​Spotlight On Medical Geology

Perhaps you have an interest in geologic matter, and helping people? If so, a career as a medical geologist could be what you're looking for! 

In its broadest sense, medical geology studies exposure to or deficiency of trace elements and minerals; inhalation of ambient and anthropogenic mineral dusts and volcanic emissions; transportation, modification and concentration of organic compounds; and exposure to radionuclides, microbes and pathogens. [http://www.agiweb.org/geotimes/nov01/feature_medgeo.html]

We've observed since ancient times that exposure to some types of soils and rocks cause health problems, some don't have any effect at all, and others are beneficial. Hippocrates for instance noted that water that 'sprung' from soil contaminated with toxic metals was not safe to drink. That was back around 400 BC. In the many decades since Hippocrates, we've encountered a lot more ways in which geographical features of the world we live in influences our health. So much so that eventually we realised we needed a professional who could speak the languages of geology and medicine, and bridge the gap between them. This professional is the medical geologist.

The Evolution Of Medical Geology

In the mid-1900's medical geology was seemingly more about a bunch of geophysicists and other earth scientists communicating with a bunch of doctors and disease experts to try and figure out how certain types of environments and their geologic components and processes affected human and animal health. It was probably adequate at the time, or we believed it was in the absence of much of the cold hard science we rely on today in these matters.

Since those days, there's been an explosion of public interest in health and healthcare generally. There's also been a considerable rise in the global population that is forcing us to expand into, dig up, and exploit previously untouched environments and resources. Likewise, advances in technological gadgetry are driving demand for minerals that were once uneconomical (or unsafe) to dig up. Whilst it may be exciting for those with an adventurous soul, the fact is that the more we're forced to venture into new frontiers the more we risk disturbing and releasing new environmental toxins and other contaminants that were previously dormant.

These issues have all led to increasing interest in the links between geology and health. As a result, medical geology is now a viable study area with courses and degree and graduate programs increasingly available at universities around the world. The list of master's and doctoral research projects on various aspects of medical geology is also increasing, which is probably also testament to the growing importance of this field.

The Earth, And Our Health

Geologic materials (rocks, sediments, dust, volcanic matter), and the earth processes that produce them (weathering, erosion, sedimentation, deposition, volcanic eruptions, earthquakes, plate tectonics) all contain or produce substances that have the potential to affect our health. Dust for example contributes to air pollution and, depending on its source, can contain extremely harmful geologic particulate matter. Likewise, some of the by-products created by our use of geologic materials we've obtained directly from the earth, notably fossil fuels, also contain dangerous contaminants.

The Many Earthly Reasons For Medical Geology

Medical geologists play an important role in helping to identify the types of soils in a particular locality and documenting their associated effects on the surrounding ecosystems. They also document the various mineral imbalances in the soils, and how those imbalances play out when it comes to supporting the accompanying vegetation.

Indeed, how soils are formed and their mineral composition / balance directly affects the plants that grow in them and thus the health of humans and animals that eat the plants.

"….the soil is the predetermining factor of micronutrient levels in any plant. Crops grown in low-quality or deficient soils have lower nutrient content in both shoot and seed. Furthermore, soil type is an identifier of micronutrient deficient populations. " [https://www.ign.org/taking-a-deeper-look.htm]

Here are a few things a medical geologist can tell you about soils, what happens to food chains when soil gets out of whack, and the implications of unhealthy soils for not only our health but also that of other species we share this planet with:
  • Calcium levels – if soil contains too much calcium, it affects the delicate balance between a range of minerals, affecting uptake of these minerals. If it's deficient in calcium, it can lead to plant problems like blossom end rot in susceptible species, notably tomatoes, squashes, and melons (irregular watering also affects calcium uptake). As a case in point, the soils around St Petersburg in Russia are highly alkaline, which makes it difficult to grow (some types of) healthy plants in them. A  recent study looked at how the addition of monosilicic acid could improve the health of cucumbers grown in the soil, notably by boosting iron and manganese uptake. The researchers noted that the improving effect of the monosilicic acid directly correlated with the level of calcium in the soil. This has significant implications for food production in affected areas.
  • Soils high in copper are toxic to plants but copper toxicity is also a serious health issue for most other living things too, including humans! Copper is a heavy metal. It's also an essential one in nutritional terms (amongst other things, it is an integral part of the iron metabolism process). However, excessive copper consumption, from long-term or chronic contact with food and water that contain high levels of the mineral, can lead to kidney failure in severe cases.
  • Soils that are high in molybdenum produce plants that also contain excess amounts of the mineral, causing molybdenum toxicosis in livestock that live off these plants.
  • Plants and animals in humid tropical areas develop characteristics indicative of the low calcium and high iron, silica, and aluminium content of the soils there
  • Whilst many soils around the world are selenium deficient, which causes its own set of health problems, others like black shales and hard coal, can be (very) high in selenium (and arsenic). We do need a small amount of selenium as part of a healthy balanced diet. However, excessive selenium intake causes selenosis. Common symptoms of this disorder include garlicky breath, brittle hair and nails, skin lesions, diarrhoea, rashes, nausea, mottled teeth, abnormal nervous system function, tiredness, and irritability.
  • As for the problems caused by selenium deficiency – the significant ones to look out for are fatigue, mental fog, a weak immune system, hair loss, muscle weakness, and infertility.
  • Black shale is a proven natural environmental contaminant, made worse by humans digging it up! It leaches into surrounding soil and water systems, causing high concentrations of minerals like Cu, Mn, Ni, Zn, Se, As, Cd etc. Plants then accumulate these minerals with associated health consequences for anything that eats them. It's further thought that some diseases and health disorders may be directly linked to black shale contamination.
  • Subclinical magnesium deficiency is a significant cause of cardiovascular disease. Unfortunately, soil erosion and heavy metal contamination have significantly depleted soil magnesium levels in many ecosystems, which means that plants and animals grown in these environments likewise can have suboptimal magnesium levels. We exacerbate this problem with our modern diet full of processed food, much of which has inadvertently undergone magnesium depletion during processing. However, areas where there is still a lot of magnesium in the soil and water, or where magnesium soil deficiencies have been corrected, tend to be associated with fewer deaths from cardiovascular disease.
  • It's estimated that around 30% of the global population suffer from varying degrees of iodine deficiency. Most of the iodine found in soil originates from oceans via the atmosphere but the composition and type of soil influences how well it retains and concentrates the mineral. Some parts of the world have very iodine deficient soils and people who live in these areas notably suffer from higher incidences of Iodine Deficiency Disorder (IDD)


