Dust and aerosols - welding fumes

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Klaus Kuhl (Kooperationsstelle Hamburg IFE GmbH), Mario Dobernowsky (Kooperationsstelle Hamburg IFE GmbH)


Introduction

Welding is a generic term for joining pieces of metal at joint faces rendered plastic or liquid by heat or pressure or both [1]. These processes generate several health and safety risks for the welders and workers nearby, such as fire and explosion risks, burst of pressurised cylinders, heat and burns, electrical risks, risks from ultraviolet and other electromagnetic radiation, working in awkward positions, and fumes that may enter the breathing zone of the welders or their colleagues.


Welding and OSH

Health and safety can be affected by welding operations:
(i) welding generates fumes that may cause airway disease and contain carcinogenic substances, whereby some welding technology may create high amounts of fumes,
(ii) hot surfaces and ultraviolet rays,
(iii) many welders have to work in confined spaces and/or in awkward positions,
(iv) restrictions for movements and increased load because of the heavy protection welders have to wear or carry, and
(v) working on site may include working without shelter exposed to rain, which increases the risk of electric shock considerably.

These risks can be considerably reduced by automated processes and welding robots. The different types of welding machines, substrates, fillers and the various types of working conditions create many different scenarios. This article addresses health issues linked to exposure to welding fumes, preventive measures including exhaust systems, low fume generating welding, training of movements that avoid breathing in of fumes, and helmets with integrated air supply. It also presents risk assessment and tools that can be used by SMEs and an outlook indicating the most important trends in welding and the related health issues.

Exposure to hazardous substances related to welding

There are a variety of different types of welding processes[2] used in industry. The type of process used will impact on the nature and extent of dangerous substances produced in welding fumes. Thus the composition of welding fumes will depend on the substrate, the filler material, the possible use of separate electrodes as in TIG welding, gases used for heat generation, gases or materials used for focusing the arc, and shielding of the arc and the bead against oxygen, possible coatings of the substrate, possible dirt on the substrate and on the adjustment of the welding machine or torch.

Depending on these factors, welding fumes may contain a large variety of particles and gases that pose hazards as listed in the following table.

Table 1: Welding technology and generated hazardous substances

Welding technology Description of welding technology Particle emission rate (mg/s) Hazard class of particle emission Other exposures
Substances that place strain on respiratory tract and lungs Toxic or irritating substances Carcinogenic substances
Submerged arc

Usually an automated process

Flux shielded arc welding.

A blanket of granulated flux is deposited on the workpiece, followed by a consumable bare metal wire electrode. The arc melts the flux to produce a protective molten shield in the welding zone.

< 1 low low low Ozone, nitrogen dioxide
Gas welding (autogenous procedure)

Manual process

The torch connected to an oxygen and an acetylene cylinder melts the metal surface and filler rod, causing a joint to be formed on solidification. < 1 low low - Nitrogen dioxide, carbon monoxide
TIG, tungsten inert gas welding

Manual process but also used in automated, robot operated processes

Gas shielded arc welding.

The tungsten electrode is non-consumable, and filler metal is introduced as a consumable into the arc manually.

< 1 low medium medium Ozone, nitrogen dioxide, carbon monoxide
Laser welding without filler metal Laser beams can be used in industrial applications requiring exceptionally high precision, such as miniature assemblies and micro techniques in the electronics industry or spinnerets for the artificial fibre industry. The laser beam melts and joins the workpieces. 1 to 2 medium high high X rays at high voltages
MIG/MAG metal inert/active gas welding

(low energy, pulsed current machines)

Manual process but also used in automated, robot operated processes

Gas shielded arc welding.

The electrode is normally a bare consumable wire of similar composition to the weld metal and is fed continuously to the arc.

1 to 4 low medium medium to high Ozone (especially in MIG-welding of aluminium materials),

carbon monoxide with MAG welding with CO2shield gas of unalloyed/low-alloy steel

Shielded metal arc welding (SMAC); “stick” arc welding; manual metal arc welding (MMA); open arc welding Flux shielded metal arc welding.

