At levels of 250 ppm (or more) of dry mass of grass, animals that eat it die within days: the death of animals in the first days of Laki which Jon describes may have been due to fluorine poisoning rather than sulphur. And with Iceland responsible for around 8% of the world’s on-land lava production, with higher than average fluorine abundance, Iceland may be the origin of 10% or more of the total fluorine emissions. There have been four eruptions with fluorine poisoning in Iceland since 1700, from Hekla and Laki, most recently in 1970, with impacts ranging from sheep deaths to depopulation of Iceland.