Abstract
The objective of the paper is to share the scientific basis for adopting the new ACGIH TLV for manganese (Mn), and to discuss the systematic process for implementing the change across businesses involving both employee and contractor workforces. In addition, it will describe the minimum worker controls and optional strategies that were implemented to control manganese and other metal fume exposures during welding and hot work. A review of manganese welding exposure data and available worker controls (engineering, administrative controls, PPE) is provided.
The approach involved both the review and validation of the science that provided the basis of the ACGIH TLV for manganese using an internal Occupational Exposure Limit (OEL) development and review process, and the assessment of manganese exposure during welding and hot work. Based on the risk of worker exposure to manganese above the ACGIH TLV, an implementation strategy was developed that included exposure monitoring, review of work activities with exposures over the OEL, changes to existing work controls, communications to management and field supervision, review of available control technology, and engagement with the welding community.
Exposure data and minimum work controls were successfully reviewed with line management and welders (both contractor and employee). The understanding of the Mn exposure data and the potential adverse health effects of overexposure facilitated the demonstration and trial use of new technology powered air purifying respirators (PAPRs) by contract welders working on a pipeline project. Lessons learned have been shared with the PAPR manufacturers and incorporated in training and safety and health procedures. The implementation of new work controls has required changes to existing work practices by welders and their helpers.
Key learnings from the implementation of new welding work controls are that significant time and effort must be put into understanding the science and basis of the exposure limit and gathering exposure data to compare to a new limit. If there is the potential for overexposure based on the operations and work tasks, then a review of available control technology (e.g. reduced manganese in welding rods/wires, portable ventilation equipment, feasible respiratory equipment) is required before developing and documenting minimum work controls. Finally, a robust strategy for communication to line management, employees, and contractor management must be developed.
Explain new/novel information to existing body of literature:
Application of a new Mn exposure limit drove the use of more protective work controls than were previously used by the majority of the welding community, which typically follows the OSHA permissible exposure limit (PEL) for manganese that was established in 1968. This paper provides practice-based methodology in overcoming the challenges associated with implementation of the new ACGIH TLV in welding applications.
