What Everyone Should Know About Radiation

01. What is radiation
02. What is natural "background" radiation
03. What are the units of radiation
04. What are the health hazards of infrared radiation
05. What are the health hazards of ultraviolet radiation
06. What are the health hazards of X-rays
07. Is all radiation bad
08. What is "low-level radiation"
09. Does low-level X-radiation pose a health hazard
10. What is a cathode ray tube (CRT)
11. Can I avoid all radiation
12. How does a CRT produce X-rays
13. When did the problem of X-radiation from TV's start
14. What are the concerns of video display terminals (VDT's)
15. What are some of the VDT hazards
16. Why the concerns today
17. Are the reports on VDT's conclusive
18. What are the health problems with VDT's
19. How much confidence is there in today's standards


1. What is radiation? There are various forms of electromagnetic radiation, such as radio waves, infrared, visible light, ultraviolet, x-rays, and gamma rays. Whenever electric charge undergoes acceleration an electromagnetic wave is formed which sends energy through space; in somewhat the same way as waves spread out over water when a stone is dropped into a pond. Radiation also includes the disintegration of radioactive substances. The radioactive substances emit alpha, beta, and gamma rays, which are streams of high-speed electrons. The radiation is produced when atoms of natural radio-active material decay or split, generating streams of photons vibrating at enormous speeds in wavelike form. Radiation has two basic forms: ionizing and nonionizing. Ionizing radiation causes ionization (splitting into charged atomic fragments) of the atoms and molecules that make up the cells and tissue of living creatures.
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2. What is natural "background" radiation? We live in a smog of radiation due to cosmic rays from outer space and intense radiation from solar activity. The air you breathe is radioactive due to naturally occurring radioactive elements, such as uranium, thorium, and radium in the rocks, soil, and masonry (like Grand Central's granite walls). The house you live in is radio-active -- more so if it's brick or stone than if it is wood. Much of the food you consume is radioactive from naturally occurring radioactive forms of carbon, hydrogen, potassium, and radium. Brazil nuts, milk, beer, and whiskey are naturally radioactive.
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3. What are the units of radiation? Radiation exposure is measured in roentgens and radiation absorption is radiation absorbed dose (rad) or roentgen equivalents man (rem). The amount of radiation delivered is referred to as dose and the measurement of these amounts is called dosimeter. For x-rays, roentgen of exposure will usually produce about 1 rad of absorbed dose in soft tissue. The rem is also a biological unit and represents the amount of radiation that is equivalent to 1 rad of 250 kvp (kilovolt-peak) X-rays.
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4. What are the health hazards of infrared radiation? The sensory nerve endings in both the cornea and iris of the eye are quite sensitive to small temperature elevations. It is generally considered that the blink reflex provides protection against infrared radiation up to levels in excess of those that cause flash burns of the skin. The absorbed energy may be conducted to interior structures of the eye and raise the temperature of that tissue as well as the cornea itself. Heating of the iris by absorption is considered to play a major role in the development of opacities in the crystalline lens, at lest for short exposure time.

Quantitative data for the production of lenticular opacities following exposure to infrared radiation are very limited.

The biological effects of infrared radiation depends upon the conversion of this radiation into heat as it falls on the surface. Prolonged exposure can cause the retina to detach itself from the eyeball. Infrared exposure may also cause opaqueness of the aqueous humor of the eye, resulting in partial or total blindness.
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5. What are the health hazards of ultraviolet radiation? Certain people are allergic to ultraviolet radiation (called photoallergies, allergies produced by ultraviolet light and other radiations by which chemical changes are produced) that can effect skin pigmentation. Susceptibility can be determined by dermatologists using skin test equipment for the various types of photo dermatoses. One skin test uses a 6-watt fluorescent tube to determine allergies to ultraviolet light.

A sufficient exposure to actinic ultraviolet radiation results in erythema or reddening of the skin (e.g., sunburn). Sufficient doses to the eye will cause keratoconjunctivitis, that painful effect know to most as welder's flash. Some individuals are hypersensitive to irradiation from specific optical spectral bands and may develop skin reactions described as photosensitivity.
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6. What are the health hazards of X-rays? X-rays, along with cosmic and gamma rays are ionizing radiation. The hazard is the shake up of the order of things in the body. The damaging action is either somatic or genetic. Somatic is the effect on the exposed individual; genetic is the effect on the progeny of the exposed person. Gamma and X-ray can pass through thick concrete without attenuation while other forms of ionizing radiation, such as alpha and beta particles, are readily stopped by a few inches of air, a sheet of paper, or foil.

