Document XRVJR00Xe4DayGa61VnGk8jJx

Guidance Note EH10 from the Health and Safety Executive Asbestos control limits and measurement of airborne dust concentrations Environmental Hygiene/10 (revised April 1983) Thos^ Guidance Notes are published under five subject headings Medical. Environmental Hygiene. Chemical Safety, Plant and Machinery and General. INTRODUCTION 1 This Guidance Note is a revision of Environmental Hygiene/10 (December 1976). Asbestos - hygiene standards and measurement of airborne dust concent rations. It replaces the information given in the earlier document and it sets out in para 9 the control limits recommended by the Advisory Committee on Asbestos (ACA)' which have been agreed by the Health and Safety Commission in the light of information available to them. The ACA believed that it was inappropriate to continue to control exposure levels in terms of a 'hygiene standard' as has been done hitherto. They believed that as the objective to be achieved was the controlled and progressive reduction of the levels of exposure, the term 'hygiene sttndard' should be replaced by 'control limit'.* 2 It gives guidance on the exposure criteria the Health and Safety Executive's inspectors will use in determining whether, in their opinion, certain of the requirements of the Asbestos Regulations 1969s (particularly Regulation 7 and 8) and Sections 2,3 and 4 of the Health and Safety at Work etc Act 19745 are observed, (t is of course for the Couits alone to give a binding decision on the inter pretation of the law. 3 The Health and Safety Commission are considering further measures for the control of exposure to asbestos dust In addition, the methods of measurement are under review If further changes are to be made, this document will be revised. 4 Pari 1 deals with current legislation and control limits. Parts 2 and 3 explains how the necessary measurements may be made. Consequently the title of this Guidance Note a altered hom the previous edition in this respect. The senes number EH 10 is rtittned PART 1 LEGISLATION AND APPROVED CODE OF PRACTICE 5 The Asbestos Regulations 1969 apply to all factories and to other premises to which Part IV of the Factories Act 1961 applies, including construction sites, electrical stations and ships under construction or repair etc. where a process involving asbestos is undertaken, except a process in which asbestos dust cannot be given off. 'Asbestos dust* is defined in Regulation 2 as "dust consisting of or containing asbestos to such an extent as is liable to cause danger to the health of employed persons". In determining whether "asbestos dust cannot be given off", the test should be applied before pre cautions are taken, for example, before local exhaust ventilation is provided. 6 Where the Asbestos Regulations do not ipply. there is a duty under the Health and Safety at Work etc Act 1974 (HSW Act) to ensure, so far as is reasonably practicable, the health, safety and welfare of persons at work and to protect persons not at work against risks to health or safety arising out of or in connection with the activities of persons at work, and similar standards to the Asbestos Regulations should be adopted. 7 The Approved Code of Practice Work with asbestos insulation end asbestos coating4 provides practical guidance on the relevant legislation 1 * concerning the risk to health from asbestos during work with thermal and acoustic insulation including structural fire protection and sprayed coating. Medieal avidenee 8 A relationship between exposure to asbestos dust and asbestosis, asbestos related bronchial cancer and mesothelioma has been recognised for many years. The Health and Safety Commission's Advisory Committee on Asbestos reviewed in 1976-79 all the evidence available to it at that time relating to the health risks of different types of asbestos. It concluded that there is evidence that all types of asbestos fibre are associated with asbestosis, cancer of the lung and gastrointestinal tract, and mesothelioma (cancer of the lining of the chest end abdomen). However, it appeared that a substantial proportion of mesotheliomas in this country are probably related to exposure to crocidolite (blue asbestos) or amosite (brown asbestos). Tfie ACA concluded that exposure to chrysotile alone has rarely been shown to cause mesothelioma. However, it considered that any change in industrial practice in the direction of the production of more finely divided chrysotile fibre is likely to increase the health risk. As far as cancer is concerned, the ACA concluded that there is an increase in risk with increasing dose, but that for all types of asbestos, `no safe level' of exposure could be identified. Further information on the medical effects f working with different types of asbestos and Health for the-purposejnf the Asbestos Regwfetions.