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Office work and physical factors: health aspects of electromagnetic fields and light
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine. National Institute for Working Life, Umeå, Sweden.
1997 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The overall aim of this thesis is to increase our knowledge of the physical environment of office workers with special focus on electromagnetic fields and to address the question of whether electromagnetic fields can directly or indirectly contribute to symptoms or discomfort among video display terminal ( VDT) workers. Furthermore, we have measured light modulation from various commonly used light sources in laboratory conditions and, as a second step, used modulated light as stimulus for provocation of neurophysiological responses in persons with perceived “electrical hypersensitivity” (EHS).During the last 20 years work-related illness among office workers has received increased attention. Changes in the physical environment, the introduction of VDTs and other electrical equipment and changes in light conditions have been discussed in this context. The basis for this thesis is the interdisciplinary Office Illness Project in Northern Sweden. Using a questionnaire completed by 4,943 office workers, 150 VDT workers with or without facial skin symptoms were selected for a case referent study of the electromagnetic fields in offices.When the measurements in the offices were performed in 1989, the general level of the 50 Hz magnetic fields in the offices was rather low, but in 5% of the offices the flux density exceeded 0.5 pT. At this level VDT monitors were shown to display detectable instability (jitter). Furthermore, the ability of test subjects (healthy volunteers) to detect jitter was shown to depend on both the amplitude and frequency characteristics of this instability. The study indicates that the instability of computer monitors and thereby the instability of the visual image of the VDT screen might be an increasing problem since it is known that the harmonic content of the general magnetic field in offices is on the rise.VDT monitors contributed to the magnetic field level at VDT workplaces in both extremely low and very low frequency ranges. However, the dominant source of electric fields in rooms was ungrounded electrical equipment, not VDT screens.High electric fields in the extremely low frequency range in the offices were associated with skin symptoms among VDT workers. The causal nature of this association cannot be determined since it may depend on undetected factors related to exposure. No associations were found, however, for any of the VDT-related electromagnetic fields and skin symptoms.Commonly used fluorescent tubes in our office environment have a degree of modulation of the light (flicker) that varies widely from less than 1% (fluorescent tubes with high frequency gear) up to nearly 100%. When persons with perceived EHS were exposed to flickering light, a higher amplitude of brain cortex responses were found at all tested frequencies compared with control subjects. These findings are of considerable interest, but further studies are required in order to establish a possible relationship between flickering light and discomfort/symptoms in persons with perceived EHS.

Place, publisher, year, edition, pages
Umeå: Umeå universitet och Arbetslivsinstitutet , 1997. , 46 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 530
Keyword [en]
Facial skin symptoms, office illness, electrical hypersensitivity, physical environment, flicker, jitter, neurophysiological effects
National Category
Environmental Health and Occupational Health
Identifiers
URN: urn:nbn:se:umu:diva-96906ISBN: 91-7191-386-6 (print)OAI: oai:DiVA.org:umu-96906DiVA: diva2:769180
Public defence
1997-11-28, Stora föreläsningssalen, Arbetslivsinstitutet, Umeå, Umeå universitet, Umeå, 09:30
Supervisors
Projects
digitalisering@umu
Available from: 2015-02-02 Created: 2014-12-05 Last updated: 2015-04-10Bibliographically approved
List of papers
1. A survey of electric and magnetic-fields among VDT operators in offices
Open this publication in new window or tab >>A survey of electric and magnetic-fields among VDT operators in offices
1993 (English)In: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187X, Vol. 35, no 3, 394-397 p.Article in journal (Refereed) Published
Abstract [en]

In this study, the ambient electric and magnetic fields as well as the electromagnetic fields associated with VDT's at 150 offices are measured. The aim of the study is to find out the general level of the various electromagnetic parameters in offices and establish a technical base for a case referent study of skin symptoms among VDT workers. The median value of the 50-Hz background field in the 150 offices is 0.07 muT. Seven of the offices have background levels higher than 0.5 muT, which is high enough to cause distortion of the picture on the screen. The dominating source for electric fields in the ELF range is electric equipment in the office, not the VDT's. The median value of the electric field in the VLF range is 1.5 V/m. The equivalent surface potential is less than 0.5 kV for 63% of the measured VDT's. The computer monitor is a major source for magnetic fields in the offices. The median value of the magnetic field in the ELF range in front of the VDT is 0.21 muT, and in the VLF range 0.03 muT.

