Appendix II: Industry Operations or Processes Associated with Occupational Exposure to Cr(VI) This appendix identifies industry operations or processes associated with occupational exposure to Cr(VI). For each of these sectors, a brief description of potential sources of Cr(VI) exposure is presented. ELECTROPLATING Exposures to Cr(VI) can occur in hard chrome plating, decorative chrome plating, and anodizing operations. Cr(VI) exposures can also occur in chromium conversion coating operations. Chromium conversion is not an electroplating process but often takes place in electroplating shops. Employee exposures to Cr(VI) during chrome electroplating and chromium conversion coating operations occur as a result of the formation of chromatecontaining mists and aerosols that are released from the chromate/chromic acid bath. Mists and aerosols containing Cr(VI) are released from hydrogen bubbles that form and burst during the electroplating process. They may also be released when platers add or remove parts from the bath. Helpers may also be exposed to Cr(VI) when adding chemical agents to the bath or when disposing of chromate-containing wastewater.
the composition of the filler metal, flux material or shielding gas used, which can affect the amount of fume generated. Other factors can also influence the amount of fume generated. For example, increasing the welding current and voltage tend to increase the amount of welding fume generated. In carbon steel welding, most exposures to Cr(VI) are usually well below the PEL due to the low percentage of chromium metal in carbon steel. Ninety percent (90%) of the carbon steel produced has only trace amounts of chromium. Ten percent (10%) of the carbon steel produced contains up to 3% chromium. Carbon steel welders in confined spaces may experience elevated Cr(VI) exposures, though most exposures will be below the PEL.
WELDING Exposures to Cr(VI) can occur when welding or cutting operations are performed on stainless steel, other metals containing Cr(VI), or surfaces coated with Cr(VI) paint. Welding on carbon steel in confined or enclosed spaces may also result in Cr(VI) exposures. Employee exposure to Cr(VI) is expected to increase as the chromium content of the base material increases. Therefore, one would expect that exposures would tend to be higher for welding on stainless steel (10 to 24% chromium) versus welding on carbon steel (generally 3% chromium or less). However, there are other factors that can greatly affect exposures to Cr(VI) during welding operations. These factors include: the type of welding process used [Flux Cored Arc Welding (FCAW), Shielded Metal Arc Welding (SMAW), and Gas Metal Arc Welding (GMAW) generate the highest fume levels while Tungsten Inert Gas (TIG) and Submerged Arc Welding (SAW) generate lower levels]; the environment where welding is taking place (exposures are lower in open spaces versus confined or other enclosed spaces); and
Welding a stanchion (Photo courtesy of Bath Iron Works).
PAINTING Paints and coatings that contain Cr(VI) are applied to a wide variety of structures and products. Cr(VI) paints and coatings are also removed from structures and products in many situations. Both of these scenarios may result in employee exposure to Cr(VI). Aerospace In the aerospace industry, employees may be exposed to Cr(VI) during painting of aircraft (exterior or interior) or aircraft parts, and during removal of chromatebased coatings. The primary Cr(VI)-containing product used is strontium chromate primer, which is used as a corrosion inhibitor on metal surfaces (particularly alu-
40 Occupational Safety and Health Administration