Occupational and Environmental Medicine 1994;51:195-199 Lung retention of cerium in humans

A retrospective study was conducted to evaluate lung retention of particles containing cerium in subjects with and without previous occupational exposure to mineral dusts. Analytical transmission electron microscopy was performed on 459 samples of bronchoalveolar lavage (BAL) fluid and 75 samples of lung tissue. Study of the distribution of mineralogical species in human samples showed that particles containing cerium were encountered in less than 10% of subjects. The proportion of subjects with particles containing cerium in their biological samples was not different between controls and subjects with previous occupational exposure to fibrous or nonfibrous mineral dusts. This was considered as the background level of lung retention of cerium in the general population. By contrast, determination of the absolute concentration of particles containing cerium in BAL fluid and lung tissue samples showed that 1 2% (from BAL fluid) and 15% (from lung tissue) of subjects with previous exposure to mineral particles had high lung retention of particles containing cerium. This study is believed to be the first one in which lung retention of cerium was estimated in the general population. INSERM Unite 139, Hopital Henri Mondor, 51 avenue du Marechal de Lattre de Tassigny, 94010 Creteil cedex, France J C Pairon F Roos Y Iwatsubo J Bignon P Brochard Institut Interuniversitaire de Medecine du Travail de Paris-Ile de France, 15 rue de l'Ecole de Medecine, 75006 Paris, France J C Pairon P Brochard Laboratoire d'Etude des Particules Inhalees, 11-13 rue George Eastman, 75013 Paris, France X Janson M A Billon-Galland P Brochard Requests for reprints to: Dr J C Pairon, INSERM Unite 139, H6pital Henri Mondor, 51 avenue du Marechal de Lattre de Tassigny, 94010 Creteil cedex, France. Accepted 12 July 1993 (Occup Environ Med 1994;51:195-199) Cerium and other rare earth elements have several industrial applications, particularly because of their luminescent and magnetic quality as well as their abrasive, colouring, decolouring, and catalytic properties. Numerous occupational groups may therefore be exposed to rare earths, as in the manufacture and use of arc lamps, and in the glass, optical, electronic, watchmaking, nuclear, metallurgical, and chemical industries.' 2 Cerium dust is generally considered to be relatively inert in experimental models.34 So far, only case reports have been published dealing with lung diseases in humans potentially related to exposure to rare earth compounds.5 Lung biopersistence of cerium has sometimes been described in individual cases, but no evaluation of lung retention and biopersistence of this mineral has been made in occupationally exposed groups or in the general population. Lung dust load may be assessed either directly from chemical and mineralogical analysis of samples of lung tissue, or estimated from analysis of bronchoalveolar lavage (BAL) fluid. Previous studies in humans have shown that the concentration of asbestos bodies in BAL fluid was correlated with parenchymal concentration. 15 Less is known about non-fibrous mineral particles. Nevertheless, good agreement has been reported between the particle types in BAL fluid and lung samples of subjects free of known recent occupational exposure to nonfibrous mineral particles. 16 The interest in mineralogical analysis of non-fibrous mineral particles in BAL fluid of subjects with various occupational exposures has been previously noted. 17-20 Our study was undertaken to determine the frequency of lung retention of particles containing cerium in the general population. For this purpose, we analysed BAL fluid and lung tissue samples retrospectively from patients with and without previous exposure to mineral dusts to estimate the background level of particles containing cerium in these samples. In subjects exhibiting significant lung retention of particles containing cerium, with previous occupational exposures to mineral dusts and especially to those associated with cerium, assessment was made of lung diseases found and of the biopersistence of particles containing cerium in the respiratory