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Hexavalent chromium content in stainless steel welding fumes is dependent on the welding process and shield gas type.

Authors
Keane-M; Stone-S; Chen-B; Slaven-J; Schwegler-Berry-D; Antonini-J
Source
J Environ Monit 2009 Feb; 11(2):418-424
NIOSHTIC No.
20034985
Abstract
Occupational exposure to welding fumes is a known health hazard. To isolate elements in stainless steel welding fumes with high potential for adverse health outcomes, fumes were generated using a robotic gas metal arc system, using four shield gases of varying oxygen content. The objective was to measure CrVI concentrations in a broad spectrum of gas metal arc welding processes, and identify processes of exceptionally high or low CrVI content. The gases used were 95% Ar/5% O2, 98% Ar/2% O2, 95% Ar/5%CO2, and 75% He/25% Ar. The welder was operated in axial spray mode (Ar/O2, Ar/CO2), short-circuit (SC) mode (Ar/CO2 low voltage and He/Ar), and pulsed axial-spray mode (98% Ar/2% O2). Results indicate large differences in CrVI in the fumes, with Ar/O2 (Pulsed) > Ar/O2 > Ar/CO2 > Ar/CO2 (SC) > He/Ar; values were 3000 300, 2800 85, 2600 120, 1400 190, and 320 290 ppm respectively (means standard errors for 2 runs and 3 replicates per run). Respective rates of CrVI generation were 1.5, 3.2, 4.4, 1.3, and 0.46 g/min; generation rates were also calculated in terms of g CrVI per metre of wire used. The generation rates of CrVI increased with increasing O3 concentrations. Particle size measurements indicated similar distributions, but somewhat higher >0.6 m fractions for the short-circuit mode samples. Fumes were also sampled into 2 selected size ranges, a microspatter fraction (0.6 m) and a fine (<0.6 m) fraction; analysis indicated that CrVI is primarily associated with particles <0.6 m. The conclusion of the study is that CrVI concentrations vary significantly with welding type and shield gas type, and this presents an opportunity to tailor welding practices to lessen CrVI exposures in workplaces by selecting low CrVI-generating processes. Short-circuit processes generated less CrVI than axial-spray methods, and inert gas shielding gave lower CrVI content than shielding with active gases. A short circuit He/Ar shielded process and a pulsed axial spray Ar/O2 process were both identified as having substantially lower CrVI generation rates per unit of wire used relative to the other processes studied.
Keywords
Welding; Welding-industry; Fumes; Gas-welders; Chromium-compounds; Particulates
Contact
Michael Keane, National Institute for Occupational Safety and Health, Health Effects Laboratory Division, 1095 Willowdale Rd, Morgantown, WV 26505, USA
CODEN
JEMOFW
CAS No.
18540-29-9; 10028-15-6
Publication Date
20090201
Document Type
Journal Article
Email Address
mjk3@cdc.gov
Fiscal Year
2009
NTIS Accession No.
NTIS Price
Issue of Publication
2
ISSN
1464-0325
NIOSH Division
HELD
Priority Area
Manufacturing
Source Name
Journal of Environmental Monitoring
State
WV
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