Workplace Exposure to Submicron Particle Mass and Number Concentrations From Manual Arc Welding of Carbon Steel

Abstract

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 microm 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 x 10(5)/cm(3) 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/m(3). 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 microm 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.

Exposure to Manufactured Nanostructured Particles in an Industrial Pilot Plant

“…Concentrations measured in workplaces, households and urban environments can be similar or much higher Exposure to manufactured nanostructured particles in an industrial pilot plantthan the steady-state concentrations obtained at this site (Zhu et al, 2002;Stephenson et al, 2003;Maynard et al, 2004). However, as the concentrations are derived under different conditions, the outlined comparison can only provide an indication for the corresponding order of magnitude.…”

Design and Characterization of an Inhalation System of Iron and Manganese Oxide Nanoparticles for Rodent Exposure

“…Welders' personal exposures to manganese has been measured at concentrations up to 4.93 mg/m 3 and up to 16.29 mg/m 3 for iron (Korczynski 2000;Flynn and Susi 2009), with total welding particulate levels up to 30 mg/m 3 (Susi et al 2000;Meeker et al 2007;Zeidler-Erdely et al 2012). Given that NP can represent up to 80% in number and 16% in mass of the total particles emitted during welding (Stephenson et al 2003;Dasch and D'Arcy 2008), the aerosol generated in our study is therefore representative of welder's occupational environment. This is important to consider as our experimental set-up is dedicated to expose the animals repeatedly, over long periods of time, in order to mimic a worker's lifetime occupational exposure.…”

“…These latter NP can be produced either intentionally because of the novel properties-useful for various applications-they display (engineered NP) or generated unintentionally (during domestic activities such as cooking, smoking, incense burning, or in welding fumes) (Stephenson et al 2003;Marconi et al 2006;Ji et al 2010). Because of the rise of anthropogenic sources of NP (and particularly the engineered ones) human exposure to NP has dramatically increased in the recent years, in the general population as well as in the context of occupational exposure (Seaton et al 2010).…”

Field Application of a Newly Developed Personal Nanoparticle Sampler to Selected Metalworking Operations

“…Also, Elihn and Berg (2009) showed the ambient average PM 1 was 280 μg/m 3 during steel spot welding, in which there was good general ventilation but with other welding activities nearby. The PM 4 of 460 μg/m 3 in the breathing zone of a shielded metal arc welder has been reported by Stephenson et al (2003). More recently, a study of 215 welders showed the personally exposed median PM 4 was 1290 μg/m 3 during gas metal arc welding with solid wire, flux-cored wire, tungsten inert gas welding, and shielded metal arc welding (Lehnert et al, 2012).…”