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Dose of beryllium causing beryllium sensitization and disease.

NIOSH 2005 Apr; :1-20
Chronic beryllium disease (CBD) and beryllium sensitization (BeS) continue to occur in the modern beryllium industry, despite efforts to reduce exposure. This disease is the consequence of a cell-mediated hypersensitivity immune response to beryllium, and may preferentially affect those exposed individuals with genetic susceptibility to beryllium. There appears to be an atypical dose-response relationship between beryllium exposure and disease with both genetics and features of exposure contributing independently to the risk of BeS and CBD. Studies suggest that features of exposure, such as particle size, may be important in determining risk for CBD. We set out to determine the personal beryllium dose that produces BeS and CBD in a beryllium machining plant and examined the relationship of particle size to the development of BeS and CBD. Methods. We examined the personal daily beryllium exposures for new employees in a precision beryllium machining plant. New workers wore a personal sampling pump each day for the first three months of employment. We also examined exposure to beryllium and the presence of BeS and CBD in a cohort of workers in at this facility. Twenty cases of BeS or CBD were compared to 206 worker controls in a case-control study. Exposure for each job title was measured using cascade impactors placed in the workers breathing zone to measure total beryllium exposure and exposure to particles < 6 microm and < 1 microm in aerodynamic diameter. Cumulative exposure was calculated as the sum (Job Title Exposure Estimate x Years in Job Title). Individual lifetime-weighted (LTW) exposure was calculated as the sum [(Job Title Exposure x Years in Job Title)/Total Years Employment)]. We also assessed the agreement of individual personal sampling to the routine air sampling collected by the plant. Results. Personal daily exposures for new employees were below the plant action level of 0.2 microg/m3 for 90% of workers participating. Cases of BeS and CBD in this plant were more likely to have worked as a machinist (odds ratio [OR], 4.4; 95% confidence interval [CI], 1.1 to 17.5) than controls. The median cumulative exposure was consistently greater in cases compared to controls for all exposure estimates and particle size fractions, although not statistically significant. Median cumulative exposure was 2.9 microg/m3 -yrs in cases vs. 1.2 microg/m3 -yrs in controls for total exposure and 1.7 microg/m3 -yrs in cases vs. 0.5 microg/m3 -yrs in controls for exposure to particles less than 6 microm in diameter. The median LTW exposure was 0.25 microg/m3 in both cases and controls. The median LTW exposure to particles less than 6 microm was 0.20 microg/m3 in cases compared to 0.14 microg/m3 in controls. The differences in cumulative and lifetime-weighted exposure were not statistically significant. None of the 22 workers with LTW exposure less than 0.02 microg/m3 had BeS or CBD. Twelve (60%) of the cases had LTW exposures greater than 0.20. Mean and median exposures for daily air monitoring (DAM) were significantly lower than median exposures for the systematic sampling approach with exposures from the systematic sampling approach ranging from 0.06 micro/m3 to 0.13 microg/m3 and the median exposures for daily monitoring ranging from 0.02 micro/m3 to 0.08 microg/m3. The 95% upper tolerance limit (UTL) calculated from the systematic sampling approach data was effective in predicting that fewer than 5% of the exposures reported in the daily air monitoring data would exceed the UTL for six of the seven operations. Conclusions: In conclusion, increased cumulative and lifetime weighted exposure to total and respirable beryllium was observed in cases of CBD and BeS compared to the controls. Despite the lack of statistical significance, these results support efforts to control beryllium exposure in the workplace. In addition routine air monitoring performed by the plants for target level compliance may overestimate median beryllium exposures. However, the use of the Upper Tolerance Limit (UTL) appears to be relatively effective in controlling exposures below a given target level. This study suggests that exposures causing BeS may be lower than those reported using data from systematic exposures assessments.
Beryllium-compounds; Beryllium-disease; Heavy-metals; Pulmonary-system-disorders; Pulmonary-disorders; Respiratory-system-disorders; Particulate-dust; Particulates; Statistical-analysis; Epidemiology; Humans; Genetics; Genetic-factors; Dose-response
Division of Environmental and Occupational Health Services, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206
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Final Grant Report
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National Institute for Occupational Safety and Health
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National Jewish Medical and Research Center