Manganese, while being a crucial mineral for the human body, can also be toxic. The body naturally excrete dietary manganese excess through the liver and kidneys. However, inhaled manganese from welding fumes bypasses this protective mechanism, leading to an accumulation that may provoke various health issues.
Manganese is a hard, gray metal used to produce steel. It’s found in welding fumes and can be inhaled by welders during operations. In this article, we explore how welders become exposed to manganese, the permissible levels of exposure, and preventative measures against the health risks posed by manganese fumes.
How Do Welders Become Exposed to Manganese?
The majority of welders are exposed to manganese (Mn) in their work. Mn fumes become a significant concern when dealing with high-tensile and low-alloy steels, ferrous alloys, and certain alloys of copper, aluminum, and nickel. These materials often contain less than 2% of Mn, though some can have up to 16%. The quantity of Mn in the welding wire, rods, and flux also factors in.
Understanding the composition of metals, gases, and consumables used during the process is vital, as it informs welders of their potential exposure. This understanding becomes crucial while welding in confined spaces since it can significantly increase exposure to manganese fumes and other hazardous substances.
Welding fumes, composed of a blend of different metals and gases, generally include a small percentage of manganese. This may exist in several oxidation states, such as manganese dioxide, manganese tetroxide, or manganese trioxide, and with different solubility properties. Manganese particles in welding fumes typically range between 0.001 and 100 µm, and may deposit throughout the respiratory system.
Health Risks Associated with Manganese Inhalation
Manganese generates toxic fumes when heated. Continuous inhalation of these fumes, even when within the standards set by OSHA, can lead to severe health impacts, including Manganism, damages to the lungs, liver, kidneys, and metal fume fever.
The severity of health effects depends on various factors, particularly the amount of inhaled manganese over time. As per Brad Racette, MD, from the Washington University School of Medicine in St. Louis: “The more exposure you have to welding fumes, the more quickly those symptoms progress over time.”
The CDC has examined the repercussions of inhaling manganese. Extended exposure to manganese-rich fume exceeding 1 mg/m3 concentration can lead to Parkinson-like symptoms. This progressive, disabling neurological condition, known as Manganism, results from an accumulation of manganese in the brain.
Symptoms may manifest as trembling, stiffness, slow movements, poor balance, depression, anxiety, and hostility. Some may experience the onset of the disease within a few months of welding, while for others, it may take 10 to 20 years.
Moreover, workers exposed to manganese levels lower than 0.2 mg/m3 may experience mood changes, short-term memory loss, decreased coordination, and altered reaction times.
Inhalation of manganese can also inflict damage on the lungs, liver, and kidneys, potentially causing fertility issues in male welders. Manganese, being toxic, can provoke lung irritation and pulmonary edema, and exacerbate metal fume fever.
Permissible Exposure Limit & Threshold Limit Values
US Regulations for Manganese Exposure
OSHA enforces a Permissible Exposure Limit (PEL) for manganese, set at 5 mg/m3. This limit (PEL-C) stipulates that the concentration of manganese in the welder’s breathing zone should never exceed this value. It is typically measured over 15-minute intervals.
In California, OSHA imposes a stricter PEL-TWA of 0.2 mg/m3 for manganese, marking the maximum 8-hour time-weighted average permissible. Additionally, they set a short-term exposure limit (PEL-STEL) of 3 mg/m3, meaning the average concentration could temporarily rise to this level for a maximum of 15 minutes. Such exposure should not occur more than four times daily, with at least 60 minutes between successive exposures within this range.
ACGIH (the American Conference of Governmental Industrial Hygienists) proposes a threshold limit value (TLV-TWA) of 0.02 mg/m3 of manganese in the welder’s breathing zone to avert long-term impacts on the nervous system. This value represents the maximum time-weighted average recommended during an 8-hour shift. Although this maximum concentration is a suggestion rather than a mandate from OSHA, many companies choose to adhere to it. Such measures are critical for welder safety, and it is likely that OSHA may adopt this recommendation as a future PEL.
