The Risks Digest

The RISKS Digest

Forum on Risks to the Public in Computers and Related Systems

ACM Committee on Computers and Public Policy, Peter G. Neumann, moderator

Volume 14 Issue 70

Friday 4 June 1993


o Re: Did they have an address for Hillary?
Olivier MJ Crepin-Leblond
Sidney Markowitz
o Health effects of VDTs - an update
Kenneth R Foster
o Info on RISKS (comp.risks)

Re: Did they have an address for Hillary?

Olivier MJ Crepin-Leblond <>
Fri, 4 Jun 1993 19:43:37 +0100
Paul Robinson (TDARCOS@MCIMAIL.COM) writes:

> I wanted to see if there was anything:
> % telnet
> telnet> open 25
> Trying ...
> Connected to
> Escape character is '^]'.
> 220 SMTP/smap Ready.
> helo
> 250 Charmed, Im sure.
> vrfy hillary
> 250 <hillary>
> "250" in this case, is an "ok" indicating the mail-server receiving
> the request considers the address to be valid.  So try that, then:

Alas, this will most probably not work.
If you type

vrfy foobar
250 <foobar>
vrfy tdarcos
250 <tdarcos>          [ Eh Paul ? Didn't know you worked there :-) ]


In fact, anything is accepted by the mailer, so that no new address can be
traced before it is officially released. A finger request at that site returns
a standard message; a "rup" of that site (to see "if the President is busy
reading your beloved messages" :) returns a "port mapper failure".

Still not ready to give up ?

Okay, how about trying "talk" ?
The reply is: "No talk daemon on requested machine"

I leave it to RISKS readers to find out if
is on Internet Relay Chat (IRC).  :-)

Olivier M.J. Crepin-Leblond, Digital Comms. Section, Elec. Eng. Department
 Imperial College of Science, Technology and Medicine, London SW7 2BT, UK
       Internet/Bitnet: <> - Janet: <>

  [Also noted by (Bill Brykczynski)
     Dave Bachmann <>
     tep@SDSC.EDU (Tom E. Perrine)
     Frederick W. Wheeler <>
     "Jonathan I. Kamens" <>
     Pat Place
     Jerry McCollom <>
     "Albert Peters" <albert@cs.Stanford.EDU>
     Peter J. Scott <pjs@euclid.Jpl.Nasa.Gov>  ]

Re: Hillary's e-mail address

Sidney Markowitz <>
Fri, 4 Jun 93 14:59:19 -0700
Someone in the White House must be paying attention to RISKS Digest.

In RISKS-14.69, Paul Robinson showed

<> telnet> open 25
<> vrfy hillary
<> 250 <hillary>

I just tried it and got back

 500 Command unrecognized

It looks like they sealed off this possible security risk.

  [Also noted by "Albert Peters" <albert@cs.Stanford.EDU>.
  Perhaps we need to add the White House to the RISKS LIST!  PGN]

health effects of VDTs - an update

Kenneth R Foster <>
Wed, 2 Jun 93 09:30:24 -0400
I am uploading a chapter from our new book Phantom Risk: Scientific Inference
and the Las (MIT Press June 1993, Foster, Bernstein, Huber, eds.)  Hopefully
it adds something to the public concern about health effects of VDTs - and
maybe some users will buy the book!  K. R. Foster

             K. R. FOSTER, D.E. BERNSTEIN, P. W. HUBER, EDS.
                           MIT PRESS JUNE 1993

           Miscarriage and Video Display Terminals:  An Update

                            Kenneth R. Foster
                         Dept. of Bioengineering
                               Univ. of PA
                             Phila. PA 19104

