Manganese is an essential mineral for the body but can also be toxic. The liver and kidneys excrete dietary manganese excess. Inhaled Manganese bypasses this defense mechanism, and breathing welding fumes with Manganese can lead to an accumulation that could cause multiple health problems.

Manganese is a hard, gray metal used to produce steel. When welding, manganese particles can be found in welding fumes and be breathed by welders. In this article, we will see how welders are exposed to Manganese, what are the exposure limits, and how to prevent the various health effects that manganese fume can have.

How are welders exposed to Manganese?

Most welders are exposed to Manganese (Mn). Mn fumes are especially problematic with high-tensile and low-alloy steels, ferrous alloys, or some copper, aluminum, and nickel alloys. Usually, they contain less than 2% of Mn, but some have as much as 16%. The amount of Mn in the welding wire, rods, and flux is also important.

It is essential to be aware of the composition of metals, gases, and consumables used in the process to know with which substances welders will be in contact. Even more so when welding in confined spaces since it can significantly increase exposure to manganese fumes and other hazardous substances.

Welding fumes are a mixture of different metals and gases and contain a small percentage of Manganese in most cases. It may be in various oxidation states (such as manganese dioxide, manganese tetroxide, or manganese trioxide) and have different solubility properties. Manganese particles in welding fumes are usually between 0.001 and 100 µm. Therefore, they may deposit throughout the respiratory system.

Health effects if you inhale Manganese

When heated, Manganese produces toxic fumes. If they are inhaled for a prolonged period, even if the concentration is maintained within OSHA’s standards, these fumes can have devastating health effects including: Manganism, damages to the lungs, liver, and kidneys, or metal fume fever.

Health effects will vary depending on many factors, especially the amount of Manganese breathed over time. According to 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 studied the effects of inhaling Manganese. Prolonged exposure to fume with a manganese concentration over 1 mg/m3 can cause Parkinson–like symptoms. This progressive and disabling neurological condition due to an accumulation of Manganese in the brain is called Manganism.

Symptoms may include trembling, stiffness, slow movements, poor balance, depression, anxiety, and hostility. The disease can appear after welding for a few months for some people. For others, it can be after 10 or 20 years.

On top of that, workers exposed to levels of Manganese lower than 0.2 mg/m3 could suffer the following symptoms: changes in mood, short-term memory loss, reduced coordination, and altered reaction time.

Breathing Manganese can also damage the lungs, liver, and kidneys, and could create fertility problems for male welders. In addition, Manganese is toxic, can cause lung irritation and pulmonary edema, and is an aggravating factor when it comes to metal fume fever.

Permissible Exposure Limit & Threshold Limit Values

PEL & TLV for Manganese in the US

The Permissible Exposure Limit imposed by OSHA for Manganese is 5 mg/m3. It is a ceiling limit (PEL-C), meaning that the concentration of Manganese in the welder’s breathing zone is never supposed to go over that. Usually, it is measured over periods of 15 minutes.

In California, OSHA’s PEL is even more strict. They impose a PEL-TWA of 0.2 mg/m3 for Manganese, which is the maximum 8-hour time-weighted average allowed. In addition, they add a short-term exposure limit (PEL-STEL) of 3 mg/m3, which means the average concentration could temporarily go as high as this amount for a maximum of 15 minutes. It should occur no more than four times daily, with at least 60 minutes between successive exposures in this range.

ACGIH (the American Conference of Governmental Industrial Hygienists) recommends a threshold limit value (TLV-TWA) of 0.02 mg/m3 of Manganese in the welder’s breathing zone to avoid long-term effects on the nervous system. This is the maximum time-weighted average recommended during an 8-hour shift. Although this maximum concentration is only a recommendation and is not enforced by OSHA, many companies decide to follow it. It is vital to protect welders, and OSHA will likely use this recommendation as a new PEL at some point.

