Hex chrome hazards
April 8, 2006
For workers in the welding industry, the new lower OSHA permissible exposure limit (PEL) for hexavalent chromium should be good news. â€œHex chrome,â€ a known human carcinogen, can be produced when welding on stainless steel or some painted surfaces. OSHAâ€™s new standard, published Feb. 28 as a result of a court order, reduces the PEL tenfold, from 52 to five micrograms of chromium per cubic meter of air as an eight-hour time-weighted average. The rule becomes effective on May 30.
Despite the lower limit, welders will still need to keep their guard up against exposure to hexavalent chromium (Cr(VI)). The rule will allow exposures five times higher than OSHA had initially proposed in 2004, and 20 times as high as the level that had been sought by activists who filed a lawsuit to force the agency to set a new standard. By OSHAâ€™s own estimates, 10 to 45 lung cancer deaths overall will occur per 1,000 workers over a lifetime at the five micrograms per cubic meter level.
Fume inhalationChromium fume, including hexavalent chromium, is created by welding or cutting on stainless steel or metals that are coated with a chromium material. The fume can be inhaled, and without adequate control measures welding on stainless steel can lead to exposure well above the legal limit, the California Department of Health Services (CDHS) reports.
The composition of the base metals, the welding materials used, and the welding processes affect the specific compounds and concentrations found in the welding fume, according to the American Welding Society.
Major health effects associated with exposure to hex chrome include lung cancer, nasal septum ulcerations and perforations, skin ulcerations, and allergic and irritant contact dermatitis. Overexposure can also cause symptoms such as nausea, headaches, dizziness and respiratory irritation.
Take controlThe two best ways to prevent inhaling or ingesting chromium-containing particles, reports CDHS, are substituting chromium-free materials and using local exhaust ventilation. If a substitute cannot be found, a mechanically powered local exhaust hood should be placed at the point where chromium is released into the air, or the entire process should be contained within the hood. Properly designed and maintained local exhaust ventilation draws off most of the chromium before it can be inhaled.
Wearing an air-purifying respirator such as a paper mask or rubber mask with screw-in filters is a less effective way to control exposure, CDHS reports. In fact, the Cal/OSHA respirator standard allows respirator use to prevent overexposure only as a last resort. This is because the use of respirators is complex and prone to error, often resulting in inadequate protection.
If using a respirator, according to CDHS, it must be approved for the type of particles in the air. For example, a paper dust mask designed for removing powder particles will not remove the fume particles created by welding. The respirator must also be fit-tested, and workers should be medically examined for their ability to wear a respirator. Even when these requirements are met, leakage of contaminated air into the respirator may still occur.
In summary, even with the lower PEL, welders must still respect the dangers of hex chrome exposure.
SIDEBAR: How welders can guard against overexposure
Source: American Welding Society