Tokaimura (Japan's Sep. 30, 1999) Nuclear Accident:
It's Causes, Health & Environmental Effects

Freshman Seminar:  Technology & Environment
Professor Najmedin Meshkati
Fall 1999
University of Southern California

Radiation Health Effects

--Background of Radiation—
--Scales and Dosages—
--Radiation Health Effects of Dosages--

The following students contributed to this section of the paper:

Tyler Burke
Loren Chidoni
Print Journalism
Justin Evans
Electrical Engineering
Bahman Mahdavi
Bahram Mahdavi

Background of Radiation:

     Understanding radiation and how it is measured is essential in determining its health impact on the body. The radiation scale and the effects of dosage on cell and tissue damage help conceptualize the major health effects of radiation.

     Radiation consists of particle rays such as alpha and beta rays, electromagnetic rays such as gamma and x-rays, and neutron particles. Alpha rays are produced after spontaneous decay of radioactive atoms including radium, radon, uranium, and plutonium.  Alpha rays pass less than one millimeter in water, and because a single piece of paper can stop an alpha ray, health effects only appear when alpha-emitting particles are ingested. The beta rays consist of a fast electron with a mass of 1/2000 of the mass of a proton or neutron.  These rays are produced by the spontaneous decay of carbon-14, strontium-90, phosphorus-32, and tritium. Like alpha rays, beta rays only cause health problems through internal exposure. Gamma rays, which are similar to visible light, have a shorter wavelength and higher energy than ultraviolet rays.  Gamma rays are produced following the decay of radioactive materials such as cobalt-60, which because of its ability to penetrate deeply into our bodies, is often used for cancer radiotherapy.  X rays are similar to gamma rays, but they consist of an array of different wavelengths, whereas gamma rays have a fixed value specific to the radioactive material.  Neutron particles, the last component of radiation, are released after nuclear fission (splitting of an atomic nucleus that produces large quantities of energy) of plutonium or uranium (all above information was taken from the Radiation Effects Research Foundation).

Scales and Dosages:

     Radiation is measured in many different ways.  The first people to devise a way to measure radiation were Marie and Pierre Curie.  The unit of measurement they used was called the “curie,” and it “describes the intensity of a sample of radioactive material in terms of atoms of the material that decay each second” (Understanding Radiation). The basis for this measurement is the rate of 37 billion atoms per second for one gram of radium.  The other units for measurement of radiation are: rads, grays, rems, and sieverts.  The United States uses the basis of rems, including branching SI units of the same system, such as millirems or kilorems.  One sievert equals 100 rems.  One gray equals 100 rads.  Rads are the basis for the world when discussing a scale to measure radiation. “A rad is defined as a certain amount of energy deposited by high-speed particles per gram of biological tissue” (Nuclear Madness). Rems seem arbitrary when considering amounts of radiation.  There’s no scientific evidence to back up the amount recorded in rems, but rads are used on the basis of science, and are defined in a scientific way. Rads and rems are equal if gamma rays are being measured.

     One way to measure radiation is through using a Geiger counter.  “A Geiger counter contains a special gas-filled tube that separates two electrodes.  When radiation passes through the tube, it interacts with the gas, causing an electrical pulse that can be measured on a meter or by audible clicks.  The number of pulses in a given time is a measure of the intensity of radiation” (Understanding Radiation). To put it in perspective, “each individual in the United States is exposed to .003 sievert per year due to natural background radiation sources” (Free Concise Encyclopedia).

Radiation Health Effects of Dosages:

     The different particles in radiation don’t always directly damage cells. Because neutrons don’t have an electrical charge, they rarely damage cells, but often cause ionization (loss of an electron resulting in the disruption of chemical bonds) in the body after interacting with hydrogen nuclei. Although neutrons don’t directly damage cells, they cause more severe damage to the body than gamma rays.  Ionization can also cause oxidation (addition of oxygen atoms), which results in chromosome aberrations, mutations, or cell death. In addition to ionization, radiation can also cause excitation (change in energy level of an electron).

    When living tissue is affected by ionizing radiation, there is always a chance that the cells are harmed or destroyed.  However, the damage depends on what kind of radiation is received, how the dose is absorbed, how quickly it is absorbed, and how strong the tissue is.  The existence of the energy in the tissues harm the DNA and reduces the ability of the cell to reproduce. The doses of radiation absorbed are related to the energy, and high doses of radiation cause major health effects, such as burns, cell damage, and death.  According to the Free Concise Encyclopedia, the human blood vessel will be severely damaged if exposed to 4000 rads or more, resulting in brain swelling, profound shock, neurological disturbances, and death within 48 hours.  Less severe damage will occur with doses of 1000 to 4000 rads, and death will transpire within 10 days. Human bone marrow will be destroyed with doses of 150 to 1000 rads, which will cause infection, hemorrhage, and a prospect of death in four to five weeks.

    In addition to cell damage, if small areas of the body are exposed to radiation, localized tissue damage will begin.  Other resources report “sudden large doses exceeding 100,000 rems can cause radiation sickness, with short-term symptoms including nausea, vomiting, extreme tiredness, and hair loss”  (Understanding Radiation).  In cases where there is a low dose of radiation, the body can heal itself and the damaged cells without major health effects.  This includes exposure over a long period of time.

    In conclusion, the effects of dosage on the health effects of radiation are directly proportional—the higher the dosage, the more damage occurs. Understanding what radiation is and how it is measured puts the dosage in perspective, and demonstrates how lethal the effects can be.

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