—A complex bacterial toxin composed of protein, lipid, and polysaccharide that is released upon lysis of the cell.


—Contact of an individual with a chemical or physical agent. Exposure is quantified as the amount of the agent available at the exchange boundaries of the individual (e.g., skin, lungs, gut) and available for absorption.

Exposure assessment

—The determination or estimation (qualitative or quantitative) of the magnitude, frequency, duration, and route of exposure.

Exposure pathway

—The course a chemical or physical agent takes from a source to an exposed individual. An exposure pathway describes a mechanism by which an individual or population is exposed to chemical or physical agents at or originating from a site. Each exposure pathway includes a source or release from a source, an exposure point, and an exposure route. If the exposure point differs from the source, a transport/exposure medium (e.g., air) or media (in cases of intermediate transfer) also is included.

Highly exposed individual (HEI)

—An individual who remains for an extended period at or adjacent to the site where maximum exposure occurs.

Indicator organism

—A microorganism that is used for monitoring whether a certain set of pathogens might be present.

Indirect exposure

—Exposure involving multimedia transport of chemicals from source to exposed individual. For example, consumption of produce grown on biosolids-amended soil.

Loading rate

—The maximum loading limit of a chemical per unit of time, permissible on a given site.

Margin of exposure

—A ratio defined by EPA as a dose derived from a tumor bioassay, epidemiological study, or biologic marker study, such as the dose associated with a 10% response rate, divided by an actual or projected human exposure.

Mutipathway exposure

—Exposure to an agent (chemical, physical, or biological) by various routes, such as inhalation, ingestion, and dermal absorption.

No-observed-adverse-effect level

—The highest dose of a chemical that was administered to animals in a toxicity study without producing an observed adverse effect.

Probabilistic approaches

—Evaluating a range of possible risk estimates and their likelihood, tied to various mathematical models of the likely distribution of potential values, instead of relying on single numbers or point estimates.

Reasonable Maximum Exposure (RME)

—A semiquantitative term referring to the lower portion of the high end of the exposure distribution. It

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