Introduction
Exposure to welding fume can cause lung disease, so welding fume must be regarded as a substance that is hazardous to health. Employers and the self-employed must protect workers' health by controlling exposure to hazardous substances, according to the requirements of the Control of Substances Hazardous to Health (Amendment) Regulations 2004 (The COSHH Regulations).
The COSHH Regulations require that, before work involving substances hazardous to health is carried out, the risk to health created by that work is assessed and that the steps needed to control the risk are identified and implemented.
Assessing the risks for welding and allied processes will involve estimating, or measuring, whether exposure to the hazardous components present in welding fume is likely to exceed the concentrations given in Guidance Note EH40 from the Health and Safety Executive and known as Workplace Exposure Limits (WELs). Assistance in conducting the risk assessment is provided in this article. Further guidance may be obtained from COSHH Essentials Welding at www.hse.gov.uk/welding/guidance/index.htm
If the risk assessment indicates that exposure is likely to exceed defined levels, exposure must be controlled, at source, using local exhaust ventilation (LEV). If exposure cannot be controlled adequately using ventilation, suitable respiratory protection equipment (RPE), in addition to ventilation measures, must be employed.
When control measures are used, employers must establish procedures to ensure that they are properly used and employees must use the control measures as intended and instructed. Employers must also ensure that control equipment is maintained in efficient working order, in good repair and in clean condition.
Exposure measurement may be required if previous data are not available for a risk assessment, to ensure compliance with exposure limits, to test the effectiveness of control measures such as ventilation or to give guidance on the selection of RPE.
Workers that are regularly exposed to fumes, dust and noxious gases should be the subjects of health surveillance. Consequently, health surveillance will usually be required for welders, unless the risk of exposure is low. The early detection of breathing problems could prevent further damage to the lungs.
The COSHH Regulations require that an employer, who undertakes work that may expose his employees to substances hazardous to health, provides information, instruction and training to allow them to know all the risks to health created by the exposure and the precautions to be taken.
Risk assessment
Performing a risk assessment for exposure to welding fume will involve consideration of the following questions:
What concentration of fume are workers are exposed to?
How long they are exposed for?
What is the likelihood of exposure occurring?
What are the possible adverse effects of exposure?
The answers will identify any requirements for fume control or exposure measurement. A good risk assessment will provide protection against occupational disease but avoid the inconvenience and expense of carrying out over-elaborate precautions.
The risk assessment must be recorded and should indicate the sources of information and the factors considered by the assessor.
It must be reviewed and, if necessary, updated, if circumstances change or it becomes apparent that the original assessment is no longer valid.
The results of a risk assessment must be communicated to employees and to their representative. The safe system of work, developed from the risk assessment, should include not only what must be done but also deal with any consequences that may arise from not following the procedure. For example, if the safe system of work shows a requirement for control measures such as ventilation or respiratory protection, it will be necessary to:
Ensure proper use of the equipment provided
Ensure that the equipment is maintained in good working order
Ensure that workers have received appropriate information and training
Other possible consequences include:
Exposure monitoring
Health surveillance
Employees must have access to their own monitoring results and to the collective results of any health surveillance.
Assessment of exposure
To assess whether exposure is likely to exceed WELs, it will be necessary to gather information on:
The composition of the fume
The composition of the fume determines the level of control that must be exercised to avoid health risks. Fume containing larger concentrations of more toxic components, i.e. those with lower exposure limits, will require control to lower levels. Fume containing carcinogens or asthmagens, e.g hexavalent chromium, will require control to as low a level as is reasonably practicable.
In arc welding, around 90% of the fume originates from the welding consumable. The parent material has only a minor effect on fume composition. Therefore, the consumable is the main factor affecting fume composition. In UK, under Section 6(1)(c) of the Health and Safety at Work Act 1974, manufacturers, importers and suppliers of welding consumables are required to provide sufficient information for their safe use. Typically, the hazard information package supplied with welding consumables comprises a warning label attached to or printed on every carton or package, Welding Manufacturers Association publication WMA236 on the nature and hazards of welding fume, hazard data sheets giving concentrations of the principal components in the fume emitted and other relevant data about the hazards and precautions.
Welding fume composition data can be used to:
- Evaluate gravimetric measurements of exposure to welding fume
- Identify the key component of the welding fume
- Calculate the key component welding fume limit value
These uses, which aid the assessment of exposure and reduce the costs of exposure measurement, are explained fully in Annex B of ISO 15011-4, Health and safety in welding and allied processes - Laboratory method for sampling fume and gases - Part 4: Fume datasheets.
