Real-time measurement of fibers using an HY-differential mobility analyzer with an optical particle counter (KOFAM)

Our plain-English summary of Real-time measurement of fibers using an HY-differential mobility analyzer with an optical particle counter (KOFAM), by S. Choi, K. Jang, K. Park, et al (PloS One, 2017).

The study

• Authors: S. Choi, K. Jang, K. Park, H. Kim
• Journal: PloS One
• Published: 2017;12(8):e0182119
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

This study investigated the applicability of an HY-differential mobility analyzer with an optical particle counter (HY-DMA/OPC), named as KOFAM, for counting fibrous matters in real time. Fibers separated from particles by the HY-DMA were counted with an OPC. To assess the KOFAM performance, the proposed method and the conventional gold standard phase contrast microscopy (PCM) method were compared in terms of variables such as recovery, relative difference, coefficient of determination, and conformity. The optimal sheath-to-aerosol (outlet) flow ratio of the internal flow in the HY-DMA was determined to be 1.6:1. In terms of recovery of the HY-DMA, the highest recovery was obtained at a voltage of 500 V regardless of which type of asbestos was tested. The recovery rate for serpentine was 45.5% and that for amphibole was 34.9%. The coefficients of determination of serpentine (R2 = 0.89) and amphibole (R2 = 0.87) were highly correlated. With respect to the coefficient of variation (CV), the KOFAM demonstrated superior performance over the M7400AD and F-1 methods and showed almost no difference from the PCM method (KOFAM: 22.5%, M7400AD: 32.4%, F-1: 88.8%, and PCM: 21.9%). There was no statistically significant difference between concentration measurements of the KOFAM and PCM analyses. Accordingly, it was concluded that the KOFAM can be used as a superior alternative to conventional fiber measurement methods. The preliminary results support the use of the KOFAM for constant measurement of airborne asbestos concentrations in real time.

In plain English

This was a laboratory study, done in Korea, testing a new instrument the authors developed, called KOFAM, meant to count airborne asbestos fibers in real time. It combines a device that separates fibers from other particles (an HY-DMA) with an optical particle counter. Serpentine asbestos (chrysotile) and amphibole asbestos (amosite, tremolite and actinolite), mixed with sand, were blown into a test chamber. KOFAM was compared with the standard microscope method (phase contrast microscopy, PCM) and with two commercial monitors, the M7400AD and the F-1. The device separated fibers best at a flow ratio of 1.6:1 and recovered the most fibers at 500 V. Because it recovered less than half of the fibers, the authors applied a correction factor. In linear regression against PCM, KOFAM had R2 values of 0.89 for serpentine and 0.87 for amphibole. Average coefficients of variation were 22.5% for KOFAM, 21.9% for PCM, 32.4% for the M7400AD and 88.8% for the F-1. The authors concluded that KOFAM could substitute for PCM. They noted that the study was done only in a laboratory and that field testing is needed.

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: Laboratory instrument-development and method-comparison study (chamber experiments comparing a new real-time fiber monitor with phase contrast microscopy and two commercial monitors)
• Who was studied: No human subjects. Asbestos samples were generated in a laboratory test chamber in Korea. Accuracy was tested 146 times for each asbestos type, 292 tests in total. Repeatability used samples at six concentrations, each repeated four times.
• Exposure: Serpentine (chrysotile) and amphibole (amosite, tremolite, actinolite) asbestos reference samples from RTI International, pulverized and mixed with sand at asbestos contents of 1 × 10^-5 to 0.1% (w/w), then dispersed as airborne fibers in a chamber
• Main results:
  • The HY-DMA separated fibers from particles most efficiently at a sheath-to-aerosol flow ratio of 1.6:1. After passing through it, only fibrous matter was seen on the filters.
  • Fiber recovery through the HY-DMA was highest at 500 V for all asbestos samples tested, and began to decrease at 600 V or more.
  • Recovery was below 50% because of particle losses inside the device, so a correction factor was applied to KOFAM counts. The article prints this factor as 2.98 in the Results and as 2.89 in the Discussion.
  • In linear regression against PCM, KOFAM gave R2 of 0.89 for serpentine and 0.87 for amphibole. The reported R2 values were 0.41 and 0.84 for the M7400AD, and 0.30 and 0.70 for the F-1.
  • Median relative difference from PCM for KOFAM was 31.2 for serpentine and 21.8 for amphibole. Overall accuracy for KOFAM was 72.9%, the highest of the methods compared.
  • Average coefficient of variation (precision) was 21.9 for PCM, 22.5 for KOFAM, 32.4 for the M7400AD and 88.8 for the F-1.
  • In Bland and Altman analysis, the average difference between KOFAM and PCM was 0.006 (95% CI -0.038 to 0.045) for serpentine and 0.009 (95% CI -0.030 to 0.047) for amphibole. Most values fell within plus or minus 2 SD, and KOFAM concentrations were lower than PCM concentrations.
• The authors' conclusion: The authors concluded that KOFAM and PCM concentrations did not differ significantly, that KOFAM can substitute for PCM and detect fibers in real time, and that it may be used to monitor asbestos release from abatement sites and ambient air.
• Limitations the authors state:
  • The study was conducted only in a laboratory. Field conditions such as temperature, humidity, non-uniform particulate matter and wind may interfere, and field assessments are needed.
  • Maximum recovery of KOFAM was less than 50% compared with PCM, requiring a correction constant to address underestimation.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: phase contrast microscopy (PCM), Serpentine Group, Amphibole Group.

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