Evaluation of exposure to the airborne asbestos in an automobile brake and clutch manufacturing industry in Iran

Our plain-English summary of Evaluation of exposure to the airborne asbestos in an automobile brake and clutch manufacturing industry in Iran, by H. Kakooei, H. Marioryad (Regulatory Toxicology and Pharmacology, 2010).

The study

• Authors: H. Kakooei, H. Marioryad
• Journal: Regulatory Toxicology and Pharmacology
• Published: 2010;56(2):143-7
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

About 2000 tons of chrysotile is used annually to produce friction materials in Islamic Republic of Iran. Approximately, 3000 workers are exposed to the asbestos fibers in the different processes of brake and clutch manufacturing. In the current study, asbestos fiber concentrations during brake and clutch manufacture were measured. This study also evaluated the fiber size and morphology distribution according to the Asbestos International Association (AIA) for standardization analytical method for asbestos. The airborne asbestos fiber concentrations and its chemical composition of 92 personal samples were analyzed by phase contrast microscopy (PCM) and scanning electron microscope (SEM) equipped with an energy-dispersive X-ray analyzer (EDX). Personal monitoring of fiber levels demonstrated counts that ranged from 0.31 to 1.3 PCM f/ml (15.5-51.5 SEM f/ml). Geometric means of the asbestos concentrations were 1.3 PCM f/ml (51.5 SEM f/ml) and 0.86 PCM f/ml (42.1 SEM f/ml) according to the brake weighting and mixing and clutch mixing process, respectively. The geometrical mean concentrations were 0.63 PCM f/ml (31 SEM f/ml), which is considerably higher than threshold limit value (TLV) of the American Conference of Governmental Industrial Hygienists (ACGIH) which is 0.1f/ml. The SEM data demonstrate that the fibrous particles consisted, approximately, of chrysotile (50%), tremolite (30%), and actinolite (20%). Based on these findings, the 50% of airborne fibers inhaled by the workers were amphiboles asbestos with fibers equal and greater than 5 microm in length and 0.2 microm in diameter, and thus not included in the PCM-based fiber counts. Therefore, it might be expected that workers who worked in the brake and clutch manufacture will suffer from negative health effects of exposing to the amphibole asbestos fibers.

(c) 2009 Elsevier Inc. All rights reserved.

In plain English

This study measured airborne asbestos in a brake and clutch factory in Tehran, Iran, where 110 of 220 workers worked directly in brake and clutch production. The authors collected 92 personal air samples from workers' breathing zones in December 2008 and January 2009. They counted fibers by phase contrast microscopy (PCM) and scanning electron microscopy (SEM). Chrysotile was the main asbestos used; crocidolite and amosite were not used. The highest geometric mean was in weighting and mixing (1.3 PCM fibers per ml; 50.5 SEM fibers per ml), and the lowest was in drilling (0.31 PCM fibers per ml). The overall geometric mean, 0.63 PCM fibers per ml, was more than 6.1 times the ACGIH limit of 0.1 fibers per ml. SEM analysis indicated the airborne fibers were approximately 50% chrysotile, 30% tremolite and 20% actinolite. The authors linked this to amphibole contamination of the chrysotile, talc and vermiculite used. They concluded that exposures were higher than in countries banning asbestos and that workers might be expected to suffer health effects. Worker health itself was not examined. The authors noted that the factory was not randomly chosen and that the number of samples was small.

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 in one factory, using personal breathing-zone samples analysed by PCM (NIOSH method 7400) and SEM with energy-dispersive X-ray analysis (AIA method); no health outcomes were studied
• Who was studied: One friction materials (brake shoe and clutch facing) factory in an industrial area of Tehran, Iran, operating since about 1962. In 2008, 110 of its 220 workers were directly involved in production. The workers were male, with a mean age of 25 (range 19 to 50) years and mean employment of 13 (range 1 to 35) years. 92 personal samples were collected from December 2008 to January 2009.
• Exposure: Airborne asbestos during dry-process brake and clutch manufacture (weighting and mixing, loading, milling, pressing, baking, bevelling, drilling, cutting, grinding/finishing). Chrysotile was the main asbestos constituent; crocidolite and amosite were not used. Other raw materials included talc and vermiculite. Bulk analysis found a mean chrysotile content of about 60% in clutches and 40% in brakes.
• Main results:
  • The weighting and mixing process (17 samples) had the highest geometric mean: 1.3 PCM fibers per ml and 50.5 SEM fibers per ml
  • Drilling (13 samples) had the lowest geometric mean: 0.31 PCM fibers per ml and 15.5 SEM fibers per ml
  • Across all personal samples, the geometric mean was 0.63 PCM fibers per ml (given as 32 SEM fibers per ml in the text). The authors reported this as more than 6.1 times the ACGIH TLV-TWA of 0.1 PCM fibers per ml.
  • SEM with energy-dispersive spectrometry indicated the airborne fibrous particles were approximately 50% chrysotile, 30% tremolite and 20% actinolite
  • Bulk X-ray diffraction analysis found asbestos in all clutches and brakes, with a mean chrysotile content of about 60% (clutches) and 40% (brakes)
  • Chrysotile fibers were mostly thinner (0.2 to 0.5 micrometres in diameter) than the tremolite and actinolite fibers (0.7 to 1.0 micrometres)
• The authors' conclusion: The authors concluded that exposure in brake and clutch manufacture in Iran was generally higher than in similar operations in countries with asbestos bans. They attributed this partly to the lack of engineering controls such as local exhaust ventilation. They also held imported chrysotile, talc and vermiculite containing tremolite and actinolite responsible for the high airborne amphibole levels. They stated that workers might be expected to suffer negative health effects from the amphibole fibers, and they recommended banning asbestos use.
• Limitations the authors state:
  • The factory was not selected randomly, and the number of samples was small
  • The dust collector (bag house) may have been running during sampling, increasing air exchanges

Topics

The National Library of Medicine indexes this study under subjects our site covers: Auto mechanics and brake work.

Medical terms in this study, explained in our Lexicon: Chrysotile, Personal Breathing Zone Sample, phase contrast microscopy (PCM), Threshold Limit Value (TLV), Tremolite, Actinolite, Amphibole Group, Amphibole Asbestos.

Related studies

• Evaluation of exposure to the airborne asbestos in an asbestos cement sheet manufacturing industry in Iran — D. Panahi, H. Kakooei, et al. (2011)
• A study of airborne chrysotile concentrations associated with handling, unpacking, and repacking boxes of automobile clutch discs — G.C. Jiang, A.K. Madl, et al. (2008)
• Evaluation of asbestos exposure during brake repair and replacement — H. Kakooei, M. Hormozy, et al. (2011)
• Exposure to chrysotile asbestos associated with unpacking and repacking boxes of automobile brake pads and shoes — A.K. Madl, L.L. Scott, et al. (2008)
• Airborne asbestos concentration from brake changing does not exceed permissible exposure limit — C.L. Blake, D.R. Van Orden, et al. (2003)
• Evaluation of the size and type of free particulates collected from unused asbestos-containing brake components as related to potential for respirability — M.A. Atkinson, M. O'sullivan, et al. (2004)

Browse more research in Regulatory Toxicology and Pharmacology, or return to medical research.