The COC has been asked by HSE to provide advice on the relative carcinogenic risks of three chrysotile-substitutes namely, polyvinyl alcohol (PVA) fibres, p-aramid fibres, and cellulose fibres. The specific question referred by HSE asks whether these three materials pose less of a carcinogenic risk than chrysotile with respect to occupational and consumer health. In view of the urgency of providing DETR Ministers with advice on this issue of chrysotile-substitutes a subgroup of the COC gave initial consideration to the question posed by HSE at a meeting on the 22 May 1998.

Assumptions and conclusion

The key assumptions in our deliberation are that:

1. carcinogenicity associated with exposure to chrysotile has been clearly demonstrated,
2. the physical properties (ie dimensions and potential for fragmentation) of chrysotile substitutes can be used to indicate potential hazard,
3. adequate epidemiological data are unlikely to become available,
4. occupational exposures to respirable PVA, p-aramid and cellulose fibres will be below the control limit for chrysotile of 0.5 f/ml (4h Time Weighted Average).

We therefore conclude: "The evidence presented to the Committee on fibre dimensions, studies in animals including that of biopersistence in the lung, indicate that the carcinogenic risk posed by PVA fibres, p-aramid fibres or cellulose fibres is likely to be less than that posed by chrysotile. Additional reassurance can be gleaned by noting that these materials are unlikely to form significant amounts of respirable fibres under normal working conditions and that occupational exposures to these materials will be below the control limit for chrysotile."

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