Acute exposure: a one time exposure of relatively short duration usually less than two weeks.

Aggregate exposure: the amount of exposure from multiple pathways from the same substance.

Chronic exposure: an exposure to a chemical or hazardous substance that occurs over a period of time usually more than 3 months.

Cumulative risk: the risk from all substances that act with the same mechanism of toxicity over all of the multiple pathways in which they may act.

Developmental stages: temporal intervals in distinct anatomical, physiological, behavioral, or functional characteristics that can contribute to potential differences in vulnerability to environmental exposures.

Dose: a combination of the frequency and duration of exposure to a toxicant, the amount of the pollutant in the environment, and individual susceptibility factors such as gender, age, genes, existing health condition, socioeconomic factors.

Macroactivity: highly general description of what a child does during a specific period of time or developmental stages, i.e., playing, school attendance, crawling, toddling, etc.

Microactivity: a very detailed description of an activity that could lead to an exposure. Some examples of microactivities leading of childhood exposures are mouthing of objects and crawling on the floor with subsequent hand contact with dirt.

Microenvironment: location a child occupies for a specified period of time, (e.g., outdoors - lawn versus outdoors - school playground).

Paraoccupational exposure: The transmission of potentially toxic quantities of industrial agents from occupational settings to homes and residences is referred to as take-home contamination. Take-home contamination has been more vividly called "fouling one's own nest."

Pica: the intentional ingestion of soil and other non-nutritive substances.

Toxicant: toxic substances that are produced by or are a by-product of anthrogenic (human-made) activities.

Toxicodynamics: the study of the cellular and molecular mechanisms of the action of a poison.

Toxin: toxic substances that are produced naturally.