To answer in true engineering fashion, “It depends.” Do you ever see your welders in a little bit of a plume or working directly over or downwind of the weld? Get the picture? How can the welders be exposed? Manganese is in all steel and is often added to improve strength and hardness. So the welder can be exposed, even if there is no manganese in the welding rod.
One man’s medicine is another’s poison
Manganese is an essential nutrient. A healthy person with normal liver and kidney function can excrete excess dietary manganese. Inhaled manganese is of greater concern because it bypasses the body’s normal defense mechanisms. This can lead to manganese accumulation and adverse health effects including damage to the lungs, liver, kidney and central nervous system. Male workers exposed to manganese also have a higher risk of fertility problems. Prolonged exposure to high manganese concentrations (>1 mg/m3) in air may lead to a Parkinsonian syndrome known as “manganism.” Chronic exposure to the manganese-containing pesticide maneb is also reported to cause Parkinson-like symptoms. According to the National Institute of Occupational Safety and Health (NIOSH), Parkinson-like symptoms may include tremors, slowness of movement, muscle rigidity and poor balance.
Exposure to manganese occurs primarily in mining, ore-crushing and metallurgical operations for iron, steel, ferrous and nonferrous alloys. Manganese fumes are produced during metallurgical operations and several types of welding operations. The exposure can vary considerably depending on the amount of manganese in the welding wire, rods, flux and base metal, according to NIOSH.
Numerous studies indicate welders may be at increased risk of neurological and neurobehavioral health effects when exposed to metals such as lead, iron and manganese. Carbon monoxide, heat and stress can also contribute to neurological impairments in welders. Some studies indicate welders exposed to low levels of manganese (<0.2 mg/m3) perform more poorly on tests of brain function and motor skills. These effects include changes in mood and short-term memory, altered reaction time and reduced hand-eye coordination. According to NIOSH, it is not known if these findings have clinical significance.
Why are we talking about manganese exposure now?
OSHA set the Permissible Exposure Limit (PEL) at 5 milligrams per cubic meter (mg/m3) over 20 years ago. The American Conference of Governmental Industrial Hygienists (ACGIH) recently lowered its Threshold Limit Value (TLV) for respirable/inhalable manganese to 0.02 mg/m3 and 0.1 mg/m3 — significantly lower than OSHA’s PEL.
ACGIH is a nonprofit, nongovernmental corporation dedicated to promoting worker health and reducing exposures to environmental health stressors in the workplace. It is not OSHA and doesn’t set legal or regulatory exposure limits, but some governmental agencies and businesses use the TLVs as their standards. And therein lies the rub.
How much credence do you give to the TLVs? Go with the TLVs and risk someone asking why you’re using TLVs that maybe aren’t enforceable, or only worry about OSHA’s PEL for manganese and have someone ask why you didn’t take the conservative approach? You can count on the Law of Unintended Consequences coming into play at some point.
What can you do to reduce manganese exposures?
You have three basic options: eliminate the manganese, control the hazard or provide PPE.
With respect to eliminating the hazard, forget it. Even if you use welding rods without manganese, we aren’t going to eliminate manganese from steel. So the manganese is here to stay.
You can often control manganese exposures but not always. The work is what it is. We recommend a combination of engineering controls with PPE (include training along with both the engineering controls and PPE selection).
We base our recommendations on the welder exposure monitoring we’ve completed over the years. We’ve found even with well planned and properly implemented engineering controls, the actual work circumstances will invariably lead to a situation where engineering controls alone don’t work. In those cases, respiratory protection is required. And make sure you’ve selected the right respirator/filter combination.
For more information, call Chris White, P.E. at (225) 761-9141, Ext. 2 or email cwhite@wynnwhite.com.
