Asbestos Exposure And Control At Puget Sound Naval Shipyard

Our plain-English summary of Asbestos Exposure And Control At Puget Sound Naval Shipyard, by C.A. Mangold, R.R. Beckett, D.J. Bessmer (1970).

The study

• Authors: C.A. Mangold, R.R. Beckett, D.J. Bessmer
• Published: U.S. Navy, Puget Sound Naval Shipyard Industrial Hygiene Division, March (1970)
• Type of article: Government report
• Our copy: from Johns-Manville's own medical library, J-M no. 004268.

In plain English

This March 1970 report from the Industrial Hygiene Division at Puget Sound Naval Shipyard, Bremerton, Washington, compared chest X-ray records across trades, measured asbestos dust in insulators' breathing zones, and described dust controls. In a two and one-half year X-ray comparison begun in July 1965, about 21% of pipe coverers and insulators had positive X-ray findings. This compared with 3.5% of boilermakers, who had some asbestos and silica exposure, and about 1% or less of other occupations with no known asbestos exposure. Positive findings counted all reported abnormalities, and most were classified as pulmonary fibrosis. Among the 22 men with positive findings whose work histories were reviewed, one was the only diagnosed case of asbestosis. Allowing for time weighting and the asbestos content of materials, insulators' exposures were below the Threshold Limit Value of 5 million particles per cubic foot. Peaks during the work day often exceeded it up to ten times. The authors concluded the shipyard had a problem with asbestos and that the limits had perhaps been too high. They noted that smoking status was unknown and that the X-ray comparison did not consider specific diagnosis or degree of lung damage.

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: Shipyard industrial hygiene report: comparison of chest X-ray findings across occupational groups using shipyard medical records, plus breathing-zone air sampling with a midget impinger and a description of control methods
• Who was studied: Working population of Puget Sound Naval Shipyard, Bremerton, Washington, who received routine chest X-rays, compared by trade over two and one-half years starting July 1965. Pipe coverers and insulators were the main focus, and 22 of them had positive X-ray findings.
• Exposure: Asbestos insulation materials used by pipe coverers and insulators during ship overhaul, shop fabrication and new ship construction: amosite (95% long fiber asbestos), magnesia block (15% asbestos), asbestos cement, and asbestos cloth (80-95% chrysotile or amosite fibers with cotton). Dust was measured in million particles per cubic foot by midget impinger.
• Main results:
  • About 21% of pipe coverers and insulators had positive chest X-ray findings, compared with 3.5% of boilermakers and about 1% or less of other occupations with no known asbestos exposure.
  • Boilermakers were described as having some exposure to both asbestos and silica.
  • Positive X-ray findings included all reported abnormalities and did not mean diagnosed asbestosis. Most positive findings were classified by physicians as pulmonary fibrosis.
  • Among the 22 pipe coverers and insulators with positive findings, one man (case 7) was the only diagnosed case of asbestosis, confirmed by chest surgery.
  • A very high incidence of positive lung findings was seen in pipe coverers and insulators with over 20 years of exposure.
  • Allowing for time weighting and the asbestos content of materials, pipe coverers and insulators received exposures below the current and proposed Threshold Limit Values.
  • Peak exposures during the work day often exceeded Threshold Limit Values by up to ten times.
  • In a January 1968 survey, 76% of insulators did not use a respirator, and about 50% did not have one in their possession.
• The authors' conclusion: The authors concluded that, despite other possible contributing factors, their data showed the shipyard had a problem with asbestos. They also concluded that Threshold Limit Values had perhaps been too high and that intermittent peak exposures mattered more than formerly recognized.
• Limitations the authors state:
  • The smoking status of workers and confirmed diagnoses of the X-ray findings were not available.
  • Specific diagnosis and degree of lung damage were not considered in the X-ray comparison.
  • The impinger sampling method has recognized limitations, including low collection efficiency.
  • Methods of assessing exposure may not reflect the true airborne concentration of asbestos dust.
  • Very short intervals between first exposure and X-ray changes probably indicate causes other than occupational asbestos exposure.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Industrial Hygiene, Chest X-Ray, Insulator, Dust Control, Pulmonary Fibrosis, Threshold Limit Value (TLV), Million Particles per Cubic Foot (mppcf).

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