|Asbestos Overview and Handling Recommendations (GTZ, 1996)|
|Part VII Annexes|
14 December 1994
Scope: This information is provided in compliance with the
Health and Safety at Work
Etc. Act 1974. Section 6 (as amended by the Consumer Protoction Act, 1987)
'X' Asbestos Cement Corrugated Sheets for Roofing and Cladding of Industrial and Agricultural Buildings
'Y' Asbestos Cement Slates for Roofing and Vertical Cladding of Houses and other Buildings such as Schools, Hospitals, Offices etc.
Asbestos Cement corrugated sheets and slates are cement-based materials reinforced with chrysotile Asbestos (white) fibres. They contain approximately 10-12 % chrysotile Asbestos fibre and 88-90 % Portland Cement mixed with water.
Asbestos Cement corrugated sheeets are light grey in colour in their natural state, but some sheets are painted with a coloured acrylic surface coating.
Slates have a carbon black pigmented base and an acrylic surface coating.
Corrugated sheets have a density of 1500 kg/m³ and a bending strength of 4,400 N/m width, when tested at 1100 mm clear span. Asbestos Cement slates are fully compressed and have an average bending strength of 27 N/mm² at a density of 1950 kg/m³. Industrial pollution will cause a slight softening of the surface of natural Asbestos Cement sheets.
Asbestos Cement products are non combustible when tested in accordance with BS476: Part 4 but are not suitable for fire resisting applications and should not be exposed to direct flame.
Potential Health Hazards
Inhaling dust which contains Asbestos fibres can seriously damage health and should be avoided.
The diseasses which may arise from the inhalation of Asbestos dust are Asbestosis - a form of fibriosis of the lungs, Lung Cancer, and Mesothelioma - a cancer of the lining of the chest or abdominal cavities. Because of synergistic effect of tobacco and Asbestos, smoking greatly increases the risk of Lung Cancer in Asbestos workers.
Provided recommended working practices are followed when working with Asbestos cement any risk to health will be very small.
The Control of Asbestos at Work Regulations (CAWR) 1987, as amended by The Control of Asbestos at Work (Amendment) Regulations 1992 apply to everyone at risk from work with Asbestos and extend specific statutory protection to all those who encounter Asbestos at work or may be affected by work activities involving Asbestos.
In particular they place duties on employers to prevent or reduce to lowest level reasonably practicable the exposure of employees to Asbestos and the spread of Asbestos from the workplace.
The regulations set Control Limits and Action Levels for Asbestos. The Control Limits are the maximum concentrations of airborne Asbestos fibres averaged over any continuous 4 hours or 10 minute period, to which employees must not be exposed without appropriate protection.
The Control Limits for chrysotile Asbestos are 0.5 fibres/ml over 4 hours or 1.5 fibres/ml over 10 minutes. If after all reasonably practicable measures have been taken to prevent and/or reduce the level of exposure, it still reaches or exceeds the Control Limit, suitable personal protective equipment, (which includes respiratory protective equipment, protective clothing and footwear) must be provided.
The Action Level is expressed as the cumulative over any continuous period of 12 weeks. (It is the exposure in fibres/ml multiplied by the number of hours over which the exposure occurs expressed as fibre hours/ml. Those exposures are added together to give a total cumulative exposure).
The Action Level for chrysotile Asbestos is 96 fibre hours/ml.
If this Action Level is liable to be exceeded additional regulations in CAWR come into operation namely notification of work with Asbestos (Regulation 6), medical surveillance (Regulation 16) and designation of works areas (Regulation 14).
Guidance on the Regulations is provided in the Approved Code of Practice on The Control of Asbestos at Work Regulations, as amended by The Control of Asbestos at Work (Amendment) Regulations 1992.
Further guidance is given in EH36 Work with Asbestos Cement and MS13 Asbestos.
The first decision employers should make is whether it is reasonably practicable to avoid exposure to Asbestos altogether by using a substitute product.
If Asbestos cement must be used the employer should make an assessment of the likely exposure before starting work. The assessment should normally be in writing, unless the work is simple, on a small scale and exposures are low so that the assessment can be easily reported and explained. The assessment should cover the type of work and duration; the steps to be taken to prevent or reduce the exposure to employees to the lowest level reasonably practical; the release of Asbestos to the environment; the provision and use of protective equipment and its cleaning (if appropriate); the procedures for removal of waste and the procedures for dealing with emergencies.
