ACGIH has adopted a dramatically lower TLV-TWA for respirable manganese particulate. The previous TLV of 0.2 micrograms/cubic meter has been lowered to 0.02 micrograms/cubic meter as stated in the 2013 ACGIH TLV/BEI Booklet. Welders, in particular, are susceptible to exposure to manganese as it is found in many welding rods and filter metals to promote hardness. Safety professionals in the metal fabricating industry are finding themselves rethinking personal protective equipment recommendations.

Informational Article
thefabricator.com