Chromate Concentration Bias in Primer Paint Particles

Chromate-containing primer paints are used to prevent corrosion on metal surfaces. Chromate contains hexavalent chromium (Cr⁶⁺), a human carcinogen. The objective of this research was to determine if there is a bias in the fraction of chromate found in various particle sizes generated during primer painting operations. A solvent-based, aviation primer paint was sprayed using a high-volume, low-pressure spray gun. Paint particles were collected and separated by size with seven-stage cascade impactors. It was determined that particles with a mass aerodynamic diameter <2.0μm contained significantly less Cr⁶⁺ per dry weight of paint than particles >2.0μm (P<0.001). The median concentration of Cr⁶⁺ in particles <2.0μm is 18μ g of Cr/mg of dry paint and the median concentration for particles >2.0μm is 70μg of Cr/mg of dry paint. The mixed paint contains 18.75% strontium chromate, which equates to a ratio of 67μg of Cr/mg of dry paint. Particles >2.0μm are more likely to impact in the upper tracheobronchial regions of the lung where mucociliary clearance is relatively rapid. Additionally, chromate emissions from spraying operations may be overestimated because larger particles, which are more easily trapped on an air filter, contain more chromate than the smaller particles, which are more likely to bypass an air filter.