Pavement Sealant Leaches Environmental Contaminants

Published October 18, 2022

Coal tar pavement sealant contains 50,000 to 75,000 ppm of carcinogenic polycyclic aromatic hydrocarbons (PAHs). Weathering by sunlight and rain can contaminate natural waterways through oxidation of the PAHs contained in the pavement sealant.

Taylor Glattke, MagLab

New research shows that high concentrations of polycyclic aromatic hydrocarbons (PAHs) found in coal tar pavement sealants are oxidized into toxic, water-soluble compounds by sunlight and subsequently washed into the environment by rainwater, polluting natural water systems, negatively impacting marine ecosystems and public health.

What did scientists discover?

Laboratory simulated weathering of coal tar pavement sealant revealed that carcinogenic polycyclic aromatic hydrocarbons (PAHs) are oxidized by sunlight into oxy-PAHs and then transferred into water. Toxicity testing of water that contained oxy-PAHs revealed high toxicity of water fractions collected from coal tar sealant.

Why is this important?

Little has been known about how pavement sealant is transformed when it is exposed to weathering, such as sunlight and rain. This new research reveals that toxic compounds in coal tar sealant can easily leach into and pollute natural water systems, thus negatively impacting marine ecosystems and public health. These new findings provide critical evidence to support phasing out of these materials in the United States and elsewhere.

Who did the research?

Taylor J. Glattke^1,2, Martha L. Chacón-Patiño², Sarajeen Saima Hoque³, Thomas E. Ennis⁴, Steven Greason⁵, Alan G. Marshall^1,2, Ryan P. Rodgers^1,2

¹Ion Cyclotron Resonance Program, National MagLab ²Department of Chemistry and Biochemistry, Florida State University ³Department of Civil & Environmental Engineering, FAMU-FSU College of Engineering ⁴Watershed Protection Department, City of Austin, TX ⁵Sitelab Corporation

Why did they need the MagLab?

The MagLab's ultrahigh-resolution FT-ICR (Fourier Transform - Ion Cyclotron Resonance) mass spectrometers allow for identification of tens of thousands of compounds from complex mixtures, such as the weathered coal tar sealant and water samples analyzed in this work.