Introduction Setting of the Scene, Definitions, and Guide to Volume

The bioavailability of potentially hazardous organic chemicals (persistent organic pollutants, pesticides, biocides, pharmaceuticals, and others) in soil and sediment has a major impact on the environmental and human health risks of these chemicals and is an important area of scientific research. However, this area remains only partially recognized by regulators. Based on the positive experiences from the previous implementation for metals, regulatory frameworks have recently started to include bioavailability within retrospective risk assessment (rRA) and remediation for organic chemicals. In this regard, realistic decision-making in terms of hazard definition and priority setting will ensure the protection of environmental and public health, in contrast to the established approach of using total extractable concentrations, which has been shown to be inappropriate. Moreover, by addressing bioavailability reduction instead of only pollutant removal as a paradigm shift, new remediation strategies become possible. However, the implementation of bioavailability for rRA remains difficult because scientific developments on bioavailability do not always translate into practical approaches for regulators, thus requiring specific measures. For the same reason, bioavailability remains largely unexplored within prospective regulatory frameworks (e.g., REACH, pesticide RA) that address the approval and regulation of organic chemicals.