and deciduous teeth, and As in urine of children and adults alike. The present work, apart from the review of all available data and information, studied in detail every possible aspect of the Lavrion environment, i.e. overburden materials (including residual and alluvial soil), house dust, lithology, metallurgical processing wastes, and produced a multitude of geochemical distribution and other thematic maps, leading to risk assessment and the production of an environmental management plan for the rehabilitation of contaminated surficial materials. Although cost-effective solutions were proposed, no action has as yet been taken by the relevant authorities.