Abstract

Several laboratory models exist for assessing the amount of lead that is released from soil and available for absorption by the gastrointestinal tract of children. Both the static in vitro digestion model (IVD) of the National Institute for Public Health and Environment (RIVM) and the dynamic Tiny-Tim model of the Netherlands Organisation for Applied Scientific Research (TNO) mimic the physiological conditions of the gastrointestinal tract of a child. However, the IVD model estimates a higher risk than the Tiny-Tim model. Exposure to too high levels of lead poses a particular health risk to children, one of which is a negative impact on IQ development. The soil in the historical inner (city) areas of many Dutch cities and villages is often polluted with lead. This lead originates from several sources, including the accumulation of lead-containing waste products and building rubble associated with centuries of urban development and industrial activities. This has resulted in a rubble layer that is referred to as made ground. Made grounds from different sources appear to have rather uniform soil characteristics, despite differences in the original soil lithology (clay, sand, loess). Possibly because of this uniformity, no relation has been observed between the release of lead from made grounds and soil characteristics. Results obtained using the IVD model, however, do indicate a qualitative relation between lead mineralogy and the release of lead from made grounds. The results of prior comparisons of the IVD and Tiny-TIM models using human and animal data are in close agreement. To obtain a definitive answer on the usability of these models in risk assessment, however, the RIVM recommends that additional validation tests be run using relevant human or animal data. This report offers policy-makers useful information on how to deal with lead bioavailability in the soil which allows a more precise risk assessment.