Ionizing radiation can affect human cells by stripping one or more electrons from an individual atom and forming an electrically charged particle, called an ion. Depending in part on the rate and strength at which they are delivered, these ions can disrupt the machinery of cells, kill them, or harm the genes that pass human traits from one generation to the next.
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7. Is all radiation bad? No. There are benefits of radiation for medical diagnosis and treatment, national defense and its significant role in generating energy. The ideal is to limit radiation exposure and avoid all unnecessary radiation. In 1981 the National Radiological Protection Board in the United Kingdom revised and issued a popular booklet, Living with Radiation. The booklet introduces the difficult subjects of collective doses to the population, relative risks, and cost-benefit analysis. It also includes the latest recommendations of the International Commission on Radiological Protection that doses to individuals shall not exceed recommended limits for the appropriate circumstances, no practice shall be adopted unless it produces a positive net benefit, and all exposures shall be kept as low as reasonably achievable, economic and social factors being taken into account.
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8. What is "low-level radiation"? Low-level X-radiation is generally applied to non-penetrating radiation when the human body is exposed to radiation. The radiation is absorbed in the body tissue. In comparison, "hard X-rays" used for radiology are absorbed in bone, but pass through the body tissue.
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9. Does low-level X-radiation pose a health hazard? No one knows for sure. The radiation is absorbed by the first few layers of body tissue and the amount is accumulated over your total lifetime. One way to determine for sure would be to expose a certain number of persons to a daily dose of low-level radiation over their entire life-time. Since this is not practical, the risks are based on statistical data of large doses to large populations. A certain percentage of the exposed population would develop varying amounts of biological damage in themselves or cause genetic damage in their offspring. The problem of knowing for sure is further complicated by the fact that sensitivity to radiation varies by age and physiology, and different rays have different potencies. There is no true threshold of medical damage by X-rays. It depends on the individual and the dose. There is evidence to support the premise that small doses of radiation carry a probability, however remote, of some damage, particularly genetically.
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10. What is a cathode ray tube? A CRT is commonly called a picture tube in television sets. It is a vacuum tube in which the electrons streaming from the cathode are directed to strike a fluorescent screen and produce illuminated traces, visible from the exterior of the tube. These tubes are also used as video displays in computer systems and oscilloscopes.
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11. Can I avoid all radiation? No. You receive an average of 100 millirems of unavoidable background radiation a year from food, water, rocks, and cosmic rays. In France, people are exposed to as many as 350 millirems a year of background radiation compared with an average of 90 millirems in New York. The average background radiation is approximately 0.01 to 0.02 millirems per hour.
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12. How does a CRT produce X-rays? X-rays can be produced in any electron tube when a current is present and there is a potential of at least 5,000 volts. It usually takes 10,000 volts or more to produce an appreciable X-ray beam. The electrons are accelerated by the high voltage and strike materials in the interior surface of the tube. X-rays are produced when the high-speed electrons bombard the interior surface of the CRT. The problem is more acute for color TV than black and white, because of the higher voltages used for color TV. The voltage can be as much as 40,000 volts. Potential sources of X-ray emissions are the picture tube, the high-voltage power supply, and the shunt regulator tube.
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13. When did the problem of X-radiation from TV's start? In the late 1960's, a number of TV's with more than allowable X-ray emissions found their way into American homes. Emission standards were reevaluated after extensive measurements were made of TV's in American homes. In a report published by the Institute of Electrical and Electronic Engineers (IEEE), the basis for a common understanding of definitions and measurement procedures in determining the extent of a potential hazard was outlined at a conference held in Washington, DC The National Center for Radiological Health (NCRH) requested a survey of TV's in the Pinelles County of Florida. The Health Department found that 32% of the receivers emitted radiation in excess of the standard set by the National Committee on Radiation Protection and Measurements (NCRP). Almost concurrent with the Florida studies, a large scale survey of X-radiation from color receivers in homes were started on December 16, 1967, by the Technical Services Branch of the NCRH. Of the 1124 sets from 26 different companies tested in the Washington, DC area, 66 receivers emitted more than the standard. In 1971, the Bureau of Radiological Health was transferred to the Food and Drug Administration (FDA). The agency enforces the Radiation Control for Health and Safety Act of 1968 that provides radiation protection activities at the Federal level. The Bureau educates consumers about the benefits and possible risks of various radiation sources in their daily lives, from sunlamps to X-rays as technology provides more and more radiation-emitting products. Beyond assuring that these products are as safe as current techniques can make them, it is FDA's job to help consumers understand benefits and risks, and make intelligent decisions about their own radiation exposure.
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14. What are the concerns of video display terminals (VDT's)? About half a dozen studies have been done over the past two years in Europe and the United States. The major concern has been complaints from operators of VDT's who sit very close to the unit eight hours a day. A VDT is no more than an ordinary cathode ray tube identical to the television screen illuminating most American homes nightly. Personal computers and video games are rapidly becoming a standard household item and are viewed at a distance much closer than TV receivers.
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15. What are some of the VDT hazards? Milton Zaret, a New York consultant in clinical opthamology has made the strongest -- and most controversial -- claims that VDT's cause cataracts. He claims that safety standards governing exposure to electromagnetic radiation are all arbitrary. He also stated that dismissal of VDT's as a serious hazard was based on "meaningless standards". Staring at a VDT for long periods of time causes eyestrain. Reported "clusters" of miscarriages and birth defects have baffled epidemiologists in the United States and Canada. New cases of cataracts allegedly caused by video display terminals were reported at a conference held at the Loughborough University in Britain. Static electricity that builds up on the screen induces electric charges on the viewer's face. This charge attracts dust which irritates the skin.
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16. Why the concerns today? According to the National Institute for Occupational Safety and Health (NIOSH), more than 7 million Americans now work at these VDT's. And that doesn't count those who bought VDT's for home use. Some office workers have become concerned that the VDT's could be causing a variety of health problems. VDT's can, in fact, produce several types of radiation: X-rays, radio frequency, microwave, ultrasound, ultraviolet, infrared, and visible light. Changing Times reported in its February 1983 issue that anyone with a TV set manufactured before January 15, 1970, used as a display terminal for games or for home computers may be risking eye damage. youngsters may be at risk for radiation exposure far in excess of the National Council for Radiation Protection and measurement recommendations for radiation exposure. Although both the Canadian and U.S. governments have given VDT's what amounts to a clean bill of health, many unions, particularly in Canada, have fought and won the right for pregnant women to refuse VDT work. Canada's airline employees union want similar alternate-work provisions for its pregnant employees and tests to monitor any nonionizing radiation emissions by users of VDT's.
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17. Are the reports on VDT's conclusive? Definitely no. As an example, the Food and Drug Administration reported in April 1981 that all but 8 out of 125 VDT's checked emitted no more than 0.4 milliRoentgens (mR) per hour. The worst reading was 2.0 mR (400% more than the standard for television sets). In another report published by the Human Factors Society in 1981, no detectable ionizing radiation was measured from 136 terminals that were tested. Researchers from the National Radiological Protection Board in Britain measured radiation from VDT's in almost every part of the electromagnetic spectrum. In another report, FDA gave computer video screens a clean bill of health. However, in the same report, Milton Zaret, an opthamologist, diagnosed radiant energy cataracts caused by exposure to microwave emissions from the VDT's used by two newspaper employees. In his view, the FDA, OSHA, and NIOSH have been "consistently wrong from the start". The federal research centers have issued bad reports, bringing discredit upon themselves.

