Accumulation of fluoride in Icelandic sheep and horses 2007-2019 and the effect of proximity to aluminium smelters

Abstract

Environmental monitoring by aluminium smelters in Iceland has included fluoride analysis of sheep and horse mandibles. Statistical modelling was done retrospectively on fluoride analyses of sheep and horses from 2007 to 2019. Relationships between the fluoride concentration in bone tissue and the age and the regional origin of the animals were investigated, along with the effect of proximity to aluminium smelters. Furthermore, the development of fluoride accumulation in sheep mandibles through the years and pathological changes were explored. A positive correlation was found between age and fluoride concentration, with a decline after a certain age. Fluoride concentration was highest in areas with aluminium smelters, in sheep in the Southwest and East of Iceland and in horses in the Southwest. Fluoride concentration in lambs around a Southwest smelter decreased significantly during 2007-2014. Pathological changes compatible with fluorosis were seen in the tooth enamel of sheep from around the smelter, in connection with an accidental burst of emissions in August 2006. Keywords: Domestic animals, environmental monitoring, fluorosis, herbivores, Iceland, pathology