Exposure of UK industrial plumbers to asbestos, Part I: Monitoring of exposure using personal passive samplers

Our plain-English summary of Exposure of UK industrial plumbers to asbestos, Part I: Monitoring of exposure using personal passive samplers, by G. Burdett, D. Bard (The Annals of Occupational Hygiene, 2007).

The study

• Authors: G. Burdett, D. Bard
• Journal: The Annals of Occupational Hygiene
• Published: 2007;51(2):121-30
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Epidemiological data suggest that there has been and may continue to be a significant risk to maintenance workers, who through their work may disturb asbestos-containing materials (ACM). The sampling and assessment of maintenance workers' exposure is a particular problem because they may not know that they are working with ACM. A strategy to monitor their true exposure has been developed and applied to one group of workers. The asbestos exposure of industrial plumbers was measured using personal passive samplers developed at the Health and Safety Laboratory (HSL). The light-weight samplers, which collect particles by electrostatic attraction, are simple to use and do not require prior knowledge that asbestos is to be disturbed as does conventional sampling. The samplers were issued by post and analysed, after return, using transmission electron microscopy (TEM). The strategy was found to be a reasonably efficient and cost-effective way to obtain data on maintenance worker's exposure to asbestos. The results of the TEM analysis of the passive samplers showed that the percentage of workers exposed to >5 microm long asbestos fibres was 62% in Round 1 and 58% in Round 2. For phase contrast microscopy equivalent (PCME) asbestos fibres, the values were 46 and 29%, respectively. The three samples with the highest numbers of fibres were followed up and were associated with plumbers working in areas which had supposedly been stripped of asbestos just prior to their starting work, suggesting that poor removal, clean-up and clearance practice presents a significant part of the risk to plumbers. Although flow rates will vary with conditions and time, an approximate average sampling rate from previous comparisons was used to calculate the concentration. This gave an average exposure to regulated PCME fibres of 0.009 f ml-1 for amphibole asbestos and 0.049 f ml-1 for chrysotile. The calculate risk based on the PCME fibre types collected and their estimated concentrations, showed that the risk from airborne amphibole fibres was approximately 6 times greater than from chrysotile fibres. If representative, the estimated lifetime risk of death from an asbestos related cancer for an exposure from age 20 for 40 years would be 68 per 100,000, which equates to an annual risk of death of the order of 10 per million.

In plain English

The authors surveyed asbestos exposure among UK industrial plumbers using passive samplers worn during a working week, and analysed the collected dust by transmission electron microscopy. Plumbers registered with the UK Institute of Plumbers were invited by letter. 50 samplers were returned in Round 1 and 24 in a second round. Asbestos fibres longer than 5 micrometres were found on 62% of Round 1 samplers and 58% of Round 2 samplers. Fibres of the regulated (PCME) size were found on 46% and 29%. Most fibres were chrysotile, amphiboles were mainly amosite, and no crocidolite was found. The three samples with the most fibres came from plumbers working in areas that had supposedly been stripped of asbestos. Using an assumed sampling rate, the average PCME concentration across both rounds was 0.009 fibres per ml for amphibole and 0.049 for chrysotile. The authors estimated a lifetime risk of death from asbestos-related cancer of 68 per 100 000 for 40 years of continuous exposure from age 20, with the amphibole risk some 6 times that of chrysotile. They stressed that these estimates rest on an assumed sampling rate.

