absorbed dose

Energy imparted to a body by radiation, measured per unit mass (kg) of tissue.

activity

The number of transformations that take place each second in a given amount of radioactive material.

alpha particle

A positively charged particle, indistinguishable from a helium atom nucleus and consisting of two protons and two neutrons.

alpha radiation

Same as alpha particle.

becquerel

The special name for the unit that expresses a measure of activity. One becquerel corresponds to one disintegration per second of any radionuclide.

beta particle

A high-speed electron or positron, emitted in radioactive decay.

curie

A unit of radioactivity, equal to the amount of a radioactive isotope that decays at the rate of 3.7 ´ 1010 disintegrations per second.

dermal uptake

The transfer of a contaminant from air, water, or soil into or through the outer skin layer; considered an exposure route in an exposure assessment.

developmental and reproductive effects

Effects caused by some physical, chemical, or biological agent, such as radiation, to the formation and development of a fetus, that results in one or more observed defects, which are not passed on to succeeding generations.

displacement

A chemical reaction in which one kind of atom or molecule is removed from combination and replaced by another.

dissociation

A chemical process by means of which a change in physical condition causes a molecule to split into simple groups of atoms, single atoms, or ions.

dose

The quantity of energy or chemical agent delivered to a specific living tissue following exposure.

dose assessment

The process by which uptake and dose of a toxic substance are identified and quantified.

dose equivalent

An absorbed dose that is adjusted or weighted to account for the potential of different radiations with the same damage.

excitation

The addition of energy to a system, transferring it from a ground state to an excited state.

exposure

The condition of having contact with a physical or chemical agent of harm.

exposure assessment

The process by which contact with a toxic substance is identified and quantified.

gamma radiation

Electromagnetic radiation emitted by radioactive decay and having energies in a range from ten thousand (104) to ten million (107) electron volts.

gray

The special name for the unit that expresses a measure of absorbed dose. One gray corresponds to an energy deposition of one joule per kg of living tissue.

half life

1. For a quantity of radiation—the time required for half of the nuclei in a sample of a specific isotopic species to undergo radioactive decay.

2. For ingested quantities—the time required for the radioactivity of material taken in by a living organism to be reduced to half its initial value by a combination of biological elimination processes and radioactive decay. Known as the biological half-life.

heritable genetic effects

Genetic damage caused by an external agent such as radiation, which manifests itself in the gene carrier and is capable of being passed on to succeeding generations.

ingestion

To take into the body by the mouth for digestion or absorption; considered an exposure route in an exposure assessment.

inhalation

To draw air into the lungs by breathing; considered an exposure route in an exposure assessment.

ionizing radiation

Radiation that converts the target totally or partially into ions on impact.

isotope

One of two or more atoms having the same atomic number but different numbers of neutrons in their nuclei.

model

A schematic description of a system, theory, or phenomenon that accounts for its known or inferred properties and may be used for further study of its characteristics

monitor

To test or sample on a regular or ongoing basis the air or an object's surface for radiation level.

neutron

An electrically neutral subatomic particle, which is stable when bound in an atomic nucleus. Neutrons and protons form nearly the entire mass of atomic nuclei.

nuclide

A type of atom specified by its atomic number, atomic mass, and energy state, such as carbon 14.

probability

A number expressing the likelihood that a specific event will occur, expressed as the ratio of the number of actual occurrences to the number of possible occurrences.

proton

A stable, positively charged subatomic particle. Neutrons and protons form nearly the entire mass of atomic nuclei.

radiation

Energy emitted in the form of rays, waves, or particles by the atoms and molecules of a radioactive substance as a result of nuclear decay.

radioactivity

Spontaneous emission of radiation, either directly from unstable atomic nuclei or as a consequence of a nuclear reaction. This radiation includes alpha particles, nucleons, electrons, and gamma rays, emitted by a radioactive substance.

relative biological effectiveness (RBE)

An adjustment factor used to adjust an absorbed dose to account for its relative potential to do damage in biological tissue.

risk

The estimated probability of injury, loss, or detriment. A measure of the deleterious effects that may be expected as the result of an action or inaction.

risk assessment

The process by which the risks associated with an action or inaction are identified and quantified.

sampling

The act, process, or technique of selecting an appropriate environmental sample.

sievert (Sv)

A unit for expressing the equivalent magnitude of an absorbed dose which has been adjusted by a factor that expresses the relative tissue damage potential of absorbed doses of radiation; equivalent to one joule of x-ray energy deposited per kg of target.

transport

To move or be conveyed from one place to another. In the context of environmental contamination, a contaminant is transported from one location to another by advection (e.g., wind) or diffusion (e.g., dilution in air) processes.

transformation

Alteration of a chemical substance from one chemical form to another through a chemical or physical reaction. Radioactive decay is a nuclear transformation whereby an atom changes from one nuclide to another.