Pursuant to a court order, OSHA issued a final rule on February 28, 2006 that addresses occupational exposure to hexavalent chromium (Cr[VI]). OSHA determined that the Cr(VI) rule is necessary to reduce significant health risks due to Cr(VI) exposure. Certain Cr(VI) compounds have been found to cause lung cancer and nasal cancer in humans. Inhaling relatively high concentrations of Cr(VI) can also cause a wide range of other health effects (such as runny nose, sneezing, itching, nosebleeds, ulcers, and holes in the nasal septum). Ingestion of very high doses of Cr(VI) can cause kidney and liver damage, nausea, irritation of the gastrointestinal tract, stomach ulcers, convulsions, and death. Dermal exposures may cause skin ulcers or allergic reactions.
Activities that have the potential for Cr(VI) exposure include the following:
Production and use of chromium metal and chromium metal alloys
Chromium electroplating
Welding of metals containing chromium such as stainless steel or other high chromium steels, or chromium coatings
Production and use of Cr(VI)-containing compounds (such as Cr[VI] pigments, Cr(VI) catalysts, and chromic acid)
Production of chromium-containing pesticides
Painting activities involving the application of strontium chromate coatings to aerospace parts
Removal of lead chromate
According to OSHA, there are a total of 380,000 workers exposed to Cr(VI). However, welders represent nearly half of the workers covered by OSHA's hexavalent standard.
This paper summarizes major provisions of OSHA's Cr(VI) standards, the nature of Cr(VI) in welding fumes, common welding processes and fume generation rates, factors for Cr(VI) exposure from welding, exposure monitoring strategies, and considerations for feasible engineering controls.
OSHA issued separate but similar standards for general industry, construction, and shipyard sectors. The major provisions of the final rule for controlling Cr(VI) exposure are summarized in Table 1.
(Table in full paper)
Chromium has been used commercially in the U.S. for more than 100 years. Chromium occurs mainly in three forms, described by its valence state. Metallic chromium (Cr[0]) is a steel-gray solid with a high melting point that is used to make steel and other alloys. Chromium metal does not occur naturally but is produced from chrome ore. Trivalent chromium (Cr[III]) occurs naturally in rocks, soil, plants, animals, and volcanic emissions. Cr(III) is used industrially as brick lining for high-temperature industrial furnaces and to make metals, metal alloys, and chemical compounds. Cr(VI) occurs through the oxidation of chromium compounds with lower valence states. Cr(VI) is considered the greatest occupational and environmental health concern, as it is the most toxic. Other valence states are unstable so they are less common. They will most likely be quickly converted to either Cr(III) or Cr(VI).
Chromium metal is found in stainless steel and many low-alloy materials, electrodes, and filler materials. The chromium that is present in electrodes, welding wires, and base materials is in the form of Cr(0). Therefore, welders do not ordinarily work with materials containing Cr(VI).