NIOSH (the National Institute for Occupational Safety and Health) uses the acronym REL for Recommended Exposure Limit as they only make recommendations as well. Their Recommended Exposure Limit over 8 hours (REL-TWA) is 1 mg/m3, and the maximum concentration for 15 minutes (REL-STEL) is 3 mg/m³.

You can check the OSHA Occupational Chemical Database to ensure these values are still applicable.

If you have any questions about welding fume, do not hesitate to contact us. We will be happy to give you some insight, and we can even visit you for free in the US and Canada.

Henlex Inc.

Exposure Limits for Manganese in Canada

Here are the limits per Province and Territory in Canada. In the table, TWA means Time-Weighted Average over 8 hours. STEL means Short Term Exposure Limit (maximum for 15 minutes, no more than four times per day with at least 60 minutes in between). C means Ceiling, which must never be exceeded.


* (t) = total / (r) = respirable
** Based on the ACGIH recommendation.
*** For 30 minutes during a continuous 24-hour period.

What to do if you get in contact with manganese fume?


If you inhale manganese fume, get some fresh air. If you have some difficulty breathing or if the symptoms worsen, persist, or reappear, make sure to see a medical professional as soon as possible. You should also call a Poison Control Center. It is better to rest for the day as pulmonary edema symptoms can appear after a few hours and are worsened by physical activity.


If manganese fume gets in contact with the eyes, immediately wash them with large amounts of water for at least 5 minutes or until the irritation is gone. Remove your contact lenses before, if possible. Get medical attention as soon as possible after first aid has been given.


If manganese fume gets in contact with your skin, immediately rinse it with water.

Protect welders against Manganese

If you know there is Manganese in welding fumes, here is a simple rule of thumb. If you can see welding fume in anyone’s face, they are very likely above the exposure limit.

Here are a few tips to sustainably prevent health problems caused by welding fumes and Manganese inhalation:

  1. Only weld when it is necessary. Other processes can sometimes replace manual welding.
  2. Use welding fume extractors.
  3. Isolate welding operations to protect other workers.
  4. Use welding processes and materials with as little manganese as possible.
  5. Make sure welders position themselves to avoid breathing fumes and gases.
  6. Make sure your factory is adequately ventilated.
  7. Use personal protective equipment if the previous measures are not enough.

Learn more about our step-by-step method to solve welding fume problems.

Unless you can stop welding altogether or use welding robots isolated in a ventilated area without workers, you will need welding fume extractors.

Manganese and MIG welding (GMAW)

It isn’t easy to meet the ACGIH recommendation of 0.02 mg/m3 of Manganese in the welder’s breathing zone. But a case study showed that it is indeed possible with Fume Extraction MIG guns.

A steel parts manufacturer tested the AIRGOMIG gun over several days. An independent company was commissioned to perform air sampling according to methods and protocols recognized in Canada and the United States, the sampling filter being installed inside the welder’s helmet. The MIG gun was tested during 8-hour shifts over three days with solid, metal-core, and fluxed-core wires. The average welding fumes concentration was kept between 0.45 and 0.69 mg/m3 (more than five times below OSHA’s PEL, which is 5mg/m3), and manganese oxide was maintained below 0.015 mg/m3 (ACGIH recommends 0.020 mg/m3).

You can read or article about fume extraction MIG guns to learn more.

Manganese and other welding processes

The best fume extraction option for other welding processes, such as TIG or Stick welding, would be a flexible arm. With proper positioning and sufficient airflow, fume extraction arms can achieve an extraction efficiency close to 100% and meet the applicable standards.

Otherwise, fume extraction nozzles could be an option, but their limited reach makes the results less predictable. Finally, fume extraction hoods cannot protect a welder as their head would be between the welding area and the hood itself.

Check out our resources for other substances found in welding fumes and their exposure limits depending on your location.

Any Questions?

Feel free to contact us. We will help you protect your workers and comply with welding fumes standards anywhere in the US and Canada.