Evaluation of exposure to the airborne asbestos in an asbestos cement sheet manufacturing industry in Iran

Our plain-English summary of Evaluation of exposure to the airborne asbestos in an asbestos cement sheet manufacturing industry in Iran, by D. Panahi, H. Kakooei, H. Marioryad, et al (Environmental Monitoring and Assessment, 2011).

The study

• Authors: D. Panahi, H. Kakooei, H. Marioryad, R. Mehrdad, M. Golhosseini
• Journal: Environmental Monitoring and Assessment
• Published: 2011;178(1-4):449-54
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Iran imports nearly 55,000 tons of Chrysotile asbestos per year and asbestos cement (AC) plants contribute nearly 94% of the total national usage. In the present study, airborne asbestos concentrations during AC sheet manufacturing were measured. The fiber type and its chemical composition were also evaluated by scanning electron microscopy (SEM), with energy-dispersive X-ray analysis. Airborne total fiber concentrations of 45 personal samples were analyzed by phase contrast microscopy. The results have highlighted that 15.5% of samples exceed the threshold limit value (TLV) established the American Conference of Governmental Industrial Hygienists, which is 0.1 fiber per milliliter (f/ml). Personal monitoring of asbestos fiber levels indicated a ranged from 0.02 ± 0.01 to 0.16 ± 0.03 f/ml. The geometrical mean was 0.05 ± 1.36 f/ml, which is considerably lower than the TLV. SEM data demonstrate that the fibrous particles consisted, approximately, of Chrysotile (55.89%) and amphiboles (44.11%). We conclude that the industrial consumption of imported Chrysotile asbestos is responsible for the high airborne amphibole asbestos levels in the AC sheet industry. More research is needed to improve characterization of occupational exposures by fiber size and concentration in a variety of industries.

In plain English

This study measured airborne fibers at one asbestos cement sheet factory in Kerman, Iran, from June 2009 to April 2010. The factory, with 120 workers, used a wet process with chrysotile asbestos (20%) and cement (80%). The authors took 45 one-hour personal air samples across six work areas, counted fibers by phase contrast microscopy, and identified fiber types by scanning electron microscopy with X-ray analysis. The geometric mean of all samples was 0.05 fibers per milliliter (f/ml). That is below the 0.1 f/ml limit of the American Conference of Governmental Industrial Hygienists, but 7 of 45 samples (15.5%) exceeded it. Feeding of raw materials had the highest geometric mean, 0.16 f/ml, significantly higher than other processes, with 4 of 7 samples above the limit. Three of 9 cutting and drilling samples also exceeded it. Fibers examined were chrysotile (55.89%) and amphibole (44.11%), including tremolite. The authors concluded that imported chrysotile containing tremolite and actinolite was responsible for the high airborne amphibole levels, and they recommended banning asbestos. They noted that the fiber-counting method cannot tell asbestos from other 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: Workplace air-sampling (exposure measurement) study at a single factory, using personal air samples counted by phase contrast microscopy and fiber identification by scanning electron microscopy with energy-dispersive X-ray analysis
• Who was studied: One asbestos cement (AC) sheet plant in Kerman, Iran, studied June 2009 to April 2010. It employed 120 male workers with a mean age of 41 (range 29 to 56) and mean employment of 15 (range 7 to 17) years. 45 personal air samples were taken across six processes.
• Exposure: Airborne fibers during wet-process asbestos cement sheet manufacture from imported chrysotile asbestos (20%) and cement (80%). Processes were feeding of raw materials, mixing, molding of sheets, unloading cars, cutting and drilling, and sheet storage.
• Main results:
  • Across all 45 personal samples, the geometric mean was 0.05 f/ml (table: 0.0522, geometric standard deviation 1.36). This is below the ACGIH limit of 0.1 f/ml.
  • 7 of the 45 samples (15.5%) were above the 0.1 f/ml threshold limit value. Individual sample results ranged from 0.012 to 0.243 f/ml.
  • Feeding of raw materials had the highest geometric mean concentration, 0.16 f/ml (table: 0.1645). This was significantly higher than the other processes (p less than 0.05), and 4 of 7 feeding samples (57.1%) exceeded the limit.
  • In cutting and drilling, 3 of 9 samples (33.3%) exceeded the limit. The geometric mean was 0.0776 f/ml and the range 0.035 to 0.243 f/ml.
  • Mixing had the lowest geometric mean, 0.02 f/ml (table: 0.0208).
  • By electron microscopy and X-ray analysis, fibrous particles in the airborne dust were 55.89% chrysotile and 44.11% amphibole. Tremolite fibers were identified.
• The authors' conclusion: The authors concluded that imported chrysotile asbestos ore containing tremolite and actinolite was responsible for the high airborne amphibole asbestos levels in the plant. They called for more research on exposures by fiber size and concentration, and strongly recommended banning asbestos and producing non-asbestos products.
• Limitations the authors state:
  • The phase contrast microscopy counting method does not distinguish asbestos from non-asbestos fibers and cannot detect fibers thinner than 0.25 micrometers. For this reason the authors added electron microscopy.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Chrysotile, Scanning Electron Microscopy (SEM), Personal Breathing Zone Sample, phase contrast microscopy (PCM), Threshold Limit Value (TLV), Amphibole Group, Amphibole Asbestos.

Related studies

• Assessment of airborne asbestos exposure at an asbestos cement sheet and pipe factory in Iran — H. Marioryad, H. Kakooei, et al. (2011)
• Evaluation of exposure to the airborne asbestos in an automobile brake and clutch manufacturing industry in Iran — H. Kakooei, H. Marioryad (2010)
• Spatio-seasonal variation of airborne asbestos concentration in urban areas of Shiraz, Iran — M.K. Fathi Fathabadi, A. Abdolahnejad, et al. (2017)
• Evaluating the airborne asbestos dispersion in enclosed parking lots in Iran — N. Nasirzadeh, Y. Rasoulzadeh, et al. (2022)
• Emission of airborne fibers from mechanically impacted asbestos-cement sheets and concentration of fibrous aerosol in the home environment in Upper Silesia, Poland — J.S. Pastuszka (2009)
• Spatio-seasonal variation, distribution, levels, and risk assessment of airborne asbestos concentration in the most industrial city of Iran: effect of meteorological factors — M. Kermani, A. Jonidi Jafari, et al. (2021)

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