Unlike the elves in the fairy tale "shoes"
Manufacturer and Elf, "This elf will not tipto chew shoes or videos with his toes at night! Extremely low-frequency (ELF)
Radiation is at the center of an increasingly heated controversy related to the health risks used by computers.
And very low frequency (VLF)
The electric field and magnetic field, ELF radiation are emitted from the computer video display terminal (VDTs)
Video display unit (VDUs)
TV, for example.
Although the evidence of the risk is not clear, public attention has prompted an increase in funding research.
This paper provides an overview of the literature on computer security, major studies, health issues, legislation, technical guidelines, and steps to reduce VDT exposure in the workplace.
Basic knowledge of magnetic field (EMFs)
Including VLF and ELF fields, it is a product of electronic motion (
Such as wires and electrical appliances)
We have electricity everywhere.
Production of American power system 60-hertz (Hz)current;
That is, the current direction of communication is 60 times per second.
This leads to the fluctuation or rise and fall of the accompanying EMFs.
Whether it is electric or magnetic, the radiation accompanying this current is called 60-Hz radiation.
These fields exert force on objects, including biological organisms.
For example, the membrane is sensitive to weak magnetic fields, which may lead to changes in cell levels. (1)
The electric field is measured in units of volts per meter, while the magnetic field is measured in units of amps per meter, or more often Gaussian or milligaussian (mG).
While the entire ELF frequency range is between 0 and 1 000Hz, most health studies focus on 60-
Hz current, what US.
Power plants are powered by wires.
The range of VLF ranges from 1,000Hz to 500,000Hz.
Television and cathode optical tubes (CRT)
The video shows emitradation within the range of ELF and VLF.
There is a magnetic field on each side of the VDT.
This radiation is associated with the safun un that produces the image, as well as the power supply inside the VDTand, and will not be stopped by the monitor housing.
Measuring the strength of the ELF magnetic field is usually measured by a device called gaussmeter, which has no Gaussian.
The average ELF field strength of the computer VDT at a distance of 12 inch is 2 by using the gaosmeter measurement. 5 to 3. 5 mG. (2)
This number is compared to 0. 9 to 1.
3 feet mG, 3 in front of the TV screen.
Acar Front Seat 5 to 5 mg, more than 10 mg under the old electric blanket.
Median data from the recent Environmental Protection Agency (EPA)
The study showed that 5 mg from VDT to 12 inch, from copier to 12 inch of 20 mg. (3)
Ashcraft reported that the Sprite reading on the computer monitor was within a distance of about 1 20 inch. 0 mG. (4)
60-in residential, typical background-
The magnetic field is Hz. 1 to . 5 mG.
Average Speed of the Earth
The ground magnetic field is about 500 mg.
Most of this is constant current (DC)
However, unlike the field accompanying the AC current (AC).
Recently, New Mexico researcher Elaine mcallon measured the average field intensity of ELF radiation from 12 computer monitors at New Mexico State University (NMSU)Library.
A sample was selected from two public terminals
Service and office area.
Eight different brands were used to obtain the current variability.
However, these measurements are not designed to determine the difference between display types.
Digital reading meter (
Security technology company)
It is used to measure at the top 20 inch of the display with milligaussian.
The average radiation of the Elves is 5.
5 mG, 12 inch away from the screen, 1.
7 mg at a distance of 20 inch.
By comparison with the "Sweden" Standard 2.
5 mg at 20 inch, 2 units higher than this value (
The highest is 3. 04 mG)
And others below this value (The lowest is09mG).
Readings from the side, top and back of the device are generally higher than those from the front of the display.
When using a computer in a library environment, employees may be exposed to ELF radiation through a variety of computer applications on typical working days.
These include the use of OCLC terminals, PCs, online logs, and CD-
ROM and Lan (LAN)workstations.
The library also touches ELF-when using an online catalog or cd-
ROM/LAN workstation or public place-
Service area such as service desk.
More than ten years ago, the library literature raised concerns about the health impact of computer use.
Greg reviewed the literature and found ergonomic and visual problems related to computer use. (5)R.
Bruce Miller concluded that the radiation of the computer is small and dangerous, but be careful during pregnancy. (6)
He is also more concerned about the economy and vision.
He also described the difficulty of reviewing the literature in situations where most of the writing was not based on empirical evidence.
Today's library relies on the use of computers in many ways.
From ordering materials to catalogues, from finding reference information to communicating with colleagues via email, we can hardly use the computer.
In order to obtain the baseline number of the time we spent before the computer, for all full-
Staff of the NMSU Library.
The questionnaire asked each employee to record how many minutes he or she spent each hour of the working day before the computer terminal for three consecutive days in the second week of September 1993.
The survey was distributed to 70. five full-
Time staff of the Library; forty-five (60 percent)were returned.