It is increasingly common to arc weld through surface coatings such as primers and to resistance weld through zinc or organically coated steels, oils, adhesives and sealants. In these cases, information on the composition of these coatings and products, given on safety datasheets, may not reflect the composition of the fume emitted sufficiently for risk assessment.
Fume from cutting processes is generally similar in composition to the metal cut, unless a surface coating is present. Precautionary removal of the coating should be carried out when insufficient information on the coating is available to evaluate the risk.
The amount of fume generated
The main factors affecting the amount of fume generated are the process and the process parameters, of which the process is the most important factor. Some processes produce large quantities of fume and others do not, irrespective of the process parameters.
Processes where metal is transferred across an open arc generate the most fume, e.g. MMA, FCA, MIG/MAG welding. TIG and resistance welding do not produce significant amounts of fume. Higher metal removal rates generally generate more fume when gouging and cutting.
The effect of welding parameters is small when compared to the overall effect of the process. Current and voltage are the most important process parameters and often the effect of other parameters stems from the changes that they confer on current and voltage. Generally, higher currents and voltages equate to more fume.
The welding position
The welding position affects the proximity of the fume to the welder's breathing zone and has a major effect on exposure. Welding positions that place the welder closer to, or worst of all, above the plume of fume lead to the highest exposures.
The welding location
The confinement (i.e. size and/or volume) of the workspace is expected to affect exposure. Smaller confined spaces are expected to result in higher exposures.
The duty cycle and duration of exposure
For a given welding situation, lower duty cycles generate less fume and usually give rise to lower exposures. Similarly, if the duration of exposure is short, lower exposure would be expected over an averaged work period.
Fume control
A hierarchical approach to fume control must be taken, as follows:
Exposure must be prevented
Exposure must be controlled using methods, i.e. LEV, other than respiratory protective equipment (RPE)
Exposure must be controlled using LEV plus RPE
If welding is to be performed, total prevention of exposure is not possible. The scope for reducing the quantity of fumes emitted, or for modifying their composition through consumable formulation, or by changing welding parameters, is very limited. Although general ventilation can help control exposure by reducing background levels of fume, it is usually ineffective for the control of welder exposure and may lead to expensive environmental heat loss. Consequently, ventilation that removes fume at source, commonly known as LEV, is recommended for fume control in the welding industry. Extracting the fume at source protects not only the welder but also other workers, by preventing the fume from entering the general workshop atmosphere. There are four main methods of controlling exposure by removing fume at source. These are:
- Adjustable extract hoods
- Extracted benches
- Extracted booths
- Extraction equipment fitted directly to the welding torch
Eight principles of good practice for the control of exposure of substances hazardous to health are set out in Schedule 2A of the COSHH Regulations 2002 (as amended). Approved Code of practice and guidance. If employers apply the principles correctly, exposure should be below any relevant WEL. The eight principles are detailed below:
- Design and operate processes and activities to minimise emission, release and spread of substances hazardous to health;
- Take into account all relevant routes of exposure - inhalation, skin absorption and ingestion - when developing control measures;
- Control exposure by measures that are proportionate to health risk;
- Choose the most effective and reliable control options which minimise the escape and spread of substances hazardous to health;
- Where adequate control of exposure cannot be achieved by other means, provide, in combination with other control measures, suitable personal protective equipment;
- Check and review regularly all elements of control measures for their continuing effectiveness;
- Inform and train all employees on the hazards and risks from the substances with which they work and the use of control measures developed to minimise the risks;
- Ensure that the introduction of control measures does not increase the overall risk to health and safety.
If ventilation control measures are used, it will be necessary to ensure that they are properly maintained by initiating a suitable management system. Such a system must ensure that control measures continue to be effective and that they are used properly. If circumstances change, re-assessment of the risks to health will be required.
Respiratory protective equipment must be used provided and used when welding fume cannot be adequately controlled using LEV. RPE should always be regarded as a last resort solution to an exposure problem and should be used in addition to, rather than instead of, LEV.
RPE is broadly grouped into two classes; respirators and air supplied equipment.
Respirator equipment includes disposable respirators, powered respirators and face masks with filters. They take in contaminated air and filter or clean it before it is inhaled.
Air supplied equipment includes devices such as air fed helmets and self-contained breathing apparatus. They deliver air from a separate source to the welder. If used, RPE should be incorporated into a formal management scheme so that effective controls are put in place and monitoring is undertaken regularly.
Measurement of exposure to fume and gases
The COSHH Regulations, require that, where necessary, the exposure of employees to hazardous substances is monitored in accordance with a suitable procedure. The employer must keep a suitable record of any monitoring carried out and ensure that the record or summary is kept available for inspection.
