Annex V — PHASES AND PRINCIPLES FOR SITE-SPECIFIC RISK ASSESSMENT

1. Characterisation of the contamination requires identifying the nature of the contaminants (e.g. heavy metals, organic contaminants, etc.) present at the site and determining their source, concentration, chemical form, and distribution in the soil, parent material and groundwater. The presence and concentration of contaminants in the different media is determined through sampling and investigation on-site and off-site in the event that a transfer of contaminants is suspected. Contaminants associated with potentially contaminating activities shall be sampled in the relevant media on the basis of the environmental context and the physico-chemical properties of the contaminants that influence their behaviour in the environment. Natural and anthropogenic background levels shall be considered. 2. Exposure assessment requires identifying the path by which soil contaminants may reach receptors. Exposure pathways can include inhalation, ingestion, dermal contact, plant uptake, migration to groundwater or others. The concentrations of the contaminants in the exposure media are combined with exposure parameters (e.g. frequency and duration of exposure, soil ingestion rate, etc.) and receptor characteristics such as age, gender, and health status to estimate the daily exposure dose. The source-pathway-receptor linkages are summarised in a graphic, schematic and simplified representation (the conceptual site model). Exposure may be assessed through direct analysis at the point of exposure or by modelling the transfer of a contaminant to the medium of exposure. 3. Toxicity or hazard assessment involves the evaluation of the potential adverse effects of the contaminants on human health and the environment, based on the dose and duration of exposure. Toxicity or hazard assessment takes into account the inherent toxicity of the contaminants and the susceptibility of different exposed receptors (humans and ecosystems), such as animals, micro-organisms, plants, children, pregnant women, the elderly, etc. The toxicological information is used to estimate reference doses or concentrations, which are used for the risk characterisation. 4. Risk characterisation requires integrating the information from the previous steps to estimate the magnitude and probability of adverse effects of the contaminated site on human health and the environment, including from migration of the contamination to other environmental media. The risk characterisation helps to assess and prioritise the need for risk reduction measures and remediation measures, and to ensure that the condition of the soil is compatible with the current and planned land use. It can also help to establish soil remediation or management objectives for a site, e.g. to achieve maximum acceptable limits or site-specific risk-based screening values. Risk assessment involves a large number of hypotheses and uncertainties. It is therefore essential to evaluate those hypotheses and uncertainties to fully understand the significance of the results obtained and to make well-informed decisions.