Herziening interventiewaarde lood; evaluatie van de afleiding van de interventiewaarde grond/sediment en grondwater

This report documents the important aspects in deriving the intervention values for lead (Pb) for soil/sediment and groundwater as part of a current ongoing running evaluation of existing intervention values. Reported for lead are the physical-chemical properties, the ecotoxicological serious soil-contamination concentration (ECOTOX SCC), the human toxicological Maximal Tolerable Risk (human MTR), human toxicological serious soil contamination concentration (HUM-TOX SCC) and proposals for the intervention value for soil and groundwater. It is recommended to use an equation derived for field soils (with pH, organic matter and clay content)for the soil type correction of the intervention values derived. If it is decided to use only the organic-matter and clay content, we advise proceeding with the current correction of Van den Berg/Roels. Based on the current toxicological information, ECOTOX SCC is recalculated with the current soil type correction (490 mg/kg d.m.) and the proposed soil type correction with pH (450 mg/kg d.m.). If it is decided to use the 'added risk-approach', the ECOTOX SCC for lead will be 575 and 535 mg/kg d.m., respectively. The ECOTOX SCC calculated for sediments is much higher (64.000 mg/kg d.m.).The human-toxicological maximal tolerable risk (human MTR) is maintained at 3.6 microg/kg b.w./day, which is also supported by the World Health Organisation (WHO). The human exposure to lead is mainly determined by the ingestion of soil particles, the intake of contaminated crops and the bioavailability of lead from soil in the human body. Prior to completing the research on bioavailability in the human body, a relative bioavailability factor for lead in soil of 0.6 was deduced. An average of 100 mg of soil per day is proposed for soil ingestion by children (1 to 6), instead of the current 150 mg per day. The average crop consumption can be slightly reduced. If it is decided to use a general background, the background exposure for lead is estimated to be 25% of the human MTR. The recalculated HUMTOX EBVC is found between 450 and 670 mg/kg, depending on the choices made and the extent to which new data are used. Integration of the HUMTOX SCC value with that of ECOTOX SCC leads to a proposal for the intervention value soil/sediment of 450-575 mg/kg d.m. and 32-41 microg/l for groundwater