This metal can exist in several different forms. When chromium is listed on a Material Safety Data Sheet for a filler metal or base metal it is usually referring to trivalent chromium. We are not as concerned about chromium in this form from a welder’s health standpoint as we are about hexavalent chromium. When hot work such as welding, plasma cutting, or carbon arc cutting is performed on metal containing trivalent chromium some of it is changed to hexavalent chromium, a more harmful form of the metal.
Many, but not all, Hardfacing filler metals contain significant amounts of chromium. OSHA has established a Permissible Exposure Limit (PEL) for hexavalent chromium which is 5 micrograms per cubic meter of air and an Action Level of 2.5 micrograms per cubic meter of air. The PEL and Action Level are based on an 8-hour time weighted average, and are a very low concentration. When these levels are exceeded there are specific requirements in the standard which the employer must follow. See Federal OSHA’s hexavalent chromium standard at 29 CFR 1910 or refer to your state OSHA website.
To better understand the Permissible Exposure Limit, imagine a 27 story warehouse with the floor dimensions of a football field. Now, take a piece of hexavalent chromium equal to the weight of a dime, grind it to a fine powder and spread it evenly throughout the air in the warehouse; the resulting concentration is approximately equal to the OSHA permissible exposure limit of 5 micrograms per cubic meter of air. This gives us a much better idea as to the exposure level to this metal which can have serious health effects on those who are overexposed.
Due to this low exposure limit it is prudent to use local exhaust ventilation during all weld applications involving metals containing significant amounts of chromium to maintain the welder’s exposure to below the OSHA Action Level.
Kevin Sayler, CIH is a health and safety consultant who helps businesses increase profitability by reducing costs associated with workplace accidents, injuries and diseases. He specializes in the prevention of harmful exposures to employees.