Steel is made into "stainless" alloys with the addition of 4 percent to 30 percent chromium, and the typical stainless steel alloys contain about 10 percent chromium. In the alloys, chromium reacts with oxygen to form a tough, passive, surface layer of chromium oxide that prevents iron in the alloy from oxidizing to form rust.

When the heat of a welding or cutting torch is used on these alloys, the base metal and/or the electrode coating convert to submicron-sized particles that become airborne as fumes, and those fumes can contain particles of chromium. Some of that chromium can be chemically altered by the heat from the process and, in the presence of oxygen, it can become hexavalent chromium, a recognized carcinogen.

Health issues
Hexavalent chromium is also referred to as Chrome Six, Cr6 and Cr(VI). Some industries use it in compounds to add anti-corrosion properties to their product. Hexavalent chromium compounds do not occur naturally — they are man-made, and they are the only form of chromium that is toxic.

Hexavalent chromium causes lung cancer in humans. However, exposure to hexavalent chromium also irritates the skin, and prolonged skin contact can result in dermatitis and skin ulcers. Breathing it also damages the nose, throat and lungs. And, some workers can develop an allergic sensitization to chromium.

Like many other substances that are identified by government health agencies as "toxic," the exact amount of hexavalent chromium that will injure a worker is not known. Sensitivity levels and how this toxic compound can affect the health of an individual worker are different.

Government standards
OSHA updated standards regarding exposure to hexavalent chromium in the workplace in 2006, and those standards were put into effect in stages, according to shop size. The standards become universally applicable to all industries and all shops, including those involved in the welding and hot cutting of stainless steel, on May 30, 2007.

The new standard reduces permissible employee exposure from 52 micrograms (m g) per cubic meter to 5 micrograms per cubic meter for an individual worker's air over an 8-hour work shift. The new standard indicates a level at which most workers will have a reduced opportunity to develop long-term illnesses.

Dealing with fumes
Most weld shops have work areas surrounded by a curtain or wall, to protect others in the area from the glare of the welding spark. Areas in which hexavalent chromium fumes may be generated should be clearly marked with boundary lines, to warn other employees that they may be entering a hazardous zone. Floor fans often are set up to move fumes in shops, but metal particles can remain airborne, and fumes circulated by floor fans could be moved to surrounding work areas.

Many shops are turning to fume extraction systems to eliminate the danger of these fumes and to protect their workers' health. Such a system could include a central air movement/filtration unit that has ducts that run to each welder. Those systems typically are designed for large shops.

Shops also use portable units that are designed for a single welding station. Alternatives include booth-type systems that remove fumes generated by welding robots. Air that is filtered and exhausted from such fume extraction systems usually is safe enough to re-circulate with the shop's air.

For workers who have higher sensitivities to inhaled irritants, personal respirators fitted to weld helmets may be required. These respirators include individual blowers and filter packs that ride on the back of the workers belt. Ordinary paper mask filters are not sufficient protection against hexavalent chromium. Personal respirators should be checked to ensure they are sized to provide sufficient air to the worker.

All fume control systems should be inspected regularly and maintained to ensure they are performing correctly. Employees also should receive appropriate training in the use of fume removal systems.

Another consideration to reduce exposures to hexavalent chromium is to schedule operations with highest potential exposure at a time when the fewest employees are in the shop.

Areas in which hexavalent chromium has been produced should be cleaned with a HEPAfilter-equipped vacuum, or by wet sweeping or wet scrubbing. Hexavalent chromium contaminated waste must be disposed of properly in sealed plastic bags or other impermeable containers.

Employers are responsible for providing a safe and healthy environment for their employees.