Ionizing and Nonionizing Radiation

Vocabulary practice flashcards covering ionizing and nonionizing radiation, measurement units, health effects, and historical exposure incidents based on Chapter 8 lecture notes.

Radiation

The propagation of energy through space or some other medium.

Ionizing Radiation

Radiation that possesses sufficient energy ($> 12.4\,\text{eV}$) to knock electrons out of atoms through a process known as ionization.

Non-ionizing Radiation

Radiation that has enough energy to move electrons around atoms in a molecule or cause them to vibrate, but lacks sufficient energy ($< 12.4\,\text{eV}$) to remove electrons.

Radon ($^{222}\text{Rn}$)

An inert, colorless, radioactive gas that emits alpha ($\alpha$) radiation; it is a decay product in the uranium series that concentrates in basements and represents the second leading cause of lung cancer in the United States.

EPA Action Level for Radon

An annual average indoor air screening level of $4\,\text{pCi/L}$, at or above which remediation is required or recommended.

Cosmic Rays

High-energy particles originating from outer space (the sun and galaxy) that interact with the atmosphere to create secondary air showers, delivering higher radiation exposures to individuals at high altitudes.

Nuclide

A nucleus characterized by a specific atomic mass, atomic number, and specific nuclear energy state.

Radionuclide

An atom that has an unstable nucleus and undergoes spontaneous radioactive decay.

Isotope

Different forms of the same chemical element containing identical numbers of protons but differing numbers of neutrons.

Radioactive Decay

The spontaneous process by which an unstable radionuclide loses energy by emitting radiation.

Half-Life ($T_{1/2}$)

The time required for a quantity of radioactive material to lose half of its radioactivity.

Alpha Particle ($\alpha$)

A heavy, positively charged subatomic particle consisting of 2 protons and 2 neutrons (a helium nucleus) ejected from an atom's nucleus that lacks the energy to penetrate paper or the outer layer of skin.

Beta Particle ($\beta$)

A small, fast-moving particle with a negative electrical charge (a high-energy electron) emitted from a nucleus during radioactive decay that can be stopped by aluminum, plastic, or clothing.

Gamma Ray ($\gamma$)

Weightless packets of pure energy (photons) originating from inside the nucleus that possess deep penetrating power, requiring inches of lead or feet of concrete to stop.

X-ray

Photons of pure energy emitted from atomic processes outside the nucleus, generally lower in energy and less penetrating than gamma rays.

Geiger Counter

A handheld instrument used to measure environmental area exposure to beta and gamma radiation by detecting audible electrical pulses caused by gas ionization in a detector tube.

Film Badge

A personal dosimeter containing dental X-ray film that darkens proportionally with radiation exposure, worn by occupational workers to measure personal dose.

Curie (Ci)

The standard U.S. unit of radioactivity describing the rate of atomic disintegrations, where $1\,\text{Ci} = 3.7 \times 10^{10}\,\text{disintegrations per second}$.

Becquerel (Bq)

The SI unit of radioactivity defined as exactly one atomic disintegration per second ($1\,\text{Ci} = 3.7 \times 10^{10}\,\text{Bq}$).

Roentgen (R)

The traditional U.S. unit of radiation exposure measuring the ionizing ability of gamma rays and X-rays traveling through air ($1\,\text{R} = 2.58 \times 10^{-4}\,\text{C/kg}$).

Rad

The traditional U.S. unit of absorbed dose representing $0.01\,\text{J/kg}$ of radiation energy absorbed by matter ($100\,\text{Rad} = 1\,\text{Gy}$).

Gray (Gy)

The SI unit of absorbed dose defined as one joule of radiation energy deposited per kilogram of matter ($1\,\text{J/kg}$).

Rem

The traditional U.S. unit of effective dose (dose equivalent) in tissue, calculated by multiplying the absorbed dose in Rad by the radiation quality factor: $\text{Rem} = \text{Rad} \times \text{QF}$.

