Environmental exposure is a fundamental concept and research area focused on the contact of biological systems (e.g., humans, ecosystems) with physical, chemical, and biological agents present in the environment. It investigates the sources, pathways, magnitude, duration, and frequency of such contacts, as well as the resulting dose and potential health or ecological effects across different populations and environmental media. This concept is critical for environmental health sciences, toxicology, epidemiology, and risk assessment, providing the essential link between environmental conditions and biological outcomes to inform policy and intervention strategies.