Environmental toxicology is an interdisciplinary science, which integrates biology, microbiology, chemistry, engineering, environmental sciences, ecology and other sciences. Assessment of the environmental effects of chemicals is complicated as it depends on the organisms tested and involves not only the toxicity of individual chemicals, but also their interactive effects, genotoxicity, mutagenicity and immunotoxicity testing. Various stressors affect the environment sometimes showing synergistic effects, which are very difficult to quantify or predict. These threats require more experimental and theoretical developments in order to produce approaches for characterization and appropriate strategies and assays for screening in order to detect the harmful agents and prevent them from reaching the sensitive endpoints. This volume contains the edited versions of the papers presented at the third International Conference on Environmental Toxicology. The papers are grouped into the following broad subject areas: Environmental Health Risk; Ecosystem Health; Biodegradation, Bioremediation and Biomonitoring; New Trends in Environmental Toxicology.