Probably not since the Second World War has one issue dominated the daily lives of so many in the way the Covid-19 pandemic has done in this past year or so.
Probably not since the Second World War has one issue dominated the daily lives of so many in the way the Covid-19 pandemic has done in this past year or so. The geoscience community like many other professional groups has been peculiarly helpless in coming up with any science-based contribution to mitigating or analysing the crisis. Not that there were any expectations.
Full marks, therefore, to researchers at the University of Leicester’s Centre for Palaeobiology. They have had the presence of mind to look ahead instead, asking whether in geological ages to come the pandemic will leave any detectable sign of its occurrence. One morbid conclusion is that human fossils are unlikely to provide much clue, because Covid victims will likely be difficult to distinguish from any other cause of death.
On the other hand, the spike in potential ‘technofossils’ in the form of disposable face masks and gloves may will find their way into the geological cycle. As the researchers point out, these items are plastic-based, durable and therefore easily fossilized. They speculate that relatively intact gloves and masks may accumulate in river beds or at the bottom of lakes and, as they are covered with sediment, will fossilize into newly formed rocks. Of course much of this medical detritus will be carried into the oceans and end up washed on beaches around the world, quite probably to be recycled back into the sea via waste disposable. Material could also find its way to mid-ocean so-called plastic islands to eventually degrade into the countless billions of microplastic fragments drifting down into deep-sea muds.
The Leicester study, described as a thought experiment, concludes that for Covid to be set in stone, so to speak, it would be if the pandemic acted ‘as a catalyst to change society’s planetary impact, such as by decarbonizing industry across the world.’ Then rock strata might signal whether the Anthropocene intensified or instead deflected away from its current ‘Hothouse Earth’ direction. Even so, a few geological ages from now, it would be hard to identify the cause of this transition as a global pandemic.
Not directly related to Covid considerations, there actually has been a growing confluence between geoscience and the medical field. Increasing interest in the inter-disciplinary study of the relationships between geo-environmental factors and the health of plants, animals and humans has given rise to a new discipline. It might easily have been stunted at birth if early advocates had stuck with the original scientific term for this discipline, namely hydrobiogeochemoepidemiopathoecology. Luckily they settled for medical geology. What apparently started as a few geochemists in the 1960s trying to decipher potential links between the natural geochemical environment and the health of people living in a particular area led to the establishment in 2006 of the International Medical Geology Association IMGA). Its website provides a good clue to its mission quoting Paracelsus, the Renaissance era Swiss physician (1493-1541) – ‘All substances are poisons; there is none which is not a poison. Only the dose differentiates a poison and a remedy.’ In Geologica Acta, 5 (3), 2007, Bunnell et al., authors who were prime movers in the early days of IMGA, outlined five principal goals: 1) To identify geochemical anomalies in soils, sediments, and water that may adversely impact human and animal health; 2) To identify the environmental causes of known health problems and, in collaboration with bio- medical/public health researchers, seek solutions to prevent or minimize these problems; 3) To evaluate the beneficial health effects of geologic materials and process; 4) To reassure the public when there are unwarranted environmental health concerns associated with geologic materials or processes; and 5) To forge links between developed and developing countries to find solutions for environmental health problems.
The authors suggested that, among other environmental health problems, geologists and the medical community could collaborate on exposure to natural dust and to radioactivity; exposure to toxic levels of trace essential and non-essential elements such as arsenic and mercury; nutrient trace element deficiencies; naturally occurring toxic organic and inorganic compounds in drinking water; identification and effects of volcanic emissions, etc. They stated that geoscientists could join the party as they offer an array of tools and databases that can be used by the environmental health community to study vector-borne diseases, to model the dispersion of pollutants in surface and ground water and in the air, plus have applications for occupational health problems resulting from exposure to minerals.
Medical geology should not be confused with medical geography. This looks at the geographical distribution of disease while not focusing on the underlying geology, but some overlap in this multi-disciplinary science seems inevitable. IMGA admits the field of study is complex. For example, on its website it highlights a study in Iran (to be found in the Journal of Agricultural Science and Food) under the somewhat uninviting title of ‘The Medical Geology and Discovery of Taranjebin Manna as a Hyper Selenium Accumulator; Biomedical and Ethno-Medical Efficacy Links to Calc-alkaline and Alkalic Tethyan Magmatic Arcs’. This turns out to be a fascinating validation of the assumed to be beneficial selenium content of a gum exudate giving it a high ethno-medical demand in Iran as well as proving an export business.
