Despite the inherent dangers of breathing toxic welding fumes, companies continue to put their workers at risk. Alan Johnson reports.
It has been shown that a single welder produces 20 to 40g of welding fumes per hour which corresponds to about 35 to 70kg per year.
Most welders understand the many health risks of working in the fabrication industry, which include electric shocks, fire, explosions and radiation exposure, but it appears that one of the biggest threats to a welder’s health - toxic welding fumes - is being ignored by many welders and their employers.
Research shows a lack of familiarity with the gases used or fumes produced during the welding processes can be a serious health risk. Workers can become ill if dangerous fumes are not removed from the workplace.
OHS groups say it is essential welders are familiar with the materials being used (such as gases, base metals, coatings and cleaners) and their possible health impact.
Research reveals fumes produced during welding processes can lead to workers experiencing eye, skin and respiratory system irritation, nausea, headaches and dizziness. In some cases, the fumes can cause serious lung diseases and increase the risk of asthma and cancer and possibly lead to asphyxiation.
However, despite all these warnings, Oscar Barahona, Sales Manager – Metal Fabrication Products with Nederman, says many manufacturers are unaware of the need for adequate fume extraction to create a safe working place.
“Some companies just rely on an open roller door, a fan on the roof or a fan in the wall as the only form of ventilation in their factories for these toxic welding fumes.
“While these fans are able to effect a number of air changes per hour or minute, the problem is the welders, and the others with them, are still exposed to the fumes, due to the fact the fumes pass the welders and others breathing zones.”
“Welding should always take place in a well ventilated area to allow the toxic fumes and gases to escape. Central ventilation systems or large extraction hoods over workbenches are often completely inadequate: the welder or operator cannot avoid inhaling the fumes as these always contaminate the general airflow.
“Nor are systems like these cost-effective: they require a great deal of power to run as they extract enormous quantities of heated air from the premises.
“Extraction-at-source is most effective – as soon as the fumes are generated. Our extraction arms, for example, can be positioned as close as 300-400mm away from the weld without impacting the shielding gas or the welding process.
“Wherever it is a viable solution, it has been proven that extraction-at-source is the most effective and efficient method of capturing and removing welding and similar fumes.
“Using this method, the risk of the welder or operator being subject to hazardous fumes is minimised,” Barahona said.
He pointed out that Australian Standard AS 1668 calls for extraction-at-source, and that Worksafe also encourages companies to provide these types of systems for the welders.
“As well, most welding training centres are very aware of the need for these systems, however once the welders leave the centres and go out into industry they find a completely different situation.
“Many manufacturers still see safety of its workers as a cost. I estimate of the 70 to 80 factories I visit every year, only around 10 per cent use extraction-at-source equipment.
“I was shocked at one company I visited recently, where the workers said they needed to take a couple of days off after finishing a job because of the fumes generated when welding aluminium.
“If these manufacturers take more care of their workers, their companies’ number one asset, workers will appreciate it and perform better and be more productive when using the correct equipment,” Barahona said.
Fumes from different welding methods
It has been shown that different welding methods give rise to different amounts of fumes containing different concentrations of hazardous substances.
Among the high-risk elements are hexavalent chromium Cr(VI), manganese, nickel and lead.
The particles at source are often extremely small; 0.01-0.1µm which means they are very easy to inhale deep into the lungs.
Furthermore, not only welders are at risk in unsafe environments. Production equipment, as well as end products, are negatively affected by the lack of adequate safety measures.
During welding, the intense heat of the electric arc vaporises a fraction of the metal in the electrode and weld pool.
Any metal vapour that escapes the arc area condenses as it cools and oxidises into weld fume. The vapour that develops condenses as it cools and oxidises into weld fume containing a complex mixture of metal oxides.
Particulate fume is formed mainly by vaporisation of metal and flux. As it cools, the vapour condenses and reacts with the atmospheric oxygen to form fine particles.
The size of the particles (0.01 - 1µm) tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger.
Additionally, many processes produce various gases (most commonly carbon dioxide and ozone, but others as well) that can prove dangerous if ventilation is inadequate.
Many readers may not realise that around 90% of the fume originates from the consumable, while the base metal only contribues very little.
The fume contains all the elements present in the consumable, but often in very different proportions. Volatile components have a higher concentration in the fume than in the consumable and the opposite is true for components with a high melting point.
The amount of welding fume varies between different welding processes: Fumes from manual metal arc (MMA) welding and fluxcored arc welding (FCAW) contain a high proportion of components coming from the electrode coating or the flux core.
Comparatively little comes from the filler metal.
Fumes from metal inert gas (MIG) and metal active gas (MAG) welding contain high concentrations of the metals being deposited.
It has also been shown that particles in welding fume are small enough to be suspended in the air for a long time.
They can be inhaled and penetrate into the innermost area of the lungs. Over time, the particles can even reach the bloodstream.
Fumes from MMA and FCAW welding usually contain significant quantities of hexavalent chromium Cr(VI).
This is important to observe because hexavalent chromium Cr(VI) has a very low exposure limit. There are also risks due to the presence of manganese, nickel and other elements.
Welding Chromium VI – Cr(VI)
Stainless steel is a ferrous alloy with a minimum of 10.5 % chromium content.
The chromium in the steel combines with oxygen in the atmosphere to form a thin, invisible layer of chrome-containing oxide, which enhances the corrosion resistance.
Hexavalent chromium or Cr(VI) compounds are those that contain the element chromium in the +6 oxidation state. Chromium in the base material and the welding electrode (consumable) does not normally appear in the form of hexavalent chromium.
However, during the welding process the alkali based flux compound reacts with the chromium generating CR(VI), which emits into the welding fumes.
Cr(VI) is a known carcinogen and investigations have clearly shown that exposure to Cr(VI) can have a very dangerous effect on health.
Manganese is essential to iron and steel production by virtue of its sulfur-fixing, deoxidizing, and alloying properties.
Manganese is also a key component of lowcost stainless steel formulations. Long-term or chronic exposure to manganese fumes or dust at high concentrations can damage the nervous system and respiratory tract, as well as having other adverse effects. Wide spectrums of neuropsychiatric illnesses have been described with manganese toxicity.
Among the neurological effects is an irreversible Parkinsonian-like syndrome.
The neurological disorder resulting from this type of manganese toxicity is known as Parkinson’s Manganism.