![]() The emissions from three units (Harris 1500A, Incoterm SPD 10/20, and Telco 40) in use at the newspaper facility were measured in the UV, visible, IR, and RF bands. The measurements were undertaken in response to a request from the Newspaper Guild and the New York Times for an evaluation of possible radiation hazards to which employees working with VDTs might be exposed. ![]() Department of Health, Education, and Welfare (Moss et al., 1977). The first detailed measurements of radiation emitted by VDTs were made by the National Institute for Occupational Safety and Health (NIOSH) of the U.S. Thus, the laboratory studies cited in Table 3.1 provide the best measures of actual emissions from VDTs. Under controlled laboratory conditions it is possible to use shielding, special time-averaging techniques, and more sensitive instruments to measure the actual emission levels or to set a much lower limiting value. Furthermore, in some of the field surveys, instruments of limited sensitivity were used and the emissions were very weak, so that the actual emission levels could not be determined in these cases it could be determined only that the emission levels were less than some value (usually the radiation exposure standard). In the field studies reviewed, VDTs and measuring instruments were not shielded from ambient radiation thus, the readings obtained represent the sum of the VDT emissions and all other sources of radiation present. Some differences appear in the levels of radiation reported in different studies (see Table 3.1) the largest differences occur between field surveys and laboratory studies. Maximum Values Reported From Several Radiation Measurement Studies. The principal studies reported in the literature are summarized in Table 3.1. All of the studies have reached the same conclusion: emissions of all types of electromagnetic radiation-X rays, ultraviolet (UV), visible (light), infrared (IR), and radio frequency (RF) radiation, including microwaves-are well below accepted occupational and environmental health and safety standard limits. ![]() Field surveys and laboratory studies have been conducted by government agencies in this country and abroad (Moss et al., 1977 Cox, 1980 Terrana et al., 1980 Bureau of Radiological Health, 1981 National Institute for Occupational Safety and Health, 1981), private organizations (Weiss and Petersen, 1979), and independent groups (Wolbarsht et al., 1980). In many cases, measurements were undertaken because of concerns expressed by VDT users about potential radiation hazards. The radiation emissions of a wide variety of different types of VDTs have been measured, and most types of VDTs in current use have been adequately surveyed for all types of potentially hazardous electromagnetic radiation. ![]() The radiation emitted in any part of the spectrum may be either broadband (e.g., most infrared radiation emitted by VDTs is broadband) or limited to discrete wavelengths or frequencies, as is most common for radio frequency radiation emitted by CRT circuits. CRTs also have sweep oscillator circuits, which emit radio frequency radiation. For example, VDTs that use a cathode-ray tube (CRT) display produce internal X radiation the tube face, however, is designed to filter out this radiation so that it does not leave the tube. Electronic products in which certain types of high-voltage components are used can produce X radiation (i.e., X rays). VDTs are designed to emit visible radiation (light), and all electronic products that increase in temperature, including VDTs, emit infrared (thermal) radiation. The types and levels of radiation emitted vary with the device. Most electronic products, including video display terminals, emit electromagnetic radiation. Types and Levels of Radiation Emitted by VDTs
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