Osteopontin, asbestos exposure and pleural plaques: a cross-sectional study

In 193 workers, 50 with pleural plaques (PP), in whom different indicators of past asbestos exposure were estimated, OPN plasma levels were assessed using commercial quantitative sandwich enzyme immunoassays according to the manufacturer's instructions.Osteopontin increased with increasing age and several aspects of asbestos exposure, without differences related to the presence of pleural plaques. At multivariable regression analysis, the explanatory variables with a significant independent influence on OPN were length of exposure (positive correlation) and time elapsed since last exposure (positive correlation).Since asbestos in lung tissue tends to wane over time, OPN should decrease (rather than increase) with time since last exposure. Therefore, OPN cannot be a reliable biomarker of exposure nor effect (presence of pleural plaques).In the absence of quantitative exposure data, asbestos exposure could be retrospectively evaluated. According to the job-exposure matrix (JEM) approach, the workers are divided into homogeneous groups, based on combinations of plant, work area, job title, historical period; the available industrial hygiene measurement series are then related to the same groups. The main limitations of this approach are that: (i) trends over time are often unknown; and (ii) the inter-individual variations within "homogeneous" groups - i.e.: same job title - can sometimes be more relevant than those between groups [1].In the job-specific modules (JSM) approach, the most significant factors capable of affecting the exposure intensity are first identified; their relative importance is then assessed, based on the available industrial hygiene historical data, or the engineering evaluation of tasks/operations, or both of them. The main limitations of the JSM approach are: (i) the relative importance of the various determinants may prove difficult to be assessed; (ii) concordance among experts about this item may be poor; (iii) the quality of the available in