Workplace Exposure to Submicron Particle Mass and Number Concentrations From Manual Arc Welding of Carbon Steel
Particle emissions from manual shielded metal arc welding of carbon steel were sampled in a typical industrial maintenance and metal fabrication workplace environment. Particle number measurements over the size range from 14 nm to 10 µm using a scanning mobility particle sizer and an optical particle counter showed that welding produced an approximately lognormal particle mode with a 120 nm count median and a geometric standard deviation of 2.07. This study produced welding particle number concentrations on the order of 2×105/cm3 in the building air 8.5 m away from the welding. Workplace exposure samples were below the current 8-hour American Conference of Governmental Industrial Hygienists mass concentration threshold limit value of 5 mg/m3. Submicron particles comprised 80% of the total aerosol mass collected by a cascade impactor during welding. The concentration of larger particles was indistinguishable from indoor background. Microscopy showed that the welding emissions are dominated by clusters formed from <0.1 µm primary spheres. These data on the particles resulting from aerosol transformation by natural dilution inside an industrial building can be compared with laboratory-scale studies of welding particulate. The particle number characteristics observed in this study are significant because toxicological hypotheses suggest that number or surface area may be a better metric than mass when evaluating the health effects of fine particles.
Stephenson, Dale; Seshadri, Gauri; and Veranth, John M.. (2003). "Workplace Exposure to Submicron Particle Mass and Number Concentrations From Manual Arc Welding of Carbon Steel". American Industrial Hygiene Association Journal, 64(4), 516-521. http://dx.doi.org/10.1080/15428110308984848