Asbestos Exposure among Mitering Workers

Our plain-English summary of Asbestos Exposure among Mitering Workers, by W. Phanprasit, D. Sujirarat, P. Musigapong, et al (Safety and Health at Work, 2012).

The study

• Authors: W. Phanprasit, D. Sujirarat, P. Musigapong, P. Sripaiboonkij, C. Chaikittiporn
• Journal: Safety and Health at Work
• Published: 2012;3(3):235-40
• Type of article: Case report
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The objectives are to compare the airborne asbestos concentrations resulted from mitering of abestos cement roof sheets by a high-speed motor and a hand saw, and to monitor whether other workers near the test sites are vulnerable to the fibers exceeding the occupational exposure limit. Four test cases were carried out and altogether 7 personal and 4 area air samples were collected. The NIOSH method 7400 was employed for the air samplings and analysis. Using the phase contrast microscopy, fiber counting was conducted under Rule A. The study showed that the fiber concentration medians for personal air samples gathered from the two tools were 4.11 fibers/cc (ranged: 1.33-12.41 fibers/cc) and 0.13 fibers/cc (ranged: 0.01-5.00 fibers/cc) respectively. The median for the area samples was 0.59 fibers/cc (ranged: 0.14-3.32 fibers/cc). Comparing each study case, the concentration level caused by the high-speed motor saw was more than twice that of the hand saw. According to the area samples, the workers nearby the test site are at risk from high exposure to asbestos.

In plain English

This article, labelled a case report, measured airborne asbestos fibers while workers mitered (cut) asbestos cement roof sheets. The authors state that such sheets contain approximately 10% to 15% asbestos by weight. In four tests, on different days at ventilated open-air sites, workers cut sheets for 15 minutes with a high-speed motor saw. In three tests they also used a hand saw. Air was sampled on each worker and 2 to 3 meters away. All four motor-saw personal samples exceeded the US OSHA 30-minute excursion limit of 1 fibers/cc (median 4.11 fibers/cc, range 1.33 to 12.41). The three hand-saw personal samples had a median of 0.13 fibers/cc (range 0.01, a value below the limit of detection, to 5.00); only the Case 2 sample exceeded the limit. The four area samples had a median of 0.59 fibers/cc (range 0.14 to 3.32). The authors reported that cutting more sheets at once produced higher concentrations. They concluded that the sheets release asbestos at concentrations harmful to workers and the public. Because the tests were brief, they compared results with a short-term limit.

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: Case report (as labelled by the journal) of four field air-sampling tests during roof-sheet mitering, using personal and area samples analysed by NIOSH method 7400 with phase contrast microscopy and counting Rule A
• Who was studied: Four workers, one per test case, each tested on a different day at different ventilated, open-air sites. Workers in Cases 1 to 3 used both a hand saw and a high-speed motor saw. The worker in Case 4 used only the motor saw. The article does not state the dates or exact locations. The authors are at Thai universities and frame the study around Thailand.
• Exposure: Mitering of asbestos cement corrugated roof sheets, stated to contain approximately 10% to 15% asbestos by weight; the fiber type in the sheets is not specified. The tools were a high-speed motor saw (800 rpm in Case 1, 1,200 rpm in Cases 2 to 4) and a wood-cutting or metal-cutting hand saw, each used for 15 minutes. Personal samples lasted about 30 minutes per saw. Area samples were taken 2 to 3 meters from the cutting point for 60 minutes.
• Main results:
  • High-speed motor saw, personal samples (4 workers): all exceeded the OSHA 30-minute excursion standard of 1 fibers/cc. The median was 4.11 fibers/cc and the range 1.33 to 12.41 fibers/cc (Case 1: 1.70; Case 2: 12.41; Case 3: 6.52; Case 4: 1.33).
  • Hand saw, personal samples (3 workers): the median was 0.13 fibers/cc and the range 0.01 to 5.00 fibers/cc. Only the Case 2 sample (5.00 fibers/cc) was over the excursion standard. Table 1 marks the Case 1 value (0.01) as lower than the limit of detection.
  • Area samples (4 samples, taken 2 to 3 meters from the cutting point and covering both tools): the median was 0.59 fibers/cc and the range 0.14 to 3.32 fibers/cc.
  • The authors reported that the number of sheets cut at once had a greater influence than saw speed. In Case 1, the 800 rpm motor saw cutting 2 sheets produced 1.70 fibers/cc. In Case 4, the 1,200 rpm saw cutting one sheet produced 1.33 fibers/cc.
  • Case 2 had the highest concentrations. The authors noted that the air there was stagnant and that the worker worked quickly and close to the task.
• The authors' conclusion: The authors concluded that asbestos cement sheets release asbestos dust at concentrations harmful to workers and to the general public. They rejected the argument that such non-friable sheets are safe for workers and for people living nearby.
• Limitations the authors state:
  • The data came from a brief, time-limited exercise, so the results were compared with the OSHA short-term (excursion) limit rather than an 8-hour standard.
  • The authors note that mitering at real construction sites usually lasts much longer than the tests did.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Occupational Exposure, NIOSH Method 7400, Air Sampling, phase contrast microscopy (PCM), Fiber Counting.

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