On February 28, 2006, OSHA issued a final ruling on the occupational exposure to Hexavalent Chromium [Cr(VI)]. OSHA determined that the new ruling was necessary to reduce severe health risks due to Cr(VI) exposure. Certain compounds found in Cr(VI) are known to cause nasal and lung cancer in humans. Ingestion of high doses of Cr(VI) can cause kidney and liver damage, while inhaling Cr(VI) in high concentration can cause a variety of health concerns. Inhaling Cr(VI) can affect your body and cause nosebleeds, runny nose, itching, and ulcers, among other symptoms. High exposures to the skin may have effects like skin ulcers and/or allergic reactions.
Activities for Cr(VI) exposure include the production and use of chromium metal and chromium metal alloys, electroplating, welding of materials containing chromium, production, and use of Cr(VI) containing compounds, production of chromium containing pesticides, painting activities involving the application of strontium chromate coating to aerospace parts.
According to OSHA, a total of 380,000 workers are exposed to Cr(VI). Only half of those exposures are from welding operations.
Cr(VI) in Welding Fumes
Chromium has been used commercially in the US for more than 100 years. It occurs mainly in three forms: Metallic chromium Cr(0), Trivalent chromium Cr(III) and Hexavalent chromium Cr(VI), the most toxic. Chromium metal is found in stainless steel and several grades of low alloy materials.
Welding fume is a mixture of metal oxides. Chromium is not intentionally added to mild steels or mild steel consumables, but due to the use to scrap steel in the production process, some low levels of chromium may be present. In most mild steel welding, the exposure limits for manganese will be exceeded prior to the PEL for Cr(VI) is reached. (Fiore, 2006)
Exposure Monitoring
OSHA requires that all employers that have employees who work with Cr(VI) determine the exposure to the employees. This is done by testing the employees initially and periodically. The exposure test will need to be conducted in a similar environment and for the usual duration in which the employee regularly performs his work so as to closely resemble normal working conditions. Exposure monitoring will be done initially, every three (3) months if > 5 µg/m3 PEL (permissible exposure limit), and every six (6) months if > 2.5 µg/m3 AL (action level). The monitoring can be discontinued if the exposure is below the action level.
Exposure Factors:
Employee Notification
For general industry, results of the exposure must be posted, or each affected employee must be notified in writing, within the required fifteen (15) working days. The notification must describe the corrective actions that are going to be taken. For construction, results of the exposure must be posted, or each affected employee must be notified in writing, within the required five (5) working days. The notification must describe the corrective actions that are going to be taken.
Best Practices and Controls
Eliminating or minimizing the potential exposure by substituting with materials that generate fewer Cr(VI) fumes should be the first consideration for engineering controls. Another way to lower exposure to our workforce is the use of automatic and mechanized equipment. This places the worker further away from the operation and breathing zone. However, this may not be a viable solution in many situations, such as construction operations. In a factory setting or fabrication shop local exhaust ventilation systems are great methods of engineering control to reduce the Cr(VI) exposure. There are also portable fume extraction units, high-volume and low-vacuum systems. These units have a few advantages: they are available in many sizes, have quick set up times and offer lower cost compared to a permanent exhaust system. The last line of protection would be the use of respirators.
Also, note that welding outdoors does not guarantee that welding fume and Cr(VI) exposure levels will be below the occupation exposure limits. General/dilution ventilation and natural ventilation have limited effectiveness if they cause the welding plume to travel through the welder's breathing zone.
References:
Jerome Spear, M.B.A, CSP, CIH "Welding Safety" article published in the Professional Safety Magazine
Fiore, S. (2006). Reducing exposure to hexavalent chromium in welding fumes. Welding Journal, 85(8), 32-42.