The link between miscarriages and use of video display terminals (VDTs) became
a public issue around 1980 with the reports of clusters of reproductive
mishaps in women users of VDTs.  In 1986 I traced the development of the VDT
debate (Foster 1986).  Now, six years later (and a decade after the
controversy began), I describe the current state of the issue.
     All together, about a dozen clusters were reported.  These included 7
adverse outcomes of 8 pregnancies at the offices of the solicitor general in
Ottawa; 10 out of 19 at the offices of the attorney general in Toronto; 7 of
13 at the Air Canada offices at Dorval Airport, Montreal; 8 of 12 at Sears,
Roebuck in Dallas, Texas; 10 of 15 at the Defense Logistics Agency in Atlanta;
3 of 5 at Pacific Northwest Bell in Renton, Washington; and 5 of 5 at Surrey
Memorial Hospital in Vancouver.  The problems included birth defects,
spontaneous abortions, respiratory problems in the newborns, Down's syndrome,
spina bifida, and premature birth.
     Despite attempts by health authorities to investigate the matter, the
clusters were never adequately explained.  I have been able to locate reports
of a follow-up investigation by the U.S. Army Environmental Hygiene Agency of
the cluster at the Defense Logistics Agency (Tezak 1981), and by the Centers
for Disease Control (1981) of the cluster at Sears, Roebuck.  Both verified
the existence of a cluster; neither established any apparent link to the
women's use of VDTs.
     The interpretation of a cluster is problematic.  Any unexpected grouping
of problems (a cluster) may indicate some problem of public health
significance.  More commonly, investigation by health authorities of a
reported cluster fails to identify a problem that can be remedied by public
health measures.  However tragic the outcomes may be to the people involved,
the grouping of cases may have been a statistical event with no epidemiologic
significance.  Roughly one pregnancy in five ends in spontaneous abortion (the
reported rates vary widely, depending on how early pregnancy is diagnosed);
roughly one child in a hundred is born with a major birth defect.  Simple
calculations will show that many clusters will occur every year among the 10
million North American women who use VDTs.  The issue, so easily raised, took
a decade to resolve.
     In the remainder of this chapter, I will summarize two lines of evidence
related to the possible reproductive risks from use of VDTs.  The first is the
many studies on possible teratological effects of electromagnetic fields; the
second is the series of progressively more sophisticated epidemiologic studies
searching for a possible link between adverse pregnancy outcomes and use of

Electromagnetic Fields

Public concern about VDTs has focused on several factors.  As judged by
contemporary newspaper articles, initial fears concerned possible X-ray
emissions from the terminals, no doubt reflecting the scare in the late 1960s
about X-ray emission from color television sets (Foster 1986).  However,
measurements by several government agencies on thousands of terminals showed
that X-ray emissions are extremely low and in the overwhelming majority of
cases are unmeasurable (Zuk et al. 1983).  Emissions of ultraviolet, visible,
and infrared radiation are also small, and far below recommended exposure
limits.  VDTs produce no measurable microwave radiation, notwithstanding one
early (incorrect) report by an investigator to the contrary.
     In their coverage of the issue, the lay media has frequently mentioned
possible effects of low-frequency magnetic fields that are present near the
terminals.  These fields include components at power-line frequency (50-60 Hz)
associated with the power supply, and fields with a more complex time
dependence from the coils that move the electron beam around the screen.
     The power-frequency fields from VDTs are comparable with those from other
appliances; at a distance of 30 cm from the terminal, typical field strengths
are a few v/m (electric field) and 4-7 Mg (magnetic flux density) (Jokela et
al. 1989).
     The fields from the beam deflection coils are more complex.  If displayed
on an oscilloscope, they would resemble a sawtooth wave with a repetition
frequency of approximately 20 Khz (for the coils responsible for horizontal
beam movement) and 60 Hz (vertical motion).  The field from the vertical
deflection coil has a peak amplitude of about 10-15 Mg at a distance of 30 cm
from the screen (Jokela et al. 1989); that from the horizontal deflection coil
is smaller but at a higher frequency.  The corresponding electric field
strength is typically a few volts per meter at a distance of 30 cm from the
terminals.  These field strengths are far below the levels associated with
known hazards of electromagnetic fields (excessive heating of tissues or nerve
excitation and shock) and far below recommended exposure limits.

