Table 1.

Key terms

Key Terms	Explanation
Environmental concentration	The amount of a chemical or environmental agent that is measured in an environmental medium at a specific place and time
Exposure pathways	The specific media through which exposures can occur (e.g., indoor and outdoor air, soil, dust, water, plants, animals, meat, dairy, fish, etc.)
Exposure routes	The ways that a chemical crosses an external barrier. Typically includes ingestion, inhalation and dermal exposure. Medical devices, regulated by the US FDA, can involve other internal exposures
Exposure scenarios	Provides information about chemical concentration, frequency of exposure, and duration of exposure as well as information about behaviors and characteristics associated with a specific life stage
External exposure	The amount of chemical present at an external barrier; sometimes referred to as the applied dose or administered dose
Internal exposure	The amount of chemical that crosses the external barrier, allowing it to reach (and, often, be measured in) internal tissues and fluids such as blood or urine. Sometimes referred to as dose, internal dose, or absorbed dose
Target site exposure	The amount of a chemical that reaches the tissue or organ where a biological action occurs