Hidden dangers? An investigation of volcanic and environmental impacts on human health and life in historical Iceland

Abstract

Volcanic eruptions can cause significant human health and environmental threats both during and after their event due to the hazardous materials and gases that are actively or passively released into the surrounding environment. Historical records suggest that severe historic eruptions in Iceland caused mass mortality to livestock, famine, altered weather and led to the contamination of water and air, all of which significantly impacted the health and living condition of people in the past. The aim of the project was to investigate the effects of volcanic eruptions on human health across Icelandic history, as well as the impacts of the anthropogenic use of heavy metals (e.g., Hg, As, Pb) and climate change (e.g., cooling weather during the Little Ice Age).

The study used a range of different methods but mainly analyses on human and animal bones and soil samples. Standard osteological analyses were conducted on skeletal individuals (n=186) from archaeological sites (n=7) across Iceland dated between the 10th and the 19th century. Samples were then collected for further analyses: human bone (n=36) and teeth samples (n=31), as well as animal bone samples (n=23) and soil samples (n=13), which were selected from the monastic-hospital site of Skriðuklaustur (AD 1493-1554). In addition to previously published comparative data, bone samples (n=14) and soil samples (n=9) were selected from a farm site, called Skeljastaðir, which was abandoned during the AD 1104 eruption of the nearby volcano Hekla. Standard osteological and palaeopathological methods were used for the skeletal analysis and anthropological descriptions. Microscopy, radiography, endoscopy, and other specialized techniques were used where necessary. Isotope (δ18O, 87Sr/86Sr, δ13C) and trace element (Hg, Pb, Cd, As, Zn, Sb, Ba, Sr) analysis of dental enamel was undertaken to investigate geographic provenance and possible exposure to toxic emissions during childhood. At the same time, isotope ratio mass spectometry of bone collagen samples (δ13C, δ15N, δ34S) from humans and animals was used to reconstruct palaeodiet and provide indications about overall nutrition. Trace element analysis (ICP-MS and ISE) was also used on bone samples to investigate ante-mortem exposure to toxic elements of volcanogenic origins (F, Hg, Pb, Cd, As). Isotope analyses conducted for the reconstruction of geographic provenance of the people buried at Skriðuklaustur showed a local population born in Iceland that came to the monastery seeking treatment, hospice, trade, or religious activity from throughout the south-eastern quarter of the country. Dietary reconstruction showed a mixed marine and terrestrial diet with freshwater fish input at the monastic-hospital Skriðuklaustur, while a primarily terrestrial protein diet with freshwater fish input at the inland farm site Skeljastaðir.

Overall, the results indicated that the burden of skeletal fluorosis on the human population was low, perhaps because people, unlike the livestock, quickly fled from areas directly impacted by volcanic fallout. The skeletal burden of most other volcanogenic pollutants was also low, indicating that any slight elevations were the result of natural, passive background emissions or limited anthropogenic exposure. However, mercury was elevated in these skeletal assemblages, due to both anthropogenic uses (e.g., as a medicine) and volcanogenic exposure. The impacts of volcanic hazards in the past cannot be dismissed and they certainly caused complicated, life-threatening, and long-term effects upon the living conditions and health of people in the past. On the other hand, it seems that the immediate dangers (e.g., volcanic smoke, lava flow) were mostly circumvented, unlike previously hypothesized. People likely mitigated against volcanic disasters by temporarily moving away from areas undergoing eruptions.