Academic journal article Scandinavian Journal of Work, Environment & Health

Sensitization and Chronic Beryllium Disease at a Primary Manufacturing Facility, Part 3: Exposure-Response among Short-Term Workers

Academic journal article Scandinavian Journal of Work, Environment & Health

Sensitization and Chronic Beryllium Disease at a Primary Manufacturing Facility, Part 3: Exposure-Response among Short-Term Workers

Article excerpt

Objectives Exposure-response relations for beryllium sensitization (BeS) and chronic beryllium disease (CBD) using aerosol mass concentration have been inconsistent, although process-related risks found in most studies suggest that exposure-dependent risks exist. We examined exposure-response relations using personal exposure estimates in a beryllium worker cohort with limited work tenure to minimize exposure misclassification.

Methods The population comprised workers employed in 1999 with six years or less tenure. Each completed a work history questionnaire and was evaluated for immunological sensitization and CBD. A job-exposure matrix was combined with work histories to create individual estimates of average, cumulative, and highest-job-worked exposure for total, respirable, and submicron beryllium mass concentrations. We obtained odds ratios from logistic regression models for exposure-response relations, and evaluated process-related risks.

Results Participation was 90.7% (264/291 eligible). Sensitization prevalence was 9.8% (26/264), with 6 sensitized also diagnosed with CBD (2.3%, 6/264). A general pattern of increasing sensitization prevalence was observed as exposure quartile increased. Both total and respirable beryllium mass concentration estimates were positively associated with sensitization (average and highest job), and CBD (cumulative). Increased sensitization prevalence was identified in metal/oxide production, alloy melting and casting, and maintenance, and for CBD in melting and casting. Lower sensitization prevalence was observed in plant-area administrative work.

Conclusions Sensitization was associated with average and highest job exposures, and CBD was associated with cumulative exposure. Both total and respirable mass concentrations were relevant predictors of risk. New process-related risks were identified in melting and casting and maintenance.

Key terms average exposure; beryllium disease; cumulative exposure; occupational respiratory disease; peak exposure.

Exposure-response relations for beryllium sensitization (BeS) and chronic beryllium disease (CBD) using various methods for estimating airborne exposure have been inconsistent (1-5). Processes or jobs worked have been used as surrogates for quantitative exposures in many studies. Process-related risks have been identified in the absence of exposure-response (1-3, 6), suggesting that predictive exposure factors do exist but may not have been adequately characterized. Possible explanations may include, among others: (i) quantification of airborne beryllium exposure using metrics that do not take into account biological relevance, rather than metrics that consider lung deposition (7-9), and (ii) inclusion of exposure periods not relevant to risk due to uncertainty regarding time of onset of BeS and CBD in cross-sectional epidemiologie studies.

Physical properties of exposure aerosols, such as aerodynamic particle size, influence deposition and distribution within the human respiratory tract, with size affecting how deeply they are likely to penetrate and where they will likely deposit (10). However, many epidemiologie studies to date have used estimates of total beryllium mass concentration without consideration for particle size (1-3). Some studies have shown an association between exposure to smaller-size particles and BeS or CBD (4, 11). As such, it is biologically plausible to consider beryllium particle size among the exposure factors relevant to the development of an alveolar beryllium lung burden and thus to risk of disease.

The interval between initial exposure to beryllium and the development of BeS can be as short as three months with several studies detecting a higher prevalence of BeS among workers with one year or less of employment tenure (3, 6, 12-14). The interval between initial exposure and the development of CBD is not well understood. In cross-sectional epidemiologie studies, however, it is not possible to know when an individual actually became sensitized or developed CBD. …

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