Chromate dissociation from three types of paint particles

Chromate-containing primer paints are used to inhibit corrosion on metal surfaces. Though chromate contains hexavalent chromium (Cr(6+)), a human carcinogen, there is little epidemiological evidence of increased lung cancer among spray painters. One reason may be that the paint matrix hinders the release of Cr(6+) from the paint particle during the time that the particle is within the lungs. This study measures the mass of Cr(6+) released from particles originating from three types of paint particles: solvent-borne epoxy, water-borne epoxy, and polyurethane. Impingers were used to collect paint particles into water and particles were held in the water at rest for 1 and 24 h residence times. Particles were then separated from the water by centrifugation. The supernatant was tested for dissolved Cr(6+), which was compared to the total Cr(6+) (dissolved Cr(6+) plus Cr(6+) in particles). The mean fractions of Cr(6+) released into the water after 1 and 24 hours for each primer averaged: 70 and 85 (solvent epoxy), 74 and 84% (water epoxy), and 94 and 95% (polyurethane). Correlations between particle size and the fraction of Cr(6+) released indicate that smaller particles (<5 microm) release a larger fraction of Cr(6+) versus larger particles (>5 microm).