Manganese is one of the most common elements welders and metalworkers are exposed to—and one of the most problematic. This soft, silvery metal, used in stainless steel and aluminum alloys, is a major component of many welding consumables.
It is also implicated in a number of health problems, including manganism, metal fume fever, lung disease, and kidney disease. That’s why the Occupational Health and Safety Administration (OSHA) strictly regulates exposure to manganese in weld fumes and metalworking dusts.
Understanding OSHA Regulations and Safety Standards for Manganese Exposure
OSHA has set the Permissible Exposure Level (PEL) for manganese at 5 mg/m3 as a ceiling. That means that there can be no more than 5 milligrams of manganese particulates in every meter cubed of air in the facility at any time. OSHA PELs have the force of law; employers must meet this standard or risk substantial fines and penalties.
However, meeting the OSHA PEL may not be enough to protect workers from adverse health impacts of manganese exposure. The National Institute of Occupational Safety and Health (NIOSH) recommends lower exposure levels based on the scientific evidence of the toxic effects of manganese. NIOSH has two standards employers should be aware of:
- PEL: NIOSH sets the recommended PEL for manganese at 1 mg/m3as a Time Weighted Average (TWA), meaning exposure should not exceed this level as an average over an 8-hour shift.
- Short Term Exposure Limit (STEL): NIOSH has set a STEL of 3 mg/m3, meaning exposure should never be above this level even if the shift average is still below 1 mg/m3.
Recommendations from the American Conference of Government and Industrial Hygienists (ACGIH) are even lower. They have set a Threshold Limit Values (TLVs®) for manganese at just 0.1 mg/m3 TWA or 0.02 mg/m3 TWA for respirable particulate matter. These guidelines are based on the latest scientific research on the exposure levels associated with toxicity to body systems.
Meeting or Exceeding OSHA PELs for Manganese
All manufacturers must meet OSHA PELs for manganese exposure. But due to the potential health risks, many manufacturers may want to go even further, striving to meet NIOSH or ACGIH recommendations.
Fortunately, manufacturers have many options when it comes to reducing exposure to weld fumes or other sources of respirable manganese particulates. Here are some steps manufacturers can take:
- Evaluate your current exposure levels. Dust concentration meters can be used to measure overall particulate levels. Manganese concentrations can often be extrapolated from the total particulate measurement based on your processes and materials, or collected dust can be sent to a lab for analysis. Measurements should be taken both in the general facility and in the breathing zones near areas where weld fumes or dust are generated.
- Install effective engineering controls. Dust collectors capture and filter contaminated air and return clean air back to the facility. Whenever possible, manufacturers should use source capture solutions to collect dirty air where it is generated. If source capture is not possible, ambient filtration systems can be used to clean air for the facility as a whole. An experienced air quality system designer can help manufacturers select the best remedy option for their processes, facility layout and the volume of dust or fumes they produce.
- Prevent the spread of dust and fumes through the facility. Manufacturers may want to consider using curtains or walls to partition off manganese-producing processes and make fumes easier to collect. Smart Building Pressure management, which uses zones of positive and negative air pressure to contain and manage fume migration, can be highly effective as well, especially in large, open facilities. Companies should also implement effective housekeeping and industrial hygiene practices to prevent the spread of manganese-containing dusts through the facility.
- Provide personal protective equipment (PPE) to workers exposed to high levels of manganese. OSHA mandates that engineering controls must be used as the first line of defense in meeting PELs. However, if it is not technically feasible to bring manganese levels within PELs in all areas of the facility, employees with higher exposure levels should be provided with PPE such as a Powered Air Purifying Respirator (PAPR) system. Companies may want to consider offering PPE on an optional basis to employees exposed above the NIOSH or ACGIH guidelines.
Read more about manganese exposure and control options.