Evaluation of the K2 asbestos screening test kit

Our plain-English summary of Evaluation of the K2 asbestos screening test kit, by W. Sahle (The Annals of Occupational Hygiene, 1987).

The study

• Author: W. Sahle
• Journal: The Annals of Occupational Hygiene
• Published: 1987;31(2):227-32
• Read it: PubMed · Publisher

In plain English

This laboratory study from Sweden's National Board of Occupational Safety and Health evaluated the K2 asbestos screening test kit. The kit, marketed as a field test, uses colour reactions to detect magnesium and iron, elements in asbestos minerals. It was tried on 30 building samples previously examined by optical microscopy and on 12 calibration preparations of titanium dioxide powder, alone or mixed with magnesium or iron oxides, amosite or chrysotile. With a white background the test detected about 0.08% by weight of magnesium or iron, but coloured samples made colour changes hard to read. The kit classified only three of the 30 field samples as asbestos-free, although 14 were known to be free of asbestos. A mainly wollastonite sample with no asbestos found still gave the red iron reaction after acid washing, contradicting the makers' claim. Whether calcium causes this colour was not investigated. The author noted the required acids and sodium hydroxide could be hazardous to transport. Testing was done in a laboratory, not the field. The author concluded the method's screening value was doubtful and its use outside a laboratory unacceptable.

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 evaluation of a commercial colorimetric asbestos screening test kit
• Who was studied: 30 field bulk samples selected from materials sent from public and industrial buildings to the Swedish National Board of Occupational Safety and Health for asbestos analysis, plus 12 calibration preparations, one of them pure titanium dioxide
• Exposure: Not a study of human exposure. Field samples contained, according to earlier optical microscopy, amosite, chrysotile, crocidolite, anthophyllite, tremolite, wollastonite, MMMF, or no asbestos. Calibration preparations were titanium dioxide (TiO2) with MgO, Fe2O3 (later replaced by magnetite), amosite or chrysotile, and also pure TiO2 powder.
• Main results:
  • The test classified only 3 of the 30 field samples as asbestos-free, whereas 14 of the samples were known to be free from asbestos.
  • In the calibration mixtures, the detection limit was about 0.08% by weight for both magnesium and iron, provided background colour did not interfere.
  • When naturally coloured samples were excluded, iron and/or magnesium was reliably detected in all field samples known by other methods to contain asbestos.
  • Original sample colour made results unreliable: the magnesium reaction for samples 6, 12, 24, 27 and 30, and the iron reaction for samples 7 and 16.
  • Sample 3 was mainly wollastonite, with no asbestos found by optical microscopy and X-ray diffraction. It still gave the red iron colour reaction after acid washing, which the author took as contradicting the claim that iron-containing non-asbestos material washes away. Whether calcium could also give the red colour was not investigated.
  • The required chemicals (sulphuric, phosphoric, hydrofluoric and acetic acid, and sodium hydroxide) may constitute an occupational hazard when transported.
• The authors' conclusion: The author concluded that the practical value of the method for asbestos screening is doubtful and that its use outside a laboratory is unacceptable.
• Limitations the authors state:
  • Although the method is promoted as a field technique, this evaluation, like earlier ones, was carried out in a laboratory setting.
  • The possibility that calcium forms a red complex with the iron reagent was not investigated.

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