|Abstract or Summary
- Electric arc welding is the most prevalent welding type in industry. It creates two
main groups of health hazards for workers; fumes and gases, and radiant energy.
Shielded Metal Arc (SMA) welding is the most widely used welding method in industrial
plant welding shops. The main chemical health hazards associated with this type of
welding are fumes. Fumes are particles formed when the electrode and base metal
constituents are vaporized and condensed in the welding area.
Potential health problems can be anticipated by measuring the concentration of
fumes in the welding space and comparing these data to established exposure standards.
If high concentrations of these fumes are present, control measures should be undertaken
to reduce the potential toxic effect to workers.
Most of the studies have been done on mild (carbon) steel welding where it is
generally necessary to monitor only the total amount of fumes. Stainless steel welding
differs from carbon steel welding in that it generates considerable fume concentrations
of chromium and nickel, which are suspected human carcinogens.
The first part of this study evaluated the health risks posed to workers exposed
to chromium and nickel fumes from routine stainless steel welding procedures. All the
welding was performed in an industrial plant welding shop by one experienced welder.
The welded piece was a three-part stainless steel cylinder. The whole period of welding
lasted almost three weeks, although the actual welding was done in eleven days during
that period. All sampling was performed with filter cassettes connected to personal air
pumps. Sampling was performed in welder's breathing zone, in the general area
(background sample), and at conveniently located points outside the breathing zone for
evaluation of ratios of chromium and nickel to total fumes. The results indicated that at
this particular industrial plant, exposure levels did not exceed the Occupational Safety
and Health Administration (OSHA) Permissible Exposure Limits (PELs) and the
American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit
Values (TLVs). The results also indicated that it was not necessary to monitor the
general area because of very low concentrations of chromium and nickel fumes. Rather,
it is suggested that the monitoring focuses on the welder's breathing zone where it is
important to sample hexavalent chromium (chromates) because of its proven carcinogenic
effect and therefore very low TLV. Also, it was found that if TLV for chromates is not
exceeded, then levels of total chromium and nickel are also likely to be below limits.
The second part of the study sought to devise a simplified method of monitoring
of welding operations. The results suggested that it is not always necessary to sample
for all the components (total fumes, total chromium, chromates, and nickel) when
estimating worker's exposure. Rather, it is possible to simplify the process by
establishing the ratios of fume constituents during a period of heavy welding, thus
enabling the industrial hygienist to make a reasonable estimate of exposure that occurs at
other times. The estimate can be made by sampling either the main constituent
(chromates) or total fumes, and predicting the exposure to remaining constituents of
interest from these data. In addition, and in contrast to previous studies, it has been concluded that when
fume concentrations are low, a welder's helmet does not provide any additional
protection against fumes. Additional protection can be provided with the use of proper
local ventilation, such as with a flexible hose, to reduce exposure well below suggested