Screening level assessment of arsenic and lead concentrations in glass beads used in pavement markings

Retroreflective glass beads used in pavement markings are a critical component of highway safety. Glass beads meeting American Association of State Highway and Transportation Officials (AASHTO) M247 specifications are the current industry standard. AASHTO M247 glass beads are fabricated using reclaimed glass cullet, offering cost effective performance while beneficially reusing sources of industrial and commercial waste glass. However, reclaimed glass cullet may contain elevated levels of arsenic and lead that can be passed through to the final product. Concern regarding the presence of arsenic and lead in retroreflective glass bead products within the U.S. marketplace resulted in recently adopted legislation that sets a 200 part-per-million (ppm = 106 x massmetal/massbeads) limit for both arsenic and lead for beads used on United States roadways. While the scientific justification for the 200 ppm limit is not immediately clear, the proposed legislation is regarded as a good-faith attempt to limit the risk associated with the presence of arsenic and lead in the beads. This research developed a preliminary understanding of the risk associated with the presence of arsenic and lead in glass beads used in pavement marking systems to support decisionmaking. Researchers tested 15 samples of commercially available glass beads in current use on U.S. roadways from State transportation department stockpiles.