STENGEL@pucc.Princeton.EDU (Robert F. Stengel) (02/12/91)
Inadvertently, I conducted an experiment relating to the on-going controversy regarding possible health effects of low-level electric fields and video data terminals (VDT). My new Macintosh LC computer is parked unceremoniously in the middle of my desk until I can find a better place for it. The dual-15w-tube fluorescent desk lamp that has served me well for 30+ years sits overhead, usually well out of the way. The lamp has separate "on" and "off" buttons; the "on" button must be held down to produce a higher electric field during the starting cycle. Recently, while sorting some 35mm slides, I pulled the lamp head closer to the desk top, just a few inches above the monitor screen. When I turned the computer on, the lamp tube nearest to the monitor began to fluoresce, flickering until the "off" button produced total discharge. Apparently, the electric pulse that occurred when the monitor was turned on was enough to initiate fluorescence in the lamp. The phenomenon has been repeated several times since. In the popular reporting on the subject, much has been made of average field strengths and possible repercussions on health, but little or no attention has been paid to peak transient fields, which could be expected to have increased effect. It may well be that the VDT presents a greater hazard as it is being turned on than while it is operating normally. Increased understanding of this potentially significant factor is warranted.
jmc@DEC-Lite.Stanford.EDU (John McCarthy) (02/12/91)
Possibly the interaction between the VDT and the fluorescent lamp was via the power line.
kludge@grissom.larc.nasa.gov ( Scott Dorsey) (02/12/91)
In article <12438@pucc.Princeton.EDU> STENGEL@pucc.Princeton.EDU writes: > Recently, while sorting some 35mm slides, I pulled the lamp head closer >to the desk top, just a few inches above the monitor screen. When I turned >the computer on, the lamp tube nearest to the monitor began to fluoresce, >flickering until the "off" button produced total discharge. Apparently, the >electric pulse that occurred when the monitor was turned on was enough to >initiate fluorescence in the lamp. The phenomenon has been repeated >several times since. First of all, since the pulse only occurs for a short period of time, the exposure (which is cumulative anyway) is quite slight. Secondly, the exposure from VDTs may be one of the less important elements in the environment. I have shared offices with 250 KW transmitters where fluorescent lights would burn a bright white while unplugged and held in the hand, and caused small sparks to jump off the corner of my glasses if the sharp edges were not rounded with a file. Currently I am across the street from a radar set which causes a noticeable flicker on fluorescent lamps and disconnected CRTs every time the beam sweeps in my direction. VDT exposure is in the sub-microvolt/m2 range, but there are a lot of environments where people live and work in the tens of volts/m2 range. AC power lines are a contributor to the exposure, and while the actual field strength produced by AC lines is quite small in most cases, the lower frequencies may possibly be more hazardous. Personally, I wouldn't worry about it. But it's a matter that certainly does deserve more study. --scott
mmm@cup.portal.com (Mark Robert Thorson) (02/13/91)
I'll bet the high voltage of the monitor was causing the flourescent light to glow. I've found that a neon bulb can often be made to glow by holding it near a TV set. This is a totally harmless effect, unrelated to the controversy about EM fields generated by VDT's and other devices. In particular, color monitors use very high voltages (about 25,000 volts) and at these high voltages some small amount of the electricity is discharged into the air.
jones@sj.ate.slb.com (Clark Jones) (02/13/91)
In article <12438@pucc.Princeton.EDU> STENGEL@pucc.Princeton.EDU writes: [stuff deleted] > In the popular reporting on the subject, much has been made of average >field strengths and possible repercussions on health, but little or no >attention has been paid to peak transient fields, which could be expected to >have increased effect. It may well be that the VDT presents a greater >hazard as it is being turned on than while it is operating normally. >Increased understanding of this potentially significant factor is warranted. And the designers of this equipment, in their infinite wisDUMB, put the on/off switches on the _BACK_ so you've got to get "up close and personal" to turn the thing on or off! BTW, you didn't mention whether the VDT in question is a monochrome or color. For many years, standard design of color CRT circuits has included a "de-gausser", which applies a decaying line-frequency magnetic field to the tube to eliminate residual magnetic fields (which would interfere with the image displayed). This is applied to the face end of the tube. Clark Disclaimer: The opinions expressed above are mine and not those of Schlumberger because they are NOT covered by the patent agreement!
jfa0522@hertz.njit.edu (john f andrews ece) (02/18/91)
While on the topic of EM fields and vdt's, can anyone point me to a source for
information on health effects of em fields? I have a few callers interested,
and would like to repost whatever I can find for wider dissemination.
