The potencial role of rare earths in the pathogenesis of interstitial lungdisease: a case report of movie projectionist as investigated by neutron activation analysis

A 60-year-old male subject who worked as a movie projectionist and who was exposed for 12 years to rare earths (RE) containing dusts from cored are li ght carbon electrodes was investigated. Chest X-ray films and pulmonary fun ction tests showed an interstitial lung disease, emphysema and a severe obs tructive impairment with marked decrease of carbon monoxide diffusion capac ity. The histological examination of a transbronchial biopsy confirmed the diffuse interstitial lung fibrosis. Neutron activation analysis (NAA) of th e biopsy showed concentrations of cerium (Ce), lanthanum (La), neodimium (N d), samarium (Sm), terbium (Tb) and ytterbium (Yb) which were high compared to the corresponding elements in the transbronchial biopsies of 5 unexpose d subjects as a control group. Thorium (Th) (which is generally present as an impurity of the RE compounds) was also determined in order to estimate t he radiation dose in the lung of the worker. On the basis of the clinical observations, of the analytical results by neu tron activation analysis of RE and of the presence of Th in the transbronch ial biopsy, as well as of the differential diagnosis, which tended to exclu de other occupational or non-occupational lung diseases, a relation between the observed interstitial lung fibrosis and occupational exposure to RE is highly probable.