"More poison than words can describe": What did people die of after the 1783 Laki eruption?

The 1783 Laki eruption in Iceland was followed by an almost 20 % population loss, traditionally attributed to famine (caused by fluorine poisoning of livestock) and contagious diseases. From the 1970s, hypotheses were formed that fluorine poisoning might have contributed to human mortality in Iceland, and air pollution might have caused excess deaths both in Iceland and Europe. Using historical documents including parish registries, we find that regional and temporal patterns in Icelandic excess mortality can be satisfactorily explained by hunger and disease, when other factors such as the availability of secondary food sources (fishing, food aid) are taken into account. In contrast, the timing and estimated concentrations of air pollution do not match observed excess mortality, and observed symptoms and estimated human fluorine uptake do not suggest large-scale fluorosis in humans. We therefore conclude that the evidence for significant direct contributions from pollution to human mortality is weak.