Materials containing asbestos
Asbestos is the generic name given to the fibrous forms of naturally occurring silicate minerals. Asbestos-containing materials (ACMs) were used in commercial products because of their high tensile strength, flexibility, low electrical conductivity and resistance to fire, heat and chemicals. Asbestos became prevalent in building construction from the 1950s onwards and was used extensively until it was prohibited in construction. Blue and brown asbestos were banned in 1985, white asbestos in 1999.
When work with asbestos, or work which may disturb asbestos, is being carried out, the Control of Asbestos Regulations require fire and rescue services to prevent exposure to asbestos fibres. Where this is not reasonably practicable, they must make sure that exposure is kept as low as reasonably practicable by measures other than using respiratory protective equipment.
The spread of asbestos must also be prevented. The Regulations (Approved code of Practice and Guidance L143) specify the work methods and controls that should be used to prevent exposure and spread.
Exposure of personnel must be kept as low as reasonably practicable and below the airborne exposure limit. The Regulations specify control limits for all types of asbestos; these can be found on the Health and Safety Executive’s website.
All work with asbestos requires a licence issued by the Health and Safety Executive (HSE), unless it is exempted from current Regulations.
The HSE can issue certificates of exemptions from certain requirements of the Regulations, such as the requirements to hold licenses to work with asbestos or to notify work with asbestos in advance. The exemptions are normally subject to specific conditions such as compliance with a specific method statement.
Any exemption will only relieve fire and rescue authorities of administrative requirements but not of the need to manage their work with asbestos-containing materials to reduce risks as required by Regulations.
The presence of ACMs does not necessarily mean that they will adversely affect the safety of those at the incident. To safeguard human health, the emphasis must be on continuous risk management and the implementation of appropriate and proportionate control measures at all incidents.
Characteristics and classification
Three main types of asbestos have been used in asbestos products: crocidolite (blue) asbestos, amosite (brown) asbestos and chrysotile (white) asbestos. Blue and brown asbestos are amphibole minerals while white asbestos is a serpentine mineral. The two mineral types have different physical properties and characteristics that lead to differences in their hazardous nature and disease potential.
Amphiboles (blue and brown asbestos)
Amphibole fibres are needle shaped and can split to form many new fibres from an initial single unit. The fibres are also more durable than white asbestos fibres and consequently have a greater potential to cause disease.
Serpentine (white asbestos)
Serpentine fibres are curly in nature and will usually split longitudinally when disturbed or subject to impact. Therefore their potential to generate fibres is lower than for amphiboles and their disease potential is also lower.
While the three main types of asbestos are often described in terms of their common names, which are based on colour, in practice this is not a reliable guide to identifying the type of asbestos. Colour is often distorted by deterioration, age, painting and heating. It is also common to have different types of asbestos mixed together.
|Blue (crocidolite)||Brown (amosite)||
|UN 2212 EAC 2X (amphibole)||UN 2212 EAC 2X (amphibole)||UN 2590 EAC 2X (serpentine)|
Inhalation of asbestos fibres is the major hazard to human health. If inhaled, the smallest of the fibres may remain deposited in the lungs. Symptoms may not occur for 15-60 years after exposure. The principal diseases known to be caused by exposure to asbestos fibres are asbestosis, lung cancer, malignant mesothelioma and asbestos pleural disease.
Asbestosis involves fibrous scarring of the lung in which the tissue becomes less elastic, making breathing progressively more difficult. It is irreversible and may progress even after the exposure to asbestos has ended. Asbestosis is an industrial disease arising from high levels of repeated exposure to airborne dust. There is no risk of contracting this disease from normal levels of environmental exposure to asbestos.
An increased incidence of lung cancer has been found amongst people who have worked with asbestos. The increased risk depends on the degree of exposure and is very much greater for smokers than non-smokers.
Mesothelioma is a cancer of the inner lining of the chest or of the abdominal wall. The incidence in the general population is very low; the majority of cases are attributable to occupational or, more rarely, para-occupational exposure to asbestos (i.e. those living in the same house as an asbestos worker).
