Environmental Health Attn: Nightingale

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Chapter 8

Ionizing and
Non-Ionizing Radiation

Learning Objectives

By the end of the chapter the reader will be able to:

  • Define the terms ionizing radiation and nonionizing radiation
  • State the differences between ionizing and nonionizing radiation
  • Describe sources and types of ionizing and nonionizing radiation
  • Discuss the health effects of exposure to ionizing and nonionizing radiation
  • Describe major incidents in which the population was exposed unexpectedly to ionizing radiation

Radiation

  • The term radiation refers to “Energy traveling through space. Some types of radiation associated with radioactivity are alpha and beta particles and gamma and X rays.”
  • Radiation also includes neutrons, which are uncharged.

Ionizing Radiation

  • Radiation that “has enough energy to remove tightly bound electrons from atoms, thus creating ions.”
  • Its properties are used to generate electric power, to kill cancer cells, and in many manufacturing processes.

Anthropogenic (Man-Made) Sources of Ionizing Radiation

  • X-rays and other procedures used in medicine (medical tests and therapies)
  • Consumer products
  • Radioactive substances used in industry
  • Nuclear power generators
  • Radioactivity (e.g., radioactive fallout) from the production and detonation (primarily for testing purposes) of nuclear weapons.

Natural Sources of
Ionizing Radiation

  • Cosmic rays
  • Other forms of radiation that impinge upon earth from outer space
  • Radiation from geologic formations that contain radioactive elements (radioelements) such as uranium, from which radon gas is formed as a decay product

Types of Ionizing Radiation

  • Particulate energy (e.g., highly energetic protons, neutrons, and α and β particles)
  • Electromagnetic energy in the form of photons (e.g., γ rays and X-rays)

Radioactivity

  • “The spontaneous emission of radiation from the nucleus of an unstable atom.
  • As a result of this emission, the radioactive atom is converted, or decays, into an atom of a different element that might or might not be radioactive.”

Absorbed Dose

  • “The radiation energy absorbed per unit mass of an organ or tissue and is used in studies of the damage to a particular organ or tissue.”

Dose Equivalent

  • Obtained by weighting the absorbed dose in an organ or tissue by a radiation weighting factor that reflects the biological effectiveness of the charged particles that produce ionization within the tissue.

Exposure

  • “A quantity used to indicate the amount of ionization in air produced by X- or gamma-ray radiation. The unit is the roentgen (R).”

Common Units of Radiation

  • Curie (Ci): A unit of measure used to describe the amount of radioactivity in a sample of material.
  • Rad: Radiation absorbed dose. The former unit of absorbed dose of ionizing radiation.

Common Units of Radiation, continued

  • Rem: (Roentgen equivalent in man) A measure of radiation dose related to biological effect. A rem is a measure of dose deposited in body tissue, averaged over the mass of the tissue of interest.
  • Roentgen (R): The unit of exposure from X- or gamma rays

Factors That Affect the Amount of Radiation Exposure

  • The total amount of time exposed to the radioactive source
  • Distance from the radioactive source
  • Degree of radioactivity (rate of energy emission) of a radioactive material

Acute Health Effects of
Ionizing Radiation

  • Include tissue burns and radiation sickness (e.g., nausea, weakness, and loss of hair)
  • At low levels: usually does not produce immediately detectable harm
  • At high levels: capable of producing fatal injuries

Stochastic Effects

  • The term stochastic means that there is an increased probability of the occurrence of an adverse health event.
  • Associated with low levels of exposure to radiation over long time periods.
  • Carcinogenesis and genetic damage such as changes in DNA are possible stochastic effects of radiation exposure.

Natural Sources of
Exposure to Ionizing Radiation

  • Cosmic radiation (radiation from space)
  • Uranium deposits that cause increases in background radiation levels in some geographic areas
  • Radon
  • A decay product of uranium, radioactive radon gas may seep into homes, thus exposing the residents.

Anthropogenic Sources of Exposure to Ionizing Radiation

  • Nuclear power plants have been known to leak ionizing radiation into the environment under unusual conditions.
  • Radioactive fallout from above-ground nuclear testing has exposed large populations to radiation.
  • Decommissioned and abandoned nuclear weapons facilities and storage of nuclear wastes can be a source.
  • Medical X-rays and radiation diagnostic and therapy procedures produce exposures to ionizing radiation.

Figure 8-4 Sources of radiation exposure in the United States.

Source: Reprinted from United States Nuclear Regulatory Commission. Available at: http://www.nrc.gov/images/reading-rm/basic-ref/glossary/ionizing-radiation.jpg. Accessed April 3, 2010.

