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

Mutagenicity
The genotoxicity of fume particulate from the welding of stainless steel has been
investigated in a number of in vitro assays. The particulate fraction of MMA/SS
fume, and to a lesser extent that of MIG/SS fume, has generated positive results in
assays for the following end-points: reverse mutation in bacterial cells; induction of
SCEs, cell transformation, chromosome aberrations in mammalian cells. Equivocal
results have been obtained in mammalian cell mutagenicity assays. These results give
an indication that certain constituents of the particulate fraction of welding fume from
stainless steel, most likely water-soluble constituents, may possess mutagenic activity.
Limited in vivo data provide some indication that water-soluble components of
MMA/SS fume particulate are mutagenic to somatic cells in vivo.
Investigations of genetic damage in lymphocytes from stainless steel welders have
generated generally inconclusive results.
Consideration against classification criteria: According to the Annex VI criteria, the
available data relating to mutagenicity do not provide a basis for considering fume
from welding stainless steel as mutagenic.
Carcinogenicity
No carcinogenicity bioassays have been conducted with fume from the welding of
stainless steel involving exposure by inhalation. The available animal carcinogenicity
data are limited to an i.t. instillation study and an intrabronchial implantation study,
neither of these conforming to currently accepted protocols. The former study was
poorly conducted and contributes no reliable data. The latter study, although deficient
in several respects, provides no evidence that the MMA/SS welding fume tested is
carcinogenic in animals.
A number of investigations into cancer risks in workers engaged in the welding of
stainless steel have been performed. The lung cancer findings from many of these
studies are based on small numbers and interpretation is also hindered by the absence
of reliable exposure histories. Nevertheless, these studies provide no consistent
pattern of excess lung cancer risk attributable to the welding of stainless steel. In
addition, a meta-analysis of lung cancer in welders (Moulin 1997) concluded that the
elevated lung cancer rates in welders “cannot be explained by hexavalent chromium
and nickel exposures among stainless steel welders”.
Consideration against classification criteria: When data concerning the hazards
associated with welding are evaluated against the current EU classification criteria,
it is clear that welding, per se, may be associated with an increased risk of lung
cancer. This position is reflected in the IARC placing of “welding fumes” in Group
2B: “possibly carcinogenic to humans” (IARC, 1990). However, as the welding of
stainless steel gives rise to no further increase in the risk, the increased risk
associated with the welding process appears not to be specific to the metals being
welded.
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