7th LEA/CIWMB Conference (2004)

Understanding Radiation and Its Effects

Radiation is Energy

• The energy is given off by unstable (radioactive) atoms and some machines.

Radiation and Radioactive Material are a Natural Part of Our Lives

• We are constantly exposed to low levels of radiation from outer space, earth, and the healing arts.
• Low levels of naturally occurring radioactive material are in our environment, the food we eat, and in many consumer products.
• Some consumer products also contain small amounts of man-made radioactive material.

Unstable Atoms Decay

• The number of “decays” that occur per unit time in the radioactive material tell us how radioactive it is.
  • Units include Curies (Ci), decays per minute (dpm), and Becquerels (decays per second).
• When an unstable atom decays, it transforms into another atom and releases its excess energy in the form of radiation.
• Sometimes the new atom is also unstable, creating a “decay chain”

Forms of Radiation

• When unstable atoms transform, they often eject particles from their nucleus. The most common of these are:
  • Alpha Radiation-High energy, but short range (travels an inch in air, not an external hazard)
  • Beta Radiation-Longer range (10–20 feet in air) and can be a skin and eye hazard for high activity beta sources.
• Gamma Rays (electromagnetic radiation)-Often accompany particle radiation. This “penetrating” radiation is an external hazard and can travel 100s of feet in air.

How Unstable Is It?

• The “Half-Life” describes how quickly Radioactive Material decays away with time.
  • It is the time required for half of the unstable atoms to decay.
• Some Examples:
  • Some natural isotopes (like uranium and thorium) have half-lives that are billions of years
  • Most medical isotopes (like Technicium-99m) last only a few days

Some Isotopes & Their Half Lives

The Amount of Radioactivity is NOT Necessarily Related to Size

• Specific activity is the amount of radioactivity found in a gram of material.
• Radioactive material with long half-lives have low specific activity.
  • 1 gram of Cobalt-60 has the same activity as 1800 tons of natural Uranium

What is a “Dose” of Radiation?

• When radiation’s energy is deposited into our body’s tissues, that is a dose of radiation.
• The more energy deposited into the body, the higher the dose.
• Rem is a unit of measure for radiation dose.
• Small doses expressed in mrem = 1/1000 rem.
• Rad & R (Roentgens) are similar units that are often equated to the Rem.

Typical Doses

Radiation is a type of energy; Contamination is material

• Exposure to Radiation will not contaminate you or make you radioactive.
• Contamination is Radioactive Material spilled someplace you don’t want it.
• Radioactive contamination emits radiation.
• Contact with Contamination can contaminate you with the material.

Our Bodies Are Resilient

• DNA damage is most important and can lead to cell malfunction or death.
• Our body has ~ 60 trillion cells
  • Each cell takes “a hit” about every 10 seconds, resulting in tens of millions of DNA breaks per cell each year.
  • BACKGROUND RADIATION causes only a very small fraction of these breaks (~ 5 DNA breaks per cell each year).
• Our bodies have a highly efficient DNA repair mechanisms

Types of Exposure & Health Effects

• Acute Dose
  • Large radiation dose in a short period of time
  • Large doses may result in observable health effects
  • Early: Nausea & vomiting
  • Hair loss, fatigue, & medical complications
  • Burns and wounds heal slowly
  • Examples: medical exposures and accidental exposure to sealed sources
• Chronic Dose
  • Radiation dose received over a long period of time
  • Body more easily repairs damage from chronic doses
  • Does not usually result in observable effects
  • Examples: Background Radiation and Internal Deposition Dividing Cells are the Most Radiosensitive

Rapidly dividing cells are more susceptible to radiation damage.

• Examples of radiosensitive cells are
  • Blood forming cells
  • The intestinal lining
  • Hair follicles
  • A fetus

At HIGH Doses, We KNOW Radiation Causes Harm

• High Dose effects seen in
  • Radium dial painters
  • Early radiologists
  • Atomic bomb survivors
  • Populations near Chernobyl
  • Medical treatments
  • Criticality Accidents
  • In addition to radiation sickness, increased cancer rates were also evident from high level exposures.

Effects of ACUTE Exposures

At LOW Doses, We PRESUME Radiation Causes Harm

• No physical effects have been observed
• Although somewhat controversial, this increased risk of cancer is presumed to be proportional to the dose (no matter how small).

The Bad News: Radiation is a carcinogen and a mutagen

The Good News: Radiation is a very weak carcinogen and mutagen!

Long-term Effects of Radiation

• Radiation is assumed to increase one’s risk of cancer
  • The “normal” chance of dying of cancer is ~ 23% (~460 out of 2,000).
  • Each rem is assumed to increase that risk by 0.05% (~1 chance in 2,000).

Conclusion Understanding Radiation and it’s Effects

• Radiation is energy given off by unstable atoms and some machines.
• Radioactive Material contains unstable atoms that give off radiation when they “decay.”
• Contamination is Radioactive Material spread someplace where you don’t want it.
• Radiation damages our cell’s DNA, fortunately our body has very efficient repair mechanisms.
• Large acute doses of radiation can cause sickness or even death. The severity of the effects are proportional to the dose at large doses.
• All exposures to radiation are presumed to increase the risk of cancer. The amount of “increased risk” is assumed to be proportional to exposure.
• Very Small DOSE = Very Small RISK

References

Risk, DNA, & Dose Effects: RadEFX(sm) Ionizing Radiation Health Effects Forum Copyright © 1994-1997 Baylor College of Medicine, All rights reserved. http://radefx.bcm.tmc.edu/ionizing/subject/risk/acute.htm

Which cites several references, including: NCRP Report 98 "Guidance on Radiation Received in Space Activities," NCRP, Bethesda (MD) (1989).

Health Effects Model for Nuclear Power Plant Accidence Consequence Analysis. Part 2, Scientific Basis for Health Effects Models. U.S. Nuclear Regulatory Commission, Report NUREG CR-4214, Rev. 1. Part II. Washington, D.C. NRC: 1989

Smithsonian, V26 No.9. December 1995; “RISK, Part 2: Safeguarding our cells” by James Trefil.

Other Graphics and Info from: Uranium Information Centre Melbourne, Australia http://www.uic.com.au/index.htm

DOE; Transportation Emergency Preparedness Program (TEPP) http://www.em.doe.gov/otem/program.html

Please note these are only outlines of the presentations. If you would like a CD of the entire LEA/CIWMB Conference including these presentations, in full, please e-mail Melissa Hoover-Hartwick.

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Last updated: October 06, 2011