Asbestos exposure among construction workers during demolition of old houses in Tehran, Iran

Our plain-English summary of Asbestos exposure among construction workers during demolition of old houses in Tehran, Iran, by H. Kakooei, M. Normohammadi (Industrial Health, 2014).

The study

• Authors: H. Kakooei, M. Normohammadi
• Journal: Industrial Health
• Published: 2014;52(1):71-7
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Air quality in demolition practices has seldom been evaluated in Iran. Accordingly, we evaluated asbestos exposure among Tehran construction workers during the demolition of old houses. To identify possible sources of asbestos exposure, including thermal insulations, chimney pipes and cement sheets, were all sampled. This study also were taken the personal air samples to evaluate any asbestos exposure during the demolition. The asbestos fibers found in the samples were analyzed by phase-contrast optical microscopy (PCM), scanning electron microscopy (SEM) equipped with an energy dispersive X-ray analysis, and polarized light microscopy (PLM) methods. Personal monitoring of asbestos fiber levels indicated a range from 0.01 to 0.15 PCM f/ml (0.02-0.42 SEM f/ml). The geometric mean concentrations were 0.07 PCM f/ml (0.20 SEM f/ml), which is considerably higher than the threshold limit value (TLV) proposed by American Conference of Governmental Industrial Hygienist (ACGIH), which is 0.1 f/ml. The analysis showed a presence in the bulk samples only chrysotile asbestos and an absence of the other type asbestos. Therefore, it might be expected that workers who worked in the demolition of old houses will suffer from negative effects of exposing to the asbestos fibers.

In plain English

This field report measured workers' airborne asbestos exposure during hand demolition of old houses in Tehran, Iran. The authors took 45 personal air samples at 13 houses built before 1975, on four sites, in 2010 and 2011. No water was sprayed during demolition. Fibers were counted by phase-contrast microscopy (PCM) and scanning electron microscopy (SEM). The overall geometric mean was 0.07 fibers per milliliter by PCM (range 0.01 to 0.15) and 0.20 by SEM. SEM counts were significantly higher than PCM counts. Levels were significantly higher at the west site than at the south and east sites. They were also higher during roof (ceiling) demolition (SEM geometric mean 0.25) than wall demolition (0.11). Bulk materials, including cement sheet, chimney pipes and thermal insulation, contained chrysotile asbestos. The authors stated that all workers were exposed above the 0.1 f/ml ACGIH limit. However, the article's own figures include values below that limit by both methods (as low as 0.01 by PCM and 0.02 by SEM), and the overall PCM geometric mean of 0.07 was also below it. The authors concluded that demolition should minimize asbestos exposure for workers, residents and the environment.

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: Field report: workplace exposure assessment using personal air sampling and bulk material analysis, with descriptive statistics
• Who was studied: Construction workers demolishing 13 houses at 4 sites (south, east, west and centre of Tehran, Iran) in 2010 and 2011. 45 personal air samples were taken. There were about 3 to 5 workers per demolition, with a mean age of 28 years and a mean employment period of 7 years.
• Exposure: Manual demolition, using hand and powered tools, of houses built before 1975 that were likely to contain asbestos cement sheet and pipe. No water was sprayed. Bulk materials contained chrysotile asbestos.
• Main results:
  • For all 45 personal samples, the geometric mean was 0.07 f/ml by PCM and 0.20 f/ml by SEM. Values ranged from 0.01 to 0.15 f/ml by PCM and from 0.02 to 0.42 f/ml by SEM.
  • The west region had the highest SEM geometric mean (0.31 f/ml) and the east the lowest (0.13 f/ml). The west was significantly higher than the south (p less than 0.001) and the east (p less than 0.01). The difference between the west and the centre was not significant (p=0.07).
  • Concentrations were significantly higher during roof (ceiling) demolition than during wall demolition (p less than 0.001). Roof demolition (29 samples) had an SEM geometric mean of 0.25 f/ml and a PCM geometric mean of 0.08 f/ml. Wall demolition (16 samples) had an SEM geometric mean of 0.11 f/ml and a PCM geometric mean of 0.03 f/ml.
  • SEM geometric means were higher than PCM geometric means (p less than 0.05).
  • Bulk materials (cement sheet, chimney pipes, fire proofing, thermal insulation) at all four sites contained chrysotile asbestos. Airborne fibers examined by SEM with chemical analysis were compatible with chrysotile.
  • The authors stated that all workers were exposed above the ACGIH limit of 0.1 f/ml, although the reported ranges include values below it by both PCM and SEM.
• The authors' conclusion: The authors concluded that demolition needs to be carried out in a way that minimizes asbestos exposure for workers, residents and the environment. They recommended improved work practices and limiting public access to demolition sites.
• Limitations the authors state:
  • The PCM counting method (NIOSH 7400) cannot tell asbestos fibers from non-asbestos fibers, and it cannot detect fibers thinner than 0.25 micrometers.
  • PCM counting, especially of chrysotile, may underestimate asbestos levels.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Thermal System Insulation (TSI), Scanning Electron Microscopy (SEM), Polarized Light Microscopy (PLM), Threshold Limit Value (TLV), Chrysotile.

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