About the symposium

Prospective and Retrospective Environmental Risk Assessment of Mixtures: Moving from Research to Regulation

Chemical-analytical surveys demonstrate over and over again, that organisms in the environment are exposed to complex chemical cocktails. Also chemical products, for example pesticides or surfactants, are usually combination products comprising active ingredients, preservatives, filling agents, etc.. However, the environmental effects of chemicals are traditionally evaluated and regulated on the basis of single substances, chemical by chemical. There seems to be a developing consensus that this approach is not sufficient, especially because the toxicity of a mixture of chemicals is usually higher than each of the individual substances.

In December 2009 the EU environment ministers therefore asked the European Commission to strengthen its work on managing the risks posed by chemical mixtures. In parallel, a range of reviews, guidelines and recommendations on how to assess risks of chemical mixtures have been compiled by academic working groups as well as national, European and international bodies (e.g. WHO or EFSA).

The symposium will present a unique overview and debate on the current state of the art, the open questions and the latest developments with respect to the environmental risk assessment of mixtures. Leading experts from academia, industry, regulatory authorities and NGOs will identify key issues and discuss recommendations for future research and regulation.

Approaches to mixture risk assessment will be discussed from a retrospective as well as a prospective perspective. Retrospective approaches are implemented as Toxicity Identification and Evaluation (TIE) and eco-epidemiological studies. They aim mainly at identifying causes for observed impacts, for example in a polluted river or at a waste disposal site. Prospective studies on the other hand focus on the prediction of mixture toxicities, based on the toxicological or ecotoxicological properties of its components, which is needed for the setting of Predicted No-Effect Concentrations (PNECs) or similar environmental quality endpoints. In both types of studies, the classical mixture concepts of Independent Action (Response Addition) and Concentration (or Dose) Addition play a pivotal role. The concepts are mode of action driven and provide a frame of reference in which to evaluate the joint action of toxicants and are hence also centerpieces in all current regulatory guidelines on mixture toxicities. However, several open questions still remain that will be examined by the symposium speakers. These range from fundamental scientific issues on the applicability of the concepts for various mixture types and exposed organisms, to matters concerning the implementation of the mixture perspective into existing regulatory frameworks and to the development of appropriate environmental quality targets for chemical mixtures. The targeted regulatory frameworks comprise REACH, the Water Framework Directive (WFD), the new PPP regulation 1107/2009 and the biocide directive 98/8/EC.