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Information on the toxicokinetics of fume from the welding of stainless steel in
humans comes from studies which have measured chromium levels in the blood or
urine in mostly MMA/SS welders. The elevated urinary chromium levels reported,
and in one study elevated RBC levels, provide evidence of chromium absorption as a
result of exposure to welding fume. In some studies, the results indicated that
repeated exposure may lead to accumulation of chromium.
3.1.4 Toxicity
Acute toxicity
Animal data
The effect of inhaled MIG/SS welding fume was studied in male rats following a
single period of exposure (Hicks et al. 1983, 1984). The welding fume was generated
using a mild steel workpiece and stainless steel electrode wire (Borstrand 61). Details
of the chemical composition of the fume have previously been reported (see Section
3.1.3). Twenty-four rats were exposed to fume (mean particle concentration 400
mg/m 3 ) for 184 minutes; groups of six animals were killed and examined at 3, 24 and
48 hours and 7 days after exposure. In another treatment group, 30 rats were exposed
to fume (mean particle concentration 580 mg/m 3 ) for 173 minutes; groups of six
animals were examined at 12, 21, 28, 200 and 300 days after exposure. Unexposed
animals served as controls. Results from the two exposure groups were combined.
Early effects in the lungs consisted of inflammatory changes (pneumonitis and
bronchiolitis) which occurred 2-48 hours after exposure, followed by accumulation of
particle-laden macrophages throughout the lung and alveolar epithelial thickening (7-
21 days). Particle clearance from the alveoli was incomplete 28 days after exposure;
particle-laden cells were visible as peribronchial and subpleural aggregates, and
distributed throughout the lung. Foam cells, giant cells and marked epithelial
thickening were also evident. These changes persisted 200-300 days after exposure.
No collagen formation was observed at any time after exposure. This study showed
that exposure by inhalation to MIG/SS welding fume at a particle concentration of
400 or 580 mg/m 3 for approximately three hours induced inflammatory changes in the
lungs of rats.
Inhalation toxicity of MMA/SS welding fume was investigated in rats following
single exposure (Uemitsu et al. 1984). Welding fume was generated under laboratory
conditions using SUS 304 stainless steel plate and a Lime-titania electrode. Eight
male rats were exposed to welding fume by the nose-only for one hour. In the control
group, eight animals were exposed to air only. The particulate content of the fume,
which was monitored periodically during the exposure period, was 1088 13 ± 125
mg/m 3 . Particle size distribution data were as follows: median diameter 0.56 µm;
mass mean diameter 0.80 µm; aerodynamic diameter 1.51 µm. Chemical composition
of the fume included the following oxides: 7.59% Cr (3.46% as soluble); 1.27% Ni
(trace amounts as soluble). Animals were examined two, seven and fourteen days
after exposure. During the 14-day post-treatment period, no deaths occurred in the
13 The actual fume concentration was also reported to be 1008 ± 106 mg/ m 3
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