[Longitudinal study of radiologic anomalies in subjects working in asbestos-insulated buildings]. / Etude longitudinale des anomalies radiologiques chez des sujets travaillant dans des locaux floqués à l'amiante.

The respiratory effects of environmental pollution by asbestos was examined in a cohort of subjects working inside university buildings partly insulated with asbestos containing materials (University of Jussieu in Paris). The present study concerned 727 subjects having undergone two standard radiographic examinations (postero-anterior and oblique chest x-ray) in the period 1981-1992. The first examination was realized between 01/01/81 and 31/12/85 and the second examination took place between 01/01/86 and 31/12/92. The subjects were classified into three groups according to their exposure status: the group G1 consisted of 161 workers occupationally exposed to asbestos; the group G2 comprised 416 subjects working for at least 15 yr in asbestos-insulated buildings without known occupational exposure to asbestos; the group G3 consisted of 150 workers working for at least 15 yr in the university with no known exposure to asbestos. Whatever the radiological abnormalities considered, no significant difference was observed between G2 and G3 in cross-sectional analyses of the two phases. The group G1 exhibited a significantly higher prevalence of pleural thickening compared to the other exposure groups after adjustment for confounding variables. Detailed examination of oblique x-ray allowed to confirm that pleural thickening were largely due to extrapleural fat. Concerning the changes in pleural abnormalities between the two phases of the study, no difference was observed between G2 and G3. This study was unable to show any excess of radiographic chest abnormalities among subjects working in asbestos-insulated buildings compared to non-exposed subjects. However, the participation in the second phase of examination was 51.2%. The study is still on-going. Therefore, it would be necessary to continue to follow-up the subjects because respiratory disorders could occur after a long latent period.

Pleural thickening: a comparison of oblique chest radiographs and high-resolution computed tomography in subjects exposed to low levels of asbestos pollution.

The present study was conducted to investigate the value of oblique chest radiographs, compared with high-resolution computed tomography (HRCT), in the assessment of pleural asbestosis in a group of subjects exposed to low levels of asbestos pollution. The study population consisted of 23 people derived from a previously reported cohort of subjects working in university buildings insulated with asbestos-containing material. Subjects were selected on a voluntary basis from among patients whose initial oblique chest X-rays showed pleural thickening. Sixteen patients were maintenance workers occupationally exposed to asbestos; the remaining seven were environmentally exposed to asbestos. For each subject, two standard chest radiographs [posteroanterior (PA) and right anterior oblique (RAO) views] were taken and HRCT was performed. Films were interpreted after agreement by three chest physicians and a radiologist. Pleural thickening was considered present in all 23 patients on RAO films and in six patients on PA films. HRCT revealed unequivocal pleural plaques in three maintenance workers and doubtful pleural abnormalities in three other maintenance workers. Considering HRCT as the "gold standard," the positive predictive value of RAO film was only 13%-26%. Most of the 17 false-positive diagnoses of pleural fibrosis were due to significant subpleural fat. These results suggest that the routine use of oblique radiographs as a screening test in cohorts of subjects exposed to low levels of pollution by asbestos should be reevaluated.