Validation and progress of a model for estimation of exposure to welding fumes

Status:

completed 01/2013

Aims:

Concentrations of welding fumes in workplace atmospheres, and consequently welders' exposure to them, are generally determined by measurement. The Institute for Prevention and Occupational Medicine (IPA) has developed a model for computational estimation of welding-fume exposure that is based upon the results of the WELDOX Study (Project IPA 50: exposure to metals during welding and their health effects: an interdisciplinary study for the formulation of health-based limit values for carcinogenic metals (WELDOX)). In the course of this study, measurements of welding fumes were performed at workplaces in the shipbuilding, machine and plant construction, and toolmaking sectors. The measurement data showed clearly that welders' exposure is essentially determined by the emission rate of the process, the constituent substances of the fumes, the welding electrode type (solid or flux-cored wire), the spatial arrangements at the workplace and the effectiveness of local exhaust ventilation system (welding fume separation equipment). Statistical methods were used to derive mathematical variables (intercepts and exp(β) values) for these parameters that reflect their influence upon the exposure. Modelling was performed by combination of these variables. Thus the model is valid for the welding methods and working conditions considered in the study. Welding is however performed in many other sectors of trade and industry. This raises the following questions: is the model also applicable to other sectors? Must the model be corrected for other purposes? Have further influencing variables be considered in order for the accuracy of the model to be enhanced? The purpose of the present research project is to find answers to these questions and thereby to validate the exposure model and to enhance it.

Activities/Methods:

In order to answer the above mentioned questions, a working group was formed under the overall control of the Institute for Occupational Safety and Health (IFA) with the involvement of representatives from the Institute for Prevention and Occupational Medicine (IPA), the German Social Accident Insurance Institutions for the woodworking and metalworking industries (BGHM) and the energy, textile, electrical and media products sectors (BG ETEM), and the IFA itself. It was agreed that a new statistical analysis of welding fume data would be used to validate the exposure model. The exposure data available in the IFA's MEGA exposure database for the period from 2000 to 2011 were selected as the body of data to be used for this purpose. These data were obtained by the German Social Accident Insurance Institutions at welders' workplaces in a number of sectors, and reflect to diverse working conditions. The intercepts and exp(β) values were determined for these data. In order to validate the model, the intercepts and exp(β) values of the WELDOX study were compared with those from MEGA. The working group also agreed that practical trials would be performed and the model developed further.

Results:

Validation of the exposure model showed that in principle the model is suitable for computational estimation of exposure to welding fumes. It must be considered that the WELDOX study primarily examined working conditions in shipbuilding, machine and plant construction and toolmaking. The working conditions typically found in these sectors can be extrapolated only partly, if at all, to other sectors. For estimations of exposure outside these sectors, the exp(β) values of the WELDOX study should not be used for calculation, particularly in case of flux-cored wire welding and welding in confined spaces. The exp(β) values derived from the MEGA data can be assumed in many welding application in order to reflect the exposure to welding fumes actually occurring at the workplace with a higher degree of accuracy. This shows that the exposure model should attach greater importance to the influence of the sector.

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