Environmental toxicology, field of study in the environmental sciences that is concerned with the assessment of toxic substances in the environment. Although it is based on toxicology, environmental toxicology draws heavily on principles and techniques from other fields, including biochemistry, cell biology, developmental biology, and genetics. Among its primary interests are the assessment of toxic substances in the environment, the monitoring of environments for the presence of toxic substances, the effects of toxins on biotic and abiotic components of ecosystems, and the metabolism and biological and environmental fate of toxins. Environmental toxicology is a multidisciplinary field of science focusing on the study of the harmful effects of various chemical, biological, and physical agents on living organisms in the ecosystems, including humans. It occupies an important niche among toxicology, environmental health, and public policy.