Environmental impact of metal and metalloid leaching from highway marking glass beads

Recently, metals and metalloids have been observed at elevated concentrations in glass beads imported to the US. Average total concentrations in imported batches ranged from 103 to 683 mg kg^-1 for As, 62 to 187 mg kg^-1 for Sb, and 23 to 179 mg kg^-1 for Pb. The labile fraction associated with the glass beads resulted in leached concentrations as great as 538 μg L^-1 for As, 1092 μg L^-1 for Pb, and 160 μg L^-1 for Sb. Sequential extraction was conducted as well to better understand the form of metals and metalloids associated with the glass beads. Only 0.23% of As, 3.40% of Pb, 2.37% of Ba, and 1.92% of Mn were extracted in the exchangeable (As, Mn, and Ba) and the oxidizable forms (Pb), whereas greater than 97% of metals and metalloids present were associated with the glass matrix. Nonparametric statistics were applied to test total concentrations that resulted in exceedances in the groundwater quality criteria. Results demonstrated that the As, Pb, and Sb limits were exceeded for 98%, 58%, and 15% of the samples tested respectively suggesting a potential environmental impact to groundwater used as a drinking water source.