Uses a consumable electrode consisting of a metal core surrounded by a flux coating

2 to 8 high high high Nitrogen dioxide
MIG (general) Gas shielded arc welding. 2 to 8 high high high Ozone in MIG-welding of aluminium materials
MAG (solid wire),

Flux-cored wire welding with shield gas (MAG)

Gas shielded arc welding. 6 to 25 high high high Carbon monoxide with MAG welding and CO2 shield gas of unalloyed/low-alloy steel
MAG (flux-cored wire),

flux-cored wire welding without shield gas

Gas shielded arc welding.

Uses a flux-cored consumable electrode; may have carbon dioxide shield (MAG).

> 25 very high very high very high Carbon monoxide with MAG welding with CO2shield gas of unalloyed/low-alloy steel
Autogenous flame cutting

Manual and automated process, also robot operated

The metal is heated by a flame, and a jet of pure oxygen is directed onto the point of cutting and moved along the line to be cut. > 25 very high very high very high Nitrous gases

Source: adapted from Platcow and Lyndon [1] and from TRGS 528 [3]

Annotations: The Emission rate column presents empirical values which can be reduced in individual cases by optimising the process parameters. TIG welding: figures given according to exposure description published by the German accident insurance associations

Other hazardous substances that could be part of the welding fumes are generated from coatings or impurities, such as epoxides, isocyanates, aldehydes [3].

Prevention and control measures

A large survey in the Netherlands showed that the calculated chance at exceeding the (former) OEL for welding fume of 3,5 mg/m3 was 80% in a group of 53 welders [4]. Thus, for the current OEL of 1 mg/m3 this would have been even much higher – close to 100%. Major factors determining exposure were relative welding time (relative to total work time), the position of the head of the welder (e.g. bent over the rising fume) and whether or not they worked in confined spaces.

This underlines the need to establish effective prevention and control measures, that are based on a risk assessment and follow the generally accepted hierarchy of control measures (see also: The hierarchy of control measures regarding dangerous substances).

Avoidance of risks and elimination of hazards – choosing a welding procedure

All welding processes involve certain risks for the welders, the colleagues nearby, or – in case of automated welding – for the machine operators and the maintenance workers. Elimination would require choosing completely different processes. One technical option is joining by bolting pieces together. This involves more time and resources, generally the application would be disproportionate in terms of effort and achievable results. The usual measure is therefore to minimise the risks and put means of separation between the source and the workers in place. Another possible alternative are strong adhesives. Such adhesives create new risks, such as skin and sensitising risks (see also: Substitution).

Also the selection of non-stainless steels would avoid the generation of carcinogenic fumes, however, this is not always possible as it may lead to increased corrosion and related maintenance and replacement problems.

The first option is to select a welding technology that would generate the least amount of hazardous substances. The table above (1) can be used as a guideline regarding particles generated by the welding process:

Where possible the processes: submerged arc (automated welding), gas welding or TIG welding should be selected. If MIG/MAG welding is necessary, modern welding machines with pulsed current should be used, as these produce considerably less welding fumes as compared to the older types of machines. Another option, that is however, rarely applicable in small companies, could be the automatisation of the welding process, e.g. by a robot.

Technical measures to minimise hazards and to separate hazards from bystanders

An optimum adjustment of the machines is necessary (consult the manual) as deviations will increase the amount of hazardous substances generated.

Before welding on coated or dirty material, the coating and dirt in the areas to be welded should be removed thoroughly. Paint coatings may contain nanomaterials.

In parallel to these efforts, the hazardous substances should be kept away from the welders and their near-by colleagues, who are not performing welding tasks, by separating work areas or using ventilation.

Various types of Local Exhaust Ventilation (LEV) are on the market:

  • work benches with downdraft ventilation,
  • use of hoods; large hoods or small moveable hoods,
  • tip-extraction (on the welding equipment),
  • shield extraction,
  • new developments such as smart exhaust arms that follow the welding progress automatically.

The best solution in each given work situation has to be carefully established. It is strongly recommended that expert guidance is sought for the selection and installation of the ventilation[5].

