Critical Particulate Contaminant(s) Generated during Arc Welding on Aluminum Alloys

Assessing exposure to particulate emissions during arc welding is an important consideration in assuring compliance with regulatory requirements. This study examined welding emissions during argon-shielded GMAW (MIG welding) processes involving aluminum alloys in a shipbuilding environment using traditional methods of air sampling (portable pumps and closed-face cassettes containing PVC filters.) Current requirements for exposure determination (inhalable, respirable and total particulates) necessitate three simultaneous samples, a very onerous imposition on worker safety and comfort. Application of a conversion factor published in the literature can considerably simplify this situation through use of a single sampler, the conventional closed face cassette. This approach provides a first-level means of evaluation and is especially useful where exposure levels are low compared to regulatory Exposure Limits. Assessment of exposure to chromium, magnesium and manganese may require additional consideration because of the necessity for simultaneous evaluation against TLVs for inhalable and respirable particulates and different oxidation states. Results strongly suggest that beryllium and/or chromium VI and possibly manganese dominate consideration about exposure and control measures (Critical Particulate Contaminant). This results from the difficulty of analysis created by the combination of extremely small Exposure Limits, presence of these elements in the alloy in trace to very small quantities and uncertainty associated with detectability in standard air samples. Resolving this question requires collection and analysis of bulk quantities of welding fume to improve the mathematics associated with detectability. Determination of the Critical Particulate Contaminant considerably simplifies future evaluation and focuses follow-up action in the appropriate direction.