Use of a cowl in asbestos air sampling

Our plain-English summary of Use of a cowl in asbestos air sampling, by K.L. Knight, D.M. Bloor, F. Miller (The Annals of Occupational Hygiene, 1985).

The study

• Authors: K.L. Knight, D.M. Bloor, F. Miller
• Journal: The Annals of Occupational Hygiene
• Published: 1985;29(2):289-91
• Type of article: Letter
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

This letter reported a comparison of cowled and uncowled filter holders for personal asbestos air sampling. The European Reference Method (ERM) required an open-face filter holder fitted with an electrically conductive cylindrical cowl. The authors noted that little work had compared it with earlier uncowled designs, and that Speight and Marsh had reported a substantial difference when sampling amosite insulation fibres. In an asbestos cement factory, cowled and plastic non-cowled holders were mounted side by side on the shoulder of a man transferring baled chrysotile asbestos into a rod mill. Samples were taken concurrently with identical backing plates and orientation, inner and outer positions were alternated, and counters did not know the holder type or position. Sampling periods were varied to give fibre densities of around 100-500 fibres per mm2, and flow rates were measured at the start, middle and end. Filters were prepared and counted by the ERM, with repeated counts. Of 20 samples, one was lost, and nine pairs of standardized fibre densities were analysed. A paired Student's t-test (t = 0.0238; tabular t 2.306 for 8 degrees of freedom) showed no significant difference at the 5% level. An F-test (F = 1.16; tabular F 4.43) showed no significant difference in variances. The authors concluded that, for airborne chrysotile, cowled holders made no practical difference to results. This differed from Speight and Marsh's experience with amosite.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This letter to the editor described a field trial comparing open-face air-sampling filter holders fitted with a cylindrical cowl, which the European Reference Method requires, with plastic holders without a cowl. The authors noted that an earlier letter by other researchers had reported a substantial difference between cowled and uncowled filters when sampling amosite insulation fibres. In this trial, the two holder types were worn side by side on the shoulder of a man transferring baled chrysotile asbestos into a rod mill at an asbestos cement factory. Samples were taken at the same time, and the holder positions were alternated. The people counting fibres did not know which holder each sample came from. One sample was lost, leaving 9 pairs for analysis. A t-test found no significant difference at the 5% level between the standardized fibre densities from the two holder types. An F-test found no significant difference in how variable the two sets of results were. The authors concluded that, when measuring airborne chrysotile, cowled holders made no practical difference to the results. They noted that this differed from the earlier amosite experience.

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: Letter to the editor reporting a field experiment: side-by-side personal air sampling comparing cowled and uncowled (plastic) filter holders, with paired statistical comparison
• Who was studied: Personal air samples from the work environment of one man in an asbestos cement factory. Twenty sample numbers are listed, one sample was lost, and 9 pairs were analyzed. Date and location are not given.
• Exposure: Airborne chrysotile asbestos from transferring baled chrysotile into a rod mill. Samples were collected to give fibre densities of around 100 to 500 fibres per square millimetre.
• Main results:
  • A paired Student's t-test found no significant difference at the 5% probability level between standardized fibre densities from cowled and non-cowled holders
  • The calculated t was 0.0238, below the tabular value printed for 8 degrees of freedom (printed as "2306", read as 2.306)
  • An F-test found no significant difference in variances between the cowled and non-cowled samples
  • Variance of standardized density was 20561.646 for cowled holders (n = 9) and 23886.244 for non-cowled holders (n = 9). F was 1.16169, below the tabular F of 4.43 for 8 and 8 degrees of freedom at p = 0.05.
  • One of the samples was lost
• The authors' conclusion: The authors concluded that when measuring airborne chrysotile asbestos fibre concentrations, cowled filter holders made no practical difference to the results. They noted this differed from the experience of Speight and Marsh with amosite insulation fibres.

Topics

Medical terms in this study, explained in our Lexicon: Air Sampling, Amosite, Asbestos-Cement, Chrysotile.

Related studies

• Efficiency of sampling and analysis of asbestos fibers on filter media: implications for exposure assessment — D.A. Vallero, J.R. Kominsky, et al. (2009)
• The influence of external aerodymanic factors on the measurement of the airborne concentration of asbestos fibres by the membrane filter method — A.M. Johnston, A.D. Jones, et al. (1982)
• Comparison of a fibrous aerosol monitor (FAM) with the membrane filter method for measuring airborne asbestos concentrations — P.J. Iles, T. Shenton-Taylor (1986)
• A comparison of fibre counting stopping rules in the application of the membrane filter method — N.P. Crawford, W.M. Maclaren, et al. (1987)
• The challenges of applying an Activity-Based Sampling methodology to estimate the cancer risk associated with asbestos contaminated landfilled zones — M.F. Cely-García, B. Lysaniuk, et al. (2020)
• Exposure of UK industrial plumbers to asbestos, Part II: Awareness and responses of plumbers to working with asbestos during a survey in parallel with personal sampling — D. Bard, G. Burdett (2007)

Browse more research in The Annals of Occupational Hygiene, or return to medical research.