Sievert (Sv)

The SI unit of effective dose equivalent, calculated by multiplying Gray by the radiation weighting factor ($\text{Sv} = \text{Gy} \times W_R$), equal to $100\,\text{rem}$.

Quality Factor (QF)

A biological weighting value used to calculate dose equivalent; it equals $1$ for beta particles, gamma rays, and X-rays, and equals $20$ for alpha particles.

Nonstochastic Health Effects

Acute radiation health outcomes characterized by a specific threshold dose, below which effects do not occur, and a severity that is directly proportional to the dose received.

Stochastic Health Effects

Long-term, chronic radiation outcomes (such as carcinogenesis and genetic mutations) that occur by chance without a threshold dose, where probability increases with dose but severity is independent of dose.

Hormesis

The biological hypothesis that low doses of a toxic substance or ionizing radiation impart beneficial or stimulatory defense mechanisms, whereas high doses produce harmful adverse effects.

Radium Jaw

A severe form of mandibular bone cancer suffered by female watch dial painters who ingested Radium-226 ($^{226}\text{Ra}$) through brush 'mouth tipping' in the early twentieth century.

Three Mile Island Accident

A commercial nuclear incident that occurred on March 28, 1979, in Pennsylvania, where mechanical failure and operator error caused a partial reactor meltdown rated as a Level 5 disaster.

Chernobyl Disaster

A catastrophic nuclear accident that occurred on April 26, 1986, in Ukraine, resulting from design flaws and human error that led to a reactor explosion, 31 direct deaths, and a Level 7 disaster classification.

Fukushima Daiichi Disaster

A major nuclear emergency that occurred on March 11, 2011, in Japan, triggered by an earthquake-induced tsunami causing equipment failure, multiple meltdowns, and a Level 7 classification.

Radiological Dispersal Device (RDD)

A conventional explosive paired with radioactive materials (commonly termed a 'dirty bomb') designed as a weapon of mass disruption to induce panic, contamination, and economic harm rather than nuclear-scale destruction.

Extremely Low Frequency (ELF) Radiation

Nonionizing radiation in the $50\,\text{Hz}$ to $60\,\text{Hz}$ range produced by electric power transmission lines, which induces weak currents in the human body without definitive proof of causing cancer.

Optical Radiation

The combined segment of the electromagnetic spectrum comprising ultraviolet radiation, visible light, and infrared radiation.

UV-C

The germicidal ultraviolet band covering wavelengths from $100\,\text{nm}$ to $280\,\text{nm}$.

UV-B

The erythema ultraviolet band spanning wavelengths from $280\,\text{nm}$ to $315\,\text{nm}$, recognized as the most hazardous UV radiation range to human health.

UV-A

The blacklight ultraviolet band spanning wavelengths from $315\,\text{nm}$ to $400\,\text{nm}$.

Photokeratitis

A painful corneal burn of the eye caused by acute exposure to ultraviolet radiation (especially UV-B), also referred to as snow blindness or actinic keratitis.

Malignant Melanoma (MM)

The most serious, aggressive, and potentially fatal form of skin cancer attributed to prolonged exposure to ultraviolet radiation.

Photoaging

Long-term skin damage caused by chronic UV exposure, clinically characterized by loss of elasticity, leathery texture, and the appearance of hyperpigmented brown spots.

Phototoxicity

An intense sun-induced dermal reaction leading to second-degree burns and blistering, often triggered by sun exposure combined with certain pharmaceutical drugs such as antibiotics or diuretics.

Photoallergy

An inflammatory skin reaction and severe itching dermatitis triggered when sunlight activates allergens or sensitizes the skin to contact substances.

Photosensitivity

An abnormal, heightened biological sensitivity of the skin to sunlight resulting from prior ultraviolet exposure or exposure to photosensitizing substances.

UV Index

A standardized scale (ranging from 1 to 11+) published by the EPA and NOAA that communicates the daily risk level of ultraviolet radiation exposure.