Key points
- Welding fumes are composed of metals and most fumes contain a small percentage of manganese.
- Welders, their employers, and healthcare workers have expressed concerns about potential neurological effects associated with exposure to manganese in welding fumes.
Overview
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 damage to the lungs, liver, kidneys and central nervous system.
Health effects
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, may cause Parkinson-like symptoms. Parkinson-like symptoms may include tremors, slowness of movement, muscle rigidity, and poor balance.
Neurological and Neurobehavioral Effects
Numerous studies indicate that 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 that 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. Affected workers frequently show abnormal accumulations of manganese in the region of the brain known as the globus pallidus, which plays an important role in movement regulation.
Welder's Anthrax
NIOSH researchers identified a new occupational disease among metalworkers called welder's anthrax. It is a rare but serious disease caused by the bacteria that produces anthrax toxin. Research suggests that exposure to metal fumes might increase workers' risk for lung infection. This is true even with common, relatively harmless infectious agents. It is still mostly unknown how metal fumes cause this disease. Theories include that metal fumes (or iron) act as a growth nutrient for bacteria, enhance the binding of bacteria to lung tissues, or impair immune responses in the lung through oxidative stress.
Risk of exposure
Exposure to manganese dust occurs primarily in mining, ore-crushing, and metallurgical operations for iron, steel, ferrous and nonferrous alloys. Manufacturing of the following products can also lead to manganese exposure:
- dry-cell batteries
- anti-knock gasoline additives
- pesticides (e.g., maneb)
- pigments, dyes, and inks
- incendiary devices
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. Confined space welding can significantly increase exposure to manganese fumes. For information about assessment of occupational exposure to manganese visit the NIOSH manganese topic page.
Occupational Exposure Limits for Manganese
| Agency | Occupational Exposure Limit |
|---|---|
| NIOSH REL | 1 mg/m3 (TWA) and 3 mg/m3 (STEL) |
| NIOSH IDLH | 500 mg/m3 |
| OSHA PEL | 5 mg/m3 (ceiling) |
| ACGIH TLV | Respirable fraction: 0.02 mg/m3(TWA) Inhalable fraction: 0.1 mg/m3 (TWA) |
IDLH: immediately dangerous to life or health concentration
PEL: permissible exposure limit
REL: recommended exposure limit
STEL: short-term exposure limit
TLV: threshold limit value
TWA: time-weighted average
Resources
NIOSH Resources
NIOSH Publication No. 2005-151: NIOSH Pocket Guide to Chemical Hazards – Welding Fumes
NIOSH Engineering Controls Database: Welding Operations
NIOSH Pocket Guide to Chemical Hazards – Manganese Compounds and Fume (as Mn)
NIOSH: IDLH – Manganese Compounds (as Mn)
NIOSH Science Blog: Welder's Anthrax
NIOSHTIC-2
NIOSHTIC-2 is a searchable bibliographic database of occupational safety and health publications, documents, grant reports, and journal articles supported in whole or in part by NIOSH.
Additional Resources
OSHA Occupational Chemical Database – Manganese Compounds (as Mn)
OSHA: Safety & Health Topics – Toxic Metals – Manganese
Agency for Toxic Substances and Disease Registry (ATSDR): Toxicological Profile for Manganese
WHO: Concise International Chemical Assessment Document 12- Manganese and Compounds