In Vitro and In Vivo Studies

Two lines of evidence are related to the question of possible reproductive
risk from VDTs: animal studies and epidemiologic observations on human
populations.  I consider the first and most confusing of these: animal tests
for possible teratogenic effects of low-frequency magnetic fields.
     In 1982 Delgado and colleagues reported that chicken eggs exposed to
pulsed magnetic fields showed a striking number of malformations in the
embryos inside (Delgado et al. 1982; Ubeda et al. 1983).  The fields were
comparable in strength with those from VDTs but weaker than the earth's
magnetic field.  Further, the investigators claimed, small changes in the
waveshape of the field made a large difference in the rate of the
malformations that were induced.  Four independent attempts to confirm the
findings were unsuccessful (Maffeo et al. 1984; Stuchly et al.  1988;
Sandstrom et al. 1986; Sisken et al. 1986).
     Delgado's findings were widely reported in the lay media, often with
speculation about their possible significance to hazards from fields from VDTs
and other appliances.  The unsuccessful attempts at replication received
little media attention.

Project HenHouse

To address the questions that the Delgado studies raised, the US Office of
Naval Research commissioned at great expense a multi- laboratory replication
of the original study, under the name Project HenHouse.  Six laboratories in
the United States, Canada, and Europe conducted replicate experiments, using
the same techniques, identical exposure apparatus, and precisely measured
fields (Berman et al. 1990).  Each experiment involved the exposure of
fertilized chicken eggs to pulsed magnetic fields, and subsequent examination
of the embryos.
     The outcome of Project HenHouse was very puzzling.  Four of the
laboratories--including that of colleagues of Delgado--found no statistically
significant differences in the rate of malformations in the exposed versus
control eggs.  A fifth laboratory reported a borderline-significant increase.
The sixth reported a statistically significant increase (but a smaller one
than originally reported by Delgado et al.).  If the results of all six
studies are combined, they indicate a borderline significant increase in rate
of malformations in the exposed eggs--in contrast with the very striking
effect originally reported by Delgado et al. (Berman et al. 1990).
     Thus, the results of Project HenHouse were neither clearly positive nor
clearly negative.  The simplest interpretation is that five of the six studies
were negative, and that the one positive study was different in some important
respect from the other five.  Whether the sixth was in error or whether there
is something important in its results is a question that cannot at present be
     The latest development in this episode is the preliminary report by
Litovitz et al. (1992) of a teratogenic effect of weak magnetic fields on
chicken eggs.  Litovitz claimed that the critical variable of exposure is the
"coherence" of the field.  As of this writing these results have not been
published; whether they will be confirmed and accepted by other scientists
remains to be seen.
     In retrospect, Delgado's study probably did not merit the widespread
attention it received.  The biological system (fertilized chicken eggs)
differs too much from human embryos for the test to have much value for risk
assessment; on the other hand it is too complex to be of much use for basic
scientific research on mechanisms of interaction of fields with a biological
systems.  Chickens are not inbred, and are notoriously variable in the
frequency of chick malformations and fertility of eggs.  Finally, a project
officer from the Office of Naval Research who visited Delgado's lab (Thomas C.
Rozzell, private communication) told me that the initial experiment was
crudely done and the applied fields were poorly characterized.
     After ten years of research on the "Delgado effect" with so little to
show for it, funding agencies and most scientists have lost interest in the
matter.  As well they should.

Other Animal Studies

Since the early 1980s, at least 17 animal studies have been searched for
effects of pulsed magnetic fields on animal embryos.  (Berman 1990 provide a
comprehensive review.)  The literature is very inconsistent, with some studies
reporting effects and others (including attempts to replicate earlier positive
findings) finding none.  Berman concludes
     ... we cannot clearly relate an increase in the
     incidence of abnormal embryos resulting from exposure
     to pulsed magnetic fields to any patterns of pulse
     frequency, field intensity, pulse shape, or rate of
     change in the intensity.... Until the important
     variables in pulsed magnetic fields are determined and
     the mechanism of effects is identified, it may not be
     possible to extrapolate such effects to humans. (1990, p. 47).

