Volcanoes, medicine, and monasticism: Investigating mercury exposure in medieval Iceland

Abstract

This study aimed to evaluate the possible use of mercury as a medical treatment at the medieval monastic hospital Skriðuklaustur (ad 1494–1554) in eastern Iceland. The individuals excavated from Skriðuklaustur exhibited a wide range of pathological conditions, including the only skeletal evidence of venereal syphilis in Iceland. Skeletal remains from the Skeljastaðir cemetery (ca. ad 1000–1104) in southern Iceland were also analysed in light of the site's proximity to the mercury emitting volcano Hekla. The eruption produced a severe toxic fallout resulting in the mass mortality of livestock and is believed to have caused the abandonment of Skeljastaðir and the other farms in the region. The skeletal analyses and sampling were conducted according to standard anthropological methods. Mercury concentrations were determined in human (n = 50), faunal (n = 23), and soil (n = 22) samples using inductively coupled plasma mass spectrometry. Individuals from both sites exhibited elevated mercury concentrations. At Skriðuklaustur, some individuals showed normal concentrations, but those with pathological conditions (e.g., hydatidosis, syphilis, tuberculosis, and other non‐specific infections) had the highest concentrations overall. On the other hand, all the individuals analysed from Skeljastaðir exhibited elevated mercury concentrations, some of which were remarkably high. A few of the individuals buried at Skeljastaðir post‐date the eruption, possibly indicating that some of them experienced heavy exposure to volcanic emissions. The less extreme concentrations at Skriðuklaustur may be a result of attention to dosage and the temporary nature of mercurial treatments. None of the faunal and soil samples presented with concentrations exceeding the normal limit, implying that diagenesis was not a concern in this research. The conclusion is that a variety of factors from medical treatment to scholarly work lead to mercury exposure at Skriðuklaustur, whereas at Skeljastaðir, volcanogenic emissions are implicated.

Comparison of trace element chemistry in human bones interred in two private chapels attached to Franciscan friaries in Italy and Denmark: an investigation of social stratification in two medieval and post-medieval societies

“…Mercury had an extremely low environmental occurrence in most medieval societies in both Denmark and Italy [2,32]. Even so, Hg has been found in high concentrations in medieval and post-medieval human individuals in several studies [2,32,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]. Some individuals were only exposed to the environmental Hg background, which has been estimated to correspond to 80 ng g −1 in cortical and 300 ng g −1 in trabecular bone tissue in Danish and German medieval and post-medieval skeletons [46].…”

“…A mixture of 45 Sc, 89 Y, and 159 Tb was used as internal standard added to all analyses. The following isotopes were measured without skimmer gas: 44 Ca, 55 Mn, 88 Sr, 137 Ba, and 208 Pb. 56 Fe was measured with hydrogen as skimmer gas.…”

Advancing the understanding of treponemal disease in the past and present

“…Following a preliminary study by Yamada et al (), in the last decade, bioarchaeologists have attempted to evaluate mercury (Hg) levels in bone and surrounding soils using various analytical techniques, including ICP‐MS (Tucker ; Walser, Kristjánsdóttir, Gowland, & Desnica, ), laser ablation ICP‐MS (LA‐ICP‐MS; Kępa et al, ), advanced mercury analyzer (AMA; Rasmussen et al, ), atomic absorption spectroscopy (AAS; Rasmussen et al, , ), and pXRF (Zuckerman, , ). However, it remains unclear how reliable results are from more recently developed instrumentation such as pXRF relative to established ICP‐MS analyses of bone, as x‐ray depth, complex microstructures, and diagenetic change can substantially affect pXRF results (Byrnes & Bush, ; Shugar & Mass, ).…”

“…In addition, while substantial Hg contributions from environmental or occupational exposure are typically rare, they may complicate interpretations of intentional, medicinal uptake to treat conditions such as treponemal disease, particularly in areas with active volcanoes where atmospheric concentrations of mercury may be naturally high (Walser et al, ); when used in the manufacturing various items including hats, mirrors, lamps, and shoes (Katz & Krenkel, ; Lee, ); and where foods high in methylmercury, such as seafood, are consumed (Iyengar & Woittiez, ; Sheehan et al, ). Subsequently, control samples—including from surrounding soils, faunal bone, as well as other human skeletons with no outward expression of treponemal disease—must be analyzed alongside those individuals diagnosed with treponematosis to ensure that exogenous sources of mercury are not mistaken for treatment (Kępa et al, ; Rasmussen et al, ; Walser et al, ; Zuckerman, ). Moreover, as unaffected human skeletons may still represent victims of treponematosis who were treated with mercury but whose bones never developed diagnostic lesions, alternate controls (soil, faunal), as well as greater numbers of control human samples, are recommended (Wood et al, ; Zuckerman, ; see also section 6.3.5).…”

Historical overview and new directions in bioarchaeological trace element analysis: a review

“…Another interesting area of research is investigating the extent that the skeletal toxic TE burden among past individuals stems from medicinal and care practices of past populations. Both As and Hg have historically been used as medicine by health practitioners from various populations (Goldwater 1972 ; Jolliffe 1993 ); some bioarchaeological studies have consequently investigated cases of As and Hg toxicity potentially resulting from medicinal treatments (Tucker 2007 ; Rasmussen et al 2008 ; Kępa et al 2012 ; Swanston et al 2015 ; Walser III et al 2018 ; Dabrowski et al 2019 ). Comparatively high levels (16.17 ± 0.58 μg/g) of skeletal As were discovered in an individual from Wroclaw, Poland (late sixteenth to mid-eighteenth centuries CE) with skeletal signs of syphilis, indicating As was used as a medicine (Dabrowski et al 2019 ).…”