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Refractory Ceramic Fibre



Towards the end of 1998 certain types of man-made mineral fibres (MMMFs) will be classified as carcinogens. This OC and ID give information and guidance on hazards and precautions in the use of refractory ceramic fibre, one widely used type of MMMF.

Legal changes

On 10 November 1997, a European Technical Progress Committee decided that the evidence was sufficient to warrant RCF being classified as a category 2 carcinogen (ie a substance to be regarded as if it were carcinogenic to humans) and the risk phase R49 ('may cause cancer by inhalation') will apply. The Directive approved by this committee (Directive 97/69/EC of 5 December 1997) and now ratified by the European Commission will be implemented in the UK by an amendment to the Chemicals (Hazard Information and Packaging for Supply) Regulations 1994 (CHIP Regulations) as amended, coming into force no later than 16 December 1998. Further information is contained in OM 1997/123.

It has also been agreed that risk phrase R38 ('irritating to the skin') will apply to RCFs.

 The classification as a category 2 carcinogen will apply to fibres of a certain size only (those less than 6mm length weighted geometric mean diameter). Most RCF products currently marketed in the UK will fall into this category. The main implication is that the Control of Substances Hazardous to Health Regulations 1994 (COSHH) Carcinogens ACOP (file 273) will apply to all work with RCF. Information notes explaining the position in more detail as far as the ceramics industry is concerned were produced by the Ceramics and Heavy Clay NIG and circulated widely in November/December 1997 (see SIM03/2003/52). The information they contain may also be relevant to other industries.

 An additional problem for users is that after being exposed to high temperatures (greater than 1000oC) for prolonged periods as can happen in kilns and furnaces, it is known that RCF at the surface of the lining devitrifies to crystalline phases including cristobalite, a form of crystalline silica which can cause silicosis. Exposure to simulated 'after-service' fibres did not produce significant excess tumours in animal studies.

 The new Directive also classifies certain types of mineral wool as category 3 carcinogens. Although mineral wools are used in the above industries they have much wider application, particularly for domestic loft insulation, and are therefore not covered in this OC.

Hazards from the use of Refractory Ceramic Fibre


   This document contains internal guidance which has been made available to the public on the potential risks associated with the use of refractory ceramic fibre (RCF) and the precautions recommended when working with this material. The guidance is considered good practice (rather than compulsory) but you may find it useful in deciding what you need to do to comply with the law. However, the guidance may not be directly applicable in all circumstances and any queries should be directed to the appropriate enforcing authority.

What is refractory ceramic fibre?

Refractory ceramic fibre (RCF) as used for insulation, particularly in kilns and furnaces, is a form of man-made vitreous (silicate) fibre (MMVF) and consists of alumino-silicate fibres which can cause irritation of the skin, eyes and upper respiratory tract, many being fine enough to be inhaled and deposited in the lungs.

The main concerns are in relation to potentially serious long-term health effects; experiments in animals have shown that RCFs can produce lung fibrosis, lung cancer, and also mesothelioma (a rare tumour of the lining of the chest cavity usually only associated with exposure to asbestos) following long-term inhalation.

 Following several years of discussions in expert working groups involving industry and trade union representatives, a European Directive has now been agreed which will result in RCFs with fibres less than 6mm length weighted geometric mean diameter being classified as category 2 carcinogens (substances to be regarded as if they are carcinogenic to humans) towards the end of 1998. Most RCF products currently marketed in the UK will fall into this category. (They will additionally be classified as 'irritating to the skin').

 This is not a ban on use, but it will mean that any work with RCF will be subject to more stringent control measures, under the Control of Substance Hazardous to Health Regulations 1994 (COSHH Regulations), Carcinogens Approved Code of Practice (COSHH Carcinogens ACOP)1.

 The COSHH Regulations require employers to assess risks from their use of hazardous substances and ensure that appropriate control measures are being taken. The COSHH Carcinogens ACOP specifies that the first choice with carcinogenic materials is to prevent exposure by avoiding their use or substitution by a less-hazardous alternative.

 If it is not reasonably practicable to do this, exposure should be controlled to the lowest level reasonably practicable. 

The current occupational exposure limit for all forms of man-made mineral fibres, including RCF, is expressed in 2 ways, 5mg/m3 (total inhalable dust) and 2 fibres/ml, both averaged over an 8-hour period (known as the 8-hour TWA). These are maximum exposure limits (MELs), ie exposure should always be reduced to the lowest level reasonably practicable and should not exceed the limit. These limits are subject to review following the new classification.

 Air sampling may need to be carried out to be able to predict possible exposure levels. Unless the likely amount of fibres in air during various operations is known, it will not be possible to decide what precautions are appropriate. The appendix to this document shows typical fibre levels during various activities but these are intended only to be indicative, not a substitute for measurement. There is an approved method for measuring man-made mineral fibres, which is detailed in HSE Guidance Note EH 40 Occupational exposure limits2. Further, the European Ceramic Fibres Industry Association (ECFIA)3 will, through its controlled and reduced exposure programme (CARE), offer assistance in this area.

 It should also be borne in mind that after firing for a prolonged period of time at high temperatures (greater than 1000OC), RCF at the surface of kiln/furnace linings will devitrify to crystalline phases including crystalline silica, which is also a hazardous material, with a MEL of 0.3mg/m3 (8-hour TWA). Therefore, during plant maintenance when the lining is disturbed, workers could be exposed to both RCF and crystalline silica.

 As with any other potentially hazardous material, information on product labels and safety data sheets provided by manufacturers and suppliers should always be consulted and followed. Additional information is available from HSE in GN EH 46 Man-made mineral fibres4 (due for revision) and the General and Carcinogens ACOPs1 also contain relevant information and guidance.

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