The survey results show that many employees spend more than half of their working days before a video display unit.
Average time of 40 people at the dock
There were 3 respondents. 5 hours perday.
5 minutes to 7 minutes a day. 3 hours a day (average). The technical-Service personnel (
The highest average score was 4. 5 hours a day.
System Staff (4 respondents)averaged 4. 0 hours a day.
Collection Management including inter-library loan (
Five respondents), averaged 3. 3 hours perday.
Information services including reference and circulation (
Six respondents), averaged 3. 0 hours a day.
Administration (Five responses)averaged 2. 5 hours a day.
It should be noted that fewer units of respondents have a greater chance of error in this estimate.
Possible health effects life on Earth evolves with radiation from natural background levels, but exposure levels have increased dramatically in the past 100.
This growth is mainly achieved through the introduction of access networks for power and transmission lines, broadcast waves, electrical appliances and other equipment in the home and workplace.
It may be logical for some people
There is no harmful effect.
However, this conclusion is not scientifically proved.
Normal physical processes, such as ion exchange, movement of materials into cells, and nervous transmission, all involve low
Horizontal energy charge.
These processes may be sensitive to external EMFs.
Some types of radiation, such as X-
Ultraviolet rays, ultraviolet rays and radiation can cause ionization and destroy chemical bonds in cell molecules.
Exposed to such a high environment
Frequency Fields pose specific health risks, especially cancer. Lower-
Frequency ELF and VLF fields are non-
Ionization, do not know if there is a chemical bond.
Laboratory studies have shown that magnetic fields can disrupt transmission signals between nerves, interfere with replication of DNA and RNA transcription, induce changes in cell growth and rate of division, and reduce cancer
The ability to combat lymphocytes, increase birth defects in experimental animals, and interact with chemicals to promote the occurrence of tumors. (7)
Magnetic fields can also inhibit the production of melatonin.
This inhibition may lead to decreased immune response and may lead to cancer.
Some researchers are working on a long-term
Range animal experiments designed to determine whether radiation plays a role in the initiation and diffusion of cancer cells.
There is evidence of a statistical correlation between cancer and residential power lines.
Nancy Wertheimer and Ed Leeper reported on the first pieces of information released in this area, and they found a link between power line-launched EMFs and childhood leukemia and lymphoma. (8)
There is also evidence that women using electric blankets have higher rates of children than expected with braintum.
In contrast, other epidemiology studies found no association between leukemia and home EMFs or close to power lines.
Several occupational studies found that workers in occupations associated with exposure to high levels of EMFs were positively correlated with increased risk of cancer such as brain tumors and leukemia.
For example, telephone cable workers have a higher incidence of leukemia compared to other telephone company employees.
To date, no occupational studies have been found in the literature on the effects of magnetic fields on the health of library staff.
Medical conditions related to computer use are reported to include birth defects, miscarriage, cataract, menstrual cycle disorder, rash, fatigue and headache.
Complaints about vision problems and eye fatigue appear to be increasing.
Although the aKaiser permanent health maintenance organization study reported abortion among female VDT operators, no conclusions were reached on health risks for pregnant women.
Both the Kaiser Permanente HMO and the National Institute of Occupational Safety and Health are continuing to study the health impact of VDTs.
Recently, a study in Finland reported a correlation between the level of elf radiation in computer monitors and spontaneous abortion by users. (9)
The study was complex because no increase was found in the relationship between exposure to magnetic fields and increased health risks.
Instead, the effect can only be found in a specific "window" of the EMF field.
In addition, the results may become more complex due to the strength of the Earth's magnetic field.
This area can be changed by location, geological anomalies and even building materials.
Recently, there seems to be a major shift in the perception of researchers.
The current debate is not whether EMFs can cause biological effects, but the degree or threshold of harm.
Some authors raise public concerns about EM radiation and call on citizens to take action to prevent electricity pollution.
Seen by some as alarmist (
In fact, his 1989 book is called the status quo of death.
Paul Brodeur opposes research by so-called industry and government agencies trying to discredit and downplay the relationship between radiation and health risks. (10)Robert O. Becker (
Cross current 1990)
The natural electrical and magnetic phenomena in organisms and the relationship between organisms and nature and human beings are described.
Radiation field. (11)
He introduced the application of controlled electric fields or magnetic fields in fracture healing and the health risks of electrical pollution.
Electric Power Research Institute (EPRI)
Institute of Electrical and Electronic Engineers (IEEE)
Published a rebuttal and comment on brood's work.
However, EPRI takes this issue very seriously and has invested millions of dollars in research in this area.
It is interested in providing reasonable scientific research that will ultimately cost less than citizens fear to develop public policies on EMF exposure.
