Question 1
Is there evidence for a difference in biological potency between chrysotile asbestos and the amphibole fibres types?
Answer:
Yes, there is an overwhelming body of evidence, based on epidemiological studies on clinical findings, and on lung tissue mineral analysis in humans showing a definite difference in potency between chrysotile and the amphiboles.
Recently published data show that:
- The morbidity and mortality experience of workers handling chrysotile only is much less severe than that of workers exposed to amphiboles (or to mixtures containing them).
- The results of mineral contents of lung tissue by fibre type show that large amounts (100-fold) of amphiboles are found in the lungs of cases compared to controls. This is not so for chrysotile.
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Question 2 >>
References for Question 1:
Wagner JC, Moncrieff CF, Coles R, Griffiths DM and Munday, DE (1986). British Journal of Industrial Medicine 43:391-395
A study among naval dockyard workers showing increasing amounts of amphiboles in lung tissue and increasing severity of asbestosis, but no increase of chrysotile.
Wagner JC, Newhouse ML, Corrin B, Rossiter CER and Griffiths DM (1988). British Journal of Industrial Medicine 45(5):301-308
The lungs from 36 past workers of an asbestos factory using chrysotile, crocidolite and amosite were examined. Crocidolite and amosite lung contents were strongly associated with asbestosis and with mesothelioma, whereas no such correlation was evident with chrysotile and mullite.
Albin A, Pooley FD, Stromberg U, Attewell R, Mitha R and Welinder H (1994). Occup. Environ. Med. 51: 205-211
Retention patterns of asbestos fibres in lung tissue among asbestos cement workers. A study showing different kinetics for amphibole and chrysotile fibres in human lung tissue. Amphibole fibre concentrations increase with duration of exposure, whereas chrysotile concentrations do not. The authors indicate that their study supports a former finding of a possible adaptive clearance of chrysotile and conclude that their findings ìsupport the hypothesis that adverse effects are associated rather with the fibres that are retained (amphiboles), than with the ones being cleared (largely chrysotile).
McConnell EE, Chevalier HJ, Hesterberg TW, Hadley JG, Mast RW (1994). ILSI Monograph - Toxic and Carcinogenic Effects of Solid Particles in the Respiratory Tract. Eds. DL Dungworth, JL Mauderly and G. Oberdorster. ILSI Press, Washington, DC (pp. 461-467)
Following an inhalation study where the effects of crocidolite and chrysotile were compared, the authors conclude: crocidolite causes more inflammatory disease and at an earlier time than chrysotile asbestos.
