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Abstract

The 1783 Laki (Skaftáreldar) eruption in Iceland was followed by a severe mortality crisis there (8000 excess deaths 1784-85, about 1/6 of the population), which has been attributed to famine caused by loss of livestock due to fluorine poisoning. Since the 1990ies, it has been suggested that air pollution from the eruption also caused a significant mortality increase in Western Europe around September 1783. This led to suggestions that air pollution and fluorine poisoning directly contributed to human mortality in Iceland. We review the potential impact of pollution and fluorine poisoning on human mortality, using contemporary Icelandic letters and parish registries and estimates of aerosol concentrations and fluorine uptake. Mortality in Iceland was complex, with no increase during the eruption, a peak in spring 1784 in the Northeast and a second peak in winter 1784-85 in the West. This can largely be explained by the interplay of previous weather conditions and volcanic influence on livestock, access to fishing, migration and disease outbreaks. Neither the timing, nor the recorded causes of death point to volcanic pollution as a major proximate cause. Modelled aerosol concentrations in Iceland seem too low to account for such massive mortality. Modelled concentrations in Europe were far below values measured near contemporary eruptions which showed no significant effect on mortality. Estimated human fluorine intake from water, meat or air seems far below the lethal dose. To conclude, while some individuals may have died from aerosol or fluorine poisoning, these were likely not the main contributors.