The risk of overestimating the risk-metal leaching to groundwater near contaminated glass waste deposits and exposure via drinking water

This study investigates metal contamination patterns and exposure to Sb, As, Ba, Cd and Pb via intake of drinking water in a region in southeastern Sweden where the production of artistic glass has resulted in a large number of contaminated sites. Despite high total concentrations of metals in soil and groundwater at the glassworks sites properties, all drinking water samples from households with private wells, located at a 30–640 m distance from a glassworks site, were below drinking water criteria from the WHO for Sb, As, Ba and Cd. A few drinking water samples showed concentrations of Pb above the WHO guideline, but As was the only element found in concentrations that could result in human exposure near toxicological reference values. An efficient retention of metals in the natural soil close to the source areas, which results in a moderate impact on local drinking water, is implied. Firstly, by the lack of significant difference in metal concentrations when comparing households located upstream and downstream of the main waste deposits, and secondly, by the lack of correlation between the metal concentration in drinking water and distance to the nearest glassworks site. However, elevated Pb and Cd concentrations in drinking water around glassworks sites when compared to regional groundwater indicate that diffuse contamination of the soils found outside the glassworks properties, and not only the glass waste landfills, may have a significant impact on groundwater quality. We further demonstrate that different mobilization patterns apply to different metals. Regarding the need to use reliable data to assess drinking water contamination and human exposure, we finally show that the conservative modelling approaches that are frequently used in routine risk assessments may result in exposure estimates many times higher than those based on measured concentrations in the drinking water that is actually being used for consumption.