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What is being done about manganese exposure causing manganism?
Researchers are still investigating the link between welding rod
fumes and manganism. Welding rod litigation has now begun to help
those who suffer the ill health effects of welding and manganese
exposure.
Efforts are being made to reduce the risk of environmental manganese
exposure. In 1994, the U.S. Environmental Protection Agency (EPA)
denied a petition by Ethyl Corporation to allow the use of methylcyclopentadienyl
manganese tricarbonyl (MMT) in unleaded gasoline, because of health
concerns related to the inhalation of manganese fumes (Davis,
1999).
Other environmental laws have been enacted to limit manganese
exposure and welding fume toxicity. However, some scientists feel
that more needs to be done about manganism and welding fumes.
Researchers studying the health effects of welding fumes report
a "preponderance of proof for manganese neurotoxicity" even in
present-day industrial settings (Iregren 1999).
According to the U.S. Department of Labor Mine Safety and Health
Administration, Welding Fumes Sampling is required due to the
"potential hazards of welding operations including metal fumes,
toxic gases, and ultraviolet and infrared radiation. Fume particles
are formed from vaporization of molten metal. They are very fine
in size, generally one micron or smaller, and may join together
to form larger particles. Welding fumes can be sampled by drawing
air through a special filter at a controlled rate.
“The adverse health effects of welding exposure include chronic
or acute systemic poisoning, metal fume fever (a short-term painful
ailment with symptoms of fever and chills), pneumoconiosis (lung
disease due to accumulation of mineral or metallic particles),
and irritation of the respiratory tract.
"The welding fumes produced at welding operations depend primarily
on the composition of the metals being welded and the welding
rods. When the base metal is iron or steel, with welding rods
of similar composition, the main component of the welding fume
will be iron oxide. When welding on stainless steel, welding fumes
containing nickel and chromium may be produced. Welding on plated,
galvanized or painted metals may generate fumes containing cadmium,
zinc oxide or lead. In addition, welding rods can generate fluoride
and free silica in the fumes, depending on the composition of
the welding rod coating.
“In summary, welding processes may generate many different metal
fumes and other toxic components. It is important that the hazards
of a welding operation be evaluated properly. Toxic gases that
arise in welding include carbon monoxide, nitrogen dioxides and
ozone. If welding or cutting operations are conducted in the presence
of chlorinated hydrocarbons, such as the form of solvents either
on the metals or in the air, hazardous concentrations of phosgene
and hydrogen chloride, which are highly toxic irritant gases,
may be produced.
"In addition to the health hazards of metal welding fumes and
toxic gases, welding operations involve the hazard of burns from
flame, arc, molten metal, heated surfaces and also that of metal
splatter. ...When personal respiratory protection is required,
this may be provided by a supplied-air welding hood or, when the
components and concentration of the fume are known, by a filter-type
respirator with filter for protection against welding fumes. It
is preferable, of course, that adequate ventilation be provided
so as to make the use of respirators unnecessary.
"When sampling for welding fumes, the inspector will use a filter
cassette placed on the collar or shoulder so that it is beneath
the helmet when the helmet is placed down. The sampling pump is
fastened to the belt. Samples [for welding fumes] may be full
shift or short-term. Short-term samples may be taken to evaluate
toxic [welding fume] components which have short-term limits.
In addition, the inspector may sample for toxic gases such as
ozone, nitrogen oxides or phosgene. It is important that the welder
carry out the welding operation in a normal way, so that an accurate
evaluation of the exposure can be made. The inspector will attach
and remove the filter cassette and pump as required.
"Normally, good local or general ventilation is required to control
exposures to the metal welding fumes and gases of welding operations.
The most effective control is local exhaust ventilation in which
an exhaust hood is placed near the welding arc or flame, and the
‘welding fume contaminants’ are drawn away from the welder's breathing
zone. The system may consist of moveable exhaust hoods, flexible
and stationary ducts, a powered fan, and a welding fume or dust
collector. Exhausted air containing welding fumes should be discharged
to the outdoors, if possible. It is important that, during the
welding operation, the exhaust hoods are placed or set so that
welding fumes are not drawn across the worker's face or into the
breathing zone. Good general ventilation should be provided. Welding
in confined spaces, such as tanks, cabs of mobile equipment and
large shovels, may be especially hazardous and require additional
ventilation to reduce welding fumes.”
http://www.msha.gov Citation
as of 11-15-2004.
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