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18. What are the health problems with VDT's? Various topics were discussed at a conference held in England in July 1981. The conference was organized by the Human Sciences and Advanced Technology (HUSAT) Research Group. Static electricity charge on a CRT reduces the level of negative ions in the air breathed by the operator and can thereby aggravate the adverse effects of negative ion depletion, including headaches, nausea, and dizziness. Different light levels, eye movements from a manuscript and the CRT screen, and reflections on the CRT screen are problems for most operators who use CRT's for most of their workday. Eyestrain caused by staring at a CRT screen is a long-term source of distress. The operator's ability to adapt to the relatively low light levels emitted by the screen is further hampered by glare from windows, unshielded luminaries, and shiny desk tops. Flicker, caused by a phosphorescent image decaying before it is refreshed by the electron scan, causes eyestrain. In another article, the "ideal" office work station, which frees users from the time-consuming chores of walking to a filing cabinet and mailing letters, might be ergonomically unacceptable. Remaining seated in the same posture for hours can lead to permanent back injury, which, along with the eyestrain caused by staring at the CRT screen, is a long-term source of distress.
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19. How much confidence is there in today's standards? Disagreements about the somatic risks from low doses of ionizing radiation stem from two difficulties fundamental to the logic of inference from observational data. First, precise direct estimation of small risks requires impractically large samples. Second, precise estimates of low-dose risks based largely on high-dose data, for which the sample size requirements are more easily satisfied, must depend heavily on assumptions about the shape of the dose-response curve, even when only a few of the parameters of the theoretical form of the curve are known. There seems to be no way to evade the problem of curve fitting and extrapolation from high-dose estimates of excess risk. Resources are not available for adequate epidemiologic studies of populations exposed to low-levels of radiation, and if anyone should try to do them anyway, they would run considerable risk of obtaining misleading results; results that would derive at least some credibility from the vast effort of obtaining them. Present experience indicates that the accuracy of evaluations is almost always limited by biological uncertainties. Until these uncertainties are resolved, one is obliged to use significant safety factors based upon knowledge of extrapolating from animal to man, variation of susceptibility among individuals, and the experience gained from accidental injuries. Recommendations in a National Research Council report done for the National Cancer Institute advises caution in undertaking any new studies of populations exposed to low levels of ionizing radiation. The populations rarely will be large enough, nor their exposures to radiation well enough documented, for a study to yield meaningful results.
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1. Radiation: Why You May be Getting Too Much, Changing Times. 35:59 (April 1981).

