Welding generates high concentrations of ultrafine particles, which research suggests may be more toxic than larger particles. Fume characteristics were measured in a controlled apparatus as a function of voltage level and wire feed speed. Particles were sampled close to the welding process on mixed cellulose ester membrane filters and analyzed for iron, manganese, and total particulate matter at an accredited industrial hygiene laboratory. An ultrafine condensation particle counter measured the particle number concentration, and an optical particle counter measured the particle size distribution. Submicrometer particle number concentrations and iron, manganese, and total particle mass concentrations all depended on voltage levels but not on wire feed speed at a constant voltage. Ultrafine particle concentrations were more than three times greater at 23.5 V than at 16 V. Particles 0.5-0.7 μm in diameter counted by the optical particle counter increased from 9800 particles/cm3 at 16 V to 82,800 particles/cm3 at 23.5 V. Manganese concentration was 1.7 mg/m3 at 16 V vs. 6.4 mg/m3at 23.5 V. The data suggest that welders should use lower voltage levels whenever possible.
Bibliographical noteFunding Information:
T his research was made possible through funding from the Pilot Projects Research Training Program of the Midwest Center for Occupational Safety and Health at the University of Minnesota’s School of Public Health. The authors would like to thank Jon Kilgore of the University of Minnesota Physics Machine Shop for his assistance in assembling the experimental apparatus.
- Wire feed speed