NIOSH Publications on Video Display Terminals; Current Literature EMF-Link [ EMF-Link Home | Online Store | Comments | Up One Level ]

NIOSH Publications on Video Display Terminals (Revised)

June 1991; iii + 84 pp.

U.S. Department of Health and Human Services
Public Health Service
Centers for Disease Control
National Institute for Occupational Safety and Health
Division of Standards Development and Technology Transfer
4676 Columbia Parkway
Cincinnati, OH 45226

This document is available from National Technical Information Service as document PB92-109230 (price code A05, $19.00)

NTIS
Port Royal Road
Springfield, VA 22161
Telephone: (703)487-4650

This publication is a compilation of materials developed by the National Institute for Occupational Safety and Health (NIOSH) on the health effects associated with video display terminals (VDTs).

The first section of the publication includes a bibliography of all NIOSH reports and publications on VDTs, listed by type: NIOSH-numbered publications; hazard evaluations and technical assistance reports; contract reports; journal articles, book chapters, and presentations; and miscellaneous reports.

The journal articles and book chapters listed may be obtained through local public or university libraries. The other documents are available directly from NTIS at the above address:

The second section of the report contains full-text copies of selected references listed in the bibliography.

Millar points out that in our society, workers are frequently those who first encounter a new substance or technology, and are thus the first to be put at risk. Dangers to workers often serve to raise a general alarm for the community as a whole. Investigations to date suggest that the VDT revolution in the workplace has produced few problems, considering the scope of the technologic change. But the perception that VDTs are hazardous is widespread. Millar responds to each concern raised. He first notes that all forms of radiation from VDTs measured were at levels well below those documented in the scientific literature as necessary for causing adverse biological effects. In response to the fact that VDT operators do report frequent visual and musculoskeletal strains and discomfort, Millar described NIOSH studies contrasting good and poor conditions, which underscored the importance of glare control, certain workstation dimensions, chair adjustability and back support, and rest breaks in easing operator discomfort. Millar outlined NIOSH's plans to study the effects of VDT use on reproductive health. Millar's testimony concludes with recommendations concerning workstation design, illumination, work regimens, and vision testing for VDT users.

The purpose of this paper was (1) to review the various studies of VDTs conducted or sponsored by NIOSH, (2) to present the NIOSH recommendations on preventing visual and musculoskeletal strains in VDT operators, and (3) to recommend future research. Altogether, NIOSH has conducted radiation measurements in a dozen locations on more than 300 VDTs from about two dozen manufacturers, without finding any VDT emitting radiation of any consequence. NIOSH's survey for evidence of eye disorders found no indication of excess cataracts in VDT operators, but did find a high incidence of complaints of musculoskeletal and visual strains. NIOSH conducted four field studies and several laboratory ergonomic studies focusing on musculoskeletal and visual strains in VDT workers. These studies showed that good ergonomic design leads to reduced health complaints and increased productivity. NIOSH has not conducted any studies focused exclusively on psychological stress in VDT users, but NIOSH studies that included psychological stress have not shown any clear relationship between VDT work and psychological strain, although various stress factors were more prevalent in the VDT workplace. NIOSH has responded to several requests to study clusters of miscarriages and other reproductive problems among VDT operators. In two of these reported incidences, NIOSH confirmed a statistically significant increase in miscarriages, but these studies have obvious limitations. Further studies of this issue are planned. Based on the results of the studies mentioned in this paper and research reports from other laboratories, NIOSH developed control technology recommendations with respect to workstation design, illumination, work regimens, and vision testing. The authors of the paper recommend more research on the effects on visual processes and reproductive outcomes of VDT use; work-rest regimens and other job design measures to minimize psychological stressors and musculoskeletal and visual strains, workstation equipment designs to prevent musculoskeletal and visual strains, and design of VDT screens to reduce eyestrain.

This paper presents a progress report on NIOSH's study of the effects of VDT use on reproductive health. NIOSH's goal was to design and implement a sound epidemiological study of a large number of working women using VDTs, including an appropriate comparison group. The protocol included study subjects from BellSouth and AT & T telecommunications companies at their facilities in the Southeast. Bellsouth employs a large number of female employees who spend most of their day working on VDTs, while AT & T has many female employees doing similar work without VDTs. Each group provides sufficient number of women of childbearing age to be able to detect a greater increased risk of miscarriages in the exposed group, if such a risk exists. After receiving extensive peer review, the protocol was revised and submitted to the Human Subjects Review Board, which approved the protocol in May, 1985. The protocol was then submitted to the Office of Management and Budget (OMB) for its approval. OMB rejected the protocol in December, 1985 on grounds of methodological deficiencies, but indicated that the CDC had made a credible case for conducting a study. NIOSH made several changes in the study protocol in response, and resubmitted the protocol to OMB. At the time this paper was presented, OMB clearance was pending. The paper includes a chronology of activities relating to the study's design and approval.

