Occupational Exposures to Asbestos: Effects of Unregulated Fibers

Details

• Personal Author:
  Richardson DB
• Description:
  The objective of this project was to draw upon unique existing data for US asbestos workers for whom high-quality estimates of asbestos exposure have been derived by PCM and fiber-size specific estimates of exposure have been derived by TEM in order to estimate the effects of the unregulated fraction of fibers, estimate TEM-based policies that would yield a comparable mortality to that obtained under current OSHA standards, and, estimate alternative TEM-based policies that would yield lower mortality. Occupational standards for asbestos exposure in the US are based on visual counting of particles by phase contrast microscopy (PCM). Only fibers long and thick enough to reliably count using that method are regulated. However, in most occupational settings the majority of asbestos fibers are too small to count by PCM. If asbestos exposure estimates based upon PCM methods were strictly proportional to total exposure to all etiologically-relevant asbestos fibers then a policy that regulated asbestos exposure as measured by PCM might suffice to control etiologically-relevant occupational asbestos exposures. However, there is strong evidence that the proportion of asbestos fibers that are not counted by PCM varies by work activity, fiber quality, and other conditions. This issue has been raised repeatedly by workers and their advocates, who have argued for regulating exposure to asbestos using methods and rules that permit quantification of short (<5 microm) and thin (<0.25 microm) fibers, such as transmission electron microscopy (TEM) analysis of air samples. One obstacle to this has been that most occupational studies of asbestos workers have classified people based on PCM estimates of exposure. Regulators noted that it was unclear what level of exposure, as quantified by TEM, would be acceptable, since TEM estimates of the total number of fibers may not be well correlated with PCM estimates of fiber counts. First, we used hierarchical regression methods to estimate the effects of the unregulated fraction of fibers; second, we used G-methods to estimate TEM-based policies that would yield a comparable mortality to that obtained under current OSHA standards; and, finally we used G-methods to estimate alternative TEM-based policies that would yield less mortality than that obtained under current OSHA standards. The project applied innovative epidemiological methods to estimation of associations between occupational exposures and disease in settings of complex, protracted occupational exposure histories, and potential bias due to health-related selection out of employment. [Description provided by NIOSH]
• Subjects:
  Air Pollutants, Occupational Air Pollution Asbestos Carcinogens Environmental Exposure Inorganic Chemicals Lung Lung Diseases Microbiology Mortality Neoplasms Occupational Exposure Occupational Health Respiratory System Respiratory Tract Diseases Risk Assessment Safety Textile Industry

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• Keywords:
  Air Analysis Air Contaminants Air Pollutants Air Quality Monitoring Asbestos Fibers Asbestos Industry Cancer Rates Electron Microscopy Exposure Assessment Exposure Levels Fibrous Bodies Lung Cancer Microscopic Analysis Mortality Data Mortality Rates Occupational Exposure Occupational Respiratory Disease Quantitative Risk Assessment Textile Workers

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• Series:
  Grant Final Reports
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Final Grant Report
• Place as Subject:
  North Carolina ; OSHA Region 4
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  OEP - Office of Extramural Programs
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-7
• NIOSHTIC Number:
  nn:20052099
• NTIS Accession Number:
  PB2018-101415
• Citation:
  Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, R03-OH-010706, 2017 Mar; :1-7
• Contact Point Address:
  David Richardson, Department of Epidemiology, McGavran-Greenberg Hall, School of Public Health, CB#7435 University of North Carolina, Chapel Hill, NC 27599-7435
• Email:
  david.richardson@unc.edu
• CAS Registry Number:
  Asbestos (CAS RN 1332-21-4)
• Federal Fiscal Year:
  2017
• Performing Organization:
  University of North Carolina at Chapel Hill
• Peer Reviewed:
  False
• Start Date:
  20140901
• Source Full Name:
  National Institute for Occupational Safety and Health
• End Date:
  20160831
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:046d8c515082bde12f4c489a43936a32beaeac72dbf3dfd0f3f939f205f79800f6832c7108d3466584f200ff84093c02bd843c3c35204677db3d6bd67dea2680
• Download URL:
  https://stacks.cdc.gov/view/cdc/218690/cdc_218690_DS1.pdf
• File Type:
  [PDF - 62.19 KB ]