Over $20 million a year in public and private research on health effects of EMFstotals.
EMFs seems to have obvious biological effects, but although workers and researchers have been following the issue since the 1970 s, the associated dangers remain unknown.
Some government officials are now convinced that we must understand what the danger is.
However, there are differences even within government agencies.
A draft EPA report released in March 1990 suggested that the magnetic field be listed as a Class B carcinogenic substance, "possibly" as a human carcinogenic substance.
The director of the health and environmental assessment authority edited the word "possible" as "possible" in his final report ".
The White House science adviser even objected to the wording and attached a note in the report stating that there was not enough data to determine if there was a reason --and-
There is an effective relationship between magnetic fields and cancer.
Food and Drug Administration (FDA)
Microwave studies and recent elf studies were conducted at the equipment and Radiation Health Center.
It now operates one of the government's largest businesses.
Home ELF research projects, such as studying the electric and magnetic fields emitted by electric blankets and VDTs.
The Department of Energy is now the main government department.
Fund institutions that do research in this area, but there are other institutions involved.
The Environmental Protection Agency recently identified areas for research, and Congress passed the Energy Policy Act of 1992, authorizing the allocation of $65 million for further research within five years.
In short, there is a lot of ongoing research and exciting interest in this area.
Even though millions of dollars are being used again for creatures
Critics still assert that they are not doing enough due to the influence of the magnetic field.
Careful avoidance how should we deal with our relationship with VDTs and other radiation sources?
Most contemporary literature advocates "cautious avoidance ".
"In other words, we should avoid using magnetic fields without unnecessarily disrupting the way we live or work.
We should pay special attention to the situation where we spend a lot of time in a magnetic field such as the one next to the appliance.
For example, since we spend 1 out of 3 on the bed, we may not want an electric clock next to our head.
We may also question our use of electric blankets and water beds.
In litigation and legislation, some disputes over the health impact of the EMF were finally resolved in court.
Case of Houston Lighting & Power
Texas appeals court Klein Independent School District acknowledges safety risks exposed to electricity
Orderly repositioning of line fields and power lines.
In another case, a former Boeing electrician infected terminal leukemia after being exposed to a dangerous electric field, and he paid $500,000 in damages to all participants participating in the class action suit
Lawsuits by citizens protesting the routing of new power lines have led to rerouting by power companies and significant spending.
In addition, due to public concerns, the value of some properties located near the power line has declined.
Some legislative and regulatory efforts have been made to strengthen research, safety, public information and limit exposure to EM radiation.
At least seven states now limit the intensity of the electric field on the right edge --of-
At least two methods also limit the strength of the magnetic field near the transmission line.
In the 1980 s, the Federal Communications Commission issued rules restricting the number of radio computers.
However, this is not done to protect computer operators, but to prevent interference with airport control facilities.
Recently, the national magnetic field research and public information dissemination act was incorporated into the Integrated Energy Policy Act, which became federal law in October 24.
The bill requires the Minister of Energy to determine whether exposure to electric and magnetic fields affects human health.
This determination will be achieved through research efforts and the collection and evaluation of scientific information in order to be distributed to the public.
Europe has long been a leader in computer emissions safety research.
1987 National Commission for measurement and testing of Sweden (MPR)
The first guide on emissions from visualdisplay devices was established.
Revised guidelines (MPRII)
Regarding the level of magnetic fields and electric fields in the range of VLF and ELF, SWEDAC, the successor organization of bypr in 1991 (12).
These manuals describe the unified approach to testing VDUs as well as the emission value guidelines.
In short, the limit of the VDT radiation guide set by MPRIIsuggests is 2.
5 millivas 20 centimeters from the monitor.
However, these values are "not based on biological effects, but on what is technically possible.
While sometimes referred to as "Swedish standards", they are actually just suggested guidance values.
In a sense, however, these guidelines have become de facto standards, and many computer manufacturers now claim to comply with MPRII.
For consumers, the importance of having products that comply with these guidelines may be that manufacturers take precautions to do technically feasible things at reasonable costs.
Institute of Electrical and Electronic Engineers (IEEE)
Similar guidelines are also being studied, which will be the parable of MPRII.
It will establish technical limitations rather than security constraints, thus avoiding security issues that have not yet been addressed.
Some scholars believe that exposure to more than 1 msof Gaussian is dangerous to health.
By contrast, some people deny any danger under the age of 60. Hzfields.
What can the library do?
In order to reduce risks or meet the concerns of employees in a library environment, measurements can be made, Workspace can be rescheduled, purchase purchases and information sharing can be modified.
To determine the level of radiation you are dealing with, you may want to use agaussmeter for measurements.
Within the price range of $100 to $200, there are many commodities on the market.
Digital instruments are reported to be more accurate and reliable than analog instruments.