Depending on the type of local exhaust ventilation in use, frequent re-adjustment may be necessary as the work progresses. An alternative could be provided by extraction integrated in the torch or mounted directly on the torch, or welder protection shields with integrated extraction. The effectivity of the extraction would be the better the nearer the nozzle is put to the source of the welding fume. However, at a certain point, it would compromise the quality of the welding bead as it would take away some of the shielding gases. An ideal position is to have it not farther away than one diameter of the nozzle. An HSE-report describes high capture efficiencies of more than 90% for on-tip extraction, but studies during actual working practice in Dutch companies only established a 50% efficiency. [6]

Exhausted air has to be replaced by fresh air. The extracted air at workplaces where welding work involves the emission of carcinogenic or mutagenic substances or substances toxic to reproduction of category 1 or 2 (especially with the use of chromium- and nickel-bearing materials) must not be fed back into the workshop (see also: Carcinogenic, mutagenic, reprotoxic (CMR) substances).

Maintenance of machinery and workplaces

The employer has to ensure that all machines and devices are in appropriate conditions and that they are serviced and checked regularly.

Workplaces have to be cleaned by a suitable and tested industrial vacuum cleaner.

All preventive and control measures have to be examined for their efficacy regularly. A good method for this is provided by the PIMEX system as it allows to comprehensively analyse the complete welding process including the extraction system and the PPE. At the same time it allows to improve the process until a minimisation of the exposure is achieved [7] . PIMEX is an acronym from the words PIcture Mix EXposure, and implies that the method is based on mixing pictures, in this case from a video camera, with data on a worker’s exposure to some agent.

Organisational measures to minimise hazards and to separate hazards from workers

See also: Organisational measures of accident prevention.

The number of workers and passers-by that could be exposed to substances generated by welding has to be kept to a minimum. This could be achieved by a related work organisation and / or by indicating or cordoning off of work areas.

However, there has to be sufficient surveillance for lone workers, especially in confined spaces.

Monitoring of exposure

The employers have to ascertain that the relevant Occupational Exposure Limit Values (OELs) are observed. Usually, respirable dust can be used as a representative measurement category. Information on OELs can be found in the GESTIS-database. It may also be necessary to also measure metals in the welding fumes, such as chromium(VI) compounds and nickel and nickel compounds [8] [9]. For example, for Chromium VI compounds an occupational exposure limit value is set in the EU directive 2004/37/EC - carcinogens or mutagens at work (as amended by directive 2017/2398/EU)[10]. The 8 hours limit value is 0,005 mg/m³. Transitional measures until 17.01.2025 are foreseen: limit value 0,010 mg/m3 and limit value: 0,025 mg/m3 for welding or plasma cutting processes or similar work processes that generate fume.

Important indications may also be obtained from biomonitoring.

Health problems generated by welding and health monitoring

The generated substances can have the following effects in humans [3]:

  • The fumes generated by welding have diameters in the range of 8 to 0.01 µm and can enter the deeper parts (alveolae) of the lungs [8].
  • Metal fumes such as iron oxides and aluminium oxide place a strain on the respiratory tract and lungs, meaning that effects in the sense of a chronic inflammation (chronic bronchitis) may occur by an overload of particles [3].
  • Occupational exposure to metal fumes have also been associated with an increased infection risk caused by Streptococcus pneumoniae (pneumonia)[11]. Therefore, in some countries such as Germany[12], the UK[13] and Sweden[11], national regulations or guidelines recommend a vaccination against pneumococcal for welders.
  • Fumes containing fluorides, manganese oxide, copper oxide, have a toxic or toxic-irritating effect [3].
  • Fumes containing chromium(VI) compounds[9] and nickel oxides are carcinogenic, may cause allergies and can occur when stainless steel is being welded [3];
  • Ozone in high concentrations is very toxic, it irritates the respiratory system and the eyes. Leads to tussive irritation, shortness of breath and possibly oedema of the lungs [8].
  • NOx can also cause oedema of the lungs [8] .
  • Carbon monoxide is a very toxic gas that can cause oxygen deficiency in tissues and asphyxiation. It is also a reproductive toxicant [8] .
  • If the welded parts have been coated by paints, plastic, or if they have been electroplated or galvanised, or if they are dirty, a wide variety of additional hazardous substances may be generated that cause additional problems in humans, such as formaldehyde (carcinogen), isocyanates (sensitising) and additional metal oxides (e.g. zinc oxide causing metal fume fever) [8].
  • Siderosis (welder’s lung) is a recognised occupational disease on the list of the European Union [14].

