The particle size distribution and speciation of chromium in paint spray aerosol

Workplace exposures to hexavalent chromium [Cr(VI)], a human carcinogen, are significant in spraying operations of chromate-containing paints. This research sought to clarify issues related to the analysis of Cr(VI) in paint samples, to assess the size distribution and speciation of chromium (Cr) in the field, and to evaluate the effect of spray application parameters on paint aerosol size distribution. Accurate determination of Cr(VI) in paint aerosol air samples is important in assessing a worker's exposure to Cr(VI). The efficiency of a widely used procedure published in National Institute of Occupational Safety and Health method 7604 at extracting Cr(VI) from paint samples was determined. This extraction was historically validated for paint samples containing 24.5 to 61.5 μg of Cr(VI). Actual Cr(VI) mass in paint samples collected in industrial settings may be greater than 61.5 μg. Paint samples containing 250 to 3000 μg of Cr(VI) were extracted and analyzed for Cr(VI) and total Cr. A significant decrease in Cr(VI) extraction efficiency was determined for samples containing more than 1000 μg of Cr(VI). Cr(VI) was stable in refrigerated samples and in paint cans.; Field studies were conducted to determine the size distribution and speciation of Cr in paint spray aerosol using personal cascade impactors. The Cr(VI) size distributions had a mean MMD of 15 μm. Cr in the paint aerosol was essentially in the Cr(VI) form. Particles larger than 10 μm accounted for most of the aerosol mass. Cr(VI) in paint spray aerosol was estimated to deposit mostly in the head airways of the respiratory system. This could explain the cases of the upper respiratory cancer reported in the literature among spray painters, and the weak or negative associations reported in epidemiologic studies between lung cancer and paint spraying.; The size distribution of paint spray aerosol generated in a laboratory-based miniature spray paint booth had a MMD ranging from 4.2 to 9.6 μm. Particle bounce inside the cascade impactor did not affect particle size distribution. Bounceback spray generated smaller particles than direct spray. Aerosol aging had no effect on size distribution. Gun atomization pressure and aerosol size were inversely related.