Human and Ecological Risk Assessment of Contaminated Sites – Key Knowledge Gaps and Implication to Soil Remediation.

Since the inception of the Industrial Revolution, human activities have substantially accelerated the cycling of contaminants in the environment. This has resulted in a large number of contaminated sites worldwide. Environmental legislation dealing with risk assessment and remediation has been traditionally based on total contaminant concentrations. The main cause for this pragmatic approach has been related to knowledge gaps in human and ecological risk assessment. Here we discuss a number of important gaps, namely contaminant bioavailability, mixed contaminant ecotoxicology and emerging contaminants. The concept of bioavailability has gained significant acceptance but its implementation into the terrestrial regulatory framework is still hindered by the limited availability of validated methodologies. While in the case of lead and arsenic human risk assessment the state-of-the-art is such that bioavailability-based risk assessment will be incorporated in the near future into legislation, the situation for other inorganic and organic contaminants is still far from being resolved. The second key knowledge gap is related to mixture of contaminants. While contaminant mixtures represent the norm in real case scenarios, environmental legislations are generally based on individual contaminants. These knowledge gaps also apply to the area of emerging contaminants that in itself is challenging in terms of human and ecological risk assessment.