AN INVESTIGATION OF ROAD PAINT CHEMISTRY: AN UNRECOGNIZED SOURCE OF HEAVY METAL POLLUTION IN TERRE HAUTE, IN

Exposure to heavy metal pollutants remains a public health concern in urban areas. Because road paint is ubiquitous in these environments, these painted surfaces could be an important source of heavy metal pollution within communities. To investigate road paint as a potential source of heavy metals, this study characterizes paint samples from Terre Haute, IN.

Sixteen road paint samples collected for this study represent a broad spectrum of paint types. This includes different colors, textures, locations (centerline vs. curbs), as well as samples from streets with different traffic volumes. The bulk chemistry of each sample was determined using X-ray Fluorescence (XRF), which revealed that ~56% of the samples have elevated Pb, Cr, Cu, and Zn concentrations. Samples with elevated concentrations of Pb, Cr, and Zn are correlated with busier streets and industrial areas. These samples also exhibited dull colors and weathered surface textures, suggesting that they are older. The presence of Pb and Cr may indicate the use of Crocoite (PbCrO₄) as a yellow pigment. Approximately 38% of the samples contained elevated Zn concentrations, which may have been added to the paint formula to increase durability. Additionally, elevated SiO₂ concentrations were observed in some samples, indicating the presence of reflective glass spheres or as an additive to reduce surface weathering.

Although this study identified road paint as a potential source of heavy metals, future investigations will include SEM/EDS analyses to better characterize surface textures, weathering profiles, and the spatial relationships between Pb, Cr, and Zn within paint samples.