Welders in Canada Overexposed to Hazardous Fumes

A recent study out of Manitoba (Canada) has found that a large proportion of welders in the province are overexposed to hazardous welding fumes.

The two-year study, entitled "Protecting Workers from Welding Fumes," examined 40 companies across the province through a grant from the Workers Compensation Board of Manitoba. It discovered that half of the metal inert gases (MIG) welders tested who were not using respiratory protection or local exhaust ventilation were overexposed to welding fumes. (WCxKit)

By contrast, where these two controls were used, "workers were consistently found to be exposed to safe levels of welding fumes," comments Doug Wylie, the report's author and a director of OHG Consulting in East St Paul, Manitoba.

The study points out that a large part of workers' exposure comes from manganese in the welding wire. "It has been suggested that as much as 95 per cent of the welding fume actually originates from the melting of the electrode or wire consumable," Wylie writes.

Analysts of the report point to a company in the study in which seven tested workers had exposures above the permissible level, with the average exposure being 192 percent of the permissible amount. When the company switched to a welding wire with lower manganese content, workers were re-tested and the average exposure was 52 percent of the permissible level.

The study offers several precautions that welders can take to help reduce exposures, such as arranging work so that the welder is out of the rising plume (rotate material so that the worker is welding beside a vertical or angled surface rather than above a horizontal surface).

Working in a down-flat position, such as welding a tank bottom or where the work piece is positioned below the welder's waist, tends to present the highest potential fume exposures, the study says.

Welding in a horizontal direction, such as when welding the girth seam of a tank, can also create high exposures, depending on the plume's path of travel in relation to the welder's breathing zone. Welding in a vertical direction, like the vertical seam of a tank shell, tends to have the lowest potential fume exposure since the welder's breathing zone is typically not in the plume's travel path and the plume stays close to the heat-affected zone as it naturally rises, Wylie writes.

In addition to positioning, ventilation is another important consideration. There are two main types: local exhaust ventilation, where contaminated air is exhausted from the building, and general ventilation, where fresh air is brought into the building to purge and dilute the airborne contaminants.

The first type uses an extraction system located very close to the point of welding fume generation to extract fumes immediately from the environment without allowing the air to enter the worker's breathing zone. Of the 30 welders who were tested using this form of ventilation, none were overexposed.

On the other hand, general ventilation may "only be partially effective" because the main pathway of exposure is between the welding fume generation and the breathing zone of the welder, the study notes. (WCxKit)

Author Robert Elliott, executive vice president, Amaxx Risks Solutions, Inc. has worked successfully for 20 years with many industries to reduce Workers Compensation costs, including airlines, healthcare, printing/publishing, pharmaceuticals, retail, hospitality and manufacturing. Contact: [email protected] or 860-553-6604.

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