In October 2017, the International Agency for Research on Cancer (IARC) concluded that exposure to mild steel welding fume can cause lung cancer and possibly kidney cancer in humans. As a result of this IARC evaluation, in Britain, the Health and Safety Executive has acted to strengthen its enforcement expectations for fume control at welding activities[15].

Medical surveillance of the workers may be needed, if there is:

  • an exposure to carcinogenic compounds, such as chromium VI, nickel, cadmium,
  • an exposure to fluorine and inorganic fluorine compounds,
  • an exposure to dust concentrations above the OEL,
  • need to wear respiratory protective equipment; a surveillance is needed because of the high strain from wearing PPE, carrying heavy equipment, working in uneasy postures and confined spaces and in high temperatures or outdoors.

Some hazardous substances which pass into the human organism through the inhalation of welding fumes can be determined in biological material (especially urine, full blood or blood serum or in the red blood cells). Thus biomonitoring could be included in the medical examinations [3].

Personal protective measures to minimise hazards

Where the described types of protective measures are not sufficient (e.g. OELs are not complied with), the employer must provide suitable respiratory protective equipment, which must be used by the workers. It is imperative to wear PPE when welding high-alloy steels, such as stainless steel, except when using low-emission procedures such as submerged arc or TIG welding.

The following are examples of respirators that may be used as personal protective measures:

  1. ventilated helmets / hoods with blower and particle filter TH2P or TH3P,
  2. masks with blower and particle filter TM1P, TM2P, TM3P,
  3. full-face masks or mouthpiece fittings with P2 or P3 filters,
  4. half-face / quarter-face masks with P2 or P3 filters, particle-filtering half-face masks FFP2 or FFP3 or
  5. insulation devices.

If gaseous hazardous substances arise during welding, combination filters must be used when wearing filtering respiratory protective equipment [3].

For welding jobs carried out in confined spaces, the following procedure for the selection of respiratory protective equipment can be used:

  1. If possible a feed air and exhaust air system must be installed in the working area.
  2. If this is not possible or not adequate for spatial reasons, preference must be given to the wearing of ventilated hoods or helmets.
  3. If it is not possible to use ventilated hoods and helmets for spatial reasons, FFP2 masks with exhalation valve at least must be worn when welding low-alloy steels, and FFP3 masks with exhalation valve when welding high-alloy steels.
  4. If it is to be expected that nitrous gases will be emitted, e.g. with flame straightening, suitable respiratory protective equipment must be used.
  5. If there is the risk of oxygen deficiency, respiratory protective equipment which is not dependent on the ambient air (insulation devices) must be used [3].

When removing nanomaterial containing paint coatings in preparation of welding jobs by dust producing work procedures, a particle filter P2 (white) or a particle filtering half-mask FFP2 should be worn [16].

Training and information

Only qualified welders should be allowed to carry out welding work. Several European standards provide requirements and quality criteria for the qualifications of welders such as EN ISO 3834, EN ISO 9606 and EN ISO 14732. Welders have to receive proper instructions from their supervisors before starting to weld. All prevention and control measures should be clearly explained and practised sufficiently. The welders should be involved in risk assessment and the selection of appropriate measures at their workplace. The PIMEX system is a good method to motivate the workers to identify shortcomings and take active part in improving the situation. The video recordings of workers performing welding tasks can be used during training sessions.

