Medicinal mercury in Medieval bones

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  • Published: Jun 1, 2008
  • Author: Steve Down
  • Channels: Base Peak
thumbnail image: Medicinal mercury in Medieval bones

The Middle Ages, often referred to as Medieval times, spanned a long period in history from the 5th to the 16th Centuries. During this time, European society and culture enjoyed many advances and it could be argued that the quality of life improved beyond recognition. One area which progressed steadily was medicine and the treatment of disease, although these days we would not touch some of the medicinal compounds with a bargepole, let alone administer them to patients.

One substance in popular use was mercury, used variously in gilding of jewellery and weapons, in inks and, yes, as medicines. Most Europeans would have had some mercury in their bodies, a lot more than background levels today, but those working with mercury compounds or being treated with them suffered far greater exposure.

Mercury was used to treat diseases with symptoms that manifested themselves on the skin. One such disease was syphilis, which was widespread at the time and was treated by the administration of mercury vapour and a mercury-containing skin tonic. Leprosy was another common disease with skin lesions, so might well have been treated with mercury. This premise has been examined by European scientists who have measured the levels of mercury in human bones from the Medieval period.

Kaare Lund Rasmussen and co-researchers from the University of Southern Denmark in Odense, The Institute of Anthropology, Archaeology and Linguistics in Hojbjerg, and the Christian-Albrechts University in Kiel studied bones that had been interred in Danish cemeteries. Two Franciscan friaries, a Cistercian abbey and a parish churchyard at various locations were examined.

Leprosy and syphilis were each identified by the type of bone lesions observed and a third condition, known as focal osteolytic syndrome that was identified as recently as 1996, was also detected in some of the skeletons. Individual specimens from 12 individuals were radiocarbon dated by gas proportional counting and the more sensitive technique of accelerator mass spectrometry. The ages were adjusted to allow for the effects of diet.

Some people had a large proportion of fish in their diet, such as those living by inland lakes or the sea. Cistercian monks were not supposed to eat four-footed animals, so would also have eaten much fish, along with people who were allegedly fasting but cheated by eating fish. This fish/shellfish diet introduces a "reservoir effect" in the carbon-14 concentrations, for which a correction was made by the research team.

The mercury concentrations in many bones were determined by atomic absorption. Measurements of mercury in the soil surrounding the bones were also carried out to confirm that mercury loss from the bones via diagenesis was not significant.

Typical background mercury levels in individuals exhibiting no sign of disease were about 30-50 ng/g, although individual levels could be affected if the person worked with mercury, as a pharmacist, for instance.

In the syphilis group, six individuals had markedly raised levels of mercury in their bones, from about 150-600 ng/g, which the research team took as evidence of mercury treatment. The other individuals may not have received treatment, so their mercury remained at background levels. This limited study suggests that 40% of the Danish population that were affected with syphilis so severe that it showed up in the bones were administered mercury.

In the leprosy group, a similar argument revealed that 11 out of 14 sufferers (79%) were treated with mercury-containing medicine. The higher incidence of treatment might be linked to the fact that 11 of the individuals were exhumed from a particular Cistercian abbey (in Om) which is known to have been highly educated in medicine.

For the three cases of focal osteolytic syndrome, found at one site, raised mercury levels were not found, indicating that this disease was not treated with mercury, or that the community was too poor to have access to the medicine.

For bones exhumed from the cloister walk of the Om abbey, which were assumed to belong to the monks who lived there, five individuals from a total of 13 tested had elevated levels. This was in direct contrast to cloister bones from a Franciscan friary, which had similar background mercury levels to those of people buried outside in a laymen cemetery.

The team put forward two alternative explanations for the high levels in the Om monks, carefully avoiding the suggestion that they were associated with leprosy or syphilis. The monks may have come into contact with mercury from the red ink that they used on their documents in the scriptorium. More likely, they say, is that they produced and administered mercury-containing medicines in the abbey hospital.

The background levels of mercury in the control groups for syphilis and leprosy were different, at 53 ± 30 and 34 ± 15 ng/g, respectively. The corresponding radiocarbon dates were determined to be later than 1500 and earlier than 1500. The lack of systematic radiocarbon dates of individuals around this period (only 12 subjects were dated) prevented the researchers declaring that mercury levels increased over time but this omission will be addressed by future dating studies.

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.


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