The definition of Exposure Science includes the study of how health and well-being can be improved for people by changing aspects of their environment.  "Toxic Exposure" can occur when a person comes into contact with anything that can harm their health or well-being, whether it is a hazardous chemical or an unsafe social situation.  

Exposure can be generally defined to be any sort of contact or influence that occurs between observable physical systems (such as people!), whether they be biological, physiological, chemical, social, or behavioral.  Physical or chemical exposure routes can be through inhalation, dermal contact, or by ingestion.  

If phenomena can be observed using human senses, indirect chemical or biological indicators, or using machine-based sensors, then we can talk about how one system of phenomena can be "exposed" to another system of phenomena, and vice versa. Systems can be defined at any relevant scale.

When a system is "exposed", it experiences a change, whether that change may be a physical deformation, energy flux, a chemical reaction, an infection, or a behavioral response (e.g., smoking, drinking, eating). We can talk about exposure occurring at any scale of physical observation, from the tiniest atoms or molecules up to cells, organisms, families, societies, and cultures.