Geological setting can have significant health effects on human, animal and plant life, writes Nicolaas C. Steenkamp. Photos by Leon Louw
Medical Geology is the study of the effect the geological setting potentially has on human, animal and plant life. The most common interaction studied is broadly related to elements absorbed by plants or dissolved in potable water, and their positive or negative interaction.
The second relates to natural events where there is usually a short but intense effect of the environment on the life in the immediate area. The main areas of interest relate to the identification and characterisation of natural and anthropogenic sources of harmful material into the environment. The aim is to predict the movement and alteration of geochemical or other agents over time and space, and find ways to minimise the effect or exposure.
The oldest records recognising the environmental effects on humans date to around 2400 BCE by Hippocrates, and in 300 BCE Aristotle established the source and symptoms of lead poisoning. The use of various minerals to treat maladies by alchemists during the Middle Ages is also recorded in treating the plague, smallpox and fever. The addition of minerals to soils for agricultural purposes and to increase crop yields and size has been in practice for more than 6000 years.
The importance of trace elements
Humans and livestock need a variety of trace elements for physical and mental development. The most important trace elements are calcium, magnesium, iron, zinc, selenium and iodine. Deficiency of some trace elements leads to developmental problems, such as skeletal deformation or under-development, a wide range of immune diseases and even cognitive issues.
Excessive amounts of these same trace elements may in turn lead to some medical conditions. For instance, excessive fluorine can lead to fluorosis and has possible links to kidney stones. Toxic trace elements such as chrome, titanium, nickel and cobalt are known carcinogens, responsible for cancers and several other illnesses, mental disorders and even death. Mercury used by hatters during the classical period resulted in mercury poisoning and the manifestation of mental disorders, which led to the term “mad as a hatter”.
The ingestion of toxic trace elements through food or treatment of food is another source. A well-known example is from the Guizhou Province in China where low-grade coal is used in drying of chilli peppers and corn. Arsenic is released in the smoke and absorbed by the chilli peppers and corn. The coal has been found to contain up to 35 000 ppm arsenic. The typical symptoms of arsenic poisoning include hyperpigmentation (flushed appearance, freckles), hyperkeratosis (scaly lesions on the skin, generally concentrated on the hands and feet), Bowen’s disease (dark, horny, pre-cancerous lesions of the skin), and squamous cell carcinoma.
Arsenic poisoning via drinking water has also been reported and studied in the Jharkhand state of India. Some crops are prone to absorbing heavy metals form the soil they are cultivated in. The high levels of mercury in some fish species, such as Pacific tuna, have been documented and affect communities that have a high raw fish diet.
Dangers of mining
Medical problems related to mining activities are well known in South Africa and relate mainly to historic mining practices prior to the introduction of mine health and safety codes. Lung diseases, such as silicosis, asbestosis and black lung are prevalent among older generations of miners.
Silicosis is indicated to be the result of inhaling fine silicate particles, mostly in gold mines over a prolonged period. Black lung, in turn, is due to the prolonged exposure and inhalation of fine coal dust. Asbestosis can be contracted by miners, but also by communities that live in the vicinity of abandoned asbestos dumps.
Huge strides have been made in remediation and rehabilitation of these dumps and the mining of asbestos has been completely halted in most parts of the world. Radon has also been linked to some lung cancers, but studies have not been able to find an empirical connection. Uranium in natural occurrence has very little effect and forms part of the natural background radiation. However, once mined and concentrated in tailings, the fine dust increases the concentration inhaled and may affect kidney, brain, liver and heart systems.
Artisanal miners making use of mercury amalgamation are also exposed to mercury fumes. Fine residue dumps and tailings dumps with high sulphide content have been linked to Acid Mine Drainage (AMD) that affects ground and surface water.
Millions have been spent in treatment and remedial actions in areas that have been affected by AMD. The potential use of fracking in the Karoo has also led to concerns about its effect on groundwater quality and its potential effect on humans and livestock. In most cases a baseline study of ailments that affect a community is performed. This would, in theory, give an indication of any increases in certain diseases or conditions in a particular area that could be linked to mining or related activities.
The use and quality of food grade salt is the best-known example of how government and health authorities have recognised the effects of what is essentially medical geology. It has long been recognised that communities that live far from the sea and have a general low intake of fish, are more likely to suffer from thyroid problems, such as the development of goitres. This led to the mandatory enrichment of table salt with iodine to curb the problem.
On the other hand, the more ready availability of table salt has led to an increase in hypertension, resulting in more programmes to limit the daily intake of salt in the developed and developing worlds. Food grade salt is also highly regulated in terms of quality and subject to SANS standards in South Africa, to mention one example.
Another example is the addition of fluorine to drinking water. Fluorine is added to drinking water to minimise the development of dental caries and starve off osteoporosis.
There is also a medical condition called geophagy, defined as the voluntary consumption of earth materials, mostly clays or soils as a result of some nutritional deficiency. The most common is the consumption of termite mounds as part of some African meals. There is, however, some proven medical value, such as small amounts of kaolinite clay for stomach ailments, which is even included in commercial anti-diarrheal oral treatments.
There are also a number of superstitions surrounding the use of fossils and crystals. There have been reports of fossils being ground up and used by traditional healers for a variety of ailments. Alternative health practitioners have also in the last couple of decades used crystals as part of their treatment regimen.
Living in the vicinity of a volcano has both direct and indirect impacts. The obvious impact is during the active period, when there is exposure to toxic gases, most notably suffocation due to carbon dioxide and ash. The volcanic soils are rich and very attractive from an agricultural perspective, but long-term exposure to volcanic soils may lead to conditions such as podoconiosis, a disease that is linked to the absorption of certain alkaline elements by microphages in the lower limb, causing endothelial swelling that is prevalent in the volcanic areas of Africa where the population walk mostly barefoot.