Incidence of ferruginous bodies in the lungs during a 45-year period and mineralogical analysis of the core fibres and uncoated fibres.

In order to determine the level of asbestos pollution in the lungs of members of the general population in and around Tokyo, the incidence of ferruginous bodies in autopsied or resected lungs during 5 periods over the 45 years from 1937 to 1981 was studied under a light microscope. Core fibres, after removal of their ferruginous coatings with oxalic acid, and uncoated fibres were analysed using a scanning electron microscope equipped with a Kevex energy-dispersive X-ray spectrometer. The incidence of ferruginous bodies in 5 g (wet) of digested lung tissue was shown to be 10% in period I (1937-1941), 18% in period II (1947-1951), 70% in period III (1958-1963), 74.4% in period IV (1970-1973) and 81.0% in period V (1980-1981). The major types of core fibres of ferruginous bodies were found to be asbestos, including amosite, crocidolite, chrysotile and the tremolite-actinolite series, but a small number of fibres of materials other than asbestos were also detected. In contrast, a large number of short fibres less than 5 microns in length in 1 g of wet lung tissue were classified as belonging to the Mg+Si group (the ratio of Mg to Si components being 30% or over) and presumed to be chrysotile. Thus an annual increase in asbestos deposition in the lungs of people living in and around Tokyo has been demonstrated and fine chrysotile fibres less than 5 microns in length seem to be the main type of deposited fibres.