This article discusses information that has been gathered in the past few years related to the health effects of VDTs. Particular emphasis is given to the issues that continue to be raised by VDT users. Murray explains that VDTs generate radiofrequency, extremely low frequency, and ultrasonic radiation. VDT users fear that these types of radiation will produce cataracts, reproductive problems, and facial skin rashes. Animal and human studies have shown that these types of health problems can result from exposure to a high level of radiation. NIOSH has conducted radiation surveys to measure the emissions from several hundred video terminals to determine whether the radiation emitted by VDTs exceeds the thresholds for biological effects available in the current literature. Most of the RF energy associated with VDTs is in the 15 to 250 kHz frequency range. There is no Federal occupational standard for this frequency range, but the American Conference of Governmental Industrial Hygienists (ACGIH) has established a standard down to 10 kHz. The maximum operator exposures from the terminals tested were less than the ACGIH standard by a factor of five or more. Although much higher levels are present very close to the VDT surface, this occurs so close to the screen that it is unlikely the operator would ever be exposed to them. Electrostatic fields around the terminals are highly variable and drop off rapidly as the distance form the CRT face increases. Murray argues that based on present knowledge, existing standards appear to be adequate to protect those using a VDT day in and day out for many years. He also points out that NIOSH surveys have not shown large differences in the radiation emissions between individual terminals or between different brands or models. Employees' exposure does not seem to increase as the terminals become older or with multiple terminals present. Murray concludes by pointing out that the radiation levels emitted by a video display terminal are below the occupational exposure standards existing in the United States and, in many cases, are below the detection capability of the survey instrumentation used. Considering the radiation measurements, biological injury thresholds, and occupational exposure standards, the VDT does not present a radiation hazard to the VDT operator.

The author described ongoing progress in an investigation conducted by NIOSH which was designed to answer the question "do VDTs cause adverse reproductive outcomes?" by factoring out the influence of stress to obtain a clearer answer to the question of the influence of electromagnetic field (EMF) radiation from the video display terminal (VDT). At the time of writing, the interviews had just been completed, so the author focused her talk on aspects of the study design and the rationale for them. Study results were described in a subsequent publication (N Engl J Med 324:727-733, 1991). The study included all adverse pregnancy outcomes rather than focusing on a single outcome, and used a cohort design so that objective company personnel records were used to define VDT use and identify a reference group similar to VDT users. This reference group was similar with respect to socioeconomic factors, ergonomic and stress factors. The study focused on spontaneous abortions and major congenital malformations; the latter group included birth defects that are always considered to be major, and a second subgroup in which the severity could not be determined. The undetermined group was to be reviewed using records of birth defects by 2 physicians and categorized as severe if they affected survival, required substantial care, resulted in handicaps or interfered with prospects for a productive life. Other outcomes to be examined included prematurity, low birth weight, and neonatal mortality. Exposure was to be defined in several different ways depending upon the outcome under study. A simple exposure metric was to be defined based on occupational category, and additional exposures calculated for the gestational period relevant to the endpoint (e.g., the first trimester for spontaneous abortion, the entire pregnancy period for low birth weight). The author concluded by stating that they had approximately 2,500 women in the final dataset, and interview data was just being processed at the time of this discussion. The paper ended with a transcript of questions and answers following the presentation; several of the questions concerned the need to obtain accurate assessments of the EMF exposure for both the VDT and reference group. In answering questions about changes to the study made at the insistence of the Office of Management and Budget (OMB), the author noted that changes made to the interview questions limited the ability of the study to evaluate any differences in workplace stress, or to assess possible reduced fertility as an outcome. [7727]

This report addresses the subject of electric and magnetic field emissions of video display terminals (VDTs), both radiofrequency (RF) and extremely low-frequency (ELF), at AT & T and Bellsouth telephone operator facilities. The purpose of the study was to assess the strength of the electric and magnetic fields produced by the different types of displays to which participants in the NIOSH study could have been exposed. The exposure evaluation included a study of the fields associated with VDTs and two other forms of displays which do not use cathode-ray-tube technology. These two non-VDT types of displays represent the equipment used by the control population in the study. A study of 96 displays, selected at random, and located in nine cities, was conducted. The study showed that the strength of the fields decreases extremely rapidly with increasing distance from the VDT screen, so that exposure of individuals using VDTs is strongly related to how far they sit away from the VDT. In conclusion, the authors state that based on measurements on 96 displays comprised of both VDT and non-VDT type displays that typical personnel exposures to electric and magnetic fields are (1) relatively low, (2) within a relatively confined range of magnitudes reported by many researchers, (3) are not highly dissimilar to exposures commonly encountered from radio stations and other devices routinely found in he home or workplace and (4) are generally substantially less than any electromagnetic field exposure limits developed for radiation protection purposes by organizations within the United States and many other countries.

IVI Online Home Page EMF-Link Home Page Leave Us a Comment
Copyright (c) 1994-2008, Information Ventures, Inc.
Mail us at: Customer-Service@infoventures.com
http://infoventures.com