Uranium

  • A common element in the earth’s crust
  • Uranium ores uraninite and pitchblende are found in large amounts in North America, Africa, and Australia.
  • Nearly all plants, animals, and aquifers contain tiny amounts of uranium.

Radon

  • Inert, colorless, and extremely toxic gas
  • Produced by the decay of radium and uranium
  • Classified as a Class A carcinogen
  • Associated with long-term adverse health effects

Extraterrestrial Radiation

  • Primary cosmic rays originate from outer space (e.g., the earth’s galaxy and the sun) and interact with the earth’s atmosphere to produce secondary cosmic rays.
  • Cosmic rays have the ability to penetrate and cross the human body easily.

Nuclear Facilities and Accidents

  • Nuclear facilities include weapons production plants, test sites, and nuclear power plants.
  • The major consequence of the Three Mile Island accident was that no new nuclear power plants have been built in the United States since 1979.
  • One of the largest accidents was at a nuclear facility in Chernobyl, Ukraine, in 1986.

Effects of a Nuclear Explosion

  • The blast (damage to or destruction of buildings and those in them)
  • Heat (destruction or injury by high temperatures or fire)
  • Intense light (damage to eyesight)
  • Ionizing radiation (causing Acute Radiation Syndromes of different degrees of severity)

Further Effects of a
Nuclear Explosion

  • Persons near the nuclear explosion would experience thermal burns and radiation-induced skin injuries.
  • A major byproduct of the detonation of a nuclear weapon is radioactive fallout.
  • Radioactivity will dissipate over several weeks, but crops and food animals taken from the area may be unsuitable to consume.

Medical Uses of Ionizing Radiation

  • About 40% of radiation exposure has been attributed to medical exposure.
  • Medical procedures include the use of X-ray machines, nuclear medicine, and radiation therapy

Nonionizing Radiation

  • Nonionizing radiation refers to “Radiation that has enough energy to move atoms in a molecule around or cause them to vibrate, but not enough to remove electrons, . . . Examples of this kind of radiation are sound waves, visible light, and microwaves.”

Examples of
Nonionizing Radiation

  • Extremely low frequency (ELF) radiation (e.g., high tension power lines)
  • AM, FM, VHF-TV radio waves
  • Microwave radiation
  • Infrared radiation (IRA, IRB, IRC) - the source of heat in heat lamps used for keeping food warm
  • Visible light radiation
  • Ultraviolet radiation (UVA, UVB, UVC)

Health Effects of
Nonionizing Radiation

  • Extremely low frequency (ELF) radiation does not appear to produce many discernible short-term health effects.
  • Higher frequency levels (i.e., radiofrequency and microwave radiation) causes heating of the body.

Sources of Exposure to ELF (50 to 60 Hertz)

  • Originates from electric power poles, wiring in the walls of buildings, and some electrical appliances

Electromagnetic Frequency

  • Electricity that flows through transmission lines may produce electromagnetic fields (EMFs).
  • Research literature suggests that findings are inconsistent, not definitive, with respect to EMF exposure and cancer.

Radiofrequency Radiation and
Cell Phones

  • Cell phones are a very low-power apparatus that transmits in the radiofrequency range of 900 to 1800 megahertz (MHz).
  • As of 2009, there were an estimated 270 million and 4.1 billion cellular telephones in use in the U.S. and worldwide, respectively.
  • Widespread popularity of cell phones means that even small adverse health effects could have substantial implications for population health.
  • Cell phone antenna banks are themselves a source of RF radiation.

Sources of
Ultraviolet Radiation (UVR)

  • Sources of UVR:
  • Welders’ arcs
  • Lamps used for tanning beds
  • Some flood lamps used in photography
  • Halogen desk lamps
  • Lightning
  • Electrical sparks
  • Sunbathing

UVR

  • UVR coming from the sun is subdivided into UVA, UVB, and UVC, depending upon the wavelength of the light.
  • Of the three forms of UVR, UVB is considered to be the form that is most harmful to human health.

The Ultraviolet (UV) Index

  • To help protect exposed persons from excessive amounts of sunlight, the UV index provides a daily forecast of the expected risk of overexposure to the sun.
  • The index predicts UV intensity levels on a scale of 1 to 11+, where low indicates a minimal risk of overexposure and 11+ means an extreme risk.
  • The index is calculated on a next-day basis for every ZIP code across the United States.

Effects of UV Radiation

  • Temporary conditions include burns and temporary blinding
  • Long-term consequences:
  • Photoaging of the skin
  • Nonmelanoma skin cancer (NMSC)
  • Malignant melanoma (MM)
  • Retinal damage
  • Lens opacities