Among the 550,000 workers exposed to manganese and hexavalent chromium hazards in Canada, welders are the most at risk with 261,000 workers exposed. Welders naturally protect themselves against the visible dangers found in their work environment. But what about welding fumes?
As high-temperature arc welding can produce important levels of contaminants, welders are particularly at risk when it comes to airborne contaminants. The hazards of contaminant exposure can affect welders through inhalation, dermal absorption or ingestion, resulting in respiratory, digestive, nervous and reproductive disorders. For welders, manganese and hexavalent chromium are the most dangerous components of welding fumes.
Manganese and hexavalent chromium
Manganese is a metal commonly added to steel to increase its hardness. In the workplace, it is mainly found in welding rods and alloying elements. When manganese is heated, it reacts with the oxygen in ambient air, forming hazardous manganese oxide fumes. These particulates can be easily inhaled. Overexposure to manganese during welding may cause nose, throat and lung irritation. It can result in “metal fume fever”. Exposure to manganese was also linked to manganism, a disease presenting symptoms similar to Parkinson’s disease: weakness, lethargy, tremors and even paralysis. Manganese is also called an ototoxic agent, which means that it can lead to hearing loss.
Hexavalent chromium: Chrome can take different forms, but poses a major health issue in its hexavalent form. Hexavalent chromium can be found in many electrodes and steel welding wires. When welding stainless steel, this chrome type if found in fumes produced. The welding process using fluxes also produces a higher ratio of hexavalent chromium (Cr+6). It can be found in a variety of paints, pigments, dyes and plastics. In the event of prolonged contact with the skin, this element can cause irritation, ulcers and allergic reactions. Studies found important correlations between hexavalent chromium exposure and lung cancer.
3 tips to protect against the health effects of manganese and hexavalent chromium
When seeking protection against airborne contaminants, the first instinct is to think about protective masks and respirators. However, as advised by Stacey Blundell, 3M Advanced Development Specialist: “When we are facing air contamination issues, there are several steps to complete before choosing a respirator; the right industrial hygiene practices must be applied by dealing with the issue at its source.”1. Reduce the contaminant levels at the source
Ventilation is crucial for any cutting, welding or brazing operation. There are two types of ventilation to reduce the level of air contaminants: natural ventilation or mechanical ventilation.
Natural ventilation works through dilution. Welding outside with a light breeze or inside with the windows and doors open, in some cases, reduces the level of contaminants. Natural ventilation through dilution must not be used alone when welding, cutting or brazing in confined spaces or areas where structures hinder the natural air flow.
Mechanical ventilation is usually the choice of welding shops. Ventilation equipment, such as exhaust fans and wall fans, carry the outside air throughout the building. A properly installed mechanical ventilation can help reduce the concentration of fumes in the welder’s breathing zone.
Welding outside in open spaces or with the assistance of local ventilation does not guarantee that exposures will be below acceptable limits. All types of ventilation must be designed, installed and maintained adequately to successfully reduce exposure for workers. Employers need to perform an ongoing assessment of fume and smoke exposure to make sure they are below the acceptable limits, or implement additional controls.2. Choosing the right products
Good practices favour substitutions as a method to reduce workers’ exposure to welding fumes. Whenever possible, the most efficient control is the elimination of the danger using a more secure process or material. Here are a few key considerations:
- Prefer the use of less dangerous material. For example, manganese-free welding rod.
- Consider another welding method that generates less welding fumes. For example, TIG or MIG welding produces less fumes than tubular wire arc welding.
- Choose alternative gases that can affect smoke generation.
- Use computers and 3D printers to simplify design and reduce the amount of welding.
- Can surfaces be riveted or glued together?
- Welding surfaces must be cleaned of any coating that could create a toxic exposure, such as paint and solvent residues.
When ventilation and other measures are insufficient to decrease the concentrations below the established standard or when the welding process releases toxic and carcinogenic fumes (such as for stainless steel and chromium 6+), a protective mask must be worn. Select the type of respirator according to the measured exposure and the exposure value.
Disposable protective masks or half-mask respirators with filters are appropriate for fume concentrations not exceeding 10 times the standard. For higher exposures, there are full-facepiece respirators or supplied air respirators with filters. In environments where fumes or gases concentrations can pose an immediate danger, a self-contained breathing apparatus (SCBA) or a supplied air respirator with a reserve cylinder should be used.
PROTECTIVE MASKS AND Respirators: and what about the law?
The equipment shall be selected, adjusted, used and cared for in accordance with the CSA Z94.4-93 Standard Selection, Use and Care of Respirators. A respiratory protection program shall be drafted and applied in compliance with that standard.
Whether they are disposable respiratory protective masks or powered supplied air respirators for higher contaminant concentrations, there is a wide range of products to protect the lungs and respiratory tract. Look for products using electrostatic technology, such as the 3M AdfloTM, letting clean air through while reducing harmful concentrations of particles, dusts and fumes potentially ending up in the lungs.