An Overview of Radiation & its Effects on Humans Exposure to ionizing radiation is considered to be dangerous for humans. The rays or particles can do damage to human tissue to an extent that is dose dependent: the more radiation, the more damage. One theory on the relationship between absorbed radiation dose and the probability of health effects is that it is linear without threshold, which would mean that there is a possible risk of health effects with any dose, however small. While there may indeed be no absolutely safe dose, but there are dosages that are considered acceptable for practical purposes and unlikely to produce health effects. The risk of exposure is also dependent to a certain degree on the length of time over which the exposure occurred. The body can tolerate small doses that add up over time better than the same exposure all at once. All humans are exposed to some radiation simply by living on earth. This naturally occurring or "background" radiation comes from the radioactive decay of naturally occurring radioactive elements in the earth's crust. In addition to this, other sources of radiation are part of the course of everyday life: dental or medical X rays, microwave radiation, luminous watch dials, color televisions, cosmic radiation, smoke alarms, exit signs; a variety of sources of exposure to extremely small doses which add up slowly over time since dosage of radiation is cumulative over a lifetime. When an exposure occurs over an extended period of time, it is referred to as "Chronic Exposure". All of us are chronically exposed to radiation naturally and in the course of daily life. Persons working in the nuclear industry or utilizing a radiation source in the course of their work receive additional exposure. Standards have been set to protect such workers from dangerous dosages of radiation. However, these standards tend to change (lower) as more is learned about the effects of radiation on the human body. A principal exists in the field of radiation protection which is referred to by the acronym "ALARA", which stands for As Low As Reasonably Achievable. Under this principle all exposures are kept to standardized minimum. In addition, the industry is required to take measures to reduce exposure if they can do so at a reasonable cost. In order to monitor occupational exposures, the worker wears a film badge or "dosimeter" to measure the amount of radiation they are exposed to. Records are kept of the readings so that cumulative dose tabulation can be kept. Recent recommendations have resulted in a lowering of the maximum acceptable exposure. As indicated by the Uranium Institute, "Dose limits are considered to be the maximum acceptable exposure for an individual but they do not represent an acceptable level of exposure for a large number of individuals, or a level of exposure to which an individual can be repeatedly exposed". There are numerous international, federal and private organizations which disagree on how much exposure is "unhealthy". Some feel that any dose of ionizing radiation, no matter how small, has the potential to do cellular damage. Others believe that there is not enough evidence to support such claims. One common agreement, however, is that there is no one standard physiological reaction to specific levels of radiation. Some people are able to tolerate certain types of radiation better than others. Persons exposed to the same sources of "acute" (short-term) radiation can end up later in life with very different physiological results. Ultimately, it is important for those concerned to investigate all current avenues of research. Please visit our "Links" section for groups who have more information on radiation and its effects on the human body.

Questions and Answers

Q- What is radiation? All material is composed of atoms. Atoms are comprised of various particles, which include the nucleus. The nucleus contains particles called protons and neutrons, and the outer shell is made up of other particles called electrons. The nucleus maintains a positive electrical charge, while the electrons have a negative electrical charge. The forces within the nucleus work toward maintaining a stable balance between the positive charge of the protons and the negative charge of the electrons. The process by which the nuclei of atoms work toward becoming stable is to get rid of excess energy. Unstable nuclei may emit a quantity of energy, or they may emit a particle. This emitted atomic energy and/or particle is what is commonly called radiation.

Q- What kinds of radiation are there? There are two basic types of radiation: One type of radiation is tiny fast-moving particles that have both energy and mass, which is known as particle radiation. The other kind is pure energy with no weight. This radiation type is comprised of vibrating or pulsating waves of electrical and magnetic energy.

Q- What is ionizing/non-ionizing radiation? Ionization is the process of removing electrons from atoms, leaving behind two electrically charged particles (ions). Some forms of radiation like visible light, microwaves, or radio waves do not have sufficient energy to remove electrons from atoms and hence referred to as non-ionizing radiation. Ionizing radiation causes changes in living tissue.

Q- What is radioactive decay? When large atoms become unstable they emit radiation energy to become stable again. This process is called radioactive decay. This radiation can be emitted in the form of a positively charged alpha particle, a negatively charged Beta particle, or Gamma and X-rays. Q- How does radiation affect the human body? The biological effects of radiation on living cells may result in three outcomes: Cells die and are removed thru normal biological processes Cells incorrectly repair themselves resulting in biophysical mutation and replication, creating free radicals which result in diseases such as cancer. In some instances, injured or damaged cells are able to repair themselves, resulting in little residual damage

Q- How can radiation exposure be minimized? There are 3 main ways to reduce a person's amount of radiation absorption. Time -limiting or minimizing exposure time will reduce the dose received from the source of the radiation. Distance - The intensity of the radiation will decrease the further one is from the source. Shielding - creating a barrier between the radiating source and the individual will help to protect from the harmful effects.

Q- What is meant by the term "Half-Life"? Half-life is a constant; all atoms of the same element have the same half-life just as they have the same "mean" life. The half-life of a nuclide is the time it takes for half of the original number of atoms to decay. This constant rate of decay varies depending upon the particular element involved.

Q- What is Fission? The fission interaction is the basis of all nuclear chain reactions, without it there would be no nuclear reaction. In fission, the neutron bombards an atom of fissionable material splitting it apart and producing additional free neutrons to perpetuate the reaction, as well as heat energy and radiation energy. A fissionable element will have a heavy nucleus from which an average of two or three neutrons are emitted when it is struck by a neutron.