Airborne asbestos in buildings

Our plain-English summary of Airborne asbestos in buildings, by R.J. Lee, D.R. Van Orden (Regulatory Toxicology and Pharmacology, 2008).

The study

• Authors: R.J. Lee, D.R. Van Orden
• Journal: Regulatory Toxicology and Pharmacology
• Published: 2008;50(2):218-25
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The concentration of airborne asbestos in buildings nationwide is reported in this study. A total of 3978 indoor samples from 752 buildings, representing nearly 32 man-years of sampling, have been analyzed by transmission electron microscopy. The buildings that were surveyed were the subject of litigation related to suits alleging the general building occupants were exposed to a potential health hazard as a result the presence of asbestos-containing materials (ACM). The average concentration of all airborne asbestos structures was 0.01structures/ml (s/ml) and the average concentration of airborne asbestos > or = 5microm long was 0.00012fibers/ml (f/ml). For all samples, 99.9% of the samples were <0.01 f/ml for fibers longer than 5microm; no building averaged above 0.004f/ml for fibers longer than 5microm. No asbestos was detected in 27% of the buildings and in 90% of the buildings no asbestos was detected that would have been seen optically (> or = 5microm long and > or = 0.25microm wide). Background outdoor concentrations have been reported at 0.0003f/ml > or = 5microm. These results indicate that in-place ACM does not result in elevated airborne asbestos in building atmospheres approaching regulatory levels and that it does not result in a significantly increased risk to building occupants.

In plain English

This study reported airborne asbestos measurements from 752 buildings nationwide (schools, university, public and commercial buildings, and some residences), collected over 10 years. The samples were all those analyzed by the authors' laboratory, RJ Lee Group, for defendants in lawsuits over asbestos-containing materials in buildings. The 3978 indoor samples were examined by transmission electron microscopy. Indoor samples averaged 0.01345 structures/ml for asbestos of all sizes and 0.00012 fibers/ml for fibers at least 5 micrometers long. Outdoor samples averaged 0.00109 structures/ml and 0.00003 fibers/ml. For structures of all sizes, indoor levels were significantly higher than outdoor levels, and schools were higher than other building types. Counting only fibers at least 5 micrometers long, no indoor sample exceeded 0.1 fibers/ml and three exceeded 0.01 fibers/ml. Most structures were chrysotile. Crocidolite and anthophyllite were not detected. Using an EPA risk model, the authors estimated cancer risks of 2.1 per million for people working in schools and 1.1 per million in public/commercial buildings. The authors concluded that in-place asbestos-containing materials did not raise airborne levels approaching regulatory levels or significantly increase occupants' risk.

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: Air sampling survey measuring airborne asbestos concentrations in occupied buildings, with risk estimates calculated from the measurements
• Who was studied: 752 buildings across the US (317 schools, 196 university buildings, 234 public and commercial buildings, plus residences), sampled over a 10-year period. The samples were all those analyzed by RJ Lee Group for defendants in asbestos-in-buildings litigation. There were 3978 indoor samples, 1678 outdoor samples, 111 personal samples and 799 blanks.
• Exposure: Airborne asbestos in buildings containing asbestos-containing materials, measured by transmission electron microscopy. Particles were classified as chrysotile, amphibole or nonasbestos.
• Main results:
  • All indoor samples: average 0.01345 structures/ml for asbestos structures of all sizes and 0.00012 fibers/ml for fibers at least 5 micrometers long.
  • Outdoor samples: average 0.00109 structures/ml (all sizes) and 0.00003 fibers/ml (at least 5 micrometers long).
  • Of all buildings, 27% had no airborne asbestos detected and 86% had no airborne asbestos at least 5 micrometers long.
  • Optically equivalent fibers (those that would be seen by phase contrast microscopy) averaged 0.00008 f/ml in indoor samples and 0.00004 f/ml in outdoor samples. Of all buildings, 90% had none, and 98% of indoor samples had none.
  • For asbestos structures of all sizes, indoor concentrations were significantly higher than outdoor concentrations (p less than 0.0001 for all building types).
  • For asbestos structures of all sizes, schools had significantly higher concentrations than university and public/commercial buildings (p less than 0.0001). Differences for longer fibers were described as marginal.
  • For fibers at least 5 micrometers long, none of the 3978 indoor samples exceeded 0.1 f/ml. Three samples, from different buildings (a physics room, a hallway and a mechanical room), exceeded 0.01 f/ml.
  • Most structures counted were chrysotile (13,107 chrysotile structures versus 363 amphibole structures).
  • Only 8% of building samples contained any amphibole structures. Anthophyllite and crocidolite were not detected.
  • Using the EPA IRIS model, and assuming it applies to low doses, the authors estimated cancer risk of 2.1 per million for people working in schools and 1.1 per million for people working in public/commercial buildings. They estimated 0.4 per million for exposure to outdoor background levels alone.
• The authors' conclusion: The authors concluded that in-place asbestos-containing materials do not raise airborne asbestos in buildings to levels approaching regulatory levels, and do not result in a significantly increased risk to building occupants.
• Limitations the authors state:
  • The study did not test whether airborne levels were linked to factors such as the type or condition of the asbestos-containing material or the type of airflow.
  • The risk estimates assume the sampled buildings represent buildings nationwide, and that risk models built on historical occupational exposures can be extrapolated to these much lower concentrations.
  • Occupancy-level ratings recorded by the survey teams were subjective.
  • The data could not explain the differences in outdoor concentrations between building types.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

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

Related studies

• Airborne asbestos levels in school buildings in Italy — A. Campopiano, S. Casciardi, et al. (2004)
• Composition of heavy metals and airborne fibers in the indoor environment of a building during renovation — M.T. Latif, N.H. Baharudin, et al. (2011)
• Extreme airborne asbestos concentrations in a public building — E. Ganor, A. Fischbein, et al. (1992)
• Airborne concentrations of asbestos in 71 school buildings — M. Corn, K. Crump, et al. (1991)
• Asbestos in New York City public school buildings--public policy: is there a scientific basis? — R. Wilson, A.M. Langer, et al. (1994)
• Re: Asbestos exposures in public and commercial buildings — T.P. Sterling, W.L. Rosenbaum, et al. (1994)

Browse more research in Regulatory Toxicology and Pharmacology, or return to medical research.