     This conflates two issues.  The first is the absence of any clearly
reproducible phenomena.  Until some reproducible phenomenon appears, with some
defined relation between dose and response, that can be consistently observed
by independent investigators, it will be difficult to draw any conclusions
from the data.  The second is the relevance of these results to human health,
assuming that the effects themselves are real.  That depends on the biological
similarity between the animal subjects and humans, the exposure conditions,
and other factors.  Whether these studies will point to a mechanism for human
injury is, at present, a matter of speculation.

Epidemiologic Evidence

A much clearer picture has emerged from the epidemiologic studies.  By now, a
dozen epidemiologic studies have been conducted in the United States, Canada,
Finland, Sweden, and elsewhere on reproductive problems associated with use of
VDTs.  (A good, but dated, review is Blackwell and Chang 1988.)  They have
been overwhelmingly--but not totally--negative, finding no links between use
of VDTs and spontaneous abortion or birth defects.
     The studies vary widely in their methods, and I will not review them in
detail here.  Table 6.1 summarizes their results in terms of the relative
risk, which is the risk (probability) of an undesired consequence in a VDT
user, divided by the probability of the same consequence for an otherwise
similar nonuser (see chapter 1).  The table also shows the 95 percent
confidence intervals, i.e. margins of sampling error in the studies.
Virtually all of the results indicate no increase in risk associated with use
of VDTs.  But some of these studies did report positive or equivocal findings,
which has helped to keep the issue alive.  The most widely publicized of these
studies was that of Goldhaber et al. (1988), who reported a 1.8-fold increase
in risk of miscarriage among women who worked with VDTs for more than 20 hours
a week during their first trimester of pregnancy.  This increase was at the
edge of statistical significance.
     Goldhaber's study was generally well done, but it had one major weakness
that resulted from its retrospective design.  To determine the subjects' use
of VDTs during pregnancy, the investigators sent them a questionnaire, as much
as three years after their pregnancies.  The investigators did not
independently verify the subjects' actual use of the terminals.  At the time
the study was conducted, the possible reproductive hazards of VDTs were well
publicized; it is likely, as the investigators themselves suggested, that
women with adverse pregnancy outcomes might have been more likely than other
women to report using VDTs.  Goldhaber's study was widely reported in the lay
media, without the careful reservations of the investigators, and usually
without mention of the negative findings of the other studies.
     The most recent, and undoubtably the best, study on reproductive risk of
VDTs was published early in 1991 in the New England Journal of Medicine by
Schnorr and colleagues.  The investigators, working for the National Institute
for Occupational Safety and Health (NIOSH), conducted a retrospective cohort
study that compared groups of telephone operators who used VDTs with telephone
operators in otherwise similar jobs who did not.  The investigators found no
link between spontaneous abortion and use of VDTs during the first trimester
of pregnancy.  Whether this study will end the VDT debate remains to be seen.
     The epidemiologic literature on the VDT-miscarriage question frequently
mentions the great difficulty of measuring reproductive risk.  These problems
are not reflected in the 95 percent confidence intervals in the table, which
show only the statistical uncertainties due to sampling error.
     For example, several of the papers listed in the table discuss at length
the problem of reporting bias, which might be introduced if not all of the
subjects in a study were equally likely to report use of VDTs during their
pregnancies.  Two studies (Goldhaber et al. 1988; McDonald et al. 1988)
mentioned this as a possible explanation for a small apparent excess of
miscarriages among VDT users.
     Another problem is the difficulty of reliably detecting miscarriages that
occur early in pregnancy.  Because of this difficulty, an investigator has a
choice of including only miscarriages that occur after a month or more of
pregnancy (and thus missing a large fraction of all miscarriages), or of
including earlier miscarriages and finding some way to determine precisely
when the subjects became pregnant.  Most studies choose the former approach.
     A final difficulty arises from the many different birth defects that can
occur.  A study that retrospectively examines medical records for any
association between birth defects and use of VDTs can, therefore, make many