Measures to improve safe behaviour

The health risks of welding processes are frequently underestimated by employers and workers. Therefore the application of protective measures is not as effective as it could be (see also: Hierarchy of prevention and control measures. Efforts to improve safe working practices need, however, certain preconditions such as example-setting by managers and supervisors, a no-blame culture, a timely feed-back to suggestions, proper induction and regular refresher training. Methods to achieve an improvement include peer observation and the use of the PIMEX system.

Tools for SMEs

In order to select the most appropriate and effective measures, the employer respectively the OSH professionals usually need to look into several (national) directives, rules and guidelines. Some member states provide detailed guidance and legislation for welding. SMEs certainly need some assistance here, and to that end several tools have been developed for example:

  1. In the framework of the Breathe Freely in Manufacturing campaign (UK) the Welding Fume Control Selector Tool has been developed[17]. This web-based tool provides guidance on the most appropriate control measures based on the type of welding, the material being welded, the duration of the welding task and the size of the piece of material being welded.
  2. A Dutch institute developed the "Welding Fume Assistant". This exposure assessment tool has been replaced by an updated instrument called “Verbetercheck Lasrook (Improvement Check Welding Fume)”. As means of illustration it contains PIMEX clips, and good practice descriptions [18].
  3. GisChem, the German information system on hazardous chemical substances includes specific information for work processes such as MAG-welding. The web-based tool provides information for users [19]:
    • Health hazards and OELs
    • Suggestions for less hazardous processes
    • Technical measures (e.g. exhaust systems)
    • Organisational measures
    • Personal protective equipment (e.g. respiratory protective equipment)
    • Hygiene measures.

Outlook

Besides the current pulsed welding machines, which improve the quality of the welds and reduce the amount of fumes, the technological development has brought more “quick and dirty” welding machines on the market as well, such as flux cored wire welding without shield gas. These can be used very easily, because they need very little training and preparations, but may cause high exposures. Therefore it is all the more necessary that SMEs find equally easily accessible health and safety guidelines and assistance. Guidelines so far available in paper or pdf format may not be useful for SMEs and micro enterprises, because finding information for the various specific scenarios is difficult. Web based tools have an advantage as they allow an easy selection of scenarios and can provide the related specific measures: namely which welding processes are possible for the given job, which exhaust system and breathing protection has to be used. More efforts should be put in the development of such tools and the improvement of existing ones.

Ultrafine particles – particles whose diameter is in the nanometre range – have come into the focus of researchers. There is evidence that welding processes generate a considerable amount of these particles, that they can enter the alveoli and can hardly be removed by the body. They may cause considerable health problems such as inflammatory, fibrogenic and carcinogenic effects [20] .

The IARC concluded that exposure to mild steel welding fume can cause lung cancer and possibly kidney cancer in humans. As a consequence, it can be expected that more stringent legislation will come into force, especially with regard to OELs. In order to minimise exposure to welding fumes, it remains necessary to implement prevention and control measures.

