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Engineering controls in mine assay laboratories.

Hall RM; Sheehy JW; Zimmer AT
Appl Occup Environ Hyg 1998 Sep; 13(9):646-655
An extensive literature search and professional contacts, who have performed industrial hygiene surveys in mine assay laboratories, suggested that mine assay workers are potentially exposed to a wide variety of chemical hazards, including lead, arsenic, silica, and mercury. As a result, the National Institute for Occupational Safety and Health (NIOSH) has undertaken a study to evaluate and disseminate control technology information for reducing these exposures and protecting worker health in this industry. Mine assay laboratories process and analyze samples from mineral exploration and mineral ore recovery operations. Ore samples are prepared for analysis by drying, crushing, splitting, and mixing samples with lead flux. Walk-through surveys were conducted at five mine assay laboratories where effective engineering controls were identified by the literature search and the professional contacts. Two laboratories appeared to represent good engineering controls in the mine assay laboratory industry and were selected for in-depth evaluations; one was located on a mine site and the other was a commercial laboratory. Both laboratories have the potential to exceed the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 50 microg/m3 and the action level of 30 microg/m3 for lead. In the commercial laboratory arsenic exposures exceeded the NIOSH recommended exposure limit OREL) of 2 microg/m3 (ceiling limit) and have the potential to exceed the OSHA PEI. for arsenic of 10 microg/m3. Based on our study results, recommendations to reduce worker exposures are as follows: (1) monitor airborne concentrations if evidence from lab-oratory analytical data indicates increased levels of hazardous metals such as arsenic or cobalt; and (2) require workers to shower and change from work clothes to street clothes before going home. Recommendations to improve ventilation systems in mine assay laboratories are as follows: (1) increase capture velocity on the ventilation hoods in the sample preparation area by increasing the degree of enclosure; (2) use a high efficiency particulate air-filtered vacuum for cleaning in the sample preparation area; and (3) increase exhaust volumes and improve hood design of canopy hoods in fire assay areas to control convection currents generated by furnaces.
Engineering-controls; Monitoring-systems; Air-quality; Air-quality-control; Air-quality-measurement; Air-quality-monitoring; Chemical-manufacturing-industry; Chemical-processing; Chemical-properties; Chemical-reactions; Ventilation; Ventilation-equipment; Ventilation-hoods; Ventilation-systems; Particulate-sampling-methods; Particulates; Heavy-metals
7439-92-1; 7440-38-2; 7631-86-9; 14808-60-7; 7439-97-6
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Journal Article
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NIOSH Division
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Applied Occupational and Environmental Hygiene
Page last reviewed: December 30, 2021
Content source: National Institute for Occupational Safety and Health Education and Information Division