Hexavalent Chromium Dissociation from Overspray Particles into Fluid for Three Aircraft Primers

DOD and industry use chromate-containing primers extensively to inhibit corrosion on metal assets. Chromate contains Cr6+, a human carcinogen, but there is little epidemiological evidence of increased lung cancer among spray painters. Using bio-aerosol impingers, overspray particles from three primers (solvent-borne epoxy, water-borne epoxy, and solvent-borne polyurethane) were collected into water to test the hypothesis that the paint matrix inhibits Cr6+ release into water, under the premise that this simulates Cr6+ release from particles into lung fluid. Particles were allowed to reside in water for 1 or 24 hours, then separated from the water by centrifugation, and the water tested for Cr6+. The mean fractions of Cr6+ released into the water after 1 and 24 hours for each primer (95% confidence) were: 70 5% and 85 5% (solvent epoxy), 74 4% and 84 4% (water epoxy), and 94 3% and 95 2% (polyurethane). Solvent and water epoxy primer 24-hour Cr6+ release ranged from 100% dissociation to 33% and 48%, respectively. Correlations between Cr6+ distribution with particle size and % Cr6+ dissociated from each sample indicate that particles \u3c 5 mm release a larger fraction of Cr6+ during the first 24 hours vs. particles \u3e 5 micrometers