References

  1. 1.0 1.1 ILO. ‘Welding and thermal cutting’, Encyclopaedia of Occupational Health and Safety, ILO (Ed.), 2011. Available at: [1]
  2. List of welding processes. Available at: [2]
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Committee on Hazardous Substances (AGS), Technical Rules for Hazardous Substances TRGS 528 – Welding work, Available at: [3]
  4. Scheepers, P.T.J., Geertsen, E., Peer, P., Willems, J., Blootstelling aan lasrook en chroomverbindingen bij laswerkzaamheden in de metalektro en metaalbewerking - Twee onderzoeken (Exposure survey during welding work: welding fume and chromium compounds), UMC/ Radbouw/ Arbo Unie, the Netherlands, 2003. Available at: [4]
  5. HSE - Health and Safety Executive. Controlling airborne contaminants at work. A guide to local exhaust ventilation (LEV), 2017. Available at: [5]
  6. Pocock, D., Saunders, C.J., Effective control of gas shielded arc welding fume, HSE, UK, 2009.
  7. Rosén G. Andersson, I-M., Walsh, P., Clark, R., Säämänen, A., Heinonen, K., Riipinen, H., Pääkkönen, R. ‘A Review of Video Exposure Monitoring as an Occupational Hygiene Tool’, Ann. occup. Hyg., Vol. 49, No. 3, pp. 201–217, 2005, Published by Oxford University Press. Available at: [6].
  8. 8.0 8.1 8.2 8.3 8.4 8.5 BG Information 593 – Hazardous substances in welding and allied processes, 2013. Available at: [7].
  9. 9.0 9.1 EU Commission. Chromium(VI) in fumes from in welding, plasma cutting and similar processes, Third study on collecting most recent information for a certain number of substances with the view to analyse the health, socio-economic and environmental impacts in connection with possible amendments of Directive 2004/37/EC on the protection of workers from the risks related to exposure to carcinogens or mutagens at work, 2018. Available at: [8]
  10. Directive 2004/37/EC of 29 April 2004 on the protection of workers from the risks related to exposure to carcinogens or mutagens at work (sixth individual Directive within the meaning of Article 16(1) Directive 89/391/EEC). Available at: [9]]
  11. 11.0 11.1 Torén K, Blanc PD, Naidoo RN, et al. Occupational exposure to dust and to fumes, work as a welder and invasive pneumococcal disease risk. Occupational and Environmental Medicine. 2020 Feb;77(2):57-63. DOI: 10.1136/oemed-2019-106175. Available at: [10]
  12. BAuA - Bundesanstalt für Arbeitsschutz und Arbeitsmedizin Bekanntmachung von Arbeitsmedizinischen Regeln, AMR 6.7 Pneumokokken-Impfung als Bestandteil der arbeitsmedizinischen Vorsorge bei Tätigkeiten mit Gefahrstoffen durch Schweißen und Trennen von Metallen – Bek. d. BMAS v. 9.5.2019 – IIIb1-36628-15/27. Available at: [11]
  13. HSE - Health and Safety Executive, Pneumonia vaccination for employees exposed to welding and metal fume, 2014. Available at: [12]
  14. Commission Recommendation of 19 September 2003 concerning the European schedule of occupational diseases (Text with EEA relevance) (notified under document number C(2003) 3297), Official Journal, L 238, 25/09/2003 pp. 0028 – 0034. Available at: [13].
  15. HSE - Health and Safety Executive, Change in Enforcement Expectations for Mild Steel Welding Fume, February 2019. Available at: [14]
  16. BG BAU – Berufsgenossenschaft der Bauwirtschaft, Allgemeine Information für Tätigkeiten mit Nanoprodukten Available at: [15].
  17. EU-OSHA, United Kingdom: Free web-based tool for selecting the best measures to protect workers from hazardous welding fumes. Available at: [16]
  18. Koninklijke Metaalunie, Vereniging FME-CWM, FNV Bondgenoten, CNV Vakmensen en de Unie, 5x Beter, Werken is gezond. Available at: [17]
  19. GisChem, Gefahrstoffinformationssystems Chemikalien, Metall - Schweissen, Available at: [18]
  20. DGUV Information 209-020 Beurteilung der Gefährdung durch Schweißrauche. Available at: [19]


Links for further reading

EU-OSHA - European Agency for Safety and Health at Work, Practical tools and guidance on dangerous substances. Available at: [20]

EU-OSHA - European Agency for Safety and Health at Work, Dangerous Substances e-tool. Available at: [21]

Roadmap on carcinogens, good practices and fact sheets. Available at: [22]

EU-OSHA - European Agency for Safety and Health at Work, Infosheet: Carcinogens at Work. Available at: [23]

EU-OSHA - European Agency for Safety and Health at Work, Summary - Exposure to carcinogens and work-related cancer. A review of assessment measures. Available at: [24]

EU-OSHA - European Agency for Safety and Health at Work, Info sheet: Substitution of dangerous substances in the workplace Available at: [25]

EU-OSHA - European Agency for Safety and Health at Work, Info sheet: Legislative framework on dangerous substances in workplaces Available at:[26]

EU-OSHA - European Agency for Safety and Health at Work, Summary - A data-driven method for assessing exposure to dangerous substances in EU workplaces Available at: [27]