Airborne asbestos in Colorado public schools

Our plain-English summary of Airborne asbestos in Colorado public schools, by D.A. Chadwick, R.M. Buchan, H.J. Beaulieu (Environmental Research, 1985).

The study

• Authors: D.A. Chadwick, R.M. Buchan, H.J. Beaulieu
• Journal: Environmental Research
• Published: 1985;36(1):1-13
• Cited by: 1 article, 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. 004396).

Abstract

Levels of airborne asbestos for six Colorado public school facilities with sprayed-on asbestos materials were documented using three analytical techniques. Phase contrast microscopy showed levels up to the thousandths of a fiber per cubic centimeter (f/cc), scanning electron microscopy (SEM) up to the hundredths of a f/cc, and transmission electron microscopy coupled to selected area electron diffraction and energy dispersive X-ray analysis (TEM-SAED-EDXA) up to the tenths of an asbestos f/cc. Phase contrast microscopy was found to be an inadequate analytical technique for documenting the levels of airborne asbestos fibers in the schools: only large fibers which were not embedded in the filter were counted, and asbestos fibers were not distinguished from nonasbestos.

In plain English

The authors measured airborne fibers in six Colorado public school facilities that had sprayed-on asbestos material, in winter and spring 1981. Bulk samples contained chrysotile, and one sample also contained amosite. All indoor and outdoor filters were analyzed by phase contrast (optical) microscopy. Fourteen indoor samples were analyzed by scanning electron microscopy (SEM). Nine indoor and five outdoor samples were analyzed by transmission electron microscopy (TEM) combined with methods that identify asbestos. By phase contrast, 57 filters were below the detectable limit, and all detectable concentrations were in the thousandths of a fiber per cubic centimeter (f/cc). One filter counted at 23,000 fibers by phase contrast showed only cellulose under polarized light. SEM concentrations at sample locations ranged up to 0.059 f/cc. By TEM, building locations minus the outdoor level ranged up to 0.739 asbestos f/cc. Building averages minus outdoor ranged from 0.001 to 0.379 asbestos f/cc. The building-versus-outdoor difference was not statistically significant (P value 0.08). The authors did not consider this strong evidence of no difference. The authors concluded that phase contrast microscopy was inadequate for documenting airborne asbestos in the schools. They noted that sample preparation might have broken fibers.

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: Environmental air sampling survey comparing three filter analysis techniques
• Who was studied: Six Colorado public school facilities containing sprayed-on asbestos materials, sampled in winter and spring 1981. Two to five indoor air pumps were used per building, plus one outdoor pump.
• Exposure: Sprayed-on asbestos material on ceilings, walls or structural beams. Bulk samples contained only chrysotile, except one Facility 5 (Level 4) sample that also contained amosite.
• Main results:
  • Phase contrast microscopy (all building and outdoor samples): 57 sample filters were below the detectable limit of 4500 fibers per filter. The remaining filters had 5,000 to 24,000 fibers per filter, and all detectable concentrations were in the thousandths of a fiber per cubic centimeter.
  • One filter counted at 23,000 fibers by phase contrast showed only cellulose and no asbestos fibers under polarized light microscopy.
  • SEM (14 building samples; outdoor samples were not analyzed by SEM): concentrations by sample location ranged from less than detectable to 0.059 f/cc. Facility averages ranged from less than reportable to 0.025 f/cc.
  • TEM-SAED-EDXA (9 building and 5 outdoor samples from five facilities): building sample locations minus the outdoor level ranged from less than the outdoor concentration to 0.739 asbestos f/cc.
  • TEM-SAED-EDXA: building averages minus the outdoor measurement ranged from 0.001 to 0.379 asbestos f/cc.
  • The highest building location was the Facility 4 classroom. One duplicate filter measured 0.782 asbestos f/cc by TEM, and the other measured 0.059 f/cc by SEM.
  • Statistical testing of TEM results: concentrations differed significantly between facilities (P value 0.03).
  • The difference between building and outdoor concentrations was not statistically significant (P value 0.08). The authors did not consider this a strong indicator that there was no difference, and further analysis indicated that the building-outdoor difference was consistent across facilities.
• The authors' conclusion: The authors concluded that phase contrast microscopy was an inadequate tool for documenting airborne asbestos in the schools. It did not distinguish asbestos from nonasbestos fibers, and it missed short, thin, or filter-embedded fibers.
• Limitations the authors state:
  • The study was not designed specifically to compare the three analytical techniques.
  • Filter ashing, sonication and redeposition for electron microscopy may have broken fibers into smaller pieces.
  • No method was available to determine the error in the electron microscopy counts.
  • Differences in filter preparation and counting criteria made comparison with other studies impossible.
  • The sample population was small, and the single Facility 6 building concentration was used twice in the statistical analysis.

Topics

Medical terms in this study, explained in our Lexicon: phase contrast microscopy (PCM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED).

Related studies

• Asbestos in Colorado schools — C.A. Baldwin, H.J. Beaulieu, et al. (1982)
• Airborne Asbestos Exposures from Warm Air Heating Systems in Schools — G.J. Burdett, K. Dewberry, et al. (2016)
• Asbestos contamination in United States schools from use of asbestos surfacing materials — W.J. Nicholson, E.J. Swoszowski, et al. (1979)
• Exposure to Amosite-Containing Ceiling Boards in a Public School in Switzerland: A Case Study — D. Vernez, O. Duperrex, et al. (2019)
• Asbestos-related disease in public school custodians — L.C. Oliver, N.L. Sprince, et al. (1991)
• A radiographic survey of public school building maintenance and custodial employees — H.A. Anderson, L.P. Hanrahan, et al. (1992)

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