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Asbestos Exposure during Routine Brake Lining Manufacture

Source: Industrial Health 2007, 45, 787-792

As awareness of the hazards of asbestos exposure became more common during the last few decades, many developed nations implemented statutory protocols strictly regulating the manner in which asbestos could be commercially used. Some of these nations even moved past regulation and enacted outright bans on the use of asbestos-family minerals. However, this pattern has not been duplicated among developing nations, where the use of asbestos has often continued unabated. Safety procedures that are necessary to protect the health of the work force have not been implemented in many of these nation’s factories and without active regulatory enforcement there is rarely any monitoring of air quality levels. The result is that workers continue to operate in unsafe environments where they are regularly exposed to extremely high levels of a known carcinogen, conclusively shown to cause all forms of mesothelioma, especially the two most common forms of the disease: pleural mesothelioma and peritoneal mesothelioma, as well as lung cancer and asbestosis.

In order to understand the exposure risks in these kinds of factories, Iranian researchers collected air samples from a brake lining manufacturing plant in Iran and compared their findings to the permissible exposure limit (PEL) regarding asbestos exposure developed and currently utilized by the Occupational Safety and Health Administration (OSHA).

Overview of the Study

The authors state that Iran has 26 brake lining manufacturing plans in current operation and the total workforce employed in those plants is approximately 3,000 people. They selected one of these plants to study overall air quality levels and to analyze the exposure risks of specific manufacturing processes. In selecting the lining manufacturing plant, the authors described some of the tasks performed, which included the grinding, beveling and drilling of materials, as well as a number of other procedures. Many of these tasks are dry processes, where the materials at hand release large amounts of dust into the air.

In measuring overall airborne dust samples, the authors found an average of particle concentration of 9.6 mg/m3, with the highest levels found in workers employed in the beveling process: 16.32 mg/m3. While the average figure is just below the threshold limit of 10 mg/m3 per day for total dust set by the American Conference of Governmental Industrial Hygienists, the bevellers, as well as those responsible for polish (11.40 mg/m3) and reassembly (11.54 mg/m3) found the particle density in their air exceeding ACGIH’s limits. OSHA’s threshold limit for this test is 15 mg/m3 , so the bevellers exceeded that limit as well.

To analyze the asbestos density in the plant’s breathable air, the authors used phase contrast optical microscopy (PCM), which is the standard technique for asbestos testing. The results returned showed an average fiber concentration of .78 f/cc, with the highest recorded level at 1.85 f/cc. With OSHA’s PEL (permissible exposure limit) for asbestos density set at only 0.1 fibers/cc, the average concentration level was 7.8 times greater than OSHA’s recommendation.

The authors completed their study in the summer, when ventilation was at its most effective, as the plant’s windows were all open because of the summer heat. The authors speculate that dust and asbestos levels during winter months would be much greater than the levels they measured because windows wouldn’t be open during winter, so ventilation would be less effective.


The results of the study clearly indicate asbestos and dust levels greater than OSHA recommendations. These levels also clearly indicate a heightened exposure risk for asbestos-related diseases, such as mesothelioma and lung cancer. In describing their paper as the first to look at asbestos levels in a brake lining manufacturing plant in Iran, the authors also see it as representative of asbestos levels found in plants in most developing countries. They strongly recommend improvements in ventilation and housekeeping to reduce contaminant levels.

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Nancy Meredith is a blog and web content writer with more than 20 years of professional experience in the Information Technology industry. She has been writing about Mesothelioma for 4 years. Follow Nancy on Google+

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