The skeletal changes found in workers exposed to fluorine compounds were first described in 1932 by Flemming Møller and Gudjonsson.1During the examination of cryolite workers for pulmonary manifestations of exposure to dust, their attention was directed to a peculiar form of bone sclerosis, occurring in a certain percentage of workers who had been exposed to cryolite dust for a number of years.Cryolite is a double fluoride of sodium and aluminium, occurring naturally, chiefly in Iceland and North America. The raw material is quarried on a large scale in Iceland, and shipped to Copenhagen, where it is crushed and refined before being used as a source of metallic aluminium.The original investigation by Flemming Møller and Gudjonsson was followed by an extensive research into the effects of fluorine by Roholm.3In an excellent monograph, in which the whole subject is studied from the clinical, biochemical and experimental aspects, Roholm gives a complete survey of the toxic effects of fluorine. The monograph is also notable for a very complete bibliography.Bishop,4in America, described a case of fluorine intoxication occurring in a worker engaged in the manufacture of a chemical fertiliser, in which fluorine was present as a contaminant. Shortt6(quoted by Flemming Møller) reported cases of osteosclerosis occurring in natives of India, where the drinking water contained considerable quantities of fluorine.Cases of “mottled teeth” have been reported in Europe and America.