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Hazardous substances in welding and allied processes are the inhalable/respirable substances generated, which are absorbed by the human body (Fig. 1.1). At a certain concentration, these substances may cause a risk to health.

To determine the health and safety program required to protect welder workers, an evaluation of workplace hazards which complies with national, regional or international health and safety regulations (e.g. labour protection law), shall be completed.

Any predominant hazardous substance is called a key component (for a specific combination of process and material). A main component of the welding fume is a component of occupational medical importance, the percentage of which in the welding fume is not predominant, i.e., this component is no key component of the welding fume. Main components shall not be equated with key components.

Despite considerable technical and organisational efforts, full protection from the effects of hazardous substances cannot be attained under today’s operating conditions. Therefore, it is necessary and beyond dispute that, for some operations, necessary technical prevention should be accompanied by preventive occupational medical care. The purpose is avoidance and early detection especially of chronic diseases.

In order to minimise the health hazard to the welder by hazardous substances at the workplace, technical, organisational and—in certain situations—also personal protective measures shall be implemented according to the applicable regulations. The efficiency of the implemented protective measures shall be checked by verification of their efficiency.

The effects can be considered on the basis of the structure of welding fumes (see also Sect. 2.2), as they are gaseous or in the form of particulate matters.

Epidemiological studies and animal tests with ultrafine particles non specifically connected with welding are in principle inhalation tests with rats or other rodents exposed to diesel soot, to technical soot and other particles to evaluate the effect of the size of particles independent of the chemical composition. They show that, depending on the particle surface in contact with the lung, inflammatory, fibrotic (hardening of the lung tissue) or carcinogenic effects may occur.

To minimise the health hazard to the welder posed by hazardous substances encountered in the workplace, engineering, administrative organisational and—in certain situations—personal protective measures, shall be implemented. The effectiveness of the implemented protective measures shall be verified.

Based on several studies, the Scientific Committee on Occupational Exposure Limit Values (SCOEL), under the EU Commission, recommended a significant reduction in the occupational exposure levels for oxides of nitrogen. This best practice document aims to describe the situation regarding the generation of oxides of nitrogen during different welding and cutting procedures and also outlines the potential health hazards that might arise as a result of exposure. Finally, protective measures for welding and cutting in workshop and on site are reported.

Based on several studies, the Scientific Committee on Occupational Exposure Limit Values (SCOEL) under the EU Commission recommended a significant reduction in the Occupational Exposure Levels for Nitrogen Oxides. In the document all the relevant aspects are considered, such as the process for the generation of the Nitrogen Oxides during welding and cutting, the corresponding health hazards and occupational diseases. The results of the applicable studies are reported and, based on that, some conclusive remarks are drawn. A specific section is also devoted to applicable protective measures for welding and cutting in the workshop and on-site.

It has been shown that exposure of subjects to emissions from a metal inert gas (MIG) brazing process of zinc-coated material led to an increase of high-sensitivity C-reactive protein (hsCRP) in the blood. In this study, the no-observed-effect level (NOEL) for such emissions was assessed.Twelve healthy subjects were exposed for 6 hours to different concentrations of MIG brazing fumes under controlled conditions. High-sensitivity C-reactive protein was measured in the blood.For welding fumes containing 1.20 and 1.50 mg m zinc, high-sensitivity C-reactive protein was increased the day after exposure. For 0.90 mg m zinc, no increase was detected.These data indicate that the no-observed-effect level for emissions from a MIG brazing process of zinc-coated material in respect to systemic inflammation is found for welding fumes with zinc concentrations between 0.90 and 1.20 mg m.