manufacture, processing and use of stainless steel - International ...

3.1.2 Information on exposure
Welding of stainless steel results in the formation of fume containing particles and
gases. As the particulate is mostly respirable, welding operations present the potential
for inhalation exposure in the occupational setting.
Published exposure data for the welding of stainless steel come from field studies and
laboratory-based studies. The data from these studies are summarised in Table 3.1.
Information on the elemental composition of MMA/SS and MIG/SS welding fume is
presented in Table 3.2.
Only a few studies are available which have investigated workplace exposure to
stainless steel welding fumes using well-designed sampling strategies. In a number of
studies, the use and effectiveness of controls have not been assessed and relatively
small sample sizes have been used. Overall, the published data on exposure indicate
that daily personal TWA concentrations for total fume are in the range 0.1-40 mg/m 3
(range of mean values 1.3-3.1 mg/m 3 ). In confined spaces, mean personal exposure
levels up to 37.2 mg/m 3 have been reported. Comparison of total fume concentrations
for the different welding methods shows that the highest levels occur with MMA
welding compared to MIG or TIG welding. Fume concentrations measured in static
samples constitute about one tenth of those found in personal samples.
Laboratory-based studies on welding of stainless steel have provided useful data on
the composition of fume associated with the different welding methods, the effect of
welding parameters on fume composition, and the physical and chemical properties of
welding fume. The available data show that MIG/SS welding produces higher total
chromium concentrations than MMA/SS welding, although only a negligible
proportion of this occurs as Cr VI (see Table 3.1). In contrast, MMA/SS welding
generates a higher concentration of Cr VI in the fume compared to MIG and TIG
welding; this is due to the presence of alkaline metals in the flux coating. Cr VI in
MMA/SS welding fume occurs as sodium or potassium dichromate. The percentage
of total chromium which exists as Cr VI in MMA/SS welding fume has been reported
to range from 30 to 100% (see Table 3.1), and Cr VI concentrations of up to 1.5 mg/m 3
have been reported with MMA/SS welding operations (van der Wal 1985). The
nickel content of fume from welding of stainless steel has been reported to be between
0.2 and 4.9% of the total fume. Nickel in welding fume occurs as oxides,
predominantly in the insoluble form.
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