Longitudinal analyses of chest radiographs from the European Carbon Black Respiratory Morbidity Study

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Abstract
High levels of exposure to carbon black have been linked with an increased prevalence of chest radiograph abnormalities. However, it is unclear to what extent current levels of exposure in the carbon black manufacturing industry are associated with new cases of and progression in small opacities. Longitudinal analyses were carried out on data from workers in the European carbon black manufacturing industry who provided three full-size chest radiographs sequentially between 1987–1995. All chest radiographs were independently read by three experienced readers according to the International Labour Organisation (ILO) classification. After exclusion of participants with previous lung diseases or injuries, females, unreadable chest radiographs and from factories with a low participation rate, data from 675 workers were available for the longitudinal analyses. An association was observed between cumulative carbon black exposure and new cases of chest radiograph abnormalities (ILO category ≥1/0) and progression in small opacities. These associations were mainly related to changes in chest radiographs from workers at one factory. A large percentage of workers with chest radiograph abnormalities reversed to normal chest films; however, after adjusting for other factors, this was not associated with levels of exposure to carbon black dust. In conclusion, the results show that exposure to carbon black is associated with increased risk of chest radiographic abnormalities, which may be reversible after reduction or cessation of exposure.