Place, publisher, year, edition, pages
New York: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 1993
Keyword
Video display terminals, frequency, employees, units, work
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:umu:diva-99020 (URN)A1993MA76400009 ()
Projects
digitalisering@umu
Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2017-12-05Bibliographically approved
2. Skin symptoms among VDT workers and electromagnetic-fields: a case-referent study
Open this publication in new window or tab >>Skin symptoms among VDT workers and electromagnetic-fields: a case-referent study
1995 (English)In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 5, no 1, 29-37 p.Article in journal (Refereed) Published
Abstract [en]

Th is case referent study is a part of the Office illness Project in Northern Sweden. From a questionnaire study among 5986 office workers, 75 VDT workers with self-reported facial skin symptoms and the same number of referents were selected for this study. The environmental electric and magnetic fields in the office as well as electromagnetic fields associated with the VDT at the workplace were measured, The aim of this part of the project was to explore the role of the measured electromagnetic parameters in relation to skin symptoms. For most of the measured parameters there was no difference between cases and referents. However, more cases than referents were found in the highest exposure group for two of the measured parameters. Fm the background electric field in the mom the relative risk in terms of crude odds ratio (OR) was 3.0 (95% CI: 1.2-7.2) for the high exposed group (greater than or equal to 31 V/m) compared with the lowest group (less than or equal to 10 V/m). The same comparison for the magnetic field in the ELF-range (greater than or equal to 0.30 mu T vs less than or equal to 0.145 mu T) in front of the VDT gave an OR of 2.7(95% CI: 1.0-6.9).

Place, publisher, year, edition, pages
John Wiley & Sons, 1995
Keyword
VDT-workers, skin symptoms, electric, magnetic fields
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:umu:diva-99019 (URN)10.1111/j.1600-0668.1995.t01-3-00005.x (DOI)A1995QY68600005 ()
Projects
digitalisering@umu
Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2017-12-05Bibliographically approved
3. External power frequency magnetic field-induced jitter on computer monitors
Open this publication in new window or tab >>External power frequency magnetic field-induced jitter on computer monitors
1993 (English)In: Behaviour & Information Technology, ISSN 0144-929X, Vol. 12, no 6, 359-363 p.Article in journal (Refereed) Published
Abstract [en]

Power frequency magnetic fields with flux densities greater than 0.5 μT are not uncommon in offices. This level has been shown to induce jitter on VDT monitors. In the present project, these magnetic field-induced disturbances have been studied in the laboratory in order to establish a firm technical basis for future studies of the disturbance's influence on eye strain in VDT workers. Eight volunteers judged the occurrence of distortion when an applied external magnetic field was varied both in amplitude and frequency for 8 investigated VDT screens. The level of the external 50 Hz magnetic field when the distortion was detectable ranged from 0.6 to 1.1 μT. If the screen was viewed through a stereomicroscope (25 × magnification), the corresponding level was in the order of 0.2 μT. If the frequency difference between the external magnetic field and the refresh rate of the screen is only ±1-2 Hz, the disturbance is noticeable at even lower flux densities.

Place, publisher, year, edition, pages
Taylor & Francis, 1993
Keyword
jitter, magnetic field, VDT
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:umu:diva-99033 (URN)10.1080/01449299308924400 (DOI)
Projects
digitalisering@umu
Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2015-04-10Bibliographically approved
4. Power frequency magnetic fields and computer monitor instability
Open this publication in new window or tab >>Power frequency magnetic fields and computer monitor instability
1998 (English)In: Displays (Guildford), ISSN 0141-9382, E-ISSN 1872-7387, Vol. 19, no 2, 85-90 p.Article in journal (Refereed) Published
Abstract [en]

Owing to the increased use of electronic loads, the harmonic content of the magnetic field in buildings has increased and it is therefore of interest to study how the harmonics (i.e. 150 Hz magnetic fields) will affect the stability of the picture on the monitor screen. Another frequency of interest to study is 16.7 Hz, the frequency used by the Swedish railway. Ten volunteers were asked to judge the occurrence of jitter on a 15-in. color monitor screen, refresh rate 72.2 Hz, at different amplitudes and frequencies of the vertical applied magnetic field. The tested screen had a highest sensitivity to 150 Hz external magnetic field, followed by 60, 16.7 and 50 Hz. In a static magnetic field the screen had a sensitivity (displacement) of 0.031±0.006 mm per applied microtesla.

