Variability in Respiratory Protection and the Assigned Protection Factor

Details

• Personal Author:
  Neuhaus J ; Nicas M
• Description:
  The workplace protection factor (WPF) for a given respirator wearer shows substantial variability from wearing to wearing; this variability is commonly assumed to be lognormal in nature. Further, when multiple WPFs are measured for each of multiple wearers, the aggregated WPFs appear to follow a lognormal distribution. However, the analysis typically applied to WPF data does not apportion variability within versus between wearers. We present an analytical framework based on a normal random effects model of log-transformed penetration P values (P = 1/WPF). Data from seven studies of negative-pressure air-purifying half-mask respirators, and from two studies of hemlet-and-visor type powered air-purifying respirators were analyzed by the method of maximum likelihood in the context of the model. More specifically, analyses were performed for log-transformed P values and for logit-transformed P values. Parameter estimates included within-wearer and between-wearer variance components. In general, the within-wearer component dominated the between-wearer component. We also propose a method for establishing an assigned protection factor, APF, that properly accounts for these variance components. Our method provides an APF satisfying two criteria: (1) for a given wearer, an acceptable WPF distribution has no more than 5% of WPFs below the APF value; and (2) for a wearer population, no more than 5% of wearers have unacceptable WPF distributions. The method incorporates an one-sided confidence limit to account for sampling variability. Alternative confidence limits were computed based on large sample variance estimates of random effects model parameters versus a bootstrap method. In general, there was good agreement between the APF values based on log-transformed versus logit-transformed P data, and between APF values based on the large sample variance estimates versus the bootstrap method. Based on large sample variance estimates for the logit-transformed P data from the seven half-mask studies, estimated APFs ranged from 1.4 to 250, with 5/7 studies yielding an APF <= 5.3. Given these results and related considerations, we recommend that the current half-mask APF be reduced from 10 to 5. [Description provided by NIOSH]
• Subjects:
  Air Pollutants, Occupational Air Pollution, Indoor Bacteria Dust Microbiology Occupational Health Personal Protective Equipment Respiratory Protective Devices Respiratory System Safety
• Keywords:
  Air-contamination Air-purification Air-purifiers Air-purifying-respirators Bacterial-dusts Microorganisms Models Personal-protective-equipment Protective-equipment Respiration Respirators Respiratory-protection Respiratory-protective-equipment Statistical-analysis

  More +
• ISSN:
  1545-9624
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  California ; OSHA Region 9
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  99-109
• Volume:
  1
• Issue:
  2
• NIOSHTIC Number:
  nn:20029310
• Citation:
  J Occup Environ Hyg 2004 Feb; 1(2):99-109
• Contact Point Address:
  Mark Nicas, PhD, Center for Occupational and Environmental Health, School of Public Health, University of California, Berkeley, California 94720
• Email:
  mnicas@berkeley.edu
• Federal Fiscal Year:
  2004
• NORA Priority Area:
  Research Tools and Approaches: Control Technology and Personal Protective Equipment
• Performing Organization:
  University of California, Berkeley, California
• Peer Reviewed:
  True
• Start Date:
  19990701
• Source Full Name:
  Journal of Occupational and Environmental Hygiene
• End Date:
  20021230
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:dcd3031cf79db6d37b5dfe6a7b90b6949a243a3da988f7d0f4961ddeed38e46f1be0f673c61263b7af7897440cf30ed78f6bf9dff5f15f6cf6a34dcf0377be30
• Download URL:
  https://stacks.cdc.gov/view/cdc/190329/cdc_190329_DS1.pdf
• File Type:
  [PDF - 327.82 KB ]