different comparisons.  However, by the statistical tests that most scientists
adopt, 1 comparison out of 20 will show a difference that is statistically
significant--even if there is no real difference in the groups being compared.
(This problem is discussed in chapter 1, and again in chapter 4.)
     Because of these and other problems, one can never achieve complete
consistency in epidemiologic studies--but the dozen studies summarized in the
table come pretty close.  They certainly rule out the large increases in risk
that some people inferred from the clusters.
     Recently, public concern has shifted to the much more difficult question
of possible risks from the fields associated with the terminals, which these
studies do not directly address.  In the NIOSH study, for example, both the
VDT and non-VDT operators were exposed to similar levels of 60 Hz
electromagnetic fields from the equipment they used.  Consequently, the study
is inconclusive on the question of hazard from fields.  This point was raised
in a letter to the editor of Science News from the president of a company that
makes radiation shields for VDTs (Doilney 1991).
     An adequate epidemiologic study on reproductive risk from 60 Hz fields
from VDTs would be very hard to mount.  The NIOSH investigators measured the
fields from the terminals, and found them to be comparable to those from many
other sources in the environment.
     The latest development in this issue is a preliminary report of a Finnish
epidemiologic study (Hietanen et al. 1992) of a 3.5- fold increase in risk of
miscarriage in VDT operators who were exposed to extremely low frequency
magnetic fields greater than 9 Mg from the terminals.  The study has not been
published as of this writing and there is no way to judge its quality; perhaps
the issue of reproductive risk from VDTs will remain alive.
     Other Problems Associated with Use of VDTs Of greater concern to many
scientists and health authorities have been diverse ergonomic and psychosocial
problems associated with the use of computers in the workplace (World Health
Organization 1989).
     Ergonomic problems include workstation design, glare, legibility of
display, seating, and keyboard height.  A panel assembled by the U.S. National
Research Council judged radiation hazards to be highly unlikely, and focused
in its report on issues such as glare, legibility of video displays, and
background lighting (National Academy of Sciences 1983).
     Perhaps more important still are psychosocial problems.  To my mind the
fundamental problem is that many clerical workers using VDTs simply have lousy
jobs.  A data entry operator who spends the day keying numbers into a
computer, with every keystroke counted, little opportunity for personal
interaction, and rigid performance standards to meet might well experience
emotional and perhaps physical problems.  If only radiation shielding could
fix such problems!
     Carpal tunnel syndrome (CTS) is a painful condition associated with
repetitive motions of the hand, that afflicts workers in many occupations,
including VDT operators.  CTS arises from compression of the median nerve as
it passes through a small opening (the carpal tunnel) in the wrist (Spinner et
al. 1989); and can be relieved by a simple operation.  The problem has been
reported among workers in diverse occupations, including meat cutting and
clerical workers, but there are few reliable data on its incidence and the
medical literature on CTS is sketchy and anecdotal.  The syndrome is clearly a
matter of concern to VDT operators and their employers, and might be prevented
by better keyboard design or other ergonomic considerations.  Clearly, more
study on CTS is needed.
     Other, less well defined, health problems have been reported from use of
VDTs (Bergqvist 1989; Council on Scientific Affairs 1987).  Since the
mid-1980s, there have been scattered reports of rashes and other skin problems
among VDT users; follow-up studies have been unable to find the cause of the
problem or associate it with the terminals or other factors in the office
environment.  This has, however, led to at least one lawsuit (see "The Legal
Context" at the end of Part I).
     On reviewing the history of the VDT debate, I am struck by the great
disparity between the ease with which concerns about reproductive hazards from
the terminals were raised, and the great difficulty in adequately addressing
them.  The clusters, in retrospect, were probably chance events of no
epidemiologic significance.  But the question of whether use of VDTs increases
reproductive risk took ten years and a dozen studies to address, and (from a
recent preliminary report) it has still not been settled.  It is time to focus
instead on the more serious ergonomic and psychosocial problems associated
with use of computers in the workplace.