Place, publisher, year, edition, pages
Elsevier, 1998
Keyword
Jitter, Video display terminal, Harmonics, B-field
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:umu:diva-99025 (URN)10.1016/S0141-9382(98)00042-0 (DOI)
Projects
digitalisering@umu
Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2017-12-05Bibliographically approved
5. Amplitude modulation of light from various sources
Open this publication in new window or tab >>Amplitude modulation of light from various sources
1994 (English)In: Lighting Research and Technology, ISSN 1477-1535, E-ISSN 1477-0938, Vol. 26, no 3, 157-160 p.Article in journal (Refereed) Published
Abstract [en]

This work was done to obtain basic knowledge about various light sources and specially about light modulation, or flicker. The study showed that the modulation of light varied a lot between different ordinary light sources. In general the 100 Hz component in the flickering light dominated. For incandescent lights the modulation increased with decreasing power and was in the range 10-22%. Light from the tungsten-halogen lamps had 2-6% modulation. The most common light sources (single-colour fluorescent light) had a modulation of about 20%. Fluorescent tubes with better colour rendering (full-colour fluorescent and full-colour special fluorescent tubes) had a higher modulation, 30-40%, while light from high-frequency (HF) fluorescent tubes had a modulation of 0.9%. Light from conventional compact fluorescent tubes had a modulation degree of about 44%, and for HF compact fluorescent tubes it was 2-7%. Modulation of light from HF compact fluorescent tubes had a tendency to decrease with increasing tube size. The modulation of light from discharge lamps was in the range of 52% up to 100% and the curve form of the light from low pressure sodium vapour lamp (100% modulation) contained several high frequency components.

Place, publisher, year, edition, pages
Sage Publications, 1994
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:umu:diva-99026 (URN)10.1177/096032719402600305 (DOI)
Projects
digitalisering@umu
Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2017-12-05Bibliographically approved
6. Neurophysiological effects of flickering light in patients with perceived electrical hypersensitivity
Open this publication in new window or tab >>Neurophysiological effects of flickering light in patients with perceived electrical hypersensitivity
Show others...
1997 (English)In: Journal of Occupational and Environmental Medicine, ISSN 1076-2752, E-ISSN 1536-5948, Vol. 39, no 1, 15-22 p.Article in journal (Refereed) Published
Abstract [en]

An increasing number of people in Sweden are claiming that they are hypersensitive to electricity, These patients suffer from shin as well as neurological symptoms when they are near computer monitors, fluorescent tubes, or other electrical appliances, Provocation studies with electromagnetic fields emitted from these appliances have, with only one exception, all been negative, indicating that there are other factors in the office environment that can effect the autonomic and/or central nervous system resulting in the symptoms reported, Flickering light is one such factor and was therefore chosen as the exposure parameter in this study, Ten patients complaining of electrical hypersensitivity and the same number of healthy voluntary control subjects were exposed to amplitude-modulated light, The sensitivity of the brain to this type of visual stimulation was tested by means of objective electrophysiological methods such as electroretinography and visual evoked potential, A higher amplitude of brain cortical responses at all frequencies of stimulation was found when comparing patients with the control subjects, whereas no differences in retinal responses were revealed.

Place, publisher, year, edition, pages
Wolters Kluwer, 1997
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:umu:diva-99018 (URN)10.1097/00043764-199701000-00006 (DOI)A1997WF86000004 ()
Conference
7th International Congress of Psychophysiology, SEP, 1994, THESSALONIKI, GREECE
Projects
digitalisering@umu
Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2017-12-05Bibliographically approved

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Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
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Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
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