Characterisation of palygorskite specimens from different geological locales for health hazard evaluation

Our plain-English summary of Characterisation of palygorskite specimens from different geological locales for health hazard evaluation, by R.P. Nolan, A.M. Langer, G.B. Herson (British Journal of Industrial Medicine, 1991).

The study

• Authors: R.P. Nolan, A.M. Langer, G.B. Herson
• Journal: British Journal of Industrial Medicine
• Published: 1991;48(7):463-75
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Palygorskite, a fibrous clay mineral, is being used as a substitute for asbestos in some applications. Nine specimens obtained from different geological locales were studied for mineral purity, elemental composition, fibre size distribution, and surface binding characteristics. The membranolytic activity of each was determined using a human erythrocyte model. The membranolytic behaviour and surface binding characteristics were compared with three chrysotile specimens employed as positive controls. The palygorskite specimens derived from the different geological locales display a range of physicochemical properties. This study shows the importance of selecting several mineral specimens for a health hazard evaluation. The current carcinogenic classification of the mineral may be limited due to the number of specimens used for that particular evaluation.

In plain English

This laboratory study examined palygorskite, a fibrous clay used as an asbestos substitute in some applications. It compared nine palygorskite specimens from different geological locales, including Brazil, Korea, Australia, Soviet Russia, Switzerland, California and Georgia, USA, with three chrysotile asbestos specimens. The authors measured mineral purity, chemistry and fibre size, and tested in a test tube how strongly each specimen damaged human red blood cells. No animals or people were studied. Every palygorskite specimen contained detectable quartz. The Korean specimen was inactive, while the California specimen needed only 51 (SD 10) micrograms per millilitre to break open half the cells. The chrysotile specimens averaged 60 (SD 21), comparable with the most active palygorskites. Of three polymers tested, only 2-PVPNO reduced palygorskite's effect; aluminium ions also inhibited 60% of lysis by the most active palygorskite. The size distributions of the respirable fractions of palygorskite and chrysotile were very similar. The authors concluded that a health hazard evaluation of the mineral cannot be based on a single source. They described the findings as strong indicators suggesting certain specimens will present a health hazard when inhaled.

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 (in vitro) characterisation study: x ray diffraction, light and electron microscopy, chemical analysis, fibre sizing, and a human red blood cell (erythrocyte) membrane-damage assay
• Who was studied: Nine palygorskite specimens from different geological locales: Brazil; Yalu River, Korea; Dartmoor, western Australia; Nizhi, Novgorod, Soviet Russia; Zermatt, Switzerland; Attapulgus, Georgia, USA; two industrial specimens (NIOSH A and B) from the Georgia-Florida deposit; and New Melone's Lake, Calaveras, California. These were compared with three chrysotile specimens: UICC Chrysotile A (Zimbabwe), Chrysotile B (Canada), and California chrysotile RG-144 from New Idria.
• Exposure: Palygorskite, a fibrous clay mineral used as an asbestos substitute, compared with chrysotile. Activity was measured as the HC50: the concentration of mineral needed to break open 50% of the red blood cells in a suspension.
• Main results:
  • All nine palygorskite specimens contained detectable quartz. Per table 1, the Brazil specimen contained 25 to 50% quartz and the Australia specimen about 50%.
  • Membrane-damaging activity of the palygorskite specimens ranged from inactive (Korean specimen) to highly active (California specimen, HC50 51 (SD 10) micrograms per millilitre).
  • Among the active palygorskite specimens, the least and most active differed by a factor of almost 15.
  • The three chrysotile specimens had an average HC50 of 60 (SD 21) micrograms per millilitre, comparable with the most active palygorskites.
  • Of three polymers tested (chondroitin sulphate, BSA, 2-PVPNO), only 2-PVPNO inhibited palygorskite's membrane-damaging activity over the concentration range studied.
  • Aluminium ions (Al3+) at less than 10 micrograms per millilitre inhibited 60% of the lysis caused by the most active palygorskite.
  • The size distributions of the respirable fractions of palygorskite and chrysotile were very similar; both consisted of short fibres.
  • The California palygorskite, with the largest percentage of long fibre, was the most membrane-damaging per unit mass. The authors considered the Korean specimen's inactivity most likely related to surface properties, not fibre size.
  • The two specimens with the highest quartz content, Brazil and Australia, were the least active of the membrane-damaging specimens.
  • No correlation appeared between elemental composition and either fibre size or membrane activity.
• The authors' conclusion: The authors concluded that the variation among specimens means a health hazard evaluation of palygorskite cannot be based on evidence from a single source. They suggested the IARC classification would be better served by noting a range of activities. They also wrote that fibre size distribution, surface properties and expected stability in the body are strong indicators suggesting certain specimens will present a health hazard when inhaled.
• Limitations the authors state:
  • The authors noted that two of the reference x ray diffraction patterns used for comparison may be confounded by the presence of quartz.

Topics

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

Medical terms in this study, explained in our Lexicon: Palygorskite (Attapulgite), Chrysotile, Carcinogenic.

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