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Paul T.C. Harrison,¹ Leonard S. Levy,¹ Graham Patrick,² Geoffrey H. Pigott,³ and Lewis L. Smith^1,2,*

¹Medical Research Council Institute for Environment and Health, University of Leicester, Leicester, United Kingdom
²Medical Research Council Toxicology Unit, University of Leicester, Leicester, United Kingdom
³Alderley Edge, Cheshire, United Kingdom

Abstract

Although the use of amphibole asbestos (crocidolite and amosite) has been banned in most European countries because of its known effects on the lung and pleura, chrysotile asbestos remains in use in a number of widely used products, notably asbestos cement and friction linings in vehicle brakes and clutches. A ban on chrysotile throughout the European Union for these remaining applications is currently under consideration, but this requires confidence in the safety of substitute materials. The main substitutes for the residual uses of chrysotile are p-aramid, polyvinyl alcohol (PVA) , and cellulose fibers, and it is these materials that are evaluated here. Because it critically affects both exposure concentrations and deposition in the lung, diameter is a key determinant of the intrinsic hazard of a fiber ; the propensity of a material to release fibers into the air is also important. It is generally accepted that to be pathogenic to the lung or pleura, fibers must be long, thin, and durable ; fiber chemistry may also be significant. These basic principles are used in a pragmatic way to form a judgement on the relative safety of the substitute materials, taking into account what is known about their hazardous properties and also the potential for uncontrolled exposures during a lifetime of use (including disposal) . We conclude that chrysotile asbestos is intrinsically more hazardous than p-aramid, PVA, or cellulose fibers and that its continued use in asbestos-cement products and friction materials is not justifiable in the face of available technically adequate substitutes. Key words: aramid, asbestos, cancer, cellulose, chrysotile, fibrosis, hazards, PVA, substitute fibers. Environ Health Perspect 107:607-611 (1999) . [Online 24 June 1999]

http://ehpnet1.niehs.nih.gov/docs/1999/107p607-611harrison/ abstract.html

Address correspondence to G. Patrick, MRC Toxicology Unit, University of Leicester, Hodgkin Building, PO Box 138, Leicester LE1 9HN, United Kingdom. Telephone: 0044 116 252 5607. Fax: 0044 116 252 5616. E-mail gp15@le.ac.uk

*Current address: Central Toxicology Laboratory, Zeneca, Ltd., Macclesfield, Cheshire, United Kingdom.

The authors thank the UK Health and Safety Executive for sponsoring this study. The views expressed are, however, those of the authors themselves.

Received 11 December 1998 ; accepted 8 April 1999.