Monitoring may be required to a) gather information on exposure levels when previous data and experience are not available, b) to ensure compliance with exposure limits, c) to test the effectiveness of control measures such as extraction, d) to give a guide for the selection of RPE.
For welding fume and gases, exposure measurements must be performed according to standard protocols. The standard that applies is EN ISO 10882. The main difference between personal sampling during welding and sampling during other activities arises because a helmet is worn during welding. When a helmet is worn, sampling must be performed behind the helmet, to provide a true indication of the quantity of fume breathed. Measurements may also be carried out at pre-selected points in the workshop. These are known as fixed point measurements. While fixed point measurements do not measure personal exposure, they can be useful in estimating the amount of fume breathed by other workers in the area. They may also be useful in identifying failures of control measures.
Records from monitoring should be readily retrievable for inspection and should be in an easily understood form. The results of personal sampling must be kept by the employer for at least forty years and for at least five years in all other cases.
Health monitoring and surveillance
Exposure to metal fumes and irritating gases, such as nitrogen oxides, has been identified as a cause of chronic obstructive pulmonary disease (COPD). Therefore, health monitoring of welders should be carried out. The early detection of reduced lung function or increased breathing problems could prevent further damage to the lungs. Regular testing by a health professional, possibly involving completion of a questionnaire and an assessment of lung function is appropriate.
Welding fumes that contain hexavalent chromium compounds are generally considered to be respiratory sensitisers, which means that they may cause asthma. Employees that are exposed to a substance that may cause occupational asthma should be under health surveillance. Health surveillance helps prevent the development of asthma by detecting the early signs of ill health. Higher or lower level health surveillance may be appropriate depending on the degree of risk. Further information may be obtained from Control guidance sheet 402, Health surveillance for occupational asthma, from Health and Safety Executive.
Information, instruction and training
The COHH regulations require that an employer, who undertakes work which may expose his employees to substances hazardous to health, provides information, instruction and training to allow them to know the risks to health created by the exposure and the precautions to be taken.
General duties are placed upon manufacturers, importers or suppliers under Section 6 of the health and safety at Work Act 1974, to provide information on the risks to health of substances which they supply. Such information should be distributed by the employer to all employees and others who need it. It is not sufficient to simply hold the information on file.
Employees or their representatives must be informed of the results of risk assessments and of any monitoring carried out, particularly the monitoring of substances that may be carcinogens or asthmagens where an exposure limit has been exceeded. The collective results of any health surveillance must also be provided, but in a form which preserves the anonymity of individuals.
Employees (and other persons as appropriate) must, as described in the General COSHH Approved Code of Practice, be kept well informed in the following matters:
- The nature and degree of the risks to health arising as a consequence of exposure; including factors that may influence risk (such as the substances involved) and factors that may increase that risk (e.g. smoking).
- The control measures adopted, the reasons for these, and how to use them properly.
- The reasons for personal protective equipment and clothing, and the jobs where this is necessary.
- The monitoring procedures, the arrangements for access to the results, and methods of notification if the exposure limit for a carcinogen or asthmagen is exceeded.
- The role of health surveillance, employees' duty to attend, the health surveillance procedures, arrangements for access to individual records and the collective results of health surveillance.
Instruction must be given to ensure that employees know:
- What they must do, the precautions that must be taken and when they must take them.
- What cleaning, storage and disposal procedures are in place, why they are required and when they are to be carried out.
- The procedures to be followed in an emergency.
Training must be provided for the effective application and use of:
- Methods of control
- Personal protective equipment
- Emergency measures
Bibliography
Great Britain. Parliament
SI 2002 No 2677 The Control of Substances Hazardous to Health Regulations 2002. London: The Stationery Office, 2002. ISBN 0110429192. Available online at: www.opsi.gov.uk/si/si2002/20022677.htm
Health and Safety Executive
EH40/2005 Workplace exposure limits 2005: containing the list of workplace exposure limits for use with the Control of Substances Hazardous to Health Regulations as amended. Norwich: HSE, 2005. ISBN 0717629775.
British Standards Institution
BS EN ISO 10882-1:2001 Health and safety in welding and allied processes - Sampling of airborne particles and gases in the operator's breathing zone. Part 1: Sampling of airborne particles. London: BSI, 2001. ISBN 0580348407
British Standards Institution
BS EN ISO 10882-2:2000 Health and safety in welding and allied processes - Sampling of airborne particles and gases in the operator's breathing zone. Part 2: Sampling of gases. London: BSI, 2000. ISBN 0580347052
Health and Safety Executive
Respiratory protective equipment at work: a practical guide. (HSG53). Norwich:HSE, 2005. ISBN 071762904X.
Health and Safety Executive
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Health and Safety Executive
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