19 Should I be concerned about monitor emissions?
Description
This article is from the comp.sys.ibm.pc.hardware.video Frequently Asked Questions, by Michael Scott with numerous contributions by others. (v1.0).
19 Should I be concerned about monitor emissions?
[From: Michael Scott (scott@bme.ri.ccf.org) and Bill Nott (BNott@bangate.compaq.com)]
In the November 8, 1996 issue of Science (Vol. 274, pg. 910) is an announcement that the US National Research Council "seemed to deal a mortal blow to one of the most polarised and long-running environmental controversies -- whether electromagnetic fields (EMF's) from power lines or household appliances pose a threat to human health. After an exhaustive, 3-year study, a 16-member panel said there is 'no conclusive and consistent evidence' that ordinary exposure to EMF's causes cancer, neurobehavioral problems, or reproductive and developmental disorders." For those interested in what this is all about, a brief summary follows.
CRT's (Cathode Ray Tubes) direct a beam of electrons at a thin layer of phosphor which coats the screen on your monitor. When the electrons strike the phosphor, shadow mask and other screen components, x-rays are produced. The amount and energy of the x-rays depends on the accelerating voltage. The relatively low voltages in CRT's (compared to commercial x-ray machines) means that relatively low quantities of low energy x-rays are produced and modern monitors are so well shielded, that there is no concern of being irradiated over time. Though it is possible for a damaged monitor to emit x-ray radiation, it is unlikely that harmful amounts will be released, and most x-rays would be directed towards the back or sides of the monitor. Any damage to the front of the CRT severe enough to increase x-ray emission would cause the CRT to implode.
All televisions and computer monitors must comply with various worldwide standards for ionizing emissions. Information relating to this compliance is typically included on the product label, or within the users manual.
Recently, concerns about low frequency (LF) and very low frequency (VLF) electro-magnetic and electro-static emissions have been raised. Many studies have been established recently to determine if these concerns are warranted. None of the studies has concluded that there is any correlation between the radiation and possible health risks. In Sweden, a large study was undertaken and as a result, the Swedish government, and the Swedish Workers Union (TCO) both established recommended limits of radiation for office equipment, including Video Display Terminals (VDT's). The same limits are applied to monitors; the Swedish Government standard is referred to as MPR 1992, and the TCO standard is referred to as TCO. Many new monitors adhere to the Swedish emission regulations.
Epidemiologists have suggested that the risk factors for some childhood cancers (particularly leukemia) are as high as two for some populations exposed to low frequency EMI. A risk factor of two means that the odds of being afflicted with a disease is twice as likely in the exposed population than in a control population. In general, a risk factor of less than six is not considered significant (cigarette smoking has a risk factor of 10-20). As a result, several groups have publicly stated that there is no significant health risk from EMI radiation levels experienced by people from home appliances or nearby high voltage lines.
Critics of the Swedish study suggest that it was simply too huge. According to a television documentary, over 800 comparisons were made for correlation between exposure and pathologies. Statistics would suggest that given enough completely random and uncorrelated measures, the odds are that some of them will display a high correlation. As a result, any study that is large enough will produce correlations between _some_ of the measured quantities. Because of this criticism, and the fact that only correlation, and no causation was proved in the study, the Swedish government has since reversed their decision to mandate maximum EMI emissions.
Studies in the U.S. to determine if EMI could cause cancer or other illness, birth defects or any other health problems in rats have come up negative. The rats were exposed to 0-10000 mG (milli-Gauss) magnetic fields (the earth's magnetic field is ~500 mG), and their skeletal and visceral organs, reproduction, frequency of cancer and immunology all came up normal. The chronic studies that were undertaken by the same group will be completed in 1996. Other studies showed that EMI had no effect on the growth of cancer cells.
So, you have to make your own decisions, but the overwhelming majority of experts agree that there is no cause for concern.
For more information, contact:
EMF INFOLINE Tel: (800) 363-2383 (in the USA) In Washington, DC, call: 484-1803
Continue to:
My Books
