Washington, June 2 : Scientists 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 also examined.
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 that progressed steadily was medicine and the treatment of disease.
One substance in popular use was mercury, used variously in gilding of jewellery and weapons, in inks and 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.
The researchers identified leprosy and syphilis 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.
The mercury concentrations in many bones were determined by atomic absorption.
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.