The main objective of the book is to contribute to the existing knowledge and practical application of modern technologies for exposure and risk assessment of chemical environmental pollution with emphasis on methodologies and the models used for environmental security. Particular attention is paid to models useful for the quantitative and qualitative identification, estimation of exposure and risk. Stress is given to the computational modelling technology achievements for environmental fate, exposure, hazard, and risk assessment of chemical pollutants in air, water, soil and biota; to the estimation of the screening level risk assessment modelling to assess and prioritize chemicals; to the evaluation of the probabilistic risk assessment methods for intentional pollution to help the risk managers in uncontrollable processes; to the review of the approaches for modelling of adverse health and environmental effects; to the comparative evaluation of currently used models on the criteria of sensitivity, variability and uncertainty; to the evaluation of the additional criteria as predictive value, advantages, validations and limitations of models. Research needs in this complex scientific field are identified and the strategy for prediction and prevention of chemical threats originating from intentional pollution are outlined.