Health Issues

Radiation Explained

All matter is composed of atoms. An element, such as uranium, is composed of one type of atom. Each atom of an element has a nucleus which contains positively charged protons and electrically charged neutrons. The nucleus contains almost all the mass (and hence weight) of the atom. Surrounding the nucleus are one or more rings of negatively charged electrons.

All atoms of the same element have the same number of protons in their nuclei. The number of neutrons, however, may vary. For example, all atoms of uranium have 92 protons. Yet, some atoms of uranium have 146 neutrons, while others have 143 neutrons. Atoms of the same element that have different atomic masses are called isotopes.

About 50 naturally occurring isotopes, including those of uranium and radium, are unstable. This means they emit particles and energy from their nuclei in order to become more stable. Atoms that decay in this way are said to be radioactive. Marie Curie, a Nobel Prize-winning physicist and chemist, was the first person to use the word radioactive to describe an element.

Radioactive atoms give off alpha particles (large particles made of two protons and two neutrons) and beta particles (high-speed electrons.) They also give off electromagnetic energy in the form of gamma rays. These particles and rays given off in the decaying of unstable nuclei are called radiation.

Our concern in Camden is with ionizing radiation; there are three types:

1. X-rays.....electromagnetic radiation of very short wavelength and high energy produced when high-energy electrons suddenly give up energy. In nature, X-rays are produced by the sun and other heavenly bodies. Most X-rays from outer space are absorbed by the atmosphere and never reach us. Man-made X-rays are produced chiefly by special electrical machines.

2. Gamma rays.....similar to X-rays, but they are produced by the spontaneous decay of radioactive materials.

3. Particle radiation.....includes alpha particles and beta particles. They are also produced by the decay of radioactive materials.

One of the most confusing things about ionizing radiation is trying to understand all the terms used to describe it or measure it. Here are the terms and units of measurement most frequently used in discussion of the Camden Radiation Site.

Gamma Radiation - Gamma Radiation is the major kind of radiation being measured at the contaminated sites in Camden. Gamma radiation results from the breakdown or radioactive materials like uranium, radium and thorium normally found in small quantities in the soil and rock in this area. The manufacturing process at the General Gas Mantle Factory used an ore containing radioactive thorium, to make gas mantles.

Radon and Thoron - Radon is the decay product of uranium. Thoron is one of the decay products of thorium. Both of these are odorless, colorless gases that can accumulate in air and water.

Thoron and Radon Progeny - These are the decay products given off by thoron and radon gas. Radon progeny are the major source of human exposure to alpha radiation. It is this alpha radiation that is responsible for cellular changes in the respiratory tract, which causes radon-induced lung cancer. Consequently, alpha particle exposure, under certain circumstances, can be quite harmful.

Sensitivity to radiation varies with age. Fetuses and newborns are much more sensitive that adults are. Sensitivity also varies with the type of tissue or organ radiated. The bone marrow (where red blood cells are produced) and the white blood cells (which fight bacterial infections) are highly sensitive to radiation. Cartilage, muscle, and nervous tissue are much more resistant. Radiation effects on the human body also vary with the intensity of the radiation to which a person is exposed, what kind of ionizing radiation it is, and how one comes into contact with it.

Three basic principles are important in protection against radiation:

1. Time.....the effects of radiation exposure are cumulative. Therefore, the less time one is exposed the less likely the exposure will cause any effect.

2. Distance....the further one is from the source of the radiation, the less likely he/she is to be exposed.

3. Shielding.....alpha particles can travel a short distance through air and can easily be stopped by a sheet of paper of the human skin. They are only dangerous if breathed into the lungs of ingested in food or water. Beta Particles can penetrate the skin a short distance; they can be blocked by plastic or wood. Gamma rays can pass completely through the skin and penetrate internal organs; concrete or lead is necessary to block them.

The above text is taken from "Radiation and You - A Health Information Pamphlet", written by the Health Team.

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