The Industrial Environment And Its Control

Our plain-English summary of The Industrial Environment And Its Control, by J.M. Dallavalle (1965).

The study

• Author: J.M. Dallavalle
• Published: New York: Pitman Publishing Corporation (1965)
• Type of article: Government report
• Our copy: from Johns-Manville's own medical library, J-M no. 005288.

In plain English

The supplied text is not the cited DallaValle book. It is section B-6, "Dust Counting Techniques", by Robert L. Harris, Jr., from a U.S. Public Health Service syllabus revised in 1965. It is a methods chapter, not a health study, and does not mention asbestos. It explains how to count mineral dust particles collected in impinger samplers, including the 1942 standard method, settling times and counting statistics. In one project, some 100 samples were counted in the field within 24 hours and again about 1 to 2 weeks later. Only 25% of pairs fell within the 50% limits and 55% within the 90% limits; 65% gave lower laboratory counts. At 90F and 85 percent relative humidity, a sampling liquid that began as commercial 95.5 percent ethyl alcohol fell to about 60 percent alcohol after 20 minutes of sampling. The author suggested settling times giving counts matching quartz settling in water for 30 minutes. Noting that observers differ in seeing small particles, the author wrote that it appears differences between counters cannot be eliminated except by selecting counting personnel.

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: Instructional methods chapter from a training syllabus on impinger dust sampling and light-field particle counting. It is not an epidemiological or clinical study.
• Who was studied: No human population was studied. The only data set described is some 100 dust samples from one project, each counted twice.
• Exposure: Airborne insoluble inorganic (mineral) dust of the kind linked to lung fibrosis, with quartz used as the reference dust. No asbestos or specific fiber type is named.
• Main results:
  • Some 100 samples were counted in the field within 24 hours and recounted in the laboratory about 1 to 2 weeks later. Only 25% of the count pairs fell within the 50% limits, and only 55% fell within the 90% limits.
  • In the same recount project, 65% of the aged samples gave lower counts in the laboratory than in the field.
  • In a warm, humid environment (90F, 85 percent relative humidity), a sampling liquid that started as commercial 95.5 percent ethyl alcohol changed to about 60 percent alcohol after 20 minutes of sampling.
  • The calculated settling time for a 1 micron quartz particle in water at 25 degrees C was about 25 minutes per millimeter of cell depth.
  • By calculation, only about one-tenth of 1 micron particles with a density of 1.4 g/cc (such as coal) would settle to the floor of a 1 mm counting cell in 25 minutes in a 50 percent ethyl alcohol-water mixture.
  • Actual counting cell depths may vary by up to 20 percent from the nominal depth.
• The authors' conclusion: The author suggested that, absent other standard procedures, settling times be chosen so that counts match those that would be obtained for quartz settling in water for 30 minutes. Because observers differ in how small a particle they can detect, the author wrote that it appears inter-observer variance cannot be eliminated except by selecting counting personnel.
• Limitations the authors state:
  • Changes in the composition of alcohol-water mixtures other than ethyl alcohol-water during sampling had not been studied.

Topics

Medical terms in this study, explained in our Lexicon: Midget Impinger.

Browse return to medical research.