Background: It has been suggested that malignant mesothelioma might be mainly or only connected with the action of short and ultrathin fibres. On the basis of this hypothesis fibres less than 5 microm long and 0.2-0.1 microm thick would enter the pulmonary-pleura barrier and reach the parietal pleura thus inducing mesothelioma. The hypothesis raised a stimulating scientific discussion.
Objectives: The aim of this communication is to report the initial results obtained comparing the size of amphibole fibres from healthy lung tissue with those from pleural tissue sampled from subjects whose death cause of death was mesothelioma.
Methods: Four mesothelioma cases due to environmental exposure were studied; the fibres were categorized by scanning electron microscopy; for every fibre, length and diameter were measured and the mineral type was defined by its chemical composition determined by X-ray microanalysis.
Results: The most important characteristics of the detected fibres were: the average length offibres from the lung and pleural tissues taken from the same subject did not difer, in all cases, by more than 10-12%; 95% offibres found in the lung tissues of all subjects had a length greater than 5 microm; 98% of fibres found in the pleural tissues had a length greater than 5 microm; the average diameter of the fibres found in the pleural tissues was 70% of the diameter of the fibres from the lung tissues.
Conclusions: The experimental data obtained in this study confirm the correlation between malignant mesothelioma and the presence in the lung and pleural tissues of fibres with a length greater, even much greater, than 4-5 microm; thus the hypothesis that the chief factors inducing mesothelioma are the "ultrashort" and "ultrathin" fibres appears rather weak.