Berg, M.  1988.  Skin problems in workers using visual display terminals--a
study of 201 patients.  19 Contact Dermatitis 335- 341.

Bergqvist, U.  1989.  Possible health effects of working with VDUs.  46 Br. J.
Indus. Med. 217-221.

Berman, E., L. Chacon, D. House, B. A. Koch, W. E. Koch, J. Leal, S. Lovtrup,
E. Mantiply, A. H. Martin, G. I. Martucci, K. H.  Mild, J. C. Monahan, M.
Sandstrom, K. Shamsaifer, R. Tell, M. A.  Trillo, A. Ubeda, and P. Wagner.
1990.  Development of chicken embryos in a pulsed magnetic field.  11
Bioelectromagnetics 169- 187.

Berman, E.  1990.  The developmental effects of pulsed magnetic fields on
animal embryos.  4 Repro. Toxicol. 45-49.

Blackwell, R., and A. Chang.  1988.  Video display terminals and pregnancy.  A
review.  95 Br. J. Obstet. & Gynaecol. 446-453.

Brandt, L. P. A., and C. V. Nielsen.  1990.  Congenital malformations among
children of women working with video display terminals.  16 Scand. J. Work
Environ. & Health 329-33.

Bryant, H. E., E. J. Love.  1989.  Video display terminal use and spontaneous
abortion risk.  18 Int. J. Epidemiol. 132-8.

Butler, W. J., and K. A. Brix.  1986.  Video display terminal work and
pregnancy outcome in Michigan clerical workers.  In Allegations of
reproductive hazards from VDUs.  Nottingham UK: Humane Technology 67-91.

Centers for Disease Control, Family Planning Evaluation Division.  981.
Cluster of spontaneous abortions.  Report EPI-80-113-2.

Council on Scientific Affairs.  1987.  Health effects of video display
terminals.  257 J. Am. Med. Assn. 1508-1512.

Delgado, J. M. R., J. Leal, J. L. Monteagudo and M. G. Gracia.  1982.
Embryological changes induced by weak extremely low frequency electromagnetic
fields.  134 J. Anat. 533-551.

Doilney, J. A.  1991.  Science News 387.  June 22.  Letter to the editor.

Ericson, A., and B. Klln.  1986.  An epidemiological study of work with
video screens and pregnancy outcome: II.  A case- control study.  9 Am. J.
Indus. Med. 459-475.

Foster, K. R.  1986.  The VDT debate.  74 Am. Scientist 163-168.

Goldhaber, M. K., M. R. Polen, and R. A. Hiatt.  1988.  The risk of
miscarriage and birth defects among women who use visual display units during
pregnancy.  13 Am. J. Indus. Med. 695-706.

Hietanen, M., M. L. Lindbohm, P. von Nandelstadh, P. Kyyrnen, and M.
Sallmn.  1992.  Effects of exposure to magnetic fields of VDTs on
miscarriages (abstr), 1st Congress of the European Bioelectromagnetics
Association, Brussels, Belgium.  January.

Jokela, K., J. Aaltonen, and A. Lukkarinen.  1989.  Measurements of
electromagnetic emissions from video display terminals at the frequency range
from 30 Hz to 1 Mhz.  57 Health Physics 79-88.

Edstrm, R., and B. Klln.  1985.  Dataskarmsarbete och graviditet.  82
Lakartidningen 687-688.

Kurppa, K., P. C. Holmberg, K. Rantala, and T. Nurminen.  1984.  Birth defects
and video display terminals, 2 The Lancet 1339.

Kurppa, K., P. C. Holmberg, K. Rantala, T. Nurminen, and L. Saxen.  1985
Birth defects and exposure to video display terminals during pregnancy.  11
Scand. J. Work Environ. Health 353-356.