-t.9C9 is precautions are sat out in HSE Medical Scries Guidance Note MS 13, Asbestos*. published every year as Form F24S6*. Onffc approved equipment which is suitable for the antiefretad^ 0 The Health and Safety Commission have decided that the ^Hewing control limits, recommended by the Advisory Committee on Asbestos should be adopted with effect from 1 January 1983: conditions with a nominal efficiency suA that the concentration of asbestos in the air breathed by the worker does not exceed the relevant control limit. Guidance on the selection, use, cleaning, maintenance and storage of respiratory protective equipment is contained for dust comi-ting of or 0`2 fibre/ml when measured in the Approved Code of Practice Work with asbestos containing any crocidolite as a time-weighted average insulation and asbestos coating*. Additional guidance on over any 4-hour period the selection end use of respiratory protective equipment for dust consisting of or 0*5 fibre/ml when measured can be obtained from local offices of the HSE. eontiir-ng any amosite as a time-weighted average but not crocidolite for dust consisting of or containing other types of asbestos but not over any 4-hour period 1 fibre/ml when measured as a time-weighted average over any 4-hour period. PART 2 MEASUREMENT OF AIRBORNE ASBESTOS General crocidolite or amosite 16 Air monitoring is necessary to ditermine whether or 10 The control limits set out in pare 9 do not represent safe le.eh which once attained make further improve ments in dust control unnecessary. They represent the upper limits of permitted exposure as determined by personal air sampling techniques (see paras IS to 24) where there is still a statutory duty to reduce exposure to a lower level where this is reasonably practicable. not control of the personal exposure of workers to the relevant control limit for asbestos is being achieved; and also to identify those areas where improvements in the system of work or engineering control-equipment need to be made to ensure that the personal exposure of workers is reduced to thc-minimum that is reasonably practicable. 11 The Health and Safety Executive win use thecriteria set out m paras 9 and 10 in assessing whether there is a compliance with the relevant requirements of the Asbestos Regulations and the HSW Act. 12 For assessing compliance with the control limits, sampling should wherever possible, be carried out for the whole 4-hour period. However, where this is not reason ably practicable or appropriate, sampling should be earned out for the actual period of exposure, end this result be used for assessing compliance as though the control limit was a time-weighted average for the period of sampling. Where both long-term and short-term samples covering the same 4-hour period are available (see para 13!. the results of the long-term sample should be used for assessing compliance. 17 The air sampling strategy should be developed and executed by a person, or j.i*ons, who have adequate information, instruction and training for the task so that they can carry it out effectively. Persons developing the strategy will need to be made aware of ati asbestos processes at the workplace and will in particular need information and instruction about: (a) the piant and machinery used for transporting and processing asbestos - containing materials: (b) the composition of materials (e g. type of asbestos); (c) process details; and (d) individual employees' tasks. Membrane filter method for airborne asbestos dust 13 In order to comply with the statutory duty toreduce exposure to a lower level where this is reasonably practi cable. it is necessary to consider whether a further overall reduction in exposure can be achieved end. in particular, to identrfy any periods, of peak exposure. The identifi cation and evaluation of these peaks will require sampling periods of less than 4-hours. Engineering control and provision of respiratory protective equipment 14 These control limits need to be achieved by means of engineering control where reasonably practicable. Where it is not reasonably practicable to maintain the personal exposure of the worker below the numerical control limits in para 9 by means of engineering controls then suitable approved respiratory protective equipment must be provided and worn, 15 A list of respiratory protective equipment approved 18 Paragraphs 19 to 24 describe the method used to determine the concentration of airborne asbestos dust to which persons are exposed at work. 19 Samples for assessment are taken by drawing a known volume of dust-laden air through a 25 mm diameter cellulose ester membrane filter of pore size 0*8 to 1*2 pm using a battery-operated pump. The membrane filter method is most accurate for deposit densities on the filter of between 100 and 1000 fibres/ mm2, and this should be taken into account in choosing the flowrate. For example, this density range would require a flowrate for a 4-hour sample onto a 25 mm filter from a concentration of 1 fibre/ml of between about 0*15 and 1*5 litres/min. The flow should be measured and controlled so that the accuracy of the total volume sampled is known to within 5%. This normally requires the use of a calibrated flowmeter for all measurements. Any flowmeter built into the pump may not be i jfficiently accurate, but can still be used during sampling as an indicator that the instrument is working. 