Hexavalent chromium [Cr(VI)] is one of the valence states (+6) of the element chromium. It is usually produced by an industrial process. Cr(VI) is known to cause cancer. In addition, it targets the respiratory system, kidneys, liver, skin and eyes. OSHA requires employers to determine Cr(VI) exposures to employees. Options for exposure determinations include initial and periodic exposure monitoring.
Chromium metal is added to alloy steel to increase hardenability and corrosion resistance. A major source of worker exposure to Cr(VI) occurs during “hot work” such as welding on stainless steel and other alloy steels containing chromium metal. Cr(VI) compounds may be used as pigments in dyes, paints, inks, and plastics. It also may be used as an anticorrosive agent added to paints, primers, and other surface coatings. The Cr(VI) compound chromic acid is used to electroplate chromium onto metal parts to provide a decorative or protective coating. It is estimated that 558,000 workers are potentially exposed to Cr(VI) in the United States. Workers in a variety of occupations are potentially exposed to Cr(VI). Workplace exposures occur mainly in the following areas:
- Welding/cutting stainless steel and other metals that contain chromium
- Use of pigments, spray paints and coatings
- Operating chrome plating baths
OSHA ID-215 / NIOSH 7605
These methods involve collecting an air sample onto a 5.0-µm polyvinyl chloride (PVC) membrane mounted in a 37-mm or 25-mm polystyrene cassette holder. The recommended flow rate is 2.0 liters per minute for 480 minutes (i.e., 960 liters). NIOSH Analytical Method 7605 is comparable to OSHA Method ID-215. Analysis is performed by ion chromatography with post column derivatization and UV detection. Hexavalent Chromium samples collected on PVC from welding operations do not require field stabilization as with Hexavalent Chromium samples collected from other operations (such as samples collected during chromium plating operations). Hexavalent Chromium samples collected from welding operations must be analyzed within eight days of sampling in accordance with OSHA ID-215 to minimize the effects caused by the interaction of Fe(II) and Hexavalent Chromium to form Cr(III). Storage stability tests showed that these samples were not stable for longer periods of time.
Significant amounts of Hexavalent Chromium are often deposited on the interior walls of the sampling cassettes. Tests showed that Hexavalent Chromium equivalent to 0 to 123% of the amounts found on the PVC filter were present on the interior walls of cassettes. Therefore, it is now routine analytical procedure for the lab analyst to the wipe interior walls of sampling cassettes for all metal samples.
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