Modelling Environmental Exposure to Transformation Products of Organic Chemicals

Abstract

Transformation products of environmental contaminants are likely to contribute significantly to the overall chemical pressure on valuable environmental resources. However, the whole extent of this so far often over-looked additional contamination remains unclear because the number of monitoring studies addressing transformation products is currently small and they are largely focused on well-known pesticide transformation products. Environmental fate modelling of transformation products opens up the possibility to predict the likely presence of environmental transformation products in environmental compartments of interest and to point towards new, potentially relevant transformation products. Whereas, depending on their purpose, there are different types of fate models for transformation products, this chapter will focus on multispecies multimedia models because of their general applicability to various tasks in chemical risk assessment and quality assessment of environmental resources. The chapter will introduce the mathematical framework underlying most multispecies multimedia models and discuss its application to three examples. These examples include the extension of overall persistence to include transformation products, the assessment of the long-range transport potential of persistent transformation products of semivolatile organic compounds, and the prediction of relative concentrations of pesticide transformation products in surface water bodies. The second part of the chapter discusses data requirements and availability for multispecies multimedia models and sheds some light on the accuracy of frequently used chemical property estimation tools. Lastly, tools to predict transformation schemes in those cases where no information on possible transformation products is available are introduced and their current limitations are discussed.