Workshop debates significance of bound residues in environmental risk assessment

ECETOC held a 2-day workshop .... in Brussels .... to further this debate and to develop guidance on how to account for bound residues and bioavailability in environmental risk assessment.

Bound residues, including non-extractable residues, are an important factor in PBT assessment and the risk assessment of chemicals. Precautionary risk assessments usually assume 100% bioavailability i.e. all of the chemical present is available, for degradation or to have potential toxic effects on the biota. This precautionary approach generally overestimates the exposure concentration by the amount that is not available and therefore overestimates the level of risk to biota in the environment. Although it is a position that has been recognised and referenced by REACH (2008) and OECD test guidance (2002), there is no agreed guidance on how to determine what is available and what is not, and how information on bound residues should be interpreted in the risk assessment. As a result, it continues to be debated from a scientific and regulatory point of view.

ECETOC held a 2-day workshop attended by 38 stakeholders representative of industry, academia and regulatory authorities from the USA, Canada, Europe and Asia in Brussels on 21-22 October to further this debate and to develop guidance on how to account for bound residues and bioavailability in environmental risk assessment. The conclusions, future regulatory and research needs and a framework outlining a possible approach for advancing and improving the risk assessment of bound residues will shortly be published in Workshop Report No. 17.