NIOSH (the National Institute for Occupational Safety and Health) uses the term REL for Recommended Exposure Limit, as they only offer recommendations. Their 8-hour Recommended Exposure Limit (REL-TWA) is 1 mg/m3, with the maximum concentration for 15 minutes (REL-STEL) set at 3 mg/m³.
For current values, please refer to the OSHA Occupational Chemical Database.
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Manganese Exposure Limits in Canada
The following are the limitations for each Province and Territory in Canada. The table indicates TWA (Time-Weighted Average over 8 hours), STEL (Short Term Exposure Limit – maximum for 15 minutes, no more than four times per day with at least 60 minutes in between), and C (Ceiling), which must never be exceeded.
** Based on the ACGIH recommendation.
*** For 30 minutes during a continuous 24-hour period.
Handling Manganese Fume Exposure
If you inhale manganese fume, seek fresh air immediately. If breathing becomes difficult or if symptoms persist, worsen, or reoccur, promptly seek medical attention. Contact a Poison Control Center as well. It’s recommended to take the rest of the day off as pulmonary edema symptoms may appear after a few hours and are aggravated by physical activity.
In the event of manganese fume contact with the eyes, wash them thoroughly with copious amounts of water for at least 5 minutes or until irritation subsides. If possible, remove your contact lenses beforehand. Seek medical help as soon as initial aid has been provided.
In case of skin contact with manganese fume, rinse it off with water immediately.
Protecting Welders from Manganese
When it’s known that manganese is present in welding fumes, remember this simple guideline. If welding fume is visibly present around anyone’s face, they’re likely exceeding the exposure limit.
Here are some strategies to durably prevent health issues induced by welding fumes and manganese inhalation:
- Only weld when it is necessary. Other processes can sometimes replace manual welding.
- Use welding fume extractors.
- Isolate welding operations to protect other workers.
- Use welding processes and materials with as little manganese as possible.
- Make sure welders position themselves to avoid breathing fumes and gases.
- Make sure your factory is adequately ventilated.
- Use personal protective equipment if the previous measures are not enough.
Learn more about our comprehensive step-by-step method to solve welding fume problems.
Unless you can completely cease welding or employ isolated welding robots in a ventilated area without workers, you’ll require welding fume extractors.
Manganese and MIG welding (GMAW)
Adhering to the ACGIH recommendation of 0.02 mg/m3 of Manganese in the welder’s breathing zone can be challenging. However, a case study illustrated that it is indeed feasible with Fume Extraction MIG guns.
A steel parts manufacturer tested the AIRGOMIG gun over several days. An independent firm was hired to conduct air sampling as per recognized methods and protocols in Canada and the United States, with the sampling filter installed inside the welder’s helmet. The MIG gun was trialed during 8-hour shifts over three days with solid, metal-core, and fluxed-core wires. The average welding fume concentration remained between 0.45 and 0.69 mg/m3 (more than five times below OSHA’s PEL, which is 5mg/m3), and manganese oxide was held below 0.015 mg/m3 (ACGIH recommends 0.020 mg/m3).
For more information, read our article about fume extraction MIG guns.
Manganese and Other Welding Processes
For other welding processes like TIG or Stick welding, a flexible arm would be the optimal fume extraction solution. With proper positioning and sufficient airflow, fume extraction arms can reach an extraction efficiency nearing 100% and comply with applicable standards.
Alternatively, fume extraction nozzles could be an option, but their limited reach makes the results less reliable. Lastly, fume extraction hoods are not ideal to protect a welder as their head would be situated between the welding area and the hood itself.
Refer to our resources for other substances found in welding fumes and their exposure limits depending on your location.
Feel free to contact us. We will help you protect your workers and comply with welding fumes standards anywhere in the US and Canada.