20 The filter holder should be of a ties.gn that will give a uniform deposit at the flowrate u:.d. To minimise contamination, the filter should be loaded into the holders, unloaded and analysed in an area free from asbestos contamination. The loaded heads should be covered with a protective cap during transport through asbestos-contaminated areas, 21 The pump should be attached to a loaded filter holder using flexible tubing, and the flow adjusted to the chosen rate using a caiibrated airflow meter. The pump should be allowed to run for 15 minutes before sampling to allow the flowrate to steady - experience may show th.s to be unnecessary with some types of modern stabilised flow pumps. A clean filter holder loaded with a clean filter should then be fitted and the flow readjusted to the required rate. The pump should then be switched off and a protective cap fitted to the filter holder. 22 The filter holder should be fixed to the upper iapei or shoulder of the worker's clothing within 300 mm of his nose or mouth. Wherever possible, the same sampler position should be adopted for each worker. Some circumstances may lead to a higher concentration to be expected on one side of the worker than the other, in which case the sampler should be positioned on the side expected to give the higher result. At the start of the sampling period, the protective cap should be removed from the filter holder the pump started, and the time noted. The flowrate should be checked periodically le.g. hourly) during sampling and readjusted to the chosen rate. Operating experience may show this to be unnecessary with some types of pump, but it is still advisable to check working conditions and that the equipment is functioning. Relevant information for use in interpreting the results (e.g. work in progress, conditions of plant) should be recorded during the sampling period. At the end of the period the time should be noted, the pump switched off, end die protective cap replaced on the filter holder. 23 After the sampling period, the filter may be carefully removed from its holder, and placed in a clean degreased tin or simitar holder for transport. The clean, unexposed edge of the filter can be secured to the tin with adhesive tape, and subsequently removed with a surgical scalpel. Alternatively, the filter may be left in the holder, with the protective cap firmly in position, for transport. Evaluation of samples 24 Tne term 'fibre* referred to in para S means particles of length greater than 5 pm, diameter of less than 3 pm and having a length to breadth ratio of at least 3:1, observed by transmitted light under phase contrast conditions at a magnification of approximately 500x, using a 40x objective with a numerical aperture of 0*65 - O'70. against a background with r.i. between 1-43 - 1*50 The number of fibres conforming to this definition should be counted on a representative ares of the filter using phase contrast optical microscopy, and the airborne concentration calculated from the number counted, the ares examined, the area of the filter, and the volume of air collected. The procedure is outlined in Technical Note 1 of the Asbestosis Research Council*. It is important to ensure that the microscope equipment is of satisfactcry standard and is properly adjusted (this can be checked with a phase contrast test slide.) Other methods of monitoring airborne asbestos dust 25 The control limits referred to in pars 5 refer to the personal exposure of worker, as determined by the method set out in paras 20 to 25. Additional valuable information can be obtained from other monitoring methods which give an indication of the level and sources of airborne asbestos dust in the workplace. 26 instruments are available which give an immediate reading of the total dust concentration and are useful for providing an indication of the general dustiness of the air. Where it is possible to establish a correlation between the results of such instruments and the membrane filter method in particular workplaces, the instruments can provide a rough and ready measure of asbestos dust in the eir. For example, to look for sources of dust emission, either from process plant or generated during manual handling, or to check that control equipment is operating satisfactorily. Short-term static samples using the membrane filter method can provide similar information. 