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: Exposure-monitoring survey in two rounds, using personal passive samplers analysed by transmission electron microscopy (TEM)
• Who was studied: Industrial plumbers registered with the UK Institute of Plumbers. 400 of the 800 registered were invited by letter, excluding Northern Ireland-based companies. The survey was a baseline carried out before the new duty to manage asbestos came into force in 2004.
• Exposure: Airborne asbestos collected over a working week during the plumbers' normal work. Fibres were counted as asbestos fibres longer than 5 micrometres and as phase contrast microscopy equivalent (PCME) fibres, and typed as chrysotile or amphibole asbestos.
• Main results:
  • Response: in Round 1, 96 samplers were sent to willing plumbers and 50 (52%) were returned and analysed.
  • Response: in Round 2, 24 samplers (48%) were returned and analysed.
  • Round 1: 31 of the 50 samplers (62%) had asbestos fibres longer than 5 micrometres.
  • Round 1: 23 samplers (46%) had PCME asbestos fibres.
  • Round 2: 14 of 24 samplers (58%) had at least one asbestos fibre longer than 5 micrometres.
  • Round 2: 7 samplers (29%) had PCME asbestos fibres.
  • Fibre types in Round 1: of 873 asbestos fibres longer than 5 micrometres, 96.7% were chrysotile and 3.3% were regulated amphibole asbestos.
  • No crocidolite fibres were found.
  • Round 1 average concentration of asbestos fibres longer than 5 micrometres was 1.84 structures per ml. This average was heavily influenced by a few samples with many fine chrysotile fibres.
  • Round 2 concentrations were much lower than Round 1: an average of 0.07 structures per ml for asbestos fibres longer than 5 micrometres.
  • The three highest samples were followed up. They came from plumbers working in areas that had supposedly been stripped of asbestos before they started work.
  • Average PCME concentration across both rounds (using an assumed sampling rate) was 0.009 f/ml for amphibole (treated as amosite) and 0.049 f/ml for chrysotile. These gave estimated lifetime risks of 58 per 100 000 and 10.1 per 100 000 respectively, for 40 years of continuous exposure from age 20.
  • Combined estimated lifetime risk of death from an asbestos-related cancer was 68 per 100 000, for the worst-case exposure of 40 years continuous from age 20.
  • This equated to an estimated annual risk of death from asbestos-related cancer (mesothelioma and lung cancer) of the order of 10 per million.
  • The authors described this risk level as significant but one that would be regarded as 'tolerable' in published HSE guidance.
  • The estimated risk to these plumbers was some 6 times greater from amphibole (mainly amosite) asbestos than from chrysotile.
• The authors' conclusion: The authors concluded that the postal passive-sampler strategy was a reasonably efficient and cost-effective way to obtain data on maintenance workers' exposure to asbestos.
• Limitations the authors state:
  • Concentration and risk estimates rest on an assumed sampling rate, which varies with conditions and time, and on many other assumptions about long-term exposure.
  • Further field calibration against conventional pump sampling is needed to validate the average sampling rate.
  • In an unsupervised postal survey, samples could have been tampered with. This is harder to detect with the indirect preparation method used. An outlier was nonetheless included in the averages.
  • Round 2 may have been biased: Round 1 results and leaflets were sent back to participants, and publicity about new legislation may also have had an impact.
  • With such a small sample, differences between rounds could simply reflect whether asbestos-containing material was present to be disturbed.
  • Low fibre counts have very poor precision.
  • The indirect sample preparation method substantially increased the counts of asbestos fibres longer than 5 micrometres, by splitting fibres off clumps and bundles.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos-Containing Material (ACM), Asbestos Exposure, Transmission Electron Microscopy (TEM), phase contrast microscopy (PCM), Amphibole Asbestos, Chrysotile, Amphibole Group.

Related studies

• 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)
• Industrial-grade talc exposure and the risk of mesothelioma — B. Price (2010)
• Personal and static sample measurements of asbestos fibres during two abatement projects — A. Dufresne, C. Dion, et al. (2009)
• Estimation of personal exposure to asbestos of brake repair workers — M.F. Cely-García, F.C. Curriero, et al. (2017)
• Study of the count-to-mass conversion factor for asbestos fibres in samples collected at the emissions of three industrial plants — S. Puledda, A. Marconi (1991)
• An evaluation of the risks of lung cancer and mesothelioma from exposure to amphibole cleavage fragments — J.F. Gamble, G.W. Gibbs (2008)

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