Table 2.

Concepts, terms and definitions related to exposure, from ES21 Federal Working Group on Exposure Science (2015).

Concept (sub-concept)	Definition	Related prevalence type(s)
Exposure	Contact between an agent and a target. Contact takes place at an exposure surface over an exposure period	Point prevalence, period prevalence
Acute exposure	A contact between an agent and a target occurring over a short time, generally less than a day. (Other terms, such as “short-term exposure” and “single dose,” are also used)	Point prevalence, period prevalence
Chronic exposure	A continuous or intermittent long-term contact between an agent and a target. (Other terms, such as “long-term exposure,” are also used)	Period prevalence
Cumulative exposure	The sum of exposures of an organism to a pollutant over a period of time	Period prevalence
Time averaged exposure	The time-integrated exposure divided by the exposure duration. An example is the daily average exposure of an individual to carbon monoxide. (Also called time-weighted average exposure)	Period prevalence
Time integrated exposure	The integral of instantaneous exposures over the exposure duration. An example is the area under a daily time profile of personal air monitor readings, with units of concentration multiplied by time	Period prevalence
Dose	The amount of agent that enters a target after crossing an exposure surface	Point prevalence, period prevalence
Cumulative dose	The total dose resulting from repeated exposures of ionizing radiation to an occupationally exposed worker to the same portion of the body, or to the whole body, over a period of time	Period prevalence