27 The dust lamp (a device for illuminating by forward scattering light) has the advantage, over other techniques, of making visible very fine dust particles thus enabling the observer to identify sourcas of dust emission and to follow movement of the dust cloud. The method is described in Certificate of Approval No API (F2363)'. The dust lamp may be used in conjunction with video equipment to enable a critical appraisal of existing work practices and engineering controls to identify ways of reducing dust emission. PART 3 SAMPLING AND ANALYSIS OF BULK MATERIAL 28 This Note now outlines acceptable techniques for sampling and analysis of bulk materials for use with the Approved Code of Practice Work with asbestos insulation anti asbestos coating* 29 Sampling and analysis of the bulk material is necessary first, to determine the presence of asbestos and second, to identify the type of asbestos. It is parti cularly important that where any crocidolite is present, the more stringent precautions should be applied and notification made in accordance with Regulation 6 of the Asbestos Regulations.2 If, however, employers find it more convenient to treat the material as thoi-jh it was crocidolite. and to provide precautions appropriate for this type of asbestos, then sampling end analysis need net be undertaken. 006208 30 The type and quantity of asbestos in old installations 2 The Asbestos Regulations 1969. SI 1989 No 690 will frequently vary from one part to another, and it HMSO ISBN 0 11 090690 X is essential that the samples collected are representative. Sampling should take into account any apparent The Health and Safety at Work etc Act 1974, variations in the material, including changes through the Chapter 37, depth of the insulating layers. Those taking the samples HMSO ISBN 0 10 $43774 3 must be protected from exposure to airborne asbestos dust. Soaking will greatly reduce the emission of fibre during sampling. Wet bulk samples can be analysed 4 Health and Safety Commission. Work with asbestos insulation and asbestos coating. Approved Code of without difficulty. The samples should be transported Practice and Guidance Note and taxi of the Asbestos in sealed, impervious containers double if necessary, and Regulations and extracts from the Health and Safety adequately identified. at Work etc Act. (Revised June 1983) 31 The types of asbestos present cannot readily be HMSO ISSN Oil 883687 0 identified by the appearance or colour of the bulk B Health and Safety Executive. Medical`Series sample, particularly if other materials are present. Guidance Note MS13,A*6e*fe* Damping the surface may help to locate areas containing HMSO (under revision) crocidolite (although the absence of blue colour does nor guarantee absence of crocidolite}. Crocidolite may be 0 F2486 (1982) (revised) Certificate of approval significantly changed in appearance by the action of heat. (Respiratory Protective Equipment) 1982 Fibres can be identified using optical microscopy'10, HMSO ISBNO 11 883680 3 and an estimate of the proportion of the minerals in the sample can be obtained using X-ray diffraction10,11. Accurate X-ray diffraction measurement is difficult at low levels (less than a few per cent) as it canndt in general distinguish between fibrous and non-fibfous 7 Technical Note 1 of the Asbestojis Research Council.-AIC, Sacfcviile House, 40 Piccadilly, London .W1V9PA forms of mineral, so that this analysis should'be supported by a microscopical examination. Other techniques, such as electron microscopy and infra-red 8 F2363. Certificate of approval No API (particulars to be contained in report of the result of thorough examination and test of exhaust ventilation system] spectroscopy can also give useful information. HMSO ISSN 0 11 883354 5 FURTHER ADVICE 1 L J Monkman, Ann. Occup. Hyg., 22 (1979) 127-139 32 Anyone needing further advice from the HSE on any aspects of this Guidance Note (e.g. training of persons to carry out air sampling, obtaining suitable sampling equipment, identifying analytical laboratories) is advised to consult, his local HSE inspector who should be able to assist either directly or by putting the enquirer in touch with an appropriate person. 10 Technical Note 3 of the Asbestosis Research Council. A1C, Sackville House, 40 Piccadilly. London W1V 9PA 11 M Teylor, The Analyst. 103 (1978) 1009-1020 FURTHER INFORMATION REFERENCES 1 Health and Safety Commission. Asbestos -- Volume %. Final Report of the Advisory Committee HMS1 ISBN 0 11 883293 X This Guidance Note is produced by the Health and Safety Executive. Further advice on this or any other publications produced by the Executive is obtainable from Baynards House. 1 Chepstow Place, London W2 4TF, or from Area Offices of the HSE. HMSO SOp net Crown copyright 1983 -- Printed in Englendtof Her Majesty * Stationery OHice by Rofeendene Ltd. Ame'Sham 006209