A study of personal and area airborne asbestos concentrations during asbestos abatement: a statistical evaluation of fibre concentration data

Our plain-English summary of A study of personal and area airborne asbestos concentrations during asbestos abatement: a statistical evaluation of fibre concentration data, by J.H. Lange, P.R. Lange, T.K. Reinhard, et al (The Annals of Occupational Hygiene, 1996).

The study

• Authors: J.H. Lange, P.R. Lange, T.K. Reinhard, K.W. Thomulka
• Journal: The Annals of Occupational Hygiene
• Published: 1996;40(4):449-66
• Cited by: 31 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Data were collected and analysed on airborne concentrations of asbestos generated by abatement of different asbestos-containing materials using various removal practices. Airborne concentrations of asbestos are dramatically variable among the types of asbestos-containing material being abated. Abatement practices evaluated in this study were removal of boiler/pipe insulation in a crawl space, ceiling tile, transite, floor tile/mastic with traditional methods, and mastic removal with a high-efficiency particulate air filter blast track (shot-blast) machine. In general, abatement of boiler and pipe insulation produces the highest airborne fibre levels, while abatement of floor tile and mastic was observed to be the lowest. A comparison of matched personal and area samples was not significantly different, and exhibited a good correlation using regression analysis. After adjusting data for outliers, personal sample fibre concentrations were greater than area sample fibre concentrations. Statistical analysis and sample distribution of airborne asbestos concentrations appear to be best represented in a logarithmic form. Area sample fibre concentrations were shown in this study to have a larger variability than personal measurements. Evaluation of outliers in fibre concentration data and the ability of these values to skew sample populations is presented. The use of personal and area samples in determining exposure, selecting personal protective equipment and its historical relevance as related to future abatement projects is discussed.

In plain English

This study analysed air samples taken during routine asbestos removal projects. The authors collected the records after the project supervisors had finished their reports. Samples came from removal of boiler and pipe insulation in a crawl space, ceiling tile, outdoor transite, floor tile and mastic by traditional methods, and mastic by a shot-blast machine. Chrysotile was the main asbestos type in each material. Fibres were counted by phase-contrast microscopy, which counts all fibres. Boiler and pipe insulation removal gave the highest fibre counts, though the authors called this difference only descriptive. Mastic removal by either method appeared to release little, if any, fibre. Every practice except floor tile/mastic and shot-blast removal had some samples numerically above the OSHA limit, but these were not time-weighted averages. For boiler/pipe work, matched personal (breathing-zone) and area samples were not significantly different (P = 0.45). The authors reported a correlation statistic of 0.61 between the two methods, which they called a good relationship. The scanned text does not make clear whether this figure is r or r squared. Area samples were more variable. After outliers were excluded, personal samples were higher. The authors concluded that area samples can help predict personal exposure but cannot completely replace the personal sampling OSHA requires. They added that using area samples alone to determine individual exposure must be viewed with caution.

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 historical air-monitoring data (personal and area samples) collected during asbestos abatement projects, gathered after the projects were completed
• Who was studied: Air samples from asbestos abatement projects selected for good sampling documentation. Table 1 lists: boiler/pipe insulation in a crawl space, 102 area samples plus 42 area and 42 personal samples matched to each other; ceiling tile in a mini-containment, 11 area and 9 personal samples; transite, 41 personal samples; floor tile by traditional methods, 14 area samples; mastic by blast track, 4 area samples. The text does not say where the projects took place or in what years, only that the work was done in summer. The matched personal/area comparison was limited to boiler/pipe insulation removal.
• Exposure: Airborne fibres released during removal of boiler/pipe insulation, ceiling tile, transite, floor tile/mastic (traditional solvent methods) and mastic (HEPA shot-blast machine). Chrysotile was the predominant asbestos type, at approximately 35% (boiler/pipe insulation), 3% (floor tile), 3% (mastic), 30% (transite) and 25% (ceiling tile). Fibres were counted by phase-contrast microscopy (NIOSH 7400 method).
• Main results:
  • Removal of pipe/boiler insulation gave the highest fibre counts on both personal and area samples; the authors described this difference as only descriptive.
  • Arithmetic and geometric mean concentrations for pipe/boiler insulation removal were above the numerical value of the OSHA permissible exposure limit (0.1 fibres per cubic centimetre). These were not time-weighted averages.
  • Every work practice except floor tile/mastic removal and the shot-blast technique had samples numerically above the OSHA limit, including some transite (outdoor) removal samples.
  • Three unmatched area samples from pipe/boiler abatement exceeded the level (greater than 1.0 fibres per cubic centimetre) that OSHA designates for a half-mask air-purifying respirator.
  • Mastic removal, by shot-blaster or by traditional solvent methods, appeared to cause little, if any, fibre release.
  • Matched personal and area samples from boiler/pipe insulation removal were not significantly different (P = 0.45).
  • The authors reported a correlation statistic of 0.61 between the two sampling methods (log-transformed values) and described it as a good relationship. The symbol is printed in the scanned text as "r’", so it is unclear whether the figure is r or r squared.
  • Area samples were more variable than personal samples. Standard deviations were 0.231 (area) and 0.197 (personal) for matched pipe/boiler samples, and 0.097 (area) and 0.049 (personal) for ceiling tile samples.
  • In the matched pipe/boiler samples, the two lowest personal values and the lowest area value were outliers. All were below the detection limit. With them excluded, the personal mean concentration was larger than the matched area mean; before exclusion, area means had been higher.
  • Airborne fibre concentrations were not normally distributed and fit a logarithmic (log-normal) form.
• The authors' conclusion: The authors concluded that area and personal sample concentrations correlated well and were not significantly different. After adjustment for outliers, personal samples appeared higher. Area samples could serve as an additional predictor of exposure, but this will not eliminate or substitute completely the personal sampling required for OSHA compliance. Matched area samples were more variable, and the use of area samples alone in determining individual exposure must be viewed with caution. The authors also concluded that airborne asbestos concentrations appear log-normally distributed and that both arithmetic and geometric means should be reported.
• Limitations the authors state:
  • The reported concentrations are not time-weighted averages, so they are not always directly comparable with the OSHA limit.
  • The ceiling tile results rest on a small number of samples, and those samples were not collected as matched pairs.
  • Phase-contrast microscopy counts all fibres, so non-asbestos fibres (for example cellulose) may contribute to the counts.
  • The selection of matched samples may be a source of bias in the correlation and significance analysis.

Topics

Medical terms in this study, explained in our Lexicon: Abatement, Asbestos-Containing Material (ACM), Pipe Covering, Transite, Personal Breathing Zone Sample.

Related studies

• Personal airborne asbestos exposure levels associated with various types of abatement — J.H. Lange, K.W. Thomulka, et al. (2006)
• Area and personal airborne exposure during abatement of asbestos-containing roofing material — J.H. Lange, K.W. Thomulka (2000)
• Personal and static sample measurements of asbestos fibres during two abatement projects — A. Dufresne, C. Dion, et al. (2009)
• Statistical analysis of data on airborne asbestos levels collected in an EPA survey of public buildings — K.S. Crump, D.B. Farrar (1989)
• Personal exposure during abatement of various asbestos-containing materials in the same work area — J.H. Lange, K.W. Thomulka, et al. (2005)
• Spatio-seasonal variation of airborne asbestos concentration in urban areas of Shiraz, Iran — M.K. Fathi Fathabadi, A. Abdolahnejad, et al. (2017)

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