The efficiency of alkaline extraction for the recovery of hexavalent chromium (CrVI) from paint samples and the effect of sample storage on CrVI recovery.

Workplace exposures to CrVI, a human carcinogen, are significant in spraying operations of chromate-containing paints. Accurate determination of CrVI in paint aerosol air samples is important in assessing a worker's exposure to CrVI. National Institute for Occupational Safety and Health method 7604 is widely used for determining CrVI in air samples. It utilizes an alkaline extraction procedure. It was historically validated for paint aerosol samples containing 24.5 to 61.5 microg of CrVI. The literature documented potential airborne CrVI exposures greater than 61.5 microg in recent paint spraying operations. The efficiency of the alkaline method at extracting CrVI from paint samples containing 250 to 3000 microg of CrVI was determined. Paint was prepared, sampled, extracted twice and then digested. Extracts were analyzed for CrVI and digestates of the residual Cr were analyzed for total Cr. Alkaline extraction of paint samples using NIOSH method 7604 resulted in quantitative recoveries for paint samples with CrVI filter loadings from 250 to 3000 microg. A decrease in CrVI extraction efficiency was observed in samples containing > 1000 microg of CrVI. A second extraction improved the recovery of CrVI in these samples. Refrigerating paint aerosol samples for up to 2 weeks did not affect their CrVI content.