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

Abstract

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