Statistical analysis of data on airborne asbestos levels collected in an EPA survey of public buildings

Our plain-English summary of Statistical analysis of data on airborne asbestos levels collected in an EPA survey of public buildings, by K.S. Crump, D.B. Farrar (Regulatory Toxicology and Pharmacology, 1989).

The study

• Authors: K.S. Crump, D.B. Farrar
• Journal: Regulatory Toxicology and Pharmacology
• Published: 1989;10(1):51-62
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004734).

Abstract

Data from a recent EPA study of airborne asbestos levels in 49 buildings occupied by the General Services Administration (GSA) are statistically analyzed. The study focuses on differences between indoor and outdoor levels, and on differences among buildings with no asbestos-containing material (ACM) (6 buildings), buildings with ACM generally in good condition (6 buildings), and buildings containing damaged ACM (37 buildings). Seven indoor samples and a single outdoor sample were collected from most buildings and analyzed by TEM (transmission electron microscopy) using a direct preparation method. No statistically significant differences were detected in asbestos levels between indoors and outdoors or among the three categories of buildings. The average indoor concentration of asbestos was 0.00073 fibers/cc (f/cc) for all fibers and 0.00007 f/cc for fibers 5 microns or longer. The current OSHA occupational standard is 0.2 f/cc for fibers 5 microns or longer as measured by phase-contrast microscopy.

In plain English

The authors statistically analyzed 1987 EPA air-sampling data from 49 General Services Administration public buildings. Six had no asbestos-containing material, six had such material in good condition, and 37 had damaged material. Most buildings had seven indoor samples and one outdoor sample (387 in all), examined by transmission electron microscopy; 100 asbestos fibers were found. The authors found no statistically significant differences between indoor and outdoor levels, or among the three building groups, and concluded the data did not indicate such differences. The average indoor level was 0.00073 fibers per cc for all asbestos fibers and 0.00007 for fibers 5 micrometers or longer, which the authors called more than 2500 times below the OSHA workplace standard of 0.2 (measured by phase-contrast microscopy). An earlier analysis of the same data reported a significantly higher concentration of total fibers in damaged-material than no-asbestos buildings, though the damaged-material average was lower. Correcting that analysis's randomization test but keeping its median-based statistic, the authors found no significant difference (P = 0.10). With the Mantel-Haenszel statistic they considered more appropriate, P was 0.75.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Statistical analysis of existing air-sampling data from an EPA survey of buildings, using randomization (Mantel-Haenszel) tests
• Who was studied: 49 public buildings owned by the General Services Administration in five U.S. regions (Washington, D.C., Kansas City, New York City, California and Denver), with 387 air samples collected in spring and early summer 1987
• Exposure: Airborne asbestos (classified as chrysotile or amphibole) inside and outside buildings in three groups: no asbestos-containing material (6 buildings), such material in good condition (6 buildings), and damaged material (37 buildings)
• Main results:
  • Across the 387 non-blank samples, 100 asbestos fibers were found
  • No statistically significant differences in airborne asbestos levels between indoors and outdoors, or among the three building groups
  • Average indoor concentration (all 49 buildings): 0.00073 f/cc for all asbestos fibers and 0.00007 f/cc for fibers 5 micrometers or longer
  • The authors stated that the average indoor concentration of fibers longer than 5 micrometers was more than 2500 times lower than the OSHA standard of 0.2 f/cc. The article notes the OSHA standard is measured by phase-contrast microscopy, while this study used transmission electron microscopy
  • Mean indoor total asbestos concentration was 0.00073 f/cc in damaged-material (Category 3) buildings, lower than the 0.00099 f/cc in no-asbestos (Category 1) buildings
  • An earlier analysis of the same data by Battelle et al. had reported a significantly higher concentration of total fibers in Category 3 (damaged-material) buildings than in Category 1 (no-asbestos) buildings
  • Repeating the Battelle et al. analysis with what they described as an appropriate randomization test, but still using the difference in medians as the test statistic, the authors found no significant difference between Category 1 and Category 3 buildings (P = 0.10)
  • Using the Mantel-Haenszel test statistic, which the authors considered more appropriate, the same Category 3 versus Category 1 comparison gave P = 0.75
  • The highest concentration of fibers 5 micrometers or longer in any single sample was 0.004 f/cc
• The authors' conclusion: The authors concluded that the EPA study data did not indicate higher levels indoors than outdoors, or differences in asbestos levels among buildings with no asbestos-containing material, material in good condition, or damaged material
• Limitations the authors state:
  • The authors note the small number of fibers found in the study (raised when comparing measured and estimated concentrations)

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Containing Material (ACM), Transmission Electron Microscopy (TEM), OSHA.

Related studies

• A study of personal and area airborne asbestos concentrations during asbestos abatement: a statistical evaluation of fibre concentration data — J.H. Lange, P.R. Lange, et al. (1996)
• Airborne concentrations of asbestos in 71 school buildings — M. Corn, K. Crump, et al. (1991)
• Airborne asbestos in public buildings — J. Chesson, J. Hatfield, et al. (1990)
• Personal airborne asbestos exposure levels associated with various types of abatement — J.H. Lange, K.W. Thomulka, et al. (2006)
• A radiographic survey of public school building maintenance and custodial employees — H.A. Anderson, L.P. Hanrahan, et al. (1992)
• Asbestos and other fibre levels in buildings — S. Altree-Williams, J.S. Preston (1985)

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