Mathematical models are being increasingly used to estimate the concentrations of a wide range of substances in the environment for a variety of reasons, including government control and legislation, and risk and hazard estimation. Exposure assessment has to be performed for many types of substances, including pesticides, industrial chemicals, pollutants, accidental discharges, etc. The interpretation of the results of model equations should always bear in mind the purpose for which the model used was built in the first place. Further, models are always an abstraction of reality, requiring simplifying assumptions to keep the models within the restraints posed by computer performance and/or scientific knowledge.
The present book treats the theme of modelling chemical exposure and risk in terms of four main topics: model characteristics, applications, comparison of estimated with measured concentrations, and modelling credibility.

Lectures.- Pesticide Fate Models and their use. FOCUS Activities.- Models used in the USA for the Evaluation of Pesticide Exposure, Hazard and Risk Assessment.- Quality assurance in environmental modelling.- Possible approaches for pesticides environmental impact management.- Pesticide leaching modelling validation A Recent European Experience.- Evaporation of pure liquids from open surfaces.- Application of USES for estimation of PEC of pesticides and hazard assessment for aquatic environment.- Modelling of operator exposure.- Use of alarm model in accidental pollution of Danube River Case study..- Results of the use of two environmental models for pesticides ranking by hazard.- Recent developments in environmental modelling at Trent University, Canada.- MACRO: a preferential flow model to simulate pesticide leaching and movement to drains.- A scientific and technological framework for evaluating comparative risk in ecological risk assessments.- Comparing two alternative pollutant dispersion models and actual data within an environmental health information Processing System (EHIPS).- RBCA Toolkit: Comprehensive Risk-based modelling system for soil and groundwater clean-up.- Danish EPA use of models for assessment of pesticides mobility.- An optimization model for the control of regional air quality in Europe.- Spatial refinement of regional exposure assessment.- COUNTRY REPORTS.- The future of the environmental modeling in risk assessment in Slovenia Country Report.- Environmental Exposure of Plant Protection Products Portuguese Experience.- Environmental Cleanup Program in Hungary Hungarian Report.- Modelling Experiences in the Slovak Republic Country Report.- Dojransko Ezero (Dojran Lake) Program 1999-2001.- Some Methodological Aspects of Soil Data Receiving AndUse for the Environmental Prognosis Country Report.- Risk Assessment and Risk Management of Industrial Chemicals in Poland Country Report.- Modelling of Environmental Chemical Pollution and Perspectives of Exposure and Risk Assessment In Ukraine National report.- Overview on Environmental Situation in Albania and Some Issues in the Field of "Modelling" Albanian experience.- Conclusions and Recommendations.