Maffeo, S., M. W. Miller and E. L. Carstensen.  1984.  Lack of effect of weak
low frequency electromagnetic fields on chick embryogenesis.  139 J. Anat.

Mackay, C. J.  1989.  Work with visual display terminals: psychosocial aspects
and health.  31 J. Occup. Med. 957-968.

McDonald, A. D., N. M. Cherry, C. Delorme, and J. C. McDonald.  1986.  Visual
display units and pregnancy: evidence from the Montreal Study.  28 J. Occup.
Med. 1226-1231.

McDonald, A. D., J. C. McDonald, B. Armstrong, N. Cherry, A. D.  Nolin, and D.
Robert.  1988.  Work with visual display units in pregnancy.  45 Br. J. Indus.
Med. 509-515.

Miller, D. A.  1974.  Electric and magnetic fields produced by commercial
power systems.  In J. G. Llaurado, A. Sances, and J.  H. Battocletti, eds.,
Biologic and clinical effects of low-frequency magnetic and electric fields
62-70.  C. Thomas.

National Academy of Sciences.  1983.  Video displays, work, and vision.
Washington DC: National Academy Press.

Nurminen, T., and K. Kurppa.  1988.  Office employment, work with video
display terminals, and course of pregnancy.  Reference mothers' experience
from a Finnish case-referent study of birth defects.  14 Scand. J. Work
Environ. Health 293-298.

Sandstrom, M., K. H. Mild, and S. Lovtrup.  1986.  Effects of weak pulsed
magnetic fields on chick embryogenesis.  In Proceedings of the International
Scientific Conference: Work with video display units 60-63.  Stockholm:
Swedish National Board of Occupational Safety.

Schnorr, T. M., B. A. Grajewski, R. W. Hornung, M. J. Thun, G. M.  Egeland, W.
E. Murray, D. L. Conover, and W. E. Halperin.  1991.  Video display terminals
and the risk of spontaneous abortion.  324 N. Eng. J. Med. 727-733.

Sisken, B. F., C. Fowler, J. P. Mayaud, J. P. Ryaby, J. Ryaby, and A. Pilla.
1986.  Pulsed electromagnetic fields and normal chick development.  5 J.
Bioelec. 25-34 (1986).

Slesin, L., and M. Zybko.  1983.  Video display terminals: Health and safety.
New York: Microwave News 41-46.

Spinner, R. J., J. W. Bachman, and P. C. Amadio.  1989.  The many faces of
carpal tunnel syndrome.  64 Mayo Clinic Proc. 829-836.

Stuchly, M. A., et al.  1988.  Teratological assessment of exposure to
time-varying magnetic field.  38 Teratology 461-466.

Ubeda, A., J. Leal, M. A. Trillo, A. Jimenez, and J. M. R.  Delgado.  1983.
Pulse shape of magnetic fields influences chick embryogenesis.  137 J. Anat.

Tezak, R. W.  1981.  Investigations of adverse pregnancy outcomes.  Service
Report 66-32-1359-81.  Aberdeen Proving Ground MD: U.S. Army Environmental
Hygiene Agency, Defense Contract Administration.

Wahlberg, J. E., and C. Lidn.  1988.  Is the skin affected by work with
visual display terminals?  6 Occup. Dermatoses 81-85.

Westerholm, P., and A. Ericson.  1987.  Pregnancy outcome and VDU-work in a
cohort of insurance clerks.  In B. Knave, P. G.  Widebck, eds., Work with
display units 86, at 87-93.  Amsterdam: Elsevier.

Windham, G. C., L. Fenster, S. H. Swan, and R. R. Neutra.  1990.  Use of video
display terminals during pregnancy and risk of spontaneous abortion, low
birth-weight, or intrauterine growth retardation.  18 Am. J. Indus. Med.

Zuk, W. M., M. A. Stuchly, P. Dvorak, and Y. Deslauriers.  1983.
Investigations of radiation emissions from video display terminals.  Public
Affairs Directorate, Dept. of Health and Welfare Canada, Report 83-EHD-91.

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