June 27, 2008 -- Medieval bones from six different Danish cemeteries reveal that monks who wrote Biblical texts and other religious materials may have been exposed to toxic mercury, which was used to formulate just one of their ink colors: red.
The study, which will be published in the August issue of the Journal of Archaeological Science, also describes a previously undocumented disease, called FOS, which was like leprosy and caused skull lesions. Additionally, the researchers found that mercury-containing medicine had been administered to 79 percent of the interred individuals with leprosy and 35 percent with syphilis.
Since the monks, who were buried in the cloister walk of the Cistercian Abbey at Øm, did not have these diseases but contained mercury in their bones, scientists believe the monks were either contaminated while preparing and administering medicines, or while writing the artistic letters of incunabula, or pre-1500 A.D. books.
Kaare Lund Rasmussen, a University of Southern Denmark scientist at the Institute of Physics and Chemistry, suspects that ink used in the abbey's scriptorium was the culprit.
He told Discovery News "it is very human to lick the brush, if one wants to make a fine line."
Even today "one should really not touch, or much less rub, the parchment pages of an incunabulum," Lund Rasmussen said, adding that mercury "was used in the first place because cinnabar (a type of mercury) has this bright red, beautiful color."
It is also known that metallic liquid mercury was given in vapor form to diseased patients. So if the monks "were just a little careless, they would be exposed this way, however, they might also be exposed during the preparation of the medicine."
For the study, Lund Rasmussen and his team drilled bone samples from the buried individuals, some of which were also friars buried in the cloister walk of the Franciscan Friary in Svendborg. Unlike the Øm monks, the friars showed no signs of mercury poisoning.
Co-author Jesper Lier Boldsen discovered the previously undocumented disease FOS while examining the skeletons.
"We do not know if FOS was fatal, but it certainly looks painful and just as severe as leprosy," Lund Rasmussen said.
While working on the study, the researchers also noted that, due to different carbon signatures, some of the medieval individuals ate a mostly marine, fish-filled diet. Lund Rasmussen suggests that the others may have "preferred beer and meat, rather than fish and water." The Cistercians were, in principal, not allowed to eat meat from any four-footed animals, but the Franciscans do not appear to have always observed this practice.
Although modern seafood may now contain high levels of mercury from environmental pollution, exposure from food would have been unlikely during the medieval period.
Other religious groups may have experienced mercury poisoning due to scripting holy texts. In a separate study, scientists from the Soreq Nuclear Research Center in Israel and the Israel Museum found cinnabar on four fragments of the Dead Sea Scrolls, which include passages from the Hebrew Bible.
University of Southern Denmark historian Kurt Villads Jensen, who did not work on the latest Danish study, told Discovery News that he believes the medieval mercury findings seem "very convincing" and that he has "absolutely no objections to the historical part of the paper, which is my main research area."
Lund Rasmussen and his team radiocarbon dated some of the studied bones, but they hope to do this for even more individuals from the test sample group, as this could reveal additional information about the possible link between mercury exposure and red ink use. By 1536, books were no longer written by hand, but were instead printed, so the scientists suspect the toxic red ink literally faded from the monastic picture.
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