According to the latest estimates around 25,000 employees in the EU are potentially exposed to refractory ceramic fibres (RCFs). The main work-related exposure route is inhalation of airborne fibres. RCFs are classified as category 1B carcinogens under the European CLP Regulation (EC 1272/2008), meaning that these substances are presumed to have a carcinogenic potential for humans based on animal evidence. Repeated or prolonged inhalation exposure to RCFs may increase the risk of lung cancer and other chronic lung diseases.

Where risks occur

RCFs are industrial products, used as insulation materials in high temperature applications in several industrial sectors. Their main application is as lining materials for kilns and furnaces. Major RCF consuming industries include chemical, fertilizer, petrochemical, steel, glass, ceramic, cement, foundry, and forging industries. Inhalation is the most important route of exposure to RCFs during manufacture and end-user processes. In RCF manufacturing industry, exposure to RCF may occur during mixing and forming processes, cutting or machining the material, and during processes where RCFs are combined or assembled with other materials.

At end-user locations, exposure to RCFs may occur in installing of high-temperature insulation materials, operating the machines and furnaces, furnace inspection and maintenance, and removal of RCF containing materials. Removing RCF insulating material from industrial furnaces and walls has resulted in some of the highest airborne concentrations measured in occupational settings.

More about the substance

RCFs are typically white or grey fibrous materials that are supplied in bulk fibre, blanket form, or contained in a solid product. Individual RCF fibres are not visible with the naked eye as their average diameters are in the low micrometre range. RCFs belong to a class of materials called synthetic vitreous fibres (SVFs). Chemically, SVFs consist mainly of silicate minerals. The SVFs differ from natural mineral fibres such as asbestos in that they have an amorphous (non-crystalline) structure, and they tend to be less durable.

Depending on the raw material and intended use, SVFs contain varying amounts of metal oxides. RCFs have a high alumina content, which allows them to withstand extremely high temperatures. RCFs are generally more persistent than other SVFs in biological environments such as the lung. The structure of RCFs can partially change from amorphous to crystalline form after being exposed to high temperatures (greater than 1000°C) for prolonged periods. Therefore, during maintenance and demolition work, when the RCF lining is disturbed, workers could be exposed both to RCF and crystalline silica.

Hazards that may occur

According to the European CLP regulation, RCFs are classified as category 1B carcinogens. This is based on evidence gained in animal experiments which suggest that repeated or prolonged inhalation exposure to RCFs may cause increased risk of lung cancer, pleural mesothelioma and other chronic lung diseases.

Short-term effects from inhaling RCFs may include respiratory irritation, such as sore throat, nasal congestion and cough. Dermal exposure to RCFs may result in contact dermatitis and itching. Fibres can also be transferred to the eyes for example via hands, causing irritation.

The potential of RCFs to cause lung effects is influenced by their physical and chemical properties, the most important being fibre diameter, length, and solubility in biological fluids. These are the key features that determine the transport to and the persistence (retention time) of the fibres in the lungs, and therefore, their toxicity. The latency period between exposure to RCF and related cancers is expected to be long, up to 20-30 years.

What you can do

The primary consideration must be whether substitution of RCF in products is technically possible. Examples for substitutes are alkaline earth silicate (AES) wools with lower bio-persistence, or light non-fibrous refractory products. The technical suitability of substitutes is highly dependent on the required thermal and mechanical properties or chemical and mechanical resistance. If substitution is not possible, it is advised to use suitable forms of products, such as pre-assembled products, laminated products, shaped parts, or working procedures which help minimising dust formation.

Spreading of RCF fibres can be minimised by enclosing dusty processes and by using effective exhaust ventilation. Fibre materials should be kept wrapped when not in use and handled as little as possible. Thoroughly wetting of the materials before removal is recommended to reduce the amount of airborne fibres. Areas where exposure may occur should be designated and kept separate from other working areas.

Employers should implement regular exposure assessments by personal sampling and/or stationary measurements to check if the protective measures are effective or whether further actions need to be taken. Workers should be trained regularly on the control measures necessary for working safely with RCFs to prevent exposure.

Eating, smoking and drinking in areas where there is a risk of contamination by RCF should be prohibited. Breaks should be taken in a separate, designated clean area, and personal protective equipment should be removed and hands washed before eating. Washing facilities to enable workers to maintain an appropriate standard of personal hygiene should be provided.

To prevent secondary exposure from settled fibres, it is important to maintain the workplace tidy. Cleaning should be conducted by a method that prevents spreading of fibres. Vacuum cleaners should be fitted with high efficiency HEPA filtration.

Workers should have adequate personal protective equipment, including respiratory protective equipment, protective clothing, gloves and safety goggles when handling RCF materials. Protective equipment should be removed in a predetermined manner (with the respiratory equipment being the last), cleaned regularly, and stored in a way that prevents fiber contamination.

Sources: ECHA, ILO, NIOSH, BAuA