A more accessible reference to medical geology studies can be located in the Medical Geology Impacts of the Natural Environment on Public Health, edited by Jose A Centeno, Robert B. Finkelman and Olle Selinus. This 2016 open access volume was originally published as a special issue of Geosciences in 2014, and provides plenty of illustrations of what medical geology has to offer in practice.
There are chapters on anthrax and the geochemistry of soils in the US; inhalation of airborne arsenic from mining operations; risk factors of E.coli 0157 and Cryptosporidiosis infection (not good) in individuals in the Karst valleys of East Tennessee; geogenic contaminants in water co-produced with coal seam gas extraction in Queensland, Australia; a Portuguese case study of heavy metal and hazard materials exposure at the Panasqueira mine; environmental risk assessment of potentially toxic elements sampled on stream sediments of Santiago, Cape Verde; legacy of uranium development around US Indian reservations; geogenic trace elements from Danish drinking water; health risks of uranium in home water wells; and impact of artisanal and small-scale gold mining on environment and human health in a region of Indonesia.
For those wondering, engineers also get a look into the emerging area of medical geology. In the 2016 January issue of International Journal of Health Geographics, a wide ranging review of medical geology challenges, Maged N. Kamel Boulos and Jennifer le Blond describe how an article in the IMGA newsletter entitled ‘Geomedical engineering: a new and captivating prospect’ by A. Ur-Rehman formalized the idea of applying engineering practice principles to medical geology issues.
Last but not least we come to geophysics and medicine where there has been a longstanding affinity. Here Crosstalk willingly pays tribute to the late Prof Larry Lines (1949-2019), charismatic geophysics professor at the University of Calgary, Alberta, Canada.In his last years he contributed some notable thoughts on the symbiosis between geophysics and medicine. In a CREWES Research Report (Vol. 30, 2018) he described geophysical and medical imaging as operations conducted prior to more invasive procedures - geophysical imaging ahead of costly drilling and medical imaging to inform before potential surgical intervention. He rather mischievously noted that in both cases the imaging was targeting anomalies but with different expectations. Anomalies found in the geophysical context could lead to a positive outcome, while we don’t want to find anomalies in the human body that may point to a malign condition.
Lines drew comparisons between seismic tomography, of which he was an authority, and the computer-aided tomography of CT scans in the medical field. He said that ‘instead of evaluating travel times as in seismic tomography, the CT experiment deals with the decays of X-ray multiples in propagation through the human body’. CTs (using a Fournier method) require a full 3600 scanning of the object, not applicable to geophysical tomography where Lines wrote that sources and receivers are on the Earth’s surface or in boreholes so that the aperture scan is restricted to much less than 3600.
With reference to electromagnetic imaging of the Earth and the body, Lines notes that GPR imaging of the near surface is valid at depths of a few metres but for EM imaging of the human body, the wavelengths involved are typically of the order of a few centimetres. This is why high frequency EM waves (microwaves) are used with frequencies in the order of 1-10 GHz. He cites an apparatus for measuring microwave transmissions to estimate dielectric properties of the human breast to detect possible tumours, and suggests this method could improve medical tomography imaging.
Meanwhile the closest similarity to reflection seismology in medical imaging is ultrasound imaging, according to the review review. Seismic reflection imaging uses the same principle as ultrasound while operating at much lower frequencies (ultrasound waves have frequencies greater than 20,000 Hz). In both cases improved resolution will occur at high frequencies at the expense of increased attenuation.
Finally, Lines noted that with co-author Joan Embleton he had explored how spinal decompression used as a non-invasive alternative to surgery involves principles very similar to the vibroseis technology deployed in land seismic surveys.
Although Lines expressed optimism about the promise of synergies between geophysicists, electrical engineers and medical imagers, further research is probably not top priority in the current pandemic era. The same applies to medical geology, however valuable the intention.
‘All substances are poisons; there is none which is not a poison…’ (Paracelsus).
‘Engineers also get a look into the emerging area of medical geology.’
