by Phillip C. Fincher, CIH, CSP
Senior Vice President

Conformance with the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) for Manganese continues to challenge many employers despite numerous layers of engineering controls.  The current TLV of 0.02 mg/m3 (respirable) and 0.1 mg/m3 (inhalable) is a ten-fold reduction from the previous TLV of 0.2 mg/m3 as an 8-hour Time Weighted Average (TWA).  The current, enforceable OSHA Permissible Exposure Limit (PEL) is 5.0 mg/m3 as a ceiling limit. The ACGIH TLVs are intended to represent levels of exposures that nearly every worker may be exposed to throughout their working career without suffering adverse health effects.  Literature suggests that exposure to manganese found in welding fumes and other forms of manganese are associated with neurological impairment in workers.  Although additional research is required to fully understand the health effects of welding fume exposures, employers and manufacturers of welding equipment and supplies continue to evaluate control strategies to reduce exposures.


Although most employers have performed welding fume surveys, I would encourage them to re-evaluate their exposure data to ensure that the sampling and analytical method used for the survey has a sufficiently low limit of detection (LOD) to ensure that values reported as below the LOD are below the TLV.  There have been numerous improvements in analytical methods to reduce the limit of quantitation (LOQ) and LOD.    A professional industrial hygienist should be consulted to review historical data and accurately evaluate employee exposures to welding fumes, manganese and other airborne chemical hazards.  An industrial hygienist will also be able to assist employers with the selection of feasible engineering controls, administrative controls and personal protective equipment (PPE).    If employers are limited to the use of respiratory protection they must ensure that they have a respiratory protection program as specified in OSHA Standard 1910.134 for Respiratory Protection.