Personal Protective Equipment
Approved Repiratory Protective Equipment (RPE) should be worn if the exposure is likely to exceed the Control Limit. All personal protective equipment provided, including RPE, should comply with the requirements of the Personal Protective Equipment (EC Directive) Regulations 1992, and bear the European Communities conformity mark 'CE'. Until the new legislation comes into effect, employers may continue to buy equipment which does not carry the 'CE' mark, and existing PPE can continue in use. In these cases, RPE must be of a type approved by, or conform to a standard approved by HSE.
Workers should be trained how to use respirators. The equipment should be maintained in good working order, cleaned and disinfected after use and stored in a suitable locker or container.
Workers should be provided with Protective Clothing if a significant quantity of Asbestos is liable to be deposited on their clothes. Protective Clothing will not be required where dust levels are very low and exposures are brief and there is little risk of Asbestos sticking to clothing. This may include activities such as handling of new Asbestos cement, hand drilling of damp Asbestos cement sheets or scribing and breaking of slates which are unlikely to result in the deposit of a significant quantity of fibre. Industrial working clothes such as jackets and overalls may be regarded as suitable. At this level of contamination washing facilities can be shared with other workers.
As the amount of cutting, breakage and drilling increases there will be a point where a significant quantity of Asbestos is deposited on the clothing and Protective Clothing, which includes clothing and footwear, must be provided.
Protective Clothing contaminated with Asbestos should either be disposed of after use, as if it was Asbestos waste or sent to a laundry equipped with facilities capable of handling Asbestos contaminated clothing. This should never be taken home for cleaning.
Protective Clothing should be removed before leaving the working area, on all occasions including meal breaks, other breaks and completion of work.
Air monitoring should be carried out periodically to check the level of exposure, the effectiveness of controls and the adequacy of protective equipment, where exposure exceeds or is liable to exceed the control limit.
This can be once a year provided that the results of the two preceding measurements have not exceeded half the control limit and there is no substantial change in the work methods and workplace conditions.
Where exposures are low and not likely to approach the control limit, monitoring may not be appropriate. Guidance on typical fibre levels for work with Asbestos cement products is contained in HSE Guidance Note EH35 'Probable Asbestos dust concentrations at construction processes'.
Prevention of exposure is the first objective and Asbestos products should only be used where a less hazardous substitute is not reasonably practicable eg. where substitutes cannot meet a critical technical performance requirement of an application. If this is not possible, precautions should be taken to keep exposure as low as reasonably practicable and to ensure that workers are adequately protected.
Information, instruction and training should be provided so employees are aware of the risks and precautions.
Transport and Storage
Other than good haulage practice in securing the consignment, no special transport precautions need to be taken with Asbestos Cement products. Products should be appropriately labelied including specific saftey instructions. Sheets should be stored as near as possible to the area where they are to be used, and away from roadways and moving vehicles. They should be stacked horizontally on level, firm ground on timber bearers.
Handling and Use
Low levels of exposure will arise if the following precautions are taken:
Use exhaust ventilation equipment where reasonably practicable;
Keep the material wet wherever possible;
Carry out sawing and drilling out in the open air;
Use hand saws and low speed reciprocating saws for mitring and cutting of corrugated sheets. Use hand drills in a downward direction for drilling sheets and slates;
Scribe and break slates;
Keep the work areas clean and tidy, take care to prevent the spread of contamination and accumulation of waste materials and clean using a dustless method such as washing or by using vacuum cleaners suitable for Asbestos.
Substantial releases of dust will be created in excess of the Control Limit, if work is carried out with power tools such as cutting and grinding discs and high speed circular saws. These should not be used under any circumstances if exhaust ventilation has not been provided.
Asbestos Cement sheets are fragile within the meaning of Regulation 36 of the Construction (working places) Regulations 1966, roof ladders and crawling boards must be used.
Asbestos Cement dust should be vacuumed at frequent intervals during working so there is no accumulation of dust. Only vacuum cleaning equipment fitted with high efficiency filters such as type H (BS 5415) vacuum cleaners are suitable for use with Asbestos. Where vacuuming is not possible, the dust should be dampened and collected while still damp and bagged in double plastic bags, sealed and labelled.
Small pieces of Asbestos cement waste should be placed in double plastic sacks which are tied or sealed. Larger pieces should be wrapped in plastic sheets and placed in a sealed container or securely sheeted skip. The containers should be labelled and removed by a registered waste carrier to a licensed waste manager.