Chromate concentration bias in primer paint particles

Area of Science:

• Occupational Health
• Environmental Science
• Materials Science

Background:

• Chromate-containing primer paints prevent metal corrosion but contain hexavalent chromium (Cr6+), a known human carcinogen.
• Understanding Cr6+ distribution in airborne particles is crucial for assessing occupational exposure risks during painting operations.

Purpose of the Study:

• To investigate potential bias in the fraction of chromate within different particle size ranges generated during primer painting.
• To determine if Cr6+ concentration varies significantly with particle size.

Main Methods:

• A solvent-based aviation primer paint was applied using a high-volume, low-pressure spray gun.
• Paint particles were collected and fractionated by size using a seven-stage cascade impactor.
• Cr6+ concentration was quantified per dry weight of paint for each particle size fraction.

Main Results:

• Particles with a mass aerodynamic diameter < 2.0 microm contained significantly less Cr6+ per dry weight compared to particles > 2.0 microm (P < 0.001).
• Median Cr6+ concentration was 18 µg/mg for particles < 2.0 µm and 70 µg/mg for particles > 2.0 µm.
• The overall paint mixture contained 18.75% strontium chromate, equivalent to 67 µg Cr/mg dry paint.

Conclusions:

• Airborne particles generated during primer painting exhibit a size-dependent bias in Cr6+ concentration, with larger particles being more hazardous.
• This size bias may lead to overestimation of chromate emissions when using standard air filters, as larger, more concentrated particles are more easily trapped.
• Findings have implications for occupational safety, exposure monitoring, and the effectiveness of air filtration systems in controlling carcinogenic hexavalent chromium exposure.