Asbestos pleural disease
This is a non-malignant disease that causes scarring of the thin membranes lining the lung and chest.
Other diseases and conditions
Asbestos may cause cancer of the digestive tract, colon, larynx, oesophagus, kidney and some types of lymphoma. These asbestos -related diseases may be due to swallowing some of the longer asbestos fibres that are caught in the upper airways and carried to the throat in mucus. However, the risk here is much smaller than those diseases caused by inhalation.
Skin and eye irritation may arise from acute exposure to fibres.
Hazards from chrysotile (white asbestos)
Crocidolite (blue), amosite (brown) and chrysotile (white asbestos) all cause cancer and have been classified by the International Agency for Research on Cancer as category 1 human carcinogens. It is recognised that chrysotile (white asbestos) is less potent (i.e. has a lower cancer risk) than the other types but it is still a carcinogen. In addition, many asbestos products contain a mixture of asbestos types and exposure to chrysotile will not be in isolation. Consequently all three forms should be treated the same.
Hazards posed to the general public at serious fires
In all cases of incidents involving asbestos-containing materials it is important to put the health risks to the general public into perspective. Asbestos is a naturally occurring substance and also a widely distributed industrial pollutant and consequently is found in low to moderate levels everywhere in the UK. These levels can be as high as 1000 fibres per cubic metre of air in urban or industrial areas. Exposure to these background levels is therefore unavoidable (Source data from the World Health Organisation)
Material containing asbestos that is in good condition and left undisturbed and in place cannot cause ill health, as fibres will not be released. Handling or touching ACMs in good condition will also generally not present a risk. However, handling would require precautionary controls (such as wetting and personal protective equipment) in case the material had been damaged or crumbles/breaks up during movement. In such situations fibres are likely to be released.
The key factor in the risk of developing an asbestos-related disease is the total number of fibres inhaled. Inhaled fibres can become lodged in the chest tissue and the body’s natural defences may not be able to easily break them down.
Asbestos will be encountered in a number of products (ACMs). The asbestos form and material that the fibres are mixed with, will define the level of hazard.
- Lower hazard - means asbestos cement products and textured coatings only. With these products, the asbestos is firmly embedded and the fibres are more difficult to release.
Other ACMs are also classified as minor or less-significant hazards under the Regulations (asbestos paper, rope seals, etc.) but they have not been included in the lower hazard category in the hazard identification process for fires because of their increased potential to release asbestos fibres in a fire
- High hazard - all other ACMs.
Prior to being banned, asbestos was predominantly used in the building industry as heat resistant insulation, lagging and roof sheeting. Asbestos is likely to be present in the vicinity of heating and ventilation systems, pipe work, boilers, structural insulating panels or as a roofing material.
It is estimated that approximately six million tonnes of asbestos has been used in the UK in the last 100 years. It may be found in the form of cement sheeting, impregnated cloth and rope or sprayed onto structures as slurry. Composites containing asbestos have also been used in decorative coatings and cladding for both internal and external use.
|High hazard (N.B. . if disturbed or involved in fire)|
Widely used mixtures containing asbestos that were used to provide fire protection, acoustic properties, heat and condensation control by:
|Asbestos insulating boards (AIB)||Used for fire protection and thermal insulation (e.g. ceiling tiles, partition walls, soffits, service duct covers, fire breaks, heater cupboards, door panels, lift shaft linings, fire surrounds, backing panels for radiators, heater and boilers).|
|Asbestos insulation||ACMs which were not applied as coatings in practice. They include preformed sections for pipe insulation, laggings, void infills and packing around cables that pass through floors, millboards used for electrical as well as thermal insulation.|
|Asbestos cement products||These generally contain between 10% and 15% asbestos and the potential for fibre release is usually low. However, contamination can arise when asbestos cement is damaged or removed without suitable controls. Cement products include flat or corrugated roof sheets, wall cladding, guttering and downpipes, water tanks, bath panels, boiler and incinerator flues, fire surrounds, etc.|
|Certain textured coatings||Such as 'Artex' prior to the mid-1980's)|