Thanks for any comments.
-----------------------------------------------------------------------------
john f andrews SYSOP The Biomedical Engineering BBS
24 hrs 300/1200/2400 (201) 596-5679
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INTERNET jfa0522@hertz.njit.edu LabRat@faraday.njit.edu CIS 73710,2600
-----------------------------------------------------------------------------Paul.Heller@f421.n109.z1.fidonet.org (Paul Heller) (02/19/91)
jf> While on the topic of EM fields and vdt's, can anyone point me to a so
jf> for
jf> information on health effects of em fields? I have a few callers inter
jf> and would like to repost whatever I can find for wider dissemination.
Here's an item that came over one of the local ham radio packet
bulletin boards today:
--------------
Path: N4QQ!KD3DE!KE2M!WB2MNF!K2ADJ!KB4CYC!KB1BD!N2DSY!KD6TH Date: 18
Feb 91 04:37:32 Z From: n2irz@kd6th.nj.usa.na (Don ) To:
ALL@NJNET Subject: 60 Hz = Leukemia
Message-ID: <50616_KD6TH> To: all@njnet
The following is the complete text of an article appearing in "The
Record", a large daily newspaper based in Hackensack, NJ, on Feb. 9,
1991 on Page D-8.
- - - - - - - - - - - - - - - - - - - - - The Associated Press
LOS ANGELES - Children may face twice the risk of getting leukemia
if they live near power lines, frequently use hair dryers, or watch
black-and-white television, a study sponsored by electric utilities
indicates.
The findings offer "considerable support for a relationship between
children's electrical appliance use and leukemia risk," said a summary
of the study by the University of Southern California.
The USC study of 464 Los Angeles County children ages 10 and
younger is considered important because it was financed by the
Electric Power Research Institute.
The utility organization in Palo Alto had been skeptical of earlier
studies linking cancer to electromagnetic fields.
The study will "raise general national concern about the role of
electric and magnetic fields in causing cancer," Dr. David Carpenter,
dean of public health at the State University of New York in Albany,
said in Friday's Los Angeles Times.
The institute, however, said no single study can settle the
controversy over electrical and magnetic fields, which are emitted by
every wire and device that carries current.
Dr. John Peters, director of USC's occupational health division,
outlined his team's preliminary findings on Thursday during a
closed-door scientific meeting in Carmel, Calif.
The university issued a statement saying the scientists would
refuse to discuss the results until they are reviewed by other
researchers and published in a scientific journal in about four
months.
But, in an unusual step, the institute released two summaries of
Peter's findings. One was on USC letterhead, the other written by the
institute.
Half the children in Peter's study developed leukemia between 1980
and 1987. They were compared with a similar group of children without
leukemia.
The study found children who live closest to neighborhood power
lines were up to 2 1/2 times more likely to suffer leukemia - a
finding consistent with earlier studies conducted in Colorado.
[END OF ARTICLE]
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Something to think about, especially if you live near high-tension
wires.
Also, of particular importance to the Amateur community, previous
studies have shown that the effects of electromagnetic fields increase
at higher frequencies. Shield all of your equipment, and move
anything running higher power (over 100 Watts or so) as far away from
your operating position as possible. Even an electric blanket can be
a source of EM fields.
An recent editorial in "73 Amateur Radio Today" raised some
additional points regarding EM fields, and precautions to take. As a
matter of fact, I remember another editorial in 73 less than 2 years
ago that dealt with the subject in great detail.
Even though you can't feel anything, there's a chance that an EM
field is doing wierd things to your body. Precautions are cheap - I
urge you to investigate further and take action to protect yourself
and those you love.
Feedback is welcomed.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* 73 de Don Rotolo * Every private citizen has a *
* N2IRZ@kd6th.nj.usa * public responsibility. *
* CIS : 73227,2644 * -Myra Janco Daniels in "Newsweek" *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
------------- End of re-posted message ...
--
Paul Heller, Paul.Heller@f421.n109.z1.fidonet.org
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