Beryllium sensitization and disease among long-term and short-term workers in a beryllium ceramics plant
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Objective: Workers at a beryllium ceramics plant were tested for beryllium sensitization and disease in 1998 to determine whether the plant-wide prevalence of sensitization and disease had declined since the last screening in 1992; an elevated prevalence was associated with specific processes or with high exposures; exposure-response relationships differed for long-term workers hired before the last plant-wide screening and short-term workers hired since then. Methods: Current workers were asked to complete a questionnaire and to provide blood for the beryllium lymphocyte proliferation test (BeLPT). Those with an abnormal BeLPT were classified as sensitized, and were offered clinical evaluation for beryllium disease. Task- and time-specific measurements of airborne beryllium were combined with individual work histories to compute mean, cumulative, and peak beryllium exposures for each worker. Results: The 151 participants represented 90% of 167 eligible workers. Fifteen (9.9% of 151) had an abnormal BeLPT and were split between long-term workers (8/77=10.4%) and short-term workers (7/74=9.5%). Beryllium disease was detected in 9.1% (7/77) of long-term workers but in only 1.4% (1/74) of short-term workers (P=0.06), for an overall prevalence of 5.3% (8/151). These prevalences were similar to those observed in the earlier survey. The prevalence of sensitization was elevated in 1992 among machinists, and was still elevated in 1998 among long-term workers (7/40=18%) but not among short-term workers (2/36=6%) with machining experience. The prevalence of sensitization was also elevated in both groups of workers for the processes of lapping, forming, firing, and packaging. The data suggested a positive relationship between peak beryllium exposure and sensitization for long-term workers and between mean, cumulative, and peak exposure and sensitization for short-term workers, although these findings were not statistically significant. Long-term workers with either a high peak exposure or work experience in forming were more likely to have an abnormal BeLPT (8/51=16%) than the other long-term workers (0/26, P=0.05). All seven sensitized short-term workers either had high mean beryllium exposure or had worked longest in forming or machining (7/55=13% versus 0/19, P=0.18). Conclusions: A plant-wide decline in beryllium exposures between the 1992 and 1998 surveys was not matched by a decline in the prevalence of sensitization and disease. Similar to findings from other studies, beryllium sensitization/disease was associated with specific processes and elevated exposures. The contrast in disease prevalence between long-term and short-term workers suggests that beryllium sensitization can occur after a short period of exposure, but beryllium disease usually requires a longer latency and/or period of exposure. The findings from this study motivated interventions to more aggressively protect and test workers, and new research into skin exposure as a route of sensitization and the contribution of individual susceptibility.
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