Physical and Chemical Characterization of Airborne Particles from Welding Operations in Automotive Plants

Abstract

Airborne particles were characterized from six welding operations in three automotive plants, including resistance spot welding, metal inert gas (MIG) welding and tungsten inert gas (TIG) welding of aluminum and resistance spot welding, MIG welding and weld-through sealer of galvanized steel. Particle levels were measured throughout the process area to select a sampling location, followed by intensive particle sampling over one working shift. Temporal trends were measured, and particles were collected on filters to characterize their size and chemistry. In all cases, the particles fell into a bimodal size distribution with very large particles >20 μm in diameter, possibly emitted as spatter or metal expulsions, and very small particles about 1 μm in diameter, possibly formed from condensation of vaporized metal. The mass median aerodynamic diameter was about 1 μm, with only about 7% of the particle mass present as ultrafine particles <100 nm. About half the mass of aluminum welding particles could be accounted for by chemical analysis, with the remainder possibly present as oxygen. Predominant species were organic carbon, elemental carbon, iron, and aluminum. More than 80% of the particle mass could be accounted for from steel welding, primarily present as iron, organic carbon, zinc, and copper. Particle concentrations and elemental concentrations were compared with allowable concentrations as recommended by the Occupational Safety and Health Administration and the American Conference of Governmental Industrial Hygienists. In all cases, workplace levels were at least 11 times lower than recommended levels.

Keywords:

• airborne particles
• fumes
• metals
• welding

ACKNOWLEDGMENTS

The authors would like to thank the following General Motors personnel: Sid Kinare, Aaron Gundrum, and Don Chester for help with the sampling; Carolina Ang for organic analysis; Curt Wong for SEM analysis; and Shawn Gayden, Dave Sigler, Jim Griffin, Jerry Brown, and Joe Speranza for their helpful input. The authors would also like to thank the following GM plant personnel who greatly facilitated our sampling: Ray Carney, Karen Averill, Tony Rubio, Deena Robertson, Carrie Ziehl Brown, Mike Bond, Nancy Milner; Ernie Johnston, Jesse Simpson, Dale Gossiaux, Bill King, Tony Prevost, and Rhonda McCarty.

Notes

^APercentage based on total mass on MOUDI.

^AShaded areas indicate that that element was distinctively higher in areas of aluminum welding than steel welding, or vice versa.

^ACarbon black.

^BAluminum dust.

^CAluminum metal dust, respirable fraction.

^DCalcium oxide.

^EChromium metal or chromium (III).

^FChromium (VI).

^GManganese fume.

^HIron oxide dust or fume.

^IInsoluble nickel compounds.

^JCopper fume.

^KRespirable zinc oxide.

^LZinc oxide fume.