MEDICAL GEOLOGY CLAY

Medical uses of montmorillonite clay
Geology is no longer confined to the study of rocks and minerals. As the field of medical geology becomes better known, the medical community will discover that geology could play a major role in the etiology of a variety of diseases. Uncovering these relationships is an inherently multidisciplinary task. After all, for medical geology and geochemistry to be of use to the public and to health authorities of a given region, all samples from the local environment–that is, rock, soils, water, plants, and food–need to be studied together and correlated with in vivo studies.

In the medical field, too, as discoveries are made in the physiology and metabolism of trace elements, the biochemical mechanisms underlying the body’s absorption and rejection of trace elements, and the cellular mechanisms that regulate these processes, researchers may also find a greater need for the understanding of geology and trace-element geochemistry.
Geology and medical science, disciplines that until now have been considered poles apart, may now find themselves joined into a multidisciplinary framework for unraveling some of nature’s most interesting secrets.

Every day we eat, drink and breathe minerals and trace elements, never giving a thought to what moves from the environment and into our bodies. For most of us this interaction with natural materials is harmless, perhaps even beneficial, supplying us with essential nutrients.  These interactions are the realm of medical geology, a fast-growing field that not only involves geoscientists but also medical, public health, veterinary, agricultural, environmental and biological scientists. Medical geology is the study of the effects of geologic materials and processes on human, animal and plant health, with both good and possibly hazardous results.

The relationship between the Earth’s surface that we humans inhabit and our health is under debate. The fact that a continuum and indelible link exists is not in doubt. We have obtained food, water, and shelter since Homo arrived, but in the twentieth century we have learned that disease as well as health may by derived from our environment.  Certain diseases are attributed to several minerals sensu latu (concept that includes the minerals sensu restrictuconsidered as natural, inorganic and crystalline solids, the so-called oligoelements or trace minerals, the biominerals and mineral resources such as natural mineral water), naturally or humanly derived. Within minerals, clay minerals, the essential constituents of clays, are omnipresent at the earth surface where organisms live, and due to their specific properties they can interact, positively as a rule, with them. Some clay minerals are being used, either as active principles (gastrointestinal protectors, laxatives, antidiarrhoeaics), or as excipients (inert bases, emulsifiers, lubricants) in certain medicines. Also they participate in formulations used for topical applications in both dermopharmacy and dermocosmetics.

The geochemical distribution and biochemical availability of the elements that are required for human existence are not uniformly distributed over the Earth’s surface. For example, low concentrations of iodine (I) characterize the soils and rocks at high elevations and in limestone terrains. This is a natural global phenomenon. Medical acumen and geostatistical and epidemiological investigations have identified iodine as an essential nutrient. The thick necks that were depicted in ancient Chinese scrolls, and the cretinism found in mountainous regions, are now recognized as symptoms of the endemic disease goitre. Jharkhand and other Eastern states in India are a Iodine deficiency zone. Reduction, but unfortunately not eradication, of this preventable malady is now possible through the use of iodine-enriched table salt and oils.

Specific properties of clay minerals such as the nanometer size and thin platy or fibrous shapes, the negative electric charge, and high adsorption and absorption capacities justify the therapeutic uses referred to. Also, these and other properties justify the nuse of clay minerals for improving environmental quality which is fundamental for the living quality of man and other organisms as they can act as catalysts for potentially benign chemical processes. Due to the properties referred to, particularly the surface properties, clay minerals and other colloidal minerals (oxides, hydroxides and oxy-hydroxides of Fe, Mn and Al) constitute environmental factors of paramount importance since they can control the bioavailability, ecological effects, biogeochemical cycles, and distribution of trace metals and metalloids in ecosystems (know heavy metals and metalloids have critically important biological effects, both beneficial and harmful.

According to natural waters and soil solutions can be readily taken up from solution by clay minerals and other colloidal minerals, the efficiency of the phenomenon depending on the properties and concentrations of the reactants and on environmental factors that affect the forms of the Jackson, 1998; Sparks, 2005). As we Jackson (1998)  trace elements in natural waters and soil solutions can be readily taken up from solution by clay minerals and other colloidal minerals, the efficiency of the phenomenon depending on the properties and concentrations of the reactants and on environmental factors that affect the forms of the elements and the surface properties of the colloids.

The process involves:

1) Sorption by clay minerals, oxides and clay–oxide–humic complexes;

 2) Co-precipitation with oxides;

 3) Complexing by organic matter.

Among the clay minerals, montmorillonite and vermiculite are those that exhibit higher adsorption capacities.  In aquatic and terrestrial ecosystems clay minerals and other colloidal minerals can act as sinks and secondary sources of trace metals and metalloids with important biological consequences as they can limit or prevent their uptake and bio-availability by organisms.  The binding and release of trace metals and metalloids by colloidal particles limiting the biological uptake provides the control of the nutritional and toxic effects of the trace metals and metalloids to the benefit or detriment of the organisms.

The surface properties of clay minerals and other colloidal minerals allow them to function as catalysts in many organic reactions (Malla et al., 1991; Sun Kou et al., 1992) and the role on pollution prevention and reduction. For instance, clay-liners have revealed great importance in the case of landfills to avoid migration of toxic metal ions and organic pollutants into neighboring soil, groundwater, and surface water. Also, the use of clay to remove metal ions from wastewater is another important field of application (Sharma et al., 1991; Gupta et al., 1992). A further application is the remediation of polluted environments such as rivers, lakes and lagoons, where toxic metals from both natural and artificial sources become concentrated, either in fine-grained bottom sediments, or in dispersed particulate matter.

Geophagy, the deliberate intake or ingestion of soil or clay by man or other animals (may be to compensate dietary deficiencies), is an old and generalized practice still taking place, these days, in some regions of the world.

“Clay minerals, the most abundant and chemically active components of the surface mineral world, are the key to understanding the links between nature (life), its substrate (essentially silicates), and a mastery of the total ecosystem by man”

The evolution of life from seawater could be supported by the similarity of the compositions of seawater, human body serum, and human red cells, in terms of free cations and anions such as calcium, magnesium, potassium, sodium, chloride, bicarbonate and phosphate (Lindh, 2005).

Clays and clay minerals formed in terrestrial or deepsea vent hydrothermal systems rich in iron and manganese sulfides and unstable silicates, are microcrystalline and have specific properties such as layer charge, high specific surface area, high ion exchange capacity, and high adsorption capacity. They would be the appropriate substrate for bacteria and enzymes. Concerning bacteria, interesting investigations have been carried out on the scientific domain of microbial ecology of hydrothermal systems, on which life on earth could have been initiated.

The relationships between Geology and Biology are the goal of Geobiology, the science that understands the earth as a system, and life as part of it. In space and time, life influences earth development, and earth’s changing environment moulds life (Noffke, 2005).  On the other hand, the interactions between Geology or Geo-sciences and the Ecology are the goal of a scientific area called Geo-ecology, which particularly highlights the interactions between man and the ecosystems.

According to Hazen (2005 a,b), the investigations carried out on the origin of life lead to the conclusion that minerals must have played key roles in virtually every phase of life emergence, catalyzing the synthesis of key biomolecules, and selecting, protecting and concentrating these molecules. They jump-started metabolism, and they may even have acted as first genetic systems.