There have been recent changes by ACGIH to manganese occupational exposure limits (OEL) which may have an effect on various industries and industrial processes. One of the more recent ailments , identified by the National Institutes of Health, that can afflict welders is manganism, also known as welder's disease.
Overexposure to manganese fume has been linked to weakness/lethargy, speech and psychological disturbances, paralysis, and tremors.
Current OSHA Requirement – 5 mg/m3
2012 ACGIH TLV - .2 mg/m3
New 2013 ACGIH TLV - .02 mg/m3
*note OSHA Regulations are Not Changing at this time
Manganese is a grey-white metal resembling iron. Manganese is used extensively to produce a variety of important alloys and to desulfurize and deoxidize steel. Manganese is also in many welding rods and filler metals to promote hardness. Manganese oxide fume is formed when manganese metal is heated and reacts with oxygen in the air such as occurs during welding.
Manganese is found in many manufacturing processes. The recent change to manganese exposure limits may have an effect on various industries and industrial processes. As a precaution, review Material Safety Data Sheets (MSDS) for materials containing these substances in manufacturing processes.
If there are questions regarding the air quality, it may be a good idea to discuss the option of air sampling with an industrial hygienist to better determine the levels of contaminants within a given process.
If the air sampling results indicate exposure levels above the occupational exposure limit (either PEL or TLV, whichever the employer is using) , changes to manufacturing processes, use of other engineering controls or PPE may be suitable choices to reduce employee exposures to acceptable levels.
The current Federal OSHA PEL for manganese compounds, including manganese fume, is 5 milligrams per cubic meter of air (5 mg/m3)(1). This PEL is a ceiling limit which means the exposure shall at no time exceed the exposure limit given for that substance. Note, “state plan” states are required to have standards, policies and procedures at least as effective as those of Federal OSHA. If you are in an area under the jurisdiction of a state OSHA plan, consult local standards for current OSHA exposure limits.
Respiratory Protection for Manganese Exposure
In many cases, changes in manufacturing processes and engineering controls alone can't reduce exposure levels to below the OELs. In such cases, it may be appropriate to use respiratory protection. For any particular application, an array of respirator types that provide an appropriate level of protection is available. The cost of these respirators may vary from around $1 for a basic negative-pressure, disposable, filtering facepiece to $1,000 or more for a powered air purifying or supplied-air system. Respirators should be selected based on results from air sampling and the necessary assigned protection factor (APF) as established within OSHA 29 CFR 1910.134. OSHA requires employers to implement a written respiratory protection program when respiratory protection is used. Elements of the written program include respirator selection, use, care and maintenance, medical evaluation, training, and fit testing for tight fitting respirators.
Respirator Selection for Manganese Oxide Fume Exposures
The table below shows suggested respiratory protection for manganese up to the maximum use concentrations based on the OSHA respirator APFs and ACGIH TLV of 0.02 mg/m3 for respirable fraction.