Metal fabricating companies that seek to provide the safest work environments for their employees might be interested to know that the job might get a little harder in the welding department. The leading industrial health and safety organization that regularly issues guidance for certain toxic compounds is recommending a dramatic reduction in manganese fume exposure.
The American Conference of Governmental Industrial Hygienists (ACGIH) has recommended a 10-fold reduction in the time weighted average (over eight hours) threshold limit value for respirable manganese particulate. The association reduced the TLV-TWA limit of 0.2 mg/m3 to 0.02 mg/m3. In other words, a person should not breathe in more than 0.02 mg/m3 of manganese over an eight-hour work period.
Of course, this is only recommendation, not a governmental regulation. The current federal Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for manganese compounds is 5 mg/m3. This is a ceiling limit, which means the exposure shall at no time exceed the exposure limit given for a particular substance, in this case manganese. For the most part, if metal fabricators meet this standard on the shop floor, they are complying with federal law.
Prolonged exposure to manganese fumes without respiratory protection can be very bad for individuals. The link first was made back in 1837 when a British scientist witnessed neurological processing issues with Scottish workers responsible for grinding manganese. Today "manganism," which results from long-term and excessive ingestion or inhalation of manganese, has been linked to weakness, lethargy, paralysis, tremors, and speech and psychological disturbances.
Unfortunately for metal fabricators, manganese is prevalent in their work environment. The element is commonly found at different levels in many welding rods and filler metals, especially for those welding applications where hardness is desired. When the welding arc hits the manganese, the metal heats up and reacts with the oxygen in the air, creating manganese oxide fumes, which can be easily inhaled if a welder is not wearing the appropriate personal protection equipment.
If a metal fabricating company elects to try and meet the ACGIH guidance, it will have to rely on a combination of approaches, such as installing new ventilation equipment, changing welding practices, or incorporating more respiratory protection. Of course, any different approach likely is to result in more expenses for the manufacturer, which may deter even the most progressive of companies from pursuing changes influenced by the new guidance.