Your instrument is best read with a milligaussian, you should know if the meter is measuring the ELF or VLF magnetic field, or both.
To measure the radiation of the CRTs on TV and video displays, the gaosmeter should be sensitive to it. 01 mGs.
EllenSugarman proposed some measurement techniques. (13)
The most common measurement distance today is 20 centimeters.
Library staff who wish to be careful to avoid should be seated at least away from the computer monitor, 3 to 4 feet from the side and back of any VDT.
The work area should be arranged so that employees do not have access to fields from the side and back of the nearby VDTs.
Since the magnetic fields go through the walls, we should recognize what is outside of them. Computers (
Monitor at least)
Should be completely closed when not used;
Don't just dim the VDT or use the screen saver. Inpublic-
The same neighboring precautions should be taken in the service area, andat public-
Service Desk, customer and staff should all avoid leaning against the front, back, top or side of the VDTs.
Let me have a rest!
Due to the different nature of work in different areas of alibrary, there may be different approaches to careful avoidance.
For any work that requires the use of a computer terminal, it is recommended to take regular breaks or change work activities.
Library management can help reduce computers
By involving employees in decisions about workstations and providing them with current computers, relevant work pressures-
When buying a new monitor, there are many options to offer improved technology.
Radiation Safety guidelines should be taken into account for new computer purchases.
You may prefer to purchase a VDTs that specifically meets the MPRII guidelines.
The monthly display is subject to Swedish restrictions.
Although the price is slightly higher, 5 mg is now generally available.
Some peripheral devices, such as photocopiers and laser printers, should also be studied as sources of magnetic fields.
Although it can shield or interfere with electrical radiation, magnetic radiation is not so easy to improve.
Anti-glare and anti-static shielding does not provide anti-magnetic radiation, nordo dimming display, use screen protection programs, and even use lead shielding.
At present, the cost of renovation is very high and the technology is very difficult.
In addition, contrary to what is widely believed, some LCD displays may emit as much radiation as CRTs.
Some seemingly reasonable precautions are ineffective.
Many advertisements for computer radiation shielding ignore this, that is, although they can shield the electric field, they cannot protect the magnetic field.
It was even claimed that such suspicious safeguards, such as red lapels buttons and crystal pyramids, allegedly "neutralised" the magnetic field.
More than a decade ago, erly said, "At the moment, seniors seeking information on this issue must go beyond their normal professional reading. "(14)
This suggestion still seems to be correct today.
Many useful articles on this topic come from technical publications and non-professional literature.
There is no clear Library VDT-
Guidelines for use, no specific research or data on health effects of VDT
Used in library settings.
It is necessary to carry out such research and develop specific guidelines so that library staff and customers are fully protected by VLF and ELFfields.
There is no fairy-tale solution to this very real problem. Notes (1. )U. S.
Biological effects of Congress, the Office of Technical Assessment, power frequency electric fields and magnetic fields (WashingtonD. C. : GPO, 1989), 2. (2. )
Garbage Hacinli, "pull out the magnetic pollution", Garbage 4 (1992): 39. (3. )U. S.
Environmental Protection Agency, EMF in your environment: magnetic field measurement of daily electrical equipment (WashingtonD. C. : GPO, 1992), 20. (4. )
NERDC update, John Ashcraft, July/August 1993, "Is your computer monitor dangerous ? ". (5. )
Greg Byerly and Signe Lindell, library terminal, Library Magazine 107 (1982): 2147. (6. )R.
Bruce Miller, "radiation, ergonomics, ion exhaustion and VDTs: healthy use of visual display terminals", Information Technology and Library 2 (1983): 151-158. (7. )U. S.
Conference, biological effect of high-frequency electric field, 2,24-33;
Sarah Glazer, "Electric Fields: are they dangerous?
Editorial Research report 16 (1991):238-250. (8. )
Nancy Wertheimer and Ed Leeper, electronic line configuration and childhood cancer, Journal of American Psychology 109: 273-284. (9. )Maria-
Lisa Lindbohm, magnetic field and abortion of video display terminals, American Journal of Psychology 136 (1992): 1041-1051. (10. )
Paul Broad, the stream of death (
New York: Simon & Schuster, 1989). (11. )Robert O.
Becker, cross current: promise of electric medicine, danger of electric pollution (
Los Angeles: Jeremy P. Tarcher, 1990). (12. )
User manual for evaluating visual display units (
Sweden, Bolas: Sweden, 1990).
For information on how to get these guidelines, MPRII, please call the Southwest code and Standards Center of New Mexico State University (505)646-6834. (13. )
Alan Sugarman warns that electricity around you may have an impact on your health (
New York: Simon & Schuster, 1992). (14. )
Byerly and Lindell, "terminals in the library," 2146.