Asbestos Exposures During The Cutting and Matching of Asbestos Cement Pipe

Our plain-English summary of Asbestos Exposures During The Cutting and Matching of Asbestos Cement Pipe, by W.M. Noble, B.L. Kawahara, W.C. Cooper (1977).

The study

• Authors: W.M. Noble, B.L. Kawahara, W.C. Cooper
• Published: Equitable Environmental Health, INC. Berkley, CA. May 16, 1977. Prepared for the A/C Piper Association.
• Type of article: Report
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This 1977 report, prepared under contract for the A/C Pipe Producers Association, measured airborne asbestos and total dust as an experienced workman and a helper cut and machined 8-inch asbestos cement sewer and pressure pipe. The authors simulated field conditions at a pipe-cutting equipment manufacturer's premises, without ventilation or engineering controls. Fibers longer than 5 micrometers were counted; the pipe material contained chrysotile and crocidolite. With the abrasive disc saw, average short-term concentrations were 20.3 and 35.5 fibers/cc for the operator and 59.7 and 64.0 fibers/cc for the helper, above the then-current OSHA ceiling of 10 fibers/cc. No other tool exceeded 5 fibers/cc in short-term samples. Over about two hours that included disc cutting, integrated exposures were 3.94 fibers/cc for the operator and 7.07 fibers/cc for the helper. Without the disc, three-hour integrated personal exposures ranged from 0.09 to 0.75 fibers/cc. The authors concluded that current and proposed standards could be met with available equipment if the abrasive disc saw were eliminated or modified. They noted that counts below 0.5 fibers/cc had a fairly wide margin of error.

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: Industrial hygiene air-sampling study of simulated field cutting and machining of asbestos cement pipe, with short-term ("peak"), integrated personal, area, total dust and background samples
• Who was studied: One experienced workman (operator) and one helper performing the operations. A preliminary survey took place on 31 January 1977 and the main survey on February 8 and 9, 1977.
• Exposure: Asbestos cement pipe (8-inch sewer pipe, Class 2400, and 8-inch pressure pipe, Class 150) containing chrysotile and crocidolite. The pipe was cut or machined with a manual field lathe, a power-driven field lathe, an abrasive disc saw, a power hole cutter, and hammer, chisel and rasp, plus limited tests of a Wheeler chain cutter and a Pilot pipe cutter.
• Main results:
  • Abrasive disc cutting, operator: the average short-term ("peak") concentrations, from three samples on each pipe type, were 20.3 and 35.5 fibers/cc. The pipe type for each average cannot be reliably assigned from the scrambled tables.
  • Abrasive disc cutting, helper: the average short-term concentrations, from three samples on each pipe type, were 59.7 and 64.0 fibers/cc. The helper's exposure was higher than the operator's; the authors attributed this to the saw blade propelling dust toward the helper.
  • The authors stated that the helper's exposure during abrasive disc cutting was higher than the operator's.
  • No other cutting or machining operation produced peak concentrations above 5 fibers/cc.
  • The Wheeler cutter, used once on sewer pipe and once on pressure pipe, gave peak concentrations well below ceiling levels for both the operator and the helper.
  • Sewer pipe, all tools except the abrasive disc, about three hours: integrated exposure was 0.09 fibers/cc for the operator and 0.10 fibers/cc for the helper.
  • Pressure pipe, similar operations, three hours: integrated exposure was 0.75 fibers/cc for the operator and 0.17 fibers/cc for the helper. The area sample was 0.44 fibers/cc.
  • Two-hour period that included abrasive disc cutting on both pipe types: integrated exposure was 3.94 fibers/cc for the operator and 7.07 fibers/cc for the helper.
  • The area integrated sample, about 15 feet away, during abrasive disc operation was 4.90 fibers/cc.
  • Background fiber concentrations measured before and after each day's work were 0.01 to 0.02 fibers/cc.
  • Preliminary survey: the operator's integrated exposure during an hour of four representative procedures was 4.3 fibers/cc.
• The authors' conclusion: The authors concluded that the abrasive disc saw produced high airborne asbestos concentrations that greatly exceeded the OSHA peak standard. They concluded that the other tools gave peak exposures substantially below current and proposed ceilings. They believed that current and proposed standards could be met with available equipment if the abrasive disc saw were eliminated or modified, and that until then saw operators and helpers should be required to wear NIOSH-approved respirators.
• Limitations the authors state:
  • Fiber counts below 5 fibers/cc become less precise, and counts below 0.5 fibers/cc have a fairly wide margin of error.
  • Fibers shorter than 5 micrometers and fibers visible only by electron microscope were not counted, and fibers were not identified mineralogically.
  • Operations were simulated rather than studied at actual pipe installation sites.
  • The silica content of the total dust was not determined, so its hazard could not be evaluated.
  • The calculated daily exposure limits for abrasive disc work assume zero exposure for the rest of the work day.
  • One unusually high total dust value, for the hand lathe on sewer pipe, could not be explained.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Asbestos-Cement, Asbestos-Cement Pipe, Engineering Controls, Chrysotile, Crocidolite, OSHA.

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