Airborne concentrations of asbestos in non-occupational environments

Our plain-English summary of Airborne concentrations of asbestos in non-occupational environments, by M. Corn (The Annals of Occupational Hygiene, 1994).

The study

• Author: M. Corn
• Journal: The Annals of Occupational Hygiene
• Published: 1994;38(4):495-502, 410
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Concentrations of asbestos in air were determined from analysis of samples collected in over 300 buildings involved in litigation. Samples were collected by certified industrial hygienists and analysed in certified laboratories by transmission electron microscopy. Building group mean concentrations of asbestos in building air inhaled by occupants were generally less than 0.0005 f ml-5 > 5 microns (90th percentile). At these concentrations the risk from asbestos exposure would be very low for building occupants. Another data set was obtained from the maintenance logs kept by owners of buildings containing asbestos fireproofing and subject to Operations and Maintenance Programmes to evaluate asbestos inhalation risk to maintenance workers. The logs were kept to document protective measures and maintenance personnel exposures during 1991-1992. Data are presented for one commercial building, which is typical of data for three additional commercial buildings and a medical centre. All samples were evaluated by the NIOSH 1400 protocol for sampling and analysis by phase contrast microscopy. Operations and maintenance precautions to reduce dust emission were modest; they included spraying of ceiling tiles with amended water, HEPA vacuuming tile edges before entry and after tile replacement, respirator usage and careful work. Negative pressure containment was not used. In this building personal exposures in electrical/plumbing work ranged from 0.000 to 0.035 f ml-1 > 5 microns in length (average work time of one job was 118 min); the 8-h TWA was 0.0149 f ml-1 > 5 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

In plain English

This paper, read at a 1993 chrysotile asbestos workshop, reviewed asbestos levels in non-occupational settings. It drew on published reports, including earlier studies by the author, of U.S. buildings in litigation over asbestos removal costs. In 71 schools, the average indoor concentration of fibres longer than 5 micrometres was 0.00024 fibres per cubic centimetre (f/cm3). In outdoor comparison samples, no long asbestos fibres were detected (less than 0.000003 f/cm3). The highest school result was 0.0023 f/cm3. No correlation was found between air levels and type or condition of asbestos-containing material. Long fibres were rarely found in indoor air. In an 18-storey commercial building, maintenance workers' 8-hour average exposures did not exceed the U.S. limit of 0.2 f/cm3. These were measured by a light-microscope method that cannot tell asbestos from other fibres. No worker spent more than 3.31% of work time on tasks with possible asbestos exposure. The review also cited reported levels in outdoor air, water and beverages. The author concluded that building occupants are exposed to low levels and called the workers' 28-week average exposures very low.

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: Review (workshop paper) summarizing published measurements of asbestos in non-occupational settings, including the author's own earlier building studies; not comprehensive
• Who was studied: U.S. buildings involved in litigation for recovery of asbestos removal costs (schools, universities, public and commercial buildings, residences, including 71 schools), maintenance workers in an 18-storey commercial building (May to November 1991), plus reported data on outdoor air, water and beverages
• Exposure: Airborne asbestos in buildings (fibres longer than 5 micrometres; chrysotile and amphibole structures, analysed by transmission electron microscopy) and maintenance workers' exposures during tasks such as ceiling removal/installation, electrical/plumbing, HVAC work, removal/encapsulation and running cable (measured by phase contrast microscopy)
• Main results:
  • Across 71 schools, the average indoor concentration of fibres over 5 micrometres long was 0.00024 f/cm3. This was significantly higher than in the outdoor samples taken for comparison, where no long asbestos fibres were detected and the concentration was less than 0.000003 f/cm3.
  • Five per cent of the school mean indoor concentrations exceeded 0.0014 f/cm3; the highest was 0.0023 f/cm3
  • Counting all structures, schools averaged 18 structures per litre for chrysotile and 0.66 for amphibole asbestos, compared with 2 structures per litre for outdoor asbestos
  • In the schools, no correlation was found between air concentration and type or condition of asbestos-containing material, among other factors; there was a correlation with the state in which the school was located
  • Fibres longer than 5 micrometres were rarely found suspended in indoor air
  • In the 18-storey commercial building, maintenance workers' 8-hour TWA exposures did not exceed the U.S. OSHA permissible exposure limit of 0.2 f/cm3 for fibres longer than 5 micrometres. Similar results were reported for four other buildings, one a medical center.
  • The maximum share of work time any maintenance worker spent on tasks related to possible asbestos exposure was 3.31%
  • Cited reports: asbestos in remote outdoor locations was less than 1 ng per cubic metre. In urban areas, up to 0.002 f/cm3 longer than 5 micrometres had been reported. Water concentrations were generally less than 1 million fibres per litre (MFL), with 100 MFL reported where water came from eroded natural asbestos deposits.
  • Cited report from 1971: asbestos was found in U.S. and Canadian beer and wine at 1.1 to 6.6 MFL (all sizes), from asbestos clarification filters
• The authors' conclusion: The author concluded that building occupants are exposed to low levels of asbestos in air, and that the maintenance workers' 28-week TWA exposures were very low
• Limitations the authors state:
  • The author states the presentation is not comprehensive and does not include all published results
  • The maintenance worker data were based on phase contrast microscopy, which does not distinguish asbestos from non-asbestos fibres
  • The task-specific 8-hour TWAs assume exposure only during the sample period
  • Results from different analytical methods are not directly comparable

Topics

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

Medical terms in this study, explained in our Lexicon: Transmission Electron Microscopy (TEM), Asbestos Exposure, NIOSH, phase contrast microscopy (PCM), Respirator.

Related studies

• Mass concentrations of airborne asbestos in the non-occupational environment--a preliminary report of U.K. measurements — G.J. Burdett, J.M. le Guen, et al. (1984)
• Airborne exposure concentrations during asbestos abatement of ceiling and wall plaster — J.H. Lange, K.W. Thomulka (2002)
• 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)
• Comparison of direct and indirect methods of measuring airborne chrysotile fibre concentration — C. Eypert-Blaison, S. Veissiere, et al. (2010)
• Airborne fiber concentration and size distribution of mineral fibers in area with serpentinite outcrops in Aichi prefecture, Japan — K. Sakai, N. Hisanaga, et al. (2001)
• Interpretation of airborne asbestos measurements — J. Chesson, J.D. Rench, et al. (1990)

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