Comparison of the standard and dark-medium objective lens in counting asbestos fibers by phase-contrast microscopy

Details

• Personal Author:
  Harper M ; Kashon M ; Lee E ; Nelson J
• Description:
  Objective: A Japanese round-robin (RR) study revealed that the analysts who used a dark-medium (DM) objective lens reported higher fiber counts of Proficiency Analytical Testing (PAT) chrysotile samples than those with a standard objective lens but no causes of such differences were investigated. The purpose of this study was to determine the major sources of the differences of fiber counts between two objective lens types by performing two sets of RR studies. Methods: For the first RR study, 15 proficiency test sample filters (five each of chrysotile and Amosite generated by water-suspended method and five chrysotile generated by aerosolization method) were purchased from the American Industrial Hygiene Association (AIHA) and slides were prepared with relocatable cover slips. Nine labs volunteered to participate in the exercise. A single microscope with both standard and DM objectives was circulated to each laboratory along with the prepared slides. A second RR study was then performed with six chrysotile field sample slides. Six out of nine labs who participated in the first RR study participated. Additionally, an 8-form diatom test slide was examined by eight analysts to compare resolutions between two objectives. Results: For the PAT chrysotile reference slides, use of the DM objective resulted in consistently higher fiber counts (1.45 times for all data) than the standard objective (p-values: < 0.05), regardless of the filter generation (water-suspension or aerosol) method. For the PAT Amosite and chrysotile field sample slides, the fiber counts between the two objectives were not significantly different. There was no differences of resolution from the 8-form diatom test slide examination. Conclusions: The findings support the contrast caused by the different phase plate absorption between the two objectives as the main factor affecting high number of PAT chrysotile fiber counts using the DM objective. The chrysotile fibers in the PAT samples are thinner than the airborne contaminant fibers collected from the field. If the thin PAT fibers are not generally representative of field samples, it is not necessary to recommend the DM objective be used for routine fiber-counting. However, the DM objective does allow more very fine fibers to be counted and may provide counts of those fine fibers, if present, similar to that achievable with an electron microscope. [Description provided by NIOSH]
• Subjects:
  Aerosols Asbestos Dust Inorganic Chemicals Laboratories Microbiology Occupational Health Particulate Matter Safety
• Keywords:
  Aerosol-sampling Asbestos-fibers Fibrous-bodies Fibrous-dusts Filters Microscopic-analysis Sampling
• Publisher:
  American Industrial Hygiene Association
• Document Type:
  Text
• Genre:
  Abstract or Summary
• Place as Subject:
  OSHA Region 3 ; OSHA Region 8 ; Utah ; West Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  HELD - Health Effects Laboratory Division
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  90
• NIOSHTIC Number:
  nn:20046280
• Citation:
  AIHce 2015: American Industrial Hygiene Conference and Exposition, May 30 - June 4, 2015, Salt Lake City, Utah. Falls Church, VA: American Industrial Hygiene Association, 2015 May; :90
• Federal Fiscal Year:
  2015
• NORA Priority Area:
  Mining
• Peer Reviewed:
  False
• Source Full Name:
  AIHce 2015: American Industrial Hygiene Conference and Exposition, May 30 - June 4, 2015, Salt Lake City, Utah
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:a796f6c21f0669aa4e5a2f17eea9992a96e29b1219d0e5df7a3c559db1775de3cac2554f93097b1a4aa6c2fa2de8c11fd9f6654e35ac6f3de1e76bbf530afe98
• Download URL:
  https://stacks.cdc.gov/view/cdc/201384/cdc_201384_DS1.pdf
• File Type:
  [PDF - 683.78 KB ]