2. J. Rotblat, Hazards of Low-Level Radiation -- Less Agreement, More Confusion, The Bulletin of Atomic Scientists. 37:31 (June/July 1981).
3. Mark Barnett, Getting a Grasp on Man-Made Radiation, FDA Consumer. 15:62 (June 1981).

4. C.E. Land, Estimating Cancer Risks from Low Doses of Ionization Radiation, Science. 209:1197 (Sept. 12, 1980).

5. D.H. Sliney and B.C. Freasier, Evaluation of Optical Radiation Hazards, Applied Optics. 12(1):1 (January 1973).

6. R.F. Dempewolff, What Everyone Should Know About Radiation, Popular Mechanics. 154:90 (November 1980).

7. A Rash of Hazards from Computer Screens, The New Scientist. 88:761 (Dec. 18-25, 1980).

8. J. Raloff, VDT's the European Experience, Science News. 137 (Aug. 29, 1981).

9. VDT and the Fetus - Cause for Concern? Science News. 377 (Dec. 12, 1981).

10. D.J. Nashel, L.Y. Korman, and J.O. Bowman, Radiation Hazard of Video Screens, New England Journal of Medicine. 308(14):891 (Sept. 30, 1982).
11. Video Display and Eyes, Changing Times. 12 (Feb., 1983).
12. E. Marshall, FDA Sees No Radiation Risk in VDT Screens, Science. 207:1120 (June 5, 1981).

13. B. Rados, VDT's Pass Medical Tests, FDA Consumer. (April 1981).
14. W.E. Murray, C.E. Moss, and W.H. Parr, A Radiation and Industrial Hygiene Survey of Video Display Terminal Operations, Human Factors. 23(4):413 (August 1981).

15. L.F. Spector, The Hazards of Radiation Around the Home, Machine Design. 40:46 (April 11, 1968).

16. M. Elecion, X-Radiation From Color Television Receivers, IEEE Spectrum. 5.95 (July 1967).

17. D. Lachenbruck, What You Should Know About X-Ray Radiation in TV Sets, Radio-Electronics. 38:54 (Nov. 1967).

18. K. Jones, HUSAT Conference Examines CRT Health Problems, Mini-Micro Systems. 49 (August 1981).

19. Examining the "Human" Aspects of Technology, Mini-Micro Systems. 50 (Aug. 1981).

20. S. Rippon, If You Fear Radiation, Open the Windows, Nuclear News. 24:102 (June 1981).

21. F. Urback, M.D., The Biological Effects of Ultraviolet Radiation, p. 533, Pergamon Press Ltd., London, 1969.

22. Urge Reduced Exposure from Radiological Technologies, Mechanical Engineering. 103:56 (Oct. 1981).

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