Welding is an essential industrial process. It’s so commonly performed these days, you could say that it’s ubiquitous in industry. Welding produces a range of potentially toxic metal fumes from welded material, welding rods or fluxes. Appreciating the hazards involved, Noah Seixas gave a keynote lecture at the recent BOHS Conference in the UK on the recent advances in welding exposure assessment and control. One of the main items of focus was on fume-related health effects, particularly the neurological health effects of welders who develop a condition known as “Manganism” brought about by exposure to manganese.
Although manganese is an essential trace element, when welders are exposed to high concentrations over a prolonged period of time, it can cause neurological disorders involving the central nervous system, where the worker develops a tremor-like syndrome which resembles Parkinson’s disease. Manganism usually begins with psychological symptoms such as hallucinations, emotional instability and disturbances in behaviour. These may be followed by neurological symptoms such as muscular weakness, speech disturbances and headaches, as well as symptoms resembling those of Parkinson’s disease. If exposure ceases after the neurological symptoms appear, the worker generally recovers, but some speech and balance problems may remain.
Controlling exposure to manganese is crucial to preventing occupational illness and may include elimination (eg: changing the welding type), substitution (eg: changing the welding rod with one that contains less manganese), engineering (eg: local exhaust ventilation), administration (eg: reducing exposure time, medicals, and training), and the use of PPE (eg: respirators).
Using a box model, Noah broke down the often complicated explanation of the determination of welding smoke exposure as a simple communication tool. As is shown in the graphic below (sourced here) it includes the number and types of welding, the room size, and the amount of air moved through the space.
Using a similar format, Noah then explained the top three ways that workers can reduce their welding smoke exposure using the simple graphic below.
The study that Noah discussed, involved a review of peer-reviewed literature and demonstrated that stick welding, MIG welding, and dual shield welding brought about the highest risk of exposure to manganese in air to the welder. The key is to make sure that if you can’t reduce the amount of manganese at the source, then you need to focus your energy into a local exhaust ventilation system to remove the welding fume rather than relying on PPE, which will always be less effective. Whilst numerous control methods were discussed, it was clear that unfortunately there still remains a heavy reliance on the welder to wear PPE such as the use of Powered Air Purifying Respirators (PAPRs).
Where PPE is used to control exposure, it can be difficult to know how effective it really is at protecting the worker. In such cases, biological monitoring is typically recommended. This is tricky when it comes to manganese though. In Australia, Safe Work Australia state, “In regard to biological monitoring, the significance of manganese in urine is still difficult to assess. On a group basis, manganese in blood seems to be more of an index of body burden than of current exposure. Accordingly, results from biological monitoring for manganese need to be treated with particular caution”. The NSW TestSafe WorkCover Laboratory go on to state, “Manganese in urine reflects recent exposure. Better interpretation of exposure is obtained on a group basis as excretion rates vary with dose. It has been suggested that blood and urine measurements are useful for confirming exposure”. So basically it’s not as simple as collecting a urine sample and comparing that measurement to a reference value provided by Safe Work Australia (there isn’t one). It’s times like these when you really need an Occupational Hygienist to provide advice and assistance to make sure your workers are protected.
So getting back to the study Noah presented, one of the (many) interesting things he discussed was the potential use of hair as an exposure biomarker as it’s easily collected and has a fairly constant growth rate. Biological monitoring tends to be invasive, so its great when other methods are identified that may achieve the same outcome. As with any method, limitations exist in using them, and in the case of using hair, the limitations include the uncertainty for Manganese affinity and the need to thoroughly remove all surface contamination…but it’s a great start!
If you are a welder or have welding activities located in your place of work and want some advice from an Occupational Hygienist, then you can find one in the AIOH consultant directory here.