Medical geologists are also good at identifying geological environments per se that will affect human and animal habitation.


They can also work with industry to ensure that geologically sensitive areas with potential to adversely affect human health are either avoided altogether, or treated with the caution and respect they deserve!

  • The desecration of vast areas of soluble rocks (limestone, gypsum, dolomite) can create havoc within the vast underground water systems located in these topographies. For 25% of the world's population, these systems are an integral part of their water supply chain so any drop in quality or quantity is significant.
  • Some areas should not be 'tampered' with because the way the geology is structured makes them prone to catastrophic events like mud flows, rock falls, avalanches and slides, and excessive erosion when subject to anthropogenic activities.


Pollution is nothing but the resources we are not harvesting – R. Buckminster Fuller

  • Certain types of rock structures will release toxic substances ie methane in coal, when disturbed by human activities like mining, quarrying, and excavating.
  • More about coal – contaminants in low-grade coal deposits have been linked to kidney disease in the Balkans whilst emissions from burning the stuff cause all manner of health problems both in humans and in other species. High on the list are mercury and arsenic poisoning, cancer, and increased levels of mercury in seafood.
  • The USGS has studied the potential repercussions on both the environment and human health from organic compounds associated with energy resources, and the impacts of hydraulic fracturing on water quality.

Water and air, the two essential fluids on which all life depends, have become global garbage cans – Jacques-Yves Cousteau.

Medical geologists also know a fair bit about the air we breathe, and the types of disturbances, natural and manmade, that affect its quality. We mentioned methane and coal mining, toxic emissions and coal burning, and radon and seismic movement earlier. Mineral dust is yet another problem, and one we've known about for a long time!

In 1556, Agricola documented the health damage caused by mineral dust in Bohemian mines. Many centuries before him, Hippocrates not only realised copper contaminated water is toxic but that 'metal diggers' often had breathing difficulties. Pliny, who wrote Naturalis Historia, was around in the first half of the 1st century AD and suggested that protective breathing devices should be used to prevent dust inhalation.
  • Most of us know something about mesothelioma, asbestosis and the deadly lung cancers caused by inhaling asbestos dust.
  • Inhaling crystalline silica dust, particularly for long periods, can lead to severe lung scarring aka silicosis. Like many other mineral dust related illnesses, it's incurable (and serious).
  • Long-term inhalation of sand silica can cause a disease called desert lung syndrome.
  • Lead dust from galena is toxic if inhaled or consumed. Unfortunately galena is a major lead ore globally, and also contains silver.
  • Torbernite is typically associated with uranium-containing granites and is a particularly nasty mineral, composed as it is of uranyl, phosphate and hydrated green copper. It is also naturally radioactive and discharges radon. Long-term exposure to radon can cause lung cancer.
  • Siderosis is a condition caused by excess iron deposits in body tissue but it's often associated with pulmonary siderosis (Welder's disease), which is caused by breathing in iron oxide 'dusts' and thus referred to as an environmental disease.
  • Balangeroite is a mineral mined at the Balangero mine at Piedmont in Italy. It shares many similar properties with asbestos but is classified as a distinct mineral in its own right. However, that similarity to asbestos is bad news for people who live and work in and around the mine because it also causes similar health problems.
  • Erionite and fluoro-edenite are other asbestos-like minerals whose dust has similar health effects if breathed in.

Side Note About Air Pollution In General

Today, air pollution is one of the top 5 killers courtesy of respiratory tract disorders like COPD, severe bronchitis, asthma, etc. It's also the #1 environmental one, and accounts for around 7 million deaths a year. The primary causes of air pollution are:
  • Motor vehicles (fumes from fossil fuel combustion engines)
  • Energy generation (smoke and fumes from fossil fuel powered plants)
  • Industrial facilities (smoke and fumes from oil refineries, mines, factories)
  • Waste disposal (smoke and fumes caused by government / agricultural waste incineration)
  • Residential energy use from polluting (fossil) fuels (heating, lighting, cooking etc)

The Etymology Of Medical Geology or How It Came To Get Its Name

'Mederi' is Latin for 'to heal' and is where the modern word 'medical' comes from. 'Ge' is Greek for 'earth' and 'logia' (also Greek) means 'study of'.
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